Heterocyclic compounds from urea derivatives. Part XXIII. Thiobenzoylated thiocarbonohydrazides and their cyclisation

Abstract

Thiobenzoylation of thiocarbonohydrazide produces successively 1-thiobenzoyl- and 1,5-bis(thiobenzoyl)-thiocarbonohydrazide in moderate yield, together with their cyclisation products, principally 4-amino-3-mercapto-5-phenyl-1,2,4-triazole. S-Methylisothiocarbonohydrazide yields 2,3-dihydro-1-methylthio-4-phenyl-2,3,5,6-tetrazine as the main product in this reaction. The labile 5-thiobenzoyl derivative of 1-phenylthiocarbonohydrazide is cyclised to 2-phenyl-5-phenylhydrazino-1,3,4-thiadiazole in acid, and to 4-anilino-3-mercapto-5-phenyl-1,2,4-triazole in alkaline media. 2-Aryl-5-phenylazo-1,3,4-thiadiazoles arising as by-products in the alkaline cyclisation are the principal products of the oxidation of the 5-phenylhydrazino-analogues.