Darzen condensation

Drazen Condensation

            This is the chemical reaction of a ketone or aldehyde with an α-haloester in the presence of a base to form an α,β-epoxy ester, also called a "glycidic ester". This reaction is also known as the Darzens condensation or glycidic ester condensation. In 1904 Auguste Georges Darzens, an organic chemist discovered this reaction.

Reaction mechanism:

 

A strong base is used to form a carbanion from haloester. This carbanion is easily formed due to its  resonance-stabilization. This acts as a nucleophilic and attacks

another carbonyl compound, forming a new carbon–carbon bond. These first two steps are similar to a base-catalyzed aldol reaction.

An epoxide is formed as a result of an intramolecular SN2 attack by the oxygen anion on carbon  baring halide ,thus displacing the halide. This reaction is thus a condensation reaction as there is a net loss of HCl when the two reactant molecules join.