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. 2018 May 10;3(5):5116–5124. doi: 10.1021/acsomega.8b00491

Synthesis of P-Stereogenic Benzoazaphosphole 1-Oxides via Alkynylation of P-Stereogenic ortho-Aurated and ortho-Iodo Phosphinic Amides

Raquel Soengas 1, Eva Belmonte Sánchez 1, María José Iglesias 1, Fernando López Ortiz 1,*
PMCID: PMC6641963  PMID: 31458727

Abstract

graphic file with name ao-2018-00491g_0009.jpg

An efficient methodology for the synthesis of P-stereogenic dihydrobenzoazaphosphole 1-oxides via intramolecular 5-exo-dig alkyne hydroamination promoted by tetrabutylammonium fluoride is herein described. The required chiral o-alkynylphosphinic amide starting materials were prepared in high yields under very mild reaction conditions through alkynylation of P-stereogenic (O^C)-cyclometalated (phosphinic amide)dichlorogold(III) complexes and Sonogashira cross-coupling of ortho-iodo P-stereogenic phosphinic amide.

Introduction

The isoindolin-1-one motif is a core structure of numerous natural and synthetic products1 that show a wide range of biological activities, such as antimicrobial, anti-HIV, antipsychotic, antidiabetic, and anticancer agents, among others.2 Considering that there is a remarkable similarity in reactivity and bioactivity between carbon species and their phosphorus counterparts, the phosphorus analogues of isoindolin-1-ones become desirable targets.3 Moreover, because the planar carbonyl group is replaced by a tetrahedral P=O linkage, this type of compounds brings the additional advantage of the possibility of synthesizing P-stereogenic enantiopure heterocycles.

Methods available for the preparation of phosphaisoindolin-1-ones (dihydrobenzoazaphosphole 1-oxides) are limited to the ring closure of (o-chloromethyl)phenylphosphinic amides 1 (Scheme 1a) promoted by DBU to give 2;4 nitrene insertion into a benzylic ortho C–H bond through photolysis of phosphinic azides having P-mesityl or P-(2,4,6-triisopropylphenyl) groups 3 to afford heterocycles 4 (Scheme 1b)5 and trapping (R)-N-(1-phenylethyl)silanamine 5 doubly lithiated at the N and Cortho positions with phenylphosphonic dichloride. The reaction provides (SP,RC)-6 in a yield of 43% and high diastereoselectivity (dr > 95:5, Scheme 1c).6,7

Scheme 1. Synthesis of Phosphaisoindolin-1-ones: (a) Ring Closure of (o-Chloromethyl)phenylphosphinic Amides; (b) Photolysis of Phosphinic Azides; and (c) Reaction of Doubly Lithiated Silanamines with Phenylphosphonic Dichloride.

Scheme 1

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These methods suffer from several drawbacks including cumbersome multistep processes, lack of generality, and low yields. Similarly to the synthesis of isoindolin-1-ones through C–N coupling reactions,8 transition-metal-catalyzed N-cyclizations of ortho-alkynylphosphinic amides would be an attractive alternative for building up the benzoazaphosphole 1-oxide system.

However, the one-pot metal-catalyzed ortho alkynylation–aminocyclization of phosphinic amides 7 using Co(II)9 and Rh(III)10 catalysts has been reported to proceed exclusively through 6-endo-dig cyclizations, leading to phosphaisoquinolin-1-ones 8. Recently, an enantioselective route to 8 using a chiral Rh(III) catalyst has been described (Scheme 2a).11o-Ethynylphenylphosphonamide monoethyl esters 9 also undergo Pd(II)-catalyzed cyclization reactions with the formation of phosphaisoquinolin-1-ones 10 (Scheme 2b).12

Scheme 2. Synthesis of Phosphaisoquinolin-1-ones: (a) Rh(III)-Catalyzed Cyclization and (b) Pd(II)-Catalyzed Cyclization.

Scheme 2

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We have reported that (O^C)- and (S^C)-cycloaurated complexes based on an ortho-substituted phosphinic amide and phosphinothioic amide framework are transformed into the corresponding ortho-alkynyl derivatives when they are used as precatalysts in the amine–aldehyde–alkyne (A3) three-component coupling synthesis of propargylamines under solvent-free conditions.13 This feature raises the question of whether Au(III) could be used for the transfer of acetylenes. Previous studies by Corma and co-workers showed that Sonogashira products were not formed in the reaction between terminal alkynes and aryl halides catalyzed by gold(III) complexes.14 In addition, alkynes are one of the most useful functional groups in synthetic chemistry, chemical biology, and materials science.15

We describe herein the synthesis and alkynylation of a P-stereogenic (O^C)-cyclometalated gold(III) complex I, an alternative route of accessing the alkynylated products III through Pd-catalyzed Sonogashira cross-coupling of terminal alkynes with a P-stereogenic ortho-iodophosphinic amide II, and the aminocyclization of the o-alkynyl derivatives to generate P-stereogenic enantiopure analogues of isoindolin-1-ones IV (Scheme 3).

Scheme 3. Retrosynthesis of Phosphaisoindolin-1-ones.

Scheme 3

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Results and Discussion

For the synthesis of a P-stereogenic (O^C)-cyclometalated gold(III) complex of type I, we followed the methodology developed in our group, which involves directed ortho lithiation of a diphenylphosphinic amide followed by electrophilic trapping with tin(IV) halides, Sn–Me bond cleavage with HCl–Et2O, and finally Sn(IV)–Au(III) transmetalation.16 Thus, starting from previously described ortho-stannylated phosphinamide 11,16b Sn–Me bond cleavage with HCl–Et2O gave chlorodimethylstannane 12 in a 87% yield (Scheme 4). Then, heating a CH3CN solution of 12 in the presence of 1 equiv of the gold salt K[AuCl4] afforded desired Au(III) complex (SP,SC)-13 in good yield (82%) after precipitation in Et2O.

Scheme 4. Synthesis of P-Stereogenic Au(III) Complex (SP,SC)-1c.

Scheme 4

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The tin(IV) compound 12 and the gold(III) complex 13 have been fully characterized through mass spectrometry and nuclear magnetic resonance spectroscopic methods. The solid-state structure of stannane 12 was unequivocally determined by single-crystal X-ray diffraction (Figure S75, Supporting Information) and revealed intramolecular Sn–O coordination, which is evidenced by the distorted trigonal pyramid (tbp) geometry of the tin atom that showed a distance O···Sn of 1.41 Å shorter than the sum of the respective van der Waals radii (3.69 Å) and a Sn–Cl bond anti to the oxygen atom 0.41 Å larger than the Sn–C bonds in the equatorial plane of the tbp (average distance of 2.12 Å) (Table S1, Supporting Information). To the best of our knowledge, there is no precedent of P-stereogenic cycloaurated gold(III) complexes in the literature.17

In order to access P-chiral o-alkynylphosphinic amides, we envisioned the alkynylation of P-stereogenic (O^C)-cyclometalated dichloro gold(III) complex 13. To search the optimal conditions, the alkynylation of 13 with trimethylsilylacetylene 14a was used as a reaction model. The best results were achieved when a solution of complex 13 (1.0 equiv) in CH3CN was treated with the alkyne 14a (2.0 equiv) and excess piperidine (3.0 equiv) at 60 °C for 6 h. Under these conditions, alkynylaryl 15a was isolated in good yield after aqueous work-up and purification by chromatography (Table 1, entry 1).

Table 1. Synthesis of P-Stereogenic ortho-Alkynylphosphinic Amides (SP,SC)-15a–g.

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entry 14 R 15 yield %a
1 a TMS a 98
2 b Ph b 85
3 c 4-FC6H4 c 98
5 d 3-MeC6H4 d 89
4 e 2-OMeC6H4 e 95
6 f 3,5-CF3C6H3 f 75
7 g 2-CH2OHC6H4 g 82
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a

Isolated yield after column chromatography.

