Synthesis, insecticidal activities, and structure–activity relationships of 1,3,4-oxadiazole-ring-containing pyridylpyrazole-4-carboxamides as novel insecticides of the anthranilic diamide family

The preparation of novel anthranilic diamide derivatives is extremely important for agricultural pest control. In this study, pyridylpyrazole-4-carboxamides containing a 1,3,4-oxadiazole ring were designed and synthesized via the dehydration of aromatic hydrazine derivatives and formanilides in the presence of an alkali. The insecticidal activities of these new compounds against the diamondback moth (Plutella xylostella) were evaluated. N-(4-chloro-2-methyl-6-(5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)phenyl)-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-4-carboxamide (8h6) showed 67%, 50%, 34%, 20%, and 17% activity at concentrations of 100, 50, 10, 5, and 1 μg ml⁻¹, respectively. Density functional theory calculations showed that the introduction of the 1,3,4-oxadiazole ring significantly changed the electron distributions in both the highest occupied and lowest unoccupied molecular orbitals, resulting in these compounds having much larger energy gaps than the well-known insecticide chlorantraniliprole, which may account for their lower activity. The results of this study demonstrate that anthranilic diamides substituted with a 1,3,4-oxadiazole ring are effective insecticides that can be used for pest management.