Reactions of thiazoline-2-thione with C,N-disubstituted nitrile imines were investigated. The reaction products are substituted 2-(1,3,4-thiadiazol-2-ylideneamino)ethanethiols and bis[2-(1,3,4-thiadiazol-2-ylideneamino)ethyl] disulfides. The reaction of thiazoline-2-thione with a double excess of nitrile imine did not considerably change the process route. The structure of compounds obtained was proved by X-ray diffraction analysis. A presumable scheme is given describing the formation of compounds obtained.The reactivity of compounds containing in the molecule N=CSH or NHC=S moiety is quite versatile [26]. The thione-thiol tautomerism existing in compounds of this structure makes them capable to react with C 1,3-dipolar systems at different reaction centers. Consequently these compounds in reactions with 1,3-dipolar reagents can form both products of N-or S-substitution, and also products of 1,3-dipolar cycloaddition. It is known however [7,8] that reactions of some of these compounds with hydrazonoyl chlorides in the presence of triethylamine give rise to products of decomposition of intermediate unstable adducts having spiro structure.We formerly demonstrated [9, 10] that reaction of benzothiazole-2-thione with C,N-disubstituted nitrile imines proceeded through formation of intermediate spiro compound where both CS were labile, and the cleavage of any of these bonds was reversible.Here we report the results obtained in investigation of the reaction between thiazoline-2-thione and C,N-disubstituted nitrile imines. Nitrile imines were prepared in situ by treating with triethylamine appropriate hydrazonoyl chlorides IIaIIi.We established that the reaction of thiazoline-2-thione (I) with nitrile imines afforded substituted bis[2-(1,3,4-thiadiazol-2-ylideneamino)ethyl] disulfides IIIac, IIIe, IIIf, and IIIh, and 2-(1,3,4-thiadiazol-2-ylideneamino)-ethanethiols IVa, IVd, IVg, and IVh.