Preparation Of Bicyclic Lactones Using Lewis Acids Catalyzed Ene-Reaction

Abstract

An efficient carbonyl ene-reaction procedure was developed for the preparation of 8-memebered cis-fused bicyclic lactones catalyzed by various Lewis acids at low temperatures. The optimum yield, temperature, catalyst concentration, solvent and reaction time were found to be 82%, -78 ^oC, MgBr.OEt₂ 1.3 equivalent, DCM and 3 hours respectively. A number of different Lewis Acids tested also gave good yields; 78%, -78 ^oC, BF₃.OEt_2, DCM, 24 hours; 74%, -78 ^oC, AlCl₃, DCM, 48 hours