Stereocontrol in <i>N</i>-Directed Hydroboration: Synthesis of Amino Alcohols Related to the Piperidine Alkaloids
作者:Guoqiang Wang、Edwin Vedejs
DOI:10.1021/ol802781c
日期:2009.3.5
acid induces internal hydroboration with high regiocontrol, even with a terminal alkene (R = H). Good stereocontrol is possible for the N-benzyl substrates. Comparisons with acyclic model structures show that the source of regiocontrol with the terminal alkene is due to a steric effect of the axial piperidine C(3,5) hydrogens that destabilize the competing bridged bicyclic transition state.
用碘或三氟甲磺酸处理 2-(2'-链烯基)-哌啶硼烷可诱导具有高度区域控制的内部硼氢化反应,即使是末端烯烃 (R = H)。N-苄基底物可能具有良好的立体控制。与非环状模型结构的比较表明,末端烯烃区域控制的来源是由于轴向哌啶 C(3,5) 氢的空间效应,它破坏了竞争性桥接双环过渡态的稳定性。