Background: Triazolothiadiazoles are molecules of great synthetic and pharmacological
significance. They are associated with significant antimicrobial, antifungal, antibacterial, antihelmintic
and anti-inflammatory activities.
Method: The condensation of 5-alkyl-4-amino-3-mercapto-4H-1,2,4-triazoles with 3-aryl-1-
phenylpyrazole-4-carboxylic acids was carried out in the presence of phosphoryl chloride and the resulting
products were tested in vitro for their antibacterial potential against Bacillus subtilis (gram positive),
Staphylococcus aureus (gram positive), Escherichia coli (gram negative) and Pseudomonas
aeruginosa (gram negative) and further antifungal properties against Candida albicans, and Saccharomyces
Results: A new series of 3-alkyl-6-(3-aryl-1-phenyl-1H-pyrazol-4-yl)-[1,2,4]triazolo[3,4-b][1,3,4]
thiadiazoles has been synthesized by the reaction mentioned above. One specific compound, 6-(3-(4-
an excellent antifungal activity against Candida albicans with a MIC value of 8 µg/ml, which is actually
even better than the standard drug Amphoptericin B (MIC 10 µg/ml).
Conclusion: An expeditious synthesis of several new 3-alkyl-6-(3-aryl-1-phenyl-1H-pyrazol-4-yl)-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles in 77-89 % yield could be performed from readily accessible
starting materials, 5-alkyl-4-amino-3-mercapto-4H-1,2,4-triazoles and 3-aryl-1-phenylpyrazole-4-
carboxylic acids. Most of the resulting compounds showed moderate to good in vitro activity against
Gram-positive bacteria. The title compounds seem to be more active against fungi than bacteria.