Synthesis of 1,1-diboronate esters by cobalt-catalyzed sequential hydroboration of terminal alkynes

A cobalt complex of iminopyridine-oxazoline catalyzes sequential hydroboration of alkyl and aryl alkynes with pinacolborane to form 1,1-diboronate esters. The reactions proceed under mild conditions with high yields, high regioselectivity, and wide functional group tolerance. The synthetic utility of 1,1-di(boronates) is demonstrated by chemoselective monoarylation and stepwise diarylation through palladium-catalyzed Suzuki-Miyaura coupling reactions.