Tishchenko reaction

The Claisen - Tishchenko reaction is named after the chemists Ludwig Claisen (1851-1930) and Vyacheslav Tishchenko Jewgenjewitsch ( 1861-1941 ).

Usually the carboxylic acid esters from carboxylic acids and alcohols can be prepared by acid catalysis. But there is another way: If an aldehyde is available, esters can be prepared as catalyst by the Claisen - Tishchenko reaction in a rearrangement reaction with aluminum alkoxide. In non-enolisable aldehydes may be used instead of an aluminum, a sodium alcoholate. Industrially produced in this way with ethyl acetate from acetaldehyde Aluminiumtriethanolat as catalyst.

If one instead of an aldehyde from a blend emanates more aldehydes, are generally formed complex mixtures of various esters, need to be carefully separated.

Reaction mechanism

The alkoxide binds to two molecules of the aldehyde and forms a cyclic transition state.

The reaction must necessarily take place in water and alcohol -free medium in contrast to the Cannizzaro reaction, the carboxylic acid and alcohol arise from the corresponding aldehyde.

A tandem reaction from an aldol reaction and a Claisen Tishchenko reaction is known as the aldol Tishchenko reaction.

Inner Molecular variant

In the intramolecular Claisen - Tishchenko reaction not enolisierungsfähiger dialdehydes to form lactones.