Squaramide–Sulfonamide Organocatalyst for Asymmetric Direct

Apr 10, 2017 - Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AD-H column (hexane/i-PrOH...
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Squaramide−Sulfonamide Organocatalyst for Asymmetric Direct Vinylogous Aldol Reactions Takaaki Sakai, Shin-ichi Hirashima,* Yoshifumi Yamashita, Ryoga Arai, Kosuke Nakashima, Akihiro Yoshida, Yuji Koseki, and Tsuyoshi Miura* Tokyo University of Pharmacy, Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan S Supporting Information *

ABSTRACT: Asymmetric direct vinylogous aldol reactions of furan-2(5H)-one with aldehydes in the presence of a catalytic amount of novel squaramide−sulfonamide organocatalyst resulted in the corresponding addition products with high to excellent enantioselectivities. This is the first successful report illustrating an example of highly stereoselective reactions using a squaramide− sulfonamide organocatalyst.



INTRODUCTION

Organocatalysts involving thiourea motifs as double hydrogen-bond donors are excellent catalysts for various asymmetric reactions to access valuable enantiomerically enriched molecules.6 In addition, squaramide organocatalysts have been reported as good double hydrogen-bond donors; their excellent catalytic activities have been demonstrated. 7 Furthermore, since Wang et al. reported asymmetric conjugate additions of 1,3-diketones to nitroalkenes using the sulfonamide−thiourea organocatalyst, organocatalysts with motif involving multiple hydrogen-bond donors have attracted considerable attention.8 On the other hand, we have reported that β-aminosulfonamides 1 and 2 as a single hydrogen-bond donor are good catalysts for asymmetric direct aldol reactions of ketones with aromatic aldehydes (Figure 1).9 In addition, β-aminosulfonamide organocatalysts were applied to the asymmetric conjugate additions of branched aldehydes to vinylsulfones10 and malonates to enones.11 Among the examined β-aminosulfonamides, organocatalysts with a perfluorobutane sulfonamide group exhibited more effective catalytic activity.9e,10,11 In this context, organocatalysts bearing both squaramide and sulfonamide motifs are expected to have excellent catalytic activity as multiple hydrogen-bond donors. However, to the best of our knowledge, only one report has been published on asymmetric reactions using squaramide− sulfonamide organocatalysts by Du et al.12 Unfortunately, the three squaramide−sulfonamide organocatalysts in the aforementioned study are poor catalysts for the Friedel−Crafts alkylation of indoles with iminochromenes, providing low stereoselectivities. To date, there is no successful example for asymmetric reactions using organocatalysts bearing both

The γ-substituted butenolides are remarkably valuable synthetic intermediates considering that several natural products containing butenolide motif exhibit significant biological activities.1 The chirality of γ-substituted butenolides plays a crucial role in the biological activities of these natural products. To synthesize chiral γ-substituted butenolides, the vinylogous Mukaiyama aldol reactions of activated 2siloxyfuran with aldehydes are one of the most powerful synthetic methodologies, which has been reported by several research groups.2,3 A more convenient synthesis of chiral γsubstituted butenolides is the direct vinylogous aldol reactions between simple furan-2(5H)-one derivatives and aldehydes using organocatalysts; however, they have rarely been reported.4,5 Although the direct vinylogous aldol reactions are highly valuable from the viewpoint of atom economy, the reactions of furan-2(5H)-one with aldehydes reported previously were not highly efficient methodologies.5 Feng et al., in their pioneering work, reported the direct vinylogous aldol reactions using thiourea organocatalyst, which did not result in satisfactory enantioselectivity (Scheme 1, eq 1).5a Pansare et al. reported methods of using squaramide organocatalysts; these methods provided excellent enantioselectivity but required long reaction time and had moderate yields (Scheme 1, eq 2 and 3).5b,c The direct vinylogous aldol reactions using quaternary ammonium organocatalyst were reported by Levacher et al.; however, the method required low temperatures and its yield and enantioselectivity were not satisfactory (Scheme 1, eq 4).5d Therefore, the development of highly efficient asymmetric direct vinylogous aldol reactions still remains one of the most challenging research themes in modern organic chemistry. © 2017 American Chemical Society

Received: February 6, 2017 Published: April 10, 2017 4661

DOI: 10.1021/acs.joc.7b00287 J. Org. Chem. 2017, 82, 4661−4667

Article

The Journal of Organic Chemistry Scheme 1. Previous Reported Methods

Figure 1. Structure of organocatalysts.

Table 1. Catalyst Screening

squaramide and sulfonamide motifs. Herein, we describe highly efficient direct asymmetric vinylogous aldol reactions using organocatalyst with both squaramide and perfluorobutanesulfonamide groups as multiple hydrogen-bond donors.



RESULTS AND DISCUSSION We examined various sulfonamide 2 and squaramide− sulfonamide organocatalysts (3−9) for model vinylogous aldol reactions of furan-2(5H)-one (13) with 4-chlorobenzaldehyde (12a), as summarized in Table 1. The β-aminosulfonamide organocatalyst 2 proved to be a poor catalyst for the direct vinylogous aldol reaction (entry 1). Among the examined squaramide−sulfonamide organocatalysts 3−9, organocatalyst 3 was the most preferable catalyst considering both diastereoselectivity and enantioselectivity (entries 2−8). We demonstrated that the chiral sulfonamide unit of 3 is essential for high stereoselectivity because the use of organocatalyst 1013 without the chiral sulfonamide unit significantly decreased stereoselectivity (entry 9). The use of organocatalyst 11 bearing thiourea motif instead of squaramide also provided lower enantioselectivity (entry 10). The absolute configuration of 14a was determined by comparison with reported chiral-phase HPLC retention times. With this optimized catalyst, various reaction solvents for vinylogous aldol reactions of 12a with 13 using catalyst 3 were studied (Table 2). Among the examined reaction solvents, relatively satisfactory results were obtained when

entry

catalyst

yield (%)a

anti:synb

% eec

1 2 3 4 5 6 7 8 9 10

2 3 4 5 6 7 8 9 10 11

0 49 32 67 65 10 7 53 50 24

88:12 94:6 81:19 87:13 90:10 79:21 80:20 50:50 82:18

91 −79 86 −68 59 −87 92 37 66

a

Isolated yield. bDetermined by 1H NMR analysis of crude product. Enantiomeric excess of anti-14a was determined by chiral HPLC analysis.

