Highly Efficient Synthesis and Acaricidal and Insecticidal Activities of Novel Oxazolines with N-Heterocyclic Substituents

Nitrogen heterocycles are found in numerous natural products, pharmaceuticals, and pesticides. Herein, we report the design and synthesis of a series of novel 2,4-diphenyl-1,3-oxazolines bearing various N-heterocyclic substituents via a 4-(4-(chloromethyl)phenyl)-2-(2,6-difluorophenyl)-4,5-dihydrooxazole intermediate generated by a modified Ritter reaction. Evaluation of the activities of the oxazolines against carmine spider mites (Tetranychus cinnabarinus) by means of a leaf-dipping method showed that most of the compounds exhibited good to excellent larvicidal and ovicidal activities. In particular, five compounds (one with a phthalimidyl group and four with a substituted indolyl group) have lower LC₅₀ values than the commercial acaricide etoxazole (0.088 mg/L against larvae and 0.128 mg/L against eggs). This work lays a foundation for the development of novel acaricides.