Rearrangement of cyclopropyl epoxides to 3,6-dihydro-2H-pyrans

Abstract

Aryl-substituted cyclopropyl epoxides rearrange to 3.6-dihydro-2H-pyrans. This new rearrangement is related to that of vinyl epoxides to dihydrofurans but occurs under much milder conditions, probably by way of a homoallyl cation resulting from opening of the epoxide ring by adventitious acid catalysis. It provides a relatively simple procedure for the synthesis of 2-aryl-3,6-dihydro-2H-pyrans.