Design, synthesis and nematocidal activity of novel 1,2,4-oxadiazole derivatives with a 1,3,4-thiadiazole amide moiety

A series of novel 1,2,4-oxadiazole derivatives containing 1,3,4-thiadiazole amide group was synthesized and their nematocidal activities were evaluated. The results indicated that compounds 4-methoxy-N-(5-(((3-(p-tolyl)-1,2,4-oxadiazol-5-yl)methyl)thio)-1,3,4-thiadiazol-2-yl)benzamide 4i and N-(5-(((3-(4-chlorophenyl)-1,2,4-oxadiazol-5-yl)methyl)thio)-1,3,4-thiadiazol-2-yl)benzamilde 4p showed good nematocidal activity against Bursaphelenchus xylophilus. The corrected mortality of compounds 4i and 4p at 200 mg/L was 57.1% and 60.1%, respectively, which are much better than 13.5% of the commercial seed coating agent Tioxazafen. Compounds 4i and 4p dramatically decreased the head swinging, body fluctuation, and body bending frequency of B. xylophilus after 12 h of treatment. Moreover, they inhibited the respiration, decreased the oxygen consumption, and caused fluid leakage of B. xylophilus. In addition, compounds 4i and 4p have good druggability properties similar to those of Tioxazafen. The present work indicates that compounds 4i or 4p could be promising lead compounds for further development of nematicides.