By varying the acidity, solvent polarity, and temperature of the reaction of thiosemicarbazide with ethyl 4-chloroacetoacetate, ethyl 2-amino-6H-1,3,4-thiadiazine-5-acetate hydrochloride, ethyl 2-hydrazinothiazole-4-acetate, and ethyl 2-imino-3-aminothiazoline-4-acetate hydrochloride may be prepared selectively. Further derivatives may be prepared by benzoylation and nitrosation. These compounds have demonstrated utilities as herbicides.