Synthesis, Nematicidal Evaluation, and 3D-QSAR Analysis of Novel 1,3,4-Oxadiazole-Cinnamic Acid Hybrids

A series of novel 1,3,4-oxadiazole-cinnamic acid hybrids were synthesized. The bioassays results indicated that compounds 1, 2, 7, and 8 showed excellent nematicidal activities against Tylenchulus semipenetrans with LC_50,48h values of 9.7 ± 1.6, 15.6 ± 2.8, 8.0 ± 0.5, and 19.8 ± 2.9 mg/L, respectively, which were higher than those of avermectin (32.6 ± 4.5 mg/L) and fosthiazate (67.8 ± 1.7 mg/L). Low-toxicity compound 26, with excellent nematicidal activity in vitro (LC_50,48h = 8.2 ± 1.2 mg/L), was designed on the basis of the predictive CoMFA ( q² = 0.795, r² = 0.921) and CoMSIA ( q² = 0.762, r² = 0.912) models. The control effect of compound 26 was 69.8% at an effective dose of 1.0 g per plant in a field experiment, which was superior to that of fosthiazate (67.2%). This work indicated that 1,3,4-oxadiazole-cinnamic acid hybrids may be used as potential nematicides.