Synthesis of Benzo-Fused 1-Azabicyclo[<i>m</i>.<i>n</i>.0]alkanes via the Schmidt Reaction: A Formal Synthesis of Gephyrotoxin
作者:William H. Pearson、Wen-kui Fang
DOI:10.1021/jo0011383
日期:2000.10.1
variety of substrates. Fortunately, these materials were easily made. Ultimately, the azido-alkene 81 bearing a 2-bromoethyl side-chain was useful for the Schmidt reaction, producing the known benzo-fused indolizidine 49, which had been transformed by Ito et al. into gephyrotoxin 4. The synthesis of 49 required nine steps (five purifications) from commercially available 4-methoxy-1-indanone 60 and proceeded
叠氮化物在分子内捕获苯并环丁基,苯并环戊基和苯并环己基碳正离子7会产生螺环氨基重氮离子8,其发生1,2-C-N重排而失去二氮,从而产生由任一芳基生成的苯并稠合的亚胺离子(9)或烷基(10)迁移至缺电子的氮原子。亚胺离子的还原提供了区域异构的苯并稠合的1-氮杂双环[mn0]烷烃,例如苯并吡咯烷,苯并吲哚并,苯并喹啉或全氢苯并[f]吡咯并[1,2-a]氮杂,有两个区域异构形式,即苯胺(例如,11 -14)和苄基胺(例如15-18),分别是芳基和烷基迁移的结果。通常,芳基迁移是优选的,尽管模型表明最低能量的氨基重氮离子是那些离开的二氮优先优先于迁移的烷基而不是芳基的重氮基离子。该方法的实用性通过生物碱gephyrotoxin 4的正式合成得以说明。观察到Schmidt反应的效率和区域选择性对阳离子前体结构的细微变化的依赖性,因此有必要探索各种底物。幸运的是,这些材料很容易制造。最终,带有2-溴乙