A REINVESTIGATION OF THE MEERWEIN-PONNDORF-VERLEY REDUCTION - A HIGHLY EFFICIENT VARIATION USING ZIRCONIUM CATALYSTS

A new variation of the Meerwein-Ponndorf-Verley reduction based on mechanistic considerations is presented. Under optimized conditions 1-(4-dimethylaminophenyl)ethanol was used as the reducing alcohol (2-4 equiv.), Zr(O-tBu)(4) as the catalyst (0.2 equiv.) and toluene or cyclohexane as the solvent. Aldehydes and ketones (if not extremely sterically hindered) were reduced to the corresponding alcohols at room temperature mostly within 2-4 h in essentially quantitative yield. alpha,beta-Unsaturated carbonyl compounds cleanly react in a 1,2-mode to afford the corresponding allylic alcohols.