Design, synthesis and acaricidal/insecticidal activities of etoxazole analogues

Based on the structure-activity relationship of etoxazole analogues and benzoylphenylureas, a series of 2-(2,6-difluorophenyl)-4-(4-substitutedphenyl)-1,3-oxazolines 4a-y were designed and synthesized. It was found that most of these compounds showed excellent acaricidal activities. They gave above 85% mortality at a concentration of 2.5 mg L-1, both for the eggs and larvae of spider mites. Some compounds also showed excellent insecticidal activities. The position and type of the substituents on the 4-phenyl of 2,4-diphenyl-1,3-oxazoline have a great influence on the activities. 2-(2,6-Difluorophenyl)-4-(2-Cl-4-(4-Cl-phenoxy)phenyl)-1,3-oxazoline (4r) exhibited 100% acaricidal mortality at 2.5 mg L-1, with 65% and 93% mortality against beet armyworm and diamondback moth, respectively, at 12.5 mg L-1, which is almost the same level as etoxazole. The newly found structure-activity relationship may also benefit further acaricide/insecticide development.