Ring transformations of 5-chloro-1,2,3-thiadiazole-4-carbaldehyde with amines, hydrazines and hydroxylamine

Abstract

5-Chloro-1,2,3-thiadiazole-4-carbaldehyde, prepared in four steps from 1,3-dichloroacetone, reacts with alkyl- and aryl-amines in alcohol solution to give 1,2,3-triazole-4-thiocarboxamides 9a–f. Similarly, hydrazine and N-aminomorpholine furnish the 1,2,3-triazole-4-thiohydrazides 9g and 9h, whereas phenylhydrazine and hydroxylamine yield unrearranged products 8i and 8j. These, however, are transformed into 1,2,3-triazole-4-carboxylic acids 14i and 14j upon storage in dimethyl sulphoxide solution. The mechanism of the rearrangement is discussed.