Dianions Derived from α-Halo Acids. The Darzens Condensation Revisited

Article abstract of DOI:10.1021/jo00346a013

The dianions of α-halo carboxylic acids are readily generated by the addition of the acids to 2 equiv of lithium diisopropylamide at low temperatures.When the mixture warms to room temperature dimeric products are formed.When aldehydes and ketones were added to the cooled solutions of the dianions and the reaction mixtures were allowed to warm to room temperature, followed by acid quench, glycidic acids were formed.The glycidic acids, per se, were often too unstable to be isolated and purified but could be analyzed by conversion to their methyl esters withdiazomethane.When the reactions were quenched prematurely, α-chloro-β-hydroxy carboxylic acids were isolated.Homologated aldehydes and ketones were obtained from the glycidic acids by catalytic and thermal decarboxylation methods.