Meerwein-Ponndorf-Verley reduction
The Meerwein-Ponndorf-Verley reduction is the reduction of aldehydes and ketones to alcohols with aluminum isopropanolate in isopropanol as the solvent . The reaction is an equilibrium reaction , the reverse reaction of which is also known as the Oppenauer oxidation . The reaction takes place under very mild conditions and selectively on carbonyl groups. Easily enolizable aldehydes and ketones, β-ketoesters and β-diketones cannot be reduced with the Meerwein-Ponndorf-Verley reduction. The reaction is named after its discoverers Hans Meerwein , Wolfgang Ponndorf and Albert Verley .
mechanism
The carbonyl compound 2 reacts with aluminum isopropoxide 1 via a cyclic, six-membered transition state 3 . The aluminum acts as a Lewis acid , whereby the complexation of the carbonyl oxygen takes place, which facilitates the hydride transfer necessary for the reduction . With the elimination of acetone 4 , the aluminum alcoholate 5 formed as an intermediate is formed . This reacts with the solvent (isopropanol) 6 to form the aluminum isopropanolate 1 , which thus acts as a catalyst , to form the corresponding alcohol 7 .
The equilibrium of this reaction is shifted to the right side by distilling off the acetone 4 formed . The reverse of the Meerwein-Ponndorf-Verley reduction is the Oppenauer oxidation , which, however, has only little preparative importance.
literature
- Alexander R. Surrey: Name Reactions in Organic Chemistry , 2nd Edition, Academic Press, 1961.
Individual evidence
- ^ László Kürti and Barbara Czakó .: Strategic Applications of Named Reactions in Organic Synthesis: Background and Detailed Mechanisms , Elsevier Academic Press, 2005, ISBN 978-0-12-429785-2 , pp. 280-281.