2‐Cyanoacetamido‐thiazole (1) was employed as a key for the construction of 6‐cyano‐7‐oxo‐7H‐thiazolo[3,2‐a]pyrimidine (4) which underwent reaction with hydrazine, malononitrile, ethyl cyanoacetate, and/or various 1,3‐bi‐nuclophilic reagents furnished the corresponding tri‐heterocyclic and tetra‐heterocyclic ring systems 5–12. In addition, the reactions of 1 with various types of arylidene‐malononitriles and/or ethyl 3‐aryl‐2‐cyanoacrylates yielded the corresponding 1‐thiazolyl‐pyridine derivatives 16 and 20, respectively. Furthermore, treatment of the precursor 1 with carbon disulfide and methyl iodide afforded the ketene dithioacetal derivative 21 which cyclized upon heating with hydrazine and/or 2‐aminobenzimidazole into the corresponding derivatives of N‐(thiazol‐2‐yl)‐1H‐pyrazole‐4‐carboxamide 22 and N‐(thiazol‐2‐yl)benzimidazo[1,2‐a]‐pyrimidine‐3‐carboxamide 23. The antibacterial properties of these thiazole‐based heterocycles were examined against panel of two bacterial strains.
N‐(Anisyl)‐5‐(2‐chloroacetamido)‐4‐cyano‐3‐methylthiophene‐2‐carboxamide (3) was synthesized and reacted with several nucleophilic reagents. The reactions with sulfur nucleophiles (namely, mercaptoacetic acid, ethyl 2‐mercaptoacetate, 5‐(phenylamino)‐1,3,4‐thiadiazole‐2‐thiol, 2‐mercapto‐4,6‐dimethyl‐nicotinonitrile, 4‐anilino‐3‐arylazo‐4‐mercapto‐butenones, ethyl 3‐anilino‐2‐arylazo‐3‐mercapto‐acrylates, and ammonium thiocyanate) yielded the corresponding sulfide, thiophene, or thiazolin‐4‐one derivatives, respectively. The reaction with salicylaldehyde (an example of oxygen nucleophile) furnished the targeting benzofuran compound 21. The reactions with nitrogen nucleophiles (namely, piperidine and aniline) yielded the corresponding thiophene‐carboxamide derivatives 23 and 25, respectively. IR, 1H NMR, and 13C NMR were used to deduce the structures of the target thiophene containing compounds. The effect of the synthesized thiophenes on the viability of HepG2, A2780, and A2780CP was determined. The most effective drug was shown by the thienopyridine‐carboxamide compound 11, against liver cancer cell lines (HepG2) and ovarian cancer cell lines (A2780CP and A2780), whose IC50 values were remarkably near those of Sorafenib, the antitumor drug.
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