The Palladium-Catalyzed Cross-Coupling Reaction of Phenylboronic Acid with Haloarenes in the Presence of Bases

Abstract The transition metal-catalyzed reactions of organometallics with organic halides have been extensively studied to prove a new approach to selective formation of carbon-carbon bonds. Recently, such coupling reactions of haloarenes with aryl magnesium1–3 and zinc4 compounds in the presence of palladium or nickel complexes have been reported for the synthesis of biaryls. Davidson and Triggs5 have previously reported that arylboronic acids react with sodium palladate to give the corresponding biaryls in good yields. The synthetic utility of the dimerization reaction is, however, limited because it requires stoichiometric amounts of the palladium compound. On the other hand, we have recently reported that cross-coupling reactions between alkenylboranes and organic halides such as alkenyl,6 alkynyl,6 aryl,7 allyl,8 and benzyl8 halides are effectively catalyzed by a catalytic amount of tetrakis(triphenylphosphine)palladium, Pd(PPh3)4 in the presence of suitable bases as indicated in Scheme 1. Although the detailed mechanistic pathway is not clear at present, the reaction should involve a transmetallation step from alkenylboranes to alkenylpalladiums.