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. 2016 Aug 25;1(2):251–263. doi: 10.1021/acsomega.6b00185

CuBr–ZnI2 Combo-Catalysis for Mild CuI–CuIII Switching and sp2 C–H Activated Rapid Cyclization to Quinolines and Their Sugar-Based Chiral Analogues: A UV–Vis and XPS Study

Ramij R Mondal 1, Saikat Khamarui 1, Dilip K Maiti 1,*
PMCID: PMC6640751  PMID: 31457128

Abstract

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An unprecedented CuBr–ZnI2 combo-catalyzed mild Cu1–CuIII switching activation of sp2 C–H of highly electron-rich arenes is reported. Anilines, aldehydes, and terminal alkynes were rapidly coupled together at ambient temperature to construct a ubiquitous quinoline framework through cyclization of the C≡C bond. This smart solvent-free strategy was exploited for the direct synthesis of valuable 4-substituted, 2,4-disubstituted, and thermally labile sugar-based chiral quinolines in good yields. In contrast to the frequently used imine–alkyne cyclization reaction, this uncommonly mild CuI–CuIII combo-catalysis for a rapid three-component cyclization is expected to proceed through the formation of a flexible propargyl amine intermediate, which provides a CuI-procatalyst for rapid sp2 C–H activation with cyclization involving transient CuIII species. The in situ generation of transient CuIII species was confirmed through online ultraviolet–visible spectroscopy (UV–vis), electrospray ionization mass spectrometry (ESI-MS), and X-ray photoelectron spectroscopy (XPS) analyses.

Introduction

Direct sp2 C–H metallation1−8 is an active area of research because it can be used for efficient functionalization of arenes without the use of specially designed, halogenated, and/or hazardous precursors. In general, sp2 C–H activation of arenes requires high temperatures, which greatly hampers achieving the desired selectivity and obtaining thermally labile compounds such as valuable sugar-based chiral compounds. Thus, activating an sp2 C–H bond, especially in electron-rich arenes such as anilines,9−13 under mild conditions is desirable and will open up new opportunities toward the selective construction of ubiquitous heterocycles such as quinolines and their valuable chiral analogues through multicomponent14−16 domino cyclization17−23 reactions. In this regard, we envisaged the development and exploitation of a new CuI–CuIII switching catalysis24−30 under mild conditions, which would efficiently deliver C–H-activated C–C/C–X bonds to form functional groups with tandem cyclization toward an unprecedented general synthesis of quinolones, with an improved reaction rate, selectivity, and substrate scope. The mechanisms of the widely used catalysis with CuI-compounds24−35 that pass through a CuI–CuIII transition have not been thoroughly investigated. The scope of the reported C–H metallation through a CuI–CuIII transition31−35 is also limited because of high temperatures and/or stringent reaction conditions.

Chirality plays a pivotal role in the lives of plants and animals, such as in biochemical transformations and the functioning of drugs.36−38 Naturally occurring chiral cinchona alkaloids bearing a quinoline motif and other chiral analogues are used as “lead” and antimalarial drugs, chiral architecture for materials, and asymmetric catalysts.39−43 Sugar-based chiral quinolines have recently been used as a new antioxidant modulator for amyloid aggregation, an Hg2+-sensor, and potent antimicrobial, antituberculosis, and DNA-intercalating antitumor agents (A–E, Figure 1).44−48 In light of the diverse applications of chiral quinolines, a few methods have been developed for their preparation: Friedländer condensation using costly precursors consisting of β-C-glycosidic ketones and 2-aminobenzaldehyde derivatives to form methylene-bridged sugar quinolines upon heating in the presence of pyrrolidine (25 mol %),45 CuI-catalyzed sugar-based alkyne–azide quinoline cycloaddition to 1,2,3-triazole-bridged chiral quinolines,46 and PPh3AuCl (10 mol %)–AgSbF6 (10 mol %)-catalyzed propargyl sugar aldehyde and aniline cycloaddition to quinoline-pyrano-fused sugars,47 as well as a few other methods.48 Quinolines directly attached to the chiral centers such as quinine analogues are used in antimalarial and other medical applications. In this regard, sugar molecules directly attached to the quinoline skeleton are potential drug candidates. To the best of our knowledge, synthesis of 2-substituted sugar-based chiral quinolines is unknown in the literature. Thus, the development of a simple and mild strategy toward the direct synthesis of acidic and thermally sensitive 2-substituted sugar-based chiral quinolines will be a valuable addition to the existing modern synthetic approaches to quinolines.

Figure 1.

Figure 1

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2-Substituted (A–D) and 2,3-fused (E) bioactive sugar-based quinolines.

The synthesis of achiral quinolines, such as transition metal-catalyzed cyclization49−54 and alkyne–imine addition reactions,55−57 is well-documented in the literature.58−63 However, instead of making unstable imines through cumbersome approaches, development of an in situ coupling strategy using amines, aldehydes, and terminal alkynes and easy metallation to the ortho-sp2 C–H through coordination of the triple bond of the in situ-generated flexible propargyl amine (I, Scheme 1) moiety will be a valuable addition to the existing methods for the synthesis of chiral quinolines directly attached to sugars under mild conditions. In this context, the combination of two catalysts will be more useful for the direct N–C and C–C coupling of an aldehyde–carbon (3) with an amine (1) and a terminal alkyne (2). Combo-catalysis is an emerging area, and we64−66 and others67−71 have established it as a powerful tool in modern organic synthesis. For instance, the diverse cyclization reactions catalyzed by VO(acac)2–CeCl3, Ni(0)–Cu(I), and MoVI–CeCl3 developed by our group provide easy access to a wide range of heterocycles.64−66 CuBr–ZnI2-mediated N–N/C–N coupling for oxidative cyclization,67 PdI–RuI-mediated Suzuki cross-coupling reactions,68 AuClLn–AgSbF6-tuned C–C coupled aromatization,69 Ti–Cr-catalyzed polymerization reactions,70 and [IrCuCl2]2–AgNTf2-guided amination71 through sp2 C–H activation are very useful in the synthesis of combo-catalysis functionalized and sugar-based optically pure quinolines (4) under mild reaction conditions, with a significantly improved reaction rate, yield, and selectivity (without 5). Interestingly, Cu(I/II) compounds72−77 and organozinc(II)78 were reported as active catalysts for the coupling of secondary aliphatic amines with aldehydes and alkynes with the respective propargyl amines.

Scheme 1. Combo-Catalysis for Mild sp2 C–H-Activated Cyclization.

