Copper-catalyzed cyclization/aza-Claisen rearrangement cascade initiated by ketenimine formation: an efficient stereocontrolled synthesis of α-allyl cyclic amidines

Abstract

An efficient and convenient synthesis of α-allyl cyclic amidines has been achieved by applying a novel cascade reaction. Copper(I)-mediated in situ N-sulfonyl ketenimine formation from the reaction of a terminal alkyne with sulfonyl azide is followed by an intramolecular nucleophilic attack on the central carbon atom by an allylic tertiary amine, and then an aza-Claisen rearrangement takes place through a chair transition state to furnish the titled amidines with complete stereocontrol.

Keywords: allylic compounds; copper; cyclization; heterocycles; rearrangements.