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

Abstract 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 1 H NMR, 13 C 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 (EC 50  = 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 (EC 50  = 1.03 mg/L), equal to commercial pyraclostrobin (EC 50  = 1.06 mg/L). The study showed that compound 20 is a promising fungicide for further development.