Synthesis and synergistic activity of N-phenyl-eight-membered oxabridged neonicotinoid analogues

Insecticide synergists are key components to improve insecticidal efficacy and reduce resistance. In this work, further derivation of the eight-membered oxabridged structure with specific synergistic effect was conducted, fifteen novel N-phenyl-eight-membered oxabridged neonicotinoid derivatives were designed and synthesized, the mortality of the target compounds combined with imidacloprid against Aphis craccivora was tested. The results indicated that most of the target compounds increased the toxicity of imidacloprid against A. craccivora at the concentration of 1 mg/L. The non-substituted compound 4a and 4-CF₃-substituted compound 4m exhibited the comparable synergistic effect, the synergism ratio was 3.44 and 3.58, respectively, which could be regarded as candidate compounds for further study.