c

Et2O or 1,4-dioxane was used (entry 9 and 10). Finally, Et2O was judged to be the most suitable reaction solvent considering both yield and stereoselectivity. Further, optimization of reaction conditions was studied (Table 3). When the amount of 13 (3, 4, and 5 equiv) under diluted conditions (0.2 M) was increased, the use of 5 equiv of 13 afforded the aldol product in high yield with excellent stereoselectivity (entry 5). Under the optimized reaction conditions, the scope and limitation of asymmetric direct vinylogous aldol reactions of 13 with various aldehydes 12b−j were analyzed (Table 4). Aromatic aldehydes bearing electron-withdrawing groups, such 4662

DOI: 10.1021/acs.joc.7b00287 J. Org. Chem. 2017, 82, 4661−4667

Article

The Journal of Organic Chemistry Table 2. Study of Solvents

Table 4. Direct Asymmetric Vinylogous Aldol Reactions Using Organocatalyst 3

entry

solvent

yield (%)a

anti:synb

% eec

1 2 3 4 5 6 7 8 9 10 11 12 13d

CH2CI2 CHCI3 toluene MeOH EtOAc acetone THF CH3CN Et2O 1,4-dioxane MTBE CPME neat

49 52 69 68 76 69 87 49 81 53 81 85 89

88:12 83:17 74:26 83:17 83:17 82:18 84:16 88:12 88:12 92:8 85:15 85:15 80:20

91 89 81 77 85 84 87 88 90 90 88 88 83

a

Isolated yield. bDetermined by 1H NMR analysis of crude product. Enantiomeric excess of anti-14a was determined by chlral HPLC analysis. dThe reaction was carried out for 24 h.

c

Table 3. Study of Reaction Conditions

entry

13 (equiv)

conc. of 12a (M)

yield (%)a

anti:synb

% eec

1 2 3 4 5

2 2 3 4 5

0.4 0.2 0.2 0.2 0.2

81 48 54 80 93

88:12 92:8 95:5 94:6 92:8

90 92 94 94 93

a

Isolated yield. bDetermined by 1H NMR analysis of crude product. Enantiomeric excess of anti-14a was determined by chiral HPLC analysis.

c

as bromo and trifluoromethyl, at the para position reacted with furan-2(5H)-one (13) in the presence of organocatalyst 3 to afford the corresponding anti-products 14b−c in high yields with high enantioselectivities (entries 2−3). The reactions of 2-chlorobenzaldehyde (12d) with 13 resulted in the anti-adducts 14d in high yields with high stereoselectivities (entry 4). The reaction between aldehyde 12e with the methyl group as a moderate electron-donating group and 13 proceeded, resulting in the corresponding product 14e in high yield with excellent enantioselectivity (entry 5). Although 4methoxybenzaldehyde (12f) bearing a strong electrondonating group is a poor substrate and provided moderate yield, high enantioselectivity was obtained (entry 6). Organocatalyst 3 promoted the reactions of aromatic aldehydes without substituent groups, including 12g, 12h, and 12i, to provide adducts 14g−i in high yields with a high degree of enantioselectivity (entries 7−9). Cyclohexanecarbaldehyde (12j), an aliphatic aldehyde, reacted with 13, affording the corresponding product 14j in moderate yield with excellent enantioselectivity (entry 10). The stereochemistry of the products was determined by comparison with reported chiralphase HPLC retention times. Although the transition state for direct vinylogous aldol reactions is unclear, we infer that three

a

Isolated yield. bDetermined by 1H NMR analysis of crude product. Enantiomeric excess of anti-14 was determined by chiral HPLC analysis.

c

acidic protons of squaramide and sulfonamide form multiple hydrogen bonds with aldehydes and the furan-2-ol derived from furan-2(5H)-one and the tertiary amine activates the furan-2-ol to afford high stereoselectivities (Figure 2).



CONCLUSION In brief, the novel organocatalyst 3 bearing the squaramide− sulfonamide motif as a multiple hydrogen-bond donor 4663

