4.43 (m, 1H, CHOH), 4.24–3.97 (m, 5H, CHBr, 2 x OCH2), 3.35 (d, J = 6.2, 1H, OH), 2.99–2.74 (m, 3H, 1 x CH2CHOH, CH2CHBr), 2.33–2.19 (m, 1H x CH2CHOH), 1.27, 1.17 (2t, J = 7.0, 6H, 2 x CH3); 13C NMR • 139.9 (d, JC-P = 2.2, ArC), 132.5 (q, JC-F = 33.7, 2 x CCF3), 131.1, 127.7 (ArCH), 122.3 (q, JC-F = 273.5, 2 x CF3), 78.5 (d, JC-P = 5.4, CHOH), 69.2 (d, JC-P = 144.2, CS), 64.8, 64.1 (2d, JC-P = 6.7, 2 x OCH2), 50.9 (d, JC-P = 6.7, CHBr), 37.4 (CH2CHBr), 35.9 (CH2CHOH), 16.1, 15.9 (2d, JC-P = 6.7, 2 x CH3); MS m/z 577 (M+, 0.24), 442 (13), 441 (83), 433 (25), 413 (13), 385 (19), 365 (38), 301(96), 299 (100), 283 (33), 281 (34), 273 (10), 271 (11), 261 (29), 255 (12), 253 (11), 243 (10), 227 (35), 225 (35), 219 (78), 218 (11), 213 (31), 207 (64), 194 (14), 191 (24), 187 (11), 163 (64), 161 (19), 155 (38), 147 (16), 146 (25), 145 (36), 135 (23), 133 (13), 127 (18), 109 (24), 99 (19), 83 (19), 82 (17), 81 (39), 65 (23), 53 (18); HRMS Calcd for C17H20BrNF6O6PS (M+) 575.9806, found: 575.9821.
General procedure for preparation of cyclopentenones 11–14. Method A (Swern oxidation). A mixture of CH2Cl2 (725 •L) and DMSO (246 •L, 3.2 mmol) was added within 5 min to a stirred solution of oxalyl chloride (145 •L, 1.6 mmol) in CH2Cl2 (3.6 mL) at -60 ºC. The reaction mixture was stirred for 15 min and then the alcohol 7 (1.45 mmol) was added within 5 min; stirring was continued for an additional 15 min. TEA (1 mL, 7.2 mmol) was then added, and the reaction mixture was stirred overnight and allowed to warm to room temperature. Water (10 mL) was then added and the aqueous layer was extracted with additional CH2Cl2 (2 x 10 mL). The organic layers were combined, washed with saturated NaCl solution (20 mL), and dried (MgSO4). Solvent evaporation afforded the corresponding crude cyclopentenones, which were purified by flash chromatography (pentane/Et2O).
Method B (TPAP/NMO). TPAP (27 mg, 0.075 mmol) was added to a stirred mixture of alcohol 7ad (273 mg, 0.5 mmol) and NMO (180 mg, 1.5 mmol) in CH2Cl2 (2 mL) at RT. After stirred for 24 h at the same temperature, the reaction mixture was filtered through a pad of Celite, which was washed with Et2O. Solvent evaporation afforded the corresponding crude cyclopentenone, which was purified by flash chromatography (pentane/Et2O).
Method C (IBX). To a solution of corresponding alcohol (0.5 mmol) in THF (3 mL) and DMSO (3 mL, for compound 7ad), or DMSO (6 mL, for 7bd and 7ca), was added IBX20 (418 mg, 1.5 mmol), and the mixture was stirred at RT for 48 h. The mixture was diluted with H2O (4 mL), and stirred at 0 ºC for 10 min. The resulting suspension was filtered through a Celite pad, which was washed with EtOAc. The filtrated was diluted with brine (5 mL), followed by extraction with Et2O (3 x 15 ml) and dried (MgSO4). Solvent evaporation afforded the corresponding crude cyclopentenones, which were purified by flash chromatography (pentane/Et2O).
5-Bromo-3-phenyl-2-cyclopentenone (11). White solid; Rf (pentane/Et2O: 6/1) 0.23; mp 58–60 ºC; IR • 2919, 2850, 1691, 1598, 1441; 1H NMR • 7.65 (d, J = 7.0, 2H, ArH), 7.52–7.46 (m, 3H, ArH), 6.65 (bs, 1H, CH=C), 4.56 (dd, J = 6.8, 2.2, 1H, CHBr), 3.77–3.71 (m, 1H x CH2), 3.36 (dd, J = 18.8, 1.6, 1H x CH2); 13C NMR • 201.9 (CO), 171.0, 169.7 (ArC, CH=C), 132.1, 129.0, 127.0, 124.2 (ArCH, CH=C), 42.1 (CHBr), 40.2 (CH2); MS m/z 238 (M++2, 16), 236 (M+, 17), 158 (14), 157 (100), 130 (38), 128 (62), 127 (24), 102 (20), 64 (11), 51 (12); HRMS Calcd for C11H9BrO (M+) 235.9837, found: 235.9835
5-Bromo-3-(4-nitrophenyl)-2-cyclopentenone (13). White solid; Rf (pentane/Et2O: 2/1) 0.13; mp 158–160 ºC; IR • 2912, 2844, 1719, 1587, 1464; 1H NMR • 8.34, 7.80 (2d, J = 8.9, 2H, ArH), 6.76 (s, 1H, CH=C), 4.56 (dd, J = 6.8, 2.2, 1H, CHBr), 3.82–3.73, 3.41–3.34 (2m, 2H, CH2); 13C NMR • 201.0 (CO), 167.4 (CH=C), 138.7, 127.6 (ArC), 127.8, 124.3 (ArCH, CH=C), 40.2 (CHBr), 29.6
