An efficient synthesis of novel bis-1,2,4-triazole and bis-1,3,4-thiadiazole derivatives starting from terephthaloyl and isophthaloyl chlorides is described. Terephthaloyl or isophthaloyl chloride was allowed to react with hydrazine hydrate in refluxing ethanol to give a corresponding bis-hydrazide derivative. Further reaction of these compounds with isothiocyanates gave bis-thiosemicarbazide derivatives, which then underwent cyclization to bis-1,3,4-thiadiazoles in the presence of sulfuric acid. The cyclization of these compounds in the presence of sodium hydroxide resulted in the formation of bis-1,2,4-triazole-3-thioles. The structure of these compounds was characterized by IR, NMR, and elemental analysis.

A series of novel bis-1,2,4-triazoles and bis-1,3,4-thiadiazoles bearing pyridine rings was synthesised, by multistep reaction sequences, in good to high yields. Reaction of pyridine-2,5-bis-and pyridine-2,6-bis-carbohydrazides with alkyl-or arylisothiocyanates gave the corresponding bis(thiosemicarbazide) derivatives, which could be cyclised under strongly basic conditions to give novel pyridine bis(1,2,4-triazole-3-thiols). However, under strongly acidic conditions the corresponding bis(2-amino-1,3,4thiadiazoles) were obtained. The synthetic routes and spectroscopic characterisation of the new compounds are reported.

All products are purified by recrystallization.