DOI: 10.1021/acs.joc.7b00287 J. Org. Chem. 2017, 82, 4661−4667

Article

The Journal of Organic Chemistry

29e (1.30 g, 3.00 mmol) at room temperature. After stirring for 24 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with a 80:1 mixture of CHCl3 and MeOH to give the crude product (1.62 g) as a pale yellow solid. To a solution of the crude product (542 mg, 1.00 mmol) in dry CH2Cl2 (3 mL) was added (R)((1S,2R,4S,5R)-5-ethylquinuclidin-2-yl)(6-methoxyquinolin-4-yl)methanamine14b (326 mg, 1.00 mmol) at room temperature. After stirring for 24 h at room temperature, the reaction mixture was evaporated. MeOH was added to the residue, and the precipitate was collected over grass filter to give the pure 4 (418 mg, 50%) as a white solid; mp 162−163 °C; [α]25D = +11.5° (c 1.00, CHCl3); 1H NMR (400 MHz, CD3OD, 50 °C): δ = 0.94 (t, J = 7.3 Hz, 3H), 1.10−1.19 (m, 1H), 1.36−1.58 (m, 3H), 1.76−1.89 (m, 4H), 2.53− 2.59 (m, 1H), 2.88−2.90 (m, 1H), 3.27−3.35 (br m, 5H), 3.45−3.49 (m, 1H), 3.90 (br s, 1H), 3.95 (s, 3H), 4.29 (br s, 1H), 6.29 (br s, 1H), 6.78−7.00 (m, 5H), 7.50 (dd, J = 9.2, 2.5 Hz, 1H), 7.60−7.67 (m, 1H), 7.72 (s, 1H), 8.03 (d, J = 9.3 Hz, 1H), 8.76 (d, J = 4.7 Hz, 1H); 13C NMR (100 MHz, CDCl3): δ = 11.2, 22.9, 23.6, 24.7, 25.1, 35.1, 40.0, 49.1, 49.5, 49.7, 51.4, 55.9, 61.5, 62.9, 100.0, 108.8−119.0 (complex signals of − CF2 and − CF3), 119.6, 121.9, 123.1, 125.9, 127.3, 127.7, 129.1, 132.0, 137.1, 141.3, 144.7, 147.9, 158.9, 169.9, 170.1, 180.7, 187.2; HRMS (ESI-TOF): calcd for C37H39F9N5O5S [M+H]+: 836.2523, Found: 836.2538. Organocatalyst 5. To a solution of 3,4-dimethoxycyclobut-3-ene1,2-dione (284 mg, 2.00 mmol) in dry MeOH (20 mL) was added (S)-N-(2-Amino-3-methylbutyl)-perfluorobutanesulfonamide10b (769 mg, 2.00 mmol) at room temperature. After stirring for 24 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with a 80:1 mixture of CHCl3 and MeOH to give the crude product (852 mg) as a pale yellow solid. To a solution of the crude product (420 mg, 0.85 mmol) in dry MeOH (5 mL) was added (S)-((1S,2S,4S,5R)-5ethylquinuclidin-2-yl)(6-methoxyquinolin-4-yl)methanamine14a (300 mg, 0.92 mmol) at room temperature. After stirring for 144 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with CHCl3 and MeOH (gradually 1:0−10:1) to give the pure 5 (317 mg, 47%) as a white solid; mp 164−165 °C; [α]27D = −78.8° (c 1.00, CHCl3); 1H NMR (400 MHz, CD3OD, 50 °C): δ = 0.89−0.97 (m, 10H), 1.28−1.33 (m, 1H), 1.46 (br s, 2H), 1.60−1.83 (br m, 5H), 2.65−3.18 (m, 3H), 3.35−3.64 (m, 4H), 4.00 (s, 3H), 4.00 (br s, 1H, overlapping signal), 6.21 (br m, 1H), 7.44 (dd, J = 9.3, 2.5 Hz, 1H), 7.57 (s, 1H), 7.84 (s, 1H), 7.97 (d, J = 9.1 Hz, 1H), 8.73 (d, J = 3.4 Hz, 1H); 13C NMR (100 MHz, CDCl3): δ = 11.3, 18.3, 19.0, 24.3, 24.6, 25.3, 26.7, 29.7, 31.0, 35.6, 41.2, 42.5, 48.9, 51.6, 56.1, 60.0, 64.5, 100.1, 108.3−116.1 (complex signals of − CF2 and − CF3), 118.7, 123.2, 127.5, 132.0, 141.8, 145.0, 148.0, 159.2, 166.8, 170.1, 182.2, 183.5; HRMS (ESI-TOF): calcd for C33H39F9N5O5S [M+H]+:788.2523, Found: 788.2528. Organocatalyst 6. To a solution of 3,4-dimethoxycyclobut-3-ene1,2-dione (284 mg, 2.00 mmol) in dry MeOH (20 mL) was added (S)-N-(2-Amino-3-methylbutyl)-perfluorobutanesulfonamide10b (769 mg, 2.00 mmol) at room temperature. After stirring for 24 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with a 80:1 mixture of CHCl3 and MeOH to give the crude product (852 mg) as a pale yellow solid. To a solution of the crude product (420 mg, 0.85 mmol) in dry MeOH (5 mL) was added (R)-((1S,2R,4S,5R)-5ethylquinuclidin-2-yl)(6-methoxyquinolin-4-yl)methanamine14b (300 mg, 0.92 mmol) at room temperature. After stirring for 144 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with CHCl3 and MeOH (gradually 1:0−10:1) to give the pure 6 (415 mg, 47%) as a white solid; mp 224−225 °C (decomp.); [α]25D = +189.5° (c 1.00, CHCl3); 1H NMR (400 MHz, CD3OD, 50 °C): δ = 0.84− 0.96 (m, 9H), 1.15−1.20 (m, 1H), 1.29−1.59 (m, 3H), 1.72−1.83 (m, 5H), 3.14−3.29 (m, 4H), 3.35−3.43 (m, 2H), 3.74−3.92 (br m, 2H), 4.00 (s, 3H), 6.36 (d, J = 10.8 Hz, 1H), 7.46 (dd, J = 9.2, 2.5 Hz, 1H), 7.06 (d, J = 3.7 Hz, 1H), 7.84 (s, 1H), 7.99 (d, J = 9.1 Hz,

Figure 2. Plausible transition state.

efficiently catalyzed the direct vinylogous aldol reactions of various aldehydes with furan-2(5H)-one to yield the corresponding anti-aldol products with high to excellent enantioselectivities. We first demonstrated that the squaramide−sulfonamide skeleton is an excellent motif for organocatalysis. Further application of squaramide−sulfonamide organocatalysts in the synthesis of bioactive compounds is currently under progress in our laboratory.



