Claisen Condensation

Claisen condensation [′klās·ən känd·ən′sā·shən]

(organic chemistry)

Condensation, in the presence of sodium ethoxide, of esters or of esters and ketones to form β-dicarbonyl compounds.

Condensation of arylaldehydes and acylphenones with esters or ketones in the presence of sodium ethoxide to yield unsaturated esters. Also known as Claisen reaction.

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Claisen Condensation 

a method of obtaining β–ketoesters (or β-aldehyde esters) by the interaction of identical or different esters in the presence of alkaline agents. A typical example of Claisen condensation is the production of acetoacetic ester (ethyl acetoacetate) from ethyl acetate in the presence of alcoholates of sodium, metallic sodium, sodium hydride, or sodium amide:

CH₃COOC₂H₅ + HCH₂COOC₂H₅

→CH₃COCH₂COOC₂H₅ + C₂H₅OH

With the use of esters of formic acid, derivatives of aldehyde acids are formed:

HCOOC₂H₅ + C₆H₅CH₂COOC₂H₅

→C₆H₅CH(COOC₂H₅)CHO + C₂ H₅ OH

The Claisen condensation is also used to obtain other β–carbonyl compounds. Thus, the reaction of esters with nitriles leads to β-ketonitriles; for example,

CH₃COOC₂H₅ + C₆ H₅ CH₂ CN

→CH₃COCH(C₆H₅)CN + C₂H₅OH

β-diketones, such as acetylacetone, are formed with the ketones:

CH₃COOC₂H₅ + CH₃COCH₃

→CH₃COCH₂COCH₃ + C₂ H₅ OH

The Claisen condensation is widely used in industry to obtain various organic compounds, such as acetoacetic ester and acetylacetone and their homologues. The reaction was studied in detail in 1887 by the German chemist L. Claisen.

REFERENCES

Organicheskie reaktsii collection 1. Moscow, 1948. Page 345. (Translated from English.)
Nesmeianov, A. N., and N. A. Nesmeianov. Nachala organicheskoi khimii, book 1. Moscow, 1969. Page 411.

IA. F. KOMISSAROV