Studies on Synthesis and Pharmacological Activities of 1,2,4-Triazolo[3,4-b]1,3,4-thiadiazoles and their Dihydro Analogues

4-Amino-5-substituted aryl-3-mercapto-1,2,4-triazoles are versatile synthons for constructing various biologically active heterocycles. Starting from 4-amino-5-substituted aryl-3-mercapto-1,2,4-triazole 3a-c, a series of new 3,5-disubstituted-1,2,4-triazolo-[3,4-b]1,3,4-thiadiazoles and their 5,6-dihydrotriazolothiadiazoles were prepared. The structures of all the newly synthesized compounds have been confirmed by elemental analysis, IR,H-1-NMR, C-13-NMR, and mass spectra. The antimicrobial effects of the synthesized compounds were investigated using the paper disc method. Anti-inflammatory and analgesic activities of the synthesized compounds were assessed by carrageenan-induced rat paw oedema method and by Eddy's hot plate method, respectively. Some of the compounds exhibited promising antimicrobial activities as well as moderate to good anti-inflammatory activity and analgesic activity.