Synthesis of new 1,2,4-triazole[3,4-b][1,3,4]thiadiazoles bearing pyrazole as potent antimicrobial agents.

A new series of 6-(aryl/heteryl)-3-(5-methyl-1-phenyl-1H-4-pyrazolyl)[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles (7a-j) has been synthesized by the reaction of 4-amino-5-(5-methyl-1-phenyl-1H-4-pyrazolyl)-4H-1,2,4-triazol-3-yl-hydrosulfide (6) with POCl(3) and the corresponding aryl/heteryl carboxylic acid, in ethanol at reflux temperature for 12 h. All the synthesized compounds were tested for in vitro activities against certain strains of bacteria such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli and fungi such as Aspergillus niger, Aspergillus nodulans, Alternaria alternate. Compounds having 4-chlorophenyl (7d), 4-aminophenyl (7f), 4-nitrophenyl (7h) and 3-pyridyl (7i) substituents at 6-position of thiadiazole ring, showed marked inhibition of bacterial and fungal growth nearly equal to the standards. The other new compounds also showed appreciable activity against the test bacteria and fungi.