Supporting Information Wiley-VC 2005 69451 Weinheim, Germany
Stereoselective Lewis Acid-Mediated [1,3] Ring Contraction of 2,5-Dihydrooxepins as a Route to Polysubstituted Cyclopentanes Supplementary Material Christopher G. Nasveschuk and Tomislav Rovis* Department of Chemistry Colorado State University, Fort Collins, C, 80523 E-mail: rovis@lamar.colostate.edu General Methods: All reactions were performed under an inert atmosphere of argon in flame-dried glassware with magnetic stirring. Dichloromethane was degassed with argon and passed through two columns of neutral alumina. Column chromatography was performed on EM Science silica gel 60 (230-400 mesh). Thin layer chromatography was performed on EM Science 0.25 mm silica gel 60-F plates. Visualization was accomplished with UV light, KMn 4, and aqueous ceric ammonium molybdate followed by heating. EtAlCl 2 was purchased as a 1.0M solution in hexane. All Lewis acids used were purchased from Aldrich Chemical Co. and used without further purification. Infrared spectra were obtained on a Nicolet Avatar 320 FT-IR spectrometer. 1 and spectra were recorded on a Varian 400 Mz spectrometer at ambient temperature. Data are reported as follows: chemical shift in parts per million (_, ppm) from an internal standard [deuterated chloroform (CDCl 3 )], multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet), integration, and coupling constant (z). 13 C NMR were recorded on a Varian 100 Mz spectrometer at ambient temperature. Chemical shifts are reported in ppm from (CDCl 3 ) taken as 77.23 ppm. Mass spectra were obtained on Fisons VG Autospec. Analytical high performance liquid chromatography (PLC) was performed on a Dynamax model SD-200 PLC equipped with a Dynamax model UV-1 variable wavelength UV detector using Chiralcel chiral columns as indicated. ptical rotations were measured on an Autopol III automatic polarimeter in a 1 dm cell. General Procedure (A) for the Lewis acid-mediated ring contraction of 2,5- dihydrooxepins. A flame-dried round bottom flask was charged with EtAlCl 2 (1.05 eq.) under an inert atmosphere of argon and subsequently diluted with C 2 Cl 2 (40-70 ml) and mixed for 10 min at ambient temperature. 2,5-Dihydrooxepin in Toluene (typically 0.2 M, 1.0 eq.) was added via syringe in one portion and the reaction was stirred for the indicated time at ambient temperature. The reaction mixture was quenched with 5 ml sat. aq. N 4 Cl, separated and the aqueous layer was extracted with C 2 Cl 2 (2 X 10 ml). The organic layers were combined, dried over Na 2 S 4, filtered, then concentrated in vacuo, and purified via column chromatography. General Procedure (B) for the Lewis acid-mediated ring contraction of 2,5- dihydrooxepins. A flame-dried round bottom flask was charged with EtAlCl 2 (1.05 eq.) under an inert atmosphere of argon and subsequently diluted with 1 ml C 2 Cl 2 and mixed for 10 min at ambient temperature. A separate flame-dried round bottom flask was charged with 2,5-dihydrooxepin (0.2 M in Toluene, 1.0 eq.) and diluted with 1 ml C 2 Cl 2 and transferred over 2 min, via cannula to the Lewis acid solution. The reaction
