Synthesis of pharmaceutically important condensed heterocyclic 4,6-disubstituted-1,2,4-triazolo-1,3,4-thiadiazole derivatives as antimicrobials.

The two series of 4,6-disubstituted 1,2,4-triazolo-1,3,4-thiadiazole derivatives 2(a-e) and 3(a-e) were synthesized and characterized using IR, (1)H-NMR, CHNS analysis and by single crystal X-ray crystallographic studies. The compound 6-(2-chloro-phenyl)-3-ethyl-[1,2,4]triazole[3,4-b]thiadiazole 2b has been characterized by single crystal X-ray diffraction method. The compound crystallizes in monoclinic space group P2(1)/c with a cell parameters a = 11.879(1) Angstroms, b = 15.112(2) Angstroms, c = 13.95(2) Angstroms, Z = 8 and the final R factor is R1= 0.0524. The structure exhibits both intra and intermolecular hydrogen bonds. The title compounds were checked for their efficacy as antimicrobials in vitro. Compounds 2b, 2c, 2d, 3b, 3c and 3d showed significant inhibition against all the strains tested, when compared to standard drugs.