Synthetic approaches towards the sulfonamide substituted-4,5-diaryl-4H-1,2,4-triazole-3-thiones

A new series of 3-alkylthio-4,5-diaryl-4H-1,2,4-triazoles having a SO2NH2 substituent in the para-position on one of the aryl rings (19/25) were prepared starting from the appropriate benzoic acid hydrazides (15/21). Reaction of the corresponding hydrazides with the appropriate isothiocyanates yielded 16/22, which were cyclized in basic media to give 4,5-diaryl-2,4-dihydro-3H-1,2,4-triazole-3-thiones 17/23. Alkylation of 17/23 afforded the alkylthio compounds 18/24. Final debenzylation was achieved with concentrated sulfuric acid to give the target sulfonamides 19/25.