Scheme 1

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Results and Discussion

After several unsuccessful attempts using potential combo-catalysts64−71 (entries 1–8, Table 1), we used ZnI2–CuBr (10 mol % each) for the three-component reaction among 2-bromoaniline (1a, 1 mmol), 4-ethynyltoluene (2a, 1 mmol), and paraformaldehyde (3a, 1.2 mmol) in different solvents (entries 9–11, Table 1) to achieve the 4-substituted quinoline 4a at room temperature in 60–65% yield. Gratifyingly, the yield (81%) and the reaction rate (30 min) significantly improved under the solvent-free conditions (entry 12). The combo-catalysis selectively produced 4a. The possible regioisomer 5a was not detected. Catalyst loading was optimized [CuBr (7 mol %)–ZnI2 (9 mol %)] under solvent-free conditions. To understand the role of the counter anion of the combo-catalyst, several experiments were performed with different ZnII–CuI-combinations (entries 13–17) under similar reaction conditions, but the reactions were not efficient. Interestingly, when using a higher and more stable oxidation state of copper in CuBr2, the reaction was unsuccessful (entry 18). We investigated the reaction with the commonly used sp2 C–H activating PdII and RuII as well as several other prospective catalysts (entries 19–25), and the results were not encouraging. Interestingly, MoO(acac)2 was found to be the alternative to ZnI2 (entry 26). However, ZnI2 was our cocatalyst of choice because of its low cost and easy availability. The reaction with the nonmetallic Lewis acid cum oxidant PhIO78−81 was unsuccessful because of the complexation and/or oxidation of the aromatic amine (1a, entry 27). The reaction was completely blocked in an N2 atmosphere, which confirmed the need for aerial oxygen in the construction of quinolines (4a, entry 28). However, the yield did not improve when the reaction was performed in an oxygen atmosphere (entry 29).

Table 1. Survey and Optimization of Cyclization Reactiona.

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entry metal catalystb solventc time (h) 4a, yield (%)d,e
1 AgOTf, TiCl4 CH2Cl2, rt, air 24  
2 V2O5, CeCl3 CH2Cl2, rt, air 24  
3 CeCl3, AgVO3 CH2Cl2, rt, air 24  
4 Yb(OTf)3, MoO(acac)2 CH2Cl2, rt, air 24  
5 RuCl3, Cs2CO3 CH2Cl2, rt, air 24  
6 RuCl3, Ag2CO3 CH2Cl2, rt, air 24  
7 [IrCODCl]2, AgClO4 CH2Cl2, rt, air 24  
8 RhCl3, Cu(OTf)2 CH2Cl2, rt, air 24  
9 ZnI2–CuBr CH2Cl2, rt, air 4.0 62
10 ZnI2–CuBr PhMe, reflux, air 4.0 60
11 ZnI2–CuBr THF, reflux, air 4.0 65
12 ZnI2–CuBrf rt, air 0.5 81
13 Zn(OAc)2–CuBr rt, air 1.5 55
14 ZnCl2–CuBr rt, air 1.0 61
15 ZnI2–CuCl rt, air 1.0 66
16 ZnI2–CuI rt, air 1.0 68
17 ZnI2–CuOTf rt, air 2.5 53
18 ZnI2–CuBr2 rt, air 12  
19 ZnI2–FeSO4 rt, air 12 42
20 ZnI2–AgOTf rt, air 12 31
21 ZnI2–AuCl rt, air 3.0 54
22 ZnI2–PdCl2 rt, air 3.5 45
23 ZnI2–Ru(dppe)Cl2 rt, air 4.0 41
24 ZnI2–PtBr2 rt, air 3.0 48
25 ZnI2–Pd(PPh3)4 rt, air 5.0 23
26 MoO(acac)2–CuBr rt, air 10 60
27 PhIO rt, air 4.0  
28 ZnI2–CuBr rt, N2 24  
29 ZnI2–CuBr rt, O2 0.4 82
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a

1a (1 mmol), 2a (1 mmol), and 3a (1.2 mmol).

b

10 mmol %.

c

10 mL.

d

4a purified by column chromatography.

e

5a not detected.

f

Optimum catalyst loading: ZnI2 (9 mol %)–CuBr (7 mol %).

Tolerance of various functionalities was successfully screened for this new method (Scheme 2) through the synthesis of a large number of valuable 4-substituted quinolines82 bearing both unsubstituted and substituted aromatic residues (Table 2), a heterocycle (4b, entry 2), a biphenyl system (4j, entry 10), and a naphthalene moiety (4k, entry 11). Essentially, there was no limitation regarding the substrate choice because the reactions occurred smoothly to produce their respective quinolines on using aromatic amines bearing halogen (1a–d, entries 1–4 and 9–17), alkyl (1e–g and 1i, entries 5–7 and 18), and alkoxy (1h, entry 8) groups. We initially concentrated on using formaldehyde to derive less substituted quinolines, which found novel applications. Unsubstituted aniline was also effective in the robust cyclization reaction (1j, entry 19). Aryl alkynes bearing alkyl, aryl, methoxy, and thiophenyl (2a–g) groups were tolerated. An aliphatic alkyne also responded well under the developed reaction conditions (2h, entry 12). In general, these simple, mild, and solvent-free products were fully characterized using spectroscopic analyses (Supporting Information). The structure of 4a was confirmed using single crystal X-ray diffraction analyses (Scheme 2),83 and that of 4h was confirmed through a comparison with known spectroscopic data.

Scheme 2. Highly Selective Direct Synthesis of Quinolines.

Scheme 2

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Table 2. Synthesized Quinolines and Reaction Data.

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The widespread bioactivity and pharmaceutical application of the 2,4-disubstituted quinoline derivatives84−89 led us to investigate their synthesis using the simple combo-catalysis strategy. To our delight, the strategy was equally applicable for aldehydes bearing aliphatic (3b, entry 1, Table 3) as well as aromatic (3c–e, entries 2–4) residues to produce 2,4-disubstituted quinolines (4t–w).90 This mild and solvent-free approach was quite fast (2–3 h) and had good yields (63–74%). Moreover, all of the synthesized products were fully characterized using relevant spectroscopic analyses (Supporting Information).

Table 3. List of 2,4-Disubstituted Quinoline Derivativesa.

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a

ZnI2: 9 mol % and CuBr: 7 mol %.

Next, we turned our attention to expanding the scope of the mild tandem cyclization process to achieve valuable sugar-based chiral quinolines. Gratifyingly, the use of glyceraldehydes produced the desired optically pure compound 7a (eq 1, Scheme 3) under the developed reaction conditions (entry 12, Table 1). To understand the versatility of the asymmetric approach, we used different pentose sugar aldehydes (6b,c; eqs 2 and 3), which produced the desired products 7b–d in 1.5–2.0 h in good yield (63–70%). The scope of the mild combo-catalysis was successfully established for the direct synthesis of functionalized chiral quinolines bearing triose, pentose, and hexose sugar moieties (7a–f, eqs 1–4) with a rapid reaction rate (1.5–2.0 h) and good yield (63–72%). The optical purity of the quinolines was verified on a semipreparative chiral HPLC column and by measuring the optical rotation.

Scheme 3. One-Step Synthesis of Sugar-Based Chiral Quinolines.

Scheme 3

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CuBr: 7 mol % and ZnI2: 9 mol %.

