Abstract Benzoyl and ethoxycarbonyl isothiocyanates reacted with 2-cyanoethanoic acid hydrazide 2 to afford 1-cyanoacetyl-4-substituted thiosemicarbazide (5a, b). Compound 5a afforded the pyrazolo [1, 5-a]-s-triazine derivative 6 on treatment with 5% potassium hydroxide, and cyclised to 2-benzoylamino-5-cyanomethyl-1, 3, 4-thiadiazole (8) when boiled under reflux in glacial acetic acid. Compound 8 condensed with aromatic ...