A Highly Active Cobalt Catalyst System for Kumada Biaryl Cross-Coupling

A highly active cobalt catalyst system has been developed for the cross-coupling reactions of arylmagnesium reagents and aryl bromides. In the presence of 1 mol% CoCl2, 2 mol% IPr·HCl and 2 mol% NaO t Bu, a wide range of (hetero)biaryls are prepared in 51–99% yields at room temperature within a short reaction time.