Glycidic esters from ketones

Darzens-Claiscn reaction Glycidic acid esters from ketones and a-halogenocarboxylic acid esters... 

Glycidic acid esters from ketones GO G-------G GOOR... 

Synthesis of glycidic esters (amides) from an aldehyde or ketone and an a-haloester (amide). 

Early work on the asymmetric Darzens reaction involved the condensation of aromatic aldehydes with phenacyl halides in the presence of a catalytic amount of bovine serum albumin. The reaction gave the corresponding epoxyketone with up to 62% ee.67 Ohkata et al.68 reported the asymmetric Darzens reaction of symmetric and dissymmetric ketones with (-)-8-phenylmenthyl a-chloroacetate as examples of a reagent-controlled asymmetric reaction (Scheme 8-29). When this (-)-8-phenyl menthol derivative was employed as a chiral auxiliary, Darzens reactions of acetone, pentan-3-one, cyclopentanone, cyclohexanone, or benzophenone with 86 in the presence of t-BuOK provided dia-stereomers of (2J ,3J )-glycidic ester 87 with diastereoselectivity ranging from 77% to 96%. 

Apart from the reaction of cyclohexanecarboxylic acid with methyllithium, cyclohexyl methyl ketone has been prepared by the reaction of cyclohexylmagnesium halides with acetyl chloride or acetic anhydride and by the reaction of methylmagnesium iodide with cyclohexanecarboxylic acid chloride. Other preparative methods include the aluminum chloride-catalyzed acetylation of cyclohexene in the presence of cyclohexane, the oxidation of cyclohexylmethylcarbinol, " the decarboxylation and rearrangement of the glycidic ester derived from cyclohexanone and M)utyl a-chloroj)ropionate, and the catalytic hydrogenation of 1-acetylcycIohexene. "... 

Aromatic and aliphatic aldehydes have been prepared in good yields by the decarboxylation and isomerization of the corresponding glycidic acids. Esters of the latter are obtained by treating a ketone with ethyl chloro-acetate in the presence of sodium amide (method 127). The glycidic esters are first converted to the sodium salts with sodium ethoxide and then treated with aqueous hydrochloric acid under gentle reflux. By this procedure, a-phenylpropionaldehyde has been prepared from acetophenone in an over-all yield of 38%. Other details have been discussed. ... 

Since glycidic esters can usually be prepared from carbonyl compounds and chloroacetic esters, hydrolysis of the ester group and decarboxylation of the resulting glycidic acid gives as end-product the aldehyde containing one carbon atom more than those in the aldehyde or ketone ... 

Hydroxy-ester enolates are oxidized by iodine at — 78°C to give the least hindered oxiran. Thus, by generating the /3-hydroxy-ester from a ketone and acetate enolates, the overall conversion represents a stereoselective Darzens condensation. Glycidic esters can also be obtained from the corresponding nitriles via iminoether derivatives prepared by alkoxide-catalysed addition of alcohols to the nitrile group. 

Modified Darzens-Claisen reaction Aldehydes from ketones via glycidic acid tertAmiyX esters Synthesis with addition of 1 -atom... 

Darzens reaction. Typical among the many types of glycidic ester recently obtained from the Darzens reaction of aliphatic and aromatic aldehydes and ketones with esters of chloroacetic acid are (110), (111), and (112). ... 

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... 

Sodium alcohol (s. a. under Cu and Ni(CO)J Darzens-Claisen reaction Synthesis of ketones from aldehydes via glycidic acid esters... 

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