Enolates acyclic, carboxylic acid derivatives

Diastereoselective Alkylations of Acyclic Enolates of Carboxylic Acid Derivatives... 

Although this methodology is not successful with acyclic carboxylic acid derivatives (e.g. Weinreb amides, A-acyloxazolidinones, carboxylic esters or thioesters), it is possible to reach this kind of valuable enantiomerically enriched products by a simple oxidation with commercial bleach from the corresponding ketone (Scheme 29, top). If the ketone possesses a substituent prone to oxidation, an alternative procedure, involving the formation of a silyl enol ether (which does not need isolation/purification), can be followed instead (Scheme 29, bottom). 

The intramolecular thioacylation of an ester enolate was used for the synthesis of 2-alkylthiopenem carboxylic acid derivatives. Sequential acylations have led to the synthesis of zwitterionic pyrazole-5-thiones from acyclic precursors, whereas 2-ethoxyoxazolidines react with the reagent to afford the products of AAacylation. ... 

Alkylations of acyclic enolates containing a collection of chiral auxiliary groups have been used successfully for the asymmetric synthesis of carboxylic acids. The chiral, nonracemic substrates that have been used include amides, imides, esters, imine derivatives of glycinates and acyl derivatives of chiral transition metals. In these systems either extraannular or chelate-enforced intraannular chirality transfer may control the sense of the alkylation step. 

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