The Darzens glycidic ester condensation

This reaction involves the condensation of an aldehyde or ketone with an a-halo ester in the presence of a basic condensing agent (sodium ethoxide, sodamide, finely divided sodium or potassium teri.-butoxide) to give a glycidic (or p-epoxy) ester. Thus acetophenone and ethyl chloroacetate yield phenyl-methyl glycidic ester (I)  

The glycidic esters are of interest primarily because upon hydrolysis and decarboxylation they afford aldehydes (if ClCHjCOOEt is used) or ketones (if substituted chloroacetic esters-ClCHKCOOEt are employed) having a higher carbon content than the original aldehyde or ketone. Thus (I) gives o-phenyl-proplonaldehyde or hydratropaldehyde (II)  

The decomposition of a glycidic ester to an aldehyde and carbon dioxide may involve the formation of a quasi six-membered ring, followed by the shift of three electron pairs  

Add the salt to dilute hydrochloric acid (prepared from 28 ml. of the concentrated acid and 150 ml. of water) contained in a 500 ml. flask fitted with a reflux condenser. Warm the mixture gently carbon dioxide is evolved and an oil separates. Heat on a steam bath for 90 minutes, cool, and extract the oil with 76 ml. of benzene. Wash the extract with 100 ml. of water, and distil the benzene solution under reduced pressure from a Claisen flask. Collect the a-phenylpropionaldehyde at 90-93°/10 mm. the yield is 30 g. 

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Allen and Van Allen, Org. Syntheses, 24, 82 (1944). For a review of the Darzens glycidic ester condensation of which this synthesis is an example, see Magerlein in Adams Organic Reactions, Vol. V, p. 413, John Wiley and Sons, Inc., New York, 1949. 

The Darzens glycidic ester condensation involves the condensation of an aldehyde or ketone with an a-halo ester, in the presence of a base, to afford an a,3 epoxy ester (a glycidic ester ). The first synthesis of a glycidic ester was reported by Erlenmeyer in 1892 and is illustrative of the general reaction, as shown in equation (1). The reaction was subsequently developed and generalized by Darzens. Glycidic esters, in addition to undergoing transformations normally associated with epoxides, afford upon hydro-... 

The Darzens Glycidic Ester Condensation Melvin S. Newman and Barney J. Magerlein... 

B.vi. Tbe Darzens Glycidic Ester Condensation. When an a-halo ester is treated with base and the resulting enolate anion condensed with a carbonyl derivative, the product is an alkoxide. This nucleophilic species can displace the halogen intramolecularly to produce an epoxide, which forms the basis of a classical reaction known as the Darzens glycidic ester condensation. 13S Reaction of ethyl a-chloroacetate and sodium ethoxide, in the presence of benzaldehyde. generated the usual alkoxide (221). Intramolecular displacement... 

The Darzens Glycidic Ester Condensation. When an aldehyde (or ketone) is allowed to react with the carbanion formed by proton abstraction from a halogenbearing carbon a to the carbonyl of an ester, RCO2R (this Chapter), an oxirane (epoxide) results. These compounds, containing an oxirane (epoxide) a,p to the carbon of the carbonyl of the ester, are known as glycidic esters. An accepted... 

Scheme 9.54. A representation of a pathway by which a glycidic ester undergoes hydrolysis and then, on acidification, decarboxylation to produce a new aldehyde.The backbone of the product aldehyde is one carbon atom longer than the original aldehyde undergoing the Darzens glycidic ester condensation.

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