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. 2013 Oct 8:41–127. doi: 10.1007/978-4-431-54445-6_3

Structure–Activity Relationship Study of PD 404182 Derivatives for the Highly Potent Anti-HIV Agents

Tsukasa Mizuhara 2,✉
PMCID: PMC7122882

Abstract

Using facile synthetic approaches to pyrimido[1,2-c][1,3]benzothiazin-6-imines and related tricyclic derivatives, the parallel structural optimizations were investigated for the central 1,3-thiazin-2-imine core, the benzene part, and the cyclic amidine part of PD 404182. Replacement of the 6-6-6 pyrimido[1,2-c][1,3]benzothiazin-6-imine framework with 5-6-6 or 6-6-5 derivatives led to a significant loss of anti-HIV activity, and introduction of a hydrophobic group at the 9- or 10-positions improved the potency. The most potent PD 404182 derivative exerts anti-HIV effects at an early stage of viral infection including binding and fusion.

Keywords: Structure–activity relationship, Anti-HIV agents, PD 404182, Pyrimidobenzothiazine

3,4-Dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (PD 404182) (1, Fig. 3.1) is a promising antiviral agent because of its high therapeutic index (CC50/EC50 > 200) and broad spectrum antiviral activities including against hepatitis C virus (HCV), simian immunodeficiency virus (SIV), and vesicular stomatitis virus (VSV), as well as HIV [1, 2]. In this chapter, the author describes the structure–activity relationship (SAR) studies of PD 404182 for the development of highly potent anti-HIV agents using the novel synthetic methods.

Fig. 3.1.

Fig. 3.1

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Structure of PD 404182

PD 404182 consists of three components, namely a 1,3-thiazin-2-imine core, and left-fused benzene and cyclic amidine moieties (Fig. 3.2). In order to obtain detailed insights into the relationships between compound structure and anti-HIV activity, the author planned to investigate substituent effects on each component: (I) derivatives with various heteroatom (N, S, and O) arrangements on the 1,3-thiazin-2-imine core; (II) pyrimido[1,2-c][1,3]thiazin-6-imine derivatives fused with a substituted benzene ring or a five- or six-membered aromatic heterocycle; and (III) benzo[e][1,3]thiazin-2-imine derivatives fused with a cyclic amidine ring with or without accessory alkyl or aryl groups.

Fig. 3.2.

Fig. 3.2

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Strategy for the SAR study of PD 404182

The investigation began with the synthesis of tricyclic heterocycles with different combinations of heteroatoms on the 1,3-thiazin-2-imine core. As described in 10.1007/978-4-431-54445-6_2, the author developed synthetic methods for pyrimido[1,2-c][1,3]benzoxazine, pyrimido[1,2-c] quinazoline, and pyrimido[1,2-c][1,3]benzothiazine derivatives using Cu(II)-mediated C–H functionalization. This facilitates the introduction of oxygen, nitrogen, and sulfur functional groups at the ortho-position of 2-phenyl-1,4,5,6-tetrahydropyrimidine (2).

One-pot reaction for Cu(OAc)2-mediated C–H functionalization of 2 and subsequent treatment with triphosgene provided a 1,3-oxazin-2-one derivative 4 (Scheme 3.1). The same one-pot procedure using thiophosgene produced a trace amount of the desired thiocarbonyl derivative 5. Treatment of the purified compound 3 with thiophosgene provided the desired 1,3-oxazin-2-thione 5 in high yield. 1,3-Oxazin-2-imine 6 was obtained by the reaction of 3 with BrCN.

Scheme 3.1.

Scheme 3.1

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Syntheses of various tricyclic heterocycles. Reagents and conditions (a) Cu(OAc)2, H2O, O2, DMF, 130 °C, 69 %; (b) triphosgene, TMEDA, CH2Cl2, 0 °C to rt, 70 % [2 steps (a, b)]; (c) thiophosgene, Et3N, CH2Cl2, 0 °C to rt, >99 %; (d) BrCN, CH2Cl2, rt, 34 %; (e) Cu(OAc)2, BocNH2, O2, DMF, 130 °C, 53 %; (f) Lawesson’s reagent, xylene, reflux, 19 %; (g) Cu(OAc)2, CS2, O2, 1,4-dioxane, 130 °C, 11 %; (h) NaOH, MeOH, H2O, reflux; (i) BrCN, EtOH, reflux, 61 % [2 steps (h, i)]; (j) triphosgene, Et3N, CH2Cl2, 0 °C to rt, 65 % [2 steps (h, j)]

The Cu-mediated C–N bond formation of compound 2 with tert-butylcarbamate followed by spontaneous intramolecular cyclization afforded a pyrimido[1,2-c]quinazolin-6-one scaffold 7 (Scheme 3.1). Subsequent treatment with Lawesson’s reagent led to formation of the thiocarbonyl derivative 8. Since no hydrolysis of the carbonyl or thiocarbonyl group of compound 7 or 8 for construction of the 2-aminoquinazoline structure in 9 occurred, an alternative approach starting from 2-aminobenzyl alcohol 12 was used for the synthesis the 2-aminoquinazoline derivative 9 (Scheme 3.2). After protection and PCC oxidation of 12, oxidative amidination [3] provided 2-(p-tosylamino)phenyltetrahydropyrimidine (14). Deprotection followed by BrCN-mediated cyclization of 14 provided the expected 2-aminoquinazoline derivative 9.

Scheme 3.2.

Scheme 3.2

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Synthesis of 2-aminoquinazoline derivative 9. Reagents and conditions (a) p-TsCl, pyridine, CHCl3, rt; (b) PCC, silica gel, CH2Cl2, rt, 80 % [2 steps (a, b)]; (c) 1,3-propanediamine, I2, K2CO3, t-BuOH, 70 °C, 98 %; (d) conc. H2SO4, 100 °C, then NaOH, H2O; (e) BrCN, EtOH, reflux, 66 % [2 steps (d, e)]

To synthesize pyrimido[1,2-c][1,3]benzothiazine derivatives 1 and 11 (Scheme 3.1), compound 2 was exposed to CS2 in the presence of Cu(OAc)2 to directly afford a pyrimido[1,2-c][1,3]benzo-thiazine-6-thione scaffold 10. Hydrolysis of the thiocarbonyl group in 10 followed by treatment with BrCN or triphosgene provided 6-imino or 6-oxo derivatives (1 or 11), respectively.

Pyrimido[1,2-c][1,3]thiazin-6-imine derivatives 25–27 with a series of fused benzene and heterocycles were prepared by consecutive heterocumulene addition and SNAr reactions (Scheme 3.3). These reactions provide easy access to the construction of the 1,3-thiazin-2-imine derivatives more efficiently (10.1007/978-4-431-54445-6_2) than the diversity-oriented C–H functionalization approach (10.1007/978-4-431-54445-6_2). The oxidative amidination of aromatic aldehydes 15–17 with an accessory functional group afforded the corresponding 2-phenyltetrahydropyrimidine derivatives 18–20. The pyrimido[1,2-c][1,3]thiazine-6-thione scaffold 21 was obtained by additions of 18f,g,i or 20s,t,u to CS2 followed by SNAr-type C–S bond formation. The desired 6-imino derivatives 25f,g,i and 27s,t,u were obtained via hydrolysis of the thiocarbonyl group of 21 followed by BrCN treatment. Alternatively, reactions of other 2-phenyltetrahydropyrimidines 18–20 with tert-butyl isothiocyanate afforded N-(t-Bu)-protected thiazinimine derivatives 22–24, which were treated with TFA to provide the expected products 25–27.

Scheme 3.3.

Scheme 3.3

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Synthesis of pyrimido[1,2-c][1,3]thiazin-6-imine derivatives fused with substituted benzene and heterocycles (25–27). Reagents and conditions (a) 1,3-propanediamine, I2, K2CO3, t-BuOH, 70 °C, 58–91 %; (b) NaH, CS2, DMF, 80 °C, 67 to >99 %; (c) NaH or t-BuOK, t-BuNCS, DMF or DMAc, rt−80 °C, 28–95 %; (d) (i) NaOH, MeOH, H2O, reflux, (ii) BrCN, EtOH, reflux, 32–68 %; (e) TFA, MS4Å, CHCl3, reflux, 63–92 %

The intermediates 22e, 22k, and 23k were subjected to further manipulations to obtain the functionalized derivatives (Scheme 3.4). The nitro group of 22e was reduced by hydrogenation to form the 9-amino derivative 28. Alkylation of 28 afforded the 9-(N-methylamino) derivative 22b (eq 1). The 9-acetamide derivative 22c was obtained by treatment of 28 with acetic anhydride (eq 2). Sandmeyer reaction of 28 gave the 9-azide derivative 22p (eq 3). Me2N- and MeO-substituted derivatives (22a, 23a, and 23f) were obtained by Me2NH-mediated N-arylation [4, 5] of the 9-bromo 22k and 10-bromo derivatives 23k, and NaOMe-mediated Ullmann coupling [6] of 23k, respectively (eq 4 and 7). The 9-acetyl derivative 22d was obtained by Heck reaction [7] of 22k with 2-hydroxyethyl vinyl ether (eq 5). Other derivatives with a variety of functional groups (22, 23, 29, and 30) were synthesized by Suzuki–Miyaura coupling reactions [8, 9] of 22k and 23k with boronic acids or their pinacol esters (eq 6 and 7). Final deprotection of the tert-butyl group in 22, 23, 29, and 30 afforded the 9- or 10-substituted pyrimido[1,2-c][1,3]benzothiazine derivatives 25, 26, 31, and 32, respectively.

Scheme 3.4.

Scheme 3.4

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Synthesis of 9- or 10-substituted pyrimido[1,2-c][1,3]benzothiazin-6-imine derivatives. Reagents and conditions (a) H2, 10 % Pd/C, EtOH, rt, 88 %; (b) NaOMe, (CH2O)n, MeOH, reflux, then NaBH4, 91 %; (c) TFA, MS4Å, CHCl3, reflux, 37–95 %; (d) Ac2O, DMAP, Et3N, CH2Cl2, rt, >99 %; (e) NaNO2, AcOH, H2O, 0 °C, then NaN3, 70 %; (f) Pd(OAc)2, t-Bu3P, NHMe2, THF, KOt-Bu, toluene, reflux, >99 %; (g) 2-hydroxyethylvinylether, Pd(OAc)2, 1,3-bis(diphenylphosphino)propane, K2CO3, H2O, 90 °C, 13 % [2 steps (g, c)]; (h) R-B(OH)2 or R-Bpin, Pd(PPh3)4, PdCl2(dppf) · CH2Cl2, K2CO3, toluene or 1,4-dioxane, EtOH, H2O, reflux, 62–96 %; (i) n-BuB(OH)2, Pd2(dba)3, P(t-Bu)3, CsCO3, 1,4-dioxane, reflux, 6 % (for 22h); (j) Pd(Pt-Bu3)2, NHMe2, THF, KOt-Bu, toluene, 170 °C, 67 % (for 23a); (k) CuBr, NaOMe, MeOH, DMF, reflux, 40 % (for 23f)

Benzo[e][1,3]thiazine derivatives with various ring-sized and/or modified cyclic amidine moieties 36 were synthesized using standard synthetic methods (Scheme 3.5). Oxidative addition using a number of diamines 33 proceeded efficiently to form five- or six-membered rings (34a–d). The same reaction for the seven-membered amidine (34e) was incomplete, but purification of the Boc-protected amidine 37 followed by subsequent deprotection of the Boc group gave the pure seven-membered amidine 34e. The resulting amidines were converted to cyclic-amidine-fused benzo[e][1,3]thiazin-2-imines 35 via tert-butyl isothiocyanate addition and an SNAr reaction. TFA-mediated deprotection gave the expected derivatives 36.

Scheme 3.5.

Scheme 3.5

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Synthesis of benzo[e][1,3]thiazine derivatives with fused cyclic amidines. Reagents and conditions (a) 2-fluorobenzaldehyde or 2-bromobenzaldehyde, I2, K2CO3, t-BuOH, 70 °C, 68–79 %; (b) NaH, t-BuNCS, DMF, rt −80 °C, 18–50 %; (c) TFA, MS4Å, CHCl3, reflux, 16–86 %; (d) Boc2O, Et3N, DMAP, CH2Cl2, rt, 37 % [2 steps (a, d)]; (e) TFA, CHCl3, reflux, 80 %

The synthesis of the spiropyrimidine-fused derivatives started with the dialkylation of malononitrile with dihaloalkanes (38, 39, or 41, Scheme 3.6). BH3-mediated reduction of the alkylated malononitriles (42–44) followed by oxidative amidination with 4-bromo-2-fluorobenzaldehyde gave the 2-phenyl-1,4,5,6-tetrahydropyrimidine derivatives (45–47). Subsequent exposure of compounds 45–47 to tert-butylisothiocyanate provided the tetracyclic compounds 48, 50, and 52a. Deprotection of the tert-butyl groups in compounds 48, 50, and 52a afforded the desired spiropyrimidine-fused benzothiazinimine derivatives (49, 51, and 53a).

Scheme 3.6.

Scheme 3.6

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Synthesis of spiropyrimidine-fused benzothiazinimine derivatives. Reagents and conditions (a) (i) 4-methoxybenzoyl chloride, Et3N, CH2Cl2, rt; (ii) LiAlH4, Et2O, rt, 75 % (2 steps); (b) malononitrile, DBU, DMF, 50 °C, 8–60 % (for 42 and 43); (c) malononitrile, K2CO3, DMF, 65 °C, 85 % (for 44); (d) BH3, THF, 0 °C to rt; (e) 4-bromo-2-fluorobenzaldehyde, I2, K2CO3, t-BuOH, 70 °C, 11–62 % [2 steps (d,e)]; (f) NaH, t-BuNCS DMF, rt −80 °C, 78–94 %; (g) TFA, MS4Å, CHCl3, reflux, 65-94 %. (h) ClCO2Me or AcCl, CH2Cl2, 0 °C, 81–96 % (for 52b or 52c); (i) (i) 1-chloroethyl chloroformate, Et3N, CH2Cl2, 0 °C, then MeOH, reflux, (ii) MsCl or TMSNCO, (Et3N), CH2Cl2, rt, 29–82 % (2 steps, for 52d or 52e)

The substitution of the p-methoxybenzyl (PMB) group in compound 53a was also attempted (Scheme 3.6). The treatment of compound 52a with methyl chloroformate or acetyl chloride directly provided derivatives 52b and 52c, respectively. A two-step procedure, including the removal of the PMB group by treatment with 1-chloroethyl chloroformate followed by modification with mesyl chloride (MsCl) or trimethylsilyl isocyanate (TMSNCO) was used for the synthesis of the derivatives 52d and 52e, respectively, because the reaction of compound 52a with MsCl and TMSNCO failed. Deprotection of the tert-butyl group in 52b–e afforded the respective N-substituted derivatives 53b–e.

SARs of the central heterocyclic core in pyrimido[1,2-c][1,3]benzothiazines were carried out. Initially, the structural requirements of the 1,3-thiazin-2-imine core substructure in 1 (PD 404182) for anti-HIV activity were investigated (Table 3.1). The antiviral activities against the HIV-1IIIB strain were evaluated using the MAGI assay [10]. Substitution of the imino group in 1 with a carbonyl group (11) resulted in a significant decrease in anti-HIV activity (EC50 = 8.94 μM). Pyrimido[1,2-c][1,3]benzoxazines (4–6), pyrimido[1,2-c]quinazolines (7–9), and pyrimido[1,2-c] [1,3]benzothiazine-6-thione (10), in which the 1-sulfur and/or 2-imino groups in 1 were modified, showed no activity. These results suggested that both the 1-sulfur atom and the 2-imino group are indispensable functional groups for the inhibitory activity against HIV infection, and may be involved in potential interactions with the target molecules.

Table 3.1.

SARs for 1,3-thiazin-2-imine core Inline graphic

Compound X Y EC50 (μM)a
1 S NH 0.44 ± 0.08
4 O O >10
5 O S >10
6 O NH >10
7 NH O >10
8 NH S >10
9 NH NH >10
10 S S >10
11 S O 8.94 ± 1.07
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aEC50 values represent the concentration of compound required to inhibit the HIV-1 infection by 50 % and were obtained from three independent experiments

A series of derivatives with modification of the benzene substructure in the pyrimido[1,2-c][1,3]benzothiazine were evaluated for anti-HIV activity (Table 3.2). The addition of positively charged N,N-dimethylamino (25a) and N-methylamino groups (25b) at the 9-position significantly decreased the anti-HIV activity. The 9-acetamide group (25c), which has hydrogen bond donor/acceptor abilities, also attenuated the bioactivity. The acetyl (25d) and nitro (25e) groups, with hydrogen acceptor properties, induced slight decreases in the anti-HIV activity. In contrast, derivatives with less-polarized substituents (25f–o and 25q) at this position generally reproduced the potent anti-HIV activity of 1. In terms of the electron-donating or -withdrawing properties of the substituent groups on the benzene substructure, good correlations were not observed. For example, the electron-donating methoxy (25f), methyl (25g), and n-butyl groups (25h), and the electron-withdrawing fluoro (25i) and trifluoromethyl groups (25j) exhibited similar anti-HIV activities (EC50 = 0.44–0.57 μM), indicating that the antiviral activity is independent of the electronic state of the 1,3-benzothiazin-2-imine core in forming potential π-stacking interaction(s) with the target molecules. Among the hydrophobic substituents at this position, bromo (25k), phenyl (25l), vinyl (25m), styryl (25n), and pentenyl groups (25o) induced inhibitory activity two or three times greater than that of 1 (EC50 = 0.18–0.25 μM). Modification with photoreactive azido (25p) and benzoylphenyl groups (25q) maintained the inhibitory activity; these could be used as probe molecules to identify the target molecule(s) of 1 [11–13].

Table 3.2.

SARs for benzene part

Compound EC50 (μM)a Compound EC50 (μM)a
graphic file with name 315325_1_En_3_Figb_HTML.gif 27r graphic file with name 315325_1_En_3_Figc_HTML.gif 0.56 ± 0.13
1 R = H 0.44 ± 0.08 27s graphic file with name 315325_1_En_3_Figd_HTML.gif 2.55 ± 0.26
25a R = NMe2 4.74 ± 1.07
25b R = NHMe >10
25c R = NHAc >10
25d R = COMe 1.44 ± 0.33
25e R = NO2 1.13 ± 0.18
25f R = OMe 0.57 ± 0.09 27k graphic file with name 315325_1_En_3_Fige_HTML.gif >10
25g R = Me 0.49 ± 0.10
25h R = n-butyl 0.44 ± 0.09
25i R = F 0.50 ± 0.07
25j R = CF3 0.53 ± 0.12
25k R = Br 0.25 ± 0.09
25l R = Ph 0.24 ± 0.04
25m R = vinyl 0.18 ± 0.05 27t graphic file with name 315325_1_En_3_Figf_HTML.gif >10
25n R = styryl 0.25 ± 0.05
25o R = pentenyl 0.24 ± 0.11
25p R = N3 0.43 ± 0.06
25q R = C6H4(4-Bz) 0.53 ± 0.12
graphic file with name 315325_1_En_3_Figg_HTML.gif 27i graphic file with name 315325_1_En_3_Figh_HTML.gif 1.68 ± 0.19
26a R = NMe2 2.12 ± 0.26 27u graphic file with name 315325_1_En_3_Figi_HTML.gif >10
26e R = NO2 3.00 ± 0.59
26f R = OMe 0.53 ± 0.04
26g R = Me 0.38 ± 0.04
26k R = Br 0.24 ± 0.05
26l R = Ph 0.24 ± 0.05
26m R = vinyl 0.40 ± 0.09
26q R = C6H4(4-Bz) 0.67 ± 0.16
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aEC50 values represent the concentration of compound required to inhibit the HIV-1 infection by 50 % and were obtained from three independent experiments

Similar SARs were observed for modification at the 10-position of pyrimido[1,2-c] [1,3]benzothiazine. Addition of positively charged N,N-dimethylamino (26a) and polarized nitro groups (26e) reduced the anti-HIV activity (EC50 = 2.12 and 3.00 μM, respectively). Hydrophobic groups including methoxy (26f), methyl (26g), bromo (26k), phenyl (26l), vinyl (26m), and 4-benzoylphenyl (26q) had favorable effects on the bioactivity (EC50 = 0.24–0.67 μM), suggesting potential hydrophobic interactions of these additional functional groups with the target molecule(s).

Further miscellaneous modifications of benzothiazine substructure were also investigated (Table 3.2). The naphtho[2,3-e][1,3]thiazine derivative 27r, with a 9,10-fused benzene, exhibited anti-HIV activity equipotent to that of the parent 1 (EC50 = 0.56 μM). A 6-fold decrease in the anti-HIV activity of the pyridine-fused pyrido[3,2-e][1,3]thiazine derivative (27s) was observed (EC50 = 2.55 μM). In addition, introduction of 8-bromo (27k) and 8,9-fused benzene (27t, naphtho[2,1-e][1,3]thiazine) substituents on benzothiazine resulted in a loss of activity, suggesting that modification at the 8-position was inappropriate for favorable interactions with the target molecule(s). The 11-fluoro derivative 27i and thiophene-fused 27u, the latter of which has 5-6-6 framework (thieno[2,3-e][1,3]thiazine), exhibited four times lower and no inhibitory potencies, respectively.

On the basis of the above SAR data for the benzene substructure in 1 (PD 404182), the author expected that introduction of a hydrophobic group at the pyrimido[1,2-c][1,3]benzothiazine 9-position would be the most promising. The next optimization to obtain more potent derivatives was therefore focused on modification of the benzothiazine scaffold at position 9 with an additional aryl group (Tables 3.3, 3.4).

Table 3.3.

SARs for biphenyl-type derivatives Inline graphic

Compound Ar EC50 (μM)a Compound Ar EC50 (μM)a
graphic file with name 315325_1_En_3_Figk_HTML.gif graphic file with name 315325_1_En_3_Figl_HTML.gif
25l R = H 0.24 ± 0.04 31s R = OMe 0.41 ± 0.10
31a R = CO2Me 0.81 ± 0.29 31t R = Ph 0.32 ± 0.12
31b R = CN 0.44 ± 0.10 31u graphic file with name 315325_1_En_3_Figm_HTML.gif 0.27 ± 0.04
31c R = NO2 0.46 ± 0.06
31d R = CF3 0.55 ± 0.16
31e R = CONH2 8.71 ± 0.82
31f R = OMe 0.24 ± 0.04 31v graphic file with name 315325_1_En_3_Fign_HTML.gif 0.25 ± 0.03
31g R = SMe 0.20 ± 0.06
31h R = OCF3 0.38 ± 0.06
graphic file with name 315325_1_En_3_Figo_HTML.gif 31w graphic file with name 315325_1_En_3_Figp_HTML.gif 0.32 ± 0.04
31i R = CO2Me 0.39 ± 0.09
31j R = CN 1.17 ± 0.27
31k R = NO2 1.26 ± 0.13
31l R = CH(OH)CH3 1.19 ± 0.19
31m R = NHAc >10 graphic file with name 315325_1_En_3_Figq_HTML.gif 0.48 ± 0.06
31n R = NHMs >10
31o R = OH 2.62 ± 0.26
31p R = OMe 0.15 ± 0.05
31q R = Oi-Pr 0.32 ± 0.10
31r R = Ph 1.35 ± 0.26
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aEC50 values represent the concentration of compound required to inhibit the HIV-1 infection by 50 % and were obtained from three independent experiments

Table 3.4.

SARs for biaryl-type derivatives Inline graphic

Compound Ar EC50 (μM)a Compound Ar EC50 (μM)a
32a graphic file with name 315325_1_En_3_Figs_HTML.gif 0.20 ± 0.06 32h graphic file with name 315325_1_En_3_Figt_HTML.gif 0.45 ± 0.07
32b graphic file with name 315325_1_En_3_Figu_HTML.gif 0.39 ± 0.12 32i graphic file with name 315325_1_En_3_Figv_HTML.gif 0.54 ± 0.04
32c graphic file with name 315325_1_En_3_Figw_HTML.gif 0.15 ± 0.03 32j graphic file with name 315325_1_En_3_Figx_HTML.gif 0.26 ± 0.02
32d graphic file with name 315325_1_En_3_Figy_HTML.gif 0.26 ± 0.07 32 k graphic file with name 315325_1_En_3_Figz_HTML.gif 0.20 ± 0.03
32e graphic file with name 315325_1_En_3_Figaa_HTML.gif 0.25 ± 0.04 32l graphic file with name 315325_1_En_3_Figab_HTML.gif 0.22 ± 0.07
32f graphic file with name 315325_1_En_3_Figac_HTML.gif >1.00b 32 m graphic file with name 315325_1_En_3_Figad_HTML.gif 0.26 ± 0.06
32n graphic file with name 315325_1_En_3_Figae_HTML.gif 0.42 ± 0.08
32g graphic file with name 315325_1_En_3_Figaf_HTML.gif >1.00b 32o graphic file with name 315325_1_En_3_Figag_HTML.gif 5.12 ± 1.28
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aEC50 values represent the concentration of compound required to inhibit the HIV-1 infection by 50 % and were obtained from three independent experiments

bCytotoxicity was observed at 10 μM

The author initially examined substituent effects at the para-position on the 9-phenyl group of compound 25l. Modification with methoxycarbonyl (31a), cyano (31b), nitro (31c), and trifluoromethyl (31d) groups slightly reduced the anti-HIV activity (EC50 = 0.44–0.81 μM), whereas a significant decrease in the anti-HIV activity was observed for a carbamoyl group (31e), with hydrogen bond donor/acceptor properties (EC50 = 8.71 μM). The hydrophobic methoxy (31f, EC50 = 0.24 μM), methylthio (31g, EC50 = 0.20 μM), and trifluoromethoxy (31h, EC50 = 0.38 μM) groups had favorable effects on the anti-HIV activity.

Similar effects as a result of modification at the meta-position of the 9-phenyl group were observed. Addition of electron-withdrawing methoxycarbonyl (31i), cyano (31j), and nitro (31k) (EC50 = 0.39–1.26 μM) groups resulted in slight decreases in anti-HIV activity. Hydrophilic (1-hydroxy)ethyl (31l, EC50 = 1.19 μM), acetylamino (31m), mesylamino (31n), and hydroxyl (31o, EC50 = 2.62 μM) groups induced reduction or loss of anti-HIV activity. In contrast, a methoxy group (31p) improved the inhibitory activity (EC50 = 0.15 μM). The more hydrophobic isopropoxy group (31q) maintained the anti-HIV activity of 25l (EC50 = 0.32 μM), whereas a phenyl group (31r) decreased the inhibitory activity (EC50 = 1.35 μM).

Similar anti-HIV activities of the ortho-methoxy (31s) and ortho-phenyl group (31t) to that of 25l were exhibited (EC50 = 0.41 and 0.32 μM, respectively), suggesting that the twisted conformations of these 9-phenyl PD 404182 derivatives might not prevent the interaction with the target molecule(s).

In order to develop more potent anti-HIV agents, the author subsequently attempted bis and tris modifications of the 9-phenyl group in 25l. Modification with 9-(3,4-dimethoxy)phenyl (31u, EC50 = 0.27 μM) or 9-(3,4,5-trimethoxy)phenyl (31v, EC50 = 0.25 μM) groups of the pyrimido[1,2-c][1,3]benzothiazine scaffold did not alter the bioactivity. Cl-modified derivatives 31w and 31x exhibited similar potencies (EC50 = 0.32 and 0.48 μM, respectively).

Since the 9-(2-naphthyl)-modified analog (32a) exhibited slightly more potent anti-HIV activity (EC50 = 0.20 μM) compared with that of the 1-naphthyl congener (32b, EC50 = 0.39 μM, Table 3.4), the author further investigated modifications with a variety of 3,4-fused phenyl groups. Compound 32c with a 1,3-dioxolane-fused phenyl group displayed activity twice as potent as that of compound 25l (EC50 = 0.15 μM), whereas the 1,4-dioxane-fused derivative 32d and quinolin-6-yl derivative 32e exhibited less favorable effects (EC50 = 0.26 and 0.25 μM, respectively). Introduction of an indolyl group (32f and 32g) resulted in no anti-HIV activity and unexpected cytotoxicity.

Substitutions of the 9-phenyl group by various heterocyclic substructures were also investigated. Six-membered heterocycles such as pyridine (32h and 32i) slightly reduced the anti-HIV activity (EC50 = 0.45 and 0.54 μM, respectively). The five-membered furan (32j), benzofuran (32k), thiophene (32l), benzothiophene (32m), and pyrazole (32n) derivatives maintained the original activity of 25l (EC50 = 0.20–0.42 μM). Notably, reduced anti-HIV activity was observed for the basic imidazole derivative (32o, EC50 = 5.12 μM).

A SAR study of the top-right cyclic amidine substructure was carried out. The five-membered dihydroimidazole derivative 36a had no anti-HIV activity (Table 3.5), suggesting that the five-membered ring may impair the critical interactions with the target molecule(s) via its small-sized ring strain or indirect effects on the thiazinimine core with a possibly altered conformation. Similarly, compound 36b with the phenyl-fused dihydropyrimidine substructure showed lower inhibitory activity (EC50 = 3.78 μM). Appending one or two methyl groups on the six-membered pyrimidine (36c and 36d) induced 1.5- to 2-fold higher inhibitory potencies (EC50 = 0.35 and 0.24 μM, respectively) compared with that of the parent compound 1. In addition, compound 36e with a seven-membered tetrahydro-1,3-diazepine substructure exhibited similar anti-HIV activity to that of 1 (EC50 = 0.31 μM).

Table 3.5.

SARs for cyclic amidine core Inline graphic

Compound EC50 (μM)a Compound EC50 (μM)a
1 graphic file with name 315325_1_En_3_Figai_HTML.gif 0.44 ± 0.08 36c graphic file with name 315325_1_En_3_Figaj_HTML.gif 0.35 ± 0.09
36a graphic file with name 315325_1_En_3_Figak_HTML.gif >10 36d graphic file with name 315325_1_En_3_Figal_HTML.gif 0.24 ± 0.04
36b graphic file with name 315325_1_En_3_Figam_HTML.gif 3.78 ± 1.39 36e graphic file with name 315325_1_En_3_Figan_HTML.gif 0.31 ± 0.06
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aEC50 values represent the concentration of compound required to inhibit the HIV-1 infection by 50 % and were obtained from three independent experiments

Above optimization studies indicated that the introduction of a hydrophobic group on the cyclic amidine substructures effectively improved the antiviral activity (compound 36c–e) by generating a potentially favorable interaction(s) with the target molecule(s). Therefore, anti-HIV activities of several spiropyrimidine fused derivatives were evaluated (Table 3.6).1 Cyclohexane (49) and N-methoxycarbonylpiperidine (53b) derivatives exhibited the similar levels of anti-HIV activity (EC50 = 0.25 and 0.44 μM, respectively) to that of the dimethyl derivative 36d (EC50 = 0.24 μM). In contrast, the tetrahydropyran (51) and N-(p-methoxybenzyl)piperidine (53a) derivatives exerted inhibitory activities that were 5–7-fold lower (EC50 = 1.73 and 1.45 μM, respectively) than that of the parent dimethyl derivative 36d. The N-acetyl- (53c), N-methanesulfonyl- (53d), and N-carbamoyl- (53e) piperidine derivatives also provided reduced levels of antiviral activity (EC50 = 1.81 to >10 μM). With this in mind, the N-alkoxycarbonyl piperidine group was identified as a linkage for the introduction of additional functional group(s) to PD 404182 with potent anti-HIV activity (53b).

Table 3.6.

SARs for spiropyrimidine-fused derivatives Inline graphic

Compound X EC50 (μM)a
49 CH2 0.25 ± 0.01
51 O 1.73 ± 0.35
53a N-PMB 1.45 ± 0.05
53b N-CO2Me 0.44 ± 0.02
53c N–Ac 2.74 ± 0.15
53d N-Ms 1.81 ± 0.43
53e N-CONH2 >10
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aEC50 values represent the concentration of compound required to inhibit the HIV-1 infection by 50 % and were obtained from three independent experiments

To investigate the mechanism of action of PD 404182 derivatives, a time of drug addition study was carried out (Fig. 3.3). In this experiment, the anti-HIV activity profiles of 1 and its derivatives 32c were compared with those of well-known anti-HIV agents such as an adsorption inhibitor (DS 5000) [14], fusion inhibitor (enfuvirtide) [15–17], NRTI (AZT) [18], NNRTI (nevirapine) [19], and integrase inhibitor (raltegravir) [20]. After inoculation of HeLa-CD4/CCR5-LTR/β-gal cells with HIV-1IIIB, each anti-HIV-1 drug was added at a 90 % inhibitory effect concentration at the indicated time points. The inhibitory effects on the infection were determined by counting the blue cells 48 h later. This investigation revealed that compound 1 (PD 404182) had an inhibitory profile in the early stage of viral infection similar to those of DS 5000 and enfuvirtide (Fig. 3.3). Identical profiles were observed for 1 and the most potent derivative 32c, indicating that the bioactivity profile is independent of the appended functional group(s).

Fig. 3.3.

Fig. 3.3

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Time of drug addition profiles in the presence of Anti-HIV agents for infection of a HIV-1IIIB strain of HeLa-CD4/CCR5-LTR/β-gal cells

To gain additional insights into the mechanism of action of PD 404182 derivatives, the antiviral activities against other HIV subtypes were evaluated (Table 3.7). Compound 1 was effective against not only HIV-1IIIB but also other two HIV-1 strains (HIV-1NL4-3 and HIV-1BaL) with similar potency. Both HIV-1IIIB and HIV-1NL4-3 strains utilize CXCR4 as a coreceptor for entry, while HIV-1BaL strain does CCR5, indicating that chemokine receptors CXCR4 and CCR5 are not the molecular targets of PD 404182 derivatives. The similar level of antiviral activity of 1 against HIV-2 (HIV-2EHO and HIV-2ROD), which is mainly distributed in West Africa, was observed. Highly potent inhibitory activities of derivatives 32c and 36d 2 against these HIV strains were observed, as in the case of the SAR study of the HIV-1IIIB strain discussed above. It has been well-known that NNRTIs are not effective against HIV-2, highlighting that PD 404182 derivatives do not act as NNRTIs. Although PD 404182 derivatives and enfuvirtide showed similar anti-HIV-1 profile in the time of drug addition assay, HIV-2EHO and HIV-2ROD infection were affected by PD 404182 derivatives, in contrast with the less effective enfuvirtide [21], suggesting that PD 404182 derivatives may not be directed at the HIV gp41 envelope protein. Recent reports have suggested that the antiviral activities of compound 1 against HIV, HCV, and pseudotype lentiviruses were derived from disruption of the structural integrities of virions [2]. Although the mechanism of action of PD 404182 derivatives is not fully understood at this stage, the unidentified biomolecule(s) in viruses or host cells could be promising molecular targets for this new class of anti-HIV agents.

Table 3.7.

