Synthesis and fungicidal activity of fluorine-containing chlorothalonil derivatives

•Application of the strategies of intermediate derivatization method.•Trifluoromethyl, a very strong electron withdrawing group, plays an important role on fungicidal activity.•Characterization of target compounds using 1H NMR, 13C NMR, 19F NMR, elemental analysis, HRMS and X-ray.•Excellent fungicidal activity against Puccinia polysora.•Detailed structure and activity relationship of target compounds.

Fourteen new fluorine-containing chlorothalonil derivatives were synthesized by using intermediate derivatization method (IDM) in order to discover novel antifungal compounds for controlling corn rust. The structures of synthesized compounds were confirmed by 1H NMR, 13C NMR, 19F NMR, elemental analysis, HRMS and X-ray. The bioassay results indicated that compound 2,4,5-trichloro-6-(2,6-dichloro-4-[trifluoromethyl]phenylamino)isophthalonitrile (3j, Rn is 2,6-Cl2-4-CF3) had the optimal structure with best fungicidal activity against corn rust (98%, 70% controls) at 25 and 6.25 mg/L concentration, respectively, much better than chlorothalonil and fluazinam, highlighting the importance of trifluoromethyl group on 4-position of benzene ring. The structure–activity relationship of the synthesized compounds was discussed as well.

Graphical abstractChlorothalonil, a commercialized fungicide with very low cost, was employed as the starting material to achieve a series of novel N-diphenylamines with excellent fungicidal activity against Southern Corn Rust. Trifluoromethyl group on 4-position of substituted phenyl plays an important role in enhancing the biological activity of target compounds.Figure optionsDownload full-size imageDownload as PowerPoint slide