Ultraviolet–visible (UV–vis) spectroscopy and X-ray photoelectron spectroscopy (XPS) of the new combo-catalysis process were performed to understand the reaction. A strong absorption band of the reaction mixture (entry 1, Table 2) in dry methanol appeared at 529 nm (λmax) in the UV–vis spectrum (Figure 2), which is very close to the literature value for the [aryl-CuIII–Br]Br complex reported by Ribas, Stahl, and colleagues.91 The XPS spectrum (Figure 3) of the reaction mixture showed the presence of two symbolic peaks at 931.9 and 952.08 eV for CuI and 933.9 and 953.8 eV for transient CuIII.92

Figure 2.

Figure 2

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UV–vis study for the detection of aryl-CuIII-species (529 nm).

Figure 3.

Figure 3

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XPS study for detection of CuI–CuIII species.

To establish the reaction mechanism, we conducted two separate control experiments (4a, entry 1, Table 2) with CuBr and ZnI2, and the reaction did not occur. The cyclization reaction was unsuccessful upon using the imine 2-BrC6H4–N—CH2 and the alkyne 2a under the reaction conditions (entry 12, Table 1), which indicates that the reaction progressed without the formation of an imine intermediate. On the basis of the UV–vis and XPS data, controlled experiments, and literature reports, we propose that CuI first activates the terminal C–H of the alkyne93 to produce R–C≡C–Cu (II, Scheme 4). This observation is also supported by the fact that the reaction was completely blocked upon using internal alkynes. The C–C and C–N bond formation between aldehyde (3), aromatic amine (1), and II with ZnI2 may give rise to propargyl amine intermediate III.16 The intermediate III bearing the flexible C≡C bond allows CuI to easily activate the aromatic C–H and π-bonds for oxidative C–H insertion with C–C coupling94 to aryl-CuIII-based intermediate (IV). The generation of the transient CuIII-species was confirmed using UV–vis (Figure 2), XPS (Figure 3), and electrospray ionization mass spectrometry (ESI-MS) (for IV; e/z 441.8867 [M + H], appearance of multiple peaks due to the presence of the isotopes of the two Br atoms) analyses of the sample taken from the ongoing reaction (4a, entry 1, Table 2). The seven-membered organometallic compound IV immediately transforms into the desired product 4 through the reductive elimination of CuI and aromatization through the formation of the transient intermediate V in the presence of molecular oxygen and CuX.95 The control experiments for the amine–aldehyde–alkyne coupled cyclization (entries 20 and 21; Table 1) were unsuccessful in the absence of air or oxygen. However, the active role of oxygen during the transformation of CuI to reactive CuIII species may not be avoided.

Scheme 4. Combo-Catalysis Cycle.

Scheme 4

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Conclusions

In conclusion, a ZnII/CuI combo-catalyzed, solvent-free rapid general synthesis of quinolines was demonstrated through an uncommonly mild, sp2 C–H-activated tandem cyclization of anilines–aldehydes–alkynes. The scope of this mild strategy was expanded to the direct synthesis of the widely used 2- and 2,4-disubstituted quinolines and also a new class of valuable chiral quinolines bearing sugar moieties directly attached to the chiral center at the C2-position. This method includes a proper example of copper(I)-catalyzed sp2 C–H activation and functionalization with in situ-generated aryl copper(III) species. UV–vis, XPS, ESI-MS, and control experiments were successfully carried out to establish the reaction mechanism involving mild CuI–CuIII switching catalysis. This simple and mild combo-catalysis strategy with efficient sp2 C–H activation at ambient temperature may create another frontier in the modern synthesis of valuable heterocycles and their chiral analogues.

Experimental Section

General Information

All reagents were purchased from commercial suppliers and used without further purification, unless otherwise specified. Commercially supplied ethyl acetate and petroleum ether were distilled before use. The petroleum ether used in our experiments had a boiling range of 60–80 °C. Column chromatography was performed on silica gel (60–120 mesh, 0.12–0.25 mm). Analytical thin-layer chromatography (TLC) was performed on 0.25 mm extra-hard silica gel plates with a UV254 fluorescent indicator. The reported melting points are uncorrected. 1H NMR and 13C NMR spectra were recorded at ambient temperature using 300 MHz spectrometers (300 MHz for 1H and 75 MHz for 13C). Chemical shifts were reported in parts per million from the tetramethylsilane internal reference, and coupling constants were reported in Hertz. Proton multiplicities were represented as s (singlet), d (doublet), dd (double doublet), t (triplet), q (quartet), and m (multiplet). Infrared spectra were recorded on a Fourier transform infrared (FT-IR) spectrometer in thin films. High-resolution mass spectrometry (HR-MS) data were acquired by electron spray ionization on a Q-ToF-microquadrupole mass spectrometer. Optical rotation of the chiral compounds was measured on a polarimeter using a standard 10 cm quartz cell in a sodium-D lamp at ambient temperature. Electronic absorption spectra were recorded using a UV–vis–NIR spectrophotometer. XPS analyses with the reaction mixture were performed on an XPS instrument.

General Procedure for the Synthesis of Quinolines

A mixture of aromatic amine (1, 1 mmol), alkyne (2, 1 mmol), aldehyde (3, 1.25 mmol), and the metal catalysts ZnI2 (9 mol %) and CuBr (7 mol %) together with anhydrous MgSO4 was taken in a mortar and thrashed with a pestle for approximately 25–180 min. The progress of the reaction was monitored using TLC. The reaction mixture was extracted with ethyl acetate (25 mL), and the organic layer was washed successively with a saturated sodium bicarbonate solution (1 × 10 mL) and brine (2 × 10 mL). The organic layer was then dried over anhydrous Na2SO4, filtered, and evaporated in a rotary evaporator under reduced pressure at room temperature. The crude mass was subjected to column chromatography with 5% ethyl acetate–hexane to obtain the corresponding desired product. Thus, the reaction with 2-bromoaniline (1a, 1.0 mmol, 177 mg), 4-ethynyltoluene (2a, 1.0 mmol, 116 mg), and paraformaldehyde (3a, 1.25 mmol, 40 mg) produced 8-bromo-4-p-tolylquinoline (4a) in 81% yield (240 mg, 0.81 mmol) after purification using column chromatography on silica gel (60–120 mesh) with ethyl acetate–petroleum ether (1:25, v/v) as the eluent. The structure of the product (4a) was confirmed using single-crystal X-ray diffractometry. The synthesized quinolines (4a–w) were characterized using NMR (1H and 13C), FT-IR, melting point (solid compounds only), and mass spectral (HR-MS) analyses.

