Discovery of novel 1,5-diaryl-3-trifluoropyrazoles as antifungal pesticides for crop protection.

BACKGROUND

Plant diseases caused by phytopathogenic fungi continue to threaten global food security, driving the urgent need for discovery of antifungal agrochemicals with novel modes of action. The motif of 1,5-diaryl-3-trifluoropyrazole was found to be associated with potential antifungal effect and HNNK-5 was such an agrochemical being developed in our lab with moderate potency. This study took HNNK-5 as the parent compound for lead optimization to discovery novel fungicides.

RESULT: To further explore the antifungal potential of this class of compounds, a series of analogues of HNNK-5 was designed and prepared. Among them, compound 7 was identified as the most potent member with much improved activity over the lead compound. Compound 7 almost completely inhibited the growth of all the tested fungal pathogens at 50 μg/mL with an EC50 range of 6.2-11.5 μg/mL, multiple-fold less potent than the positive control azoxystrobin. Scanning electronic microscope (SEM) observation and fatty acid analysis showed that compound 7 treatment caused morphological changes and altered the amount of fatty acids of Fusarium oxysporum. Furthermore, compound 7 at higher application rates showed pronounced controlling effects against peanut root rot disease caused by Fusarium oxysporum in field study, similar to those of positive control azoxystrobin.

CONCLUSION

This study indicated that the characteristic structure of 1,5-diaryl-3-trifluoropyrazole could be employed as a potential skeleton for antifungal pesticides development and provided compound 7 as a promising pesticide candidate for further development. © 2025 Society of Chemical Industry.