Selective Co/Ti cooperatively catalyzed biaryl couplings of aryl halides with aryl metal reagents.

Various aryl bromides or chlorides, including those bearing a free COOH, OH, CONHR, and SO2NHR group, coupled with aryl magnesium or lithium reagents in the presence of 7.5 mol % CoCl2/15 mol % PBu3 and substoichiometric Ti(OEt)4 (40 mol % to ArM) at room temperature in high yields with high chemo- and regioslectivity. This simple reaction represents the first example of Co/Ti cooperative catalysis which plays a key role in suppressing undesired homocouplings.