Synthesis, insecticidal activity, and structure-activity relationship (SAR) of anthranilic diamides analogs containing oxadiazole rings

A series of anthranilic diamides analogs (3-11, 16-24) containing 1,2,4- or 1,3,4-oxadiazole rings were synthesized and characterized by ¹H NMR, MS and elemental analyses. The structure of 3-bromo-N-(2-(3-(4-bromophenyl)-1, 2,4-oxadiazol-5-yl)-4-chloro-6-methylphenyl)-1-(3-chloropyridin-2-yl) -1H-pyrazole-5-carboxamide (18, CCDC-924454) was determined by X-ray diffraction crystallography. The insecticidal activities against Plutella xylostella and Spodoptera exigua were evaluated. The results showed that most of title compounds displayed good larvicidal activities against P. xylostella, especially compound 3-bromo-N-(4-chloro-2-methyl-6-(5-(methylthio)-1,3,4-oxadiazol-2-yl) phenyl)-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carboxamide (6), which displayed 71.43% activity against P. xylostella at 0.4 μg mL^-1 and 33.33% against S. exigua at 1 μg mL^-1. The structure-activity relationship showed that compounds decorated with a 1,3,4-oxadiazole were more potent than compounds decorated with a 1,2,4-oxadiazole, and different substituents attached to the oxadiazole ring also affected the insecticidal activity. This work provides some hints for further structure modification and the enhancement of insecticidal activity.