Meerwein-Ponndorf-Verley Reduction: Introduction
The Meerwein-Ponndorf-Verley reaction reduces aldehydes and ketones to the corresponding alcohols. The reducing agents are aluminum alkoxides, mainly aluminum isopropoxide. The reaction is a redox reaction. The starting aldehyde or ketone is reduced to an alcohol, and one alkoxide residue of the aluminum alkoxide is oxidized to the ketone. Aluminum isopropoxide can be regenerated by using isopropanol as solvent. The newly generated aluminum alkoxide is hydrolyzed in this equilibrium reaction. By using aluminum isopropoxide, the isopropoxy group is oxidized to acetone which is removed by distillation, thereby moving the equilibrium to the right side.
The reverse reaction is referred to as the Oppenauer oxidation.
Reduction of cinnamyl aldehyde to cinnamyl alcohol (yield 75%).
The reaction is of no preparative importance because reductions of this type are preferrably carried out with complex hydrides. The Meerwein-Ponndorf-Verley reduction is being used in industry to synthesize allyl alcohol from acrolein; the former is an important intermediate in the synthesis of glycerol.