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

Abstract

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 <i>Aedes albopictus</i> (<i>A. albopictus</i>) and <i>Plutella xylostella</i> (<i>P. xylostella</i>). The larvicidal activity against mosquitos of compounds <b>5</b>, <b>5a</b>, <b>5k</b>, and <b>5l</b> at 0.5 mg/L was 60-80%. At a concentration of 500 mg/L, compounds <b>5</b>, <b>5a</b>, <b>5h</b>, <b>5k</b>, <b>5l</b>, <b>5r</b>, <b>6</b>, <b>6j</b>, <b>6k</b>, and <b>7</b> showed a 70-100% mortality against <i>P. xylostella</i>. Among them, derivatives <b>5</b> and <b>6</b> 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 <b>5</b> and <b>6</b> in the <i>Musca domestica</i> (<i>M. domestica</i>) GABARs might lead to the disparity in bioactivity from docking studies. Toxicity tests on zebrafish suggested that compound <b>6</b> may be slightly less toxic to the embryos than fipronil on hatching rate.