Synthesis and Antibacterial Evaluation of Some New Thiazole-Based Polyheterocyclic Ring Systems

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.