Novel Isoxazoline Amide Derivatives with Diaryl Sulfide Fragment as Potential Insecticides

Isoxazoline insecticides exhibit broad-spectrum and highly effective insecticidal activity by acting on insect GABA receptors. Existing insecticides have high toxicity towards non-target organisms, such as bees, limiting their practical use. This study utilized an active group splicing approach to create 41 new isoxazoline compounds (FSC1-FSC41). Bioassays indicated that most compounds displayed potent insecticidal activity against Plutella xylostella and Spodoptera litura. Particularly, FSC36 exhibited the highest activity, with LC50 values of 0.84 mg/L and 1.52 mg/L against P. xylostella and S. litura, surpassing the commercial compound fluxametamide (1.53 mg/L and 2.05 mg/L). Acute oral toxicity tests on honey bees showed FSC36 to have an LD50 of 2.77 mg/L, lower than fluralaner (0.19 mg/L) and fluxametamide (0.92 mg/L), overcoming the "high efficacy-high toxicity" challenge. This research offers a foundation for developing novel isoxazoline insecticides that are highly effective and environmentally friendly.