This protocol was then extended to other alkynes bearing either electron-withdrawing or electron-donating substituents (Table 1, entries 2–7). In all cases, the corresponding o-alkynylphosphinic amides 15b–g were obtained in high yields. Unfortunately, all attempts of achieving the process in a catalytic manner using ortho-halophosphinic amides as starting material failed. No oxidative addition of Au(I) was observed.14,18 Alternatively, the synthesis of P-stereogenic o-alkynylphosphinic amides could also be accomplished via Pd/Cu-catalyzed Sonogashira reaction of the corresponding o-iodo derivative. In order to increase structural diversity, we used o-iodo-N-((R)-1-phenylethyl)phosphinic amide 16 as the starting material. Compound 16 is readily obtained via a highly diastereoselective N,Cortho dilithiation of methyl (R)-(diphenyl((1-phenylethyl)amino)-λ5-phosphanylidene)carbamate (dr 95:5) followed by electrophilic trapping with 1,2-diiodoethane and subsequent aza-Wittig reaction with acetaldehyde.19

For the Sonogashira-based synthesis of o-alkynylphosphinic amides 15, we used ethynyltrimethylsilane 14a as the coupling partner with ortho-iodophosphinic amide 16 and 2 mol % of PdCl2(PPh3)2 and 1 mol % CuI as catalysts. Heating the reaction mixture at 50 °C for 12 h in the presence of Et3N afforded optically pure (RP,RC)-15h in good yield (Table 2). We then set out to explore the scope of this transformation with a range of alkynes containing different substitution patterns.

Table 2. Synthesis of P-Stereogenic o-Alkynylphosphinic Amides (RP,RC)-15h–l.

graphic file with name ao-2018-00491g_0007.jpg

entry 14 R 15 yield %a
1 a TMS h 88
2 b Ph i 96
3 c 4-FC6H4 j 94
4 e 2-OMeC6H4 k 95
6 g 2-CH2OHC6H4 l 45b
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a

Isolated yield after column chromatography.

b

Conversion determined by 1H-NMR.

The reaction was compatible with the presence of electron-withdrawing and electron-donating groups, regardless of their location in the phenyl group. The ortho-alkyne derivatives 15i and 15j bearing either a p-fluoro or a o-methoxy group, respectively, were obtained almost quantitatively after 12 h of reaction. However, the coupling reaction with (2-ethynyl-phenyl)methanol afforded product 15l in moderate conversion of ca. 45%. This result is in sharp contrast with the alkynylation of gold complex 13 with (2-ethynyl-phenyl)methanol, which gave the product in 100% conversion and excellent isolated yield (82%). As mentioned above, P-stereogenic o-alkynylphosphinic amides 15 are phosphorus-containing analogues of o-(1-alkynyl)benzamides, a very useful synthon for accessing isoindol-1-ones via 5-exo-dig N-cyclization.8 We decided to explore the annulation of the enyne-phosphinic amide moiety of compounds 15 using the metal-free, inexpensive, and environmentally friendly phase transfer catalysis (PTC) methodology.20 The reaction was carried out by treating a tetrahydrofuran (THF) solution of the corresponding o-alkynylphosphinic amides 15 (0.03 M) with 1.5 equiv of tetrabutylammonium fluoride (TBAF) at room temperature (rt) for 1 h. We started our study with substrate 15a, for which deprotection of the alkyne (containing a trimethylsilyl (TMS) group) and cyclization took place in the same process, furnishing exclusively the product of 5-exo-dig ring closure 17a in good yield (Table 3, entry 1). The selectivity of 5-exo/6-endo-dig observed is in agreement with recent computational studies showing that, in related aminoalkynylation reaction, the formation of 5-exo-dig products is highly favored kinetically.21 Contrary to the anionic cyclization, analogue metal-catalyzed cycloisomerization reactions generally proceed through 6-endo-dig pathways.11,12,22 In an attempt to switch the selectivity toward 6-endo benzannulated derivative 18, alkyne 15b was treated with bis(benzonitrile)palladium(II) chloride and trimethylamine in refluxing THF. However, the 5-exo-dig product 17b was exclusively formed under these conditions.23

Table 3. Synthesis of P-Stereogenic (SP,SC) and (RP,RC)-1,2-Benzoazaphosphole 2-Oxides 17.

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entry 15 R1 R2 17 E/Za yield %b
1 a TMS (S)-CHMetBu a   74
2 b Ph (S)-CHMetBu b 74:26 73
3 c 4-FC6H4 (S)-CHMetBu c 92:8 78
4 d 3-MeC6H4 (S)-CHMetBu d 70:30 69
5 e 2-OMeC6H4 (S)-CHMetBu e 81:19 88
6 h TMS (R)-CHMePh f   75
7 i Ph (R)-CHMePh g 82:18 95
8 j 4-FC6H4 (R)-CHMePh h 91:9 83
9 k 2-OMeC6H4 (R)-CHMePh i 70:30 88
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a

Determined by 1H NMR (300 MHz).

b

Isolated yield after column chromatography.

Heterocycle 17a has been fully characterized through mass spectrometric and NMR spectroscopic techniques. Additionally, the solid-state structure was determined through single-crystal X-ray diffraction (Figure S76, Supporting Information). As far as we know, the formation of 17a represents the first regioselective synthesis of P-stereogenic 1,2-benzoazaphosphole 2-oxides based on an intramolecular cyclization without the employment of metals. Given the satisfactory results, the methodology was extended to P-stereogenic alkynyl aryls 15b–k, and the results are summarized in Table 3. In all cases, the reaction took place with total regioselectivity with formation of the five-membered ring. Mixtures of the Z and E isomers were obtained in favor of the E diastereoisomer. Compounds 17a–e showed atropisomerism because of the restricted reorientation of the bulky N-alkyl substituent. These results show that the diastereoselectivity depends on the substituents present on the phenyl linked to the alkyne moiety. The diastereomeric ratio varied as a function of the substitution pattern, being in the range of 70:30 (17d,i) to 91:9 (17h). The configuration of the exocyclic carbon–carbon double bond was unequivocally established via 1D gNOESY NMR experiments (Figures S49, S53, S67, and S71, Supporting Information).

Finally, we submitted phosphinic amide 15g containing an NH and an OH group to the same reaction conditions (Scheme 4). Compound 18 was obtained in 84% yield, indicating that cycloaddition through the oxygen atom is favored over cycloaddition through the nitrogen. This result is in agreement with previous work reported in the literature about hydroxy- versus aminocyclizations (Scheme 5).24

Scheme 5. Synthesis of ortho-(1H-Isochromene)phosphinic Amide 18.

Scheme 5

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Conclusions

We have described the alkynylation of an unprecedented (SP,SC)-(O^C)-cycloaurated gold(III) complex. The formation of the P-stereogenic cross-coupling ortho-alkynylphosphinic amides proceeded straightforward in high yield. Alternatively, the Sonogashira cross-coupling reaction between a (RP,RC)-phosphinic amide and a series of terminal alkynes afforded the enantiopure ortho-alkyne derivatives in moderate to high yield. These ortho-alkynylphosphinic amides provided an efficient route to P-stereogenic dihydrobenzoazaphosphole 1-oxides via intramolecular alkyne hydroamination under metal-free conditions using TBAF as the cyclization agent. The new N,P-containing heterocycles are analogues of the important isoindolin-1-one core, in which the carbon atom of the C=O group has been replaced by a P-chirogenic moiety.

