Mannich bases and novel benzothiazole derivatives of imidazo[2,1-b][1,3,4]thiadiazoles and their biological evaluation

A series of 2,6-disubstituted imidazo[2,1-b][1,3,4]thiadiazoles, their new Mannich bases and novel benzothiazole derivatives were synthesized. The structures of all the synthesized compounds were established by analytical and spectral data. All the compounds were screened for their antitubercular activity against Mycobacterium tuberculosis H₃₇Rv using the BACTEC 460 radiometric system and antibacterial activity against E. coli and B. cirrhosis, antifungal activity against A. niger and P. worthmanni. Among the tested compounds Mannich bases 3e, 3f and 4 g and 5-carbaldehyde derivative 6d have shown excellent inhibition (99, 99, 97 and 95%, respectively) against M. tuberculosis. Mannich bases in general have also shown impressive antifungal activity.     

Chemoselectivity of thiophene dicarboxylate towards hydrazine hydrate: Synthesis of some new bis heterocycles from thiophene monocarbohydrazide

Chemoselectivity of C₅-carbethoxy function over that of C₃-carbethoxy function of the thiophene dicarboxylate towards the nucleophilic attack of hydrazine hydrate has been evidenced by exclusive formation of monocarbohydrazide i.e. ethyl 2-amino-5-(hydrazinocarbonyl)-4-methylthiophene-3-carboxylate and this monocarbohydrazide was reacted separately with acetylacetone, cyanogen bromide, acetonylacetone and CS₂ in ethanolic potassium hydroxide solution to furnish corresponding derivatives of 3,5-dimethylpyrazole, 5-aminooxadiazole, 2,5-dimethylpyrrole and 5-thiooxadiazole respectively. Thiophene monocarbohydrazide was converted to hydrazone derivatives by reacting with p-chlorobenzaldehyde and isatin. The monocarbohydrazide was also converted to thiosemicarbohydrazide derivatives, which was then cyclised with POCl₃ to afford corresponding thiadiazole derivatives. The structures of all the newly synthesized compounds were elucidated on the basis of their spectral and analytical data and the compounds were screened for their antituberculosis, antibacterial and antifungal activities.