Synthesis of some new [1,2,4]triazolo[3,4-b][1,3,4]thiadiazines and [1,2,4]triazolo[3,4-b][1,3,4] thiadiazoles starting from 5-nitro-2-furoic acid and evaluation of their antimicrobial activity.

New series of fused 1,2,4-triazoles such as, 6-(aryl)-3-(5-nitrofuran-2-yl)-5,6-dihydro-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles 4-8, 6-(alkyl/aryl amino)-3-(5-nitrofuran-2-yl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles 9-13 and 6-(4-substituted phenyl)-3-(5-nitrofuran-2-yl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines 14-18 have been synthesized via the reaction of 4-amino-5-(5-nitrofuran-2-yl)-4H-1,2,4-triazole-3-thiol 3 with various reagents such as hetero aromatic aldehydes, alkyl/aryl isothiocyanates and 4-substituted phenacyl bromides, respectively. The structures of the newly synthesized compounds have been confirmed on the basis of elemental analysis and spectral studies. The newly synthesized triazolo derivatives have been investigated for their in vitro antibacterial activity. Most of the tested compounds showed interesting antibacterial activity against Staphylococcus aureus. Furthermore, the most potent antibacterial compounds 11-13 were evaluated for their in vitro cytotoxic activity against human cancer cell lines. It was found that compounds 11 and 13 showed higher cytotoxicity against Hep-G2 cell line as compared to standard.