Discovery of Novel N-Pyridylpyrazole Thiazole Derivatives as Insecticide Leads

To develop effective insecticides against Lepidoptera pests, 25 novel N-pyridylpyrazole derivatives containing thiazole moiety were designed and synthesized based on the intermediate derivatization method (IDM). The insecticidal activities of these target compounds against Plutella xylostella (P. xylostella), Spodoptera exigua (S. exigua), and Spodoptera frugiperda (S. frugiperda) were evaluated. Bioassays indicated that compound 7g-7j exhibited good insecticidal activities. Compound 7g showed especially excellent insecticidal activities against P. xylostella, S. exigua, and S. frugiperda with LC50 values of 5.32 mg/L, 6.75 mg/L, and 7.64 mg/L, respectively, which were adequate for that of commercial insecticide indoxacarb. A preliminary structure-activity relationship analysis showed that the insecticidal activities of thiazole amides were better than that of thiazole esters, and the amides with electron-withdrawing groups on the benzene ring were better than the ones with electron-donating groups. This work provides important information for designing novel N-pyridylpyrazole thiazole candidate compounds and suggests that the 7g is a promising insecticide lead for further studies.