Efficient synthesis of some novel symmetrical and unsymmetrical pyridine bis-1,2,4-triazoles and bis-1,3,4-thiadiazoles

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 aryl-isothiocyanates 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-1,3,4-thiadiazoles) were obtained. The synthetic routes and spectroscopic characterisation of the new compounds are reported.