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

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.