Efficient C-H activation of alkylbenzenes and methylcyclohexenes to benzyl esters by Pd(OAc)2/Sn(OAc)2 catalyst system

Selective activation of the side-chain C-H bond of alkylbenzenes and methylcyclohexenes is achieved by a Pd(OAc)(2)/Sn(OAc)(2) catalyst system, Under an oxygen atmosphere, various benzyl esters were obtained from the substrates and carboxylic anhydrides. The esters were obtained in more than 100% yield based on the amount of benzoic anhydride, and consumption of oxygen was observed. This suggests that oxygen may be incorporated to produce two moles of the benzoxyl group from one mole of benzoic anhydride, It is interesting that either 1-, 3- or 4-methylcyclohexene reacted with benzoic anhydride to give benzyl benzoate, These carboxylations proceeded at the side-chain alkyl group with high selectivity and no ring-carboxylated product or coupling product was detected, From these results, a mechanism involving the formation of a eta(3)-benzylpalladium complex was proposed. (C) 1997 John Wiley & Sons, Ltd.