Design, synthesis and structure–activity relationship of novel diphenylamine derivatives

[Display omitted] Diphenylamine derivatives have been reported with good fungicidal, insecticidal, acaricidal, rodenticidal and/or herbicidal activities. To find new lead compound of this kind, a series of novel diphenylamine derivatives were designed and synthesized by the approach of Intermediate Derivatization Methods. All compounds were identified by 1H NMR and elemental analysis. Bioassays demonstrated that some compounds substituted at 2,4,6-positions or 2,4,5-positions of phenyl ring B exhibited excellent fungicidal activities. The optimal compounds P30 and P33 showed 80% and 85% control respectively against cucumber downy mildew at 12.5mgL−1, both 100% control against rice blast at 0.3mgL−1 and both 100% control against cucumber gray mold at 0.9mgL−1. The relationship between structure and fungicidal activities was discussed as well.