Novel Acaricidal Silico-Containing Pyrazolyl Acrylonitrile Derivatives Identified through Rational Carbon-Silicon Bioisosteric Replacement Strategy

The identification of novel pyrazolyl acrylonitrile acaricides with improved properties is of great value for the control of phytophagous mites. A series of innovative silicon-containing pyrazolyl acrylonitriles were rationally designed by applying a bioisosteric carbon-silicon replacement strategy and prepared based on novel synthetic methodology. As a result of our research, we discovered compound A25 which possesses outstanding acaricidal activity. With an LC₅₀ value of 0.062 mg/L, compound A25 was found to be 2.3-fold and 1.9-fold more potent than the commercial acaricides cyenopyrafen and cyetpyrafen, respectively. Enzymatic inhibitory assay indicated that the active principle M1 of compound A25 possesses an IC₅₀ value of 2.32 μM against Tetranychus cinnabarinus SDH, which was about twofold superior compared to the active metabolites of cyenopyrafen (IC₅₀ = 4.72 μM). Molecular docking study showed that the active metabolites 2 and 3 and their corresponding silicon counterparts form H-bonds and cation−π interaction with the residues of Trp165, Tyr433, and Arg279.