Design, synthesis and antifungal evaluation of novel indoline‐containing pyrazole‐4‐carboxamide derivatives as potential succinate dehydrogenase inhibitors

Abstract BACKGROUND Plant diseases caused by various pathogenic fungi significantly reduce productivity and threaten food safety. Chemical fungicides remain a cornerstone in the management of fungal infections afflicting crops. In search for more potent succinate dehydrogenase inhibitors (SDHIs) for crop protection, a series of novel indoline‐containing pyrazole‐4‐carboxamide derivatives were designed and synthesized. RESULTS The assay results indicated that the majority of compounds incorporating a benzyl group displayed remarkable antifungal efficacies. Notably, compound 6j emerged as a standout, exhibiting the highest potency against Rhizoctonia solani , with a half‐maximal effective concentration (EC 50 ) of 0.04 μg mL −1 , surpassing Boscalid (EC 50 = 0.40 μg mL −1 ) and Fluxapyroxad (EC 50 = 0.06 μg mL −1 ). Furthermore, compound 6i showed potent antifungal effects against Sclerotinia sclerotiorum and Valsa mali , with EC 50 values of 1.79 μg mL −1 and 3.54 μg mL −1 , respectively. In vivo tests confirmed that compound 6j effectively inhibited the growth of R. solani on rice leaves, while compound 6i suppressed S. sclerotiorum on oilseed rape and V. mali on apple fruits. Further antifungal mechanism studies revealed that compound 6j shared a similar mode of action with Fluxapyroxad. CONCLUSION These findings indicated that compounds 6j and 6i could serve as promising SDHI candidates for crop protection, warranting further investigation. © 2026 Society of Chemical Industry.