Anti-HIV activity of compounds 1, 32c, and 36d against other HIV strains

Strains EC50 (μM)a
1 32c 36d
HIV-1NL4-3 0.38 ± 0.06 0.25 ± 0.03 0.23 ± 0.09
HIV-1BaL 0.37 ± 0.06 0.16 ± 0.02 0.13 ± 0.05
HIV-2EHO 0.31 ± 0.06 0.17 ± 0.03 0.14 ± 0.02
HIV-2ROD 0.30 ± 0.06 0.11 ± 0.03 0.10 ± 0.04
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aEC50 values represent the concentration of compound required to inhibit the HIV-1 infection by 50 % and were obtained from three independent experiments

In conclusion, the author have designed and synthesized PD 404182 derivatives for a novel series of anti-HIV agents. Comprehensive SAR studies demonstrated that the 6-6-6 fused pyrimido[1,2-c][1,3]benzothiazine scaffold and the heteroatom arrangement in the thiazinimine moiety are indispensable for the inhibitory activity of 1 (PD 404182) against HIV infection. Optimization studies of the benzene and cyclic amidine rings indicate that the introduction of a hydrophobic group on the benzene ring is more effective in improving the antiviral activity, giving potential favorable interaction(s) with the target molecule(s). The most potent compound, 32c, had anti-HIV activity three times higher than that of the parent 1. In addition, PD 404182 derivatives could be promising agents for treatment of HIV-2 infection. The author also revealed, using a time of drug addition experiment, that PD 404182 derivatives prevent the HIV infection process at a fusion or binding process.

Experimental Section

General Methods

All moisture-sensitive reactions were performed using syringe-septum cap techniques under an Ar atmosphere and all glasswares were dried in an oven at 80 °C for 2 h prior to use. Melting points were measured by a hot stage melting point apparatus (uncorrected). For flash chromatography, Wakogel C-300E (Wako) or aluminum oxide 90 standardized (Merck) was employed. For preparative TLC, TLC silica gel 60 F254 (Merck) or TLC aluminum oxide 60 F254 basic (Merck), or NH2 Silica Gel 60 F254 Plate (Wako) were employed. For analytical HPLC, a COSMOSIL 5C18-ARII column (4.6 × 250 mm, Nacalai Tesque, Inc., Kyoto, Japan) was employed with method A [a linear gradient of CH3CN containing 0.1 % (v/v) TFA] or method B [a linear gradient of CH3CN containing 0.1 % (v/v) NH3] at a flow rate of 1 mL/min on a Shimadzu LC-10ADvp (Shimadzu Corp., Ltd., Kyoto, Japan), and eluting products were detected by UV at 254 nm. Preparative HPLC was performed using a COSMOSIL 5C18-ARII column (20 × 250 mm, Nacalai Tesque Inc.) with a linear gradient of MeCN containing 0.1 % (v/v) NH3 at a flow rate of 8 mL/min on Shimadzu LC-6AD (Shimadzu corporation, Ltd). 1H-NMR spectra were recorded using a JEOL AL-400 or a JEOL ECA-500 spectrometer, and chemical shifts are reported in δ (ppm) relative to Me4Si (CDCl3) or DMSO (DMSO-d 6) as internal standards. 13C-NMR spectra were recorded using a JEOL AL-400 or JEOL ECA-500 spectrometer and referenced to the residual solvent signal. 19F–NMR spectra were recorded using a JEOL ECA-500 and referenced to the internal CFCl3 (δ F 0.00 ppm). 1H-NMR spectra are tabulated as follows: chemical shift, multiplicity (b = broad, s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet), coupling constant(s), and number of protons. Exact mass (HRMS) spectra were recorded on a JMS-HX/HX 110A mass spectrometer. Infrared (IR) spectra were obtained on a JASCO FT/IR-4100 FT-IR spectrometer with JASCO ATR PRO410-S. The purity of the compounds was determined by combustion analysis or HPLC analysis as >95 % unless otherwise stated. Synthesis and characterization data of compounds 2, 4, 7, and 10 are shown in 10.1007/978-4-431-54445-6_2. Synthesis and characterization data of compounds 1, 18e-g, 18i, 19e, 20s, 20t, 21f, 21g, 21i, 21s, 21t, 34a and 35a are shown in 10.1007/978-4-431-54445-6_2.

Synthesis of 3,4-Dihydro-2H,6H-pyrimido[1,2-c][1,3]benzoxazine-6-thione (5)

2-(2-Hydroxyphenyl)tetrahydropyrimidine (3). DMF (0.83 mL) and water (4.5 μL, 0.25 mmol) were added to a flask 2-phenyl-1,4,5,6-tetrahydropyrimidine 2 (40.1 mg, 0.25 mmol) and Cu(OAc)2 (45.4 mg, 0.25 mmol) under an O2 atmosphere. After being stirred at 130 °C for 20 min, mixture was concentrated. The residue was purified by flash chromatography over aluminum oxide with CHCl3–MeOH (95:5) to give the title compound 3 as brown solid (30.3 mg, 69 %): IR (neat) cm−1: 3257–3041 (OH), 1613 (C=N); 1H-NMR (500 MHz, DMSO-d 6) δ: 1.84–1.88 (2H, m, CH2), 3.40 (4H, t, J = 5.7 Hz, 2 × CH2), 6.27–6.30 (1H, m, Ar), 6.47 (1H, d, J = 8.6 Hz, Ar), 7.04–7.08 (1H, m, Ar), 7.45 (1H, dd, J = 8.0, 1.7 Hz, Ar), 12.09 (1H, br s); 13C-NMR (125 MHz, CD3OD) δ: 20.0, 39.3 (2C), 111.2, 114.5, 124.4, 126.3, 135.1, 161.0, 172.4; MS (FAB) m/z (%): 177 (MH+, 100).

Compound 5. To a suspension of 3 (33.0 mg, 0.19 mmol) and Et3N (0.068 mL, 0.47 mmol) in CH2Cl2 (10.0 mL) was added dropwise a solution of thiophosgene (0.016 mL, 0.21 mmol) in CH2Cl2 (1.0 mL) at 0 °C. After being stirred at rt for 1 h, the mixture was quenched with sat. NaHCO3. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (3:1) to give the title compound 5 as yellow solid (41.9 mg, >99 %): mp 135–136 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1655 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 2.03–2.08 (2H, m, CH2), 3.68 (2H, t, J = 5.5 Hz, CH2), 4.30 (2H, t, J = 6.1 Hz, CH2), 7.21 (1H, d, J = 8.5 Hz, Ar), 7.25–7.29 (1H, m, Ar), 7.50–7.52 (1H, m, Ar), 8.00 (1H, d, J = 7.8 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.1, 44.5, 49.2, 115.9, 116.9, 125.4, 125.7, 133.0, 139.7, 150.9, 180.8; Anal. calcd for C11H10N2OS: C, 60.53; H, 4.62; N, 12.83. Found: C, 60.23; H, 4.72; N, 12.62.

Synthesis of 3,4-Dihydro-2H,6H-pyrimido[1,2-c][1,3]benzoxazin-6-imine (6)

2-(2-Hydroxyphenyl)tetrahydropyrimidine 3 (5.4 mg, 0.03 mmol) was suspended with CH2Cl2 (0.3 mL) and added the solution of BrCN (3.3 mg, 0.06 mmol) in CH2Cl2 (0.3 mL). After being stirred for 1 h at rt, the additional portion of BrCN (3.3 mg, 0.06 mmol) in CH2Cl2 (0.3 mL) was added. After being stirred for 1 h at rt, the mixture was concentrated. The residue was purified by preparative TLC over NH2 silica gel with n-hexane–EtOAc (1:1) to give the title compound 6 as colorless solid (2.1 mg, 34 %): mp 104–105 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1639 (C=N), 1611 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.98–2.03 (2H, m, CH2), 3.64 (2H, t, J = 5.4 Hz, CH2), 3.93 (2H, t, J = 6.0 Hz, CH2), 5.83 (1H, br s, NH), 6.99 (1H, d, J = 8.0 Hz, Ar), 7.15 (1H, t, J = 8.0 Hz, Ar), 7.42 (1H, td, J = 8.0, 1.7 Hz, Ar), 7.99 (1H, dd, J = 8.0, 1.7 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.6, 43.4, 44.1, 115.2, 116.2, 123.9, 125.5, 132.3, 142.5, 150.4, 150.7; Anal. calcd for C11H11N3O: C, 65.66; H, 5.51; N, 20.88. Found: C, 65.55; H, 5.40; N, 20.70.

Synthesis of 3,4-Dihydro-2H,6H-pyrimido[1,2-c]quinazolin-6(7H)-thione (8)

Xylene (4.0 mL) was added to a flask containing 3,4-dihydro-2H,6H-pyrimido[1,2-c]quinazolin-6(7H)-one 7 (50.3 mg, 0.25 mmol) and Lawesson’s reagent (202.2 mg, 0.50 mmol). After being stirred under reflux for 24 h, xylene (2 mL) and additional amount of Lawesson’s reagent (101.1 mg, 0.25 mmol) were added. After being stirred under reflux for additional 12 h, the mixture was cooled to rt. The residue was dissolved in CHCl3 and washed with sat. NaHCO3 and brine and dried over MgSO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (2:1) to give the title compound 8 as colorless solid (10.4 mg, 19 %): mp 258–259 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1618 (C=N); 1H-NMR (500 MHz, DMSO-d 6) δ: 1.85–1.90 (2H, m, CH2), 3.52 (2H, t, J = 5.4 Hz, CH2), 4.19 (2H, t, J = 6.0 Hz, CH2), 7.12–7.19 (2H, m, Ar), 7.46 (1H, t, J = 7.7 Hz, Ar), 7.92 (1H, d, J = 6.9 Hz, Ar), 12.00 (1H, s, NH); 13C-NMR (100 MHz, DMSO-d 6) δ: 20.6, 44.0, 46.7, 114.8, 117.6, 123.8, 125.1, 132.1, 135.9, 142.1, 174.0; HRMS (FAB): m/z calcd for C11H12N3S [M + H]+ 218.0752; found: 218.0757.

Synthesis of 3,4-Dihydro-2H,6H-pyrimido[1,2-c]quinazolin-6-amine (9)

2-[ N -( p -Toluenesulfonyl)amino]benzaldehyde (13). To a solution of 2-aminobenzylalcohol 12 (2.0 g, 16.2 mmol) and pyridine (1.6 mL, 19.4 mmol) in CHCl3 (60 mL) was added a solution of p-TsCl (3.4 g, 18.0 mmol) in CHCl3 (17 mL), and the mixture was stirred at rt for 3 h. After concentration, EtOAc and sat. NH4Cl were added to the residue. The organic phase was separated and dried over MgSO4. After concentration, the resulting solid was added to a suspension of PCC (5.2 g, 24.3 mmol) and silica gel (10.6 g) in CHCl3 (70 mL). After being stirred at rt for 2 h, the mixture was filtered and concentrated. The residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (9:1) to give the title compound 13 as colorless solid (3.6 g, 80 %): mp 134–136 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1672 (C=O), 1492 (NSO2), 1157 (NSO2); 1H-NMR (400 MHz, CDCl3) δ: 2.36 (3H, s, CH3), 7.16 (1H, t, J = 7.6 Hz, Ar), 7.24 (2H, d, J = 8.5 Hz, Ar), 7.49–7.53 (1H, m, Ar), 7.59 (1H, dd, J = 7.6, 1.5 Hz, Ar), 7.69 (1H, d, J = 8.3 Hz, Ar), 7.77 (2H, d, J = 8.5 Hz, Ar), 9.83 (1H, s, CHO), 10.78 (1H, br s, NH); 13C-NMR (100 MHz, CDCl3) δ: 21.5, 117.8, 121.9, 122.9, 127.3 (2C), 129.7 (2C), 135.8, 136.1, 136.5, 140.0, 144.1, 194.9; Anal. calcd for C14H13NO3S: C, 61.07; H, 4.76; N, 5.09. Found: C, 60.97; H, 4.46; N, 5.05.

2-[2- N -( p -Toluenesulfonylamino)phenyl]-1,4,5,6-tetrahydropyrimidine (14). To a solution of 13 (2.75 g, 10 mmol) in t-BuOH (94 mL) was added propylenediamine (969 mg, 11 mmol). The mixture was stirred at 70 °C for 30 min, and then K2CO3 (4.15 g, 30 mmol) and I2 (3.17 g, 12.5 mmol) were added. After being stirred at same temperature for 3 h, the mixture was quenched with sat. Na2SO3 until the iodine color disappeared. The organic layer was separated and concentrated. The resulting solid was dissolved in H2O. The whole was extracted with CHCl3, and dried over MgSO4. After concentration, the resulting solid was recrystallized from CHCl3–Et2O–n-hexane to give the title compound 14 as pale yellow crystals (3.23 g, 98 %): mp 211–213 °C; IR (neat) cm−1: 1630 (C=N); 1478 (NSO2), 1124 (NSO2); 1H-NMR (400 MHz, CDCl3) δ: 1.77–1.82 (2H, m, CH2), 2.34 (3H, s, CH3), 3.36 (4H, t, J = 5.7 Hz, 2 × CH2), 6.53–6.57 (1H, m, Ar), 7.04–7.08 (1H, m, Ar), 7.16–7.22 (3H, m, Ar), 7.58 (1H, dd, J = 8.2, 1.3 Hz, Ar), 7.76 (2H, d, J = 8.3 Hz, Ar), 10.75 (1H, br s, NH); 13C-NMR (100 MHz, CDCl3) δ: 18.4, 21.3, 38.8 (2C), 112.4, 117.7, 121.2, 126.3 (2C), 126.5, 129.2 (2C), 133.0, 140.9, 142.0, 150.3, 158.9; HRMS (FAB): m/z calcd for C17H20N3O2S [M + H]+ 330.1276; found: 330.1273.

Compound 9. To a flask containing 14 (164.7 mg, 0.5 mmol) was added conc. H2SO4 (5.0 mL). After being stirred at 100 °C for 30 min, the mixture was cooled to 0 °C, and then pH was adjusted to 12–14 with 2 N NaOH. The whole was extracted with CHCl3, and dried over MgSO4. After concentration, the residue was dissolved in anhydrous EtOH (2 mL). Then, BrCN (105.9 mg, 1.0 mmol) was added to the mixture under an Ar atmosphere. After being stirred under reflux for 2 h, the reaction was quenched with 2N NaOH. The whole was extracted with CHCl3, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with EtOAc–MeOH (95:5) to give the title compound 9 as colorless solid (66.0 mg, 66 %): mp 259–260 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1603 (C=N); 1H-NMR (400 MHz, DMSO-d 6) δ: 1.81–1.87 (2H, m, CH2), 3.44 (2H, t, J = 5.4 Hz, CH2), 3.70 (2H, t, J = 6.1 Hz, CH2), 6.49 (2H, br s, NH2), 6.87–6.95 (2H, m, Ar), 7.27–7.31 (1H, m, Ar), 7.87 (1H, dd, J = 7.9, 1.1 Hz, Ar); 13C-NMR (100 MHz, DMSO-d 6) δ: 20.0, 42.8, 42.9, 118.9, 120.7, 122.7, 124.3, 131.1, 145.6, 146.6, 151.6; HRMS (FAB): m/z calcd for C11H13N4 [M + H]+ 201.1140; found: 201.1138.

Synthesis of 3,4-Dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-one (11)

3,4-Dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazine-6-thione 10 (58.6 mg, 0.25 mmol) was suspended into a 0.1 M NaOH in MeOH-H2O (9:1, 5 mL). After being stirred under reflux for 12 h, the mixture was concentrated. To a stirring solution of the residue and Et3N (0.029 mL, 2.0 mmol) in CH2Cl2 (16.6 mL) was added dropwise a solution of triphosgene (155.8 mg, 0.52 mmol) in CH2Cl2 (1.7 mL) at 0 °C. After being stirred at rt for 1 h, the mixture was quenched with sat. NaHCO3. The whole was extracted with CHCl3. The extract was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (9:1) to give the title compound 11 as colorless solid (35.3 mg, 65 %): mp 102–103 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1639 (C=O) 1612 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.95-1.99 (2H, m, CH2), 3.73 (2H, t, J = 5.7 Hz, CH2), 4.00 (2H, t, J = 6.0 Hz, CH2), 7.13 (1H, dd, J = 8.0, 1.3 Hz, Ar), 7.27–7.30 (1H, m, Ar), 7.40 (1H, td, J = 8.0, 1.1 Hz, Ar), 8.28 (1H, dd, J = 8.0, 1.1 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.8, 42.4, 45.2, 124.4, 125.8, 126.8, 128.9, 129.2, 130.9, 146.1, 162.8; HRMS (FAB): m/z calcd for C11H11N2OS [M + H]+ 219.0592; found: 219.0592.

Synthesis of 9-(N,N-Dimethylamino)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25a)

N -( tert -Butyl)-9-( N′ ,N′ H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22a). To a mixture of N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (88.1 mg, 0.25 mmol) and Pd(OAc)2 (5.6 mg, 0.025 mmol) and KOt-Bu (84.2 mg, 0.75 mmol) in toluene (2.0 mL) were added P(tert-Bu)3 (0.009 mL, 0.038 mmol) and 2 N Me2NH in THF (0.38 mL, 0.75 mmol). After being stirred at reflux for 1 h, the mixture was filtered through a Celite pad and concentrated. The residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) to give the title compound 22a as colorless solid (80.9 mg, >99 %): mp 161–162 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1587 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.38 (9H, s, 3 × CH3), 1.86-1.92 (2H, m, CH2), 2.97 (6H, s, 2 × CH3), 3.58 (2H, t, J = 5.5 Hz, CH2), 3.85 (2H, t, J = 6.1 Hz, CH2), 6.28 (1H, d, J = 2.7 Hz, Ar), 6.55 (1H, dd, J = 9.0, 2.7 Hz, Ar), 8.04 (1H, d, J = 9.0 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 22.0, 30.0 (3C), 40.0 (2C), 44.9, 45.5, 54.0, 105.5, 110.6, 115.7, 129.7, 130.0, 139.2, 148.0, 151.2; HRMS (FAB): m/z calcd for C17H25N4S [M + H]+ 317.1800; found: 317.1803.

Compound 25a. TFA (2.0 mL) was added to a mixture of 22a (63.3 mg, 0.2 mmol) in small amount of CHCl3 and MS4 Å (300 mg, powder, activated by heating with Bunsen burner). After being stirred under reflux for 1 h, the mixture was concentrated. To a stirring mixture of the residue in CHCl3 was added dropwise Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) to give the title compound 25a as colorless solid (38.2 mg, 73 %): mp 150–151 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1600 (C=N), 1562 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.93–1.98 (2H, m, CH2), 2.98 (6H, s, 2 × CH3), 3.64 (2H, t, J = 5.7 Hz, CH2), 4.00 (2H, t, J = 6.3 Hz, CH2), 6.17 (1H, d, J = 2.3 Hz, Ar), 6.55 (1H, dd, J = 9.2, 2.3 Hz, Ar), 7.01 (1H, br s, NH), 8.05 (1H, d, J = 9.2 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.1, 40.0 (2C), 43.8, 44.7, 104.4, 110.7, 114.4, 129.8, 129.9, 146.7, 151.3, 154.2; HRMS (FAB): m/z calcd for C13H17N4S [M + H]+ 261.1174; found: 261.1173.

Synthesis of 3,4-Dihydro-9-(N-methylamino)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25b)

9-Amino- N-(tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (28). To a suspension of N-(tert-Butyl)-3,4-dihydro-9-nitro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22e (477.0 mg, 1.5 mmol) in EtOH (10 mL) was added 10 % Pd/C (ca. 55 % in water, 400 mg) under a H2 atmosphere. After being stirred at rt overnight, the mixture was filtered through a Celite pad. After concentration, the resulting solid was recrystallized from CHCl3–n-hexane to give the title compound 28 as colorless crystals (381.1 mg, 88 %): mp 152–155 °C; IR (neat) cm−1: 1589 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.37 (9H, s, 3 × CH3), 1.86-1.92 (2H, m, CH2), 3.57 (2H, t, J = 5.4 Hz, CH2), 3.84 (2H, t, J = 6.0 Hz, CH2), 3.88 (2H, br s, NH2), 6.33 (1H, d, J = 2.2 Hz, Ar), 6.49 (1H, dd, J = 8.5, 2.2 Hz, Ar), 7.99 (1H, d, J = 8.5 Hz, Ar); 13C-NMR (100 MHz, CD3OD) δ: 22.7, 30.2 (3C), 45.2, 46.8, 55.2, 109.1, 114.4, 116.4, 130.7, 131.4, 140.5, 151.8, 152.4; HRMS (FAB): m/z calcd for C15H21N4S [M + H]+ 289.1487; found: 289.1489.

N -( tert -Butyl)-3,4-dihydro-9-( N -methylamino)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22b). To a flask containing 28 (108.5 mg, 0.38 mmol), MeONa (30.6 mg, 0.57 mmol), and paraformaldehyde (34.2 mg, 1.1 mmol) was added unhydrous MeOH (2.5 mL) under an Ar atmosphere, and stirring was continued for 5 h under reflux. Then, NaBH4 (28.8 mg, 0.76 mmol) was added to the mixture and stirring was continued for additional 30 min under reflux. After concentration, the residue was dissolved in EtOAc, and washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by flash column chromatography over aluminum oxide with n-hexane–EtOAc (1:1) to give the title compound 22b as yellow solid (104.9 mg, 91 %): mp 156–158 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1590 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.38 (9H, s, 3 × CH3), 1.87–1.92 (2H, m, CH2), 2.83 (3H, s, CH3), 3.57 (2H, t, J = 5.4 Hz, CH2), 3.85 (2H, t, J = 6.0 Hz, CH2), 4.04 (1H, br s, NH), 6.20 (1H, d, J = 2.4 Hz, Ar), 6.43 (1H, dd, J = 8.8, 2.4 Hz, Ar), 8.01 (1H, d, J = 8.8 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 30.2, 44.7, 45.5, 54.0, 104.9, 111.8, 116.3, 129.7, 130.4, 139.0, 148.3, 150.6; HRMS (FAB): m/z calcd for C16H23N4S [M + H]+ 303.1643; found: 303.1638.

Compound 25b. Using the general procedure as described for 25a, compound 22b (30.7 mg, 0.1 mmol) was allowed to react for 1 h with TFA (1.0 mL) and MS4Å (200 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1 to 0:1) gave the title compound 25b as pale yellow solid (9.0 mg, 37 %): mp 129–131 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1602 (C=N), 1555 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.92–1.98 (2H, m, CH2), 2.84 (3H, d, J = 4.1 Hz, CH3), 3.64 (2H, t, J = 5.6 Hz, CH2), 4.00 (2H, t, J = 6.2 Hz, CH2), 4.03 (1H, br s, NH), 6.11 (1H, d, J = 2.4 Hz, Ar), 6.44 (1H, dd, J = 8.8, 2.4 Hz, Ar), 8.01 (1H, d, J = 8.8 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.1, 30.2, 43.9, 44.6, 104.0, 111.9, 129.2, 130.1, 130.3, 146.9, 150.8, 154.1; Anal. calcd for C12H14N4S: C, 58.51; H, 5.73; N, 22.74. Found: C, 58.30; H, 5.62; N, 22.45.

Synthesis of 9-(N-Acetylamino)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25c)

9-( N -Acetylamino)- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22c). To a mixture of 9-amino-N-(tert-butyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 28 (100.9 mg, 0.35 mmol), Et3N (0.015 mL, 1.05 mmol), DMAP (4.3 mg, 0.04 mmol) in CH2Cl2 (3.5 mL) was added Ac2O (0.066 mL, 0.70 mmol) under an Ar atmosphere. After being stirred under reflux for 1 h, sat. NaHCO3 was added to the mixture. The whole was extracted with EtOAc. The extract was washed with brine, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1 to 0:1) to give the title compound 22c as colorless solid (120.1 mg, > 99 %): mp 213–214 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1680 (C=O), 1596 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.37 (9H, s, 3 × CH3), 1.88–1.93 (2H, m, CH2), 2.15 (3H, s, CH3), 3.59 (2H, t, J = 5.4 Hz, CH2), 3.86 (2H, t, J = 6.1 Hz, CH2), 6.99 (1H, dd, J = 8.7, 2.1 Hz, Ar), 7.74 (1H, d, J = 2.1 Hz, Ar), 7.96 (1H, br s, NH), 8.08 (1H, d, J = 8.7 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 24.6, 29.9 (3C), 44.9, 45.4, 54.2, 114.4, 116.8, 123.1, 129.1, 130.4, 138.2, 139.7, 147.8, 168.6; HRMS (FAB): m/z calcd for C17H23N4OS [M + H]+ 331.1593; found: 331.1590.

Compound 25c. Using the general procedure as described for 28a, compound 25c (120.1 mg, 0.36 mmol) was allowed to react for 10 h. Purification by recrystallization from MeOH–CHCl3–Et2O gave the title compound 25c as pale yellow crystals (64.9 mg, 65 %): mp 214 °C (decomp.); IR (neat) cm−1: 1681 (C=O), 1619 (C=N), 1550 (C=N); 1H-NMR (400 MHz, DMSO-d 6) δ: 1.85-1.91 (2H, m, CH2), 2.07 (3H, s, CH3), 3.55 (2H, t, J = 5.5 Hz, CH2), 3.92 (2H, t, J = 6.0 Hz, CH2), 7.32 (1H, dd, J = 8.9, 1.8 Hz, Ar), 7.61 (1H, d, J = 1.8 Hz, Ar), 8.10 (1H, d, J = 8.9 Hz, Ar), 9.14 (1H, br s, NH), 10.27 (1H, s, NH); 13C-NMR (100 MHz, DMSO-d 6) δ: 20.3, 24.1, 43.3, 43.6, 112.2, 116.7, 119.3, 129.2, 129.9, 141.7, 146.3, 149.5, 169.0; HRMS (FAB): m/z calcd for C13H15N4OS [M + H]+ 275.0967; found: 275.0967.

Synthesis of 9-Acetyl-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25d)

To a mixture of N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (100 mg, 0.284 mmol), Pd(OAc)2 (6.4 mg, 0.0284 mmol), K2CO3 (120 mg, 0.852 mmol) and dppp (23.7 mg, 0.0568 mmol) in H2O (0.57 mL) was added ethylene glycol monovinyl ether (0.13 mL, 1.42 mmol). After being stirred at reflux for 12 h, the whole was extracted with CHCl3. The extract was washed with brine, and dried over Na2SO4. After concentration, TFA (2.84 mL) was added to resulting residue. After being stirred under reflux for 1.5 h, the mixture was added dropwise to Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with brine, and dried over Na2SO4. After concentration, the residue was purified by preparative TLC over aluminum oxide with n-hexane–EtOAc (7:3) to give the title compound 25d as pale yellow solid (9.7 mg, 13 %): mp 148.4 °C; IR (neat) cm−1: 1678 (C=O), 1616 (C=N), 1567 (C=N); 1H-NMR (300 MHz, CDCl3) δ: 1.95-2.03 (2H, m, CH2), 2.60 (3H, s, CH3), 3.72 (2H, t, J = 5.7 Hz, CH2), 4.03 (2H, t, J = 6.3 Hz, CH2), 7.63 (1H, d, J = 1.8 Hz, Ar), 7.74 (1H, dd, J = 8.3, 1.7 Hz, Ar), 8.32 (1H, d, J = 7.8 Hz, Ar); 13C-NMR (75 MHz, CDCl3) δ: 20.9, 26.7, 43.8, 45.1, 123.6, 125.7, 129.3, 129.6, 130.4, 138.3, 146.0, 152.6, 196.7; Anal. calcd for C13H13N3OS: C, 60.21; H, 5.05; N, 16.20. Found: C, 60.16; H, 5.02; N, 15.94.

Synthesis of 3,4-Dihydro-9-nitro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25e)

N -( tert -Butyl)-3,4-dihydro-9-nitro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22e). To a mixture of 2-(2-fluoro-4-nitrophenyl)-1,4,5,6-tetrahydropyrimidine 18e (2.0 g, 9.0 mmol) and NaH (716.8 mg, 17.9 mmol; 60 % oil suspension) in DMF (29.8 mL) was added tert-butylisothiocyanate (2.28 mL, 17.9 mmol) under an Ar atmosphere, and the mixture was stirred at −20 °C to rt for 2 days. The whole was extracted with EtOAc, and the extract was washed with sat. NaHCO3, brine, and dried over Na2SO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) to give the title compound 22e as pale yellow solid (1.77 g, 62 %): mp 152–153 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1591 (NO2), 1581 (C=N), 1523 (NO2); 1H-NMR (500 MHz, CDCl3) δ: 1.39 (9H, s, 3 × CH3), 1.91–1.96 (2H, m, CH2), 3.66 (2H, t, J = 5.2 Hz, CH2), 3.88 (2H, t, J = 5.7 Hz, CH2), 7.97 (1H, dd, J = 9.7, 2.3 Hz, Ar), 8.01 (1H, d, J = 2.3 Hz, Ar), 8.39 (1H, d, J = 9.2 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.7, 30.0 (3C), 45.3, 45.5, 54.5, 119.9, 120.3, 130.0, 131.1, 132.8, 136.1, 146.5, 148.5; HRMS (FAB): m/z calcd for C15H19N4O2S [M + H]+ 319.1229; found: 319.1229.

Compound 25e. Using the general procedure as described for 25a, compound 22e (47.8 mg, 0.15 mmol) was allowed to react for 1 h with TFA (1.5 mL) and MS4Å (225 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (19:1 to 1:1) gave the title compound 25e as pale yellow solid (24.9 mg, 63 %): mp 170–172 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1587 (NO2), 1568 (C=N), 1523 (NO2); 1H-NMR (400 MHz, CDCl3) δ: 1.97–2.03 (2H, m, CH2), 3.74 (2H, t, J = 5.6 Hz, CH2), 4.04 (2H, t, J = 6.2 Hz, CH2), 7.41 (1H, br s, NH), 7.93 (1H, d, J = 2.2 Hz, Ar), 8.00 (1H, dd, J = 9.0, 2.2 Hz, Ar), 8.42 (1H, d, J = 9.0 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 20.8, 43.8, 45.2, 118.9, 120.5, 130.4, 130.8, 131.7, 145.1, 148.7, 151.3; Anal. calcd for C11H10N4O2S: C, 50.37; H, 3.84; N, 21.36. Found: C, 50.29; H, 4.03; N, 21.08.

Synthesis of 3,4-Dihydro-9-methoxy-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25f)

3,4-Dihydro-9-methoxy-2H,6H-pyrimido[1,2-c][1,3]benzothiazine-6-thione 21f (66.1 mg, 0.25 mmol) was suspended into a 0.1 M NaOH in MeOH-H2O (9:1) (5 mL), and the mixture was stirred for 12 h under reflux. After concentration, the residue was suspended in anhydrous EtOH (1 mL). BrCN (53.0 mg, 0.50 mmol) was added under an Ar atmosphere, and the mixture was stirred for 2 h under reflux. The reaction was quenched with 2 N NaOH, and the whole was extracted with CHCl3, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1) to give the title compound 25f as colorless solid (37.6 mg, 61 %): mp 106 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1572 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.94–1.98 (2H, m, CH2), 3.66 (2H, t, J = 5.7 Hz, CH2), 3.81 (3H, s, CH3), 4.01 (2H, t, J = 6.0 Hz, CH2), 6.50 (1H, d, J = 2.3 Hz, Ar), 6.76 (1H, dd, J = 9.0, 2.3 Hz, Ar), 7.15 (1H, br s, NH), 8.15 (1H, d, J = 9.0 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.8, 44.8, 55.5, 107.3, 113.3, 119.5, 130.2, 130.6, 146.2, 153.4, 161.2; Anal. calcd for C12H13N3OS: C, 58.28; H, 5.30; N, 16.99. Found: C, 58.15; H, 5.23; N, 16.79.

Synthesis of 3,4-Dihydro-9-methyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25g)

3,4-Dihydro-9-methyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazine-6-thione 21g (62.1 mg, 0.25 mmol) was subjected to the general procedure as described for 25f to give the title compound 25g as colorless solid (39.2 mg, 68 %): mp 121 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1569 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.94–1.99 (2H, m, CH2), 2.32 (3H, s, CH3), 3.67 (2H, t, J = 5.7 Hz, CH2), 4.01 (2H, t, J = 6.3 Hz, CH2), 6.84 (1H, s, Ar), 7.02 (1H, d, J = 8.6 Hz, Ar), 7.16 (1H, br s, NH), 8.10 (1H, d, J = 8.6 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.1, 21.1, 43.8, 44.9, 123.6, 124.1, 127.4, 128.6, 128.8, 141.1, 146.6, 153.6; HRMS (FAB): m/z calcd for C12H14N3S [M + H]+ 232.0908; found: 232.0912.

Synthesis of 9-(n-Butyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25h)

9-( n -Butyl)- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22h). To a mixture of N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (352.3 mg, 1.0 mmol), n-butylboronic acid (152.9 mg, 1.5 mmol), Pd2(dba)3·CHCl3 (51.8 mg, 0.05 mmol) and Cs2CO3 (391.0 mg, 1.2 mmol) in 1,4-dioxane (2.5 mL) was added P(tert-Bu)3 (0.024 mL, 0.1 mmol) under an Ar atmosphere, the mixture was stirred for 19 h under reflux. The mixture was filtered through a Celite pad, and concentrated. The residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 19:1) to give the title compound 22h as a colorless oil (21.0 mg, 6 %): IR (neat) cm−1: 1593 (C=N); 1H-NMR (400 MHz, CDCl3) δ; 0.91 (3H, t, J = 7.3 Hz, CH3), 1.29-1.36 (2H, m, CH2), 1.38 (9H, s, 3 × CH3), 1.54-1.62 (2H, m, CH2), 1.87–1.93 (2H, m, CH2), 2.57 (2H, t, J = 7.7 Hz, CH2), 3.60 (2H, t, J = 5.4 Hz, CH2), 3.86 (2H, t, J = 6.0 Hz, CH2), 6.91 (1H, d, J = 1.2 Hz, Ar), 7.01 (1H, dd, J = 8.3, 1.2 Hz, Ar), 8.08 (1H, d, J = 8.3 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 13.8, 21.9, 22.2, 30.0 (3C), 33.0, 35.2, 45.0, 45.4, 54.1, 123.9, 125.3, 126.5, 128.3, 128.7, 138.6, 145.4, 147.9; HRMS (FAB): m/z calcd for C19H28N3S [M + H]+ 330.2004; found: 330.1999.

Compound 25h. Using the general procedure as described for 25a, compound 22h (10.3 mg, 0.03 mmol) was allowed to react for 1 h with TFA (1.0 mL) and MS4 Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1) gave the title compound 25h as colorless solid (5.2 mg, 61 %): mp 52–55 °C (from n-hexane); IR (neat) cm−1: 1621 (C=N), 1571 (C=N); 1H-NMR (400 MHz, CDCl3) δ; 0.91 (3H, t, J = 7.3 Hz, CH3), 1.29–1.38 (2H, m, CH2), 1.54–1.61 (2H, m, CH2), 1.93–1.99 (2H, m, CH2), 2.58 (2H, t, J = 7.7 Hz, CH2), 3.67 (2H, t, J = 5.6 Hz, CH2), 4.01 (2H, t, J = 6.2 Hz, CH2), 6.84 (1H, d, J = 1.5 Hz, Ar), 7.03–7.05 (1H, m, Ar), 8.11 (1H, d, J = 8.3 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 13.8, 21.1, 22.2, 33.0, 35.2, 43.8, 44.9, 123.0, 124.4, 126.8, 128.6, 128.8, 146.1, 146.6, 153.7; HRMS (FAB): m/z calcd for C15H20N3S [M + H]+ 274.1378; found: 274.1372.

