High yield prodn. of partly known 3-amino-1,2,4-thiadiazoles - by reacting acylguanidines, thiono esters and strong base, then cyclisation with bromine

3-Amino-1,2,4-thaidiazoles of formula (i): where R = H, opt. halogenated 1-18C alkyl, aralkyl or phenyl opt. substd. by halogen, NO2, CF3 or lower alkyl; are prepd. by reacting the acylguanidine where R1 = 1-18C alkanoyl or benzoyl opt. substd. by halogen, NO2, NH2, alkoxy, acetamido or lower alkyl, with R-C(S)-OR2 where R2 is 1-6c alkyl, aralkyl or aryl, in the presence of NaH in polar solvent at -40 to 100 degrees C., and dehydrogenatingly cyclisting the obtd. acyl thioacylguanidine with Br2. (I) are inters. to plant protection agents and pharmaceuticals such as antibacterial sulphnamides.