Background In recent years, carboxamide fungicides, targeting succinate dehydrogenase (SDH), have shown highly efficient and broad spectrum fungicidal activity. Structure–activity relationship (SAR) results for these commercial fungicides show that the carboxamide group was a key active group. This is useful information for the discovery of new pyrazole carboxamide derivatives with fungicidal activity. Results Twenty‐seven novel pyrazole carboxamides were designed and synthesized. Their fungicidal activities against Gibberella zeae, Phytophthora infestans, Phytophthora capsici, Rhizoctonia solani, Alternaria solani, Botrytis cinerea, Fusarium oxysporum, Cercospora arachidicola, Sclerotinia sclerotiorum and Physalospora piricola were tested; derivatives possessed excellent inhibitory at 50 mg L−1 in particular. Furthermore, some pyrazole carboxamides exhibited remarkably high activities against Sclerotinia sclerotiorum in vitro with EC50 values of 2.04 to 15.2 μg mL−1. In addition, some compounds also exhibited high activities against Physalospora piricola, Cercospora arachidicola and Phytophthora capsici. Inhibition activities against SDH proved that the designed analogues were effective at the enzyme level. The SAR of these pyrazole carboxamides was studied by using the docking method. Conclusion It is possible that pyrazole carboxamides, which exhibit good activity against Sclerotinia sclerotiorum, can be further optimized as a lead compounds of carboxamide fungicides. © 2019 Society of Chemical Industry

It is possible that, with further structure modification, 1,2,4-triazolo[4,3-a]pyridine derivatives, which possess good herbicidal activities, may become novel lead compounds for the development of herbicides against dicotyledonous weeds.

BACKGROUND 4‐Hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27) has been a good target for herbicide discovery. In order to discover novel HPPD herbicides, a series of pyrazole aromatic ketone analogs were designed and synthesized. RESULTS The 25 pyrazole aromatic ketone analogs synthesized were tested for herbicidal activity and compounds A1, A3, A4, A17, A20 and A25 displayed excellent herbicidal activity against Chenopodium serotinum, Stellaria media and Brassica juncea at 37.5 g ha−1. In addition, compounds A1, A5, A9, A10, A16, A17, A20 and A25 exhibited good crop selectivity for wheat, maize and rice at 150 g ha−1. Inhibition activities against AtHPPD proved the compounds were HPPD inhibitors. The structure–activity relationship of these pyrazole aromatic ketone analogs was studied using molecular docking. CONCLUSION These pyrazole aromatic ketone derivatives could be used as lead structures for development of HPPD herbicides against dicotyledonous weeds with further structure modification. © 2019 Society of Chemical Industry

A practical synthetic route for pyrimidine derivatives is presented. This study suggests that these pyrimidine derivatives exhibit some activity against the yellow fever mosquito and, with further structure modification, could be novel lead compounds for the development of insecticides against mosquitoes. © 2016 Society of Chemical Industry.

Natural products are a source of many novel compounds with biological activity for the discovery of new pesticides and pharmaceuticals. Quinoxaline is a fused N-heterocycle in many natural products and synthetic compounds, and seven novel quinoxaline derivatives were designed and synthesized via three steps. Pesticidal activities of title quinoxaline derivatives were bioassayed. Most of these compounds had herbicidal, fungicidal, and insecticidal activities. The compounds 2-(6-methoxy-2-oxo-3phenylquinoxalin-1(2H)-yl)acetonitrile (3f) and 1-allyl-6-methoxy-3-phenylquinoxalin-2(1H)-one (3g) were the most active herbicides and fungicides. Mode-of-action studies indicated that 3f is a protoprophyrinogen oxidase-inhibiting herbicide. Compound 3f also possessed broad-spectrum fungicidal activity against the plant pathogen Colletotrichum species. Some of these compounds also had insecticidal activity. Molecular docking and DFT analysis can potentially be used to design more active compounds.