Synthesis and fungicidal activity of N-phenylacetamide derivatives containing 1,2,4-triazole

To discover compounds with better fungicidal activity, a series of N-phenylacetamide derivatives (6a-6o) containing 1,2,4-triazoles were designed and synthesized by combining substituted N-phenylacetamide with 1-(2,4-difluorophenyl)-2-(1H-1,2,4-triazol-1-yl)-ethanol using an ether bridge. Their structures were confirmed by ¹H NMR, ¹³C NMR, and HRMS analyses. The results of indoor fungicidal activity determination using the mycelial growth rate method showed that compound 6j had an EC₅₀ value of 0.15 mg/L for Bipolaris maydis, with indoor toxicity comparable to that of the control agent diniconazole (0.12 mg/L). The EC₅₀ value of compound 6a for Rhizoctonia solani was 6.96 mg/L, and its indoor toxicity is lower than that of the control agent diniconazole (1.88 mg/L). However, the potted results showed that at concentrations of 200 and 100 mg/L, the protective efficacy of compound 6a against rice sheath blight was 76.65% and 43.92%, respectively, which were higher than those of diniconazole (68.03% and 42.02%). The curative efficacy was 78.90% and 45.05%, respectively, which were higher than those of diniconazole (75.56% and 42.34%). The synthesized target compounds in this study have certain fungicidal activities, thereby enriching the structural types of triazole fungicides.