Design, Synthesis, and Biological Activities of Novel Phenylpyrazole Derivatives Containing a Trifluoromethylselenyl Moiety

Phenylpyrazole insecticides are widely used for crop protection and public sanitation by blocking gamma-aminobutyric acid (GABA)-gated chloride channels and glutamate-gated chloride (GluCl) channels. Herein, 36 novel phenylpyrazole derivatives containing a trifluoromethylselenyl moiety were designed and synthesized based on the strategy of introducing a selenium element. All derivative structures were characterized by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). The insecticidal activity results indicated that some derivatives had good insecticidal activities against Aedes albopictus (A. albopictus) and Plutella xylostella (P. xylostella). The larvicidal activity against mosquitos of compounds 5, 5a, 5k, and 5l at 0.5 mg/L was 60–80%. At a concentration of 500 mg/L, compounds 5, 5a, 5h, 5k, 5l, 5r, 6, 6j, 6k, and 7 showed a 70–100% mortality against P. xylostella. Among them, derivatives 5 and 6 had a better insecticidal effect with mortality rates of 87 and 93% at 50 mg/L, respectively. It was summarized that the different binding poses of fipronil and compounds 5 and 6 in the Musca domestica (M. domestica) GABARs might lead to the disparity in bioactivity from docking studies. Toxicity tests on zebrafish suggested that compound 6 may be slightly less toxic to the embryos than fipronil on hatching rate.