Synthesis and anticancer activity of arylazothiazoles and 1,3,4-thiadiazoles using chitosan-grafted-poly(4-vinylpyridine) as a novel copolymer basic catalyst

A novel series of 4-substituted 5-arylazo-2-[1-(pyrrol-3-yl)ethylidenehydrazinyl]thiazoles and 5-arylazo-2-[1-(pyrrol-3-yl)ethylidenehydrazinyl]-2,3-dihydrothiazol-3-amines was prepared by cyclocondensation of alpha-oxohydrazonoyl halides with 1-(pyrrol-3-yl)-ethylidenethiosemicarbazide and 1-(pyrrol-3-yl)ethylidenethiocarbohydrazide, respectively. These cyclocondensation reactions were achieved by using chitosan-grafted-poly(4-vinylpyridine) as a novel basic catalyst under microwave irradiation. Furthermore, the reaction of the above mentioned thiosemicarbazide and thiocarbohydrazide with N-phenylbenzenecarbohydrazonyl chlorides (bereft of the alpha-oxo group) using chitosan-grafted catalyst proceeded via a similar mechanism and afforded the same 2-hydrazono-1,3,4-thiadiazoles. The structures of the newly synthesized compounds were established on the basis of spectroscopic evidences as well as by their synthesis via alternative methods. Finally, the appraisal of the newly synthesized products for their anticancer activity against a colon carcinoma cell line (HCT-116) and liver carcinoma cell line (HEPG2-1) revealed promising activity, especially 4-phenyl- and 4-(thiophen-2-yl)-substituted 1,3-thiazole derivatives.