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). This reactions was discovered by the organic chemist Auguste George Darzens (1867-1954).



Several reviews have been published.

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 SN2 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.