Synthesis of 9-Fluoro-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25i)

9-Fluoro-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazine-6-thione 21i (63.1 mg, 0.25 mmol) was subjected to the general procedure as described for 25f to give the title compound 25i as colorless solid (30.4 mg, 52 %): mp 123–124 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1624 (C=N), 1585 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.94–2.00 (2H, m, CH2), 3.67 (2H, t, J = 5.7 Hz, CH2), 4.01 (2H, t, J = 6.3 Hz, CH2), 6.75 (1H, dd, J = 8.0, 2.9 Hz, Ar), 6.91 (1H, ddd, J = 8.6, 8.0, 2.9 Hz, Ar), 7.22 (1H, br s, NH), 8.24 (1H, dd, J = 8.6, 5.7 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.8, 44.8, 110.0 (d, J = 25.2 Hz), 113.9 (d, J = 21.6 Hz), 123.1, 130.9 (d, J = 8.4 Hz), 131.5 (d, J = 8.4 Hz), 146.4 (d, J = 155.9 Hz), 152.6, 163.7 (d, J = 254.3 Hz); 19F-NMR (500 MHz, CDCl3) δ: −109.1; Anal. calcd for C11H10FN3S: C, 56.15; H, 4.28; N, 17.86. Found: C, 56.13; H, 4.44; N, 17.78.

Synthesis of 3,4-Dihydro-9-trifluoromethyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25j)

2-(2-Fluoro-4-trifluoromethylphenyl)-1,4,5,6-tetrahydropyrimidine (18j). To a solution of 2-fluoro-4-trifluoromethylbenzaldehyde 15j (1.00 g, 5.21 mmol) in t-BuOH (49 mL) was added propylenediamine (424.7 mg, 5.73 mmol). The mixture was stirred at 70 °C for 30 min, and then K2CO3 (2.16 g, 15.6 mmol) and I2 (1.65 g, 6.51 mmol) were added. After being stirred at same temperature for 3 h, the mixture was quenched with sat. Na2SO3. The organic layer was separated and concentrated. The resulting solid was dissolved with H2O, and then pH was adjusted to 12–14 with 2 N NaOH. The whole was extracted with CHCl3, and the extract was dried over MgSO4. After concentration, the resulting solid was recrystallized from CHCl3–n-hexane to give the title compound 18j as colorless crystals (0.84 g, 65 %): mp 108–110 °C; IR (neat) cm−1: 1620 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.86–1.90 (2H, m, CH2), 3.52 (4H, t, J = 5.2 Hz, 2 × CH2), 5.34 (1H, br s, NH), 7.33 (1H, d, J = 11.5 Hz, Ar), 7.42 (1H, d, J = 8.6 Hz, Ar), 7.96 (1H, dd, J = 8.6, 8.0 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 20.5, 42.2 (2C), 113.4 (dq, J = 26.9, 3.9 Hz), 120.9–121.0 (m), 123.0 (dq, J = 273.0, 2.5 Hz), 128.0 (d, J = 13.2 Hz), 131.5 (d, J = 4.1 Hz), 132.8 (dq, J = 33.7, 9.1 Hz), 150.4, 159.6 (d, J = 249.1 Hz); 19F-NMR (500 MHz, CDCl3) δ: −115.1, −63.4; Anal. calcd for C11H10F4N2: C, 53.66; H, 4.09; N, 11.38. Found: C, 53.82; H, 4.06; N, 11.43.

N -( tert -Butyl)-3,4-dihydro-9-trifluoromethyl-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22j). Using the general procedure as described for 22e, compound 18j (246.2 mg, 1.0 mmol) was allowed to react at 80 °C for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 22j as colorless solid (219.4 mg, 64 %): mp 82 °C (from n-hexane); IR (neat) cm−1: 1601 (C=N), 1569 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.39 (9H, s, 3 × CH3), 1.90–1.95 (2H, m, CH2), 3.64 (2H, t, J = 5.4 Hz, CH2), 3.88 (2H, t, J = 6.3 Hz, CH2), 7.38 (1H, s, Ar), 7.41 (1H, d, J = 8.6 Hz, Ar), 8.31 (1H, d, J = 8.6 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 29.9 (3C), 45.2, 45.4, 54.3, 121.6 (q, J = 4.0 Hz), 122.4 (q, J = 3.6 Hz), 123.5 (q, J = 272.7 Hz), 129.2, 130.1, 130.7, 132.0 (q, J = 33.2 Hz), 136.9, 146.9; 19F-NMR (500 MHz, CDCl3) δ: −63.6; HRMS (FAB): m/z calcd for C16H19F3N3S [M + H]+ 342.1252; found: 342.1252.

Compound 25j. Using the general procedure as described for 25a, compound 22j (68.3 mg, 0.20 mmol) was allowed to react for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (8:2) gave the title compound 25j as colorless solid (48.2 mg, 84 %): mp 91.5 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1625 (C=N), 1561 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.96–2.01 (2H, m, CH2), 3.71 (2H, t, J = 5.7 Hz, CH2), 4.03 (2H, t, J = 6.3 Hz, CH2), 7.27 (2H, m, Ar, NH), 7.44 (1H, dd, J = 8.3, 1.4 Hz, Ar), 8.35 (1H, d, J = 8.6 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.9, 43.8, 45.0, 120.7 (q, J = 4.0 Hz), 122.7 (q, J = 3.2 Hz), 123.3 (q, J = 272.7 Hz), 129.6, 129.7, 129.9, 132.5 (q, J = 33.2 Hz), 145.6, 152.1; 19F-NMR (500 MHz, CDCl3) δ: −63.8; Anal. calcd for C12H10F3N3S: C, 50.52; H, 3.53; N, 14.73. Found: C, 50.51; H, 3.50; N, 14.69.

Synthesis of 9-Bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25k)

2-(4-Bromo-2-fluorophenyl)-1,4,5,6-tetrahydropyrimidine (18k). 4-Bromo-2-fluorobenzaldehyde 15k (1.02 g, 5.0 mmol) was subjected to the general procedure as described for 18j to give the title compound 18k as colorless crystals (0.80 g, 62 %): mp 135–137 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1622 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.83–1.89 (2H, m, CH2), 3.49 (4H, t, J = 5.9 Hz, 2 × CH2), 4.88 (1H, br s, NH), 7.24 (1H, dd, J = 11.2, 2.0 Hz, Ar), 7.30 (1H, dd, J = 8.5, 2.0 Hz, Ar), 7.71 (1H, dd, J = 8.5, 8.3 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 20.6, 42.3 (2C), 119.5 (d, J = 27.3 Hz), 123.4 (d, J = 3.3 Hz), 123.6 (d, J = 5.0 Hz), 127.7 (d, J = 3.3 Hz), 131.6 (d, J = 4.1 Hz), 150.7, 159.8 (d, J = 251.6 Hz); 19F-NMR (500 MHz, CDCl3) δ: −114.7; Anal. calcd for C10H10BrFN2: C, 46.72; H, 3.92; N, 10.90. Found: C, 46.66; H, 3.82; N, 10.87.

9-Bromo- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22k). Using the general procedure as described for 22e, compound 18k (257.1 mg, 1.00 mmol) was allowed to react at rt overnight. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 22k as colorless solid (295.6 mg, 84 %): mp 107–108 °C (from n-hexane); IR (neat) cm−1: 1596 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.38 (9H, s, 3 × CH3), 1.87–1.93 (2H, m, CH2), 3.60 (2H, t, J = 5.6 Hz, CH2), 3.85 (2H, t, J = 6.1 Hz, CH2), 7.26–7.31 (2H, m, Ar), 8.05 (1H, d, J = 8.5 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.0, 45.4, 54.3, 124.4, 126.7, 126.8, 129.1, 130.1, 130.9, 137.2, 147.2; Anal. calcd for C15H18BrN3S: C, 51.14; H, 5.15; N, 11.93. Found: C, 51.30; H, 5.07; N, 11.82.

Compound 25k. Using the general procedure as described for 25a, compound 22k (52.8 mg, 0.15 mmol) was allowed to react for 2 h with TFA (1.5 mL) and MS4Å (225 mg). Purification by flash chromatography over silica gel with n-hexane–EtOAc (2:1) gave the title compound 25k as colorless solid (40.2 mg, 91 %): mp 104–105 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1569 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.94–1.99 (2H, m, CH2), 3.67 (2H, t, J = 5.5 Hz, CH2), 4.00 (2H, t, J = 6.0 Hz, CH2), 7.19–7.34 (3H, m, NH, Ar), 8.08 (1H, d, J = 8.8 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 20.9, 43.8, 44.9, 125.0, 125.6, 125.9, 129.5, 130.4, 130.7, 145.8, 152.4; Anal. calcd for C11H10BrN3S: C, 44.61; H, 3.40; N, 14.19. Found: C, 44.37; H, 3.28; N, 13.93.

Synthesis of 3,4-Dihydro-9-phenyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25l)

N -(tert-Butyl)-3,4-dihydro-9-phenyl-2 H ,6 H -pyrimido[1,2-c][1,3]benzothiazin-6-imine (22l). To a solution of N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) and phenylboronic acid (21.9 mg, 0.18 mmol) in a mixture of toluene (1.5 mL), EtOH (0.9 mL) and 1 M aq. K2CO3 (1.5 mL) was added Pd(PPh3)4 (6.9 mg, 4 mol %) and PdCl2(dppf)·CH2Cl2 (3.7 mg, 3 mol %). After being stirred at reflux for 1 h, the mixture was extracted with CHCl3. The extract was dried over MgSO4 and concentrated. The residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) to give the title compound 22l as colorless solid (44.8 mg, 85 %): mp 122.5–124 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1592 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.40 (9H, s, 3 × CH3), 1.90–1.95 (2H, m, CH2), 3.64 (2H, t, J = 5.4 Hz, CH2), 3.89 (2H, t, J = 6.0 Hz, CH2), 7.33–7.37 (2H, m, Ar), 7.41–7.44 (3H, m, Ar), 7.58 (2H, d, J = 6.9 Hz, Ar), 8.25 (1H, d, J = 8.6 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 122.7, 124.8, 126.5, 127.0 (2C), 128.0, 128.8 (2C), 128.9, 129.5, 138.3, 139.4, 142.9, 147.7; HRMS (FAB): m/z calcd for C21H24N3S [M + H]+ 350.1691; found: 350.1683.

Compound 25l. Using the general procedure as described for 25a, compound 22l (25.1 mg, 0.07 mmol) was allowed to react for 1 h with TFA (1.0 mL) and MS4Å (105 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (8:2) gave the title compound 25l as pale yellow solid (19.4 mg, 92 %): mp 122–124 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1619 (C=N), 1567 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.97–2.02 (2H, m, CH2), 3.72 (2H, t, J = 5.4 Hz, CH2), 4.04 (2H, t, J = 6.3 Hz, CH2), 7.25–7.26 (1H, m, Ar), 7.37–7.40 (1H, m, Ar), 7.43–7.47 (3H, m, Ar), 7.58 (2H, d, J = 7.4 Hz, Ar), 8.29 (1H, d, J = 8.6 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.1, 43.8, 45.0, 121.8, 121.8, 125.1, 125.5, 127.0 (2C), 128.2, 128.9 (2C), 129.4, 139.2, 143.5, 146.5, 153.4; HRMS (FAB): m/z calcd for C17H16N3S [M + H]+ 294.1065; found: 294.1069.

Synthesis of 3,4-Dihydro-9-vinyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25m)

N -( tert -Butyl)-3,4-dihydro-9-vinyl-2 H ,6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22m). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (528.4 mg, 1.5 mmol) was allowed to react with vinylboronic acid pinacol ester (0.305 mL, 1.8 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 22m as colorless solid (455.7 mg, > 99 %): mp 67–68 °C (from n-hexane); IR (neat) cm−1: 1589 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.39 (9H, s, 3 × CH3), 1.88–1.94 (2H, m, CH2), 3.62 (2H, t, J = 5.6 Hz, CH2), 3.87 (2H, t, J = 6.1 Hz, CH2), 5.33 (1H, d, J = 11.0 Hz, CH), 5.79 (1H, d, J = 17.6 Hz, CH), 6.64 (1H, dd, J = 17.6, 11.0 Hz, CH), 7.12 (1H, d, J = 1.7 Hz, Ar), 7.23 (1H, dd, J = 8.3, 1.7 Hz, Ar), 8.14 (1H, d, J = 8.3 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.1, 115.9, 122.1, 123.7, 127.0, 128.6, 129.3, 135.4, 138.3, 139.3, 147.7; HRMS (FAB): m/z calcd for C17H22N3S [M + H]+ 300.1534; found: 300.1536.

Compound 25m. Using the general procedure as described for 25a, compound 22m (60.4 mg, 0.2 mmol) was allowed to react for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (8:2) gave the title compound 25m as colorless solid (42.1 mg, 87 %): mp 76–77 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1618 (C=N), 1564 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.95-2.01 (2H, m, CH2), 3.69 (2H, t, J = 5.4 Hz, CH2), 4.02 (2H, t, J = 6.1 Hz, CH2), 5.36 (1H, d, J = 10.9 Hz, CH), 5.81 (1H, d, J = 17.7 Hz, CH), 6.65 (1H, dd, J = 17.7, 10.9 Hz, CH), 7.04 (1H, s, Ar), 7.20 (1H, br s, NH), 7.26–7.28 (1H, m, Ar), 8.17 (1H, d, J = 8.5 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 116.4, 121.1, 124.0, 125.8, 129.0 (2C), 135.2, 139.8, 146.4, 153.3; HRMS (FAB): m/z calcd for C13H14N3S [M + H]+ 244.0908; found: 244.0911.

Synthesis of 3,4-Dihydro-9-styryl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25n)

N -( tert -Butyl)-3,4-dihydro-9-styryl-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22n). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with styrylboronic acid pinacol ester (41.4 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 22n as colorless solid (50.9 mg, 90 %): mp 124.5–125 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1590 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (9H, s, 3 × CH3), 1.88–1.94 (2H, m, CH2), 3.63 (2H, t, J = 5.5 Hz, CH2), 3.87 (2H, t, J = 6.1 Hz, CH2), 7.01 (1H, d, J = 16.3 Hz, CH), 7.14 (1H, d, J = 16.3 Hz, CH), 7.22 (1H, d, J = 1.7 Hz, Ar), 7.27–7.38 (4H, m, Ar), 7.50 (2H, d, J = 7.3 Hz, Ar), 8.17 (1H, d, J = 8.3 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 122.2, 124.0, 126.6, 126.7 (2C), 127.0, 128.1, 128.7 (2C), 128.8, 129.4, 130.7, 136.8, 138.3, 139.2, 147.7; HRMS (FAB): m/z calcd for C23H26N3S [M + H]+ 376.1847; found: 376.1845.

Compound 25n. Using the general procedure as described for 25a, compound 22n (31.7 mg, 0.084 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 25n as colorless solid (20.2 mg, 75 %): mp 111–113 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1618 (C=N), 1567 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.94–2.00 (2H, m, CH2), 3.69 (2H, t, J = 5.6 Hz, CH2), 4.02 (2H, t, J = 6.2 Hz, CH2), 7.00 (1H, d, J = 16.3 Hz, CH), 7.12–7.16 (2H, m, CH, Ar), 7.20 (1H, br s, NH), 7.26–7.30 (1H, m, Ar), 7.34–7.38 (3H, m, Ar), 7.50 (2H, d, J = 7.6 Hz, Ar), 8.20 (1H, d, J = 8.5 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 121.2, 124.2, 125.5, 126.6, 126.7 (2C), 128.2, 128.7 (2C), 129.1, 129.2, 131.1, 136.6, 139.7, 146.4, 153.3; Anal. calcd for C19H17N3S: C, 71.44; H, 5.36; N, 13.15. Found: C, 71.17; H, 5.24; N, 13.07.

Synthesis of 3,4-Dihydro-9-pentenyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25o)

N -( tert -Butyl)-3,4-dihydro-9-pentenyl-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22o). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with pentenylboronic acid pinacol ester (35.2 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 22o as a colorless oil (44.2 mg, 86 %): IR (neat) cm−1: 1590 (C=N); 1H-NMR (400 MHz, CDCl3) δ; 0.95 (t, J = 7.4 Hz, 3H, CH3), 1.38 (9H, s, 3 × CH3), 1.46–1.54 (2H, m, CH2), 1.87–1.93 (2H, m, CH2), 2.16–2.21 (2H, m, CH2), 3.61 (2H, t, J = 5.6 Hz, CH2), 3.86 (2H, t, J = 6.2 Hz, CH2), 6.29–6.30 (2H, m, 2 × CH), 7.05 (1H, d, J = 1.7 Hz, Ar), 7.17 (1H, dd, J = 8.3, 1.7 Hz, Ar), 8.10 (1H, d, J = 8.3 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 13.7, 21.9, 22.3, 30.0 (3C), 35.1, 45.1, 45.4, 54.1, 121.6, 123.6, 126.0, 128.5, 128.6, 129.1, 133.4, 138.5, 139.8, 147.8; HRMS (FAB): m/z calcd for C20H28N3S [M + H]+ 342.2004; found: 342.2007.

Compound 25o. Using the general procedure as described for 25a, compound 22o (40.0 mg, 0.12 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (8:2) gave the title compound 25o as a colorless oil (31.9 mg, 95 %): IR (neat) cm−1: 1619 (C=N), 1568 (C=N); 1H-NMR (400 MHz, CDCl3) δ; 0.95 (3H, t, J = 7.4 Hz, CH3), 1.45–1.54 (2H, m, CH2), 1.93–1.99 (2H, m, CH2), 2.17–2.22 (2H, m, CH2), 3.68 (2H, t, J = 5.5 Hz, CH2), 4.01 (2H, t, J = 6.2 Hz, CH2), 6.29–6.31 (2H, m, 2 × CH), 6.96 (1H, d, J = 1.7 Hz, Ar), 7.16 (1H, br s, NH), 7.19 (1H, dd, J = 8.5, 1.7 Hz, Ar), 8.13 (1H, d, J = 8.5 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 13.7, 21.0, 22.3, 35.1, 43.8, 44.9, 120.6, 123.8, 124.9, 128.3, 128.9, 129.0, 133.9, 140.3, 146.5, 153.5; HRMS (FAB): m/z calcd for C16H20N3S [M + H]+ 286.1378; found:286.1376.

Synthesis of 9-Azido-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25p)

9-Azido- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22p). To a solution of 9-amino-N-(tert-butyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 28 (100.9 mg, 0.35 mmol) in AcOH (2 mL) and H2O (1 mL) was added NaNO2 (33.8 mg, 0.49 mmol) at 0 °C, and the stirring was continued for 1 h. NaN3 (34.1 mg, 0.53 mmol) was added to the reaction mixture, and stirring was continued for 30 min at rt. Reaction mixture was neutralized with K2CO3, and the whole was extracted with CHCl3, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1) to give the title compound 22p as pale yellow solid (77.3 mg, 70 %): mp 79–80 °C (from n-hexane); IR (neat) cm−1: 2104 (N3), 1592 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.38 (9H, s, 3 × CH3), 1.88–1.94 (2H, m, CH2), 3.60 (2H, t, J = 5.6 Hz, CH2), 3.86 (2H, t, J = 6.2 Hz, CH2), 6.74 (1H, d, J = 2.3 Hz, Ar), 6.84 (1H, dd, J = 8.5, 2.3 Hz, Ar), 8.19 (1H, d, J = 8.5 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.0, 45.4, 54.2, 114.2, 116.8, 124.5, 130.3, 130.9, 137.4, 142.0, 147.1; HRMS (FAB): m/z calcd for C15H19N6S [M + H]+ 315.1392; found: 315.1398.

Compound 25p. Using the general procedure as described for 25a, compound 22p (77.3 mg, 0.25 mmol) was allowed to react for 2 h with TFA (3.5 mL) and MS4 Å (525 mg). Purification by recrystallization from MeOH–Et2O gave the title compound 25p as pale yellow crystals (27.0 mg, 42 %): mp 120–121 °C; IR (neat) cm−1: 2107 (N3), 1615 (C=N), 1569 (C=N); 1H-NMR (400 MHz, DMSO-d 6) δ: 1.82–1.88 (2H, m, CH2), 3.56 (2H, t, J = 5.5 Hz, CH2), 3.89 (2H, t, J = 5.4 Hz, CH2), 6.97 (1H, dd, J = 8.8, 2.4 Hz, Ar), 7.03 (1H, d, J = 2.4 Hz, Ar), 8.17 (1H, d, J = 8.8 Hz, Ar), 8.76 (1H, s, NH); 13C-NMR (100 MHz, DMSO-d 6) δ: 20.6, 43.1, 44.2, 113.7, 117.0, 122.6, 130.2, 130.8, 141.9, 144.7, 150.0; Anal. calcd for C11H10N6S: C, 51.15; H, 3.90; N, 32.54. Found: C, 51.07; H, 3.88; N, 32.28.

Synthesis of 9-(4-Benzoylphenyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (25q)

9-(4-Benzoylphenyl)- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (22q). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-benzoylphenylboronic acid (40.7 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (8:2) gave the title compound 22q as colorless solid (55.6 mg, 82 %): mp 187–189 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1656 (C=O), 1593 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.41 (9H, s, 3 × CH3), 1.91–1.97 (2H, m, CH2), 3.65 (2H, t, J = 5.5 Hz, CH2), 3.90 (2H, t, J = 6.1 Hz, CH2), 7.39 (1H, d, J = 1.7 Hz, Ar), 7.46–7.53 (3H, m, Ar), 7.60 (1H, t, J = 7.4 Hz, Ar), 7.70 (2H, d, J = 8.0 Hz, Ar), 7.82 (2H, d, J = 7.3 Hz, Ar), 7.88 (2H, d, J = 8.0 Hz, Ar), 8.30 (1H, d, J = 8.3 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.2, 45.4, 54.2, 123.0, 124.8, 126.9 (2C), 127.4, 128.3 (2C), 129.1, 129.9, 130.0 (2C), 130.7 (2C), 132.5, 136.9, 137.6, 137.9, 141.7, 143.3, 147.6, 196.1; HRMS (FAB): m/z calcd for C28H28N3OS [M + H]+ 454.1953; found: 454.1954.

Compound 25q. Using the general procedure as described for 25a, compound 22q (30.4 mg, 0.067 mmol) was allowed to react for 1 h with TFA (1.0 mL) and MS4 Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 25q as colorless solid (16.7 mg, 63 %): mp 155–156 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1655 (C=O), 1619 (C=N), 1561 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.97–2.03 (2H, m, CH2), 3.72 (2H, t, J = 5.5 Hz, CH2), 4.05 (2H, t, J = 6.1 Hz, CH2), 7.30 (1H, d, J = 1.7 Hz, Ar), 7.48–7.52 (3H, m, Ar), 7.59–7.63 (1H, m, Ar), 7.68 (2H, d, J = 8.3 Hz, Ar), 7.81–7.83 (2H, m, Ar), 7.89 (2H, d, J = 8.3 Hz, Ar), 8.32 (1H, d, J = 8.5 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 122.0, 125.1, 126.2, 126.9 (2C), 128.3 (2C), 129.5, 129.6, 130.0 (2C), 130.7 (2C), 132.5, 137.1, 137.5, 142.2, 143.0, 146.3, 153.0, 196.0; HRMS (FAB): m/z calcd for C20H18N3OS [M + H]+ 398.1327; found: 398.1333.

Synthesis of 10-(N,N-Dimethylamino)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (26a)

N -( tert -Butyl)-10-( N,N -dimethylamino)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (23a). To a mixture of 10-bromo-N-(tert-butyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 23k (600.2 mg, 1.70 mmol) and Pd(Pt-Bu3)2 (174.2 mg, 0.341 mmol) and KOt-Bu (573.3 mg, 5.11 mmol) in toluene (1.7 mL) was added 2.0 M Me2NH in THF (2.55 mL, 5.11 mmol). The reaction was heated using a microwave reactor (standard mode) for 10 min at 170 °C. The whole was extracted with EtOAc. The extract was washed with brine, and dried over Na2SO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (6:4 to 5:5) to give the title compound 23a as pale yellow solid (363.3 mg, 67.4 %): mp 86.1 °C; IR (neat) cm−1: 1583 (C=N); 1H-NMR (300 MHz, CDCl3) δ: 1.38 (9H, s, 3 × CH3), 1.86–1.94 (2H, m, CH2), 2.97 (6H, s, 2 × CH3), 3.61 (2H, t, J = 5.3 Hz, CH2), 3.86 (2H, t, J = 6.3 Hz, CH2), 6.78 (1H, dd, J = 9.0, 3.0 Hz, Ar), 6.98 (1H, d, J = 8.4 Hz, Ar), 7.56 (1H, d, J = 2.4 Hz, Ar); 13C-NMR (75 MHz, CDCl3) δ: 22.0, 29.9 (3C), 40.8 (2C), 45.1, 45.5, 54.0, 111.6, 115.4, 115.8, 125.3, 128.7, 139.7, 148.8, 149.3; HRMS (FAB): m/z calcd for C17H25N4S [M + H]+ 317.1800; found: 317.1796.

Compound 26a. TFA (0.63 mL) was added to a mixture of 23a (20 mg, 0.063 mmol) and MS4Å (110 mg, powder, activated by heating with Bunsen burner) in small amount of CHCl3. After being stirred under reflux for 40 min, the mixture was added dropwise to Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3, brine, and dried over Na2SO4. After concentration, the residue was purified by preparative TLC over aluminum oxide with n-hexane–EtOAc (7:3) to give the title compound 26a as yellow solid (11.4 mg, 68.3 %): mp 134.5 °C; IR (neat) cm−1: 1617 (C=N), 1552 (C=N); 1H-NMR (300 MHz, CDCl3) δ: 1.92–2.00 (2H, m, CH2), 2.97 (6H, s, 2 × CH3), 3.68 (2H, t, J = 5.7 Hz, CH2), 4.01 (2H, t, J = 6.3 Hz, CH2), 6.79 (1H, dd, J = 8.7, 3.3 Hz, Ar), 6.89 (1H, d, J = 8.7 Hz, Ar), 7.08 (1H, br s, NH), 7.58 (1H, d, J = 2.7 Hz, Ar); 13C-NMR (75 MHz, CDCl3) δ: 20.8, 40.6 (2C), 44.1, 44.3, 111.8, 114.6, 116.3, 124.6, 126.3, 148.7, 149.4, 154.4; Anal. calcd for C13H16N4S: C, 59.97; H, 6.19; N, 21.52. Found: C, 59.91; H, 6.19; N, 21.41.

Synthesis of 3,4-Dihydro-10-nitro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (26e)

N -( tert -Butyl)-3,4-dihydro-10-nitro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (23e). To a mixture of 2-(2-bromo-5-nitrophenyl)-1,4,5,6-tetrahydropyrimidine 19e (50 mg, 0.209 mmol) in DMAc (0.70 mL) were added tert-butylisothiocyanate (0.053 mL, 0.418 mmol) and KOt-Bu (46.9 mg, 0.418 mmol) at 0 °C under an N2 atmosphere. After being stirred at 0 °C for 1 h, sat. NH4Cl was added. The whole was extracted with EtOAc. The extract was washed with brine, and dried over Na2SO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (1:0 to 9:1) to give the title compound 23e as pale yellow solid (39.1 mg, 58.9 %): mp 123.8 °C; IR (neat) cm−1: 1593 (NO2), 1520 (NO2); 1H-NMR (300 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.90–1.98 (2H, m, CH2), 3.67 (2H, t, J = 5.6 Hz, CH2), 3.89 (2H, t, J = 6.3 Hz, CH2), 7.23 (1H, m, Ar), 8.13 (1H, dd, J = 8.7, 2.7 Hz, Ar), 9.11 (1H, d, J = 2.7 Hz, Ar); 13C-NMR (75 MHz, CDCl3) δ: 21.7, 30.0 (3C), 45.1, 45.5, 54.5, 124.1, 124.3, 125.3, 128.5, 135.6, 137.1, 145.8, 146.1; HRMS (FAB): m/z calcd for C15H19N4O2S [M + H]+ 319.1229; found: 319.1232.

Compound 26e. TFA (3.2 mL) was added to compound 23e (100 mg, 0.314 mmol). After being stirred under reflux for 1.5 h, the mixture was added dropwise to Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3, brine, and dried over Na2SO4. After concentration, the residue was purified by preparative TLC over aluminum oxide with n-hexane–EtOAc (7:3) to give the title compound 26e as orange solid (15.9 mg, 19.3 %): mp 167.9 °C; IR (neat) cm−1: 1614 (C=N), 1576 (NO2), 1557 (C=N), 1519 (NO2); 1H-NMR (300 MHz, CDCl3) δ: 1.97–2.04 (2H, m, CH2), 3.74 (2H, t, J = 5.6 Hz, CH2), 4.05 (2H, t, J = 6.2 Hz, CH2), 7.19 (1H, d, J = 9.0 Hz, Ar), 7.38 (1H, br s, NH), 8.17 (1H, dd, J = 8.7, 2.7 Hz, Ar), 9.13 (1H, d, J = 2.7 Hz, Ar); 13C-NMR (75 MHz, CDCl3) δ: 20.8, 44.1, 44.9, 124.5 (2C), 124.8, 127.6, 136.7, 144.5, 146.3, 151.0; HRMS (FAB): m/z calcd for C11H11N4O2S [M + H]+ 263.0603; found: 263.0606. The purity of the compound was 75 % by HPLC.

Synthesis of 3,4-Dihydro-10-methoxy-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (26f)

N -( tert -Butyl)-3,4-dihydro-10-methoxy-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (23f). To a mixture of N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (500.3 mg, 1.42 mmol) and NaOMe (767 mg, 14.2 mmol, 28 % solution in MeOH,) in DMF (2.5 mL) was added CuBr (20.4 mg, 0.142 mmol). The mixture was stirred at 110 °C for 2.5 h. The whole was extracted with CH2Cl2. The extract was washed with brine, and dried over Na2SO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (6:4 to 4:6) to give the titlecompound 23f as colorless solid (171.5 mg, 39.8 %): mp 87.1 °C; IR (neat) cm−1: 1588 (C=N); 1H-NMR (300 MHz, CDCl3) δ: 1.38 (9H, s, 3 × CH3), 1.87–1.95 (2H, m, CH2), 3.62 (2H, t, J = 5.6 Hz, CH2), 3.86 (5H, m, CH3, CH2), 6.92 (1H, dd, J = 8.7, 2.7 Hz, Ar), 7.00 (1H, d, J = 8.4 Hz, Ar), 7.75 (1H, d, J = 3.3 Hz, Ar); 13C-NMR (75 MHz, CDCl3) δ: 21.9, 29.9 (3C), 45.1, 45.5, 54.1, 55.6, 111.3, 118.9, 120.2, 125.7, 128.9, 138.8, 148.1, 158.1; Anal. calcd for C16H21N3OS: C, 63.33; H, 6.98; N, 13.85. Found: C, 63.04; H, 6.97; N, 13.68.

Compound 26f. TFA (0.88 mL) was added to compound 23f (26.7 mg, 0.088 mmol). After being stirred under reflux for 3 h, the mixture was added dropwise to Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3, brine, and dried over Na2SO4. After concentration, the residue was purified by preparative TLC over aluminum oxide with n-hexane–EtOAc (7:3) to give the title compound 26f as colorless solid (9.6 mg, 44 %): mp 89.0 °C; IR (neat) cm−1: 1614 (C=N), 1562 (C=N); 1H-NMR (300 MHz, CDCl3) δ: 1.93–2.00 (2H, m, CH2), 3.69 (2H, t, J = 5.4 Hz, CH2), 3.85 (3H, s, CH3), 4.02 (2H, t, J = 6.2 Hz, CH2), 6.92–6.98 (2H, m, Ar), 7.15 (1H, br s, NH), 7.78 (1H, s, Ar); 13C-NMR (75 MHz, CDCl3) δ: 21.0, 43.9, 44.9, 55.6, 111.9, 119.3, 119.9, 124.8, 127.9, 146.7, 153.9, 158.3; Anal. calcd for C12H13N3OS: C, 58.28; H, 5.30; N, 16.99. Found: C, 58.24; H, 5.36; N, 16.46. The purity of the compound was 92 % by HPLC.

Synthesis of 3,4-Dihydro-10-methyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (26g)

2-(2-Fluoro-5-methylphenyl)-1,4,5,6-tetrahydropyrimidine (19g). 2-Fluoro-5-methylbenzaldehyde 16g (3.0 g, 21.7 mmol) was subjected to the general procedure as described for 18j to give the title 19g as colorless crystals (3.1 g, 75 %): mp 119–121 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1626 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.84–1.89 (2H, m, CH2), 2.31 (3H, s, CH3), 3.51 (4H, t, J = 5.7 Hz, 2 × CH2), 5.01 (1H, s, NH), 6.92 (1H, dd, J = 11.7, 8.3 Hz, Ar), 7.09–7.12 (1H, m, Ar), 7.63 (1H, dd, J = 7.4, 2.3 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.5, 20.7, 42.3 (2C), 115.6 (d, J = 24.0 Hz), 123.7 (d, J = 12.0 Hz), 130.6 (d, J = 3.6 Hz), 131.3 (d, J = 9.6 Hz), 133.9 (d, J = 3.6 Hz), 151.7, 158.4 (d, J = 244.7 Hz); 19F-NMR (500 MHz, CDCl3) δ: −122.4; HRMS (FAB): m/z calcd for C11H14FN2 [M + H]+ 193.1141; found: 193.1140.

N -( tert -Butyl)-3,4-dihydro-10-methyl-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (23g). To a mixture of compound 19g (0.50 g, 2.6 mmol) and KOt-Bu (0.58 g, 5.2 mmol) in DMAc (8.7 mL) was added tert-butylisothiocyanate (0.66 mL, 5.2 mmol) under an Ar atmosphere. After being stirred at 80 °C for 3 h, the whole was extracted with EtOAc. The whole was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (1:1) to give the title compound 23g as colorless solid (0.21 g, 28 %): mp 76–77 °C (from n-hexane); IR (neat) cm−1: 1597 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.38 (9H, s, 3 × CH3), 1.88–1.94 (2H, m, CH2), 2.33 (3H, s, CH3), 3.62 (2H, t, J = 5.6 Hz, CH2), 3.87 (2H, t, J = 6.2 Hz, CH2), 7.00 (1H, d, J = 8.0 Hz, Ar), 7.13 (1H, dd, J = 8.0, 1.3 Hz, Ar), 8.01 (1H, d, J = 1.3 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 22.0, 29.9 (3C), 45.1, 45.4, 54.1, 124.4, 125.7, 127.6, 128.6, 131.1, 135.9, 138.7, 148.2; HRMS (FAB): m/z calcd for C16H22N3S [M + H]+ 288.1534; found: 288.1535.