Characterization Data of Substituted Quinolines (4a–w)

8-Bromo-4-p-tolylquinoline (4a)

Yield: 81% (240 mg, 0.81 mmol). Characteristic: yellow solid. Melting point: 97–98 °C. 1H NMR (300 MHz, CDCl3): δ 8.99 (1H, d, J = 4.5 Hz), 7.99 (1H, d, J = 7.5 Hz), 7.87 (1H, d, J = 8.5 Hz), 7.07–7.33 (6H, m), 2.38 (3H, s). 13C NMR (75 MHz, CDCl3): 149.9, 149.3, 144.7, 138.3, 134.0, 132.8, 128.9, 128.8, 127.8, 126.3, 125.6, 124.2, 121.6, 20.7. FT-IR (KBr, cm–1): 1604, 1589, 1575, 1484, 1453, 1398, 1383, 783, 754, 731, 709. HR-MS (m/z) for C16H12BrN (M+): calculated 297.0153, found 297.0155 (one of the major peaks).

Bromo-6-methyl-4-(thiophen-3-yl)quinoline (4b)

Yield: 80% (243 mg, 0.80 mmol). Characteristic: greenish black solid. Melting point: 111–112 °C. 1H NMR (300 MHz, CDCl3): δ 8.86–8.89 (1H, m), 7.84–7.85 (1H, m), 7.69–7.71 (1H, m), 7.42–7.46 (2H, m), 7.31 (1H, t, J = 4.8 Hz), 7.17–7.24 (1H, m), 2.40 (3H, s). 13C NMR (75 MHz, CDCl3): δ 149.7, 144.1, 143.3, 138.1, 137.2, 135.2, 128.8, 128.0, 126.4, 125.1, 124.7, 124.6, 122.0, 21.4. FT-IR (KBr, cm–1): 1609, 1580, 1556, 1474, 1430, 1360, 1019, 831, 686. HR-MS (m/z) for C14H10BrNS (M+): calculated 302.9717, found 302.9713 (one of the major peaks).

6-Bromo-8-methyl-4-phenyl-quinoline (4c)

Yield: 78% (233 mg, 0.78 mmol). Characteristic: grey oil. 1H NMR (300 MHz, CDCl3): δ 8.86–8.89 (1H, m), 7.80–7.83 (1H, m), 7.47–7.52 (1H, m), 7.34–7.45 (5H, m), 7.21–7.24 (1H, m), 2.33 (3H, s). 13C NMR (75 MHz, CDCl3): δ 149.7, 148.4, 144.2, 137.8, 137.1, 135.1, 129.5, 128.6, 128.5, 128.0, 124.8, 122.2, 21.4. FT-IR (neat, cm–1): 1612, 1584, 1570, 1481, 1445, 1431, 1366, 1246, 1032, 863, 763, 701, 620. HR-MS (m/z) for C16H12BrN (M+): calculated 297.0153, found 297.0157 (one of the major peaks).

5,8-Dichloro-4-phenylquinoline (4d)

Yield: 72% (197 mg, 0.72 mmol). Characteristic: yellow oil. 1H NMR (300 MHz, CDCl3): δ 8.96 (1H, d, J = 4.2 Hz), 7.70 (1H, d, J = 8.4 Hz), 7.41 (1H, d, J = 8.4 Hz), 7.31–7.35 (3H, m), 7.20–7.23 (3H, m). 13C NMR (75 MHz, CDCl3): δ 149.8, 149.3, 145.7, 140.1, 133.3, 130.1, 129.9, 129.2, 129.2, 128.8, 128.0, 127.8, 125.7, 118.8. FT-IR (neat, cm–1): 1645, 1603, 1591, 1563, 1480, 1381, 1178, 1027, 832, 810, 783. HR-MS (m/z) for C15H9Cl2N (M+): calculated 273.0112, found 273.0117 (one of the major peaks).

6-Ethyl-4-phenylquinoline (4e)

Yield: 67% (156 mg, 0.67 mmol). Characteristic: brown oil. 1H NMR (300 MHz, CDCl3): δ 8.78 (1H, d, J = 4.5 Hz), 8.01 (1H, d, J = 8.7 Hz), 7.59 (1H, s), 7.47–7.52 (1H, m), 7.40–7.44 (5H, m), 7.19–7.22 (1H, m), 2.67 (2H, q, J = 7.5 Hz), 1.17 (3H, t, J = 7.5 Hz). 13C NMR (75 MHz, CDCl3): δ 149.0, 147.9, 147.4, 142.8, 138.2, 131.6, 130.4, 129.6, 129.5, 128.5, 128.4, 128.3, 126.7, 123.3, 121.3, 29.1, 15.5. FT-IR (neat, cm–1): 1620, 1588, 1561, 1482, 1432, 1379, 1353, 1045, 867, 834, 741, 710. HR-MS (m/z) for C17H15N (M+): calculated 233.1204, found 233.1203.

6-Isopropyl-4-p-tolylquinoline (4f)

Yield: 67% (175 mg, 0.67 mmol). Characteristic: yellow oil. 1H NMR (300 MHz, CDCl3): δ 8.78 (1H, s), 8.03 (1H, d, J = 8.7 Hz), 7.66 (1H, s), 7.54 (1H, dd, J = 8.7, 1.8 Hz), 7.33 (2H, d, J = 7.8 Hz), 7.25 (2H, d, J = 8.1 Hz), 7.16–7.19 (1H, m), 2.88–2.97 (1H, m), 2.38 (3H, s), 1.18 (6H, d, J = 6.6 Hz). 13C NMR (75 MHz, CDCl3): δ 143.4, 142.5, 141.8, 141.5, 132.5, 129.6, 124.0, 123.7, 123.6, 123.1, 121.1, 116.4, 115.7, 28.6, 18.2, 15.6. FT-IR (neat, cm–1): 1614, 1584, 1569, 1501, 1456, 1384, 1042, 859, 817, 755, 698. HR-MS (m/z) for C19H19N (M+): calculated 261.1517, found 262.1594 (M+ + H).

4-(4-Methoxyphenyl)-5,7-dimethylquinoline (4g)

Yield: 80% (210 mg, 0.80 mmol). Characteristic: brown solid. Melting point: 82–83 °C. 1H NMR (300 MHz, CDCl3): δ 8.70 (1H, d, J = 4.5 Hz), 7.75 (1H, s), 7.13 (2H, d, J = 8.7 Hz), 7.05 (2H, d, J = 3.9 Hz), 6.88 (2H, d, J = 8.4 Hz), 3.80 (3H, s), 2.42 (3H, s), 1.94 (3H, s). 13C NMR (75 MHz, CDCl3): δ 159.3, 149.9, 148.7, 148.4, 138.9, 135.3, 134.7, 132.2, 129.8, 127.4, 124.7, 123.0, 113.3, 55.3, 24.4, 21.4. FT-IR (KBr, cm–1): 2970, 1666, 1609, 1571, 1514, 1492, 1457, 1435, 1248, 1032, 832. HR-MS (m/z) for C18H17NO (M+): calculated 263.1310, found 263.1313.

