Design, synthesis, and nematicidal and fungicidal activity of 8-chloro-6-(trifluoromethyl) imidazo 1,2-a pyridine derivatives

In order to find new imidazo 1,2-a pyridine derivatives with excellent activity, using 2-amino-3-chloro-5-(trifluoromethyl) pyridine as the starting material, 17 new imidazo 1,2-a pyridine derivatives, which belong to two series, were designed and synthesized via the active substructure splicing strategy in this study, including 12 aminopyridine derivatives (1-12) and 5 sulfohydrazide derivatives (13-17), followed by the determination of their nematicidal and fungicidal activities. The structures of all the target compounds were confirmed by ¹H NMR, ¹³C NMR and HRMS. The in vitro nematicidal activity of target compounds was determined, and the results revealed a certain level of toxicity to Caenorhabditis elegans and Bursaphelenchus xylophilus. The LC₅₀ values of compounds 13, 15, 16 and 17 against C. elegans were 41.04, 7.64, 36.33 and 34.17 mg/L, respectively, which were better than that of fosthiazate (63.69 mg/L). The pot assay results for controlling Meloidogyne incognita showed thatthat compounds 15 and 16 achieved control efficacies of 66.11% and 70.00% (at a concentration of 50 mg/L), 58.33% and 66.67% (at a concentration of 100 mg/L), respectively. Both compounds outperformed the reference agent fluopyram, which achieved efficacies of 43.33% and 63.33%. The results of in vitro fungicidal activity showed that the EC₅₀ value of compound 8 against Gaeumannomyces graminis was 2.44 mg/L, which was significantly better than that of fluopyram (144.98 mg/L). The target compounds of sulfonyl hydrazide derivatives synthesized in this study showed certain nematicidal and fungicidal activity, which can provide research ideas for the design and modification of 8-chloro-6- (trifluoromethyl) imidazo 1,2-a pyridine derivatives.