Reaction Steps
Dry dimethylsulfoxide (18.4 mL, 260 mmol) in dry CH2Cl2 (30 mL) was added dropwise to a stirred solution of 2M (COCl)2 (65 mL, 130 mmol) at −78° C. during 15 min under nitrogen. The alcohol 4 (15 g, 104 mmol), prepared according to Example 3, in dry dichloromethane (50 mL) was then added during 10 min. resulting in a slightly cloudy solution, which was stirred for 30 min at −78° C. A solution of triethyl amine (75 mL, 520 mmol) in dichloromethane (50 mL) was then added dropwise during 15 min. The mixture was then stirred for 1h at room temperature, and the reaction was quenched by adding water (25 mL), with rapid stirring. The resulting slurry was immediately poured into ether (300 mL) and washed with 20% KHSO4 (2×200 mL). The layers were separated, and the aqueous layer was extracted with ether (2×100 mL). The combined organic layers were washed with brine solution (2×100 mL), dried over MgSO4, filtered, and concentrated to afford the crude aldehyde 5 (12.4 g, 84%) as an oil, which was used in the following condensation with ethylene glycol, IR (KBr) υmax 2951, 2921, 2863, 1720, 1638, 1456, 1379, 1255, 1121, 1033, 997, 909 cm−1; 1HNMR (CDCl3) δ1.73-1.77 (m, 1 H), 1.92-1.96 (m, 1 H), 2.23-2.27 (m, 1 H), 2.42-2.46 (m, 1 H), 2.50-2.52 (m, 1 H), 3.29 (s, 3 H), 3.39-3.43 (m, 2 H), 5.05-5.10 (m, 2 H), 5.72-5.77 (m, 1 H), 9.64 (s, 1 H); 13CNMR (CDCl3) δ28.65, 33.04, 48.57, 58.57, 70.00, 117.40, 134.85; mass spectrum (EI), m/z (rel intensity) 167 (23), 157 (17), 149 (100), 143 (16), 142 (4, M+), 141 (12), 129 (28), 127 (64), 112 (22), 111 (26), 109 (14), 100 (16), 97 (23), 95 (31), 93 (22), 87 (24), 85 (36), 84 (53), 83 (45), 82 (21), 81 (49), 79 (27), 71 (70), 70 (26), 69 (51), 67 (55), 59 (49), 57 (80), 55 (87), 53 (31).