6-Methoxy-4-phenylquinoline (4h)96

Yield: 67% (157 mg, 0.67 mmol). Characteristic: brown oil. 1H NMR (300 MHz, CDCl3): δ 8.80 (1H, d, J = 4.5 Hz), 8.08 (1H, d, J = 9.3 Hz), 7.52 (5H, s), 7.39 (1H, dd, J = 9.3, 2.7 Hz), 7.30 (1H, d, J = 4.2 Hz), 7.19 (1H, d, J = 2.4 Hz), 3.78 (3H, s). 13C NMR (75 MHz, CDCl3): δ 157.9, 147.3, 147.2, 144.5, 138.2, 131.0, 129.2, 128.6, 128.3, 127.7, 121.8, 121.6, 103.7, 55.4. FT-IR (KBr, cm–1): 2925, 1623, 1584, 1501, 1432, 1248, 1030, 856. HR-MS (m/z) for C16H13NO (M+): calculated 235.0997, found 235.0996.

8-Bromo-4-m-tolylquinoline (4i)

Yield: 77% (230 mg, 0.77 mmol). Characteristic: yellow solid. Melting point: 97–98 °C. 1H NMR (300 MHz, CDCl3): δ 8.90 (1H, d, J = 4.5 Hz), 7.90 (1H, d, J = 7.5 Hz), 7.74 (1H, d, J = 8.4 Hz), 7.22–7.28 (2H, m), 7.10–7.20 (4H, m), 2.30 (3H, s). 13C NMR (75 MHz, CDCl3): δ 150.6, 149.4, 145.5, 138.4, 137.4, 133.1, 130.1, 129.4, 128.5, 128.3, 126.8, 126.6, 126.1, 125.1, 122.1, 21.4. HR-MS (m/z) for C16H12BrN (M+): calculated 297.0153, found 297.0152 (one of the major peaks).

4-(Biphenyl-4-yl)-8-bromoquinoline (4j)

Yield: 73% (262 mg, 0.73 mmol). Characteristic: brown solid. Melting point: 130–132 °C. 1H NMR (300 MHz, CDCl3): δ 9.01 (1H, d, J = 4.5 Hz), 8.01 (1H, dd, J = 7.5, 0.9 Hz), 7.90 (1H, dd, J = 8.4, 0.9 Hz), 7.67 (2H, dd, J = 8.1, 1.8 Hz), 7.61 (2H, dd, J = 8.7, 1.5 Hz), 7.26–7.49 (7H, m). 13C NMR (75 MHz, CDCl3): δ 150.6, 148.9, 145.6, 141.6, 140.2, 136.4, 133.2, 130.0, 128.9, 128.2, 127.8, 127.3, 127.1, 126.9, 126.0, 125.2, 122.2. FT-IR (KBr, cm–1): 1639, 1599, 1579, 1494, 1450, 1405, 839, 763, 734, 714, 698. HR-MS (m/z) for C21H14BrN (M+): calculated 359.0310, found 359.0306 (one of the major peaks).

8-Bromo-4-(6-methoxynaphthalen-2-yl)quinoline (4k)

Yield: 72% (261 mg, 0.72 mmol). Characteristic: brown solid. Melting point: 148–149 °C. 1H NMR (300 MHz, CDCl3): δ 9.00 (1H, d, J = 4.2 Hz), 8.01 (1H, dd, J = 7.5, 0.9 Hz), 7.90 (1H, dd, J = 8.4, 0.9 Hz), 7.81–7.83 (2H, m), 7.73 (1H, d, J = 9.0 Hz), 7.49 (1H, d, J = 1.5 Hz), 7.39–7.46 (1H, m), 7.30 (1H, t, J = 7.9 Hz), 7.13–7.17 (2H, m), 3.89 (3H, s). 13C NMR (75 MHz, CDCl3): δ 157.9, 149.9, 149.1, 133.9, 132.7, 131.9, 129.2, 128.0, 127.9, 127.1, 126.6, 126.5, 125.7, 121.9, 119.2, 105.2, 54.9. FT-IR (KBr, cm–1): 1625, 1604, 1580, 1492, 1452, 1384, 1252, 1209, 1026, 853, 819, 768, 747. HR-MS (m/z) for C20H15BrNO (M+ + H): calculated 364.0337, found 364.0334 (M+ + H, one of the major peaks).

8-Bromo-4-(o-tolyloxymethyl)quinoline (4l)

Yield: 65% (212 mg, 0.65 mmol). Characteristic: brown solid. Melting point: 78–79 °C. 1H NMR (300 MHz, CDCl3): δ 8.97 (1H, d, J = 3.6 Hz), 8.00 (1H, d, J = 7.5 Hz), 7.88 (1H, d, J = 8.4 Hz), 7.59 (1H, d, J = 3.3 Hz), 7.35 (1H, t, J = 7.5 Hz), 7.09–7.13 (2H, m), 6.85 (2H, t, J = 8.4 Hz), 5.44 (2H, s), 2.23 (3H, s). 13C NMR (75 MHz, CDCl3): δ 156.2, 151.1, 145.1, 143.2, 133.2, 131.1, 127.2, 127.1, 126.9, 125.8, 122.7, 121.3, 120.0, 111.3, 66.4, 16.3. FT-IR (KBr, cm–1): 1646, 1601, 1587, 1463, 1368, 1306, 1291, 1191, 1020, 754. HR-MS (m/z) for C17H14BrNO (M+): calculated 327.0259, found 327.0261 (one of the major peaks).

8-Bromo-4-phenylquinoline (4m)

Yield: 75% (212 mg, 0.75 mmol). Characteristic: brown oil. 1H NMR (300 MHz, CDCl3): δ 8.97–8.98 (1H, m), 7.98 (1H, dd, J = 7.2, 4.5 Hz), 7.79 (1H, dd, J = 8.1, 1.5 Hz), 7.17–7.46 (7H, m). 13C NMR (75 MHz, CDCl3): 150.5, 149.3, 145.5, 137.5, 133.2, 129.5, 128.6, 128.2, 126.9, 126.0, 125.1, 122.2. FT-IR (neat, cm–1): 1611, 1581, 1490, 1442, 1391, 1372, 779, 751, 731, 702. HR-MS (m/z) for C15H10BrN (M+): calculated 282.9997, found 282.9994 (one of the major peaks).

8-Bromo-4-(4-methoxyphenyl)quinoline (4n)

Yield: 70% (220 mg, 0.70 mmol). Characteristic: brown solid. Melting point: 78–80 °C. 1H NMR (300 MHz, CDCl3): δ 8.94 (1H, dd, J = 4.3, 1.2 Hz), 7.90 (1H, dd, J = 7.5, 1.2 Hz), 7.84 (1H, d, J = 8.4 Hz), 7.24–7.34 (4H, m), 6.96 (2H, dd, J = 9.7, 1.8 Hz), 3.79 (3H, s). 13C NMR (75 MHz, CDCl3): δ 160.0, 150.5, 149.1, 145.5, 133.1, 130.8, 129.7, 128.4, 126.7, 126.0, 125.0, 122.1, 114.1, 55.4. FT-IR (KBr, cm–1): 1666, 1607, 1584, 1513, 1489, 1455, 1386, 1248, 1178, 1037, 837, 766. HR-MS (m/z) for C16H12BrNO (M+): calculated 313.0102, found 313.0104 (one of the major peaks).

