Synthesis of novel thiadiazolotriazin-4-ones and study of their mosquito-larvicidal and antibacterial properties

• We synthesized novel heterocyclic compounds thiadiazolotriazin-4-ones (5a–5n).
• These were characterised by IR, 1H NMR, 13C NMR and mass-spectral studies.
• 5f exhibits mosquito-larvicidal activity to a good extent.
• 5i and 5m possess broad-spectrum antibacterial property.
• Toxicity studies indicate that 5f, 5i and 5m fall under the class slightly toxic.

A series of novel 3-tert-butyl-7-(aryloxymethyl)-4H-[1,3,4]thiadiazolo[2,3-c][1,2,4]triazin-4-ones (5a–5n) were synthesized by refluxing 3,3-dimethyl-2-oxobutanoic acid (trimethyl pyruvic acid) (1) and thiocarbohydrazide (2) in ethanol as solvent for 12 h, to yield 3-mercapto-4-amino-6-tert-butyl-1,2,4-triazine-5(4H)-one (3) (Scheme 1), then the compound (3) was condensed with different substituted aryloxyacetic acids (4) in POCl3 at 90 °C for 8 h (Scheme 2). The structures of the newly synthesized compounds were confirmed by IR, 1H NMR, 13C NMR, elemental analyses and mass spectroscopic studies. Few of the synthesized compounds exhibited moderate mosquito-larvicidal and antibacterial activities. Among the novel derivatives, the compound (5f) showed relatively high larvicidal activity against a malaria vector. Compounds (5i) and (5m) exhibited a broad spectrum antibacterial activity against Gram positive and Gram negative species and hence they may be considered as drug candidates for bacterial pathogens.

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