Heterogeneous Catalysis in the Meerwein-Ponndorf-Verley Reduction of Carbonyl Compounds

Abstract

The Meerwein-Ponndorf-Verley (MPV) reaction involves the catalysed transfer of hydrogen from an alcohol to a carbonyl compound and provides an effective method for synthesizing carbonyl compounds under very mild conditions. The method, which requires the use of a catalyst, is high selective as it leaves most reducible functional groups in the carbonyl reactant untouched. The classical MPV reaction is conducted in a homogeneous phase, usually in the presence of a metal alkoxide as catalyst. The process has been extensively studied over the past 15 years, using heterogeneous catalysts that minimize or avoid many of the problems inherent in homogeneous catalysis. The most widely used among such catalysts consist of metal oxides (particularly aluminium, magnesium and zirconium oxides), magnesium phosphates, layered double hydroxides, mesoporous solids and zeolitic compounds. These materials vary widely in nature and include acid, basic, neutral, mesoporous and microporous solids. This allows virtually any type of carbonyl compound to be reduced by using an appropriate available catalyst. This paper reviews the most salient advances in MPV reduction processes involving heterogeneous catalysts, with emphasis of the reaction proper rather than on the nature of the catalyst. Special attention is given to the shape selectivity provided by zeolitic materials and layered double hydroxides for some carbonyl compounds.