Intermolecular Reaction of Internal Alkynes and Imines: Propargyl Tosylates as Key Partners in a Gold-Catalyzed [4 + 1] Unusual Cyclization Leading to Cyclopent-2-enimines

Propargyl tosylates react with N-tosylaldimines to afford cyclopent-2-enimines in a gold-catalyzed process that involves a deep reorganization of both substrates. The formal [4 + 1] cyclization is initiated by a 1,2-migration of the tosylate that eventually generates a substituted 1,3-diene. Subsequent interaction with the imine launches a series of reaction steps prior to a Nazarov-like cyclization to yield the final product.