8-Bromo-6-methyl-4-phenylquinoline (4o)

Yield: 71% (212 mg, 0.71 mmol). Characteristic: grey oil. 1H NMR (300 MHz, CDCl3): δ 8.86–8.89 (1H, m), 7.80–7.83 (1H, m), 7.47–7.52 (1H, m), 7.34–7.45 (5H, m), 7.21–7.24 (1H, m), 2.33 (3H, s). 13C NMR (75 MHz, CDCl3): δ 149.7, 148.4, 144.2, 137.8, 137.1, 135.1, 129.5, 128.6, 128.5, 128.0, 124.8, 122.2, 21.4. FT-IR (neat, cm–1): 1612, 1584, 1570, 1481, 1445, 1431, 1366, 1246, 1032, 863, 763, 701, 620. HR-MS (m/z) for C16H12BrN (M+): calculated 297.0153, found 297.0157 (one of the major peaks).

8-Bromo-6-methyl-4-m-tolylquinoline (4p)

Yield: 70% (218 mg, 0.70 mmol). Characteristic: yellow solid. Melting point: 126–128 °C. 1H NMR (300 MHz, CDCl3): δ 8.87 (1H, d, J = 4.2 Hz), 7.80 (1H, s), 7.52 (1H, s), 7.30 (1H, t, J = 7.5 Hz), 7.19–7.22 (2H, m), 7.13–7.16 (2H, m), 2.34 (3H, s), 2.32 (3H, s). 13C NMR (75 MHz, CDCl3): δ 149.1, 148.1, 143.6, 137.8, 137.2, 136.5, 134.6, 129.5, 128.7, 127.9, 127.5, 126.1, 124.3, 124.1, 121.7, 20.9. FT-IR (KBr, cm–1): 1610, 1603, 1573, 1482, 1468, 1439, 1376, 1364, 1022, 882, 786, 754, 710. HR-MS (m/z) for C17H15BrN (M+ + H): calculated 312.0388, found 312.0389 (M+ + H, one of the major peaks).

5,8-Dichloro-4-m-tolylquinoline (4q)

Yield: 62% (178 mg, 0.62 mmol). Characteristic: yellow solid. Melting point: 80 °C. 1H NMR (300 MHz, CDCl3): δ 8.93 (1H, dd, J = 3.9, 1.8 Hz), 7.66–7.70 (1H, m), 7.37–7.41 (1H, m), 7.28–7.30 (1H, m), 7.16–7.21 (2H, m), 6.99–7.02 (2H, m), 2.30 (3H, s). 13C NMR (75 MHz, CDCl3): δ 149.8, 149.4, 145.7, 140.0, 137.4, 133.3, 130.1, 129.9, 129.2, 129.1, 128.7, 127.6, 126.0, 125.8, 118.5, 21.4. FT-IR (KBr, cm–1): 1642, 1606, 1589, 1569, 1483, 1383, 1189, 1020, 847, 814, 784. HR-MS (m/z) for C16H11Cl2N (M+): calculated 287.0269, found 287.0271 (one of the major peaks).

8-Methyl-4-phenylquinoline (4r)

Yield: 67% (147 mg, 0.67 mmol). Characteristic: brown oil. 1H NMR (300 MHz, CDCl3): δ 8.85–8.88 (1H, m), 7.65 (1H, d, J = 8.4 Hz), 7.43–7.48 (1H, m), 7.37–7.39 (5H, m), 7.15–7.30 (2H, m), 2.76 (3H, s). 13C NMR (75 MHz, CDCl3): δ 148.6, 147.7, 138.5, 137.3, 129.5, 129.5, 128.4, 128.2, 126.7, 126.2, 123.9, 121.1, 18.6. FT-IR (neat, cm–1): 1602, 1582, 1571, 1477, 1432, 1383, 1364, 1055, 867, 839, 735, 711. HR-MS (m/z) for C16H13NNa (M+ + Na): calculated 242.0946, found 242.0948 (M+ + Na).

4-p-Tolylquinoline (4s)

Yield: 78% (171 mg, 0.78 mmol). Characteristic: blackish oil. 1H NMR (300 MHz, CDCl3): δ 8.87 (1H, d, J = 4.2 Hz), 8.12 (1H, d, J = 8.7 Hz), 7.89 (1H, d, J = 8.4 Hz), 7.66 (1H, t, J = 7.5 Hz), 7.43 (1H, t, J = 7.5 Hz), 7.19–7.36 (5H, m), 2.40 (3H, s). 13C NMR (75 MHz, CDCl3): δ 149.8, 148.7, 148.4, 138.3, 134.9, 129.6, 129.4, 129.3, 129.2, 126.8, 126.5, 125.9, 121.2, 21.2. FT-IR (neat, cm–1): 1614, 1586, 1569, 1501, 1460, 1421, 1390, 1276, 1010, 819, 764. HR-MS (m/z) for C16H13N (M+): calculated 219.1048, found 219.1052.

8-Bromo-2-isobutyl-4-p-tolylquinoline (4t)

Yield: 70% (247 mg, 0.70 mmol). Characteristic: brown oil. 1H NMR (300 MHz, CDCl3): 8.05 (1H, d, J = 8.4 Hz), 7.82 (1H, d, J = 8.1 Hz), 7.60 (1H, t, J = 7.5 Hz), 7.30–7.38 (2H, m), 7.24 (2H, d, J = 7.8 Hz), 7.16 (1H, s), 2.80 (2H, d, J = 7.2 Hz), 2.37 (3H, s), 2.07–2.20 (1H, m), 0.91 (6H, d, J = 6.6 Hz). 13C NMR (75 MHz, CDCl3): δ 161.6, 148.8, 148.0, 138.3, 135.2, 129.4, 129.3, 129.2, 128.9, 125.7, 125.4, 122.2, 48.1, 29.4, 22.6, 21.2. FT-IR (neat, cm–1): 1624, 1590, 1573, 1499, 1456, 1344, 1127, 1053, 855, 817, 760, 711, 698. HR-MS (m/z) for C20H20BrN (M+): calculated 353.0779, found 353.0781 (one of the major peaks).

6-Ethyl-2-(4-nitrophenyl)-4-p-tolylquinoline (4u)

Yield: 66% (243 mg, 0.66 mmol). Characteristic: grey solid. Melting point: 130–132 °C. 1H NMR (300 MHz, CDCl3): δ 8.29 (4H, s), 8.09 (1H, d, J = 8.7 Hz), 7.73 (1H, s), 7.66 (1H, s), 7.58 (1H, d, J = 8.7 Hz), 7.40 (2H, d, J = 7.8 Hz), 7.31 (2H, d, J = 8.1 Hz), 2.72 (2H, q, J = 7.5 Hz), 2.43 (3H, s), 1.21 (3H, t, J = 7.5 Hz). 13C NMR (75 MHz, CDCl3): δ 153.2, 149.2, 148.2, 147.6, 145.6, 143.5, 138.5, 135.2, 131.0, 130.1, 129.3, 128.7, 128.1, 126.2, 123.9, 123.3, 119.0, 21.2, 19.0, 15.4. FT-IR (KBr, cm–1): 2960, 2926, 1725, 1595, 1548, 1516, 1492, 1456, 1343, 1110, 847, 821, 699. HR-MS (m/z) for C24H20N2O2 (M+): calculated 368.1525, found 368.1529.

