Fundamental study for development of novel catalytic reactions by transitionmetal complexes involving carbon-oxygen bond cleavage or formation steps

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We have studied the carbon-oxygen bond activation of organic compounds by palladium complexes and its application to novel catalytic processes.Major findings : (A) improvement of the reaction conditions of the diect hydrogenation of carboxylic acids to aldehydes by palladium complexes in the presence of pivalic anhydride was investigated. The hydrogenation reaction proceeded faster in polar solvents such as acetone and DMF. The nature of palladium-tertiary phosphine catalyst also affected the hydrogenation, the highest yield of aldehyde was obtained with use of palladium acetate and five equivalents of tri (p-tolyl) phosphine catalyst. The heterogeneous catalysts such as palladium on charcoal also catalyzed this hydrogenation reaction.(B) carbon-oxygen bond of ketene dimer was cleaved by a zerovalent palladium-styrene complex having two tertiary phosphines to give corresponding palladalactone complex. The structure of the palladalactone complex was fully determined by X-ray crystallography and NMR spectroscopy. Study of the chemical reactivity of the palladalactone complex was also investigated.(C) study on the oxidative carbonylation of amines catalyzed by palladium complexes was investigated. Oxamide was obtained in a good yield by using 1,4-dichloro-2-butene as an oxidizing agent.