Novel heptafluoroisopropyl N-phenylpyrazole aryl amides containing cyanoalkyl groups: Design, synthesis, insecticidal activity, docking studies and theoretical calculations

Abstract

To discover and develop new insecticides of the phenylpyrazole class, a series of heptafluoroisopropyl N-phenylpyrazole aryl amide compounds bearing cyanoalkyl groups were synthesized based on the lead compound nicofluprole. Their structures were established by HRMS, 1H NMR and 13C NMR. Bioassay results indicated that several of these compounds exhibited remarkable acaricidal and insecticidal activities. The LC50 values for compounds A1, A2 and A5 against Tetranychus cinnabarinus (T. cinnabarinus) were 1.7–4.2 times lower than that of nicofluprole (3.124 mg/L). Compounds A1, A2, A4 and A7 against Myzus persicae (M. persicae) had LC50 values of 0.261, 1.292, 0.589 and 1.133 mg/L respectively, exceeding that of nicofluprole (LC50 = 4.200 mg/L). Some compounds also demonstrated good insecticidal activity against Plutella xylostella (P. xylostella). For example, compounds A1–A4, A6, and A7 had a mortality rate of 100 % at a low concentration of 1.25 mg/L, which was comparable to nicofluprole (93.3%). Compound A1 exhibited insecticidal activity against Chilo suppressalis (C. suppressalis) with an LC50 value of 2.271 mg/L, which was superior to both nicofluprole (6.021 mg/L) and the positive control broflanilide (6.895 mg/L). Taking compound A5 as a representative, we tested the insecticidal activity against Aphis fabae (A. fabae), Aphis gossypii Glover (A. gossypii Glover), Nilaparvata lugens (N. lugens) and Laodelphax striatellus (L. striatellus) at 10 mg/L, and our results revealed that compound A5 exhibited broad-spectrum insecticidal activity. Molecular docking studies suggested that A1 had a lower binding energy of −7.764 kcal/mol with the P. xylostella gamma-aminobutyric acid receptors (GABAR). Density functional theory calculations (DFT) provided insights into the design of new compounds. This research suggested that the novel phenylpyrazoles featuring cyanoalkyl moieties in this work hold potential as novel insecticides for further research and development.