Synthesis and fungicidal activity of fluorine-containing chlorothalonil derivatives

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 H-1 NMR, C-13 NMR, F-19 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, R-n 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. (C) 2014 Elsevier B.V. All rights reserved.