Design, Synthesis, Crystal Structures, and Insecticidal Activities of Eight-Membered Azabridge Neonicotinoid Analogues

Three series of novel azabridge neonicotinoid analogues were designed and synthesized, which were constructed by starting material A, glutaraldehyde, and primary amine hydrochlorides (aliphatic amines, phenylhydrazines, and anilines). Most of the eight-membered azabridge compounds presented higher insecticidal activities than oxabridged compound B against cowpea aphid (Aphis craccivora) and brown planthopper (Nilaparvata lugens). Compared with imidacloprid, some azabridged compounds exhibited excellent insecticidal activity against brown planthopper. The crystal structures and bioassay indicated that changing bridge atoms from O to N could lead to entirely different conformations, which might be the important influential factor of the bioactivities.