Experimental Section

General Information

All reactions were carried out under inert atmosphere, in previously dried Schlenk flasks. CH3CN was distilled in the presence of P2O5 and degassed before use. Commercial reagents were purified by distillation before use, except for organolithium base and TBAF, which were used as received. Compounds 11(13b) and 16(16b) were synthesized, as previously reported. All new compounds were characterized based on their NMR spectroscopy data and high-resolution mass spectrometry (HRMS) spectra. NMR spectra were obtained on a Bruker AVANCE III HD 300 (1H 300.13 MHz; 13C 75.47 MHz; 31P 121.49 MHz) and a Bruker AVANCE III HD 500 (1H 500.13 MHz; 13C 125.76 MHz; 31P 202.46 MHz). Chemical shifts are given in ppm using tetramethylsilane (TMS) for 1H and 13C as internal standards and 85% H3PO4 for 31P as an external standard. 1H, 1H{31P} and 31P NMR spectra were acquired from all reaction crudes in CDCl3 or CD3CN as the solvent. The following abbreviations are used to indicate the multiplicity of signal: s—singlet, d—doublet, t—triplet, q—quartet, and sep—septet. HRMS were recorded on an Agilent Technologies LC/MSD-TOF and HP 1100 MSD spectrometer using electrospray ionization. Melting points were recorded on Büchi B-540 capillary melting point apparatus and are uncorrected.

Crystallography

Single-crystal X-ray diffraction data for compound 17a were collected on a Bruker AXS Smart APEX diffractometer using graphite monochromatic Mo Kα radiation (λ = 0.71069 Å) at 100(2) and 293(2) K. Data collection and cell refinement were performed with the Bruker SMART program.25 For compound 12, the crystallographic data were collected on a Bruker D8 VENTURE diffractometer at 100 K, using Cu Kα radiation (λ = 1.54178 Å). Data collection and cell refinement were performed with Bruker Instrument Service v4.2.2. Empirical multiscan absorption correction using equivalent reflections was performed with the SADABS program.26 The structure solutions and full-matrix least-squares refinements based on F2 were performed with the SHELXL program package.27 All atoms except for hydrogen were refined anisotropically. Hydrogen atoms were treated by a mixture of independent and constrained refinement. CCDC 1579088 for 12 and 1573376 for 17a contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/products/csd/request/ or from Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44-1223-336-033; E-mail: deposit@ccdc.cam.ac.uk).

(S)-P-Phenyl-N-((S)-3,3-dimethylbutan-2-yl)-P-(2-(chlorodimethylstannyl)phenyl) Phosphinic Amide (12)

To a solution of the stannane 11 (400 mg, 0.85 mmol) in toluene (21 mL) was added a solution of HCl (0.9 mL of a 1.0 M solution in diethyl ether, 0.93 mmol). The reaction mixture was stirred at rt for 1 h and then evaporated under reduced pressure. The residue was purified by precipitation with diethyl ether, affording 12 (378 mg, 0.75 mmol) in 87% yield. A diethyl ether solution of this solid was stored at rt, affording air-stable crystals suitable for X-ray diffraction. White solid. mp 148–150 °C; 1H NMR (300.13 MHz, CDCl3): δ 0.88 (s, 3H), 0.92 (s, 9H), 0.93 (s, 3H), 1.22 (d, 3JHH 6.6 Hz, 3H), 2.74 (ddq, 3JHH 11.5 Hz, 3JPH 8.8 Hz, 3JHH 6.6 Hz, 1H), 2.93 (dd, 3JHH 11.5, 3JPH 4.6 Hz, 1H), 7.48–7.69 (m, 5H), 7.83–7.94 (m, 3H), 8.63 (dd, 3JHH 7.3, 4JPH 2.2 Hz, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 3.5 (d, 4JPC 3.0 Hz), 4.2 (d, 4JPC 2.9 Hz), 19.3 (d, 3JPC 6.0 Hz), 26.4, 34.9 (d, 2JPC 7.8 Hz), 50.7 (d, 3JPC 3.3 Hz), 129.1 (d, 3JPC 12.7 Hz), 129.2 (d, 2JPC 12.6 Hz), 130.3 (d, 1JPC 132.2 Hz), 131.6 (d, 2JPC 13.0 Hz), 131.6 (d, 3JPC 9.3 Hz), 132.4 (d, 4JPC 3.5 Hz), 133.1 (d, 4JPC 2.7 Hz), 133.0 (d, 1JPC 134.5 Hz), 137.9 (d, 2JPC 16.1 Hz), 152.4 (d, 2JPC 17.7 Hz) ppm; 31P NMR (121.50 MHz, CDCl3): δ 32.4 ppm; HRMS-ESI (m/z): [M – Cl]+ calcd for C20H29NOPSn, 450.1003; found, 450.1016.

(S)-[2-((2S)-1,2,2-Trimethylpropylamino) (Phenyl)phosphoroxoyl Phenyl] Gold(III) Dichloride (13)

K[AuCl4] (159 mg, 0.41 mmol) was added to a solution of 12 (238 mg, 0.41 mmol) in CH3CN (5 mL). The reaction mixture was heated at 90 °C for 2 h, after which the solution was cooled, filtered, and then evaporated under reduced pressure. The resulting yellow solid was washed with diethyl ether three times, then filtered, and dried under vacuum to afford gold complex 13 (207 mg, 0.36 mmol) in 89% yield. Yellow solid. mp 138–140 °C; 1H NMR (300.13 MHz, CDCl3): δ 0.92 (s, 9H), 1.28 (d, 3JHH 6.6 Hz, 3H), 3.03 (ddq, 3JHH 11.0, 3JPH 8.8, 3JHH 6.6 Hz, 1H), 3.60 (dd, 3JHH 11.0, 3JPH 5.5 Hz, 1H), 7.06 (td, 3JHH 7.5, 3JPH 2.5 Hz, 1H), 7.20 (t, 3JHH 7.5 Hz, 1H), 7.35 (dd, 3JHH 8.0, 3JHH 3.5 Hz, 1H), 7.46–7.57 (m, 4H), 8.00 (ddd, 3JPH 11.9, 3JHH 8.0, 3JHH 1.6 Hz, 2H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 19.5 (d, 3JPC 6.0 Hz), 26.4, 34.8 (d, 2JPC 6.8 Hz), 53.9 (d, 3JPC 2.7 Hz), 129.2 (d, 2JPC 11.8 Hz), 129.2 (d, 3JPC 12.6 Hz), 130.0 (d, 1JPC 130.7 Hz), 131.9 (d, 3JPC 12.8 Hz), 133.3 (d, 2JPC 9.2 Hz), 133.4 (d, 4JPC 3.5 Hz), 133.6 (d, 4JPC 3.5 Hz), 134.21 (d, 3JPC 17.5 Hz), 141.6 (d, 1JPC 128.3 Hz), 144.3 (d, 2JPC 12.9 Hz) ppm; 31P NMR (121.50 MHz, CDCl3): δ 25.5 ppm; HRMS-ESI (m/z): [M – Cl]+ calcd for C18H23AuClNOP, 532.0871; found, 532.0866.

General Procedure for the Alkynylation of Au–Dichloride Complex 13

To a solution of Au(III) dichloride complex 13 (0.2 mmol) and the corresponding acetylene 14 (0.6 mmol) in CH3CN (12 mL), piperidine was added (1.0 mmol). The reaction mixture was stirred at 60 °C for 6 h and then evaporated under reduced pressure. Addition of water (20 mL) followed by extraction with dichloromethane (2 × 20 mL) and solvent evaporation under vacuum afforded a crude product (SP,SC)-15, which was purified by column chromatography in silica gel eluting with mixtures AcOEt/hexane.

