Darzens reaction

The Darzens reaction (also known as the Darzens condensation or glycidic ester condensation) is the chemical reaction of a ketone (or aldehyde) with an α-haloester to form α,β-epoxy esters (2). α,β-Epoxy esters, also called glycidic esters, upon hydrolysis yield aldehydes or ketones (4).^[1] This reactions was discovered by the organic chemist Auguste George Darzens (1867-1954).

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Several reviews have been published.^[2][3][4]

Reaction mechanism

The reaction is base initiated, which leads to the generation of a stabilized carbanion (or ester enolate). Nucleophilic attack of a carbonyl group by the carbanion follows. The unstable anion attacks intramolecularly via a S_N2 mechanism, with chloride as a leaving group. The product is an α-epoxyester. A new carbon-carbon bond is formed in the process. In this case EtO^- should be used as a base to prevent ester hydrolysis.

References

1. ^  (a) Darzens, G. Compt. Rend. 1904, 139, 1214. (b) Darzens, G. Compt. Rend. 1905, 141, 766. (c) Darzens, G. Compt. Rend. 1906, 142, 214.
2. ^  Newman, M. S.; Magerlein, B. J. Org. React. 1949, 5, 413. (Review)
3. ^  Ballester, M. Chem. Rev. 1955, 55, 283. (Review)
4. ^  Rosen, T. Comp. Org. Syn. 1991, 2, 409-439. (Review)

See also

• Johnson-Corey-Chaykovsky reaction
• Reformatskii reaction