Concomitant introduction of COOH and OH groups to biphenyl was achieved by allowing biphenyl to react with CO and O-2 using the Pd/molybdovanadophosphoric acid catalytic system. For instance, biphenyl reacted under a mixed gas of CO (0.5 atm) and O-2, (0.5 atm) in the presence of catalytic amounts of Pd(OAc)(2) and H5PMo10V2O40 center dot 26H(2)O in acetic acid to give the corresponding hydroxybiphenylcarboxylic acids. The reaction was found to proceed through the formation of biphenylcarboxylic acid followed by hydroxylation of the resulting carboxylic acid. (c) 2006 Elsevier B.V. All rights reserved.