Claisen condensation

Source: Wikipedia, the free encyclopedia.
Not to be confused with Claisen rearrangement or Claisen–Schmidt condensation.
Claisen condensation
Named after Rainer Ludwig Claisen
Reaction type Condensation reaction
Reaction
R-COO-R′
+
Carbonyl
+
(Base: Na-OR')
↓
β-keto ester
+
R'-OH
Conditions
Typical solvents
R'-OH
Identifiers
Organic Chemistry Portal claisen-condensation
RSC ontology ID RXNO:0000043

The Claisen

acetoacetic esters.[5]

The overall reaction of the classic Claisen condensation

Requirements

At least one of the

α-proton and be able to undergo deprotonation to form the enolate anion). There are a number of different combinations of enolizable and nonenolizable carbonyl compounds that form a few different types
of Claisen.

The base used must not interfere with the reaction by undergoing

electrophilic
ester.

The alkoxy portion of the ester must be a relatively good

methoxide
and ethoxide, respectively, are commonly used.

Types

  • The classic Claisen condensation, a self-condensation between two molecules of a compound containing an enolizable ester.
  • The mixed (or "crossed") Claisen condensation, where one enolizable ester or ketone and one nonenolizable ester are used.
  • Retro-Claisen condensation is the reverse of the title reaction, i.e., the base-induced cleavage of 2-ketoesters

Mechanism

In the first step of the mechanism, an α-proton is removed by a strong base, resulting in the formation of an enolate anion, which is made relatively stable by the

α-hydrogen
because of the driving force effect of deprotonation of the β-keto ester in the last step.

Animation zum Reaktionsmechanismus der Claisen-Kondensation
animation

See also

References

  1. ISBN 0-07-111562-5
    .
  2. doi:10.1002/cber.188101402192
    .
  3. doi:10.1002/cber.188702001150
    .
  4. ISBN 0471264180
    .
  5. ISBN 3527306730
    .

External links
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