Abstract The efficient homocoupling of arylboronic acids was achieved by using the catalytic combination of inexpensive copper salts and 1, 10-phenanthroline as a ligand. The homocoupling reaction proceeds at ambient temperature in air without any additives such as base or oxidant. This method tolerates various substituents on the arylboronic acids such as halogens, carbonyls, and a nitro group. As a result, 25 symmetrical biaryls were obtained ...