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

To discover new nematicidal and fungicidal compounds with high activity, 1,3,4-thiadiazole and 1,2,4-triazole structures were introduced into imidazo 1,2-a pyridine by using the principle of active substructure splice, with 2-amino-3-chloro-5-trifluoromethyl pyridine as raw material. Twenty-four unreported 8-chloro-6-(trifluoromethyl) imidazo 1,2-a pyridine thiadiazole/triazole derivatives were designed and synthesized, and their structures were confirmed by ¹H NMR, ¹³C NMR and HRMS. The results indicated that all the compounds showed different levels of toxic activity against Caenorhabditis elegans when the concentration was 100 mg/L. After 48 h, the corrected mortality rates of compounds 9e, 9f, 9i, 9k, 10d and 10h were 94.10%, 84.08%, 93.74%, 91.82%, 92.61% and 88.90%, respectively, which were better than the control agent fosthiazate (60.28%), but lower than fluopyram (100%). The toxicity of the target compound to Bursaphelenchus xylophilus was not ideal. At a concentration of 100 mg/L, only compounds 9c and 9l exhibited moderate nematicidal activity, with corrected mortality rates of 50.27% and 49.43%, respectively, which were lower than the control agents fosthiazate (52.04%) and fluopyram (96.50%). The results of the fungicidal activity assay by mycelium growth rate method showed that EC₅₀ values of compounds 9a and 9c were 57.35 and 34.75 mg/L, respectively, which were better than the control agent fluopyram (122.37 mg/L), but lower than carbendazim (0.48 mg/L). The imidazo 1,2-a pyridine thiadiazole/triazole compounds synthesized in this study have certain nematoidal and fungicidal activities, and provide a reference for further exploration of imidazo 1,2-a pyridine compounds.