Co/Zn Bimetallic Catalysis Enables Enantioselective Alkynylation of Isatins and α-Ketoesters Using Terminal Alkynes

We present herein a novel cobalt/zinc bimetallic catalysis system for the realization of an efficient and enantioselective alkynylation of isatins and alpha-ketoesters using terminal alkynes. By using a simple procedure with all commercially available catalysts, including cobalt bromide, a chiral bisphosphine ligand, and zinc triflate, a range of synthetically useful tertiary propargylic alcohols are accessed with high yields and good enantioselectivities. Control reactions showed that this catalytic system proceeds through activation of the terminal alkyne by zinc triflate and a base, transmetalation from zinc to cobalt, and then the enantio-determining alkynylation of ketones.