Reaction of hydrazonyl halides with (substituted) thioureas and thiosemicarbazides gives mainly 1,3,4-thiadiazolines, the stronger base being preferentially eliminated in the process. Similar reactions in presence of triethylamine give C-amino- and C-hydrazino-1,2,4-triazoles, respectively, together with the hydrazonyl sulfide.Potassium cyanide cleavage of a hydrazonyl disulfide gives the corresponding 1,3,4-thiadiazoline and thiohydrazide.