mixture was quenched with 5 ml sat. aq. N 4 Cl, separated and the aqueous layer was extracted with C 2 Cl 2 (2 X 10 ml). The organic layers were combined, dried over Na 2 S 4, filtered, then concentrated in vacuo, and purified via column chromatography. 2-Methyl-4-phenyl-cyclopent-3-enecarbaldehyde (10). 1 NMR (400 Mz CDCl 3 ) δ 9.83 (1, d, J = 2.5 z), 7.44-7.21 (5, m), 6.05 (1, d, 1.5 z), 3.38 (1, m), 3.28-3.14 (2, m), 2.77 (1, dd, J = 15.6, 7.9 z), 1.08 (3, d, J = 7.0 z); 13 C NMR (100 Mz CDCl 3 ) δ 204.2, 140.2, 135.8, 130.2, 128.6, 127.7, 125.8, 53.4, 42.3, 32.0, 16.5; IR (NaCl dep from C 2 Cl 2 ) 2959, 2726, 1720, 1494, 1447, 756, 693 cm -1 ; RMS (FAB+) calcd for C 13 14, 186.1045. Found 186.1041. 2-Methyl-4-p-tolyl-cyclopent-3-enecarbaldehyde (12). 1 NMR (400 Mz CDCl 3 ) δ 9.81 (1, d, J = 2.6 z), 7.30-7.08 (4, m), 5.99 (1, d, J = 1.9 z), 3.72 (1, m), 3.24-3.11 (2, m), 2.76 (1, dd, J = 15.8, 8.1 z), 2.32 (3, s), 1.08 (3, d, J = 7.2 z); 13 C NMR (100 Mz CDCl 3 ) δ 211.1, 203.6, 139.4, 136.8, 128.6, 128.5, 125.0, 52.7, 41.6, 31.4, 20.7, 15.8; IR (NaCl dep from C 2 Cl 2 ) 2922, 2362, 1720, 1645, 1513, 809 cm -1 ; RMS (FAB+) calcd for C 14 16, 200.1201. Found 200.1198. 2-Methyl-4-(4-trifluoromethyl-phenyl)-cyclopent-3- enecarbaldehyde (14). 1 NMR (400 Mz CDCl 3 ) δ 9.86 (1, d, J = 2.4 z), 7.60-7.48 (4, m), 6.17 (1, d, CF 3 J = 1.9 z), 3.44 (1, m), 3.34-3.18 (2, m), 2.78 (1, dd, J = 17.0, 9.6 z), 1.13 (3, d, J = 7.3 z); 13 C NMR (100 Mz CDCl 3 ) δ 203.6, 139.3, 132.7, 126.0, 125.6, 125.5, 53.2, 42.4, 31.9, 16.4; IR (NaCl dep from C 2 Cl 2 ) 2962, 1721, 1615, 1326, 1123, 827 cm -1 ; RMS (FAB+) calcd for C 14 13 F 3, 254.0929. Found 254.0919. 2,3-Dimethyl-4-phenyl-cyclopent-3-enecarbaldehyde (16). 1 NMR (400 Mz CDCl 3 ) δ 9.81 (1, d, J = 2.3 z), 7.36-7.19 (5, m), 3.18-3.06 (3, m), 2.76 (1, m), 1.81 (3, s), 1.11 (3, d, 6.8 z); 13 C NMR (100 Mz CDCl 3 ) δ 204.8, 138.1, 137.8, 133.3, 128.4, 127.9, 126.8, 52.9, 47.0, 35.1, 14.7, 13.6; IR (NaCl dep from C 2 Cl 2 ) 2961, 2722, 1720, 1446, 762, 700 cm -1 ; RMS (FAB+) calcd for C 14 16, 200.1201. Found 200.1199. 2-enethyl-4-phenyl-cyclopent-3-enecarbaldehyde (18). 1 NMR (400 Mz CDCl 3 ) δ 9.82 (1, d, J = 3.2 z), 7.46-7.14 (10, m), 6.21 (1, d, J = 1.9 z), 3.35-3.21 (2, m), 3.14 (1, m), 2.84 (1, dd, J = 16.1, 8.0 z), 2.75-2.61 (2, m), 1.92-1.68 (2, m); 13 C NMR (100 Mz CDCl 3 ) δ 203.9, 141.8, 141.3, 135.8, 128.7, 128.7, 128.6, 128.1, 127.9, 126.2, 125.9, 53.4, 47.7, 34.4, 33.5, 32.8; IR (NaCl dep from C 2 Cl 2 ) 2920, 2852, 1718, 1494, 695 cm -1 ; RMS (FAB+) calcd for C 20 20, 276.1514. Found 276.1508.
