1. 52 mL) was added Ph 3 P=CHCOCH 3 (576 mg, 1.81 mmol) at room temperature. The mixture was then refluxed for 96 hr. After cooling to room temperature, the mixture was passed through a pad of silica gel and then concentrated in vacuo;The residue was purified with flash column chromatography on silica gel (hexane/EtOAc