Rhodium-Catalyzed and Chiral Zinc Carboxylate-Assisted Allenylation of Benzamides via Kinetic Resolution

Abstract

Enantioenriched allenes are important building blocks. While they have been accessed by other coupling methodologies, enantioenriched allenes have been rarely obtained via C–H activation. In this work, kinetic resolution of tertiary propargyl alcohols as an allenylating reagent has been realized via rhodium(III)-catalyzed C–H allenylation of benzamides. The reaction proceeded efficiently under mild conditions, and both the allenylated products and the propargyl alcohols were obtained in high enantioselectivities with an s-factor of up to 139. The resolution results from bias of the two propargylic substituents and is assisted by a chiral zinc carboxylate additive.