Compound 26g. Using the general procedure as described for 25a, compound 23g (200 mg, 0.7 mmol) was allowed to react for 1 h with TFA (3.0 mL) and MS4Å (450 mg). Purification by preparative TLC over aluminum oxide with n-hexane–EtOAc (9:1) gave the title compound 26g as colorless solid (150 mg, 92 %): mp 116 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1623 (C=N), 1556 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.94–2.00 (2H, m, CH2), 2.34 (3H, s, CH3), 3.69 (2H, t, J = 5.6 Hz, CH2), 4.01 (2H, t, J = 6.1 Hz, CH2), 6.94 (1H, d, J = 8.0 Hz, Ar), 7.15–7.17 (2H, m, Ar, NH), 8.04 (1H, s, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 21.1, 43.8, 44.9, 123.5, 125.4, 126.5, 129.0, 131.6, 136.3, 146.9, 153.7; HRMS (FAB): m/z calcd for C12H14N3S [M + H]+ 232.0908; found: 232.0913.

Synthesis of 10-Bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (26k)

2-(5-Bromo-2-fluorophenyl)-1,4,5,6-tetrahydropyrimidine (19k). 5-Bromo-2-fluorobenzaldehyde 16k (1.02 g, 5.0 mmol) was subjected to the general procedure as described for 18j to give the title compound 19k as colorless crystals (1.02 g, 79 %): mp 121–122 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1623 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.83–1.89 (2H, m, CH2), 3.50 (4H, t, J = 5.7 Hz, 2 × CH2), 5.28 (1H, br s, NH), 6.94 (1H, dd, J = 11.1, 8.8 Hz, Ar), 7.42 (1H, ddd, J = 8.8, 4.4, 2.7 Hz, Ar), 7.97 (1H, dd, J = 6.8, 2.7 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 20.6, 42.1 (2C), 117.1 (d, J = 3.3 Hz), 117.7 (d, J = 25.7 Hz), 126.2 (d, J = 13.2 Hz), 133.3 (d, J = 3.3 Hz), 133.6 (d, J = 9.1 Hz), 150.3, 159.1 (d, J = 247.5 Hz); 19F-NMR (500 MHz, CDCl3) δ: −119.5; Anal. calcd for C10H10BrFN2: C, 46.72; H, 3.92; N, 10.90. Found: C, 46.59; H, 3.87; N, 10.89.

10-Bromo- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (23k). Using the general procedure as described for 22e, compound 19k (257.1 mg, 1.00 mmol) was allowed to react at rt overnight. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 23k as colorless solid (111.6 mg, 32 %): mp 93–94 °C (from n-hexane); IR (neat) cm−1: 1599 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.38 (9H, s, 3 × CH3), 1.88-1.93 (2H, m, CH2), 3.62 (2H, t, J = 5.6 Hz, CH2), 3.86 (2H, t, J = 6.1 Hz, CH2), 6.97 (1H, d, J = 8.5 Hz, Ar), 7.41 (1H, dd, J = 8.5, 2.2 Hz, Ar), 8.36 (1H, d, J = 2.2 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 29.9 (3C), 45.1, 45.4, 54.2, 119.7, 125.9, 128.1, 129.3, 131.2, 133.0, 137.4, 146.7; Anal. calcd for C15H18BrN3S: C, 51.14; H, 5.15; N, 11.93. Found: C, 51.09; H, 4.98; N, 11.89.

Compound 26k. Using the general procedure as described for 25a, compound 23k (52.8 mg, 0.15 mmol) was allowed to react for 2 h with TFA (1.5 mL) and MS4Å (225 mg). Purification by flash chromatography over silica gel with n-hexane–EtOAc (2:1) gave the title compound 26k as colorless crystals (39.7 mg, 89 %): mp 106–107 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1621 (C=N), 1571 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.94-1.99 (2H, m, CH2), 3.69 (2H, t, J = 5.4 Hz, CH2), 4.01 (2H, t, J = 6.3 Hz, CH2), 6.91 (1H, d, J = 8.6 Hz, Ar), 7.20 (1H, br s, NH), 7.44 (1H, dd, J = 8.6, 2.3 Hz, Ar), 8.39 (1H, d, J = 2.3 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.9, 43.8, 44.9, 120.0, 125.0, 127.8, 128.3, 131.6, 133.5, 145.4, 152.5; Anal. calcd for C11H10BrN3S: C, 44.61; H, 3.40; N, 14.19. Found: C, 44.51; H, 3.66; N, 14.06.

Synthesis of 3,4-Dihydro-10-phenyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (26l)

N -( tert -Butyl)-3,4-dihydro-10-phenyl-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (23l). Using the general procedure as described for 22l, 10-bromo-N-(tert-butyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 23k (52.8 mg, 0.15 mmol) was allowed to react for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 23l as colorless solid (32.6 mg, 62 %): mp 101–103 °C (from n-hexane); IR (neat) cm−1: 1594 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.40 (9H, s, 3 × CH3), 1.90–1.95 (2H, m, CH2), 3.64 (2H, t, J = 5.4 Hz, CH2), 3.89 (2H, t, J = 6.0 Hz, CH2), 7.18 (1H, d, J = 8.0 Hz, Ar), 7.32 (1H, t, J = 7.4 Hz, Ar), 7.41 (2H, t, J = 7.4 Hz, Ar), 7.55 (1H, dd, J = 8.0, 2.0 Hz, Ar), 7.61 (2H, d, J = 7.4 Hz, Ar), 8.47 (1H, d, J = 2.0 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.5, 54.2, 125.0, 126.9, 127.0 (2C), 127.4, 127.9, 128.1, 128.7 (2C), 128.7, 138.2, 139.1, 140.0, 147.9; HRMS (FAB): m/z calcd for C21H24N3S [M + H]+ 350.1691; found:350.1683.

Compound 26l. Using the general procedure as described for 25a, compound 23l (13.1 mg, 0.037 mmol) was allowed to react for 2 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1) gave the title compound 26l as colorless solid (8.4 mg, 77 %): mp 82 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1621 (C=N), 1550 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.95-2.01 (2H, m, CH2), 3.71 (2H, t, J = 5.6 Hz, CH2), 4.03 (2H, t, J = 6.2 Hz, CH2), 7.10–7.44 (5H, m, Ar), 7.56–7.64 (3H, m, Ar), 8.50 (1H, d, J = 2.2 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.1, 43.9, 45.0, 124.0, 126.9, 127.1 (2C), 127.3, 127.6, 128.8 (2C), 129.2, 139.4, 139.8, 146.6, 152.1, 153.3; Anal. calcd for C17H15N3S: C, 69.59; H, 5.15; N, 14.32. Found: C, 69.61; H, 5.13; N, 14.22.

Synthesis of 3,4-Dihydro-10-vinyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (26m)

N -( tert -Butyl)-3,4-dihydro-10-vinyl-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (23m). Using the general procedure as described for 22l, 10-bromo-N-(tert-butyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 23k (52.8 mg, 0.15 mmol) was allowed to react with vinylboronic acid pinacol ester (0.031 mL, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 23m as a colorless oil (30.5 mg, 68 %): IR (neat) cm−1: 1595 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.38 (9H, s, 3 × CH3), 1.89–1.94 (2H, m, CH2), 3.63 (2H, t, J = 5.4 Hz, CH2), 3.87 (2H, t, J = 6.0 Hz, CH2), 5.24 (1H, d, J = 11.0 Hz, CH), 5.77 (1H, d, J = 17.6 Hz, CH), 6.69 (1H, dd, J = 17.6, 11.0 Hz, CH), 7.07 (1H, d, J = 8.3 Hz, Ar), 7.40 (1H, dd, J = 8.3, 2.0 Hz, Ar), 8.20 (1H, d, J = 2.0 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.1, 114.1, 124.7, 126.6, 127.4, 127.8, 128.2, 135.7, 135.9, 138.2, 147.9; HRMS (FAB): m/z calcd for C17H22N3S [M + H]+ 300.1534; found: 300.1532.

Compound 26m. Using the general procedure as described for 25a, compound 23m (7.3 mg, 0.024 mmol) was allowed to react for 1 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1) gave the title compound 26m as colorless solid (3.7 mg, 62 %): mp 69–70 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1622 (C=N), 1550 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.95-2.01 (2H, m, CH2), 3.70 (2H, t, J = 5.7 Hz, CH2), 4.02 (2H, t, J = 6.2 Hz, CH2), 5.27 (1H, dd, J = 10.7, 0.6 Hz, CH), 5.79 (1H, dd, J = 17.7, 0.6 Hz, CH), 6.69 (1H, dd, J = 17.7, 10.7 Hz, CH), 7.00 (1H, d, J = 8.3 Hz, Ar), 7.19 (1H, br s, NH), 7.42 (1H, dd, J = 8.3, 2.0 Hz, Ar), 8.23 (1H, d, J = 2.0 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 114.5, 123.8, 126.8, 126.9, 127.8, 127.9, 135.6, 135.9, 146.5, 153.2; HRMS (FAB): m/z calcd for C13H14N3S [M + H]+ 244.0908; found: 244.0902.

Synthesis of 10-(4-Benzoylphenyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (26q)

10-(4-Benzoylphenyl)- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (23q). Using the general procedure as described for 22l, 10-bromo-N-(tert-butyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 23k (52.8 mg, 0.15 mmol) was allowed to react with 4-benzoylphenylboronic acid (40.7 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (8:2) gave the title compound 23q as colorless solid (65.1 mg, 96 %): mp 192–193 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1654 (C=O), 1592 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.41 (9H, s, 3 × CH3), 1.91–1.96 (2H, m, CH2), 3.65 (2H, t, J = 5.5 Hz, CH2), 3.90 (2H, t, J = 6.1 Hz, CH2), 7.39 (1H, d, J = 1.7 Hz, Ar), 7.46–7.52 (3H, m, Ar), 7.58–7.62 (1H, m, Ar), 7.70 (2H, d, J = 8.5 Hz, Ar), 7.82 (2H, dd, J = 8.3, 1.2 Hz, Ar), 7.88 (2H, d, J = 8.5 Hz, Ar), 8.30 (1H, d, J = 8.5 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 123.0, 124.8, 126.9 (2C), 127.3, 128.3 (2C), 129.1, 129.8, 130.0 (2C), 130.7 (2C), 132.5, 136.9, 137.6, 137.9, 141.6, 143.3, 147.5, 196.1; HRMS (FAB): m/z calcd for C28H28N3OS [M + H]+ 454.1953; found: 454.1952.

Compound 26q. Using the general procedure as described for 25a, compound 23q (36.2 mg, 0.08 mmol) was allowed to react for 1 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 26q as colorless solid (23.4 mg, 74 %): mp 163–165 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1654 (C=O), 1622 (C=N), 1561 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.97–2.03 (2H, m, CH2), 3.72 (2H, t, J = 5.6 Hz, CH2), 4.05 (2H, t, J = 6.2 Hz, CH2), 7.15 (1H, d, J = 8.0 Hz, Ar), 7.48–7.52 (2H, m, Ar), 7.58–7.64 (2H, m, Ar), 7.73 (2H, d, J = 8.5 Hz, Ar), 7.82 (2H, dd, J = 8.2, 1.3 Hz, Ar), 7.88 (2H, d, J = 8.5 Hz, Ar), 8.57 (1H, d, J = 2.0 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.9, 45.0, 124.3, 126.7 (2C), 127.2, 127.6, 128.3 (2C), 128.8, 129.2, 130.0 (2C), 130.7 (2C), 132.4, 136.5, 137.7, 138.0, 143.7, 146.3, 152.9, 196.1; HRMS (FAB): m/z calcd for C24H20N3OS [M + H]+ 398.1327; found: 398.1327.

Synthesis of 11-Fluoro-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (27i)

2-(2,6-Difluorophenyl)-1,4,5,6-tetrahydropyrimidine (20i). 2,6-Difluorobenzaldehyde 17i (1.00 g, 7.04 mmol) was subjected to the general procedure as described for 18j to give the title compound 20i as colorless crystals (1.08 g, 78 %): mp 165–166 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.85–1.90 (2H, m, CH2), 3.47 (4H, t, J = 5.7 Hz, 2 × CH2), 4.77 (1H, br s, NH), 6.86–6.91 (2H, m, Ar), 7.24–7.30 (1H, m, Ar); 13C-NMR (100 MHz, CDCl3) δ: 20.5, 42.2 (2C), 111.4–111.6 (m, 2C), 115.9 (t, J = 20.3 Hz), 130.1 (t, J = 9.9 Hz), 146.8, 160.3 (dd, J = 250.3, 7.0 Hz, 2C). 19F-NMR (500 MHz, CDCl3) δ: −114.4; Anal. calcd for C10H10F2N2: C, 61.22; H, 5.14; N, 14.28. Found: C, 61.23; H, 5.13; N, 14.26.

N -( tert -Butyl)-11-fluoro-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (24i). Using the general procedure as described for 22e, compound 20i (196.2 mg, 1.0 mmol) was allowed to react at rt overnight. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 24i as colorless solid (212.6 mg, 73 %): mp 81 °C (from n-hexane); IR (neat) cm−1: 1592 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.37 (9H, s, 3 × CH3), 1.90–1.95 (2H, m, CH2), 3.66 (2H, t, J = 5.7 Hz, CH2), 3.80 (2H, t, J = 6.6 Hz, CH2), 6.94–6.99 (2H, m, Ar), 7.23–7.26 (1H, m, Ar); 13C-NMR (125 MHz, CDCl3) δ: 22.5, 30.1 (3C), 45.3, 45.5, 54.2, 115.0 (d, J = 24.0 Hz), 118.7, 120.9 (d, J = 3.6 Hz), 130.6 (d, J = 10.8 Hz), 131.9, 137.6, 146.1 (d, J = 8.4 Hz), 160.2 (d, J = 260.3 Hz); 19F-NMR (500 MHz, CDCl3) δ: −110.8; HRMS (FAB): m/z calcd for C15H19FN3S [M + H]+ 292.1284; found: 292.1288.

Compound 27i. Using the general procedure as described for 25a, compound 24i (58.3 mg, 0.20 mmol) was allowed to react for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1) gave the title compound 27i as colorless solid (42.3 mg, 90 %): mp 142.5 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1624 (C=N), 1585 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.97–2.02 (2H, m, CH2), 3.73 (2H, t, J = 5.2 Hz, CH2), 3.94 (2H, t, J = 6.6 Hz, CH2), 6.91 (1H, d, J = 8.0 Hz, Ar), 6.97–7.01 (1H, m, Ar), 7.22 (1H, br s, NH), 7.27–7.31 (1H, m, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.7, 44.0, 45.5, 115.3 (d, J = 24.0 Hz), 117.4 (d, J = 8.4 Hz), 120.0 (d, J = 3.6 Hz), 131.2 (d, J = 9.6 Hz), 131.5, 144.8 (d, J = 9.6 Hz), 152.6 (d, J = 4.8 Hz), 160.5 (d, J = 261.5 Hz); 19F-NMR (500 MHz, CDCl3) δ: −110.0. Anal. calcd for C11H10FN3S: C, 56.15; H, 4.28; N, 17.86. Found: C, 56.05; H, 4.28; N, 17.71.

Synthesis of 8-Bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (27k)

2-(3-Bromo-2-fluorophenyl)-1,4,5,6-tetrahydropyrimidine (20k). 3-Bromo-2-fluorobenzaldehyde 17k (0.71 g, 3.5 mmol) was subjected to the general procedure as described for 18j to give the title compound 20k as colorless crystals (0.62 g, 69 %): mp 99 °C; IR (neat) cm−1: 1624 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.84–1.89 (2H, m, CH2), 3.50 (4H, t, J = 5.7 Hz, 2 × CH2), 5.13 (1H, br s, NH), 7.03 (1H, td, J = 8.0, 0.9 Hz, Ar), 7.54 (1H, ddd, J = 8.0, 6.4, 1.3 Hz, Ar), 7.69 (1H, ddd, J = 8.0, 6.5, 1.3 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 20.6, 42.1 (2C), 109.6 (d, J = 22.3 Hz), 125.1 (d, J = 4.1 Hz), 126.3 (d, J = 13.2 Hz), 129.8 (d, J = 3.3 Hz), 134.3, 150.8, 156.3 (d, J = 248.3 Hz); 19F-NMR (500 MHz, CDCl3) δ: −110.7; Anal. calcd for C10H10BrFN2: C, 46.72; H, 3.92; N, 10.90. Found: C, 46.64; H, 4.10; N, 10.93.

8-Bromo- N -( tert H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (24k). Using the general procedure as described for 22e, compound 20k (257.1 mg, 1.00 mmol) was allowed to react at rt overnight. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 24k as colorless solid (335.3 mg, 95 %): mp 89 °C (from n-hexane); IR (neat) cm−1: 1595 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.42 (9H, s, 3 × CH3), 1.87–1.92 (2H, m, CH2), 3.62 (2H, t, J = 5.4 Hz, CH2), 3.86 (2H, t, J = 6.0 Hz, CH2), 7.07 (1H, dd, J = 8.0, 7.4 Hz, Ar), 7.55 (1H, d, J = 7.4 Hz, Ar), 8.19 (1H, d, J = 8.0 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.7, 30.1 (3C), 45.3, 45.3, 54.3, 118.6, 126.5, 127.5, 129.9, 130.7, 133.8, 137.4, 147.5; Anal. calcd for C15H18BrN3S: C, 51.14; H, 5.15; N, 11.93. Found: C, 50.89; H, 5.06; N, 11.83.

Compound 27k. Using the general procedure as described for 25a, compound 24k (52.8 mg, 0.15 mmol) was allowed to react for 2 h with TFA (1.5 mL) and MS4Å (225 mg). Purification by flash chromatography over silica gel with n-hexane–EtOAc (2:1) gave the title compound 27k as colorless solid (31.6 mg, 71 %): mp 138–139 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1567 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.94–1.98 (2H, m, CH2), 3.69 (2H, t, J = 5.7 Hz, CH2), 4.02 (2H, t, J = 6.0 Hz, CH2), 7.10 (1H, dd, J = 8.3, 7.7 Hz, Ar), 7.33 (1H, br s, NH), 7.56 (1H, dd, J = 7.7, 1.4 Hz, Ar), 8.23 (1H, dd, J = 8.3, 1.4 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.8, 43.7, 45.0, 117.6, 126.8, 127.9, 128.8, 130.5, 134.1, 146.2, 152.7; Anal. calcd for C11H10BrN3S: C, 44.61; H, 3.40; N, 14.19. Found: C, 44.36; H, 3.64; N, 13.96.

Synthesis of 3,4-Dihydro-2H,6H-pyrimido[1,2-c]naphtho[2,3-e][1,3]thiazin-6-imine (27r)

2-(3-Fluoronaphthalen-2-yl)-1,4,5,6-tetrahydropyrimidine (20r). 1-Fluoro-2-naphthaldehyde 17r (0.96 g, 5.52 mmol) was subjected to the general procedure as described for 18j to give the title compound 20r as pale yellow crystals (0.85 g, 67 %): mp 128–130 °C (from CHCl3–EtOAc–Et2O); IR (neat) cm−1: 1619 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.86–1.91 (2H, m, CH2), 3.52 (4H, t, J = 5.7 Hz, 2 × CH2), 5.21 (1H, br s, NH), 7.41–7.44 (2H, m, Ar), 7.49 (1H, t, J = 7.4 Hz, Ar), 7.73 (1H, d, J = 8.6 Hz, Ar), 7.83 (1H, d, J = 8.6 Hz, Ar), 8.27 (1H, d, J = 8.0 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.5, 42.2 (2C), 111.7 (d, J = 22.8 Hz), 124.5 (d, J = 16.8 Hz), 125.6 (d, J = 2.4 Hz), 126.7 (d, J = 4.8 Hz), 127.5, 128.6, 130.1, 130.9 (d, J = 4.8 Hz), 134.2 (d, J = 9.6 Hz), 151.9, 157.8 (d, J = 247.1 Hz); 19F-NMR (500 MHz, CDCl3) δ: −119.8; HRMS (FAB) m/z calcd for C14H14FN2 [M + H]+ 229.1141; found: 229.1143.

N -( tert -Butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ]naphtho[2,3- e ][1,3]thiazin-6-imine (24r). Using the general procedure as described for 22e, compound 20r (228.3 mg, 1.00 mmol) was allowed to react at rt overnight. Purification by flash chromatography over silica gel with n-hexane–EtOAc (1:1) gave the title compound 24r as colorless solid (284.8 mg, 88 %): mp 82.5–83.5 °C, IR (neat) cm−1: 1594 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.42 (9H, s, 3 × CH3), 1.92–1.98 (2H, m, CH2), 3.69 (2H, t, J = 5.6 Hz, CH2), 3.91 (2H, t, J = 6.2 Hz, CH2), 7.38–7.43 (1H, m, Ar), 7.45–7.49 (1H, m, Ar), 7.60 (1H, s, Ar), 7.69 (1H, d, J = 7.8 Hz, Ar), 7.87 (1H, d, J = 8.0 Hz, Ar), 8.70 (1H, s, Ar); 13C-NMR (100 MHz, CDCl3) δ: 22.0, 30.1 (3C), 45.3, 45.5, 54.3, 122.5, 125.8, 125.9, 126.3, 126.5, 127.8, 128.5, 129.2, 131.7, 133.9, 138.4, 148.5; HRMS (FAB) m/z calcd for C19H22N3S [M + H]+ 324.1534; found: 324.1526.

Compound 27r. Using the general procedure as described for 25a, compound 24r (64.7 mg, 0.2 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (4:1) gave the title compound 27r as colorless solid (36.6 mg, 68 %): mp 180–181 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1627 (C=N), 1572 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.98–2.04 (2H, m, CH2), 3.75 (2H, t, J = 5.5 Hz, CH2), 4.06 (2H, t, J = 6.2 Hz, CH2), 7.40–7.51 (3H, m, Ar), 7.68 (1H, d, J = 8.3 Hz, Ar), 7.87 (1H, d, J = 8.3 Hz, Ar), 8.74 (1H, s, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.1, 43.9, 45.1, 121.6, 125.0, 125.4, 126.1, 126.3, 128.1, 129.2, 129.2, 131.6, 133.9, 147.1, 153.4; HRMS (FAB) m/z calcd for C15H14N3S [M + H]+ 268.0908; found: 268.0909.

Synthesis of 3,4-Dihydro-2H,6H-pyrimido[1,2-c]pyrido[3,2-e][1,3]thiazin-6-imine (27s)

Using general procedure as described for 25f, reaction of 2-(2-bromopyridin-3-yl)-1,4,5,6-tetrahydropyrimidine 21s (58.8 mg, 0.25 mmol) and purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 27s as colorless solid (17.4 mg, 32 %): mp 181–183 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1624 (C=N), 1582 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.96–2.01 (2H, m, CH2), 3.70 (2H, t, J = 5.7 Hz, CH2), 4.05 (2H, t, J = 6.3 Hz, CH2), 7.17 (1H, dd, J = 8.0, 4.6 Hz, Ar), 7.39 (1H, br s, NH), 8.46–8.50 (2H, m, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.8, 43.8, 45.2, 121.4, 123.7, 136.3, 145.3, 151.2, 151.3, 153.5; HRMS (FAB): m/z calcd for C10H11N4S [M + H]+ 219.0704; found: 219.0703.

Synthesis of 2,3-Dihydronaphtho[2,1-e]pyrimido[1,2-c][1,3]thiazin-12(1H)-imine (27t)

2,3-Dihydronaphtho[2,1-e]pyrimido[1,2-c][1,3]thiazine-12(1H)-thione 21t (71.1 mg, 0.25 mmol) was subjected to the general procedure as described for 25f to give the title compound 27t as colorless solid (42.3 mg, 63 %): mp 157 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1615 (C=N), 1572 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.99–2.03 (2H, m, CH2), 3.75 (2H, t, J = 5.4 Hz, CH2), 4.07 (2H, t, J = 6.0 Hz, CH2), 7.33 (1H, br s, NH), 7.53–7.57 (2H, m, Ar), 7.66 (1H, d, J = 8.6 Hz, Ar), 7.80–7.90 (2H, m, Ar), 8.30 (1H, d, J = 9.2 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.9, 43.7, 45.1, 123.2, 124.0, 125.1, 125.9, 126.7, 126.7, 127.5, 127.8, 128.5, 133.9, 147.1, 152.7; HRMS (FAB): m/z calcd for C15H14N3S [M + H]+ 268.0908; found: 268.0906.

Synthesis of 3,4-Dihydro-2H,6H-pyrimido[1,2-c]thieno[2,3-e][1,3]thiazin-6-imine (27u)

2-(3-Bromothiophen-2-yl)-1,4,5,6-tetrahydropyrimidine (20u). 3-Bromothiophene-2-carbaldehyde 17u (1.29 g, 6.75 mmol) was subjected to the general procedure as described for 18j to give the title compound 20u as pale yellow crystals (1.11 g, 67 %): mp 61–63 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1611 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.83–1.88 (2H, m, CH2), 3.48 (4H, t, J = 5.9 Hz, 2 × CH2), 6.07 (1H, br s, NH), 6.92 (1H, d, J = 5.4 Hz, Ar), 7.24 (1H, d, J = 5.4 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 20.5, 42.0 (2C), 105.8, 127.3, 131.4, 135.6, 149.3; HRMS (FAB): m/z calcd for C8H10BrN2S [M + H]+ 244.9748; found: 244.9742.

3,4-Dihydro-2 H, 6 H -pyrimido[1,2- c ]thieno[2,3- e ][1,3]thiazin-6-thione (21u). To a mixture of 20u (122.6 mg, 0.50 mmol) and NaH (40.0 mg, 1.0 mmol; 60 % oil suspension) in DMF (1.7 mL) was added CS2 (0.060 mL, 1.0 mmol) under an Ar atmosphere. After being stirred at 80 °C for 12 h, the mixture was concentrated. The residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (8:2) to give the title compound 21u as pale yellow solid (80.5 mg, 67 %): mp 167 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1624 (C=N); 13C-NMR (400 MHz, CDCl3) δ: 2.04–2.10 (2H, m, CH2), 3.68 (2H, t, J = 5.5 Hz, CH2), 4.42 (2H, t, J = 6.1 Hz, CH2), 6.76 (1H, d, J = 5.4 Hz, Ar), 7.49 (1H, d, J = 5.4 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.5, 45.0, 48.5, 122.3, 128.4, 130.8, 131.0, 141.7, 189.7; HRMS (FAB): m/z calcd for C9H9N2S3 [M + H]+ 240.9928; found: 240.9936.

Compound 27u. Compound 21u (60.1 mg, 0.25 mmol) was subjected to general procedure as described for 25f to give the title compound 27u as colorless solid (19.4 mg, 35 %): mp 100–101 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1616 (C=N), 1567 (C=N); 13C-NMR (400 MHz, CDCl3) δ: 1.99–2.05 (2H, m, CH2), 3.62 (2H, t, J = 5.6 Hz, CH2), 3.99 (2H, t, J = 6.1 Hz, CH2), 6.74 (1H, d, J = 5.4 Hz, Ar), 7.28 (1H, br s, NH), 7.41 (1H, d, J = 5.4 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.2, 43.5, 44.5, 123.3, 125.9, 127.0, 129.9, 143.7, 153.7; Anal. calcd for C9H9N3S2: C, 48.40; H, 4.06; N, 18.82. Found: C, 48.38; H, 3.98; N, 18.75.

Synthesis of 3,4-Dihydro-9-(4-methoxycarbonylphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31a)

N -( tert -Butyl)-3,4-dihydro-9-(4-methoxycarbonylphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29a). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-(methoxycarbonyl)phenylboronic acid (32.4 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29a as colorless solid (47.3 mg, 77 %): mp 201–202 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1719 (C=O), 1593 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.90–1.96 (m, 2H, CH2), 3.65 (t, J = 5.5 Hz, 2H, CH2), 3.89 (t, J = 6.1 Hz, 2H, CH2), 3.94 (s, 3H, CH3), 7.36 (d, J = 1.7 Hz, 1H, Ar), 7.44 (dd, J = 8.5, 1.7 Hz, 1H, Ar), 7.65 (d, J = 8.2 Hz, 2H, Ar), 8.10 (d, J = 8.2 Hz, 2H, Ar), 8.28 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.2, 45.4, 52.1, 54.2, 123.0, 124.8, 127.0 (2C), 127.3, 129.1, 129.6, 129.8, 130.2 (2C), 138.0, 141.7, 143.8, 147.5, 166.8; HRMS (FAB): m/z calcd for C23H26N3O2S [M + H]+ 408.1746; found: 408.1748.

Compound 31a. Using the general procedure as described for 25a, compound 29a (38.4 mg, 0.094 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 1:1) gave the title compound 31a as (27.3 mg, 83 %): mp 185–186 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1719 (C=O), 1619 (C=N), 1566 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.97–2.02 (m, 2H, CH2), 3.71 (t, J = 5.7 Hz, 2H, CH2), 3.94 (s, 3H, CH3), 4.04 (t, J = 6.0 Hz, 2H, CH2), 7.27 (d, J = 1.7 Hz, 1H, Ar), 7.46 (dd, J = 8.0, 1.7 Hz, 1H, Ar), 7.63 (d, J = 8.6 Hz, 2H, Ar), 8.10 (d, J = 8.6 Hz, 2H, Ar), 8.30 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 52.2, 122.0, 125.1, 126.2, 126.9 (2C), 129.5, 129.6, 129.7, 130.2 (2C), 142.1, 143.4, 146.2, 153.0, 166.7; HRMS (FAB): m/z calcd for C19H18N3O2S [M + H]+ 352.1120; found: 352.1119.

Synthesis of 9-(4-Cyanophenyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31b)

N -( tert -Butyl)-9-(4-cyanophenyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29b). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-cyanophenylboronic acid (26.4 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (8:2) gave the title compound 29b as colorless solid (53.9 mg, 96 %): mp 188–190 °C (from CHCl3–n-hexane); IR (neat) cm−1: 2226 (C ≡ N), 1593 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.91–1.96 (m, 2H, CH2), 3.65 (t, J = 5.5 Hz, 2H, CH2), 3.89 (t, J = 6.1 Hz, 2H, CH2), 7.33 (d, J = 1.8 Hz, 1H, Ar), 7.41 (dd, J = 8.3, 1.8 Hz, 1H, Ar), 7.68 (d, J = 8.1 Hz, 2H, Ar), 7.73 (d, J = 8.1 Hz, 2H, Ar), 8.29 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.2, 45.4, 54.2, 111.7, 118.6, 123.0, 124.7, 127.6 (2C), 127.8, 129.3, 130.1, 132.6 (2C), 137.6, 140.7, 143.9, 147.4; HRMS (FAB): m/z calcd for C22H23N4S [M + H]+ 375.1343; found: 375.1640.

Compound 31b. Using the general procedure as described for 25a, compound 29b (32.5 mg, 0.087 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (6:4) gave the title compound 31b as colorless solid (20.8 mg, 75 %): mp 210–211 °C (from CHCl3–n-hexane); IR (neat) cm−1: 2224 (C ≡ N), 1615 (C=N), 1577 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.97-2.02 (m, 2H, CH2), 3.71 (d, J = 5.4 Hz, 2H, CH2), 4.04 (t, J = 6.1 Hz, 2H, CH2), 7.24 (d, J = 1.7 Hz, 1H, Ar), 7.43 (dd, J = 8.3, 1.7 Hz, 1H, Ar), 7.67 (d, J = 8.3 Hz, 2H, Ar), 7.73 (d, J = 8.3 Hz, 2H, Ar), 8.32 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 111.9, 118.5, 122.0, 125.0, 126.7, 127.6 (2C), 129.7, 129.9, 132.7 (2C), 141.2, 143.5, 146.0, 152.8; HRMS (FAB): m/z calcd for C18H15N4S [M + H]+ 319.1017; found: 319.1015.

Synthesis of 3,4-Dihydro-9-(4-nitrophenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31c)

N -( tert -Butyl)-3,4-dihydro-9-(4-nitrophenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29c). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (352.3 mg, 1.0 mmol) was allowed to react with 4-nitrophenylboronic acid (200.3 mg, 1.2 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 2:1) gave the title compound 29c as colorless solid (366.9 mg, 93 %): mp 201–202 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1590 (C=N), 1514 (NO2); 1H-NMR (400 MHz, CDCl3) δ: 1.41 (s, 9H, 3 × CH3), 1.91–1.97 (m, 2H, CH2), 3.65 (t, J = 5.6 Hz, 2H, CH2), 3.90 (t, J = 6.1 Hz, 2H, CH2), 7.37 (d, J = 1.8 Hz, 1H, Ar), 7.44 (dd, J = 8.4, 1.8 Hz, 1H, Ar), 7.74 (d, J = 8.5 Hz, 2H, Ar), 8.28–8.32 (m, 3H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.2, 45.5, 54.3, 123.2, 124.1 (2C), 124.8, 127.8 (2C), 128.0, 129.3, 130.2, 137.5, 140.4, 145.8, 147.4, 147.5; HRMS (FAB): m/z calcd for C21H23N4O2S [M + H]+ 395.1542; found: 395.1539.

Compound 31c. Using the general procedure as described for 25a, compound 29c (77.0 mg, 0.075 mmol) was allowed to react for 4 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 31c as colorless solid (50.7 mg, 75 %): mp 207–209 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1615 (C=N), 1598 (NO2), 1573 (C=N), 1508 (NO2); 1H-NMR (500 MHz, CDCl3) δ: 1.98–2.02 (m, 2H, CH2), 3.72 (t, J = 5.7 Hz, 2H, CH2), 4.05 (t, J = 6.0 Hz, 2H, CH2), 7.27 (s, 1H, Ar), 7.46 (d, J = 8.0 Hz, 1H, Ar), 7.72 (d, J = 8.6 Hz, 2H, Ar), 8.30 (d, J = 8.6 Hz, 2H, Ar), 8.34 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 122.2, 124.2 (2C), 125.1, 126.9, 127.8 (2C), 129.7, 130.0, 140.8, 145.4, 146.0, 147.6, 152.7; HRMS (FAB): m/z calcd for C17H15N4O2S [M + H]+ 339.0916; found: 339.0912.

Synthesis of 3,4-Dihydro-9-(4-trifluoromethylphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31d)

N -( tert -Butyl)-3,4-dihydro-9-(4-trifluoromethylphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29d). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-(trifluoromethyl)phenylboronic acid (27.4 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29d as colorless solid (51.9 mg, 83 %): mp 177–179 °C (from n-hexane); IR (neat) cm−1: 1594 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.90–1.96 (m, 2H, CH2), 3.64 (t, J = 5.6 Hz, 2H, CH2), 3.89 (t, J = 6.1 Hz, 2H, CH2), 7.33 (d, J = 2.0 Hz, 1H, Ar), 7.41 (dd, J = 8.3, 2.0 Hz, 1H, Ar), 7.68 (s, 4H, Ar), 8.29 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.8, 29.9 (3C), 45.1, 45.4, 54.2, 122.9, 124.1 (q, J = 271.1 Hz), 124.8, 125.8 (q, J = 3.6 Hz, 2C), 127.3 (2C), 127.4, 129.2, 129.9, 130.0 (q, J = 32.8 Hz), 137.8, 141.3, 142.9, 147.5; 19F-NMR (500 MHz, CDCl3) δ: −63.0; HRMS (FAB): m/z calcd for C22H23F3N3S [M + H]+ 418.1565; found: 418.1563.

