Cobalt-Catalyzed Diborylation of 1,1-disubstituted Vinylarenes: A Practical Route to Branched gem-Bis(boryl)alkanes.

We report the first catalytic diborylation of 1,1-disubstituted vinylarenes with pinacolborane using a cobalt catalyst generated from bench-stable Co(acac)2 and xantphos. A wide range of 1,1-disubstituted vinylarenes underwent this transformation to produce the corresponding gem-bis(boryl)alkanes in modest to high yields. This cobalt-catalyzed reaction can be readily conducted on a gram scale without the use of a dry box and represents a practical and effective approach to prepare a wide range of branched gem-bis(boryl)alkanes.