Cobalt-Catalyzed Hydroboration of Alkenes, Aldehydes, and Ketones.

An operationally convenient and general method for hydroboration of alkenes, aldehydes, and ketones employing Co(acac) as a precatalyst is reported. The hydroboration of alkenes in the presence of HBpin, PPh, and NaO Bu affords good to excellent yields with high Markovnikov selectivity with up to 97:3 branched/linear selectivity. Moreover, Co(acac) could be used effectively to hydroborate aldehydes and ketones in the absence of additives under mild reaction conditions. Inter- and intramolecular chemoselective reduction of the aldehyde group took place over the ketone functional group.