8-Bromo-2-(2-bromophenyl)-6-methyl-4-phenylquinoline (4v)

Yield: 63% (273 mg, 0.63 mmol). Characteristic: brown oil. 1H NMR (300 MHz, CDCl3): δ 8.85 (1H, s), 8.38 (1H, dd, J = 7.8 Hz), 7.08–8.13 (1H, m), 7.95 (1H, dd, J = 7.2 Hz), 7.74–7.82 (2H, m), 7.60–7.66 (1H, m), 7.47 (1H, s), 7.14–7.25 (2H, m), 7.04 (1H, d, J = 8.1 Hz), 2.35 (3H, s), 2.16 (3H, s). 13C NMR (75 MHz, CDCl3): δ 159.5, 157.5, 147.6, 140.1, 137.9, 137.2, 135.3, 135.2, 133.4, 132.4, 131.3, 130.0, 129.6, 128.6, 128.4, 127.7, 126.8, 125.3, 124.4, 123.9, 122.0, 21.4. FT-IR (neat, cm–1): 1671, 1587, 1539, 1470, 1433, 1356, 827, 756, 702. HR-MS (m/z) for C22H15Br2N (M+): calculated 450.9571, found 450.9574 (one of the major peaks).

8-Bromo-6-methyl-2-(2-nitrophenyl)-4-m-tolylquinoline (4w)

Yield: 74% (319 mg, 0.74 mmol). Characteristic: colorless solid. Melting point: 121–122 °C. 1H NMR (300 MHz, CDCl3): δ 8.85 (1H, s), 8.38 (1H, dd, J = 7.8, 1.2 Hz), 8.08–8.13 (1H, m), 7.95 (1H, dd, J = 7.5, 1.8 Hz), 7.74–7.82 (2H, m), 7.60–7.66 (1H, m), 7.47 (1H, s), 7.14–7.25 (2H, m), 7.04 (1H, d, J = 8.1 Hz), 2.35 (3H, s), 2.16 (3H, s). 13C NMR (75 MHz, CDCl3): δ 156.7, 147.0, 137.9, 134.0, 133.7, 133.6, 133.4, 132.6, 131.3, 131.0, 130.2, 129.6, 129.1, 128.9, 127.5, 124.5, 119.3, 118.6, 115.7, 20.6, 20.0. FT-IR (KBr, cm–1): 1627, 1607, 1571, 1518, 1487, 1337, 1209, 1077, 807, 738. HR-MS (m/z) for C23H17BrN2O2 (M+): calculated 432.0473, found 432.0476 (one of the major peaks).

Characterization Data of Chiral Sugar-Based Quinoline Derivatives (7a–f)

Synthesis of compound 7 was performed according to the procedure for compound 4.

(R)-2-(2,2-Dimethyl-1,3-dioxolan-4-yl)-6-methoxy-4-phenylquinoline (7a)

Yield: 65% (218.0 mg, 0.65 mmol). Characteristic: black oil. [α]D25 – 78.40 (c 0.18, CHCl3). 1H NMR (300 MHz, CDCl3): δ 8.27 (1H, d, J = 9.3 Hz), 7.64 (1H, s), 7.56 (4H, s), 7.46 (1H, d, J = 8.4 Hz), 7.26 (1H, d, J = 1.5 Hz), 7.22 (1H, s), 4.11 (1H, dd, J = 16.0, 7.8 Hz), 3.80 (3H, s), 3.27 (1H, dd, J = 12.0, 3.6 Hz), 3.16 (1H, dd, J = 12.0, 7.2 Hz), 1.58 (3H, s), 1.52 (3H, s). 13C NMR (75 MHz, CDCl3): δ 158.5, 156.5, 152.6, 141.7, 137.6, 129.1, 128.9, 128.8, 128.4, 127.5, 123.3, 121.3, 121.3, 118.7, 110.8, 104.1, 70.5, 67.2, 55.7, 26.8, 26.4. FT-IR (neat, cm–1): 1713, 1627, 1589, 1496, 1378, 1256, 1210, 1163, 1072, 883, 836, 758, 707. HR-MS (m/z) for C21H21NO3 (M+): calculated 335.1521, found 335.1524.

2-((3aR,5R,6R,6aR)-6-(Benzyloxy)-2,2-dimethyltetrahydrofuro[3,2-d][1,3]dioxol-5-yl)-8-bromo-4-p-tolylquinoline (7b)

Yield: 68% (371.5 mg, 0.68 mmol). Characteristic: yellow oil. [α]D25 – 53.70 (c 0.20, CHCl3). 1H NMR (300 MHz, CDCl3): δ 8.05 (1H, d, J = 7.5 Hz), 7.92 (1H, d, J = 8.7 Hz), 7.76 (1H, s), 7.26–7.42 (5H, m), 7.06–7.16 (3H, m), 6.83 (2H, d, J = 7.2 Hz), 6.19 (1H, d, J = 3.0 Hz), 5.72 (1H, d, J = 2.7 Hz), 4.75 (1H, d, J = 12.6 Hz), 4.55–4.58 (1H, m), 4.41 (1H, d, J = 11.7 Hz), 4.19 (1H, d, J = 11.7 Hz), 2.64 (3H, s), 1.61 (3H, s), 1.39 (3H, s). 13C NMR (75 MHz, CDCl3): δ 158.4, 150.0, 149.7, 145.0, 138.8, 134.4, 132.9, 128.9, 128.8, 128.1, 126.4, 125.8, 124.4, 121.4, 117.9, 112.2, 105.6, 84.1, 83.4, 78.5, 72.7, 26.8, 26.4, 21.2. FT-IR (neat, cm–1): 1713, 1631, 1582, 1491, 1451, 1379, 1209, 1084, 1021, 905, 866, 764, 701. HR-MS (m/z) for C30H28BrNO4 (M+): calculated 545.1201, found 545.1204 (one of the major peaks).

