Mesoporous Zr and Hf catalysts for chemoselective MPV reductions of unsaturated ketones

Zr and Hf catalysts were immobilized in mesoporous materials such as MCM-41 or MCM-48; in comparison with the homogeneous catalysts, the resulting materials display strongly increased activity in the Meerwein-Ponndorf-Verley (MPV) reduction of ketones with alcohols as reductants. In the reduction of unsaturated ketones, a very high selectivity for the allylic alcohol is obtained. For efficient reduction, an excess of the reducing alcohol with respect to the enone is required. For the model reduction of benzalacetone with cyclopentanol, the adsorption of reagents and products on the catalytic material is studied. Even complex substrates such as prostaglandin enone precursors can be reduced; in certain cases a substantial diastereomeric excess is observed. (C) 2003 Elsevier B.V. All rights reserved.