Low-Pressure Cobalt-Catalyzed Enantioselective Hydrovinylation of Vinylarenes

An efficient and practical protocol for the enantioselective cobalt-catalyzed hydrovinylation of vinylarenes with ethylene at low (1.2 bar) pressure has been developed. As precatalysts, stable [L2CoCl2] complexes are employed that are activated in situ with Et2AlCl. A modular chiral TADDOL-derived phosphine-phosphite ligand was identified that allows the conversion of a broad spectrum of substrates, including heterocyclic vinylarenes and vinylferrocene, to smoothly afford the branched products with up to 99% ee and virtually complete regioselectivity. Even polar functional groups, such as OH, NH2, CN, and CO2R, are tolerated.