Compound 31d. Using the general procedure as described for 25a, compound 29d (41.2 mg, 1.0 mmol) was allowed to react for 4 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 31d as colorless solid (26.0 mg, 73 %): mp 142–143 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1619 (C=N), 1567 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.95–2.00 (m, 2H, CH2), 3.70 (t, J = 5.4 Hz, 2H, CH2), 4.03 (t, J = 6.0 Hz, 2H, CH2), 7.22 (s, 1H, Ar), 7.42 (d, J = 8.0 Hz, 1H, Ar), 7.64 (d, J = 8.0 Hz, 2H, Ar), 7.68 (d, J = 8.0 Hz, 2H, Ar), 8.30 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.9, 43.8, 44.9, 121.9, 124.0 (q, J = 272.2 Hz, 125.0, 125.7 (t, J = 3.6 Hz, 2C), 126.2, 127.2 (2C), 129.5, 129.6, 130.1 (q, J = 32.4 Hz), 141.7, 142.5, 146.1, 152.8; 19F-NMR (500 MHz, CDCl3) δ: −63.1; Anal. calcd for C18H14F3N3S: C, 59.82; H, 3.90; N, 11.63. Found: C, 59.56; H, 3.81; N, 11.48.

Synthesis of 9-(4-Aminocarbonylphenyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31e)

9-[(4-Aminocarbonyl)phenyl]- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29e). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-(aminocarbonyl)phenylboronic acid (29.7 mg, 0.18 mmol) in 1,4-dioxane for 1 h. Purification by preparative TLC over aluminum oxide with CHCl3–MeOH (95:5) gave the title compound 29e as colorless solid (31.2 mg, 53 %): mp 261–263 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1650 (C=O), 1592 (C=N); 1H-NMR (400 MHz, CDCl3–CD3OD) δ: 1.41 (s, 9H, 3 × CH3), 1.92–1.98 (m, 2H, CH2), 3.62 (t, J = 5.5 Hz, 2H, CH2), 3.90 (t, J = 6.1 Hz, 2H, CH2), 7.38 (d, J = 1.7 Hz, 1H, Ar), 7.47 (dd, J = 8.5, 1.7 Hz, 1H, Ar), 7.66 (d, J = 8.3 Hz, 2H, Ar), 7.92 (d, J = 8.3 Hz, 2H, Ar), 8.17 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3–CD3OD) δ: 21.6, 29.7 (3C), 44.7, 45.4, 54.2, 122.9, 124.8, 126.8, 126.9 (2C), 128.0 (2C), 128.8, 129.8, 132.6, 137.8, 141.8, 142.6, 148.7, 169.7; HRMS (FAB): m/z calcd for C22H25N4OS [M + H]+ 393.1749; found: 393.1744.

Compound 31e. TFA (17 mL) was added to a mixture of 29e (27.1 mg, 0.069 mmol) and MS4 Å (4.5 g, powder, activated by heating with Bunsen burner) in CHCl3 (3.0 mL) and MeOH (10 drops). After being stirred under reflux for 9 h, the mixture was concentrated. To a stirring mixture of this residue in CHCl3 was added dropwise Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by preparative TLC over aluminum oxide with EtOAc–MeOH (95:5) to give compound 31e as colorless solid (13.0 mg, 56 %): mp 222–223 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1666 (C=O), 1616 (C=N), 1556 (C=N); 1H-NMR (400 MHz, DMSO-d 6) δ: 1.83–1.89 (m, 2H, CH2), 3.59 (t, J = 5.1 Hz, 2H, CH2), 3.92 (t, J = 5.7 Hz, 2H, CH2), 7.40 (s, 1H, NH), 7.60–7.62 (m, 2H, Ar), 7.81 (d, J = 8.3 Hz, 2H, Ar), 7.96 (d, J = 8.3 Hz, 2H, Ar), 8.04 (s, 1H, NH), 8.24 (d, J = 8.3 Hz, 1H, Ar), 8.74 (s, 1H, NH); 13C-NMR (100 MHz, DMSO-d 6) δ: 20.7, 43.1, 44.4, 121.8, 124.3, 125.4, 126.5 (2C), 128.1 (2C), 129.0, 129.7, 133.8, 140.6, 141.1, 145.1, 149.5, 167.3; HRMS (FAB): m/z calcd for C18H17N4OS [M + H]+ 337.1123; found: 337.1118.

Synthesis of 3,4-Dihydro-9-(4-methoxyphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31f)

N -( tert -Butyl)-3,4-dihydro-9-(4-methoxyphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29f). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-methoxyphenylboronic acid (27.4 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29f as colorless solid (54.7 mg, 96 %): mp 199–200 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1592 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.89–1.95 (m, 2H, CH2), 3.63 (t, J = 5.5 Hz, 2H, CH2), 3.84 (s, 3H, CH3), 3.88 (t, J = 6.0 Hz, 2H, CH2), 6.96 (d, J = 8.5 Hz, 2H, Ar), 7.29 (d, J = 2.0 Hz, 1H, Ar), 7.38 (dd, J = 8.3, 2.0 Hz, 1H, Ar), 7.53 (d, J = 8.5 Hz, 2H, Ar), 8.22 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.1, 55.3, 114.3 (2C), 122.1, 124.4, 125.9, 128.1 (2C), 128.9, 129.4, 131.9, 138.4, 142.5, 147.8, 159.8; HRMS (FAB): m/z calcd for C22H26N3OS [M + H]+ 380.1797; found: 380.1801.

Compound 31f. Using the general procedure as described for 25a, compound 29f (28.4 mg, 0.075 mmol) was allowed to react for 2 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (3:1) gave the title compound 31f as colorless solid (20.0 mg, 82 %): mp 93–94 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1567 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.96-2.02 (m, 2H, CH2), 3.71 (t, J = 5.5 Hz, 2H, CH2), 3.85 (s, 3H, CH3), 4.04 (t, J = 6.2 Hz, 2H, CH2), 6.97 (d, J = 8.5 Hz, 2H, Ar), 7.20 (d, J = 1.7 Hz, 1H, Ar), 7.41 (dd, J = 8.3, 1.7 Hz, 1H, Ar), 7.52 (d, J = 8.5 Hz, 2H, Ar), 8.25 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 55.4, 114.4 (2C), 121.1, 124.7, 124.8, 128.1 (2C), 129.3, 129.3, 131.5, 143.1, 146.5, 153.5, 159.9; Anal. calcd for C18H17N3OS: C, 66.85; H, 5.30; N, 12.99. Found: C, 66.95; H, 5.50; N, 12.89.

Synthesis of 3,4-Dihydro-9-(4-methylthiophenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31g)

N -( tert -Butyl)-3,4-dihydro-9-(4-methylthiophenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29g). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-(methylthio)phenylboronic acid (30.2 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29g as colorless solid (50.6 mg, 85 %): mp 201–202 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1592 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.89–1.95 (m, 2H, CH2), 2.51 (s, 3H, CH3), 3.64 (t, J = 5.5 Hz, 2H, CH2), 3.88 (t, J = 6.1 Hz, 2H, CH2), 7.30–7.32 (m, 3H, Ar), 7.40 (dd, J = 8.4, 1.3 Hz, 1H, Ar), 7.51 (d, J = 8.3 Hz, 2H, Ar), 8.23 (d, J = 8.4 Hz, 1H, Ar; 13C-NMR (100 MHz, CDCl3) δ: 15.7, 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 122.3, 124.4, 126.4, 126.8 (2C), 127.3 (2C), 129.0, 129.6, 136.0, 138.2, 138.8, 142.2, 147.7; HRMS (FAB): m/z calcd for C22H26N3S2 [M + H]+ 396.1568; found: 396.1566.

Compound 31g. Using the general procedure as described for 25a, compound 29g (38.5 mg, 0.097 mmol) was allowed to react for 4 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 31g as colorless solid (18.4 mg, 56 %): mp 151–153 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1573 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.96–2.02 (m, 2H, CH2), 2.52 (s, 3H, CH3), 3.71 (t, J = 5.5 Hz, 2H, CH2), 4.04 (t, J = 6.1 Hz, 2H, CH2), 7.21 (d, J = 1.8 Hz, 1H, Ar), 7.31 (d, J = 8.3 Hz, 2H, Ar), 7.42 (dd, J = 8.5, 1.8 Hz, 1H, Ar), 7.49 (d, J = 8.3 Hz, 2H, Ar), 8.27 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 15.6, 21.0, 43.8, 44.9, 121.3, 124.7, 125.3, 126.7 (2C), 127.3 (2C), 129.4 (2C), 135.7, 139.2, 142.8, 146.5, 153.3; HRMS (FAB): m/z calcd for C18H18N3S2 [M + H]+ 340.0942; found: 340.0944.

Synthesis of 3,4-Dihydro-9-(4-trifluomethoxyphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31h)

N -( tert -Butyl)-3,4-dihydro-9-(4-trifluoromethoxyphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29h). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-(trifluoromethoxy)phenylboronic acid (37.1 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29h as colorless solid (59.7 mg, 92 %): mp 157 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1595 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.91-1.95 (m, 2H, CH2), 3.64 (t, J = 5.4 Hz, 2H, CH2), 3.89 (t, J = 6.0 Hz, 2H, CH2), 7.27–7.30 (m, 3H, Ar), 7.38 (dd, J = 8.0, 1.7 Hz, 1H, Ar), 7.59 (d, J = 8.6 Hz, 2H, Ar), 8.26 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.2, 45.5, 54.2, 120.5 (q, J = 257.4 Hz), 121.3 (2C), 122.8, 124.7, 127.0, 128.5 (2C), 129.1, 129.8, 138.0, 138.2, 141.5, 147.6, 149.2 (q, J = 1.7 Hz); 19F-NMR (500 MHz, CDCl3) δ: −58.3; HRMS (FAB): m/z calcd for C22H23F3N3OS [M + H]+ 434.1514; found: 434.1512.

Compound 31h. Using the general procedure as described for 25a, compound 29h (44.8 mg, 0.103 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1–7:3) gave the title compound 31h as colorless solid (17.3 mg, 45 %): mp 120 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1621 (C=N), 1571 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.98-2.02 (m, 2H, CH2), 3.72 (t, J = 5.7 Hz, 2H, CH2), 4.04 (t, J = 6.3 Hz, 2H, CH2), 7.22 (d, J = 1.7 Hz, 1H, Ar), 7.29 (d, J = 8.6 Hz, 2H, Ar), 7.41 (dd, J = 8.0, 1.7 Hz, 1H, Ar), 7.59 (d, J = 8.6 Hz, 2H, Ar), 8.29 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.9, 43.8, 44.9, 120.4 (q, J = 257.5 Hz), 121.3 (2C), 121.7, 124.9, 125.8, 128.4 (2C), 129.4, 129.5, 137.8, 141.9, 146.2, 149.2, 153.0; 19F-NMR (500 MHz, CDCl3) δ: −58.4; HRMS (FAB): m/z calcd for C18H15F3N3OS [M + H]+ 378.0888; found: 378.0888.

Synthesis of 3,4-Dihydro-9-(3-methoxycarbonylphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31i)

N-( -( tert -Butyl)-3,4-dihydro-9-(3-methoxycarbonylphenyl)-2 H, 6 H c ][1,3]benzothiazin-6-imine (29i). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-(methoxycarbonyl)phenylboronic acid (32.4 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29i as colorless solid (56.2 mg, 92 %): mp 116–117.5 °C (from n-hexane); IR (neat) cm−1: 1723 (C=O), 1592 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.41 (s, 9H, 3 × CH3), 1.91-1.96 (m, 2H, CH2), 3.65 (t, J = 5.4 Hz, 2H, CH2), 3.89 (t, J = 6.0 Hz, 2H, CH2), 3.95 (s, 3H, CH3), 7.37 (d, J = 1.7 Hz, 1H, Ar), 7.45 (dd, J = 8.6, 1.7 Hz, 1H, Ar), 7.51 (t, J = 8.0 Hz, 1H, Ar), 7.78 (d, J = 8.0 Hz, 1H, Ar), 8.04 (d, J = 8.0 Hz, 1H, Ar), 8.26-8.28 (m, 2H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 52.2, 54.2, 122.8, 124.7, 127.0, 128.0, 129.0, 129.1 (2C), 129.7, 130.8, 131.3, 138.1, 139.7, 141.7, 147.6, 166.8; HRMS (FAB): m/z calcd for C23H26N3O2S [M + H]+ 408.1746; found: 408.1741.

Compound 31i. Using the general procedure as described for 25a, compound 29i (34.2 mg, 0.084 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 31i as colorless solid (22.8 mg, 77 %): mp 131 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1721 (C=O), 1620 (C=N), 1568 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.97-2.02 (m, 2H, CH2), 3.72 (t, J = 5.4 Hz, 2H, CH2), 3.96 (s, 3H, CH3), 4.04 (t, J = 6.0 Hz, 2H, CH2), 7.28 (d, J = 1.4 Hz, 1H, Ar), 7.47 (dd, J = 8.6, 1.4 Hz, 1H, Ar), 7.52 (t, J = 7.7 Hz, 1H, Ar), 7.76 (d, J = 7.7 Hz, 1H, Ar), 8.05 (d, J = 7.7 Hz, 1H, Ar), 8.25 (s, 1H, Ar), 8.30 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 52.3, 121.8, 125.0, 125.9, 128.1, 129.0, 129.2, 129.5, 129.5, 130.9, 131.3, 139.4, 142.3, 146.3, 153.1, 166.7; Anal. calcd for C19H17N3O2S: C, 64.94; H, 4.88; N, 11.96. Found: C, 64.83; H, 4.79; N, 11.84.

Synthesis of 9-(3-Cyanophenyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31j)

N -( tert -Butyl)-9-(3-cyanophenyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29j). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-cyanophenylboronic acid (26.5 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (85:5) gave the title compound 29j as colorless solid (48.4 mg, 86 %): mp 165–167 °C (from CHCl3–n-hexane); IR (neat) cm−1: 2230 (C ≡ N), 1593 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.91-1.96 (m, 2H, CH2), 3.65 (t, J = 5.7 Hz, 2H, CH2), 3.89 (t, J = 6.3 Hz, 2H, CH2), 7.31 (d, J = 1.7 Hz, 1H, Ar), 7.38 (dd, J = 8.0, 1.7 Hz, 1H, Ar), 7.55 (t, J = 7.7 Hz, 1H, Ar), 7.65 (dt, J = 7.7, 1.7 Hz, 1H, Ar), 7.81 (dt, J = 7.7, 1.7 Hz, 1H, Ar), 7.86 (t, J = 1.7 Hz, 1H, Ar), 8.29 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.1, 45.4, 54.2, 113.2, 118.5, 122.8, 124.5, 127.6, 129.3, 129.7, 130.1, 130.5, 131.3, 131.4, 137.7, 140.4, 140.8, 147.4; HRMS (FAB): m/z calcd for C22H23N4S [M + H]+ 375.1643; found: 375.1646.

Compound 31j. Using the general procedure as described for 25a, compound 29j (40.3 mg, 0.11 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (2:1 to 0:1) gave the title compound 31j as colorless solid (30.6 mg, 89 %): mp 196–197 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 2230 (C ≡ N), 1623 (C=N), 1572 (C=N); 1H-NMR (400 MHz, CDCl3–CD3OD) δ: 1.98–2.04 (m, 2H, CH2), 3.71 (t, J = 5.5 Hz, 2H, CH2), 4.01 (t, J = 6.1 Hz, 2H, CH2), 7.25 (d, J = 1.8 Hz, 1H, Ar), 7.44 (dd, J = 8.5, 1.8 Hz, 1H, Ar), 7.58 (t, J = 7.8 Hz, 1H, Ar), 7.68 (d, J = 7.8 Hz, 1H, Ar), 7.81 (d, J = 7.8 Hz, 1H, Ar), 7.86 (s, 1H, Ar), 8.27 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3–CD3OD) δ: 20.7, 43.9, 44.7, 113.0, 118.3, 121.9, 124.9, 126.2, 129.5, 129.7, 129.7, 130.4, 131.3, 131.5, 140.2, 141.0, 146.6, 153.4; HRMS (FAB): m/z calcd for C18H15N4S [M + H]+ 319.1017; found: 319.1016.

Synthesis of 3,4-Dihydro-9-(3-nitrophenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31k)

N -( tert -Butyl)-3,4-dihydro-9-(3-nitrophenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29k). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-nitrophenylboronic acid (30.0 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 8:2) gave the title compound 29k as colorless solid (52.3 mg, 88 %): mp 208–209 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1593 (C=N), 1529 (NO2); 1H-NMR (500 MHz, CDCl3) δ: 1.41 (s, 9H, 3 × CH3), 1.92–1.96 (m, 2H, CH2), 3.65 (t, J = 5.4 Hz, 2H, CH2), 3.90 (t, J = 6.3 Hz, 2H, CH2), 7.37 (d, J = 1.7 Hz, 1H, Ar), 7.44 (dd, J = 8.6, 1.7 Hz, 1H, Ar), 7.62 (t, J = 8.0 Hz, 1H, Ar), 7.91 (dd, J = 8.0, 2.0 Hz, 1H, Ar), 8.22 (dd, J = 8.0, 2.0 Hz, 1H, Ar), 8.31 (d, J = 8.6 Hz, 1H, Ar), 8.44 (t, J = 2.0 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.2, 45.4, 54.3, 121.8, 122.7, 122.9, 124.6, 127.7, 129.4, 129.9, 130.2, 132.9, 137.6, 140.2, 141.1, 147.4, 148.7; HRMS (FAB): m/z calcd for C21H23N4O2S [M + H]+ 395.1542; found: 395.1544.

Compound 31k. Using the general procedure as described for 25a, compound 29k (37.9 mg, 0.096 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1) gave the title compound 31k as colorless solid (23.2 mg, 71 %): mp 168–170 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1567 (C=N), 1529 (NO2); 1H-NMR (500 MHz, CDCl3) δ: 1.98-2.03 (m, 2H, CH2), 3.72 (t, J = 5.7 Hz, 2H, CH2), 4.05 (t, J = 6.0 Hz, 2H, CH2), 7.28 (d, J = 1.7 Hz, 1H, Ar), 7.47 (dd, J = 8.6, 1.7 Hz, 1H, Ar), 7.63 (t, J = 7.7 Hz, 1H, Ar), 7.90 (dd, J = 7.7, 1.7 Hz, 1H, Ar), 8.23 (dd, J = 7.7, 1.7 Hz, 1H, Ar), 8.34 (d, J = 8.6 Hz, 1H, Ar), 8.42 (t, J = 1.7 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 121.8, 121.9, 122.9, 124.9, 126.7, 129.8, 129.9, 130.0, 132.8, 140.7, 140.8, 146.0, 148.7, 152.8; Anal. calcd for C17H14N4O2S: C, 60.34; H, 4.17; N, 16.56. Found: C, 60.04; H, 4.13; N, 16.28.

Synthesis of (±)-3,4-Dihydro-9-[3-(1-hydroxyethyl)phenyl]-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31l)

N -( tert -Butyl)-3,4-dihydro-9-(3-vinylphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29l). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (70.6 mg, 0.20 mmol) was allowed to react with 3-vinylphenylboronic acid (35.5 mg, 0.24 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29l as a colorless oil (64.4 mg, 86 %): IR (neat) cm−1: 1591 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.90–1.95 (m, 2H, CH2), 3.64 (t, J = 5.4 Hz, 2H, CH2), 3.89 (t, J = 6.3 Hz, 2H, CH2), 5.30 (d, J = 10.9 Hz, 1H, CH), 5.82 (d, J = 17.8 Hz, 1H, CH), 6.77 (dd, J = 17.8, 10.9 Hz, 1H, CH), 7.34 (d, J = 1.7 Hz, 1H, Ar), 7.37–7.47 (m, 4H, Ar), 7.59 (s, 1H, Ar), 8.25 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 114.5, 122.7, 124.8, 125.0, 125.8, 126.5, 126.6, 128.9, 129.0, 129.5, 136.5, 138.2, 138.2, 139.7, 142.8, 147.7; HRMS (FAB): m/z calcd for C23H26N3S [M + H]+ 376.1847; found: 376.1850.

Compound 31l. Using the general procedure as described for 25a, compound 29l (58.5 mg, 0.16 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 1:1) gave the title compound 31l as colorless solid (25.9 mg, 49 %): mp 193–195 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1616 (C=N), 1558 (C=N); 1H-NMR (400 MHz, DMSO-d 6) δ: 1.36 (d, J = 6.6 Hz, 3H, CH3), 1.84–1.89 (m, 2H, CH2), 3.59 (t, J = 5.1 Hz, 2H, CH2), 3.92 (t, J = 6.0 Hz, 2H, CH2), 4.76–4.81 (m, 1H, CH), 5.20 (d, J = 4.4 Hz, 1H, OH), 7.36–7.43 (m, 2H, Ar), 7.53–7.57 (m, 3H, Ar), 7.67 (s, 1H, Ar), 8.24 (d, J = 8.3 Hz, 1H, Ar), 8.71 (s, 1H, NH); 13C-NMR (125 MHz, CDCl3–CD3OD) δ: 20.6, 25.0, 44.0, 44.5, 69.5, 121.7, 123.8, 125.0, 125.1, 125.3, 125.6, 128.8, 129.0, 129.0, 138.8, 143.6, 146.8, 147.2, 154.1; HRMS (FAB): m/z calcd for C19H20N3OS [M + H]+ 338.1327; found: 338.1327.

Synthesis of 9-[3-(Acetylamino)phenyl]-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31m)

9-[3-(Acetylamino)phenyl]- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29m). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-(acetylamino)phenylboronic acid (32.2 mg, 0.18 mmol) in 1,4-dioxane for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1) gave the title compound 29m as colorless solid (44.6 mg, 73 %): mp 221–222 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1670 (C=O), 1590 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.91–1.95 (m, 2H, CH2), 2.18 (s, 3H, CH3), 3.64 (t, J = 5.4 Hz, 2H, CH2), 3.89 (t, J = 6.0 Hz, 2H, CH2), 7.29–7.38 (m, 4H, Ar), 7.50 (d, J = 7.4 Hz, 1H, Ar), 7.70 (s, 1H, NH), 7.73 (s, 1H, Ar), 8.21 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 24.5, 30.0 (3C), 45.1, 45.4, 54.2, 118.4, 119.5, 122.8, 122.9, 124.8, 126.7, 128.8, 129.5, 129.5, 138.2, 138.5, 140.2, 142.4, 147.9, 168.5; HRMS (FAB): m/z calcd for C23H27N4OS [M + H]+ 407.1906; found: 407.1905.

Compound 31m. Using the general procedure as described for 25a, compound 29m (35.4 mg, 0.096 mmol) was allowed to react for 3 h. Purification by preparative TLC over aluminum oxide with EtOAc–MeOH (98:2) gave the title compound 31m as colorless solid (23.7 mg, 78 %): mp 208–210 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1691 (C=O), 1611 (C=N), 1561 (C=N); 1H-NMR (DMSO-d 6) δ: 1.85-1.90 (m, 2H, CH2), 2.06 (s, 3H, CH3), 3.60 (t, J = 5.4 Hz, 2H, CH2), 3.93 (t, J = 6.0 Hz, 2H, CH2), 7.37–7.41 (m, 2H, Ar), 7.46–7.49 (m, 2H, Ar), 7.61 (d, J = 6.3 Hz, 1H, Ar), 7.90 (s, 1H, Ar), 8.26 (d, J = 8.0 Hz, 1H, Ar), 8.75 (s, 1H, NH), 10.04 (s, 1H, NH); 13C-NMR (125 MHz, CDCl3–CD3OD) δ: 20.7, 23.7, 44.0, 44.5, 118.3, 119.6, 121.8, 122.4, 125.1 (2C), 129.0, 129.0, 129.2, 138.8, 139.4, 143.3, 147.2, 154.1, 169.7; HRMS (FAB): m/z calcd for C19H17N4OS [M − H]− 349.1123; found: 349.1129.

Synthesis of 3,4-Dihydro-9-[3-(methanesulfonylamino)phenyl]-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31n)

N -( tert -Butyl)-3,4-dihydro-9-[3-(methanesulfonylamino)phenyl]-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29n). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-(methanesulfonylamino)phenylboronic acid (38.7 mg, 0.18 mmol) in 1,4-dioxane for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:2 to 0:1) gave the title compound 29n as colorless solid (20.1 mg, 30 %): mp 200–202 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1591 (C=N), 1153 (NSO2); 1H-NMR (500 MHz, CDCl3–CD3OD) δ: 1.41 (s, 9H, 3 × CH3), 1.92-1.97 (m, 2H, CH2), 3.02 (s, 3H, CH3), 3.62 (t, J = 5.2 Hz, 2H, CH2), 3.90 (t, J = 6.0 Hz, 2H, CH2), 7.27 (d, J = 7.4 Hz, 1H, Ar), 7.34-7.43 (m, 5H, Ar), 8.15 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.8, 30.0 (3C), 39.5, 44.9, 45.5, 54.3, 119.1, 119.8, 122.9, 123.7, 124.8, 127.0, 129.0, 129.8, 130.1, 137.7, 137.9, 140.9, 142.0, 148.4; HRMS (FAB): m/z calcd for C22H27N4O2S2 [M + H]+ 443.1575; found: 443.1574.

Compound 31n. Using the general procedure as described for 25a, compound 29n (26.1 mg, 0.059 mmol) was allowed to react for 4.5 h. Purification by preparative TLC over aluminum oxide with EtOAc–MeOH (95:5) gave the title compound 31n as colorless solid (13.4 mg, 59 %): mp 194–196 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1625 (C=N), 1557 (C=N), 1325 (NSO2), 1147 (NSO2); 1H-NMR (500 MHz, CDCl3–CD3OD) δ: 1.98-2.03 (m, 2H, CH2), 3.02 (s, 3H, CH3), 3.70 (t, J = 5.4 Hz, 2H, CH2), 4.00 (t, J = 6.3 Hz, 2H, CH2), 7.23–7.46 (m, 6H, Ar), 8.21 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3–CD3OD) δ: 20.8, 39.1, 44.0, 44.7, 118.8, 120.0, 121.9, 123.4, 125.2, 125.6, 129.3, 129.5, 130.1, 138.0, 140.5, 142.7, 147.0, 153.9; HRMS (FAB): m/z calcd for C18H19N4O2S2 [M + H]+ 387.0949; found: 387.0957.

Synthesis of 3,4-Dihydro-9-(3-hydroxyphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31o)

N -( tert -Butyl)-3,4-dihydro-9-(3-hydroxyphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29o). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-hydroxyphenylboronic acid (24.8 mg, 0.18 mmol) in 1,4-dioxane for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1 to 0:1) gave the title compound 29o as colorless solid (16.1 mg, 29 %): mp 265–267 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1591 (C=N); 1H-NMR (500 MHz, CDCl3–CD3OD) δ: 1.41 (s, 9H, 3 × CH3), 1.92–1.97 (m, 2H, CH2), 3.60 (t, J = 5.2 Hz, 2H, CH2), 3.90 (t, J = 6.0 Hz, 2H, CH2), 6.85 (d, J = 8.0 Hz, 1H, Ar), 7.03 (s, 1H, Ar), 7.08 (d, J = 8.0 Hz, 1H, Ar), 7.27 (t, J = 8.0 Hz, 1H, Ar), 7.34 (s, 1H, Ar), 7.43 (d, J = 8.0 Hz, 1H, Ar), 8.09 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3–CD3OD) δ: 21.5, 29.7 (3C), 44.5, 45.4, 54.2, 113.8, 115.1, 118.2, 122.8, 124.9, 126.0, 128.5, 129.4, 129.8, 138.1, 140.4, 143.2, 149.4, 157.2; HRMS (FAB): m/z calcd for C21H24N3OS [M + H]+ 366.1640; found: 366.1639.

Compound 31o. TFA (9 mL) was added to a mixture of 29o (16.1 mg, 0.044 mmol) and MS4Å (2.0 g, powder, activated by heating with Bunsen burner) in CHCl3 (1.0 mL) and MeOH (10 drops). After being stirred under reflux for 5 h, the mixture was concentrated. To a mixture of the residue in CHCl3 was added dropwise Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by preparative TLC over aluminum oxide with EtOAc–MeOH (95:5) to give the title compound 31o as colorless solid (7.9 mg, 58 %): mp 199–200 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1621 (C=N), 1557 (C=N); 1H-NMR (500 MHz, DMSO-d 6) δ: 1.85-1.90 (m, 2H, CH2), 3.60 (t, J = 5.4 Hz, 2H, CH2), 3.92 (t, J = 5.4 Hz, 2H, CH2), 6.81 (dd, J = 7.7, 2.0 Hz, 1H, Ar), 7.06 (t, J = 2.0 Hz, 1H, Ar), 7.13 (d, J = 8.3 Hz, 1H, Ar), 7.27 (t, J = 7.7 Hz, 1H, Ar), 7.48–7.50 (m, 2H, Ar), 8.22 (d, J = 8.3 Hz, 1H, Ar), 8.74 (br s, 1H, NH), 9.57 (s, 1H, OH); 13C-NMR (100 MHz, DMSO-d 6) δ: 20.7, 43.1, 44.3, 113.5, 115.3, 117.5, 121.4, 124.2, 124.9, 129.0, 129.5, 130.0, 139.5, 142.3, 145.2, 149.7, 157.8; HRMS (FAB): m/z calcd for C17H16N3OS [M + H]+ 310.1014; found: 310.1010.

Synthesis of 3,4-Dihydro-9-(4-methoxyphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31p)

N -( tert -Butyl)-3,4-dihydro-9-(3-methoxyphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29p). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-methoxyphenylboronic acid (27.4 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29p as a colorless oil (55.6 mg, 98 %): IR (neat) cm−1: 1591 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.90–1.96 (m, 2H, CH2), 3.64 (t, J = 5.5 Hz, 2H, CH2), 3.86 (s, 3H, CH3), 3.89 (t, J = 6.2 Hz, 2H, CH2), 6.91 (dd, J = 8.2, 2.5 Hz, 1H, Ar), 7.10 (t, J = 2.5 Hz, 1H, Ar), 7.15–7.18 (m, 1H, Ar), 7.32–7.37 (m, 2H, Ar), 7.41 (dd, J = 8.5, 1.7 Hz, 1H, Ar), 8.24 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 55.3, 112.7, 113.5, 119.5, 122.8, 124.9, 126.7, 128.9, 129.5, 129.9, 138.2, 140.9, 142.8, 147.7, 160.0; HRMS (FAB): m/z calcd for C22H26N3OS [M + H]+ 380.1797; found: 380.1793.

Compound 31p. Using the general procedure as described for 25a, compound 29p (32.1 mg, 0.085 mmol) was allowed to react for 2 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (3:1) gave the title compound 31p as colorless solid (23.4 mg, 85 %): mp 114–115 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1569 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.96–2.02 (m, 2H, CH2), 3.71 (t, J = 5.5 Hz, 2H, CH2), 3.86 (s, 3H, CH3), 4.04 (t, J = 6.2 Hz, 2H, CH2), 6.93 (dd, J = 7.9, 2.7 Hz, 1H, Ar), 7.09 (t, J = 2.7 Hz, 1H, Ar), 7.14–7.17 (m, 1H, Ar), 7.21 (br s, NH), 7.24 (d, J = 1.7 Hz, 1H, Ar), 7.36 (t, J = 7.9 Hz, 1H, Ar), 7.44 (dd, J = 8.5, 1.7 Hz, 1H, Ar), 8.27 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 55.4, 112.8, 113.6, 119.5, 121.8, 125.2, 125.6, 129.3, 129.3, 129.9, 140.6, 143.4, 146.4, 153.4, 160.0; Anal. calcd for C18H17N3OS: C, 66.85; H, 5.30; N, 12.99. Found: C, 66.56; H, 5.14; N, 12.83.

Synthesis of 3,4-Dihydro-9-(3-isopropoxyphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31q)

N -( tert -Butyl)-3,4-dihydro-9-(3-isopropoxyphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29q). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-isopropoxyphenylboronic acid (32.4 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29q as a colorless oil (48.8 mg, 80 %): IR (neat) cm−1: 1592 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.36 (d, J = 5.7 Hz, 6H, 2 × CH3), 1.40 (s, 9H, 3 × CH3), 1.90-1.95 (m, 2H, CH2), 3.64 (t, J = 5.7 Hz, 2H, CH2), 3.89 (t, J = 6.0 Hz, 2H, CH2), 4.58-4.65 (m, 1H, CH), 6.89 (dd, J = 8.0, 2.0 Hz, 1H, Ar), 7.10 (t, J = 2.0 Hz, 1H, Ar), 7.14 (dd, J = 7.4, 2.0 Hz, 1H, Ar), 7.31–7.34 (m, 2H, Ar), 7.41 (dd, J = 8.0, 1.7 Hz, 1H, Ar), 8.24 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 22.0 (2C), 30.0 (3C), 45.1, 45.4, 54.1, 69.9, 114.9, 115.1, 119.3, 122.8, 124.8, 126.6, 128.8, 129.4, 129.9, 138.3, 140.9, 142.8, 147.7, 158.3; HRMS (FAB): m/z calcd for C24H30N3OS [M + H]+ 408.2110; found: 408.2108.

Compound 31q. Using the general procedure as described for 25a, compound 29q (44.0 mg, 0.108 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 31q as a colorless oil (35.5 mg, 94 %): IR (neat) cm−1: 1620 (C=N), 1567 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.36 (d, J = 6.1 Hz, 6H, 2 × CH3), 1.95–2.01 (m, 2H, CH2), 3.70 (t, J = 5.5 Hz, 2H, CH2), 4.03 (t, J = 6.2 Hz, 2H, CH2), 4.57–4.66 (m, 1H, CH), 6.90 (dd, J = 8.3, 2.4 Hz, 1H, Ar), 7.09 (d, J = 1.8 Hz, 1H, Ar), 7.11–7.13 (m, 1H, Ar), 7.23 (d, J = 1.8 Hz, 1H, Ar), 7.33 (t, J = 8.0 Hz, 1H, Ar), 7.43 (dd, J = 8.5, 1.8 Hz, 1H, Ar), 8.26 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 22.0 (2C), 43.8, 45.0, 70.0, 115.0, 115.2, 119.2, 121.8, 125.1, 125.5, 129.2, 129.3, 129.9, 140.6, 143.4, 146.4, 153.4, 158.3; HRMS (FAB): m/z calcd for C20H22N3OS [M + H]+ 352.1484; found: 352.1484.

Synthesis of 9-[(1,1′-Biphenyl)-3-yl]-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31r)

9-[(1,1′-Biphenyl)-3-yl]- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29r). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-biphenylboronic acid (35.7 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29r as a colorless oil (65.1 mg, > 99 %.): IR (neat) cm−1: 1591 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.41 (s, 9H, 3 × CH3), 1.91–1.95 (m, 2H, CH2), 3.64 (t, J = 5.4 Hz, 2H, CH2), 3.89 (t, J = 6.3 Hz, 2H, CH2), 7.35–7.39 (m, 2H, Ar), 7.44–7.51 (m, 4H, Ar), 7.55–7.60 (m, 2H, Ar), 7.63 (d, J = 7.4 Hz, 2H, Ar), 7.78 (s, 1H, Ar), 8.27 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 122.8, 124.9, 125.9 (2C), 126.7, 126.9, 127.2 (2C), 127.5, 128.8 (2C), 129.0, 129.3, 129.6, 138.2, 139.9, 140.9, 142.0, 142.8, 147.7; HRMS (FAB): m/z calcd for C27H28N3S [M + H]+ 426.2004; found: 426.2000.

