Action of alkali metals in liquid ammonia on substituted thiophenes. Communication 9. Preparation of 5-mercapto-4-ketoalkanoic acids by reductive cleavage of 4-acetylamino- and 4-nitrothiophene-2-carboxylic acids

Abstract

1. Opening of the thiophene ring in acetylamino-2-thiophenecarboxylic acids by the action of Na in liquid ammonia leads to salts of 4-acetylamino-5-mercaptoalkenoic acid. After alkylation and saponification these salts are converted to 5-alkylthio-4-ketoalkanoic acids. 2. A preparative method has been developed for the synthesis of 5-alkylthio-4-ketoalka-noic acids by reductive cleavage of 4-nitro-2-thiophenecarboxylic acids.