Catalytic stereoselective synthesis of cyclopentanones from donor–acceptor cyclopropanes and in situ-generated ketenes

Abstract

A dual InBr₃–EtAlCl₂ Lewis acidic system was found to be optimal for promoting the diastereoselective (3 + 2)-cycloaddition of donor–acceptor cyclopropanes with in situ-generated ketenes to form cyclopentanones. The desired products were formed in good to excellent yields (70–93% for 16 examples) and with good to excellent diastereoselectivity and enantiospecificity.