EXPERIMENTAL SECTION

1

H NMR and 13C NMR spectra were recorded on a Bruker Avance III Nanobay 400 MHz spectrometer (400 MHz for 1H NMR and 100 MHz for 13C NMR). The chemical shifts are expressed in ppm downfield from tetramethylsilane (δ = 0.00) as an internal standard. Mass spectra were recorded by an electrospray ionization-time-offlight (ESI-TOF) mass spectrometer (Micromass LCT). Specific rotations were measured on a Jasco P-1030. Melting points were obtained with Yanaco MP-J3 and are uncorrected. For thin layer chromatographic (TLC) analyses, Merck precoated TLC plates (silica gel 60 F254) were used. Flash column chromatography was performed on neutral silica gel (Kanto Silica gel 60N, 40−50 μm). Preparation of Organocatalyst 3. To a solution of 3,4dimethoxycyclobut-3-ene-1,2-dione (499 mg, 3.51 mmol) in dry MeOH (35 mL) was added 29e (1.52 g, 3.51 mmol) at room temperature. After stirring for 20 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with a 80:1 mixture of CHCl3 and MeOH to give the crude product (1.96 g) as a pale yellow solid. To a solution of the crude product (1.63 g, 3.00 mmol) in dry MeOH (12 mL) was added (S)-((1S,2S,4S,5R)-5-ethylquinuclidin-2-yl)(6methoxyquinolin-4-yl)methanamine14a (976 mg, 3.00 mmol) at room temperature. After stirring for 31 h at room temperature, the reaction mixture was evaporated. MeOH was added to the residue, and the precipitate was collected over grass filter to give the pure 3 (1.58 g, 63%) as a white powder. mp 156−158 °C; [α]25D = −40.3° (c 1.00, CHCl3); 1H NMR (400 MHz, CD3OD, 50 °C): δ = 0.92 (t, J = 7.3 Hz, 3H), 0.92 (br s, 1H, overlapping signal), 1.48 (s, 2H), 1.82 (br s, 5H), 2.74−3.03 (br m, 4H), 3.26−3.33 (br m, 2H, overlapping signals), 3.39−3.76 (br m, 2H), 3.95 (s, 3H), 3.98−4.24 (br m, 2H), 6.29 (br s, 1H), 7.01 (br s, 5H), 7.47 (dd, J = 9.2, 2.5 Hz, 1H), 7.55 (d, J = 2.9 Hz, 1H), 7.75 (br s, 1H), 8.01 (d, J = 9.1 Hz, 1H), 8.76 (s, 1H); 13C NMR (100 MHz, CDCl3): δ = 11.3, 24.3, 24.7, 25.2, 26.8, 35.0, 39.0, 42.9, 50.9, 51.4, 56.1, 60.2, 60.6, 100.0, 108.3−119.4 (complex signals of − CF2 and − CF3), 118.4, 123.2, 126.2, 127.4, 128.2, 129.3, 132.1, 137.9, 141.4, 145.0, 148.0, 159.2, 166.9, 169.4, 182.1, 183.5; HRMS (ESI-TOF): calcd for C37H39F9N5O5S [M+H]+: 836.2523, Found: 836.2527; Anal. Calcd for C37H38F9N5O5S: C, 53.17; H, 4.58; N, 8.38. Found: C, 52.97; H, 4.76; N, 8.17. Organocatalyst 4. To a solution of 3,4-dimethoxycyclobut-3-ene1,2-dione (426 mg, 3.00 mmol) in dry MeOH (30 mL) was added 4664

DOI: 10.1021/acs.joc.7b00287 J. Org. Chem. 2017, 82, 4661−4667

Article

The Journal of Organic Chemistry 1H), 8.74 (d, J = 4.7 Hz, 1H); 13C NMR (100 MHz, CDCl3): δ = 11.4, 17.7, 19.0, 23.1, 23.9, 25.0, 25.2, 31.9, 35.4, 47.5, 49.0, 49.5, 51.9, 55.9, 61.4, 65.6, 100.5, 108.0−119.1 (complex signals of − CF2 and − CF3), 119.3, 123.1, 127.5, 132.0, 142.8, 144.8, 147.9, 158.7, 169.8, 170.5, 181.6, 187.2; HRMS (ESI-TOF): calcd for C33H39F9N5O5S [M+H]+: 788.2523, Found: 788.2518. Organocatalyst 7. To a solution of 3,4-dimethoxycyclobut-3-ene1,2-dione (499 mg, 3.51 mmol) in dry MeOH (35 mL) was added 29e (1.52 g, 3.51 mmol) at room temperature. After stirring for 20 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with a 80:1 mixture of CHCl3 and MeOH to give the crude product (1.96 