Versatile synthesis of N,S-heterocycles containing the antipyrine moiety

A series of novel sulfide derivatives of expected biological activity were synthesized via the reaction of 4-(chloroacetyl) antipyrine (1) with several sulfur nucleophiles. The quantitatively available 2-aminothiazole derivatives 10 and 11 were coupled with pyrazolopyridinyl and aromatic diazonium salts to furnish a new series of the corresponding pyrazolopyridinylazo and arylazo-thiazole dyes 12 and 13. The reaction of 4-(cyanoacetyl) antipyrine (14) with phenyl isothiocyanate afforded the nonisolable adduct 15, which was used as a precursor for the synthesis of polyfunctionally substituted ketene N,S-acetal, dihydrothiazole, and thiazolidinone ring systems.