Design, synthesis and fungicidal activity of novel 3(2H)-pyridazinone derivative containing arylpyrazole motif

In order to discover the compounds with high fungicidal activities, a series of novel compounds(C1-C22) were designed and synthesized by synthesised using the Intermediate Derivatisation Method (IDM). The arylpyrazole intermediate was modified by introducing a pyridazine substructure, and the resulting compounds were characterized by ¹H NMR, ¹³C NMR and HRMS. By means of the lead discovery and structural optimization, the compound C14 bearing 4-F atom in the benzene ring with optimal activity was found, which showed significantly better activity(100%) than the control compound flumorph(10%) at 6.25 mg/L against cucumber downy mildew, and equal control efficacy at a lower dose of 3.13 mg/L (85% control efficacy) to the commercial cyazofamid(85% control efficacy). Further research is warranted.