Heterocyclic systems containing bridgehead nitrogen atom: synthesis and bioactivity of 3-(2-thienyl)-s-triazolo[3,4-b][1,3,4]thiadiazole, 2-(2-thienyl)thiazolo[3,2-b]-s-triazole and isomeric 3-(2-thienyl)-thiazolo[2,3-c]-s-triazole

摘要

The synthesis of 2-(2-thienyl)-5-p-bromophenylthiazolo[3,2-b]-s-triazole 5 has been achieved starting from 5-mercapto-3-(2-thienyl)-s-triazole 3. Compound 3 on condensation withp-bromophenacyl bromide gives the ketone 4 which on cyclization with PPA affords, 5-p-bromophenyl-2-(2-thienyl)thiazolo[3,2-b]-s-triazole 5 and not the isomeric 5-(p-bromophenyl)-3-(2-thienyl)thiazolo[2,3-c]-s-triazole 7. This has been established by an unequivocal synthesis of 7 through POCl_3 cyclization of 2-thienoylhydrazino-4-p-bromophenyl thiazole hydrobromide 6. However, the condensation of 4-amino-3-(2-thienyl)-5-mercapto-s-triazole 8 with carbon disulphide furnishes 3-(2-thienyl)-s-triazolo[3,4-b][1,3,4]thiadiazole-6(5H)-thione 9 in one step only. The diuretic, antibacterial and antifungal activities of these compounds have also been evaluated.