Design, synthesis and antifungal evaluation of novel pyrazole carboxamides with diarylamines scaffold as potent succinate dehydrogenase inhibitors

Sixteen novel pyrazole carboxamides with diarylamines scaffold were designed, synthesized and characterized in detail via H-1 NMR, C-13 NMR and ESI-HRMS. Preliminary bioassays showed that some of the target compounds exhibited good antifungal activity against Rhizoctonia solani, Fusarium oxysporum, Phytophthora infestans and Fusarium graminearum. Among them, compound 1c exhibited the highest antifungal activities against R. solani in vitro with EC50 value of 0.005 mg/L, superior to the commercially available fungicide fluxapyroxad (EC50 = 0.033 mg/L). And compound 1c (IC50 = 0.034 mg/L) showed higher inhibition abilities against succinate dehydrogenase than fluxapyroxad (IC50 = 0.037 mg/L). This study suggests that compound 1c could be regarded as a potential succinate dehydrogenase inhibitor.