Carbon-oxygen bond activation of carboxylic anhydrides by zerovalent palladium complexes and its application to catalytic reactions

Acyclic and cyclic carboxylic anhydrides oxidatively add to zerovalent palladium complexes having tertiary phosphines with carbon-oxygen bond cleavage to give corresponding acyl(carboxylato)palladium complexes, which subsequently react with atmospheric dihydrogen at room temperature to form aldehydes and carboxylic acids. Application of these results led us to the discovery of novel aldehyde synthesis by hydrogenation of carboxylic anhydrides catalyzed by palladium complexes. Furthermore we have developed atom-efficient and environmentally benign, direct hydrogenation of carboxylic acids to corresponding aldehydes in the presence of trimethylacetic anhydride catalyzed by palladium complexes.