Asymmetric Hydrovinylation of Vinylindoles. A Facile Route to Cyclopenta[<i>g</i>]indole Natural Products (+)-<i>cis</i>-Trikentrin A and (+)-<i>cis</i>-Trikentrin B
作者:Wang Liu、Hwan Jung Lim、T. V. RajanBabu
DOI:10.1021/ja3004733
日期:2012.3.28
Vinylindoles undergo Ni(II)-catalyzed asymmetric hydrovinylation under very mild conditions (-78 °C, 1 atm ethylene, 4 mol % catalyst) to give the corresponding 2-but-3-enyl derivatives in excellent yields and enantioselectivities. Hydroboration of the alkene and oxidation to an acid, followed by Friedel-Crafts annulation, gives an indole-annulated cyclopentanone that is a suitable precursor for the
乙烯基吲哚在非常温和的条件下(-78 °C,1 atm 乙烯,4 mol% 催化剂)进行 Ni(II) 催化的不对称加氢乙烯基化,以优异的产率和对映选择性得到相应的 2-but-3-enyl 衍生物。烯烃的硼氢化和氧化成酸,然后进行 Friedel-Crafts 环化,得到吲哚环化的环戊酮,它是合成顺式三链酮和所有已知的草药的合适前体。例如,来自 4-乙基-7-乙烯基吲哚的环戊酮通过四步(Wittig 反应、烯烃异构化、非对映选择性氢化和氮脱保护)转化为 (+)-cis-trikentin A。先前从 (S)-(-)-苹果酸合成该分子涉及 20 多个步骤和非对映异构中间体的制备型 HPLC 分离。