Main products of reaction between benzothiazole-2-thione and a double excess of nitrilimine are substituted 1-aryl-1-(1,3-benzothiazol-2-yl)-2-(2,3-dihydro-1,3,4-thiadiazol-2-yl)hydrazines. In the first step presumably forms a spiro compound via 1,3-dipolar cycloaddition of nitrilimine molecule to the C=S bond of the benzothiazolethione. The second nitrilimine molecule adds to the new C=S bond of the intermediate product arising by the rupture of C-S bond in the thiadiazole ring of the spiro compound.