Synthesis of N-Difluoromethyl Benzothiazole (or Benzoxazole) Selenones as Novel Inhibitors Against Phytopathogenic Fungi.

Azole selenoureas exhibit diverse biological functions. However, the synthesis and biological activity of benzothiazole and benzoxazole selenones remained unexplored. Herein, we report the base-catalyzed synthesis of N-difluoromethyl benzothiazole (or benzoxazole) selenone derivatives, which demonstrated significant antifungal efficacy against Rhizoctonia solani, Phytophthora infestans, Botrytis cinerea, and Fusarium oxysporum. Compound 3b exhibited exceptional antifungal activity against R. solani, with an EC50 of 2.10 mg/L. Moreover, it substantially inhibited sclerotia germination (81.5% at 9 mg/L) and formation (79.3% at 9 mg/L), surpassing octhilinone. The protective effect on detached rice leaves and rice seedlings was found to be 43.4% and 85.2% at 100 mg/L, respectively, and 64.4% and 89.4% at 200 mg/L. These findings suggest that benzothiazole and benzoxazole selenones represent promising lead compounds for sustainable plant disease management.