Design,synthesis, and fungicidal activity of novel 1,3,4-oxadiazole derivatives

Employing the intermediate derivatization method (IDM), twenty novel 1,3,4-oxadiazole derivatives containing arylpyrazoloxyl moiety were designed and synthesized. The structures of the title compounds were identified by ¹H NMR, ¹³C NMR, MS and elemental analyses, compound 4 was further identified by single-crystal X-ray diffraction. Antifungal activities against rice sheath blight (RSB) and sorghum anthracnose (SA) were evaluated by the mycelium linear growth rate method. Compounds 4, 16 and 20 displayed significant activities against RSB (EC₅₀ = 0.88 mg/L, 0.91 mg/L and 0.85 mg/L, respectively), higher than the reference tebuconazole; While compound 3 exhibited higher activity against SA (EC₅₀ = 1.03 mg/L), equal to commercial pyraclostrobin (EC₅₀ = 1.06 mg/L). The study showed that compound 20 is a promising fungicide for further development.