Synthesis And Bioactivity Of Neonicotinoid Analogues

As the milestone of the history of insecticides, neonicotinoid insecticides, derived from natural nicotine and shared the same action site as nicotine:nicotinic acetylcholine receptors (nAChR), played an important role in crop protection. Now the development of novel nicotinoid insecticides has been the focus of intense research today because of the resistance to neonicotinoids in some regions. In this thesis five series of novel structure neonicotinoid analogues were designed and synthesized with vinylnitro (iminonitro) neonicotinoid as lead compound. The structure and bioactivity relationships were also studied for seek of lead nicotinoid insecticides.1. Twenty unsaturated nicotinoid aldoxime compounds were designed and conveniently synthesized by reduction of the corresponding vinylnitro compounds with SnCl2-2H2O. Some evidences from a brief investigation suggest that these aldoximes be formed by reduction of the aci form of nitro, not the usually nitro form. X-ray crystallography analysis reveals that hydroxyl is arranged in trans configuration. Some compounds exhibited diversity of bioactivity with good herbicidal activity, moderate insecticidal activity and weak fungicidal activity.2. Five trans-nicotinoid aldoxime ether compounds were designed and synthesized with the nicotinoid aldoximes as materials. In addition twelve nicotinoid imidazolyl esters were designed and easily synthesized by internal elimination-rearrangement reaction of the corresponding aldoxime esters with the situ acid catalysis. Some compounds exhibited diversity of bioactivity with moderate herbicidal and insecticidal activity.3. With vinylnitro neonicotinoids as material, thirty-seven novel neonicotinoids, in which nitro were fixed in cis-configuration by bicycle structure or bulky conjugated system, were designed and synthesized. All the neonicotinoids exhibited excellent insecticidal activities against wiggler and some of them exhibited moderate activities against pea aphids. Compared to nitro-and chloride-containing compounds, fluorine-containing compounds were of higher insecticidal activity.4. With vinylnitro neonicotinoid as lead compound, fourteen vinylnitro-cyano neonicotinoid analogues were designed and synthesized. X-ray crystallography analysis reveals that nitro is arranged in trans configuration. One of the neonicotinoid analogues exhibited moderate activity against pea aphids. 5. According to theπ-πstacking mode of action of neonicotinoids, thirty-one neonicotinoid analogues with extended conjugated system were designed and synthesized. Further with them as ligands, twenty-four BF2 nicotinoid complexes were designed and synthesized by complexing with BF2. The preliminary bioassay indicated that the BF2 complexes exhibited higher insecticidal and fungicidal activities than their corresponding ligands.