Homocoupling of Arylboronic Acids Catalyzed by CuCl in Air at Room Temperature

Homocoupling of arylboronic acids has been successfully carried out by using the inexpensive simple copper salt CuCl as the catalyst in methanol to obtain symmetric biaryls in good to excellent yields. The reaction proceeds with a CuCl loading of 2 mol-% under extremely mild conditions: in air, at room temperature, without the need of any additives such as base, oxidant, or ligand.