Design, Synthesis, and Acaricidal/Insecticidal Activities of Oxazoline Derivatives Containing a Sulfur Ether Moiety

On the basis of etoxazole, a series of novel 2-(2,6-difluorophenyl)-4-(4-substituted phenyl)-1,3-oxazolines containing a sulfur ether moiety were designed and synthesized via the key intermediate N-(1-(4-(bromomethyl)­phenyl)-2-chloroethyl)-2,6-difluorobenzamide. The bioassay results showed that most of these designed target compounds exhibited excellent acaricidal activity against both the eggs and larvae of Tetranychus cinnabarinus, especially the eggs. Among compounds with high activity against the eggs of mites, the LC₅₀ values of 2, 11, 17, and 19 were 0.0003, 0.0002, 0.0005, and 0.0008 mg L^–1, respectively, much lower than that of etoxazole (0.0089 mg L^–1). Compound 2 was chosen to evaluate the acaricidal activity in the field, and the results displayed that at a concentration of 22 mg kg^–1, 2 had a much better control effect than etoxazole against both T. cinnabarinus and P. latus on eggplant. Some compounds also showed good insecticidal activities against oriental armyworm and mosquito. On the basis of our research, the newly found structure–activity relationship may guide the development of new acaricides/pesticides that are required in the agriculture market.