2-((3aR,5R,6S,6aR)-6-(Benzyloxy)-2,2-dimethyltetrahydrofuro[3,2-d][1,3]dioxol-5-yl)-8-bromo-4-p-tolylquinoline (7c)

Yield: 63% (344.0 mg, 0.63 mmol). Characteristic: yellow oil. [α]D25 – 62.43 (c 0.19, CHCl3). 1H NMR (300 MHz, CDCl3): δ 8.03 (1H, d, J = 7.2 Hz), 7.91 (1H, d, J = 8.4 Hz), 7.75 (1H, s), 7.25–7.40 (5H, m), 7.03–7.14 (3H, m), 6.82 (2H, d, J = 7.2 Hz), 6.17 (1H, d, J = 3.3 Hz), 5.70 (1H, d, J = 3.0 Hz), 4.72 (1H, d, J = 3.0 Hz), 4.55 (1H, d, J = 3.0 Hz), 4.40 (1H, d, J = 11.7 Hz), 4.17 (1H, d, J = 12.0 Hz), 2.45 (3H, s), 1.60 (3H, s), 1.38 (3H, s). 13C NMR (75 MHz, CDCl3): δ 158.3, 149.9, 149.3, 144.7, 138.3, 134.0, 132.8, 128.9, 128.8, 127.8, 126.3, 125.6, 124.2, 121.4, 117.8, 112.2, 105.7, 84.1, 83.4, 78.3, 72.7, 26.7, 26.4, 21.2. FT-IR (neat, cm–1): 1712, 1623, 1586, 1489, 1455, 1382, 1217, 1078, 1029, 859, 707. HR-MS (m/z) for C30H28BrNO4 (M+): calculated 545.1201, found 545.1206 (one of the major peaks).

2-((3aR,5R,6S,6aR)-6-(Benzyloxy)-2,2-dimethyltetrahydrofuro[3,2-d][1,3]dioxol-5-yl)-5,7-dimethyl-4-phenylquinoline (7d)

Yield: 70% (337.0 mg, 0.70 mmol). Characteristic: yellow oil. [α]D25 – 59.00 (c 0.80, CHCl3). 1H NMR (300 MHz, CDCl3): δ 7.78 (1H, s), 7.50 (1H, s), 7.30–7.40 (5H, m), 7.05–7.15 (4H, m), 6.82 (2H, d, J = 7.2 Hz), 6.13 (1H, d, J = 3.6 Hz), 5.60 (1H, d, J = 3.0 Hz), 4.71 (1H, d, J = 3.6 Hz), 4.43 (1H, d, J = 3.0 Hz), 4.33 (1H, d, J = 11.7 Hz), 4.06 (1H, d, J = 11.7 Hz), 2.50 (3H, s), 1.98 (3H, s), 1.57 (3H, s), 1.32 (3H, s). 13C NMR (75 MHz, CDCl3): δ 155.3, 149.0, 148.7, 142.5, 139.1, 137.3, 135.2, 131.9, 128.8, 128.7, 128.0, 127.2, 126.8, 123.7, 122.0, 112.1, 105.5, 84.0, 83.3, 72.3, 26.9, 26.4, 24.2, 21.3. FT-IR (neat, cm–1): 1714, 1621, 1579, 1488, 1453, 1376, 1211, 1082, 1024, 863, 698. HR-MS (m/z) for C31H31NO4 (M+): calculated 481.2253, found 481.2255.

8-Bromo-4-phenyl-2-((3aR,5R,5aS,8aS,8bR)-2,2,7,7-tetramethyltetrahydro-3aH-bis[1,3]dioxolo[4,5-b:4′,5′-d]pyran-5-yl)quinoline (7e)

Yield: 72% (369.5 mg, 0.72 mmol). Characteristic: brown oil. [α]D25 – 80.63 (c 0.95, CHCl3). 1H NMR (300 MHz, CDCl3): δ 8.00–8.03 (1H, m), 7.83–7.86 (1H, m), 7.73 (1H, d, J = 2.7 Hz), 7.49–7.50 (5H, m), 7.41 (1H, d, J = 8.1 Hz), 7.26–7.27 (1H, m), 5.78 (1H, d, J = 4.8 Hz), 5.28 (1H, s), 5.00 (1H, d, J = 7.8 Hz), 4.81–4.83 (1H, m), 4.46 (1H, dd, J = 2.7, 2.1 Hz), 1.63 (3H, s), 1.50 (3H, s), 1.40 (3H, s), 1.31 (3H, s). 13C NMR (75 MHz, CDCl3): δ 159.2, 148.7, 144.9, 144.8, 138.2, 132.7, 132.4, 129.6, 128.4, 128.3, 127.4, 126.2, 125.7, 120.7, 117.9, 109.4, 108.8, 96.7, 73.6, 71.5, 71.0, 70.9, 26.2, 25.9, 24.9, 24.2. FT-IR (neat, cm–1): 1712, 1634, 1600, 1508, 1453, 1382, 1255, 1211, 1166, 1068, 1003, 905, 764, 702. HR-MS (m/z) for C26H26BrNO5 (M+): calculated 511.0994, found 511.0997 (one of the major peaks).

6-Methoxy-4-phenyl-2-((3aR,5R,5aS,8aS,8bR)-2,2,7,7-tetramethyltetrahydro-3aH-bis[1,3]dioxolo[4,5-b:4′,5′-d]pyran-5-yl)quinoline (7f)

Yield: 67% (310.5 mg, 0.67 mmol). Characteristic: yellow oil. [α]D25 – 56.70 (c 1.2, CHCl3). 1H NMR (300 MHz, CDCl3): δ 8.00 (1H, dd, J = 7.5, 1.5 Hz), 7.59 (1H, d, J = 1.5 Hz), 7.44–7.55 (5H, m), 7.31–7.36 (1H, m), 7.17–7.18 (1H, m), 5.74–5.75 (1H, m), 5.18 (1H, s), 4.84 (1H, dd, J = 6.3, 1.5 Hz), 4.76 (1H, dd, J = 5.7, 2.1 Hz), 4.41–4.44 (1H, m), 3.75 (3H, s), 1.60 (3H, s), 1.41 (3H, s), 1.37 (3H, s), 1.28 (3H, s). 13C NMR (75 MHz, CDCl3): δ 157.5, 155.7, 146.9, 143.7, 138.8, 130.6, 129.3, 128.4, 128.0, 126.9, 121.4, 120.4, 109.1, 108.8, 103.7, 96.7, 73.6, 71.0, 70.7, 55.3, 26.2, 25.9, 24.9, 24.2. FT-IR (neat, cm–1): 1713, 1622, 1593, 1560, 1493, 1381, 1255, 1214, 1166, 1068, 1012, 889, 833, 760. HR-MS (m/z) for C27H29NO6 (M+): calculated 463.1994, found 463.1992.

Acknowledgments

Financial support from DST (SR/S1/OC-05/2012 and SR/S5/GC-04/2012) and UGC (SRF) is gratefully acknowledged.

Supporting Information Available

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.6b00185.

  • Detailed experimental procedures, XRD, spectroscopic data, and spectra (PDF)

  • Crystallographic information (CIF)

The authors declare no competing financial interest.

Supplementary Material

ao6b00185_si_001.pdf (7.5MB, pdf)
ao6b00185_si_002.cif (11.5KB, cif)

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ao6b00185_si_001.pdf (7.5MB, pdf)
ao6b00185_si_002.cif (11.5KB, cif)

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