SELECTIVE DIMERIZATION OF ALDEHYDES TO ESTERS CATALYZED BY ZIRCONOCENE AND HAFNOCENE COMPLEXES

Zirconocene and hafnocene complexes such as Cp2MH2 and Cp2M(Cl)H (M = Zr or Hf) were found to catalyze efficiently the selective dimerization of aldehydes to esters under mild conditions. Hafnocene complexes exhibited higher activity than the corresponding zirconocene complexes, while titanocene complexes were inert in the present reaction. The reaction was found to be markedly influenced by the structure of the aldehydes used. Cross-dimerization could be achieved by allowing Cp2ZrH2 or Cp2Zr(Cl)H to react with two different aldehydes whose reactivities are slightly different from each other.