Synthesis, biological activity and toxicity to zebrafish of benzamides substituted with pyrazole-linked 1,2,4-oxadiazole.

To find pesticidal lead compounds with high activity, a series of novel benzamides substituted with pyrazole-linked 1,2,4-oxadiazole was designed and synthesized by using the splicing principle of active substructures. The chemical structures of the target compounds were confirmed by 1 H NMR, 13 C NMR and HRMS. The preliminary bioassay showed that most compounds displayed good larvicidal activities against mosquito larvae at 10 mg L -1 . In particular, compound 12g exhibited obvious activity; its lethal rate reached up to 100% (at 5 mg L -1 ) and 55% (at only 2 mg L -1 ). Furthermore, compound 12f (70.6%) and 12h (100%) showed good fungicidal activities against Pyricularia oryzae , with EC 50 values of 8.28 and 5.49 μg mL -1 , respectively, which were superior to that of the control drug bixafen (9.15 μg mL -1 ). Finally, the LC 50 of compound 12h to zebrafish embryo was 0.39 mg L -1 , so it was classified as a high-toxic compound. Thus, this compound may be used as a potential lead compound for further structural optimisation to develop new compounds with high activity and low toxicity.