(S)–P-Phenyl-N-((S)-3,3-dimethylbut-2-yl)-P-(2-(trimethylsilylethynyl)phenyl)-phosphinic Amide (15a)

Isolated yield after chromatography (AcOEt/hexane 1:1) 98%. Yellow oil; 1H NMR (300.13 MHz, CDCl3): δ 0.02 (s, 9H), 1.63 (d, 3JHH 6.9 Hz, 3H), 3.79 (t, 3JHH = 2JPH 9.5 Hz, 1H), 4.70 (m, 1H), 7.11–7.52 (m, 6H), 7.72–7.76 (m, 2H), 8.16 (m, 1H) ppm; 3C NMR (75.47 MHz, CDCl3): δ 101.8, 104.3 (d, 3JPC 6.0 Hz), 124.4 (d, 3JPC 13.4 Hz), 128.1 (d, 2JPC 8.3 Hz), 128.3 (d, 3JPC 11.1 Hz), 131.0 (d, 4JPC 2.8 Hz), 131.1 (d, 2JPC 11.1 Hz), 131.7 (d, 4JPC 2.8 Hz), 133.6 (d, 3JPC 9.7 Hz), 134.1 (d, 1JPC 129.5 Hz), 134.2 (d, 2JPC 6.9 Hz), 134.6 (d, 1JPC 117.9 Hz) ppm; 31P NMR (121.50 MHz, CDCl3): δ 24.5 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C23H33NOPSi, 398.2069; found, 398.2064.

(S)-P-Phenyl-N-((S)-3,3-dimethylbut-2-yl)-P-(2-(phenylethynyl)phenyl)-phosphinic Amide (15b)

Isolated yield after chromatography (AcOEt/hexane 1:1) 85%. White solid; mp 115–117 °C; 1H NMR (300.13 MHz, CDCl3): δ 0.79 (s, 9H), 1.23 (d, 3JHH 6.4 Hz, 3H), 1.90 (br s, 1H), 3.35 (dc, 3JPH 8.8, 3JHH 7.2, Hz, 1H), 7.15–7.521 (m, 2H), 7.28–7.36 (m, 3H), 7.38–7.54 (m, 5H), 7.60–7.64 (m, 1H), 7.76–7.84 (m, 2H), 8.25–35 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 19.6 (d, 3JPC 2.5 Hz), 26.3, 34.6 (d, 3JPC 4.6 Hz), 55.0 (d, 2JPC 1.7 Hz), 88.9 (d, 3JPC 5.5 Hz), 95.9, 122.1, 124.2 (d, 2JPC 7.7 Hz), 128.2 (d, 3JPC 13.1 Hz), 128.3 (d, 3JPC 12.8 Hz), 128.4, 128.90, 131.2 (d, 4JPC 4.0 Hz), 131.2, 131.3 (d, 2JPC 10.5 Hz), 131.5 (d, 4JPC 2.9 Hz), 133.5 (d, 3JPC 25.9 Hz), 131.5 (d, 2JPC 8.9 Hz), 135.3 (d, 1JPC 128.0 Hz), 135.6 (d, 1JPC 121.9 Hz) ppm; 31P NMR (121.50 MHz, CDCl3): δ 24.6 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C26H29NOP, 402.1987; found, 402.1984.

(S)-P-Phenyl-N-((S)-3,3-dimethylbut-2-yl)-P-(2-((4-fluorophenyl)ethynyl) Phenyl) Phosphinic Amide (15c)

Isolated yield after chromatography (AcOEt/hexane 1:1) 98%. Pink oil; 1H NMR (300.13 MHz, CDCl3): δ 0.75 (s, 9H), 1.20 (d, 3JHH 6.4 Hz, 3H), 3.21–3.55 (m, 2H), 6.93–6.99 (m, 2H), 7.07–7.12 (m, 3H), 7.34–7.48 (m, 5H), 7.54–7.58 (m, 1H), 7.76–7.84 (m, 2H), 8.20–8.28 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 19.6 (d, 3JPC 2.5 Hz), 26.3, 34.6 (d, 3JPC 4.7 Hz), 55.0 (d, 2JPC 1.7 Hz), 88.6 (d, 3JPC 5.5, 6JFC 1.1 Hz), 94.8, 115.8 (d, 2JFC 22.1 Hz), 118.2 (d, 4JFC 3.6 Hz), 124.1 (d, 2JPC 7.7 Hz), 128.2 (d, 3JPC 13.1 Hz), 128.3 (d, 3JPC 11.5 Hz), 131.2 (d, 4JPC 3.3 Hz), 131.2 (d, 2JPC 10.6 Hz), 131.5 (d, 4JPC 2.9 Hz), 133.1 (d, 3JFC 8.4 Hz), 133.3 (d, 3JPC 9.9 Hz), 131.5 (d, 2JPC 7.3 Hz), 135.2 (d, 1JPC 128.2 Hz), 135.6 (d, 1JPC 122.2 Hz), 162.7 (d, 1JFC 250.9 Hz) ppm; 31P NMR (121.50 MHz, CDCl3): δ 24.5 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C26H28FNOP, 420.1893; found, 420.1890.

(S)-P-Phenyl-N-((S)-3,3-dimethylbut-2-yl)-P-(2-((3-methylphenyl)ethynyl) Phenyl) Phosphinic Amide (15d)

Isolated yield after chromatography (AcOEt/hexane 1:1) 89%. White solid. mp 99–101 °C; 1H NMR (300.13 MHz, CDCl3): δ 0.79 (s, 9H), 1.23 (d, 3JHH 6.4 Hz, 3H), 2.32 (s, 3H), 3.34–3.39 (m, 2H), 6.92 (s, 1H), 6.99 (d, 3JHH 6.3 Hz, 1H), 7.14–7.23 (m, 2H), 7.38–7.53 (m, 5H), 7.58–7.63 (m, 1H), 7.76–7.83 (m, 2H), 8.27–8.34 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 19.6 (d, 3JPC 2.4 Hz), 21.2, 26.3, 34.6 (d, 3JPC 4.5 Hz), 54.9 (s, 2JPC 1.7 Hz), 88.6 (d, 3JPC 5.5 Hz), 96.2, 121.6, 124.3 (d, 2JPC 7.7 Hz), 128.2 (d, 3JPC 12.5 Hz), 128.2 (d, 2JPC 10.3 Hz), 128.3, 129.8, 131.1, 131.3 (d, 3JPC 10.6 Hz), 131.5 (d, 4JPC 2.9 Hz), 131.2 (d, 4JPC 2.9 Hz), 133.3 (d, 3JPC 9.9 Hz), 133.6 (d, 2JPC 7.2 Hz), 135.6 (d, 1JPC 121.9 Hz), 135.3 (d, 1JPC 128.1 Hz), 138.1 ppm; 31P NMR (121.50 MHz, CDCl3): δ 24.7 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C27H31NOP, 416.2143; found, 416.2137.

(S)-P-Phenyl-N-((S)-3,3-dimethylbut-2-yl)-P-(2-((2-methoxyphenyl)ethynyl) Phenyl) Phosphinic Amide (15e)

Isolated yield after chromatography (AcOEt/hexane 1:1) 95%. Pale yellow solid. mp 110–112 °C; 1H NMR (300.13 MHz, CDCl3): δ 0.75 (s, 9H), 1.28 (d, 3JHH 6.4 Hz, 3H), 3.46 (ddq, 3JHH 10.4, 3JHH = 3JPH 6.8 Hz, 1H), 3.34–3.39 (dd, 2JPH 16.0, 3JHH 10.4 Hz, 1H), 6.81–6.90 (d, 2H), 7.21–7.38 (m, 5H), 7.46–7.50 (m, 2H), 7.60–7.64 (m, 1H), 7.73–7.81 (m, 2H), 8.27–8.34 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 19.9 (d, 3JPC 2.6 Hz), 26.3, 34.6 (d, 3JPC 3.9 Hz), 54.9 (d, 2JPC 1.4 Hz), 55.3, 92.7, 92.8 (d, 3JPC 5.7 Hz), 110.5, 111.45, 120.6, 124.7 (d, 2JPC 7.7 Hz), 127.9 (d, 3JPC 13.1 Hz), 128.1 (d, 3JPC 11.5 Hz), 130.3, 131.0 (d, 4JPC 2.4 Hz), 131.1 (d, 2JPC 10.6 Hz), 131.3 (d, 4JPC 3.0 Hz), 133.3 (d, 3JPC 10.9 Hz), 133.4, 133.7 (d, 2JPC 7.2 Hz), 135.6 (d, 1JPC 126.9 Hz), 135.6 (d, 1JPC 122.0 Hz), 159.6 ppm; 31P NMR (121.50 MHz, CDCl3): δ 25.1 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C27H31NO2P, 432.2092; found, 432.2096.

