Enaminones as Building Blocks in Heterocyclic Preparations: Synthesis of Novel Pyrazoles, Pyrazolo[3,4-d]pyridazines, Pyrazolo[1,5-a]pyrimidines, Pyrido[2,3-d]pyrimidines Linked to Imidazo[2,1-b]thiazole System

6-Arylimidazo[2,1-b]-1,3,4-thiadiazole-2-sulfonamides 3 on Vilsmeier-Haak reaction produced 5-formyl-6-arylimidazo[2,1-b]-1,3, 4-thiadiazole-2-[N-(dimethylaminomethino)]sulfonamides 4, while 3 on treatment with potassium thiocyanate in the presence of bromine in acetic acid produced 5-thiocyanato-2-sulfonamides 6. Interaction of 4 with aminoguanidine hydrochloride in ethanol produced the corresponding 5-guanylhydrazone derivatives 5. Compounds 5 and 6 showed a high degree of antibacterial activity against both Escherichia coli and Staphylococcus aureus comparable to that of sulfamethoxazole and Norfloxacin. However, they were found to show moderate activity against Salmonella typhi, Pseudomonas aeruginosa and Pneumococci. Show more