Vinylcyclopentenes (3a) and (3b).To vinylcyclopropane 1 (150 mg, 0.68 mmol) and methyl butynoate 2 (1.26 g, 12.9 mmol) in PhH (6 mL) under Ar was added dropwise a deoxygenated solution of Ph2S2 (190 mg, 0.86 mmol) and AIBN (27 mg, 0,17 mmol) in PhH (40 mL) in ca 30 h under sunlamp irradiation. The mixture was kept at r.t. till 1 was consumed (TLC). Evaporation in vacuum
and flash chromatography (silica gel, 5% Et2O in hexane) afforded 96 mg of 3a and 3b in a 1.5:1 ratio (oil, 41%). Chromatography allows isolation of individual stereoisomers.
【Feldman KS, Tet Lett., 1989, 30, 5845】