Meerwein-Ponndorf-Verley reduction

The Meerwein-Ponndorf-Verley-Reduction in organic chemistry is the reduction of ketones to secondary alcohols with aluminumisopropylate catalysis in isopropanol solution ^[1].

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First the carbonyl-oxygen coordinates to the aluminumisopropylate 2. This makes the carbonyl-carbon even more positive. In the next step the hydride attacks the carbonyl-carbon and a 6-membered cyclic transition state is formed. After the hydride shift the alcoholate of the desired alcohol 5 and acetone 6 remain. The alcoholate reacts with another isopropanol molecule to form the alcohol 3 and recover the Aluminumisopropylate.

All of these reactions are equilibrium reactions. Distillation of acetone out of the reaction mixture shifts the equilibrium to the product side. This is easily achieved because acetone is the most volatile substance in the reaction mixture.

The same process in the opposite direction is called Oppenauer oxidation.

References

1. ^ Alexander R. Surrey, Name Reactions in Organic Chemistry, 2nd Edition, Academic Press, 1961.