2-[2-(tert-Butyl-diphenyl-silanyloxy)-ethyl]-4-phenylcyclopent-3-enecarbaldehyde (20). 1 NMR (400 Mz CDCl 3 ) δ 9.76 (1, d, J = 3.0 z), 7.68-7.65 (5, m), 7.42- TBDPS 7.23 (10, m), 6.10 (1, s), 3.80-3.73 (2, m), 3.49 (1, m), 3.23 (1, m), 3.10 (1, m), 2.81 (1, dd, J = 16.2, 8.5 z), 1.86 (1, m), 1.59 (1, m), 1.07 (9, s); 13 C NMR (100 Mz CDCl 3 ) δ 204.0, 140.9, 135.8, 133.9, 129.9, 128.6, 128.4, 127.9, 127.7, 125.8, 62.5, 53.3, 44.7, 34.0, 32.5, 27.1, 19.4; IR (NaCl dep from C 2 Cl 2 ) 3070, 2930, 2856, 1721, 1428, 1112, 701 cm -1 ; RMS (FAB+) calcd for C 30 34 2 Si, 454.2328. Found 454.2308. 2,3-Dimethyl-4-phenethyl-cyclopent-3-enecarbaldehyde (22). 1 NMR (400 Mz CDCl 3 ) δ 9.71 (1, d, J = 3.0 z), 7.28-7.17 (5, m), 3.03-2.88 (2, m), 2.76-2.62 (3, m), 2.44-2.29 (3, m), Me 1.42 (3, s), 0.95 (3, d, J = 7.0 z); 13 C NMR (100 Mz CDCl 3 ) δ 205.3, 142.1, 135.8, 132.6, 128.6, 128.4, 126.0, 52.9, 46.0, 34.3, 33.9, 30.5, 14.9, 11.7; IR (NaCl dep from C 2 Cl 2 ) 3026, 2928, Me 2854, 1721, 1453, 699 cm -1 ; RMS (FAB+) calcd for C 16 21, 229.1592. Found 229.1598. 2-Methyl-4-p-tolyl-cyclopent-3-enecarbaldehyde (23). 1 NMR (400 Mz CDCl 3 ) δ 9.76 (1, d, J = 2.4 z), 7.35-7.12 (4, m), 5.97 (1, d, J = 1.9 z), 3.23 (1, m), 3.08-2.92 (2, m), 2.78 (1, m), 2.34 (3, s), 1.24 (3, d, J = 7.0 z); 13 C NMR (100 Mz CDCl 3 ) δ 203.1, 139.7, 137.5, 132.9, 129.3, 128.8, 125.7, 58.2, 41.8, 33.1, 21.4, 20.8; IR (NaCl dep from C 2 Cl 2 ) 2957, 2867, 2712, 1723, 1513, 809 cm -1 ; RMS (FAB+) calcd for C 14 16, 200.1201. Found 200.1204. 2-enethyl-4-phenyl-cyclopent-3-enecarbaldehyde (24). 1 NMR (400 Mz CDCl 3 ) δ 9.73 (1, d, J = 2.1 z), 7.45-7.18 (10, m), 6.11 (1, d, J = 1.7 z), 3.20 (1, m), 3.11-2.89 (3, m), 2.74 (2, t, J = 8.0 z), 1.97-1.82 (2, m); 13 C NMR (100 Mz CDCl 3 ) δ 202.8, 141.9, 140.7, 135.6, 128.7, 128.6, 127.8, 127.7, 126.2, 125.9, 56.0, 46.8, 37.5, 34.1, 33.0; IR (NaCl dep from C 2 Cl 2 ) 3026, 2921, 2712, 1721, 1447, 695 cm -1 ; RMS (FAB+) calcd for C 20 20, 276.1514. Found 276.1502. 2,5-Dimethyl-3-phenyl-cyclopent-3-enecarbaldehyde (26). 1 NMR (400 Mz CDCl 3 ) δ 9.82 (1, d, J = 3.2 z), 7.42-7.23 (5, m), 5.89 (1, s), 3.63 (1, m), 3.38 (1, m), 2.79 (1, ddd, J = 8.3, 4.7, 3.4 z), 1.15 (3, d, J = 6.8 z), 1.12 (3, d, J = 7.5 z); 13 C NMR (100 Mz CDCl 3 ) δ 204.3, 145.9, 135.6, 130.5, 128.7, 127.6, 126.5, 62.4, 40.5, 39.4, 18.8, 16.5; IR (NaCl dep from C 2 Cl 2 ) 3031, 2960, 2928, 1720, 1457, 761, 697 cm -1 ; RMS (FAB+) calcd for C 14 16, 200.1201. Found 200.1202; 23 [α] D = -13.7 o (c = 0.075 in C 2 Cl 2 ); PLC analysis (Chiracel D-, 95:5 hex/i-pr,
1.0 ml/min, 254 nm; tr(minor) = 5.9 min., tr(major) = 12.7 min.) gave the isomeric composition of the product: 95% ee. 4-ydroxymethyl-3-methyl-1-phenyl-cyclopentane-1,2-diol (29). 1 NMR (400 Mz CDCl 3 ) δ 7.55-7.23 (5, m), 3.98 (1, d, J = 8.7 z), 3.72 (2, m), 2.40 (2, m), 2.30 (1, dd, J = 14.5, 8.7 z), 2.00 (1, dd, J = 14.4, 6.5 z), 2.16-1.82 (3, m), 1.18 (3, d, J = 6.6 z); 13 C NMR (100 Mz CDCl 3 ) δ 145.3, 128.5, 127.2, 125.5, 85.6, 80.9, 64.1, 41.8, 39.8, 38.2, 13.3; IR (NaCl dep from C 2 Cl 2 ) 3367, 2959, 2928, 1446, 1337, 1034, 760, 700 cm -1 ; LRMS (ES-) for C 13 17 3, 221.1. Stereochemical assignment for 26: ne enhancements: 1.8% 0.4% 1.3% 26 0.8% 0.9%