(S)-P-Phenyl-N-((S)-3,3-dimethylbut-2-yl)-P-(2-((3,5-trifluoromethylphenyl) Ethynyl)phenyl) Phosphinic Amide (15f)

Isolated yield after chromatography (AcOEt/hexane 1:1) 75%. White solid. mp 131–133 °C; 1H NMR (300.13 MHz, CDCl3): δ 0.78 (s, 9H), 1.25 (d, 3JHH 6.4 Hz, 3H), 3.00 (dd, 2JPH 14.4, 3JHH 10.2 Hz, 1H), 3.21–3.35 (m, 1H), 7.42–7.48 (m, 4H), 7.51–7.67 (m, 4H), 7.72–7.81 (m, 3H), 8.24–8.31 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 19.6 (d, 3JPC 2.3 Hz), 26.2, 34.6 (d, 3JPC 3.9 Hz), 55.4 (d, 2JPC 1.4 Hz), 91.9 (d, 3JPC 5.9 Hz), 92.6, 122.1 (d, 4JFC 13.1 Hz), 122.2 (d, 1JFC 184.2 Hz), 122.2 (d, 2JFC 96.2 Hz), 124.6 (d, 3JFC 4.8 Hz), 128.5 (d, 3JPC 13.1 Hz), 129.2 (d, 3JPC 11.4 Hz), 131.3 (d, 2JPC 24.5 Hz), 131.4 (d, 2JPC 10.8 Hz), 131.4 (d, 4JPC 2.4 Hz), 131.9 (d, 4JPC 2.4 Hz), 132.00 (d, 3JFC 33.8 Hz), 133.6 (d, 2JPC 3.0 Hz), 134.0 (d, 3JPC 7.3 Hz), 134.7 (d, 1JPC 127.8 Hz), 135.8 (d, 1JPC 135.8 Hz) ppm; 31P NMR (121.50 MHz, CDCl3): δ 24.3 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C28H27F6NOP, 538.1735; found, 538.1747.

(S)-P-Phenyl-N-((S)-3,3-dimethylbut-2-yl)-P-(2-((2-(hydroxymethyl)phenyl) Ethynyl) Phenyl) Phosphinic Amide (15g)

Isolated yield after chromatography (AcOEt/hexane 3:2) 84%. Clear oil; 1H NMR (300.13 MHz, CDCl3): δ 0.77 (s, 9H), 1.15 (d, 3JHH 6.3 Hz, 3H), 3.14–3.33 (m, 2H), 4.51 (d, 3JHH 13.1 Hz, 1H), 4.63 (d, 3JHH 13.1 Hz, 1H), 7.16–7.28 (m, 3H), 7.34–7.49 (m, 6H), 7.60–7.64 (m, 1H), 7.75–7.82 (m, 2H), 7.85–7.93 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 19.1 (d, 3JPC 2.6 Hz), 26.3, 34.7 (d, 3JPC 5.0 Hz), 55.8 (d, 2JPC 2.3 Hz), 63.2, 92.4 (d, 3JPC 5.6 Hz), 94.0, 121.3, 125.5 (d, 3JPC 7.2 Hz), 127.1, 128.0 (d, 3JPC 12.0 Hz), 128.2, 128.4 (d, 3JPC 13.0 Hz), 129.0, 131.4 (d, 4JPC 2.4 Hz), 131.9, 132.0 (d, 4JPC 2.1 Hz), 132.0 (d, 2JPC 7.3 Hz), 133.1 (d, 2JPC 8.7 Hz), 133.6 (d, 1JPC 128.6 Hz), 134.2 (d, 3JPC 10.0 Hz), 134.4 (d, 1JPC 125.0 Hz), 144.4 ppm; 31P NMR (121.50 MHz, CDCl3): δ 25.6 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C27H31NO2P, 432.2092; found, 432.2083.

General Procedure Applied for the Pd-Catalyzed Sonogashira Reactions

To a stirred suspension of the corresponding ortho-iodine derivative 16 (0.28 mmol; 1 equiv), PdCl2(PPh3)2 (2%; 0.006 mmol; 5 mg), and CuI (1%; 0.003 mmol; 1 mg) in Et3N (1 mL), the corresponding alkyne 14 (1.2 equiv) was added dropwise. Then, the mixture was heated to 50 °C and stirred overnight. In order to get rid of the metals, the reaction crude was dissolved in CH2Cl2 (2–5 mL) and filtered through Celite. The solution was then washed with 1 M HCl (2 × 2 mL), and the isolated organic layer was dried over anhydrous MgSO4 and filtered. After evaporation of the solvent, the crude product (RP,RC)-15 was purified by column chromatography in silica gel eluting with mixtures AcOEt/hexane.

(R)-P-Phenyl-N-((R)-1-phenylethyl)-P-(2-(trimethylsilylethynyl)phenyl) Phosphinic Amide (15h)

Isolated yield after chromatography (AcOEt/hexane 1:2) 86%. Clear oil: 1H NMR (300.13 MHz, CDCl3): δ 0.02 (s, 9H), 1.63 (d, 3JHH 6.9 Hz, 3H), 3.79 (dd, 2JPH 9.5 Hz, 3JHH 9.5 Hz, 1H), 4.70 (ddc, 3JHH 7.9 Hz, 3JPH 7.5 Hz, 3JHH 7.1 Hz, 1H), 7.1–7.5 (m, 11H), 7.74 (m, 2H), 8.16 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ −0.73, 25.25 (d, 3JPC 6.0 Hz), 50.68 (d, 2JPC 1.0 Hz), 101.84, 104.26 (d, 3JPC 6.0 Hz), 124.35 (d, 2JPC 8.3 Hz), 126.13, 126.89, 128.14 (d, 3JPC 13.4 Hz), 128.14, 128.33 (d, 3JPC 11.1 Hz), 131.01 (d, 4JPC 2.8 Hz), 131.11 (d, 2JPC 11.1 Hz), 131.69 (d, 4JPC 2.8 Hz), 133.56 (d, 3JPC 9.7 Hz), 134.10 (d, 1JPC 129.5 Hz), 134.19 (d, 2JPC 6.9 Hz), 134.62 (d, 1JPC 117.9 Hz),144.48 (d, 3JPC 4.2 Hz) ppm; 31P NMR (121.5 MHz, CDCl3): δ 24.52 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C25H28NOPSi, 418.1756; found, 418.1759.

(R)-P-Phenyl-N-((R)-1-phenylethyl)-P-(2-(phenylethynyl)phenyl)phosphinic Amide (15i)

Isolated yield after chromatography (AcOEt/hexane 1:2) 92%. Oil; 1H NMR (300.13 MHz, CDCl3): δ 1.59 (d, 3JHH 6.6 Hz, 3H), 3.71 (dd, 2JPH 9.1 Hz, 3JHH 8.3 Hz, 1H), 4.70 (m, 1H), 7.1–7.5 (m, 15H), 7.86 (m, 2H), 8.18 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 25.47 (d, 3JPC 5.1 Hz), 50.83, 88.65 (d, 3JPC 5.5 Hz), 96.04, 122.15, 124.77 (d, 2JPC 7.4 Hz), 126.06, 126.90, 128.08 (d, 3JPC 11.6 Hz), 128.26 (d, 3JPC 13.0 Hz), 128.23, 128.29, 128.74, 131.16, 131.24 (d, 4JPC 2.3 Hz), 131.42 (d, 2JPC 10.6 Hz), 131.80 (d, 4JPC 2.8 Hz), 133.36 (d, 3JPC 9.7 Hz), 133.57 (d, 1JPC 129.9 Hz), 134.28 (d, 2JPC 7.4 Hz), 134.02 (d, 1JPC 120.2 Hz), 144.57 (d, 3JPC 4.6 Hz) ppm; 31P NMR (121.5 MHz, CDCl3): δ 24.05 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C28H24NOP, 422.1674; found, 422.1671.

