Synthesis, crystal structure, biological evaluation, docking study and DFT calculation of novel strobilurins containing oxime ether phenyl ring or dihydrobenzofuran moiety

Two sets of strobilurin derivatives containing oxime ether phenyl ring or dihydrobenzofuran moiety were designed, synthesized and evaluated for their fungicidal and insecticidal activities. The structures of the target compounds were determined by 1H NMR, 13C NMR and elemental analysis, and the crystal structure of compound 3a was further determined by X-ray diffraction analysis. Some of the title compounds exhibited certain degree of fungicidal and insecticidal activities at the concentration of 500 mg/L. The control effects of compounds 1, 4a and 8 against Erysipe graminis and 1, 3a, 4a and 8 against Puccinia sorghi were all above 90%, which were close to the level of trifloxystrobin. The lethal rates of compounds 5a and 6a against Mythimna separata reached 100%, similar to that of positive control chlorantraniliprole, and the lethal rates of compounds 1, 2 and 8 against Aphis fabae were 100%, 100% and 98.6%, respectively, numerical equivalent to that of imidacloprid. Furthermore, molecular docking showed the potential mechanism for fungicidal activities of these compounds, and DFT calculation indicated that the frontier molecular orbitals and van der Waals surface electrostatic potentials could be related to insecticidal activity.