Compound 31r. Using the general procedure as described for 25a, compound 29r (56.1 mg, 0.13 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 31r as colorless solid (37.0 mg, 76 %): mp 179–181 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1568 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.97–2.02 (m, 2H, CH2), 3.72 (t, J = 5.4 Hz, 2H, CH2), 4.04 (t, J = 6.0 Hz, 2H, CH2), 7.30 (d, J = 1.7 Hz, 1H, Ar), 7.38 (t, J = 7.4 Hz, 1H, Ar), 7.45–7.56 (m, 5H, Ar), 7.59–7.64 (m, 3H, Ar), 7.77 (s, 1H, Ar), 8.30 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.9, 45.0, 121.9, 125.2, 125.6, 125.9 (2C), 127.1, 127.2 (2C), 127.6, 128.8 (2C), 129.3, 129.4 (2C), 139.7, 140.8, 142.1, 143.4, 146.4, 153.3; HRMS (FAB): m/z calcd for C23H20N3S [M + H]+ 370.1378; found: 370.1378.

Synthesis of 3,4-Dihydro-9-(2-methoxyphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31s)

N -( tert -Butyl)-3,4-dihydro-9-(2-methoxyphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29s). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 2-methoxyphenylboronic acid (27.4 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29s as a colorless oil (46.0 mg, 81 %): IR (neat) cm−1: 1591 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.39 (s, 9H, 3 × CH3), 1.89–1.95 (m, 2H, CH2), 3.63 (t, J = 5.4 Hz, 2H, CH2), 3.80 (s, 3H, CH3), 3.88 (t, J = 5.9 Hz, 2H, CH2), 6.97 (d, J = 8.3 Hz, 1H, Ar), 7.02 (t, J = 7.4 Hz, 1H, Ar), 7.29–7.38 (m, 4H, Ar), 8.21 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 22.0, 30.0 (3C), 45.1, 45.4, 54.1, 55.6, 111.4, 120.9, 125.2, 126.2, 127.5, 128.0, 128.6, 129.1, 129.3, 130.6, 138.6, 140.6, 147.9, 156.5; HRMS (FAB): m/z calcd for C22H26N3OS [M + H]+ 380.1797; found: 380.1793.

Compound 31s. Using the general procedure as described for 25a, compound 29s (34.7 mg, 0.091 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 31s as colorless solid (21.6 mg, 73 %): mp 130.5 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1567 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.95-2.01 (m, 2H, CH2), 3.70 (t, J = 5.6 Hz, 2H, CH2), 3.80 (s, 3H, CH3), 4.03 (t, J = 6.2 Hz, 2H, CH2), 6.97 (d, J = 8.3 Hz, 1H, Ar), 7.02 (td, J = 7.5, 0.8 Hz, 1H, Ar), 7.22 (d, J = 1.5 Hz, 1H, Ar), 7.28-7.40 (m, 3H, Ar), 8.24 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.1, 43.8, 44.9, 55.6, 111.3, 120.9, 124.3, 125.1, 127.7, 128.3, 128.4, 128.7, 129.5, 130.5, 141.1, 146.6, 153.7, 156.4; Anal. calcd for C18H17N3OS: C, 66.85; H, 5.30; N, 12.99. Found: C, 66.56; H, 5.08; N, 12.90.

Synthesis of 9-[(1,1′-Biphenyl)-2-yl]-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31t)

9-[(1,1′-Biphenyl)-2-yl]- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29t). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 2-biphenylboronic acid (35.7 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29t as a colorless oil (64.1 mg, >99 %.): IR (neat) cm−1: 1591 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.36 (s, 9H, 3 × CH3), 1.86–1.91 (m, 2H, CH2), 3.59 (t, J = 5.6 Hz, 2H, CH2), 3.85 (t, J = 6.2 Hz, 2H, CH2), 6.91–6.93 (m, 2H, Ar), 7.11–7.14 (m, 2H, Ar), 7.19–7.22 (m, 3H, Ar), 7.40–7.42 (m, 4H, Ar), 7.99 (d, J = 8.8 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 29.9 (3C), 45.1, 45.4, 54.1, 125.5, 125.9, 126.7, 127.5, 127.9, 127.9, 128.1, 128.1 (2C), 128.6, 129.7 (2C), 130.2, 130.7, 138.4, 138.9, 140.6, 140.9, 143.6, 147.8; HRMS (FAB): m/z calcd for C27H28N3S [M + H]+ 426.2004; found: 426.2002.

Compound 31t. Using the general procedure as described for 25a, compound 29t (51.1 mg, 0.12 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 31t as a colorless oil (35.7 mg, 81 %): IR (neat) cm−1: 1620 (C=N), 1570 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.92-1.98 (m, 2H, CH2), 3.66 (t, J = 5.5 Hz, 2H, CH2), 3.99 (t, J = 6.1 Hz, 2H, CH2), 6.83 (d, J = 1.7 Hz, 1H, Ar), 6.95 (dd, J = 8.3, 1.7 Hz, 1H, Ar), 7.11–7.13 (m, 2H, Ar), 7.20–7.23 (m, 3H, Ar), 7.38–7.43 (m, 4H, Ar), 8.03 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 124.5, 124.8, 126.8, 127.6, 128.1 (3C), 128.1, 128.2, 128.3, 128.4, 129.7 (2C), 130.2, 138.5, 140.6, 140.8, 144.2, 146.5, 153.5; HRMS (FAB): m/z calcd for C23H20N3S [M + H]+ 370.1378; found: 370.1378.

Synthesis of 3,4-Dihydro-9-(3,4-dimethoxyphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31u)

N -( tert -Butyl)-3,4-dihydro-9-(3,4-dimethoxyphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29u). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3,4-dimethoxyphenylboronic acid (32.8 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29u as colorless solid (60.3 mg, 98 %): mp 147–148 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1593 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.90–1.96 (m, 2H, CH2), 3.64 (t, J = 5.5 Hz, 2H, CH2), 3.89 (t, J = 6.1 Hz, 2H, CH2), 3.92 (s, 3H, CH3), 3.96 (s, 3H, CH3), 6.93 (d, J = 8.3 Hz, 1H, Ar), 7.09 (d, J = 2.0 Hz, 1H, Ar), 7.15 (dd, J = 8.3, 2.0 Hz, 1H, Ar), 7.29 (d, J = 1.7 Hz, 1H, Ar), 7.39 (dd, J = 8.3, 1.7 Hz, 1H, Ar), 8.23 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.1, 56.0, 56.0, 110.1, 111.4, 119.5, 122.2, 124.5, 126.1, 128.9, 129.4, 132.3, 138.3, 142.7, 147.7, 149.3 (2C); HRMS (FAB): m/z calcd for C23H28N3O2S [M + H]+ 410.1902; found: 410.1907.

Compound 31u. Using the general procedure as described for 25a, compound 29u (46.0 mg, 0.11 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 31u as colorless solid (24.6 mg, 63 %): mp 142 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1567 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.96-2.02 (m, 2H, CH2), 3.71 (t, J = 5.6 Hz, 2H, CH2), 3.92 (s, 3H, CH3), 3.96 (s, 3H, CH3), 4.04 (t, J = 6.2 Hz, 2H, CH2), 6.93 (d, J = 8.3 Hz, 1H, Ar), 7.07 (d, J = 2.0 Hz, 1H, Ar), 7.14 (dd, J = 8.3, 2.0 Hz, 1H, Ar), 7.20 (d, J = 1.8 Hz, 1H, Ar), 7.41 (dd, J = 8.3, 1.8 Hz, 1H, Ar), 8.25 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 56.0, 56.0, 110.1, 111.5, 119.5, 121.3, 124.7, 125.0, 129.3, 129.4, 132.0, 143.2, 146.4, 149.3, 149.4, 153.4; Anal. calcd for C19H19N3O2S: C, 64.57; H, 5.42; N, 11.89. Found: C, 64.41; H, 5.37; N, 11.93.

Synthesis of 3,4-Dihydro-9-(3,4,5-trimethoxyphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31v)

N -( tert -Butyl)-3,4-dihydro-9-(3,4,5-trimethoxyphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29v). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3,4,5-trimethoxyphenylboronic acid (38.2 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29v as a colorless oil (65.0 mg, 99 %): IR (neat) cm−1: 1585 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.41 (s, 9H, 3 × CH3), 1.91–1.96 (m, 2H, CH2), 3.64 (t, J = 5.5 Hz, 2H, CH2), 3.88–3.91 (m, 5H, CH3, CH2), 3.93 (s, 6H, 2 × CH3), 6.77 (s, 2H, Ar), 7.28 (d, J = 1.8 Hz, 1H, Ar), 7.38 (dd, J = 8.4, 1.8 Hz, 1H, Ar), 8.24 (d, J = 8.4 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 56.3 (2C), 60.9, 104.4 (2C), 122.6, 124.7, 126.5, 128.9, 129.5, 135.3, 138.1, 138.3, 143.0, 147.7, 153.6 (2C); HRMS (FAB): m/z calcd for C24H30N3O3S [M + H]+ 440.2008; found: 440.2008.

Compound 31v. Using the general procedure as described for 25a, compound 29v (49.4 mg, 0.11 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 31v as colorless solid (14.2 mg, 34 %): mp 156–157 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1569 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.97–2.02 (m, 2H, CH2), 3.71 (t, J = 5.5 Hz, 2H, CH2), 3.89 (s, 3H, CH3), 3.93 (s, 6H, 2 × CH3), 4.04 (t, J = 6.1 Hz, 2H, CH2), 6.75 (s, 2H, Ar), 7.20 (d, J = 1.7 Hz, 1H, Ar), 7.40 (dd, J = 8.5, 1.7 Hz, 1H, Ar), 8.27 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.9, 45.0, 56.3 (2C), 61.0, 104.4 (2C), 121.7, 125.0, 125.4, 129.3 (2C), 135.0, 138.5, 143.6, 146.4, 153.3, 153.6 (2C); HRMS (FAB): m/z calcd for C20H22N3O3S [M + H]+ 384.1382; found: 384.1381.

Synthesis of 9-(3-Chloro-4-methoxyphenyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31w)

N -( tert -Butyl)-9-(3-chloro-4-methoxyphenyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29w). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-chloro-4-methoxyphenylboronic acid (33.6 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29w as a colorless oil (58.7 mg, 95 %): IR (neat) cm−1: 1592 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.90–1.95 (m, 2H, CH2), 3.64 (t, J = 5.4 Hz, 2H, CH2), 3.89 (t, J = 6.0 Hz, 2H, CH2), 3.94 (s, 3H, CH3), 6.98 (d, J = 8.6 Hz, 1H, Ar), 7.26 (d, J = 2.0 Hz, 1H, Ar), 7.36 (dd, J = 8.6, 2.0 Hz, 1H, Ar), 7.45 (dd, J = 8.6, 2.3 Hz, 1H, Ar), 7.61 (d, J = 2.3 Hz, 1H, Ar), 8.23 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 56.2, 112.2, 122.2, 123.0, 124.3, 126.2, 126.4, 128.7, 129.0, 129.7, 132.7, 138.1, 141.2, 147.6, 155.0; HRMS (FAB): m/z calcd for C22H25ClN3OS [M + H]+ 414.1407; found: 414.1402.

Compound 31w. Using the general procedure as described for 25a, compound 29w (41.6 mg, 0.10 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 31w as colorless solid (18.8 mg, 53 %): mp 186–188 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1563 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.97–2.01 (m, 2H, CH2), 3.71 (t, J = 5.4 Hz, 2H, CH2), 3.94 (s, 3H, CH3), 4.03 (t, J = 6.0 Hz, 2H, CH2), 6.98 (d, J = 8.6 Hz, 1H, Ar), 7.17 (d, J = 1.4 Hz, 1H, Ar), 7.38 (dd, J = 8.0, 2.3 Hz, 1H, Ar), 7.44 (dd, J = 8.0, 1.4 Hz, 1H, Ar), 7.59 (d, J = 2.3 Hz, 1H, Ar), 8.25 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 56.2, 112.2, 121.2, 123.0, 124.5, 125.3, 126.2, 128.7, 129.4, 129.5, 132.4, 141.7, 146.3, 153.2, 155.1; HRMS (FAB): m/z calcd for C18H17ClN3OS [M + H]+ 358.0781; found: 358.0777.

Synthesis of 9-(3-Chloro-6-methoxyphenyl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (31x)

N -( tert -Butyl)-9-(3-chloro-6-methoxyphenyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (29x). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-chloro-6-methoxyphenylboronic acid (33.6 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 29x as a colorless oil (54.9 mg, 88 %): IR (neat) cm−1: 1591 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.39 (s, 9H, 3 × CH3), 1.89–1.95 (m, 2H, CH2), 3.64 (t, J = 5.5 Hz, 2H, CH2), 3.78 (s, 3H, CH3), 3.88 (t, J = 6.1 Hz, 2H, CH2), 6.88 (d, J = 9.5 Hz, 1H, Ar), 7.26–7.34 (m, 4H, Ar), 8.21 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.1, 55.9, 112.6, 125.1, 125.8, 126.7, 127.2, 128.1, 128.8, 128.8, 130.2, 130.6, 138.4, 139.2, 147.8, 155.1; HRMS (FAB): m/z calcd for C22H25ClN3OS [M + H]+ 414.1407; found: 414.1410.

Compound 31x. Using the general procedure as described for 25a, compound 29x (33.2 mg, 0.080 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 31x as colorless solid (16.3 mg, 57 %): mp 175–178 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1568 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.96–2.02 (m, 2H, CH2), 3.71 (t, J = 5.6 Hz, 2H, CH2), 3.79 (s, 3H, CH3), 4.04 (t, J = 6.2 Hz, 2H, CH2), 6.89 (d, J = 8.5 Hz, 1H, Ar), 7.19 (d, J = 1.7 Hz, 1H, Ar), 7.26–7.30 (m, 2H, Ar), 7.36 (dd, J = 8.3, 1.7 Hz, 1H, Ar), 8.27 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.9, 43.8, 44.8, 55.9, 112.5, 124.2, 125.3, 125.8, 127.5, 128.6, 128.9, 130.1 (2C), 130.1, 139.8, 146.6, 153.3, 155.0; HRMS (FAB): m/z calcd for C18H17ClN3OS [M + H]+ 358.0781; found: 358.0783.

Synthesis of 3,4-Dihydro-9-(naphthalen-2-yl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32a)

N -( tert -Butyl)-3,4-dihydro-9-(naphthalen-2-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30a). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 2-naphthaleneboronic acid (30.9 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 30a as colorless solid (56.3 mg, 94 %): mp 144–145 °C (from n-hexane); IR (neat) cm−1: 1592 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.42 (s, 9H, 3 × CH3), 1.91–1.96 (m, 2H, CH2), 3.65 (t, J = 5.2 Hz, 2H, CH2), 3.90 (t, J = 5.7 Hz, 2H, CH2), 7.45–7.51 (m, 3H, Ar), 7.55 (d, J = 8.0 Hz, 1H, Ar), 7.71 (d, J = 8.0 Hz, 1H, Ar), 7.84–7.91 (m, 3H, Ar), 8.04 (s, 1H, Ar), 8.29 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.5, 54.2, 122.9, 125.0 (2C), 126.0, 126.3, 126.5, 126.6, 127.6, 128.3, 128.6, 129.0, 129.6, 132.9, 133.5, 136.7, 138.3, 142.8, 147.7; HRMS (FAB): m/z calcd for C25H26N3S [M + H]+ 400.1847; found: 400.1848.

Compound 32a. Using the general procedure as described for 25a, compound 30a (45.3 mg, 0.11 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 32a as colorless solid (28.2 mg, 73 %): mp 143–145 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1568 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.96-2.02 (m, 2H, CH2), 3.72 (t, J = 5.6 Hz, 2H, CH2), 4.04 (t, J = 6.2 Hz, 2H, CH2), 7.36 (d, J = 1.8 Hz, 1H, Ar), 7.49–7.52 (m, 2H, Ar), 7.57 (dd, J = 8.5, 1.8 Hz, 1H, Ar), 7.68 (dd, J = 8.5, 1.8 Hz, 1H, Ar), 7.84–7.91 (m, 3H, Ar), 8.02 (d, J = 1.5 Hz, 1H, Ar), 8.33 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 122.0, 124.9, 125.3 (2C), 126.1, 126.4, 126.5, 127.6, 128.3, 128.7, 129.4 (2C), 133.0, 133.5, 136.3, 143.4, 146.5, 153.3; HRMS (FAB): m/z calcd for C21H18N3S [M + H]+ 344.1221; found: 344.1222.

Synthesis of 3,4-Dihydro-9-(naphthalen-1-yl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32b)

N -( tert -Butyl)-3,4-dihydro-9-(naphthalen-1-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30b). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 1-naphthaleneboronic acid (30.9 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 30b as a colorless oil (58.4 mg, 97 %): IR (neat) cm−1: 1590 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.92–1.98 (m, 2H, CH2), 3.67 (t, J = 5.6 Hz, 2H, CH2), 3.92 (t, J = 6.1 Hz, 2H, CH2), 7.25–7.25 (m, 1H, Ar), 7.34 (dd, J = 8.3, 1.7 Hz, 1H, Ar), 7.39–7.52 (m, 4H, Ar), 7.86 (d, J = 8.3 Hz, 2H, Ar), 7.89 (d, J = 7.6 Hz, 1H, Ar), 8.31 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 22.0, 30.0 (3C), 45.1, 45.4, 54.2, 125.3, 125.6, 125.6, 125.9, 126.3, 126.7, 126.8, 128.0, 128.2, 128.3, 128.3, 129.1, 131.2, 133.7, 138.2, 138.6, 142.8, 147.8; HRMS (FAB): m/z calcd for C25H26N3S [M + H]+ 400.1847; found: 400.1845.

Compound 32b. Using the general procedure as described for 25a, compound 30b (46.4 mg, 0.12 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 32b as colorless solid (34.4 mg, 86 %): mp 146–148 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1568 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.98–2.04 (m, 2H, CH2), 3.73 (t, J = 5.6 Hz, 2H, CH2), 4.06 (t, J = 6.2 Hz, 2H, CH2), 7.17 (d, J = 1.7 Hz, 1H, Ar), 7.35–7.52 (m, 5H, Ar), 7.81–7.91 (m, 3H, Ar), 8.33 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.1, 43.8, 45.0, 124.7, 125.2, 125.4, 125.6, 126.0, 126.4, 126.8, 128.3, 128.4 (2C), 128.7, 128.9, 131.1, 133.7, 138.2, 143.4, 146.5, 153.3; HRMS (FAB): m/z calcd for C21H18N3S [M + H]+ 344.1221; found: 344.1221.

Synthesis of 3,4-Dihydro-9-(3,4-methylenedioxyphenyl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32c)

N -( tert -Butyl)-3,4-dihydro-9-(3,4-methylenedioxyphenyl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30c). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3,4-(methylenedioxy)phenylboronic acid (29.9 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 30c as colorless solid (54.6 mg, 93 %): mp 173 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1591 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.89–1.95 (m, 2H, CH2), 3.63 (t, J = 5.5 Hz, 2H, CH2), 3.88 (t, J = 6.2 Hz, 2H, CH2), 5.99 (s, 2H, CH2), 6.87 (d, J = 8.8 Hz, 1H, Ar), 7.05–7.07 (m, 2H, Ar), 7.24 (d, J = 2.0 Hz, 1H, Ar), 7.34 (dd, J = 8.3, 2.0 Hz, 1H, Ar), 8.21 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 101.3, 107.4, 108.6, 120.7, 122.3, 124.5, 126.2, 128.9, 129.5, 133.7, 138.3, 142.6, 147.7, 147.7, 148.3; HRMS (FAB): m/z calcd for C22H24N3O2S [M + H]+ 394.1589; found: 394.1592.

Compound 32c. Using the general procedure as described for 25a, compound 30c (40.1 mg, 0.102 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 32c as colorless solid (17.0 mg, 49 %): mp 169–170 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1619 (C=N), 1568 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.95–2.01 (m, 2H, CH2), 3.70 (t, J = 5.5 Hz, 2H, CH2), 4.03 (t, J = 6.1 Hz, 2H, CH2), 6.00 (s, 2H, CH2), 6.87 (d, J = 7.8 Hz, 1H, Ar), 7.04–7.06 (m, 2H, Ar), 7.15 (d, J = 1.7 Hz, 1H, Ar), 7.20 (br s, 1H, NH), 7.36 (dd, J = 8.3, 1.7 Hz, 1H, Ar), 8.24 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 101.3, 107.4, 108.7, 120.8, 121.3, 124.8, 125.1, 129.3, 129.3, 133.4, 143.1, 146.4, 147.9, 148.3, 153.4; HRMS (FAB): m/z calcd for C18H16N3O2S [M + H]+ 338.0963; found: 338.0960.

Synthesis of 3,4-Dihydro-9-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32d)

N -( tert -Butyl)-3,4-dihydro-9-(2,3-dihydrobenzo[ b ][1,4]dioxin-6-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30d). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with (2,3-dihydrobenzo[b][1,4]dioxin-6-yl)boronic acid (32.3 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 30d as a colorless oil (63.9 mg, 96 %): IR (neat) cm−1: 1586 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.89–1.94 (m, 2H, CH2), 3.63 (t, J = 5.4 Hz, 2H, CH2), 3.88 (t, J = 6.0 Hz, 2H, CH2), 4.28 (s, 4H, 2 × CH2), 6.92 (d, J = 8.6 Hz, 1H, Ar), 7.07–7.09 (m, 1H, Ar), 7.11 (d, J = 2.3 Hz, 1H, Ar), 7.26 (s, 1H, Ar), 7.36 (t, J = 4.0 Hz, 1H, Ar), 8.21 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.1, 64.4, 64.5, 115.8, 117.6, 120.0, 122.2, 124.4, 126.1, 128.9, 129.4, 132.9, 138.4, 142.3, 143.8 (2C), 147.7; HRMS (FAB): m/z calcd for C23H26N3O2S [M + H]+ 408.1746; found: 408.1746.

Compound 32d. Using the general procedure as described for 25a, compound 30d (45.1 mg, 0.11 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 32d as colorless solid (26.7 mg, 69 %): mp 174–176 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1619 (C=N), 1567 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.95-2.00 (m, 2H, CH2), 3.70 (t, J = 5.7 Hz, 2H, CH2), 4.03 (t, J = 6.3 Hz, 2H, CH2), 4.28 (s, 4H, 2 × CH2), 6.92 (d, J = 8.6 Hz, 1H, Ar), 7.06 (dd, J = 8.6, 2.3 Hz, 1H, Ar), 7.09 (d, J = 2.3 Hz, 1H, Ar), 7.17 (d, J = 2.0 Hz, 1H, Ar), 7.19 (br s, 1H, NH), 7.38 (dd, J = 8.6, 2.0 Hz, 1H, Ar), 8.23 (d, J = 8.6 Hz, 1H, Ar; 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 64.3, 64.4, 115.8, 117.7, 120.0, 121.2, 124.6, 125.0, 129.2, 129.3, 132.5, 142.8, 143.8, 143.9, 146.4, 153.4; HRMS (FAB): m/z calcd for C19H18N3O2S [M + H]+ 352.1120; found: 352.1121.

Synthesis of 3,4-Dihydro-9-(quinolin-6-yl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32e)

N -( tert -Butyl)-3,4-dihydro-9-(quinolin-6-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30e). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 6-quinolineboronic acid (31.1 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 1:1) gave the title compound 30e as colorless solid (36.2 mg, 60 %): mp 179–180 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1590 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.42 (s, 9H, 3 × CH3), 1.91–1.97 (m, 2H, CH2), 3.66 (t, J = 5.4 Hz, 2H, CH2), 3.91 (t, J = 6.1 Hz, 2H, CH2), 7.42–7.46 (m, 2H, Ar), 7.55 (dd, J = 8.3, 1.8 Hz, 1H, Ar), 7.95 (dd, J = 8.8, 2.0 Hz, 1H, Ar), 8.00 (d, J = 1.5 Hz, 1H, Ar), 8.16–8.21 (m, 2H, Ar), 8.32 (d, J = 8.3 Hz, 1H, Ar), 8.93 (dd, J = 4.1, 1.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 121.6, 123.1, 125.0, 125.7, 126.9, 128.4, 128.7, 129.1, 129.8, 130.1, 136.2, 137.5, 138.0, 142.0, 147.6, 148.0, 150.7; HRMS (FAB): m/z calcd for C24H25N4S [M + H]+ 401.1800; found: 401.1802.

Compound 32e. Using the general procedure as described for 25a, compound 30e (27.0 mg, 0.067 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 1:1) gave the title compound 32e as colorless solid (19.3 mg, 84 %): mp 165–167 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1572 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.98–2.04 (m, 2H, CH2), 3.73 (t, J = 5.5 Hz, 2H, CH2), 4.06 (t, J = 6.1 Hz, 2H, CH2), 7.38 (d, J = 1.7 Hz, 1H, Ar), 7.45 (dd, J = 8.0, 4.3 Hz, 1H, Ar), 7.58 (dd, J = 8.3, 1.7 Hz, 1H, Ar), 7.94 (dd, J = 8.8, 2.2 Hz, 1H, Ar), 8.01 (d, J = 2.2 Hz, 1H, Ar), 8.18 (d, J = 8.8 Hz, 1H, Ar), 8.22 (dd, J = 8.0, 1.5 Hz, 1H, Ar), 8.35 (d, J = 8.3 Hz, 1H, Ar), 8.94 (dd, J = 4.3, 1.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 121.7, 122.1, 125.3, 125.8, 125.9, 128.3, 128.6, 129.5, 129.6, 130.2, 136.3, 137.2, 142.5, 146.3, 148.0, 150.8, 153.2; HRMS (FAB): m/z calcd for C20H17N4S [M + H]+ 345.1174; found: 345.1175.

Synthesis of 3,4-Dihydro-9-[3-(trifluoromethylcarbonyl)indol-6-yl]-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32f)

N -( tert -Butyl)-3,4-dihydro-9-(indol-6-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30f). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with indol-6-ylboronic acid (29.0 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (2:1) gave the title compound 30f as colorless solid (56.0 mg, 96 %): mp 256 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1589 (C=N); 1H-NMR (500 MHz, DMSO-d 6) δ: 1.39 (s, 9H, 3 × CH3), 1.82–1.87 (m, 2H, CH2), 3.55 (t, J = 5.4 Hz, 2H, CH2), 3.82 (t, J = 6.0 Hz, 2H, CH2), 6.46 (s, 1H, Ar), 7.37 (d, J = 8.3 Hz, 1H, Ar), 7.42 (t, J = 2.6 Hz, 1H, Ar), 7.58–7.63 (m, 3H, Ar), 7.72 (s, 1H, Ar), 8.21 (d, J = 8.3 Hz, 1H, Ar), 11.21 (br s, 1H, NH); 13C-NMR (125 MHz, CDCl3–CD3OD) δ: 21.6, 29.7 (3C), 44.6, 45.4, 54.2, 109.6, 118.8, 120.7 (2C), 122.8, 125.1, 125.3, 125.5, 127.8, 128.5, 129.3, 132.7, 136.3, 138.4, 144.5, 149.3; HRMS (FAB): m/z calcd for C23H25N4S [M + H]+ 389.1800; found: 389.1800.

Compound 32f. TFA (17 mL) was added to a mixture of 30f (31.9 mg, 0.082 mmol) and MS4 Å (4.5 g, powder, activated by heating with Bunsen burner) in CHCl3 (3.0 mL) and MeOH (5 drops). After being stirred under reflux for 8.5 h, the mixture was concentrated. To a mixture of this residue in CHCl3 was added dropwise Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by preparative TLC over aluminum oxide with CHCl3–MeOH (98:2) to give the title compound 32f as pale yellow solid (17.8 mg, 51 %): mp 270 °C (decomp.) (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1662 (C=O), 1568 (C=N); 1H-NMR (500 MHz, DMSO-d 6) δ: 1.86-1.91 (m, 2H, CH2), 3.61 (t, J = 5.4 Hz, 2H, CH2), 3.94 (t, J = 6.0 Hz, 2H, CH2), 7.61–7.62 (m, 2H, Ar), 7.71 (dd, J = 8.6, 1.7 Hz, 1H, Ar), 7.88 (s, 1H, Ar), 8.24–8.28 (m, 2H, Ar), 8.55 (d, J = 1.7 Hz, 1H, Ar), 8.75 (s, 1H, NH), 12.82 (br s, 1H, NH); 13C-NMR (100 MHz, DMSO-d 6) δ: 20.7, 43.1, 44.4, 108.8, 111.1, 116.8 (q, J = 291.3 Hz), 121.5, 121.7, 122.6, 124.4, 124.8, 125.7, 129.1, 129.6, 134.6, 137.2, 138.5 (q, J = 4.7 Hz), 142.4, 145.1, 149.7, 173.9 (q, J = 33.9 Hz); HRMS (FAB): m/z calcd for C21H16F3N4OS [M + H]+ 429.0997; found: 429.1001.

Synthesis of 3,4-Dihydro-9-[3-(trifluoromethylcarbonyl)indol-5-yl]-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32g)

N -( tert -Butyl)-3,4-dihydro-9-(indol-5-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30g). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with indol-5-ylboronic acid (29.0 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (2:1) gave the title compound 30g as colorless solid (59.2 mg, > 99 %): mp 232–233 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1583 (C=N); 1H-NMR (400 MHz, CDCl3–CD3OD) δ: 1.41 (s, 9H, 3 × CH3), 1.91–1.97 (m, 2H, CH2), 3.63 (t, J = 5.4 Hz, 2H, CH2), 3.90 (t, J = 6.1 Hz, 2H, CH2), 6.58 (d, J = 3.0 Hz, 1H, Ar), 7.23 (d, J = 3.0 Hz, 1H, Ar), 7.41–7.42 (m, 3H, Ar), 7.50 (dd, J = 8.5, 0.9 Hz, 1H, Ar), 7.86 (s, 1H, Ar), 8.18 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3–CD3OD) δ: 21.8, 29.9 (3C), 44.9, 45.5, 54.2, 102.7, 111.4, 119.2, 121.2, 122.7, 125.1, 125.1, 125.3, 128.3, 128.6, 129.3, 131.1, 135.7, 138.6, 144.6, 148.8; HRMS (FAB): m/z calcd for C23H25N4S [M + H]+ 389.1800; found: 389.1800.

Compound 32g. TFA (17 mL) was added to a mixture of 30g (28.5 mg, 0.073 mmol) and MS4Å (4.5 g, powder, activated by heating with Bunsen burner) in CHCl3 (3.0 mL). After being stirred under reflux for 10 h, the mixture was concentrated. To a mixture of this residue in CHCl3 was added dropwise Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by preparative TLC over aluminum oxide with CHCl3–MeOH (98:2) to give the compound 32g as pale yellow solid (28.9 mg, 92 %): mp 250 °C (decomp.) (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1659 (C=O), 1613 (C=N), 1561 (C=N); 1H-NMR (500 MHz, DMSO-d 6) δ: 1.86–1.91 (m, 2H, CH2), 3.61 (t, J = 5.4 Hz, 2H, CH2), 3.94 (t, J = 5.7 Hz, 2H, CH2), 7.56–7.59 (m, 2H, Ar), 7.67–7.72 (m, 2H, Ar), 8.28 (d, J = 8.6 Hz, 1H, Ar), 8.45 (s, 1H, Ar), 8.56 (d, J = 1.7 Hz, 1H, Ar), 8.75 (br s, 1H, NH), 12.82 (br s, 1H, NH); 13C-NMR (100 MHz, DMSO-d 6) δ: 20.7, 43.1, 44.4, 109.1, 113.6, 116.8 (q, J = 290.5 Hz), 119.2, 121.6, 123.7, 124.6, 124.6, 126.4, 129.1, 129.6, 133.9, 136.6, 138.4 (q, J = 4.7 Hz), 143.0, 145.2, 149.7, 173.9 (q, J = 33.7 Hz); HRMS (FAB): m/z calcd for C21H16F3N4OS [M + H]+ 429.0997; found: 429.0991.

Synthesis of 3,4-Dihydro-9-(pyridin-3-yl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32h)

N -( tert -Butyl)-3,4-dihydro-9-(pyridin-3-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30h). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-pyridineboronic acid (22.1 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 30h as colorless solid (45.9 mg, 87 %): mp 143–144 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1595 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.91–1.96 (m, 2H, CH2), 3.65 (t, J = 5.6 Hz, 2H, CH2), 3.89 (t, J = 6.2 Hz, 2H, CH2), 7.33 (d, J = 1.7 Hz, 1H, Ar), 7.36 (dd, J = 7.8, 4.9 Hz, 1H, Ar), 7.41 (dd, J = 8.5, 1.7 Hz, 1H, Ar), 7.87 (ddd, J = 7.8, 2.2, 1.5 Hz, 1H, Ar), 8.30 (d, J = 8.5 Hz, 1H, Ar), 8.62 (dd, J = 4.9, 1.5 Hz, 1H, Ar), 8.85 (d, J = 2.2 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.1, 45.4, 54.2, 122.8, 123.5, 124.7, 127.3, 129.3, 130.0, 134.2, 135.0, 137.8, 139.6, 147.5, 148.1, 149.2; HRMS (FAB): m/z calcd for C20H23N4S [M + H]+ 351.1643; found: 351.1645.

Compound 32h. Using the general procedure as described for 25a, compound 30h (36.3 mg, 0.10 mmol) was allowed to react for 2 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1) gave the title compound 32h as colorless solid (24.8 mg, 81 %): mp 191–193 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1616 (C=N), 1568 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.97–2.03 (m, 2H, CH2), 3.72 (t, J = 5.5 Hz, 2H, CH2), 4.05 (t, J = 6.1 Hz, 2H, CH2), 7.24 (d, J = 1.7 Hz, 1H, Ar), 7.38 (dd, J = 7.9, 4.8 Hz, 1H, Ar), 7.43 (dd, J = 8.3, 1.7 Hz, 1H, Ar), 7.86 (dt, J = 7.9, 1.8 Hz, 1H, Ar), 8.33 (d, J = 8.3 Hz, 1H, Ar), 8.63 (dd, J = 4.8, 1.8 Hz, 1H, Ar), 8.83 (d, J = 1.8 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 121.8, 123.6, 124.9, 126.2, 129.7, 129.8, 134.2, 134.7, 140.1, 146.2, 148.1, 149.3, 152.9; HRMS (FAB): m/z calcd for C16H15N4S [M + H]+ 295.1017; found: 295.1013.

Synthesis of 3,4-Dihydro-9-(pyridin-4-yl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32i)

N -( tert -Butyl)-3,4-dihydro-9-(pyridin-4-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30i). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 4-pyridineboronic acid (22.1 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 30i as colorless solid (27.6 mg, 52 %): mp 196–197 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1593 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.41 (s, 9H, 3 × CH3), 1.91–1.96 (m, 2H, CH2), 3.65 (t, J = 5.4 Hz, 2H, CH2), 3.89 (t, J = 6.0 Hz, 2H, CH2), 7.38 (s, 1H, Ar), 7.45 (d, J = 8.6 Hz, 1H, Ar), 7.49 (d, J = 5.0 Hz, 2H, Ar), 8.30 (d, J = 8.6 Hz, 1H, Ar), 8.67 (d, J = 5.0 Hz, 2H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.1, 45.4, 54.2, 121.4 (2C), 122.8, 124.4, 128.1, 129.3, 130.1, 137.6, 139.8, 146.6, 147.4, 150.4 (2C); HRMS (FAB): m/z calcd for C20H23N4S [M + H]+ 351.1643; found: 351.1644.