(R)-P-Phenyl-N-((R)-1-phenylethyl)-P-(2-((4-fluorophenyl)ethynyl)phenyl) Phosphinic Amide (15j)

Isolated yield after chromatography (AcOEt/hexane 1:1.5) 94%. Oil; 1H NMR (300.13 MHz, CDCl3): δ 1.58 (d, 3JHH 6.7 Hz, 3H), 3.62 (dd, 2JPH 9.5 Hz, 3JHH 8.3 Hz, 1H), 4.58 (m, 1H), 6.9–7.5 (m, 15H), 7.84 (m, 2H), 8.12 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 25.50 (d, 3JPC 5.1 Hz), 50.90, 88.28 (d, 3JPC 5.6 Hz), 94.92, 115.60 (d, 2JFC 22.2 Hz), 118.28 (d, 4JFC 3.2 Hz), 124.73 (d, 3JPC 7.9 Hz), 126.03, 126.94, 128.11 (d, 3JPC 10.6 Hz), 128.26 (d, 3JPC 12.9 Hz), 128.29, 131.27 (d, 4JPC 2.3 Hz), 131.45 (d, 3JPC 10.6 Hz), 131.81 (d, 4JPC 2.8 Hz), 133.12 (d, 3JFC 8.3 Hz), 133.32 (d, 2JPC 10.2 Hz), 134.27 (d, 3JPC 7.4 Hz), 144.61 (d, 3JPC 5.1 Hz), 162.65 (d, 1JFC 250.6 Hz) ppm; 31P NMR (121.5 MHz, CDCl3): δ 24.10 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C28H23FNOP, 440.1580; found 440.1589.

(R)-P-Phenyl-N-((R)-1-phenylethyl)-P-(2-((2-methoxyphenyl)ethynyl)phenyl)-phosphinic Amide (15k)

Yield after chromatography (AcOEt/hexane 1:1.5) 95%. Oil; 1H NMR (300.13 MHz, CDCl3): δ 1.63 (d, 3JHH 6.7 Hz, 3H), 3.66 (s, 3H), 4.66 (m, 1H), 4.77 (m, 1H), 6.77 (d, 3JHH 8.5 Hz, 1H), 6.86 (m, 2H), 6.9–7.5 (m, 13H), 7.79 (m, 2H), 8.22 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 25.03 (d, 3JPC 6.5 Hz), 50.90, 55.02, 92.66, 92.75 (d, 3JPC 6.0 Hz), 110.30, 111.47, 120.56, 125.05 (d, 2JPC 8.3 Hz), 126.33, 126.62, 127.79, 127.87 (d, 3JPC 12.9 Hz), 127.89 (d, 3JPC 10.6 Hz), 130.09, 130.93 (d, 2JPC 10.6 Hz), 130.98 (d, 4JPC 2.8 Hz), 131.52 (d, 4JPC 2.8 Hz), 132.94 (d, 3JPC 9.7 Hz), 133.14, 134.61 (d, 2JPC 6.9 Hz), 133.87 (d, 1JPC 123.9 Hz), 133.95 (d, 1JPC 122.5 Hz), 144.41 (d, 3JPC 4.2 Hz), 159.46 ppm; 31P NMR (121.5 MHz, CDCl3): δ 24.30 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C29H26NO2P, 452.1779; found, 452.1821.

General Procedure Applied for Intramolecular Cyclization Promoted by TBAF

To a solution of the corresponding ortho-alkyne derivative 15 (0.15 mmol; 1 equiv) in THF (5 mL; 0.03 M), TBAF (0.18 mL of a 1M solution in THF; 0.18 mmol; 1.2 equiv) was added. The reaction was completed after an hour of stirring at rt. The crude mixture was washed with H2O (2 × 5 mL), extracted with CH2Cl2 (2 × 5 mL), and dried over anhydrous Na2SO4. Solvent evaporation under vacuum furnished the crude product 17, which was later purified through a short silica column.

(S)-3-Methylene-1-phenyl-2-((S)-3,3-dimethylbut-2-yl)-2,3-dihydrobenzo[c][1,2] Azaphosphole 1-Oxide (17a)

Isolated yield after chromatography (AcOEt/hexane 1:1) 74%. White solid. mp 128–129 °C (diethyl ether/hexane 1:1); 1H NMR (300.13 MHz, CDCl3): δ 1.13 (s, 9H), 1.17 (d, 3JHH 7.2 Hz, 3H), 1.61 (d, 3JHH 7.2 Hz, 3H), 3.36–3.46 (m, 2H), 4.59 (d, 3JHH 1.9 Hz, 1H), 4.74 (d, 3JHH 2.5 Hz, 1H), 5.11 (dd, 3JPH 7.2, 3JHH 2.5 Hz, 1H), 5.16 (dd, 3JPH 5.7, 3JHH 1.9 Hz, 1H), 7.38–7.44 (m, 6H), 7.48–7.50 (m, 2H), 7.53–7.66 (m, 8H), 7.75–7.78 (m, 2H) ppm; 13C NMR (75.47 MHz, CDCl3): data for major isomer: δ 12.7 (d, 3JPC 2.4 Hz), 29.2, 36.79 (d, 3JPC 3.9 Hz), 58.4 (d, 2JPC 4.9 Hz), 87.9 (d, 3JPC 8.8 Hz), 129.1 (d, 2JPC 12.7 Hz), 131.1 (d, 3JPC 13.2 Hz), 132.0 (d, 4JPC 3.0 Hz), 132.1 (d, 4JPC 2.9 Hz), 132.2 (d, 3JPC 10.8 Hz), 132.8 (d, 2JPC 10.8 Hz), 141.1 (d, 1JPC 152.0 Hz), 141.4 (d, 1JPC 156.2 Hz) ppm; 31P NMR (121.5 MHz, CDCl3): δ 33.5, 34.6 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C20H25NOP, 326.1668; found, 326.1672.

(S)-3-((E)-Benzylidene)-1-phenyl-2-((S)-3,3-dimethylbut-2-yl)-2,3-dihydrobenzo[c][1,2] Azaphosphole 1-Oxide (17b)

Isolated yield after chromatography (AcOEt/hexane 1:1) 73%. Yellow oil; dr 74:26; 1H NMR (300.13 MHz, CDCl3): δ 1.21 (s, 9H), 1.37 (d, 3JHH 7.1 Hz, 3H), 4.12 (dq, 3JPH 19.9 Hz, 3JHH 7.1 Hz, 1H), 6.71 (d, 3JHH 2.1 Hz, 1H), 7.34–7.69 (m, 11H), 7.76–7.81 (m, 2H), 7.83 (dd, 3JHH 8.1 Hz, 4JPH 2.5 Hz, 2H) ppm; 13C NMR (75.47 MHz, CDCl3): data for major isomer: δ 16.2 (d, 3JPC 2.2 Hz), 26.6, 34.79, 59.6, 103.9 (d, 3JPC 6.2 Hz), 120.5, 126.4, 127.4 (d, 2JPC 13.0 Hz), 128.0 (d, 3JPC 13.6 Hz), 128.0 (d, 3JPC 14.3 Hz), 128.1, 128.9 (d, 3JPC 22.3 Hz), 130.6 (d, 1JPC 100.1 Hz), 130.1, 131.8 (d, 4JPC 2.4 Hz), 131.9 (d, 4JPC 3.3 Hz), 132.8 (d, 2JPC 11.2 Hz), 133.3 (d, 1JPC 130.5 Hz), 137.9, 140.2 (d, 2JPC 15.6 Hz), 141.3 (d, 2JPC 14.2 Hz), ppm; 31P NMR (121.5 MHz, CDCl3): δ 34.9 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C26H29NOP, 402.1987; found, 402.1985.