g) as a pale yellow solid. To a solution of the crude product (542 mg, 1.00 mmol) in dry MeOH (10 mL) was added (1S,2S)N1,N1-dimethylcyclohexane-1,2-diamine15 (284 mg, 2.00 mmol) at room temperature. After stirring for 40 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with CHCl3 and MeOH (gradually 1:0−14:1) to give the pure 7 (579 mg, 90%) as a white solid; mp 257−260 °C (decomp.); [α]21D = −49.3° (c 0.25, DMSO); 1H NMR (400 MHz, CD3OD, 50 °C): δ = 1.29−1.46 (m, 4H), 1.75−2.12 (m, 4H), 2.49 (br s, 7H), 2.83−2.89 (m, 1H), 2.97− 3.02 (m, 1H), 3.34−3.49 (m, 2H), 4.04−4.23 (br m, 2H), 7.18−7.30 (m, 5H); 13C NMR (100 MHz, DMSO): δ = 22.2, 24.0, 34.5, 48.3, 53.2, 56.2, 66.5, 105.5−118.5 (complex signals of − CF2 and − CF3), 126.3, 128.2, 138.1, 167.5, 182.2; HRMS (ESI-TOF): calcd for C25H30F9N4O4S [M+H]+: 653.1839, Found: 653.1852. Organocatalyst 8. To a solution of 3,4-dimethoxycyclobut-3-ene1,2-dione (499 mg, 3.51 mmol) in dry MeOH (35 mL) was added 29e (1.52 g, 3.51 mmol) at room temperature. After stirring for 20 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with a 80:1 mixture of CHCl3 and MeOH to give the crude product (1.96 g) as a pale yellow solid. To a solution of the crude product (542 mg, 1.00 mmol) in dry MeOH (10 mL) was added (1R,2R)N1,N1-dimethylcyclohexane-1,2-diamine15 (284 mg, 2.00 mmol) at room temperature. After stirring for 24 h at room temperature, the reaction mixture was evaporated. MeOH was added to the residue, and the precipitate was collected over grass filter to give the pure 8 (174 mg, 27%) as a white solid; mp 253−255 °C (decomp.); [α]25D = −69.3° (c 0.20, DMSO); 1H NMR (400 MHz, DMSO): δ = 1.23−1.32 (br m, 5H), 1.65−1.98 (m, 5H), 2.43 (br s, 5H), 2.76− 2.95 (m, 3H), 3.85 (br s, 2H), 4.13−4.24 (m, 1H), 7.17−7.28 (m, 6H), 7.55 (br s, 2H); 13C NMR (100 MHz, DMSO): δ = 21.9, 24.0, 24.1, 34.4, 48.4, 53.1, 56.4, 66.6, 105.8−121.3 (complex signals of − CF2 and − CF3), 126.3, 128.2, 129.4, 138.2, 167.4, 182.1; HRMS (ESI-TOF): calcd for C25H30F9N4O4S [M+H]+: 653.1839, Found: 653.1853. Organocatalyst 9. To a solution of 3,4-dimethoxycyclobut-3-ene1,2-dione (284 mg, 2.00 mmol) in dry MeOH (35 mL) was added N-((1S,2S)-2-amino-1,2-diphenylethyl)-3,5-bis(trifluoromethyl)benzenesulfonamide16 (977 mg, 2.00 mmol) at room temperature. After stirring for 23 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with a 80:1 mixture of CHCl3 and EtOAc to give the crude product (850 mg) as a pale yellow solid. To a solution of the crude product (359 mg, 0.60 mmol) in dry MeOH (4 mL) was added (S)-((1S,2S,4S,5R)-5-ethylquinuclidin-2-yl)(6-methoxyquinolin-4-yl)methanamine14a (195 mg, 0.60 mmol) at room temperature. After stirring for 24 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with CHCl3 and MeOH (gradually 1:0−20:1) to give the pure 9 (299 mg, 56%) as a white solid; mp 290−291 °C (decomp.); [α]25D = 115.3° (c 0.25, DMSO); 1H NMR (400 MHz, DMSO): δ = 0.59 (s, 1H), 0.81 (t, J = 7.0 Hz, 3H), 1.36−1.55 (m, 7H), 2.33−2.57 (m, 2H), 3.10−3.15 (m, 1H), 3.95 (s, 3H), 4.67− 4.71 (m, 1H), 5.31−5.36 (m, 1H), 5.95 (br s, 1H), 6.68−6.79 (m, 5H), 7.08−7.19 (m, 5H), 7.47 (d, J = 9.5 Hz, 1H), 7.65 (d, J = 4.0 Hz, 1H), 7.81 (s, 3H), 7.93−8.18 (m, 4H), 8.83 (s, 1H), 8.98 (s, 1H); 13C NMR (100 MHz, DMSO): δ = 12.0, 25.1, 26.2, 26.9, 28.1,

