Abstract
A new method for the synthesis of 1,3,4-thiadiazoles is described. Thus condensation of 4-methyl-4phenyl-3-thiosemicarbazide with an aldehyde or ketone affords 1,1-disubstituted-6-[1-(arylethylidine) amino] −2,5-dithiobiureas, rather than the anticipated 4,4-disubstituted-3-thiosemicarbazones. Refluxing the 2,5-dithiobiureas in ethanol containing acetic acid as catalyst gave the corresponding 1,3,4-thiadiazol-2-yl hydrazones. Furthermore, refluxing a solution of a 4,4-disubstituted-3-thiosemicarbazone in acetonitrile containing acetic acid as catalyst also afforded 1,3,4-thiadiazol-2-yl hydrazones in excellent yield. Arylethylideneamino-2,5-dithiobiurets are thought to be intermediates in the latter reaction.