Synthesis and Biological Activities of New Thiadiazolyl 3-pyridazinones

Eight new thiadiazolyl 3(2H)-pyridazinones compounds were synthesized by the reaction of 2-tert-butyl-4-chloro-5-hydroxy-3(2H)-pyridazinones with 5-aryl-2-chloromethyl-1,3,4-oxadiazoles which were prepared by the cyclization of N-chloroacetyl-N'-aroylhydrazines. The structure of the title compounds were confirmed by 1H NMR, HR mass spectra and elemental analysis. Their biological activities were examined and some of them exhibited good activities against Pseudaletia separate Walker. The EC50 of 3b was 21 mg/L.