Synthesis and fungicidal activities of 1-2-benzyloxy-2-(2,4-difluorophenyl) ethyl-1H-1,2,4-triazole derivatives

Using antifungal medication econazole as the lead compound, a series of 1-2-benzyloxy-2-(2,4-difluorophenyl) ethyl-1H-1,2,4-triazole derivatives were designed, synthesized, and characterized by ¹H NMR, ¹³C NMR and HRMS. The in vitro fungicidal activities of those compounds against 7 plant pathogenic fungi were evaluated to discover effective compounds preliminarily. The efficiencies of the most effective compounds were further tested against rice sheath blight and wheat stripe rust in greenhouse and field. Furthermore, the inhibitory effect on the ergosterol biosynthesis of R. solani also were determined. Most of the target compounds exhibited good fungicidal activities against the tested plant pathogenic fungi in vitro, especially against Rhizoctonia solani and Alternaria solani. By measuring their EC₅₀ values, it was found that the EC₅₀ values of the tested compounds against R. solani were less than 3 μmol/L, which were significantly higher than those of difenoconazole and econazole. The EC₅₀ values of 4a , 4b , 4c , 4g , 4i and 4l against A. solani were all lower than 10 μmol/L. Compounds 4b and 4i showed higher than 70% control efficiencies against wheat stripe rust at 250 μmol/L in greenhouse. And the control efficiency of compound 4b against wheat stripe rust was 81.93% at 240 g a.i./hm² in field. In addition, compounds 4b and 4i were found to be effective in inhibiting ergosterol biosynthesis of R. solani with the inhibition rate of around 80% at the concentration of 100 μmol/L.