Compound 32i. Using the general procedure as described for 25a, compound 30i (23.4 mg, 0.067 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1 to 0:1) gave the title compound 32i as colorless solid (15.1 mg, 77 %): mp 154–155 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1575 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.97–2.02 (m, 2H, CH2), 3.72 (t, J = 5.4 Hz, 2H, CH2), 4.04 (t, J = 6.3 Hz, 2H, CH2), 7.29 (s, 1H, Ar), 7.46–7.48 (m, 3H, Ar), 8.33 (d, J = 8.6 Hz, 1H, Ar), 8.68 (d, J = 4.6 Hz, 2H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 121.4 (2C), 121.9, 124.8, 127.1, 129.7, 129.9, 140.3, 146.1, 146.3, 150.4 (2C), 152.8; Anal. calcd for C16H14N4S: C, 65.28; H, 4.79; N, 19.03. Found: C, 65.35; H, 4.63; N, 19.24.

Synthesis of 9-(Furan-2-yl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32j)

N -( tert -Butyl)-9-(furan-2-yl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30j). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 2-furanboronic acid (20.1 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 30j as colorless solid (42.4 mg, 83 %): mp 128–130 °C (from n-hexane); IR (neat) cm−1: 1596 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.89–1.94 (m, 2H, CH2), 3.63 (t, J = 5.5 Hz, 2H, CH2), 3.87 (t, J = 6.1 Hz, 2H, CH2), 6.47–6.49 (m, 1H, Ar), 6.71 (d, J = 3.4 Hz, 1H, Ar), 7.42–7.48 (m, 3H, Ar), 8.20 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 106.7, 111.9, 119.2, 121.4, 126.3, 128.8, 129.6, 132.3, 138.2, 142.8, 147.6, 152.5.; HRMS (FAB): m/z calcd for C19H22N3OS [M + H]+ 340.1484; found: 340.1484.

Compound 32j. Using the general procedure as described for 25a, compound 30j (30.3 mg, 0.089 mmol) was allowed to react for 4 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 32j as colorless solid (18.3 mg, 73 %): mp 133 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1567 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.95–2.01 (m, 2H, CH2), 3.70 (t, J = 5.6 Hz, 2H, CH2), 4.02 (t, J = 6.1 Hz, 2H, CH2), 6.49 (dd, J = 3.4, 1.7 Hz, 1H, Ar), 6.73 (d, J = 3.4 Hz, 1H, Ar), 7.21 (br s, 1H, NH), 7.33 (d, J = 1.7 Hz, 1H, Ar), 7.47–7.49 (m, 2H, Ar), 8.22 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 107.1, 112.0, 118.2, 121.6, 125.2, 129.3, 129.5, 132.7, 143.0, 146.3, 152.2, 153.3; Anal. calcd for C15H13N3OS: C, 63.58; H, 4.62; N, 14.83. Found: C, 63.40; H, 4.46; N, 14.72.

Synthesis of 9-(Benzofuran-2-yl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32k)

9-(Benzofuran-2-yl)- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30k) Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 2-benzofuranboronic acid (29.2 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 30k as colorless solid (54.3 mg, 93 %): mp 211 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1595 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.41 (s, 9H, 3 × CH3), 1.90–1.94 (m, 2H, CH2), 3.64 (t, J = 5.4 Hz, 2H, CH2), 3.88 (t, J = 6.0 Hz, 2H, CH2), 7.06 (s, 1H, Ar), 7.23 (t, J = 7.4 Hz, 1H, Ar), 7.30 (t, J = 7.4 Hz, 1H, Ar), 7.50 (d, J = 7.4 Hz, 1H, Ar), 7.58 (d, J = 7.4 Hz, 1H, Ar), 7.62–7.64 (m, 2H, Ar), 8.25 (d, J = 8.0 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.2, 45.4, 54.2, 103.0, 111.2, 120.4, 121.2, 122.3, 123.1, 124.9, 127.3, 128.9 (2C), 129.8, 132.0, 138.0, 147.5, 154.2, 155.0; HRMS (FAB): m/z calcd for C23H24N3OS [M + H]+ 390.1640; found: 390.1645.

Compound 32k. Using the general procedure as described for 25a, compound 30k (41.5 mg, 0.11 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 32k as pale yellow solid (30.5 mg, 85 %): mp 189–191 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1620 (C=N), 1565 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.95–2.00 (m, 2H, CH2), 3.70 (t, J = 5.4 Hz, 2H, CH2), 4.02 (t, J = 6.3 Hz, 2H, CH2), 7.07 (s, 1H, Ar), 7.22–7.25 (m, 1H, Ar), 7.31 (t, J = 7.2 Hz, 1H, Ar), 7.50–7.51 (m, 2H, Ar), 7.58 (d, J = 7.2 Hz, 1H, Ar), 7.65 (dd, J = 8.6, 1.1 Hz, 1H, Ar), 8.28 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.0, 43.8, 45.0, 103.4, 111.3, 119.4, 121.2, 122.6, 123.2, 125.1, 126.2, 128.8, 129.3, 129.6, 132.4, 146.2, 153.1, 153.9, 155.1; HRMS (FAB): m/z calcd for C19H16N3OS [M + H]+ 334.1014; found: 334.1017.

Synthesis of 3,4-Dihydro-9-(thiophen-3-yl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32l)

N -( tert -Butyl)-3,4-dihydro-9-(thiophen-3-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30l). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 3-thiopheneboronic acid (23.0 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 30l as colorless solid (54.0 mg, >99 %): mp 132–133 °C (from n-hexane); IR (neat) cm−1: 1592 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.89–1.95 (m, 2H, CH2), 3.63 (t, J = 5.6 Hz, 2H, CH2), 3.88 (t, J = 6.2 Hz, 2H, CH2), 7.32 (d, J = 2.0 Hz, 1H, Ar), 7.36–7.43 (m, 3H, Ar), 7.50 (dd, J = 2.7, 1.5 Hz, 1H, Ar), 8.21 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.9, 30.0 (3C), 45.1, 45.4, 54.2, 121.5, 121.9, 124.1, 126.0, 126.3, 126.6, 129.0, 129.6, 137.4, 138.2, 140.6, 147.7; HRMS (FAB): m/z calcd for C19H22N3S2 [M + H]+ 356.1255; found: 356.1253.

Compound 32l. Using the general procedure as described for 25a, compound 30l (37.6 mg, 0.11 mmol) was allowed to react for 2 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (4:1) gave the title compound 32l as colorless solid (25.9 mg, 82 %): mp 120–121 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1619 (C=N), 1569 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.96–2.01 (m, 2H, CH2), 3.70 (t, J = 5.4 Hz, 2H, CH2), 4.03 (t, J = 6.1 Hz, 2H, CH2), 7.23 (d, J = 1.1 Hz, 1H, Ar), 7.35–7.41 (m, 2H, Ar), 7.44 (dd, J = 8.3, 1.1 Hz, 1H, Ar), 7.51–7.52 (m, 1H, Ar), 8.24 (d, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 120.9, 121.8, 124.4, 125.0, 125.9, 126.7, 129.4 (2C), 138.0, 140.3, 146.5, 153.3; Anal. calcd for C15H13N3S2: C, 60.17; H, 4.38; N, 14.03. Found: C, 60.12; H, 4.11; N, 14.04.

Synthesis of 9-(Benzothiophen-2-yl)-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32m)

9-(Benzothiophen-2-yl)- N -( tert -butyl)-3,4-dihydro-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30m). Using the general procedure as described for 22l, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with 2-benzothiopheneboronic acid (32.0 mg, 0.18 mmol) for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 30m as colorless solid (44.8 mg, 74 %): mp 222–223 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1590 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.41 (s, 9H, 3 × CH3), 1.90–1.94 (m, 2H, CH2), 3.63 (t, J = 5.4 Hz, 2H, CH2), 3.88 (t, J = 6.3 Hz, 2H, CH2), 7.30–7.36 (m, 2H, Ar), 7.42 (d, J = 1.7 Hz, 1H, Ar), 7.52 (dd, J = 8.6, 1.7 Hz, 1H, Ar), 7.58 (s, 1H, Ar), 7.76 (dd, J = 7.2, 1.4 Hz, 1H, Ar), 7.82 (d, J = 8.0 Hz, 1H, Ar), 8.23 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.1, 45.4, 54.2, 120.7, 121.9, 122.3, 123.8, 123.9, 124.7, 124.8, 127.2, 129.0, 129.9, 136.0, 137.9, 139.7, 140.4, 142.3, 147.5; HRMS (FAB): m/z calcd for C23H24N3S2 [M + H]+ 406.1412; found: 406.1407.

Compound 32m. Using the general procedure as described for 25a, compound 30m (35.8 mg, 0.09 mmol) was allowed to react for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1 to 7:3) gave the title compound 32m as pale yellow solid (26.9 mg, 86 %): mp 198–200 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1615 (C=N), 1567 (C=N); 1H-NMR (500 MHz, CDCl3–CD3OD) δ: 1.95–2.00 (m, 2H, CH2), 3.69 (t, J = 5.4 Hz, 2H, CH2), 4.01 (t, J = 6.0 Hz, 2H, CH2), 7.25 (br s, 1H, NH), 7.32–7.37 (m, 3H, Ar), 7.54 (dd, J = 8.6, 1.7 Hz, 1H, Ar), 7.58 (s, 1H, Ar), 7.77 (t, J = 4.0 Hz, 1H, Ar), 7.82 (d, J = 7.4 Hz, 1H, Ar), 8.23 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3–CD3OD) δ: 20.9, 43.9, 44.9, 120.9, 121.0, 122.3, 123.9, 124.2, 124.7, 124.9, 125.9, 129.4, 129.6, 136.6, 139.7, 140.3, 141.8, 146.4, 153.2; HRMS (FAB): m/z calcd for C19H16N3S2 [M + H]+ 350.0786; found: 350.0785.

Synthesis of 3,4-Dihydro-9-(1H-pyrazol-1-yl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32n)

N -( tert -Butyl)-3,4-dihydro-9-(1 H -pyrazol-1-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30n). To a solution of N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol), pyrazole (12.3 mg, 0.18 mmol), CuCl (1.5 mg, 0.015 mmol) and K2CO3 (21.8 mg, 0.16 mol) in N-methylpyrrolidone (0.3 mL) was added acetylacetone (3.8 μL, 0.038 mmol) under an Ar atmosphere. After being stirred at 130 °C for 19 h, EtOAc was added. The organic layers were washed with H2O, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) to give the title compound 30n as colorless solid (39.8 mg, 71 %): mp 132–133 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1597 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.39 (s, 9H, 3 × CH3), 1.90–1.96 (m, 2H, CH2), 3.63 (t, J = 5.6 Hz, 2H, CH2), 3.88 (t, J = 6.2 Hz, 2H, CH2), 6.48 (dd, J = 2.7, 1.8 Hz, 1H, Ar), 7.47 (dd, J = 8.8, 2.2 Hz, 1H, Ar), 7.56 (d, J = 2.2 Hz, 1H, Ar), 7.73 (d, J = 1.8 Hz, 1H, Ar), 7.94 (d, J = 2.7 Hz, 1H, Ar), 8.28 (d, J = 8.8 Hz, 1H, Ar); 13C-NMR (100 MHz,CDCl3) δ: 21.8, 30.0 (3C), 45.0, 45.4, 54.2, 108.2, 114.3, 115.9, 125.4, 126.7, 129.9, 130.8, 137.7, 141.0, 141.7, 147.3; HRMS (FAB): m/z calcd for C18H22N5S [M + H]+ 340.1596; found: 340.1598.

Compound 32n. Using the general procedure as described for 25a, compound 30n (21.6 mg, 0.064 mmol) was allowed to react for 1 h. Purification by preparative TLC over aluminum oxide with CHCl3 gave the title compound 32n as colorless solid (16.2 mg, 89 %): mp 158–159 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1615 (C=N), 1561 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.96–2.02 (m, 2H, CH2), 3.70 (t, J = 5.6 Hz, 2H, CH2), 4.03 (t, J = 6.2 Hz, 2H, CH2), 6.49 (dd, J = 2.6, 1.8 Hz, 1H, Ar), 7.27 (s, 1H, NH), 7.48–7.51 (m, 2H, Ar), 7.74 (d, J = 1.5 Hz, 1H, Ar), 7.95 (d, J = 2.7 Hz, 1H, Ar), 8.31 (d, J = 9.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.0, 43.8, 44.9, 108.4, 113.3, 116.1, 124.3, 126.7, 130.3, 130.6, 141.3, 141.8, 145.9, 152.8; HRMS (FAB): m/z calcd for C14H14N5S [M + H]+ 284.0970; found: 284.0966.

Synthesis of 3,4-Dihydro-9-(1H-imidazol-1-yl)-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (32o)

N -( tert -Butyl)-3,4-dihydro-9-(1 H -imidazol-1-yl)-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (30o). Using the general procedure as described for 30n, N-(tert-butyl)-9-bromo-3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine 22k (52.8 mg, 0.15 mmol) was allowed to react with imidazole (12.3 mg, 0.18 mmol) for 3 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1 to 0:1) gave the title compound 30o as colorless solid (25.8 mg, 51 %): mp 170–171 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1599 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.40 (s, 9H, 3 × CH3), 1.91–1.96 (m, 2H, CH2), 3.64 (t, J = 5.6 Hz, 2H, CH2), 3.89 (t, J = 6.2 Hz, 2H, CH2), 7.15 (d, J = 2.3 Hz, 1H, Ar), 7.22 (dd, J = 8.8, 2.3 Hz, 1H, Ar), 7.22 (s, 1H, Ar), 7.30 (s, 1H, Ar), 7.90 (s, 1H, Ar), 8.32 (d, J = 8.8 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.8, 30.0 (3C), 45.0, 45.5, 54.3, 116.2, 117.7, 118.4, 126.5, 130.5, 130.8, 131.3, 135.3, 136.9, 138.4, 146.9; HRMS (FAB): m/z calcd for C18H22N5S [M + H]+ 340.1596; found: 340.1598.

Compound 32o. Using the general procedure as described for 25a, compound 30o (20.6 mg, 0.061 mmol) was allowed to react for 1 h. Purification by preparative TLC over aluminum oxide with EtOAc–MeOH (9:1) gave the title compound 32o as colorless solid (9.7 mg, 56 %): mp 183–185 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1622 (C=N), 1561 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.97-2.03 (m, 2H, CH2), 3.71 (t, J = 5.7 Hz, 2H, CH2), 4.04 (t, J = 6.1 Hz, 2H, CH2), 7.07 (d, J = 2.2 Hz, 1H, Ar), 7.22 (s, 1H, Ar), 7.25 (dd, J = 8.8, 2.2 Hz, 1H, Ar), 7.29 (s, 1H, Ar), 7.89 (s, 1H, Ar), 8.36 (d, J = 8.8 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 20.9, 43.8, 44.9, 115.2, 117.7, 118.6, 125.5, 130.9, 131.0, 131.1, 135.3, 138.8, 145.6, 152.2; HRMS (FAB): m/z calcd for C14H14N5S [M + H]+ 284.0970; found: 284.0966.

Synthesis of 2,3-Dihydro-5H-imidazo[1,2-c][1,3]benzothiazin-5-imine (36a)

Using the general procedure as described for 25a, N-(tert-butyl)-2,3-dihydroimidazo[1,2-c][1,3]benzothiazin-5-imine 35a (18.4 mg, 0.07 mmol) was allowed to react for 12 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over silica gel with n-hexane–EtOAc (1:1) gave the title compound 36a as colorless solid (11.1 mg, 78 %): mp 176–178 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1621 (C=N), 1585 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 4.11 (4H, s, 2 × CH2), 5.82 (1H, br s, NH), 7.12 (1H, d, J = 8.0 Hz, Ar), 7.24-7.28 (1H, m, Ar), 7.38–7.42 (1H, m, Ar), 8.20 (1H, dd, J = 7.7, 1.4 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 47.3, 52.9, 120.8, 123.8, 126.5, 129.1, 132.0, 132.4, 150.0, 154.0; HRMS (FAB): m/z calcd for C10H10N3S [M + H]+ 204.0595; found: 204.0600.

Synthesis of 6H,8H-Quinazolino[3,2-c][1,3]benzothiazin-6-imine (36b)

N -( tert -Butyl)-6 H, 8 H -quinazolino[3,2- c ][1,3]benzothiazin-6-imine (35b). To a solution of 2-fluorobenzaldehyde (1.41 g, 11.39 mmol) in t-BuOH (38 mL) was added 2-aminobenzylamine 33b (1.53 g, 12.53 mmol). The mixture was stirred at 80 °C for 30 min, and then K2CO3 (4.73 g, 34.18 mmol) and I2 (3.61 g, 14.24 mmol) were added. After being stirred at same temperature for 4 h, the mixture was quenched with sat. Na2SO3. The organic layer was separated and concentrated. The resulting solid was dissolved with H2O and CHCl3, and then pH was adjusted to 12–14 with 5 N NaOH. The whole was extracted with CHCl3. The extract was washed with brine, dried over Na2SO4. To a mixture of resulting residue in DMAc (7.4 mL) were added KOt-Bu (496 mg, 4.42 mmol) and tert-butylisothiocyanate (0.56 mL, 4.42 mmol) under an N2 atmosphere. After being stirred at 80 °C for 2.5 h, sat. NH4Cl was added. The whole was extracted with EtOAc. The extract was washed with brine, and dried over Na2SO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (1:0 to 9:1) to give the title compound 35b as yellow solid (114.1 mg, 3.1 % over 2 steps): mp 92.2 °C; IR (neat) cm−1: 1588 (C=N); 1H-NMR (300 MHz, CDCl3) δ: 1.42 (9H, s, 3 × CH3), 5.10 (2H, s, CH2), 7.08–7.23 (3H, m, Ar), 7.27–7.40 (4H, m, Ar), 8.43 (1H, dd, J = 8.0, 1.4 Hz, Ar); 13C-NMR (75 MHz, CDCl3) δ: 29.9 (3C), 46.2, 54.7, 124.0, 124.8, 124.9, 125.4, 125.8, 126.4, 127.7, 128.3, 129.0, 129.4, 130.7, 138.3, 141.1, 148.3; Anal. calcd for C19H19N3S: C, 70.99; H, 5.96; N, 13.07. Found: C, 71.05; H, 5.99; N, 12.91.

Compound 36b. TFA (0.5 mL) was added to 35b (100 mg, 0.311 mmol). After being stirred under reflux for 30 min, the mixture was added dropwise to Et3N at 0 °C to adjust pH to 8–9. The whole was extracted with EtOAc. The extract was washed with sat. NaHCO3 aq., brine, and dried over Na2SO4. After concentration, the residue was purified by preparative TLC over aluminum oxide with n-hexane–EtOAc (9:1) to give the title compound 36b as colorless solid (13 mg, 16 %): mp 133–135 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1594 (C=N), 1541 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 5.27 (2H, s, CH2), 7.08–7.13 (2H, m, Ar), 7.16 (1H, t, J = 7.2 Hz, Ar), 7.26–7.34 (3H, m, Ar), 7.39 (1H, td, J = 6.9, 1.1 Hz, Ar), 7.59 (1H, br s, NH), 8.50 (1H, d, J = 8.0 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 45.1, 123.0, 123.8, 125.4, 125.6, 126.3, 126.5, 126.6, 128.5, 129.2, 129.5, 131.1, 140.1, 146.3, 153.3; HRMS (FAB): m/z calcd for C15H12N3S [M + H]+ 266.0752; found: 266.0750.

Synthesis of (±)-3,4-Dihydro-3-methyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (36c)

2-(2-Fluorophenyl)-5-methyl-1,4,5,6-tetrahydropyrimidine (34c). 2-Fluorobenzaldehyde (0.62 g, 5.0 mmol) was subjected to the general procedure for 18j using 2-methylpropylenediamine 33c (0.48 g, 5.5 mmol) to give the title compound 34c as colorless crystals (0.72 g, 75 %): mp 98–99 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1628 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.01 (3H, d, J = 6.9 Hz, CH3), 1.92–1.99 (1H, m, CH), 3.06 (2H, dd, J = 13.2, 9.7 Hz, 2 × CH), 3.52 (2H, dd, J = 13.2, 3.4 Hz, 2 × CH), 5.27 (1H, br s, NH), 7.04 (1H, dd, J = 11.7, 8.3 Hz, Ar), 7.15 (1H, t, J = 7.4 Hz, Ar), 7.30–7.35 (1H, m, Ar), 7.81 (1H, td, J = 7.4, 1.7 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 16.8, 25.2, 49.4 (2C), 115.9 (d, J = 24.0 Hz), 124.2, 124.3 (d, J = 3.6 Hz), 130.6 (d, J = 3.6 Hz), 130.8 (d, J = 8.4 Hz), 151.3, 160.1 (d, J = 247.1 Hz); 19F-NMR (500 MHz, CDCl3) δ: −117.1; HRMS (FAB): m/z calcd for C11H14FN2 [M + H]+ 193.1141; found: 193.1136.

(±)- N -(-(tert -Butyl)-3,4-dihydro-3-methyl-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (35c). Using the general procedure as described for 22e, compound 34c (384.5 mg, 2.0 mmol) was allowed to react at 80 °C for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 95:5) gave the title compound 35c as colorless solid (288.4 mg, 50 %): mp 60–62 °C (from n-hexane); IR (neat) cm−1: 1598 (C=N), 1570 (C=N); 13C-NMR (500 MHz, CDCl3) δ: 1.05 (3H, d, J = 6.3 Hz, CH3), 1.39 (9H, s, 3 × CH3), 1.91–1.99 (1H, m, CH), 3.09–3.17 (2H, m, CH2), 3.72 (1H, dt, J = 15.5, 3.7 Hz, CH), 4.19 (1H, dt, J = 13.7, 3.7 Hz, CH), 7.11 (1H, d, J = 8.0 Hz, Ar), 7.19 (1H, t, J = 8.0 Hz, Ar), 7.30 (1H, t, J = 8.0 Hz, Ar), 8.19 (1H, d, J = 8.0 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 16.7, 26.9, 30.0 (3C), 51.6, 52.4, 54.2, 124.4, 126.0, 127.7, 128.5, 129.1, 130.1, 138.4, 147.6; HRMS (FAB): m/z calcd for C16H22N3S [M + H]+ 288.1534; found: 288.1535.

Compound 36c. Using the general procedure as described for 25a, compound 35c (57.5 mg, 0.20 mmol) was allowed to react for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1) gave the title compound 36c as colorless solid (36.7 mg, 79 %): mp 82–84 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1621 (C=N), 1574 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.09 (3H, d, J = 6.3 Hz, CH3), 1.96–2.08 (1H, m, CH), 3.19 (1H, dd, J = 15.8, 10.6 Hz, CH), 3.27 (1H, dd, J = 13.0, 10.6 Hz, CH), 3.80 (1H, ddd, J = 15.8, 4.5, 3.2 Hz, CH), 4.37 (1H, ddd, J = 13.0, 4.5, 3.2 Hz, CH), 7.04 (1H, d, J = 7.4 Hz, Ar), 7.18–7.25 (2H, m, Ar, NH), 7.33 (1H, td, J = 7.4, 1.4 Hz, Ar), 8.23 (1H, dd, J = 8.3, 1.4 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 16.4, 26.1, 49.9, 52.2, 123.5, 126.3, 126.6, 128.8, 128.9, 130.6, 146.2, 153.4; Anal. calcd for C12H13N3S: C, 62.31; H, 5.66; N, 18.17. Found: C, 62.04; H, 5.75; N, 17.88.

Synthesis of 3,4-Dihydro-3,3-dimethyl-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine (36d)

2-(2-Fluorophenyl)-5,5-dimethyl-1,4,5,6-tetrahydropyrimidine (34d). 2-Fluorobenzaldehyde (0.62 g, 5.0 mmol) was subjected to the general procedure for 18j using 2,2-dimethylpropylenediamine 33d (0.56 g, 5.5 mmol) to give the title compound 34d as colorless crystals (0.82 g, 79 %): mp 150–153 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1629 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.02 (6H, s, 2 × CH3), 3.13 (4H, s, 2 × CH2), 5.14 (1H, br s, NH), 7.05 (1H, ddd, J = 11.7, 7.8, 1.0 Hz, Ar), 7.15 (1H, td, J = 7.8, 1.0 Hz, Ar), 7.30–7.35 (1H, m, Ar), 7.81 (1H, td, J = 7.8, 2.0 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 25.0 (2C), 26.2, 54.3 (2C), 115.8 (d, J = 23.2 Hz), 124.2, 124.3 (d, J = 3.3 Hz), 130.6 (d, J = 4.1 Hz), 130.8 (d, J = 9.1 Hz), 150.5 (d, J = 1.7 Hz), 160.2 (d, J = 247.5 Hz); 19F-NMR (500 MHz, CDCl3) δ: −117.3; HRMS (FAB): m/z calcd for C12H16FN2 [M + H]+ 207.1298; found: 207.1299.

N -( tert -Butyl)-3,4-dihydro-3,3-dimethyl-2 H, 6 H -pyrimido[1,2- c ][1,3]benzothiazin-6-imine (35d). Using the general procedure as described for 22e, compound 34d (412.5 mg, 2.0 mmol) was allowed to react at 80 °C for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 35d as colorless solid (236.6 mg, 39 %): mp 70–72 °C (from n-hexane); IR (neat) cm−1: 1602 (C=N), 1570 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.01 (6H, s, 2 × CH3), 1.39 (9H, s, 3 × CH3), 3.33 (2H, s, CH2), 3.58 (2H, s, CH2), 7.12 (1H, d, J = 8.0 Hz, Ar), 7.20 (1H, t, J = 8.0 Hz, Ar), 7.31 (1H, td, J = 8.0, 1.1 Hz, Ar), 8.21 (1H, dd, J = 8.0, 1.1 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 24.8 (2C), 28.5, 29.9 (3C), 54.2, 55.7, 57.4, 124.5, 126.0, 127.5, 128.5, 129.1, 130.1, 138.7, 146.7; HRMS (FAB): m/z calcd for C17H24N3S [M + H]+ 302.1691; found: 302.1695.

Compound 36d. Using the general procedure as described for 25a, compound 35d (60.3 mg, 0.20 mmol) was allowed to react for 1 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:1) gave the title compound 36d as colorless solid (42.0 mg, 86 %): mp 113–114 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1627 (C=N), 1575 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.05 (6H, s, 2 × CH3), 3.41 (2H, s, CH2), 3.74 (2H, s, CH2), 7.05 (1H, dd, J = 7.6, 1.1 Hz, Ar), 7.21–7.25 (2H, m, Ar, NH), 7.34 (1H, td, J = 7.6, 1.4 Hz, Ar), 8.26 (1H, dd, J = 8.3, 1.4 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 24.6 (2C), 27.9, 54.0, 57.2, 123.5, 126.3, 126.3, 128.8, 128.9, 130.6, 145.3, 153.8; HRMS (FAB): m/z calcd for C13H16N3S [M + H]+ 246.1065; found: 246.1069.

Synthesis of 2,3,4,5-Tetrahydro-7H-1,3-diazepino[1,2-c][1,3]benzothiazin-7-imine (36e)

N -( tert -Butoxycarbonyl)-2-(2-fluorophenyl)-4,5,6,7-tetrahydro-1,3-diazepine (37). To a solution of 2-fluorobenzaldehyde (2.48 g, 20.0 mmol) in t-BuOH (188 mL) was added 1,4-diaminobutane 33e (2.21 mL, 22.0 mmol). The mixture was stirred at 70 °C for 30 min, and then K2CO3 (8.29 g, 60.0 mmol) and I2 (6.35 g, 25 mmol) were added. After being stirred at same temperature for 3 h, the mixture was quenched with sat. Na2SO3. The organic layer was separated and concentrated. The resulting solid was dissolved with H2O, and then pH was adjusted to 12–14 with 2 N NaOH. The whole was extracted with CHCl3, and dried over Na2SO4. After concentration, Et3N (8.67 mL, 60.0 mmol) and Boc2O (13.8 mL, 60.0 mmol) were added to the solution of residue in CH2Cl2 (100 mL). After being stirred for 30 min at rt, sat. NaHCO3 was added. After being stirred at rt for 1 h, the whole was extracted with CHCl3. The extract was washed with brine, and dried over MgSO4. After concentration, the residue was purified by column chromatography over silica gel with n-hexane–EtOAc (4:1) to give the title compound 37 as colorless solid (2.18 g, 37 %): mp 63–65 °C (from n-hexane); IR (neat) cm−1: 1710 (C=O), 1631 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.14 (9H, s, 3 × CH3), 1.66–1.70 (2H, m, CH2), 1.78–1.83 (2H, m, CH2), 3.61 (2H, br s, CH2), 3.76 (2H, t, J = 5.2 Hz, CH2), 7.03 (1H, dd, J = 11.2, 8.3 Hz, Ar), 7.15 (1H, td, J = 7.7, 1.1 Hz, Ar), 7.33–7.38 (1H, m, Ar), 7.60 (1H, t, J = 7.7 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 23.2, 26.4, 27.7 (3C), 44.9, 50.7, 81.1, 115.7 (d, J = 21.6 Hz), 124.0 (d, J = 2.4 Hz), 126.5, 130.9 (d, J = 2.4 Hz), 131.1 (d, J = 8.4 Hz), 152.8, 154.8, 160.5 (d, J = 250.7 Hz); 19F-NMR (500 MHz, CDCl3) δ: −118.9; HRMS (FAB) m/z calcd for C16H22FN2O2 [M + H]+ 293.1665; found: 293.1669.

2-(2-Fluorophenyl)-4,5,6,7-tetrahydro-1 H -1,3-diazepine (34e). To a solution of 37 (877.1 mg, 3.0 mmol) in CH2Cl2 (6.0 mL) was added TFA (6.0 mL). The mixture was stirred under reflux for 2 h, mixture was washed with 2 N NaOH. The organic phase was dried over MgSO4. After concentration, the residue was recrystallized from CHCl3–n-hexane to give the title compound 34e as colorless crystals (461.2 mg, 80 %): mp 92 °C; IR (neat) cm−1: 1627 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.80–1.83 (4H, m, 2 × CH2), 3.48 (4H, br s, 2 × CH2), 4.86 (1H, br s, NH), 7.02–7.06 (1H, m, Ar), 7.12 (1H, td, J = 7.7, 1.1 Hz, Ar), 7.30–7.34 (1H, m, Ar), 7.63 (1H, td, J = 7.7, 1.7 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 28.4 (2C), 47.9 (2C), 115.7 (d, J = 22.8 Hz), 124.2 (d, J = 3.6 Hz), 127.0 (d, J = 12.0 Hz), 130.9 (d, J = 8.4 Hz), 131.2 (d, J = 3.6 Hz), 157.2, 160.4 (d, J = 247.1 Hz); 19F-NMR (500 MHz, CDCl3) δ: −117.7; HRMS (FAB) m/z calcd for C11H14FN2 [M + H]+ 193.1141; found: 193.1140.

N -( tert -Butyl)-7 H -2,3,4,5-tetrahydro-1,3-diazepino[1,2- c ][1,3]benzothiazin-7-imine (35e). Using the general procedure as described for 25e, compound 34e (192.2 mg, 1.0 mmol) was allowed to react at rt overnight. Purification by flash chromatography over silica gel with n-hexane–EtOAc (4:1) gave the title compound 35e as a yellow oil (50.3 mg, 18 %): IR (neat) cm−1: 1588 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.37 (9H, s, 3 × CH3), 1.87−1.93 (4H, m, 2 × CH2), 3.82 (2H, t, J = 5.4 Hz, CH2), 3.88 (2H, t, J = 5.4 Hz, CH2), 7.16−7.23 (2H, m, Ar), 7.26−7.31 (1H, m, Ar), 7.84 (1H, d, J = 7.1 Hz, Ar); 13C-NMR (100 MHz, CDCl3) δ: 23.3, 24.5, 30.2 (3C), 48.3, 49.2, 53.8, 124.9, 126.3, 127.0, 129.4, 129.7, 133.5, 140.0, 152.2; HRMS (FAB) m/z calcd for C16H22N3S [M + H]+ 288.1534; found: 288.1540.

Compound 36e. Using the general procedure as described for 25a, compound 35e (50.3 mg, 0.18 mmol) was allowed to react for 2 h. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (4:1 to 2:1) gave the title compound 36e as a colorless oil (11.3 mg, 27 %): IR (neat) cm−1: 1638 (C=N), 1578 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.94−2.01 (4H, m, 2 × CH2), 3.92 (2H, t, J = 5.5 Hz, CH2), 3.96 (2H, t, J = 5.6 Hz, CH2), 7.00 (1H, br s, NH), 7.12−7.14 (1H, m, Ar), 7.23−7.28 (1H, m, Ar), 7.31−7.35 (1H, m, Ar), 7.90 (1H, dd, J = 7.8, 1.5 Hz, Ar); 13C-NMR (125 MHz, CDCl3) δ: 23.3, 24.3, 47.5, 49.0, 124.2, 126.6, 127.5, 129.3, 129.9, 132.0, 151.0, 155.5; HRMS (FAB) m/z calcd for C12H14N3S [M + H]+ 232.0908; found: 232.0906.

Synthesis of 9-Bromo-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,1′-cyclohexan)-6(4H)-imine (49)

Cyclohexane-1,1-dicarbonitrile (42). To a solution of malononitrile (660.6 mg, 10.0 mmol) in DMF (25.0 mL) was added DBU (2.99 mL, 20.0 mmol). After being stirred at 50 °C for 2 h, a solution of 1,5-dibromopentane 38 (1.35 mL, 10.0 mmol) in DMF (10.0 mL) was added to the reaction mixture. After being stirred at the same temperature for additional 5 h, EtOAc was added. The mixture was washed with 5 % aq. NaHCO3, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (3:1). The resulting solid was recrystalized from CHCl3–n-hexane to give the title compound 42 as colorless crystals (801.8 mg, 60 %): mp 62 °C, IR (neat) cm−1: 2254 (C ≡ N); 1H-NMR (400 MHz, CDCl3) δ: 1.51–1.57 (m, 2H, CH2), 1.73–1.78 (m, 4H, 2 × CH2), 2.13 (t, J = 5.9 Hz, 4H, 2 × CH2); 13C-NMR (100 MHz, CDCl3) δ: 21.6 (2C), 23.9, 32.4, 34.6 (2C), 115.9 (2C); MS (FAB) m/z (%): 135 (MH+, 100).

