Aerobic Oxidation of Benzene to Biphenyl Using a Pd(II)/Molybdovanadophosphoric Acid Catalytic System

The oxidative coupling reaction of benzene to biphenyl was examined by the use of a Pd(OAc)2/molybdovanadophosphoric acid/O2 system under mild conditions. Pd(OAc)2 combined with two different types of molybdovanadophosphoric acids exhibited the highest catalytic activity for the biphenyl synthesis. The best turn-over number (TON) of Pd(OAc)2 and the yield of biphenyl reached 109 and 14.3% based on the benzene used, respectively. The rate-determining step of the coupling was found to be the reoxidation step of the reduced molybdovanadophosphoric acid by molecular oxygen.