Chemo- and regioselective Meerwein-Ponndorf-Verley and Oppenauer reactions catalyzed by Al-free Zr-zeolite beta

Al-free Zr-beta zeolite with Si/Zr up to 75 was synthesized in a fluoride medium. The incorporation of zirconium into zeolite beta induced the formation of increased amounts of polymorph B. Lewis acid sites were predominant in the Al-free Zr-beta. Zr-zeolite beta was found to be an excellent catalyst in the Meerwein-Ponndorf-Verley (MPV) reduction of several alkyl- and aryl-substituted cyclohexanones, with high selectivity to the corresponding alcohols. The catalyst was reusable and no leaching was detected under the reaction conditions. A prominent feature of the Zr-zeolite beta catalyst is its ability to maintain activity even in the presence of rather significant amounts of water, up to 9 wt%. The activity was unaffected by the presence of pyridine but was decreased by added acids. However, the poisoning effect could be easily reversed by washing. The excellent performance of Zr-zeolite beta in the MPVO reaction is due to an appropriate Lewis acidity and the ease of ligand exchange at the Zr active sites within the zeolite beta pore channels. (C) 2004 Elsevier Inc. All rights reserved.