Synthesis and acaricidal activity of novel pyrazole acrylonitrile derivatives

In order to obtain acaricides of pyrazole acrylonitrile with better acaricidal activity for mitecontrol, seventeen novel ester derivatives were synthesized via four steps of Blanc chloromethylation reaction, dehalogenation reaction, condensation reaction and esterification reaction using ethyl 1,3-dimethyl-1H-pyrazole-5-carboxylate as the starting material. Furthermore, their acaricidal activity against Tetranychus cinnabarinus was assessed by immersion test, and the mortality rate and lethal mid-range concentration LC₅₀ were calculated. The results show that the target compounds display excellent acaricidal activity against T. cinnabarinus, and compared with the commercial pesticide cyenopyrafen (LC₅₀ = 0.61 mg/L), compounds 5q and 5k possess significantly higher acaricidal activity against T. cinnabarinus with LC₅₀ values of 0.17 and 0.22 mg/L, respectively.