(S)-3-((E)-4-Fluorobenzylidene)-1-phenyl-2-((S)-3,3-dimethylbut-2-yl)-2,3-dihydrobenzo[c][1,2] Azaphosphole 1-Oxide (17c)

Isolated yield after chromatography (AcOEt/hexane 1:2) 74%. Yellow oil; dr 92:8; 1H NMR (300.13 MHz, CDCl3): δ 0.46 (s, 9H), 1.37 (d, 3JHH 7.1 Hz, 3H), 4.12 (dq, 3JPH 19.9, 3JHH 7.2 Hz, 1H), 6.61 (s, 1H), 7.03–7.09 (m, 2H), 7.28–7.34 (m, 2H), 7.38–7.59 (m, 6H), 7.67–7.74 (m, 2H), 7.80 (dd, 3JHH 8.1 Hz, 4JPH 2.4 Hz, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 15.8 (d, 3JPC 2.1 Hz), 27.61, 35.5, 61.5, 102.5 (d, 3JPC 7.6 Hz), 115.2 (d, 2JFC 21.4 Hz), 120.4 (d, 2JPC 11.0 Hz), 127.4 (d, 2JPC 11.4 Hz), 128.4 (d, 2JPC 13.3 Hz), 129.0 (d, 3JPC 12.9 Hz), 129.3 (d, 1JPC 100.1 Hz), 131.1 (d, 2JPC 7.9 Hz), 131.9 (d, 4JPC 2.4 Hz), 132.0 (d, 4JPC 2.4 Hz), 132.8 (d, 3JFC 10.7 Hz), 132.9 (d, 4JFC 4.0 Hz), 133.2 (d, 1JPC 130.4 Hz), 140.7 (d, 2JPC 16.0 Hz), 141.2 (d, 2JPC 14.4 Hz), 161.7 (d, 1JFC 247.7 Hz) ppm; 31P NMR (121.5 MHz, CDCl3): δ 35.0 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C26H28FNOP, 420.1893; found, 420. 1895.

(S)-3-((E)-3-Methylbenzylidene)-1-phenyl-2-((S)-3,3-dimethylbut-2-yl)-2,3-dihydrobenzo[c][1,2] Azaphosphole 1-Oxide (17d)

Isolated yield after chromatography (AcOEt/hexane 1:1) 69%. Clear oil; dr 70:30; 1H NMR (300.13 MHz, CDCl3): δ 0.47 (s, 9H), 1.36 (d, 3JHH 7.1 Hz, 3H), 2.37 (s, 3H), 4.13 (dq, 3JPH 20.3 Hz, 3JHH 7.1 Hz, 1H), 6.69 (d, 4JPH 1.6 Hz, 1H), 7.07–7.59 (m, 5H), 7.37–7.59 (m, 6H), 7.80–7.83 (m, 2H), 7.80 (dd, 3JHH 8.1 Hz, 4JPH 2.5 Hz, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 15.8 (d, 3JPC 2.1 Hz), 21.34, 27.6, 35.4, 61.5, 103.9 (d, 3JPC 7.6 Hz), 120.3, 120.5, 126.4, 127.4 (d, 2JPC 13.0 Hz), 127.6 (d, 3JPC 14.3 Hz), 128.3 (d, 3JPC 13.6 Hz), 128.1, 128.8 (d, 2JPC 12.9 Hz), 130.6 (d, 1JPC 92.1 Hz), 130.1, 131.8 (d, 4JPC 2.4 Hz), 131.9 (d, 4JPC 3.3 Hz), 132.8 (d, 2JPC 10.8 Hz), 133.4 (d, 1JPC 130.5 Hz), 137.7, 140.2 (d, 2JPC 15.7 Hz), 141.3 (d, 2JPC 14.5 Hz) ppm; 31P NMR (121.5 MHz, CDCl3): δ 35.1 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C27H31NOP, 416.2143; found, 416.2141.

(S)-3-((E)-2-Methoxybenzylidene)-1-phenyl-2-((S)-3,3-dimethylbut-2-yl)-2,3-dihydrobenzo[c][1,2] Azaphosphole 1-Oxide (17e)

Isolated yield after chromatography (AcOEt/hexane 1:1) 88%. Yellow oil; dr 81:19; 1H NMR (300.13 MHz, CDCl3): δ 0.42 (s, 9H), 1.39 (d, 3JHH 7.1 Hz, 3H), 3.87 (s, 3H), 4.02–4.17 (m, 1H), 6.55 (d, 4JPH 2.1 Hz, 1H), 6.89–6.98 (m, 2H), 7.19–7.59 (m, 9H), 7.70–7.77 (m, 2H), 7.80 (dd, 3JHH 8.1 Hz, 4JPH 2.5 Hz, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 16.2 (d, 3JPC 2.3 Hz), 27.5, 35.4, 55.3, 61.3, 100.7 (d, 3JPC 7.7 Hz), 110.3, 110.0, 120.7 (d, 3JPC 11.2 Hz), 125.4, 127.3 (d, 2JPC 12.0 Hz), 128.3 (d, 3JPC 13.4 Hz), 128.5, 128.7 (d, 3JPC 13.0 Hz), 130.5 (d, 1JPC 109.6 Hz), 133.4, 131.7 (d, 4JPC 2.4 Hz), 131.8 (d, 4JPC 3.0 Hz), 132.9 (d, 2JPC 10.8 Hz), 131.9 (d, 1JPC 115.9 Hz), 140.8 (d, 2JPC 16.0 Hz), 141.4 (d, 2JPC 14.4 Hz), 157.0 ppm; 31P NMR (121.5 MHz, CDCl3): δ 34.6 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C27H31NO2P, 432.2092; found, 432.2096.

(R)-3-Methylene-1-phenyl-2-((R)-1-phenylethyl)-2,3-dihydrobenzo[c][1,2] Azaphosphole 1-Oxide (17f)

Isolated yield after chromatography (AcOEt/hexane 1:4) 88%. Oil; 1H NMR (300.13 MHz, CDCl3): δ 1.68 (d, 3JHH 7.2 Hz, 3H), 4.26 (d, 3JHH 2.2 Hz, 1H), 4.94 (dd, 3JHH 2.2 Hz, 4JPH 2.4 Hz, 1H), 5.05 (dq, 3JPH 9.2 Hz, 3JHH 7.2 Hz, 1H), 7.0–7.7 (m, 14H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 17.16 (d, 3JPC 2.3 Hz), 52.07 (d, 2JPC 2.3 Hz), 86.59 (d, 3JPC 7.4 Hz), 120.96 (d, 3JPC 10.2 Hz), 127.08, 127.33, 127.68 (d, 3JPC 12.5 Hz), 128.14, 128.26 (d, 3JPC 13.9 Hz), 129.34 (d, 3JPC 12.9 Hz), 131.92 (d, 4JPC 2.8 Hz), 132.05 (d, 4JPC 2.3 Hz), 132.38 (d, 3JPC 11.6 Hz), 131.01 (d, 1JPC 115.6 Hz), 139.38 (d, 3JPC 13.9 Hz), 140.20 (d, 3JPC 2.8 Hz), 142.13 (d, 2JPC 17.6 Hz) ppm; 31P NMR (121.50 MHz, CDCl3): δ 32.90 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C22H20NOP, 346.1361; found, 346.1364.

