Design, Synthesis and Insecticidal Activity of 3-(Ethylsulfonyl)-Pyridines Bearing Trifluoromethyl-Oxadiazole Fragment

Background: Oxadiazole fragment is one of the most prevalent structures in biochemicals, especially in the research of new pesticides. It is necessary to develop new insecticides with a different mode of action for the treatment of insecticide resistance problems. And, it is worth exploring the new active insecticidal lead structures with oxadiazole fragments. Methods: We used a “splicing up” method introducing the trifluoromethyl-oxadiazole moiety to 3- (ethylsulfonyl)-pyridine structure, and replaced the 6-position on the pyridine ring by different substituted amines. Then, a series of novel 3-(ethylsulfonyl)-pyridines containing trifluoromethyloxadiazole moiety were designed and synthesized. All these title compounds were confirmed by ¹H NMR, ¹³C NMR and ESI-MS. Results: The primary insecticidal activity results indicated that some of them (A1-A7, A10, A13- A14) exhibited good mortality against Mythimna separate at 500 mg/L (80-100%), and compounds A13 and A14 have moderate insecticidal activity against M. separate at 250 mg/L (50-55%). Discussion: The bioassay results showed that the designed compounds did not achieve excellent insecticidal activity by introducing the potential oxadiazole fragment. Therefore, it seems that the special physicochemical properties of the oxadiazole fragment should be considered in fragment splicing-based design. Conclusion: According to the bioassay studies, the results revealed that compounds A13 and A14 may provide useful information for further designing of efficient insecticides.