Enantioselective Synthesis of Allylboronates Bearing a Tertiary or Quaternary B-Substituted Stereogenic Carbon by NHC-Cu-Catalyzed Substitution Reactions
作者:Aikomari Guzman-Martinez、Amir H. Hoveyda
DOI:10.1021/ja104254d
日期:2010.8.11
Allylic substitutions that afford alpha-substituted allylboronates bearing B-substituted tertiary or quaternary carbon stereogenic centers are presented. C-B bond-forming reactions, catalyzed by chiral bidentate Cu-NHC complexes, are performed in the presence of commercially available bis(pinacolato)diboron. Transformations proceed in high yield (up to >98%) and site selectivity (>98% S(N)2'), and
提供带有 B 取代的叔或季碳立体中心的 α 取代的烯丙基硼酸酯的烯丙基取代。由手性双齿 Cu-NHC 配合物催化的 CB 键形成反应在市售的双(频哪醇)二硼存在下进行。转化以高产率(高达 >98%)和位点选择性(>98% S(N)2')以及高达 >99:1 的对映体比例进行。可以使用反式或顺式二取代的烯烃;烷基-(直链和支链)和芳基-三取代的烯丙基碳酸酯用作有效的底物。带有季碳中心的烯丙基硼酸酯在空气中是稳定的,可以很容易地通过硅胶色谱法纯化;相比之下,仲烯丙基硼酸酯不能以相同的方式纯化并且稳定性明显较差。