Investigation of tartaric acid amide formation by thermolysis of tartaric acids with alkylamines

Abstract

N,N'-dialkyltartramides were obtained by conventional thermolysis at 200 °C without a solvent, of the L-, D- or meso-tartaric acids with butyl-, hexyl- and octylamine, respectively. The products proved in all cases to be mixtures of all the possible stereoisomers, in ratios that depended on the stereochemistry of the tartaric acid applied, retaining an excess of the configuration of the starting material. Isomerization of the initially formed diamide did not take place under the reaction conditions. Mechanistically the transformation was rationalized in terms of two competing pathways - the direct substitution of the alkylamine into the carboxylic acid group, - in competition with ketene formation and subsequent amide formation. As a method for stereoselective synthesis of optically active N,N'-dialkyltartramides, the method may be considered obsolete and of little practical value; however, it provided new insight into the mechanisms of amide formation. © ARKAT-USA, Inc.