Regioselective synthesis of new 2-(E)-cyano(thiazolidin-2-ylidene)thiazoles.

Cyclocondensation of 2-[bis(methylthio)methylene]malononitrile (1) and cysteamine (2) afforded 2-(thiazolidin-2-ylidene)malononitrile (3). This compound on treatment with NaSH gave the corresponding thioamide derivative 4a in a regioselective manner on the basis of its single crystal X-ray diffraction analysis. Reaction of this compound with several alpha-bromocarbonyl compounds gave new 2-(E)-cyano(thiazolidin-2-ylidene)thiazoles 5a-g.