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Malonic ester synthesis



The malonic ester synthesis is a chemical reaction where diethyl malonate or another ester of malonic acid is alkylated at the carbon alpha (directly adjacent) to both carbonyl groups, and then converted to a substituted acetic acid.[1]

Additional recommended knowledge

Contents

Mechanism

A strong base is required to deprotonate the center proton. The protons alpha to carbonyl groups are easily deprotonated. The malonic ester is especially so by virtue of being adjacent to two carbonyl groups. The carbanion formed can undergo nucleophilic substitution on the alkyl halide, to give the alkylated compound. On heating, the di-ester undergoes thermal decarboxylation, yielding an acetic acid substituted by the appropriate R group.[2] Thus, the malonic ester can be thought of being equivalent to the -CH2COOH synthon.

The esters chosen are usually the same as the base used, i.e. ethyl esters with sodium ethoxide. This is to prevent scrambling by transesterification.

Variations

Dialkylation

The ester may be dialkylated if deprotonation and alkylation are repeated before the addition of aqueous acid.

Cycloalkylcarboxylic acid synthesis

Intramolecular malonic ester synthesis occurs when reacted with a dihalide.[3]

See also

References

  1. ^ House, Herbert O. (1972). Modern Synthetic Reactions. Menlo Park, CA.: W. A. Benjamin. ISBN 0-8053-4501-9. 
  2. ^ Malonic Ester Synthesis. Organic Chemistry Portal. Retrieved on 2007-10-26.
  3. ^ Smith, Janice Gorzynski. Organic Chemistry: Second Ed. 2008. pp 905-906
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Malonic_ester_synthesis". A list of authors is available in Wikipedia.
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