(R)-3-((E)-Benzylidene)-1-phenyl-2-((R)-1-phenylethyl)-2,3-dihydrobenzo[c] [1,2]azaphosphole 1-Oxide (17g)

Isolated yield after chromatography (AcOEt/hexane 1:4) 95%; dr 5:1; 1H NMR (300.13 MHz, CDCl3): δ 1.61 (d, 3JHH 6.8 Hz, 3H), 5.15 (dc, 3JPH 18.4 Hz, 3JHH 6.8 Hz, 1H), 6.74 (d, 4JPH 2.8 Hz, 1H), 6.9–7.7 (m, 18H), 7.88 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 17.85, 53.21 (d, 2JPC 2.3 Hz), 102.33 (d, 3JPC 7.9 Hz), 120.57 (d, 3JPC 11.1 Hz), 127.09, 127.23, 127.48 (d, 3JPC 12.5 Hz), 127.61 (d, 3JPC 13.9 Hz), 128.16, 128.62, 129.08, 129.35, 130.90 (d, 4JPC 2.8 Hz), 131.48 (d, 2JPC 11.6 Hz), 131.89 (d, 4JPC 2.3 Hz), 132.53 (d, 2JPC 11.1 Hz), 132.15 (d, 1JPC 132.2 Hz), 136.56, 137.94 (d, 2JPC 16.2 Hz), 138.21 (d, 3JPC 1.9 Hz), 140.62 (d, 2JPC 15.3 Hz) ppm; 31P NMR (121.50 MHz, CDCl3): δ 35.31 (82%), 31.68 (18%) ppm; HRMS-ESI (m/z): [M + H]+ calcd for C28H24NOP, 422.1674; found 422.1665.

(R)-3-((E)-4-Fluorobenzylidene)-1-phenyl-2-((R)-1-phenylethyl)-2,3-dihydrobenzo[c] [1,2]azaphosphole 1-Oxide (17h)

Isolated yield after chromatography (AcOEt/hexane 1:4) 85%. Oil; dr 10:1; 1H NMR (300.13 MHz, CDCl3): δ 1.62 (d, 3JHH 6.9 Hz, 3H), 5.12 (dc, 3JPH 17.9 Hz, 3JHH 6.9 Hz, 1H), 6.66 (br s, 1H), 6.9–7.6 (m, 17H), 7.86 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 18.01, 53.35 (d, 2JPC 2.3 Hz), 101.12 (d, 3JPC 7.9 Hz), 115.14 (d, 2JFC 21.3 Hz), 120.54 (d, 3JPC 11.1 Hz), 127.14, 127.32, 127.52 (d, 3JPC 12.5 Hz), 127.67 (d, 3JPC 13.9 Hz), 128.84, 129.10 (d, 3JPC 12.9 Hz), 130.90 (d, 3JPC 7.9 Hz), 131.00 (d, 4JPC 3.2 Hz), 131.52 (d, 3JFC 11.6 Hz), 131.94 (d, 4JPC 2.3 Hz), 132.06 (d, 1JPC 132.2 Hz), 132.42 (d, 4JFC 3.7 Hz), 138.16 (d, 3JPC 8.8 Hz), 138.28 (d, 3JPC 5.6 Hz), 140.49 (d, 2JPC 15.3 Hz), 161.59 (d, 1JFC 246.92 Hz) ppm; 31P NMR (121.50 MHz, CDCl3): δ 35.30 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C28H23FNOP, 440.1580; found, 440.1587.

(R)-3-((E)-2-Methoxybenzylidene)-1-phenyl-2-((R)-1-phenylethyl)-2,3-dihydrobenzo [c][1,2]azaphosphole 1-Oxide (17i)

Isolated yield after chromatography (AcOEt/hexane 1:4) 89%. Oil; dr 2.5:1; 1H NMR (300.13 MHz, CDCl3): δ 1.61 (d, 3JHH 6.9 Hz, 3H), 3.88 (s, 3H), 5.15 (dc, 3JPH 17.9 Hz, 3JHH 6.9 Hz, 1H), 6.60 (d, 4JPH 2.8 Hz, 1H), 6.91–7.72 (m, 17H), 7.91 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 17.96, 53.23 (d, 2JPC 2.1 Hz), 55.35, 98.41 (d, 3JPC 7.6 Hz), 110.41, 120.08, 120.85 (d, 3JPC 10.7 Hz), 125.06, 126.93, 127, 127.33, 127.53 (d, 3JPC 13.7 Hz), 128.73 (d, 3JPC 13.2 Hz), 129.15, 130.80 (d, 4JPC 3.1 Hz), 131.12, 131.60 (d, 3JPC 11.2 Hz), 131.72 (d, 4JPC 2.1 Hz), 132.47 (d, 1JPC 132.2 Hz), 132.56 (d, 3JPC 11.2 Hz), 138.30 (d, 3JPC 15.8 Hz), 140.66 (d, 3JPC 5.1 Hz), 140.73 (d, 2JPC 15.3 Hz), 157.12 ppm; 31P NMR (121.50 MHz, CDCl3): δ 34.82 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C29H26NO2P, 452.1779; found, 452.1774.

(S)-P-(2-(1H-Isochromen-3-yl)phenyl)-P-phenyl-N-((S)-3,3-dimethylbut-2-yl)phosphinic Amide (18)

Isolated yield after chromatography (AcOEt/hexane 1:1) 74%. Oil; 1H NMR (300.13 MHz, CDCl3): δ 0.87 (s, 9H), 1.10 (d, 3JHH 6.6 Hz, 3H), 2.84 (t, 3JHH = 2JPH 9.3 Hz, 1H), 3.05–3.13 (m, 1H), 5.41 (s, 1H), 7.10 (ddd, 3JHH 7.5 Hz, 3JPH 2.6 Hz, 4JHH 1.2 Hz, 1H), 7.14 (s, 1H), 7.30–7.39 (m, 3H), 7.44–7.64 (m, 6H), 7.89–7.97 (m, 2H), 8.32–8.36 (m, 1H) ppm; 13C NMR (75.47 MHz, CDCl3): δ 18.9 (d, 3JPC 2.7 Hz), 26.5, 34.7 (d, 3JPC 5.0 Hz), 55.9 (d, 2JPC 2.3 Hz), 75.0, 94.5 (d, 4JPC 5.6 Hz), 120.9, 121.0, 124.5 (d, 3JPC 13.2 Hz), 128.1 (d, 2JPC 7.1 Hz), 120.4, 129.0 (d, 1JPC 124.8 Hz), 129.1, 129.5 (d, 2JPC 10.4 Hz), 131.4 (d, 4JPC 2.6 Hz), 131.5 (d, 4JPC 2.9 Hz), 132.7 (d, 3JPC 9.5 Hz), 132.9 (d, 3JPC 11.1 Hz), 133.8 (d, 1JPC 128.1 Hz), 134.7, 139.2, 139.7 (d, 2JPC 7.7 Hz), 157.3 ppm; 31P NMR (121.50 MHz, CDCl3): δ 27.3 ppm; HRMS-ESI (m/z): [M + H]+ calcd for C27H31NO2P, 432.2092; found, 432.2085.

Acknowledgments

This work is dedicated to Professor V. Gotor on the occasion of his 70th birthday. We thank the MINECO and FEDER program for financial support (project CTQ2014-57157-P). We thank Dr. Antonio Llamas Saiz for his help in the analysis of X-ray diffraction data. E.B.S. thanks MICINN for a Ph.D. fellowship.

Supporting Information Available

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b00491.

  • Copies of NMR spectra of all new compounds and ORTEP diagram and crystallographic information for compounds 12 and 17a (PDF)

  • Crystallographic information for compound 12 (deposited as CCDC 1579088) (CIF)

  • Crystallographic information for compound 17a (deposited as CCDC 1573376) (CIF)

The authors declare no competing financial interest.

Supplementary Material

ao8b00491_si_001.pdf (7.6MB, pdf)
ao8b00491_si_002.cif (469.5KB, cif)
ao8b00491_si_003.cif (177.1KB, cif)

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ao8b00491_si_001.pdf (7.6MB, pdf)
ao8b00491_si_002.cif (469.5KB, cif)
ao8b00491_si_003.cif (177.1KB, cif)

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