Phenyl isothiocyanate reacts with 2-cyanoacetohydrazide (1) to yield the co
rresponding 1-cyanoacetyl-4-phenylthiosemicarbazide (3), via acid hydrolysi
s of the intermediate 2 whereas cyclization of 3 gave the 1,2,4-triazoles 4
, 1,3,4-thiadiazoles 7 and 1,3,4-thiadiazine-5-ones 9; compound 4a was reac
ted with phenyl isothiocyanate, dicyandiamide, sulfanylacetic acid and benz
aldehyde to afford 11, 13, 14 and 15, respectively.