Heterocyclic systems containing bridgehead nitrogen atom:: Synthesis and bioactivity of thiazolo [3,2-b]-s-triazoles and isomeric thiazolo [2,3-c]-s-triazoles

Synthesis of 2,5-disubstituted thiazolo [3,2-b]-s-triazoles 4 has been achieved starting from the appropriate 5-mercapto-3-p-nitrophenyl-s-triazole 2.2 on condensation with alpha-haloketone gave the ketone 3 which on cyclization with PPA afforded thiazolo [3,2-b]-s-triazoles 4 and not the isomeric thiazolo [2,3-c]-s-triazoles 6. This has been established by an unequivocal synthesis of 6 through POCI3 cyclization of 2-benzoyl-hydrazino 4 chlorophenylthiazole hydrobromide 5. The synthesis of 3 and 5 was achieved more conveniently in better yield by treating 2 and 1 directly with ketones in the presence of NBS. The latter method is more convenient & versatile. The diuretic, antibacterial and antifungal activity of some of the compounds, have also been evaluated.