A new efficient Pd-catalyzed synthesis of diphenyl carbonate with heteropolyacid as a cocatalyst

A new catalytic system, Pd–Mn-HPA (heteropolyacid), has been found to be very efficient in the oxidative carbonylation of phenol to diphenyl carbonate (DPC) with CO and oxygen at low pressure in the absence of solvent. Synergistic effect between W–Mo–heteropolyacid and Mn(OAc)2 was observed for regenerating the Pd(II) species from Pd(0). The ratio of W–Mo in heteropolyacid, efficiency of the heteropolyacid salts and the roles of tetrabutylammonium bromide and molecular sieves have been investigated in detail. Using suitable components of the catalyst system, 53% yield of DPC with a Pd turnover number of 827 can be attained.