Synthesis and cytotoxic activity of certain new arylazothiazole containing compounds

2‐Amino‐5‐arylazo‐4‐(2‐chlorophenyl)thiazoles ( 2a‐e ) were prepared by the coupling of aryldiazonium chlorides with 2‐amino‐4‐(2‐chlorophenyl) thiazole ( 1 ). The thioureas 3a‐e were obtained by condensing the arylazothiazoles 2a‐c with the appropriate isothiocyanates. Reaction of 2d with aromatic aldehydes afforded the chalcone analogues 4a‐c . The pyridone derivatives 5a,b were synthesized by reacting the ketone 2d with different aromatic aldehydes, ethyl cyanoacetate and ammonium acetate. On the other hand, 5b was also prepared by cyclizing 4c with ethyl cyanoacetate and ammonium acetate. Furthermore, 6‐chloroimidazo2,l‐b]‐thiazole 7 was obtained from the acid derivative 6b by treatment with POC1₃. While, the imidazo2,l‐b]‐thiazolones 9a‐d were produced by the cyclization of the chloroacetyl derivatives 8a‐d with DMAP/pyri‐dine. Representative examples of the prepared compounds were tested for in vitro antitumor activity against two human tumor cell lines. Some compounds showed activity against brain tumor cell lines.