3-(4-Bromo-2-fluorophenyl)-2,4-diazaspiro[5.5]undec-2-ene (45). To a solution of 42 (134.2 mg, 1.0 mmol) in THF (2.5 mL) was added BH3-THF in THF (5.0 mL, 5.0 mmol, 1.0 M) at 0 °C under an Ar atmosphere. The mixture was warmed to rt. After being stirred at 65 °C for 5 h, the reaction mixture was cooled to 0 °C, and was added 1 N HCl. After being stirred at rt for 1 h, the mixture was basified with 2 N NaOH. The whole was extracted with CHCl3 and dried over MgSO4. After concentration, the residue was dissolved in t-BuOH (10.0 mL), and 4-bromo-2-fluorobenzaldehyde (203.0 mg, 1.0 mmol) was added. After being stirred at 70 °C for 30 min, K2CO3 (414.6 mg, 3.0 mmol) and I2 (317.3 mg, 1.25 mmol) were added. After being stirred at same temperature for 3 h, the reaction mixture was quenched with sat. Na2SO3 until the iodine color almost disappeared. The reaction mixture was basified with 2 N NaOH. The whole was extracted with CHCl3, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with EtOAc–MeOH (1:0 to 95:5) gave the title compound 45 as colorless solid (200.1 mg, 62 %): mp 204–205 °C (from CHCl3–n-hexane), IR (neat) cm−1: 1626 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.35–1.37 (m, 4H, 2 × CH2), 1.47–1.49 (m, 6H, 3 × CH2), 3.20 (s, 4H, 2 × CH2), 5.07 (s, 1H, NH), 7.23 (dd, J = 11.2, 2.0 Hz, 1H, Ar), 7.28 (dd, J = 8.3, 2.0 Hz, 1H, Ar), 7.69 (t, J = 8.3 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.7 (2C), 26.5, 28.8 (2C), 33.5, 52.2 (2C), 119.4 (d, J = 27.6 Hz), 123.1 (d, J = 12.0 Hz), 123.5 (d, J = 10.8 Hz), 127.7 (d, J = 3.6 Hz), 131.8 (d, J = 3.6 Hz), 149.9, 159.8 (d, J = 251.9 Hz); 19F-NMR (500 MHz, CDCl3) δ: −114.6; HRMS (FAB): m/z calcd for C15H19BrFN2 [M + H]+ 325.0716; found: 325.0724.

9-Bromo- N -( tert -butyl)-2 H -spiro(benzo[ e ]pyrimido[1,2- c ][1,3]thiazine-3,1′-cyclohexan)-6(4 H )-imine (48). To a mixture of compound 45 (164.5 mg, 0.51 mmol) and NaH (40.8 mg, 1.02 mmol; 60 % oil suspension) in DMF (3.3 mL) was added t-BuNCS (129.4 μL, 1.02 mmol) under an Ar atmosphere. After being stirred at rt overnight, the reaction mixture was warmed at 60 °C. After being stirred at this temperature for 1 h, EtOAc was added. The resulting solution was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 48 as colorless solid (180.1 mg, 84 %): mp 118–119 °C (from n-hexane); IR (neat) cm−1: 1578 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.32–1.37 (m, 4H, 2 × CH2), 1.38 (s, 9H, 3 × CH3), 1.43–1.52 (m, 6H, 3 × CH2), 3.38 (s, 2H, CH2), 3.71 (s, 2H, CH2), 7.26–7.31 (m, 2H, Ar), 8.04 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 21.8 (2C), 26.5, 29.9 (3C), 31.2, 33.4 (2C), 52.5, 54.2, 55.9, 124.3, 126.5, 126.8, 129.1, 130.0, 130.9, 137.6, 146.2; HRMS (FAB): m/z calcd for C20H27BrN3S [M + H]+ 420.1109; found: 420.1117.

Compound 49. Using the general procedure as described for 25a, 48 (124.7 mg, 0.3 mmol) was allowed to react under reflux for 2.5 h with TFA (3.0 mL) and MS4Å (0.45 g). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 49 as pale yellow solid (89.8 mg, 82 %): mp 130 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1626 (C=N), 1572 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.37–1.55 (m, 10H, 5 × CH2), 3.46 (s, 2H, CH2), 3.82 (s, 2H, CH2), 7.21 (d, J = 2.0 Hz, 1H, Ar), 7.24 (s, 1H, NH), 7.33 (dd, J = 8.8, 2.0 Hz, 1H, Ar), 8.10 (d, J = 8.8 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.6 (2C), 26.3, 30.6, 33.3 (2C), 51.4, 55.4, 125.0, 125.3, 125.9, 129.5, 130.5, 130.7, 144.8, 152.7; HRMS (FAB): m/z calcd for C16H19BrN3S [M + H]+ 364.0483; found: 364.0485.

Synthesis of 9-Bromo-2′,3′,5′,6′-tetrahydro-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-pyran)-6(4H)-imine (51)

Dihydro-2 H -pyran-4,4(3 H )-dicarbonitrile (43). To a solution of malononitrile (660.6 mg, 10.0 mmol) in DMF (25.0 mL) was added DBU (2.99 mL, 20.0 mmol). After stirring at 50 °C for 2 h, the reaction mixture was added a solution of bis(2-chloroethyl)ether 39 (1.18 mL, 10.0 mmol) in DMF (10.0 mL). After being stirred at same temperature for 5 h, EtOAc was added. The mixture was washed with 5 % aq. NaHCO3, and dried over MgSO4. The filtrate was concentrated. The residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (3:1). The resulting solid was recrystalized from CHCl3–n-hexane to give the title compound 43 as colorless crystals (112.2 mg, 8 %): mp 96 °C, IR (neat) cm−1: 2253 (C ≡ N); 1H-NMR (400 MHz, CDCl3) δ: 2.24 (t, J = 5.2 Hz, 4H, 2 × CH2), 3.87 (t, J = 5.2 Hz, 4H, 2 × CH2); 13C-NMR (100 MHz, CDCl3) δ: 30.2, 33.8 (2C), 63.0 (2C), 114.9 (2C); MS (FAB) m/z (%): 137 (MH+, 100).

3-(4-Bromo-2-fluorophenyl)-9-oxa-2,4-diazaspiro[5.5]undec-2-ene (46). Using the general procedure as described for 45, 43 (84.1 mg, 0.62 mmol) was allowed to react. Purification by flash chromatography over aluminum oxide with EtOAc–MeOH (1:0 to 95:5) gave the title compound 46 as colorless solid (21.4 mg, 11 %): mp 200–201 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1626 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.52 (t, J = 5.4 Hz, 4H, 2 × CH2), 3.31 (s, 4H, 2 × CH2), 3.72 (t, J = 5.4 Hz, 4H, 2 × CH2), 4.03 (br s, 1H, NH), 7.25 (dd, J = 11.7, 2.0 Hz, 1H, Ar), 7.31 (dd, J = 8.6, 2.0 Hz, 1H, Ar), 7.70 (t, J = 8.6 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3) δ: 27.0, 33.3 (2C), 51.4 (2C), 63.7 (2C), 119.5 (d, J = 27.6 Hz), 122.5 (d, J = 13.2 Hz), 124.0 (d, J = 9.6 Hz), 127.9 (d, J = 3.6 Hz), 131.7 (d, J = 3.6 Hz), 150.4, 159.7 (d, J = 251.9 Hz); HRMS (FAB): m/z calcd for C14H17BrFN2O [M + H]+ 327.0508; found: 327.0512.

9-Bromo- N -( tert -butyl)-2′,3′,5′,6′-tetrahydro-2 H -spiro(benzo[ e ]pyrimido[1,2- c ][1,3]thiazine-3,4′-pyran)-6(4 H )-imine (50). Using the general procedure as described for 48, 46 (21.4 mg, 0.065 mmol) was allowed to react at rt overnight. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) gave the title compound 50 as colorless solid (21.5 mg, 78 %): mp 148–149 °C (from n-hexane); IR (neat) cm−1: 1578 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.38 (s, 9H, 3 × CH3), 1.48–1.53 (m, 4H, 2 × CH2), 3.48 (s, 2H, CH2), 3.71–3.74 (m, 4H, 2 × CH2), 3.84 (s, 2H, CH2), 7.29–7.33 (m, 1H, Ar), 7.37 (d, J = 4.1 Hz, 1H, Ar), 8.05 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (125 MHz, CDCl3–CD3OD) δ: 29.4, 29.9 (3C), 33.1 (2C), 51.4, 54.3, 55.5, 63.8 (2C), 124.6, 126.1, 126.9, 129.3, 130.0, 130.9, 137.6, 146.4; HRMS (FAB): m/z calcd for C19H25BrN3OS [M + H]+ 422.0902; found:422.0898.

Compound 51. Using the general procedure as described for 25a, 50 (21.4 mg, 0.065 mmol) was allowed to react under reflux for 2.5 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 51 as colorless solid (12.3 mg, 66 %): mp 212–214 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1626 (C=N), 1573 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.54 (t, J = 5.4 Hz, 4H, 2 × CH2), 3.56 (s, 2H, CH2), 3.74 (t, J = 5.4 Hz, 4H, 2 × CH2), 3.93 (s, 2H, CH2), 7.22 (d, J = 2.0 Hz, 1H, Ar), 7.31 (br s, 1H, NH), 7.34 (dd, J = 8.8, 2.0 Hz, 1H, Ar), 8.10 (d, J = 8.8 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3–CD3OD) δ: 28.6, 32.9 (2C), 50.7, 54.6, 63.4 (2C), 124.7, 125.3, 125.9, 129.6, 130.3, 130.5, 145.4, 152.9; HRMS (FAB): m/z calcd for C15H17BrN3OS [M + H]+ 366.0276; found: 366.0280.

Synthesis of 9-Bromo-1′-(4-methoxybenzyl)-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-piperidin)-6(4H)-imine (53a)

Bis(2-chloroethyl)- N -(4-methoxybenzyl)amine (41). To a suspension of bis(2-chloroethyl)amine hydrochloride 40 (8.92 g, 50.0 mmol) in CH2Cl2 (300 mL) were added Et3N (2.89 mL, 100.0 mmol) and 4-methoxybenzoyl chloride (6.77 mL, 50.0 mmol). After being stirred at rt for 2 h, the reaction mixture was washed with 1 N HCl, sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was dissolved in anhydrous Et2O (250 mL), and LiAlH4 (2.1 g, 55.0 mmol) was slowly added to the mixture at 0 °C under an Ar atmosphere. After being stirred at rt overnight, the reaction mixture was quenched by the addition of water, 2 N NaOH, and water. The mixture was dried over MgSO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (19:1) to give the title compound 41 as colorless oil (9.88 g, 75 %): 1H-NMR (400 MHz, CDCl3) δ: 2.90 (t, J = 7.1 Hz, 4H, 2 × CH2), 3.48 (t, J = 7.1 Hz, 4H, 2 × CH2), 3.67 (s, 2H, CH2), 3.80 (s, 3H, CH3), 6.86 (d, J = 8.5 Hz, 2H, Ar), 7.24 (d, J = 8.5 Hz, 2H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 42.0 (2C), 55.2, 56.2 (2C), 58.6, 113.8 (2C), 129.7 (2C), 130.7, 158.9; MS (FAB) m/z (%): 262 (MH+, 100).

1-(4-Methoxybenzyl)piperidine-4,4-dicarbonitrile (44). To a solution of malononitrile (2.49 g, 37.7 mmol) in DMF (94.3 mL) was added K2CO3 (5.73 mg, 41.5 mmol). After being stirred at 65 °C for 2 h, a solution of 41 (9.88 mg, 37.7 mmol) in DMF (37.7 mL) was added. After being stirred at same temperature for 5 h, EtOAc was added. The mixture was washed with 5 % aq. NaHCO3, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (2:1) to give the title compound 44 as yellow oil (8.13 g, 85 %): IR (neat) cm−1: 2248 (C ≡ N); 1H-NMR (400 MHz, CDCl3) δ: 2.22 (t, J = 5.4 Hz, 4H, 2 × CH2), 2.61 (br s, 4H, 2 × CH2), 3.48 (s, 2H, CH2), 3.80 (s, 3H, CH2), 6.86 (d, J = 8.5 Hz, 2H, Ar), 7.19 (d, J = 8.8 Hz, 2H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 31.1, 34.1 (2C), 48.5 (2C), 55.2, 61.9, 113.8 (2C), 115.4 (2C), 129.2, 130.1 (2C), 159.0; HRMS (FAB): m/z calcd for C15H18N3O [M + H]+ 256.1450; found: 256.1454.

3-(4-Bromo-2-fluorophenyl)-9-(4-methoxybenzyl)-2,4,9-triazaspiro[5.5]undec-2-ene (47). Using the general procedure as described for 45, 44 (4.05 g, 15.9 mmol) was allowed to react. Purification by flash chromatography over aluminum oxide with EtOAc–MeOH (1:0 to 95:5) to give the title compound 47 as colorless solid (752.6 mg, 11 %): mp 179–181 °C (from CHCl3–n-hexane), IR (neat) cm−1: 1630 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.45 (t, J = 5.4 Hz, 4H, 2 × CH2), 2.35 (t, J = 5.4 Hz, 4H, 2 × CH2), 3.16 (s, 4H, 2 × CH2), 3.40 (s, 2H, CH2), 3.73 (s, 3H, CH3), 4.63 (s, 1H, NH), 6.78 (d, J = 8.6 Hz, 2H, Ar), 7.14–7.23 (m, 4H, Ar), 7.62 (t, J = 8.3 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 27.3, 32.8 (2C), 49.1 (2C), 51.4 (2C), 55.2, 62.7, 113.5 (2C), 119.4 (d, J = 27.3 Hz), 122.7 (d, J = 12.4 Hz), 123.7 (d, J = 9.9 Hz), 127.8 (d, J = 3.3 Hz), 130.2, 130.3 (2C), 131.7 (d, J = 4.1 Hz), 150.3 (d, J = 1.7 Hz), 158.6, 159.7 (d, J = 251.6 Hz); 19F-NMR (500 MHz, CDCl3) δ: −114.6; HRMS (FAB): m/z calcd for C22H26BrFN3O [M + H]+ 446.1243; found: 446.1237.

9-Bromo- N -( tert -butyl)-1′-(4-methoxybenzyl)-2 H -spiro(benzo[ e ]pyrimido[1,2- c ][1,3]thiazine-3,4′-piperidin)-6(4 H )-imine (52a). Using the general procedure as described for 48, 47 (2.0 g, 4.48 mmol) was allowed to react at rt overnight. Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:0 to 9:1) to give the title compound 52a as colorless solid (2.28 g, 94 %): mp 89–91 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1577 (C=N); 1H-NMR (500 MHz, CDCl3) δ: 1.37 (s, 9H, 3 × CH3), 1.49–1.52 (m, 4H, 2 × CH2), 2.40–2.46 (m, 4H, 2 × CH2), 3.41 (s, 2H, CH2), 3.47 (s, 2H, CH2), 3.75 (s, 2H, CH2), 3.80 (s, 3H, CH3), 6.85 (d, J = 8.6 Hz, 2H, Ar), 7.22 (d, J = 8.6 Hz, 2H, Ar), 7.28–7.31 (m, 2H, Ar), 8.03 (d, J = 8.6 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 29.7, 29.9 (3C), 32.6 (2C), 49.2 (2C), 51.6, 54.3, 55.2, 55.5, 62.7, 113.6 (2C), 124.5, 126.3, 126.8, 129.2, 130.0, 130.1, 130.4 (2C), 130.9, 137.5, 146.3, 158.7; HRMS (FAB): m/z calcd for C27H34BrN4OS [M + H]+ 541.1637; found: 541.1633.

Compound 53a. Using the general procedure as described for 25a, compound 52a (448.1 mg, 0.83 mmol) was allowed to react for 2 h with TFA (10.0 mL) and MS4Å (1.50 g). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (7:3) gave the title compound 53a as colorless solid (288.8 mg, 72 %): mp 160–162 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1626 (C=N), 1573 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.54 (t, J = 5.5 Hz, 4H, 2 × CH2), 2.39-2.51 (m, 4H, 2 × CH2), 3.46 (s, 2H, CH2), 3.48 (s, 2H, CH2), 3.79 (s, 3H, CH3), 3.86 (s, 2H, CH2), 6.84 (d, J = 8.8 Hz, 2H, Ar), 7.20–7.22 (m, 3H, Ar), 7.28 (s, 1H, NH), 7.32 (dd, J = 8.8, 2.0 Hz, 1H, Ar), 8.08 (d, J = 8.8 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 29.2, 32.6 (2C), 49.1 (2C), 50.8, 55.1, 55.2, 62.6, 113.6 (2C), 125.1, 125.1, 125.9, 129.5, 130.3 (2C), 130.3, 130.4, 130.7, 145.0, 152.6, 158.7; HRMS (FAB): m/z calcd for C23H26BrN4OS [M + H]+ 485.1011; found: 485.1010.

Synthesis of 9-Bromo-1′-(methoxycarbonyl)-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-piperidin)-6(4H)-imine (53b)

9-Bromo- N -( tert -butyl)-1′-(methoxycarbonyl)-2 H -spiro(benzo[ e ]pyrimido[1,2- c ][1,3]thiazine-3,4′-piperidin)-6(4 H )-imine (52b). To the solution of 9-bromo-N-(tert-butyl)-1′-(4-methoxybenzyl)-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-piperidin)-6(4H)-imine 52a (40.6 mg, 0.075 mmol) in CH2Cl2 (0.38 mL) was added methyl chloroformate (86.4 μL, 1.13 mmol) at 0 °C under an Ar atmosphere. After being stirred at same temperature for 30 min, the reaction mixture was concentrated. The residue was purified by flash chromatography over silica gel with n-hexane–EtOAc (1:1) to give the title compound 52b as a colorless solid (29.2 mg, 81 %): mp 157–158 °C (from n-hexane); IR (neat) cm−1: 1699 (C=O), 1577 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.37 (s, 9H, 3 × CH3), 1.46 (t, J = 5.6 Hz, 4H, 2 × CH2), 3.44 (br s, 4H, 2 × CH2), 3.56 (br s, 2H, CH2), 3.70 (s, 3H, CH3), 3.81 (s, 2H, CH2), 7.29–7.33 (m, 2H, Ar), 8.05 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 29.9 (3C), 30.1, 32.2 (2C), 39.9 (2C), 50.8, 52.5, 54.3, 55.2, 124.7, 126.1, 126.8, 129.3, 130.0, 130.9, 137.7, 146.3, 155.9; HRMS (FAB): m/z calcd for C21H28BrN4O2S [M + H]+ 479.1116; found: 479.1115.

Compound 53b. Using the general procedure as described for 25a, compound 52b (6.4 mg, 0.013 mmol) was allowed to react for 2 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (9:3) gave the title compound 53b as colorless solid (4.0 mg, 73 %): mp 139–141 °C (from MeCN–H2O); IR (neat) cm−1: 1692 (C=O), 1626 (C=N), 1573 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.49 (t, J = 5.7 Hz, 4H, 2 × CH2), 3.45-3.57 (m, 6H, 3 × CH2), 3.70 (s, 3H, CH3), 3.91 (s, 2H, CH2), 7.22 (d, J = 2.0 Hz, 1H, Ar), 7.31 (br s, 1H, NH), 7.34 (dd, J = 8.8, 2.0 Hz, 1H, Ar), 8.10 (d, J = 8.8 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 29.5, 32.2 (2C), 39.7 (2C), 50.0, 52.6, 54.6, 125.0, 125.3, 126.0, 129.6, 130.5, 130.6, 145.1, 152.6, 155.9; HRMS (FAB): m/z calcd for C17H20BrN4O2S [M + H]+ 423.0490; found: 423.0492.

Synthesis of 1′-Acetyl-9-bromo-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-piperidin)-6(4H)-imine (53c)

1′-Acetyl-9-bromo- N -( tert -butyl)-2 H -spiro(benzo[ e ]pyrimido[1,2- c ][1,3]thiazine-3,4′-piperidin)-6(4 H )-imine (52c). Using the general procedure as described for 52b, 9-bromo-N-(tert-butyl)-1′-(4-methoxybenzyl)-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-piperidin)-6(4H)-imine 52a (40.6 mg, 0.075 mmol) was allowed to react for 10 min with AcCl (53.3 μL, 0.75 mmol). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1) gave the title compound 52c as colorless solid (33.3 mg, 96 %): mp 181–182 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1632 (C=O), 1578 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.37 (s, 9H, 3 × CH3), 1.46–1.52 (m, 4H, 2 × CH2), 2.10 (s, 3H, CH3), 3.45–3.56 (m, 5H, 5 × CH), 3.72-3.78 (m, 2H, 2 × CH), 3.90 (d, J = 13.4 Hz, 1H, CH), 7.29–7.33 (m, 2H), 8.05 (d, J = 8.5 Hz, 1H); 13C-NMR (100 MHz, CDCl3) δ: 21.4, 29.9 (3C), 30.3, 32.2, 32.8, 37.5, 42.6, 50.8, 54.4, 55.1, 124.7, 126.0, 126.9, 129.3, 130.0, 130.8, 137.7, 146.3, 168.8; HRMS (FAB): m/z calcd for C21H28BrN4OS [M + H]+ 463.1167; found: 463.1164.

Compound 53c. Using the general procedure as described for 25a, compound 52c (6.5 mg, 0.014 mmol) was allowed to react for 2 h with TFA (1.0 mL) and MS4 Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:2) gave the title compound 53c as colorless solid (4.5 mg, 79 %): mp 147–148 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1625 (C=O), 1573 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.49–1.55 (m, 4H, 2 × CH2), 2.09 (s, 3H, CH3), 3.47–3.61 (m, 5H, 5 × CH), 3.70–3.77 (m, 1H, CH), 3.84 (d, J = 13.4 Hz, 1H, CH), 4.04 (d, J = 13.2 Hz, 1H, CH), 7.22 (d, J = 1.2 Hz, 1H, Ar), 7.33–7.36 (m, 2H, Ar, NH), 8.10 (d, J = 8.8 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 21.4, 29.7, 32.1, 32.7, 37.3, 42.4, 49.8, 54.7, 124.9, 125.3, 126.0, 129.6, 130.4, 130.6, 145.1, 152.6, 168.9; Anal. calcd for C17H19BrN4OS: C, 50.13; H, 4.70; N, 13.75. Found: C, 50.24; H, 4.78; N, 13.57.

Synthesis of 9-Bromo-1′-(methanesulfonyl)-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-piperidin)-6(4H)-imine (53d)

9-Bromo- N -( tert -butyl)-1′-(methanesulfonyl)-2 H -spiro(benzo[ e ]pyrimido[1,2- c ][1,3]thiazine-3,4′-piperidin)-6(4 H )-imine (52d). To the solution of 9-bromo-N-(tert-butyl)-1′-(4-methoxybenzyl)-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-piperidin)-6(4H)-imine 52a (54.2 mg, 0.10 mmol) in CH2Cl2 (0.5 mL) were added Et3N (28.9 μL, 0.20 mmol) and 1-chloroethyl chloroformate (21.8 μL, 0.20 mmol) at 0 °C under an Ar atmosphere. After being stirred at same temperature for 30 min, the reaction mixture was concentrated. The residue was dissolved in MeOH (2.0 mL). After being stirred under reflux for 10 min, the reaction mixture was concentrated. The residue was dissolved in CHCl3, and was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was dissolved in CH2Cl2 (1.0 mL) and Et3N (28.9 μL, 0.20 mmol), and MsCl (15.5 μL, 0.20 mmol) was added at rt under an Ar atmosphere. After being stirred at rt for 10 min, the reaction mixture was washed with sat. NaHCO3, brine, and dried over MgSO4. After concentration, the residue was purified by flash chromatography over aluminum oxide with n-hexane–EtOAc (6:4) to give the title compound 52d as a colorless solid (40.9 mg, 82 %): mp 177 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1577 (C=N), 1331 (NSO2), 1155 (NSO2); 1H-NMR (400 MHz, CDCl3) δ: 1.38 (s, 9H, 3 × CH3), 1.62 (t, J = 5.5 Hz, 4H, 2 × CH2), 2.80 (s, 3H, CH3), 3.21–3.27 (m, 2H, CH2), 3.31–3.37 (m, 2H, CH2), 3.46 (s, 2H, CH2), 3.84 (s, 2H, CH2), 7.29–7.33 (m, 2H, Ar), 8.05 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 29.8, 29.9 (3C), 32.0 (2C), 34.7, 42.0 (2C), 50.1, 54.4, 55.1, 124.8, 125.9, 126.9, 129.4, 130.0, 130.8, 137.9, 146.3; HRMS (FAB): m/z calcd for C20H28BrN4O2S2 [M + H]+ 499.0837; found: 499.0840.

Compound 53d. Using the general procedure as described for 25a, compound 52d (9.2 mg, 0.018 mmol) was allowed to react for 2 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with n-hexane–EtOAc (1:1) gave the title compound 53d as colorless solid (5.3 mg, 65 %): mp 171–172 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1621 (C=N), 1564 (C=N), 1320 (NSO2), 1152 (NSO2); 1H-NMR (400 MHz, CDCl3-CD3OD) δ: 1.64–1.67 (m, 4H, 2 × CH2), 2.82 (s, 3H, CH3), 3.19–3.25 (m, 2H, CH2), 3.35–3.41 (m, 2H, CH2), 3.52 (s, 2H, CH2), 3.92 (s, 2H, CH2), 7.24 (d, J = 2.0 Hz, 1H, Ar), 7.37 (dd, J = 8.5, 2.0 Hz, 1H, Ar), 8.07 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3-CD3OD) δ: 29.0, 31.9 (2C), 34.7, 41.7 (2C), 49.2, 54.6, 124.7, 125.4, 126.0, 129.7, 130.3, 130.4, 145.3, 153.1; HRMS (FAB): m/z calcd for C16H20BrN4O2S2 [M + H]+ 443.0211; found: 443.0210.

Synthesis of 1′-(Aminocarbonyl)-9-bromo-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-piperidin)-6(4H)-imine (53e)

1′-(Aminocarbonyl)-9-bromo- N -( tert -butyl)-2 H -spiro(benzo[ e ]pyrimido[1,2- c ][1,3]thiazine-3,4′-piperidin)-6(4H )-imine (52e). Using the general procedure as described for 52d, 9-bromo-N-(tert-butyl)-1′-(4-methoxybenzyl)-2H-spiro(benzo[e]pyrimido[1,2-c][1,3]thiazine-3,4′-piperidin)-6(4H)-imine 52a (54.2 mg, 0.10 mmol) was allowed to react with 1-chloroethyl chloroformate (21.8 μL, 0.20 mmol) followed with N-trimethylsilylisocyanate (26.5 μL, 0.20 mmol). Purification by flash chromatography over aluminum oxide with EtOAc–MeOH (1:0 to 9:1) gave the title compound 52e as colorless solid (11.8 mg, 29 %): mp 203–205 °C (from CHCl3–n-hexane); IR (neat) cm−1: 1649 (C=O), 1577 (C=N); 1H-NMR (400 MHz, CDCl3) δ: 1.37 (s, 9H, 3 × CH3), 1.51 (t, J = 5.6 Hz, 4H, 2 × CH2), 3.37–3.51 (m, 6H, 3 × CH2), 3.82 (s, 2H, CH2), 4.46 (s, 2H, NH2), 7.30–7.33 (m, 2H, Ar), 8.05 (d, J = 8.5 Hz, 1H, Ar); 13C-NMR (100 MHz, CDCl3) δ: 29.9 (3C), 30.0, 32.1 (2C), 40.3 (2C), 50.9, 54.4, 55.1, 124.7, 126.0, 126.8, 129.3, 130.0, 130.9, 137.6, 146.3, 158.0; HRMS (FAB): m/z calcd for C20H27BrN5OS [M + H]+ 464.1120; found: 464.1122.

Compound 53e. Using the general procedure as described for 25a, compound 52e (5.1 mg, 0.011 mmol) was allowed to react for 2 h with TFA (1.0 mL) and MS4Å (150 mg). Purification by flash chromatography over aluminum oxide with EtOAc–MeOH (1:0 to 9:1) gave the title compound 53e as colorless solid (4.2 mg, 94 %): mp 222 °C (from MeOH–CHCl3–n-hexane); IR (neat) cm−1: 1651 (C=O), 1624 (C=N), 1585 (C=N); 1H-NMR (400 MHz, DMSO-d6) δ: 1.31 (t, J = 5.6 Hz, 4H, 2 × CH2), 3.20–3.38 (m, 4H, 2 × CH2), 3.45 (s, 2H, CH2), 3.84 (s, 2H, CH2), 5.88 (s, 2H, NH2), 7.42 (dd, J = 8.5, 1.5 Hz, 1H), 7.59 (d, J = 1.5 Hz, 1H), 8.08 (d, J = 8.5 Hz, 1H, Ar), 8.91 (s, 1H, NH). 13C-NMR (125 MHz, DMSO-d6) δ: 29.0, 31.6 (2C), 39.5 ± 1.0 (2C), 48.9, 54.0, 124.3, 124.7, 126.0, 129.0, 130.2, 131.2, 144.0, 149.2, 158.0; HRMS (FAB): m/z calcd for C16H19BrN5OS [M + H]+ 408.0494; found: 408.0496.

Determination of Anti-HIV Activity

The sensitivity of HIV-1IIIB strain was determined by the MAGI assay. The target cells (HeLa-CD4/CCR5-LTR/β-gal; 104 cells/well) were plated in 96-well flat microtiter culture plates. On the following day, the cells were inoculated with the HIV-1 (60 MAGI U/well, giving 60 blue cells after 48 h of incubation) and cultured in the presence of various concentrations of the test compounds in fresh medium. Forty-eight hours after viral exposure, all the blue cells stained with X-Gal (5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside) were counted in each well. The activity of test compounds was determined as the concentration that blocked HIV-1 infection by 50 % (50 % effective concentration [EC50]). EC50 was determined by using the following formula:

EC50 = 10^[log(A/B) × (50 − C)/(D − C) + log(B)],

wherein

  • A: of the two points on the graph which bracket 50 % inhibition, the higher concentration of the test compound,

  • B: of the two points on the graph which bracket 50 % inhibition, the lower concentration of the test compound,

  • C: inhibitory activity (%) at the concentration B,

  • D: inhibitory activity (%) at the concentration A.

Footnotes

1

Because a 9-brominated derivative 25k exhibited more potent anti-HIV activity than compound 1 in the SAR study, the author employed compound 25k as a lead.

2

The cytotoxicity of compounds 1, 32c and 36d was not observed at 10 μM in the MAGI assay. Further toxicity studies such as hemolytic activity or renal/liver accumulation may be needed to take a drug for long periods of time.

References

  • 1.Chockalingam K, Simeon RL, Rice CM, Chen Z. Proc. Natl. Acad. Sci. U.S.A. 2010;107:3764–3769. doi: 10.1073/pnas.0915117107. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Chamoun AM, Chockalingam K, Bobardt M, Simeon R, Chang J, Gallay P, Chen Z. Antimicrob. Agents Chemother. 2012;56:672–681. doi: 10.1128/AAC.05722-11. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Ishihara M, Togo H. Tetrahedron. 2007;63:1474–1480. doi: 10.1016/j.tet.2006.11.077. [DOI] [Google Scholar]
  • 4.Wolfe JP, Wagaw S, Marcoux J-F, Buchwald SL. Acc. Chem. Res. 1998;31:805–818. doi: 10.1021/ar9600650. [DOI] [Google Scholar]
  • 5.Hartwig JP. Angew. Chem. Int. Ed. 1998;37:2046–2065. doi: 10.1002/(SICI)1521-3773(19980817)37:15<2046::AID-ANIE2046>3.0.CO;2-L. [DOI] [PubMed] [Google Scholar]
  • 6.Kunz K, Scholz U, Ganzer D. Synlett. 2003;15:2428–2439. doi: 10.1055/s-2003-42473. [DOI] [Google Scholar]
  • 7.Arvela RK, Pasquini S, Larhed MJ. Org. Chem. 2007;72:6390–6396. doi: 10.1021/jo0705768. [DOI] [PubMed] [Google Scholar]
  • 8.Miyaura N, Suzuki A. Chem. Rev. 1995;95:2457–2483. doi: 10.1021/cr00039a007. [DOI] [Google Scholar]
  • 9.Mitschb A, Altenkämpera M, Sattlerc I, Schlitzer M. Arch. Pharm. Chem. Life Sci. 2005;338:9–17. doi: 10.1002/ardp.200400886. [DOI] [PubMed] [Google Scholar]
  • 10.Watanabe K, Negi S, Sugiura Y, Kiriyama A, Honbo A, Iga K, Kodama EN, Naitoh T, Matsuoka M, Kano K. Chem. Asian J. 2010;5:825–834. doi: 10.1002/asia.200900465. [DOI] [PubMed] [Google Scholar]
  • 11.Drake RR, Neamati N, Hong H, Pilon AA, Sunthankar P, Hume SD, Milne GWA, Pommier Y. Proc. Natl. Acad. Sci. U.S.A. 1998;95:4170–4175. doi: 10.1073/pnas.95.8.4170. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12.Lin W, Li K, Doughty MB. Bioorg. Med. Chem. 2002;10:4131–4141. doi: 10.1016/S0968-0896(02)00259-6. [DOI] [PubMed] [Google Scholar]
  • 13.Al-Mawsawi LQ, Fikkert V, Dayam R, Witvrouw M, Burke TR, Jr, Borchers CH, Neamati N. Proc. Natl. Acad. Sci. U.S.A. 2006;103:10080–10085. doi: 10.1073/pnas.0511254103. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.Baba M, Scgols D, Pauwels R, Nakashima H, De Clercq EJ. Acquir. Immune. Defic. Syndr. 1990;3:493–499. [PubMed] [Google Scholar]
  • 15.Kilby JM, Eron JJN. Engl. J. Med. 2003;348:2228–2238. doi: 10.1056/NEJMra022812. [DOI] [PubMed] [Google Scholar]
  • 16.Lalezari JP, Henry K, O’Hearn M, Montaner JS, Piliero PJ, Trottier B, Walmsley S, Cohen C, Kuritzkes DR, Eron JJ, Jr, Chung J, DeMasi R, Donatacci L, Drobnes C, Delehanty J, Salgo MN. Engl. J. Med. 2003;348:2175–2185. doi: 10.1056/NEJMoa035026. [DOI] [PubMed] [Google Scholar]
  • 17.Matthews T, Salgo M, Greenberg M, Chung J, DeMasi R, Bolognesi D. Nat. Rev. Drug Discov. 2004;3:215–225. doi: 10.1038/nrd1331. [DOI] [PubMed] [Google Scholar]
  • 18.Fischl MA, Richman DD, Grieco MHN. Engl. J. Med. 1987;317:185–191. doi: 10.1056/NEJM198707233170401. [DOI] [PubMed] [Google Scholar]
  • 19.Merluzzi VJ, Hargrave KD, Labadia M, Grozinger K, Skoog M, Wu JC, Shih C-K, Eckner K, Hattox S, Adams J, Rosehthal AS, Faanes R, Eckner RJ, Koup RA, Sullivan JL. Science. 1990;250:1411–1413. doi: 10.1126/science.1701568. [DOI] [PubMed] [Google Scholar]
  • 20.Steigbigel RT, Cooper DA, Kumar PN, Eron JE, Schechter M, Markowitz M, Loutfy MR, Lennox JL, Gatell JM, Rockstroh JK, Katlama C, Yeni P, Lazzarin A, Clotet B, Zhao J, Chen J, Ryan DM, Rhodes RR, Killar JA, Gilde LR, Strohmaier KM, Meibohm AR, Miller MD, Hazuda DJ, Nessly ML, DiNubile MJ, Isaacs RD, Nguyen B-Y, Teppler HN. Engl. J Med. 2008;359:339–354. doi: 10.1056/NEJMoa0708975. [DOI] [PubMed] [Google Scholar]
  • 21.Witvrouw M, Pannecouque C, Switzer WM, Folks TM, De Clercq E, Heneine W. Antivir. Ther. 2004;9:57–65. [PubMed] [Google Scholar]

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