52.9, 55.8, 57.2, 58.7, 61.3, 62.0, 101.6, 119.3, 121.9, 121.9, 122.4 (q, JC−F = 273 Hz), 125.6, 126.8, 127.3, 127.4, 127.6, 127.6, 127.7, 128.5, 130.6 (q, 2JC−F = 33.8 Hz), 131.6, 135.9, 139.1, 143.6, 144.4, 147.8, 157.8, 166.7, 166.9, 181.7, 182.6; HRMS (ESI-TOF): calcd for C46H44F6N5O5S [M+H]+: 892.2962 Found: 892.2964. Organocatalyst 11. To a solution of 29e (720 mg, 1.67 mmol) and N,N′-dicyclohexylcarbodiimide (344 mg, 1.67 mmol) in dry THF (5 mL) was added carbon disulfide (664 μL, 11.0 mmol) at 0 °C. After stirring for 24 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with a 10:1 mixture of hexane and EtOAc to give the crude product (1.03 g) as a pale yellow solid. To a solution of the crude product (1.03 g, 1.67 mmol) in dry THF (6 mL) was added (S)-((1S,2S,4S,5R)-5-ethylquinuclidin-2-yl)(6-methoxyquinolin-4-yl)methanamine14a (976 mg, 3.00 mmol) at room temperature. After stirring for 94 h at room temperature, the reaction mixture was evaporated. The residue was purified by flash column chromatography on silica gel with CHCl3 and EtOAc (gradually 1:0−50:1) to give the pure 11 (1.14 g, 85%) as a white solid; mp 116−118 °C; [α]27D = −78.7° (c 1.00, CHCl3); 1H NMR (400 MHz, CD3OD, 50 °C): δ = 0.91 (t, J = 7.3 Hz, 3H), 1.03−1.08 (m, 1H), 1.46−1.47 (br m, 2H), 1.85−1.92 (br m, 5H), 2.73 (br s, 2H), 3.13−3.19 (m, 3H), 3.35−3.55 (br m, 3H), 3,96 (s, 3H), 3.96 (br s, 1H, overlapping signal), 6.46 (br s, 1H), 6.97 (br s, 5H), 7.45 (dd, J = 9.2, 2.5 Hz, 1H), 7.49 (d, J = 4.9 Hz, 1H), 7.97 (d, J = 9.3 Hz, 1H), 7.99 (d, J = 2.5 Hz, 1H), 8.68 (d, J = 4.7 Hz, 1H); 13C NMR (100 MHz, CDCl3): δ = 11.3, 24.0, 24.4, 24.8, 26.0, 29.7, 34.8, 39.0, 43.2, 52.6, 55.1, 55.8, 59.5, 60.2, 102.2, 107.9−119.2 (complex signals of − CF2 and − CF3), 120.0, 122.8, 126.8, 127.9, 128.5, 128.8, 131.6, 136.0, 141.6, 144.9, 147.8, 158.6, 181.8; HRMS (ESI-TOF): calcd for C34H39F9N5O3S2 [M+H]+: 800.2345, Found: 800.2356. General Procedure for Asymmetric Direct Vinylogous Aldol Reaction and Characterization Date of the Vinylogous Aldol Reaction Products (14a−j). Furan-2(5H)-one 13 (70 μL, 1.0 mmol) was added to a solution of aldehyde 12 (0.2 mmol) and organocatalyst (0.02 mmol, 10 mol%) in dry Et2O (1.0 mL) at 25 °C. After stirring for indicated time, the reaction mixture was purified by silica gel choromatography with CHCl3 and EtOAc (gradually 1:0−50:3) to afforded the title compound 14. (R)-5-((S)-(4-Chlorophenyl)(hydroxy)methyl)furan-2(5H)-one (14a).3a,5a,b According to the general procedure, 4-chlorobenzaldehyde 12a (28.1 mg, 0.2 mmol) afforded product 14a (41.6 mg, 93%) as a white solid, (anti/syn = 92:8) (93% ee); 1H NMR (400 MHz, CDCl3): δ = 2.46 (d, J = 4.0 Hz, 1H, anti), 2.72 (d, J = 3.2 Hz, 1H, syn), 4.74 (dd, J = 6.8 Hz, 3.2 Hz, 1H, syn), 5.06 (dd, J = 4.3 Hz, 4.0 Hz, 1H, anti), 5.14−5.16 (m, 1H, syn, anti), 6.15 (dd, J = 5.8 Hz, 2.0 Hz, 1H, syn), 6.20 (dd, J = 5.8 Hz, 1.9 Hz, 1H, syn), 7.20 (dd, J = 5.8 Hz, 1.4 Hz, 1H, syn), 7.32−7.41 (m, 5H);13C NMR (100 MHz, CDCl3) anti diastereomer: δ = 72.5, 86.5, 123.4, 127.6, 128.2, 129.0, 134.4, 136.9, 152.9, 173.2, syn diastereomer: δ = 74.6, 86.6, 123.3, 128.2, 134.8, 136.4. Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AD-H column (hexane/i-PrOH = 95:5 at 0.8 mL/min); λ = 254 nm; t major = 40.2 min, t minor = 46.2 min; HRMS (ESI): Calcd for C11H9ClO3Na [M+Na]+: 247.0132, Found: 247.0123. (R)-5-((S)-(4-Bromophenyl)(hydroxy)methyl)furan-2(5H)-one (14b).3a,5a,b According to the general procedure, 4-bromobenzaldehyde 12b (37.0 mg, 0.2 mmol) afforded product 14b (46.8 mg, 87%) as a white solid, (anti/syn = 93:7) (94% ee); 1H NMR (400 MHz, CDCl3): δ = 3.15 (br d, J = 3.0 Hz, 1H, anti), 3.24 (br s, 1H, syn), 4.74 (d, J = 6.6 Hz, 1H, syn), 5.05 (br dd, J = 3.4 Hz, 3.0 Hz, 1H, anti), 5.13−5.15 (m, 1H, syn, anti), 6.11−6.13 (m, 1H, syn), 6.17 (dd, J = 5.8 Hz, 1.9 Hz, 1H, anti), 7.20−7.22 (m, 1H, syn), 7.24− 7.29 (m, 2H, syn, anti), 7.32 (dd, J = 1.5 Hz, 5.8 Hz, 1H, anti) 7.50− 7.55 (m, 2H, syn, anti); 13C NMR (100 MHz, CDCl3) anti diastereomer: δ = 72.5, 86.5, 122.5, 123.5, 127.9, 132.0, 152.8, 173.2, syn diastereomer: δ = 74.7, 86.6, 123.0, 123.3, 128.5, 136.9, 153.1, 172.7. Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AD-H column (hexane/i-PrOH = 95:5 at 0.8 mL/min); λ = 254 nm; t major = 40.2 1

