Base- and Phosphine-Free Palladium-Catalyzed Homocoupling of ­Arylboronic Acid Derivatives under Air

In the presence of a catalytic amount of Pd(OAc)2, ­various arylboronic acids underwent homocoupling in MeOH at ambient temperature under air to give rise to symmetrical biaryls. The homocoupling of arylboronic acids was also carried out using polyurea-encapsulated Pd(OAc)2 as a recyclable catalyst.