Cyclizations versus rearrangements in the reactions of some epoxyolefins with Lewis acids

Abstract

Treatment of various substituted epoxyolefins A: with BF₃·OEt₂ and other reagents that could be expected to induce carbocyclization to give cyclohexanes was investigated. It turned out that the general reaction of these systems was the epoxide to ketone rearrangement, while the carbocyclization was only a rare event. Only substrates carrying the allylsilane grouping underwent carbocyclization and in addition the protecting groups and the stereochemistry of the system had a decisive influence on whether ring closure or rearrangement were to take place.