Reactions of Alkenyl Fischer Carbene Complexes with Ketene Acetals: Formation of Alkynes

Abstract

Abstract Alkenyl Fischer carbene complexes with an isopropoxy group on the carbene carbon will react with ketene acetals by 1,4‐addition to give a zwitterionic intermediate, which undergoes subsequent internal isopropoxide transfer to generate a vinylidene complex. Either a hydrogen or phenyl group on the vinylidene carbon will undergo a formal 1,2‐migration to give 4‐pentynoate esters after hydrolysis of the intermediate orthoester. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)