4665

DOI: 10.1021/acs.joc.7b00287 J. Org. Chem. 2017, 82, 4661−4667

Article

The Journal of Organic Chemistry

(R)-5-((S)-Hydroxy(phenyl)methyl)furan-2(5H)-one (14g).3a,5a,b According to the general procedure, benzaldehyde 12g (20.3 μL, 0.2 mmol) afforded product 14g (34.9 mg, 92%) as a white solid, (anti/syn = 87:13) (93% ee); 1H NMR (400 MHz, CDCl3): δ = 2.52 (d, J = 3.6 Hz, 1H, anti), 2.79 (d, J = 2.4 Hz, 1H, syn), 4.70−4.72 (m, 1H, syn), 5.10. (dd, J = 3.6 Hz, 4.0 Hz, 1H, anti), 5.16−5.20 (m, 1H, syn, anti), 6.13 (dd, J = 5.8 Hz, 2.0 Hz, 1H, syn), 6.18 (dd, J = 5.7 Hz, 2.0 Hz, 1H, anti), 7.17 (dd, J = 5.8 Hz, 1.6 Hz, 1H, syn), 7.34−7.44 (m, 6H); 13 C NMR (100 MHz, CDCl 3 ) anti diastereomer: δ = 73.1, 86.8, 123.3, 126.1, 128.6, 128.9, 138.4, 153.0, 173.3, syn diastereomer: δ = 75.7, 87.1, 123.0, 126.8, 129.1, 137.9, 153.4, 172.8. Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AS-H column (hexane/i-PrOH = 90:10 at 1.0 mL/min); λ = 254 nm; t major = 31.2 min, t minor = 75.0. min; HRMS (ESI): Calcd for C11H10O3Na [M+Na]+: 213.0522, Found: 213.0531. (R)-5-((S)-Hydroxy(naphthalen-2-yl)methyl)furan-2(5H)-one (14h).3a,5a,b According to the general procedure, 2-nafthaldehyde 12h (31.2 mg, 0.2 mmol) afforded product 14h (34.9 mg, 73%) as a white solid, (anti/syn = 82:18) (89% ee); 1H NMR (400 MHz, CDCl3): δ = 2.71 (d, J = 3.4 Hz, 1H, anti), 2.95 (d, J = 3.0 Hz, 1H, syn), 4.87 (dd, J = 7.0 Hz, 3.0 Hz, 1H, syn), 5.24−5.29 (m, 2 H), 6.12 (dd, J = 5.8 Hz, 2.0 Hz, 1H, syn), 6.19 (dd, J = 5.8 Hz, 1.5 Hz, 1H, anti), 7.18 (dd, J = 5.8 Hz, 1.5 Hz, 1H, syn), 7.34 (dd, J = 5.8 Hz, 1.3 Hz, 1H, anti), 7.46−7.54 (m, 3H, syn, anti), 7.85−7.90 (m, 4H, syn, anti); 13C NMR (100 MHz, CDCl3) anti diastereomer: δ = 73.3, 86.6, 123.4, 123.6, 125.4, 126.6, 126.7, 127.9, 128.2, 128.8, 133.3, 133.4, 135.7, 152.8, 173.0, syn diastereomer: δ = 76.0, 87.1, 123.2, 124.2, 125.4, 128.2, 128.9, 135.2, 153.2; Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AD-H column (hexane/i-PrOH = 90:10 at 1.0 mL/min); λ = 254 nm; t major = 15.8. min, t minor = 20.5 min; HRMS (ESI): Calcd for C15H12O3Na [M+Na]+: 263.0679, Found: 263.0662. (R)-5-((S)-Hydroxy(naphthalen-1-yl)methyl)furan-2(5H)-one (14i).17b According to the general procedure, 1-nafthaldehyde 12i (μL, 0.2 mmol) afforded product 14i (27.2 μL, 91%) as a white solid, (anti/syn = 88:12) (91% ee); 1H NMR (400 MHz, CDCl3): δ = 2.71 (br d, J = 3.5 Hz, 1H, anti), 3.00−3.01 (m, 1H, syn), 5.37− 5.40 (m, 1H, syn), 5.43−5.44 (m, 1H, anti), 5.99 (br dd, J = 3.5 Hz, 3.2 Hz, 1 H, anti), 6.14 (ddd, J = 5.8 Hz, 2.0 Hz, 0.9 Hz 1H, syn), 6.20 (ddd, J = 5.8 Hz, 2.0 Hz, 0.4 Hz 1H, anti), 6.95 (dd, J = 5.8 Hz, 1.5 Hz, 1H, syn), 7.26 (dd, J = 5.8 Hz, 1.3 Hz, 1H, anti), 7.52− 7.62 (m, 3H, syn, anti), 7.73−7.78 (m, 1H, syn, anti), 7.87−7.94 (m, 2H, syn, anti), 7.97−8.03 (m, 1H, syn, anti); 13C NMR (100 MHz, CDCl3) anti diastereomer: δ = 69.6, 85.7, 122.2, 123.3, 124.1, 125.7, 126.1, 127.0, 129.1, 129.3, 130.0, 133.7, 133.8, 153.0, 173.3, syn diastereomer: δ = 87.7, 122.8, 122.9, 125.3, 125.6, 126.1, 126.8, 129.3, 129.6, 130.5, 133.9, 153.6; Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AD-H column (hexane/i-PrOH = 90:10 at 1.0 mL/min); λ = 254 nm; t major = 13.7. min, t minor = 15.6 min; HRMS (ESI): Calcd for C15H12O3Na [M+Na]+: 263.0679, Found: 263.0681. (R)-5-((S)-Cyclohexyl(hydroxy)methyl)furan-2(5H)-one (14j).3a,5a,b According to the general procedure, cyclohexanecalbaldehyde 12j (24.2 μL, 0.2 mmol) afforded product 14j (19.5 mg, 50%) as a white solid, (anti/syn = 89:11) (94% ee); 1H NMR (400 MHz, CDCl3): δ = 1.06−1.36 (m, 5 H, syn, anti), 1.58−1.83 (m, 6H), 2.19 (br, 1H, anti), 3.45−3.49 (m, 1 H, syn), 3.61 (dd, J = 5.9 Hz, 5.7 Hz, 1H, anti), 5.11 (ddd, J = 5.7 Hz, 1.8 Hz, 1.6 Hz, 1H, anti), 5.18−5.20 (m, 1 H, syn), 6.16−6.17 (m, 1 H, syn), 6.19 (dd, J = 5.8 Hz, 1.8 Hz, 1H, anti), 7.45−7.48 (m, 1 H, syn), 7.60 (dd, J = 5.8 Hz, 1.6 Hz, 1H, anti); 13C NMR (100 MHz, CDCl3) anti diastereomer: δ = 25.8, 26.1, 26.3, 27.9, 29.4, 40.7, 75.7, 83.9, 122.8, 154.5, 173.3, syn diastereomer: δ = 25.9, 26.1, 26.2, 28.6, 29.6, 41.4, 75.8, 84.2, 122.5, 154.8. Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AS-H column (hexane/i-PrOH = 80:20 at 1.0 mL/min); λ = 220 nm; t major = 7.6 min, t minor = 13.0 min; HRMS (ESI): Calcd for C11H16O3Na [M+Na]+: 219.0992, Found: 219.0990.

