Pd(OAc)2-catalyzed room temperature homocoupling reaction of arylboronic acids under air without ligand

Moderate to good yields of symmetrical biaryls were achieved under very mild conditions via homocoupling of arylboronic acids catalyzed by Pd(OAc)2 under air without using ligand. And the reactions were performed in acetone/water (v/v = 1:1) at room temperature without giving side products. In addition, when the reaction was carried out under an oxygen atmosphere, enhancement of yield was observed which indicated the essential of oxygen.