Synthesis, Acaricidal Activity, and Structure–Activity Relationships of Pyrazolyl Acrylonitrile Derivatives

A series of novel pyrazolyl acrylonitrile derivatives was designed, targeting Tetranychus cinnabarinus, and synthesized. Their structures were identified by combination of 1 H NMR, 13 C NMR, and MS spectra. The structures of compounds 18 and 19 were further confirmed by X-ray diffraction. Extensive greenhouse bioassays indicated that compound 19 exhibits excellent acaricidal activity against all developmental stages of T. cinnabarinus, which is better than the commercialized compounds cyenopyrafen and spirodiclofen. It was shown that the acute toxicity of compounds 19 to mammals is quite low. The structure–activity relationships are also discussed.