min, t minor = 46.2 min; HRMS (ESI): Calcd for C11H9BrO3Na [M +Na]+: 290.9627, Found: 290.9630. (R)-5-((S)-Hydroxy(4-(trifluoromethyl)phenyl)methyl)furan-2(5H)one (14c). 3a,5b According to the general procedure, 4(trifluoromethyl)benzaldehyde 12c (26.8 μL, 0.2 mmol) afforded product 14c (50.1 mg, 97%) as a white solid, (anti/syn = 91:9) (91% ee); 1H NMR (400 MHz, CDCl3): δ = 2.76 (d, J = 3.7 Hz, 1 H, anti), 2.91−2.95 (m, 1H, syn), 4.84−4.88 (m, 1H, syn), 5.15−5.20 (m, 2 H), 6.15 (dd, J = 5.8 Hz, 2.0 Hz, 1H, syn), 6.21 (dd, J = 5.8 Hz, 1.8 Hz, 1H, anti), 7.22−7.24 (m, 1H, syn), 7.31 (dd, J = 5.8 Hz, 1.4 Hz, 1H, anti) 7.51−7.56 (m, 2H, syn, anti), 7.65−7.69 (m, 2H, syn, anti); 13C NMR (100 MHz, CDCl3) anti diastereomer: δ = 72.6, 86.4, 123.6, 124.0 (q, 1JC−F = 272 Hz), 125.8 (q, 3JC−F = 3.7 Hz), 126.6, 130.8 (q, 2JC−F = 32.3 Hz), 142.5, 152.6, 173.2, syn diastereomer: δ = 74.6, 86.5, 123.4, 128.1, 152.9. Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AS-H column (hexane/i-PrOH = 90:10 at 1.0 mL/min); λ = 254 nm; t major = 18.6 min, t minor = 29.3 min; HRMS (ESI): Calcd for C12H9F3O3Na [M+Na]+: 281.0396, Found: 281.0404. (R)-5-((S)-(2-Chlorophenyl)(hydroxy)methyl)furan-2(5H)-one (14d).17a According to the general procedure, 2-chlorobenzaldehyde 12d (22.5 μL, 0.2 mmol) afforded product 14d (43.2 mg, 96%) as a white solid, (anti/syn = 88:12) (91% ee); [α]24D = +188.0° (c 1.0, CHCl3); 1H NMR (400 MHz, CDCl3): δ = 2.82 (d, J = 3.7 Hz, 1H), 5.40−5.41 (m, 1H), 5.60 (dd, J = 3.7 Hz, 3.6 Hz, 1H), 6.19 (dd, J = 5.8 Hz, 2.0 Hz, 1H), 7.25 (dd, J = 5.8 Hz, 1.4 Hz, 1H) 7.29−7.41 (m, 3H), 7.56 (dd, J = 7.6 Hz, 1.4 Hz, 1H); 13C NMR (100 MHz, CDCl3): δ = 69.5, 84.8, 123.6, 127.5, 128.0, 129.7, 132.0, 135.6, 152.4, 173.4. Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AD-H column (hexane/i-PrOH = 95:5 at 0.8 mL/min); λ = 254 nm; t major = 19.4 min, t minor = 28.1 min; HRMS (ESI): Calcd for C11H9ClO3Na [M+Na]+: 247.0132, Found: 247.0138. (R)-5-((S)-Hydroxy(p-tolyl)methyl)furan-2(5H)-one (14e).3a,5a,b According to the general procedure, p-tolualdehyde 12e (23.6 μL, 0.2 mmol) afforded product 14e (33.2 mg, 81%) as a white solid, (anti/syn = 88:12) (91% ee); 1H NMR (400 MHz, CDCl3): δ = 2.37 (s, 3H, syn, anti), 2.54 (br d, J = 2.9 Hz, 1H, anti), 2.80 (s, 1H, syn), 4.66 (d, J = 7.0 Hz, 1H, syn), 5.04−5.05 (br, 1H, anti), 5.13−5.17 (m, 1 H, syn, anti), 6.12 (dd, J = 5.8 Hz, 2.0 Hz, 1H, syn), 6.17 (dd, J = 5.8 Hz, 2.0 Hz, 1H, anti), 7.16 (dd, J = 5.8 Hz, 1.5 Hz, 1H, syn), 7.19−7.29 (m, 4H, syn, anti), 7.36 (dd, J = 5.8 Hz, 1.5 Hz, 1H, anti); 13 C NMR (100 MHz, CDCl3) anti diastereomer: δ = 21.3, 73.1, 86.8, 123.2, 126.1, 126.8, 129.5, 135.4, 138.5, 153.1, 173.2, syn diastereomer: δ = 75.6, 87.2, 123.0, 126.8, 134.9, 138.9, 153.4. Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AD-H column (hexane/i-PrOH = 95:5 at 1.0 mL/min); λ = 254 nm; t major = 23.9 min, t minor = 26.6 min; HRMS (ESI): Calcd for C12H12O3Na [M +Na]+: 227.0679, Found: 227.0683. (R)-5-((S)-Hydroxy(4-methoxyphenyl)methyl)furan-2(5H)-one (14f).5a,b According to the general procedure, 4-methoxybenzaldehyde 12f (24.2 μL, 0.2 mmol) afforded product 14f (20.9 mg, 47%) as a white solid, (anti/syn = 88:12) (92% ee); 1H NMR (400 MHz, CDCl3): δ = 2.69 (br d, J = 3.2 Hz, 1H, anti), 2.92 (br s, 1H, syn), 3.82 (s, 3H, syn, anti), 5.65 (d, J = 7.0 Hz, 1H, syn), 5.00 (br dd, J = 3.2 Hz, 2.8 Hz, 1H, anti), 5.13−5.16 (m, 1H, syn, anti), 6.11 (dd, J = 5.8 Hz, 2.0 Hz, 1H, syn), 6.16 (dd, J = 5.8 Hz, 2.0 Hz, 1H, anti), 6.90−6.94 (m, 2H, syn, anti), 7.16 (dd, J = 5.8 Hz, 1.6 Hz, 1H, syn), 7.28−7.33 (m, 2H, syn, anti), 7.38 (dd, J = 5.8 Hz, 1.5 Hz, 1H, anti); 13 C NMR (100 MHz, CDCl3) anti diastereomer: δ = 55.4, 73.0, 86.8, 114.2, 123.2, 127.5, 130.5, 153.2, 159.8, 173.2, syn diastereomer: δ = 75.3, 87.2, 123.0, 128.1, 130.0, 153.4, 160.1, 172.8. Enantiomeric excess of the product was determined by chiral stationary phase HPLC analysis using a ChiralPak AD-H column (hexane/i-PrOH = 90:10 at 1.0 mL/min); λ = 254 nm; t major = 17.5. min, t minor = 20.5 min; HRMS (ESI): Calcd for C12H12O4Na [M +Na]+: 243.0628, Found: 243.0629. 4666

DOI: 10.1021/acs.joc.7b00287 J. Org. Chem. 2017, 82, 4661−4667

Article

The Journal of Organic Chemistry



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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b00287. Spectra data and copies of all new compounds (PDF)



AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] *E-mail: [email protected] ORCID

Tsuyoshi Miura: 0000-0003-1216-4507 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors would like to thank Enago (www.enago.jp) for the English language review. REFERENCES

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DOI: 10.1021/acs.joc.7b00287 J. Org. Chem. 2017, 82, 4661−4667