Condensed bridgehead nitrogen heterocyclic systems:: Microwave assisted synthesis and bioactivity of s-triazolo[3,4-b][1,3,4]thiadiazoles, s-triazolo[3,4-b][1,3,4]thiadiazines and s-triazolo [3′,4′:2,3]-thiadiazino[5,6-b]quinoxaline

N-[3-(4-Amino-5-mercapto-4H-[1,2,3]triazol-3-yl)-4,5,6,7-tetrahydrobenzo[b] thiophen-2-yl]acetamide 1 on condensation with chloroacetic acid, alpha-haloketone and benzoin furnishes [1,2,4]triazolo[3,4-b][1,3,4]thiadiazine derivatives 2, 3 and 4 respectively, while condensation with 2,3-dichloroquinoxaline, carbon disulphide, aromatic carboxylic acid and aromatic carboxaldehydes yield the cyclic products, [1,2,4] triazolo[3,4-b][1,3,4]thiadiazole derivatives 5, 6, 7, 8 respectively. The compounds have been characterized on the basis of elemental analysis and spectral data. The antibacterial, antifungal and antitubercular activities of the compounds have also been evaluated.