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Intercepting fleeting cyclic allenes with asymmetric nickel catalysis

机译：用不对称镍催化拦截短循环杂环

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摘要

Asymmetric nickel catalysis is used to intercept transient cyclic allene intermediates to achieve stereocontrol.Strained cyclic organic molecules, such as arynes, cyclic alkynes and cyclic allenes, have intrigued chemists for more than a century with their unusual structures and high chemical reactivity(1). The considerable ring strain (30-50 kilocalories per mole)(2,3)that characterizes these transient intermediates imparts high reactivity in many reactions, including cycloadditions and nucleophilic trappings, often generating structurally complex products(4). Although strategies to control absolute stereochemistry in these reactions have been reported using stoichiometric chiral reagents(5,6), catalytic asymmetric variants to generate enantioenriched products have remained difficult to achieve. Here we report the interception of racemic cyclic allene intermediates in a catalytic asymmetric reaction and provide evidence for two distinct mechanisms that control absolute stereochemistry in such transformations: kinetic differentiation of allene enantiomers and desymmetrization of intermediate pi-allylnickel complexes. Computational studies implicate a catalytic mechanism involving initial kinetic differentiation of the cyclic allene enantiomers through stereoselective olefin insertion, loss of the resultant stereochemical information, and subsequent introduction of absolute stereochemistry through desymmetrization of an intermediate pi-allylnickel complex. These results reveal reactivity that is available to cyclic allenes beyond the traditional cycloadditions and nucleophilic trappings previously reported, thus expanding the types of product accessible from this class of intermediates. Additionally, our computational studies suggest two potential strategies for stereocontrol in reactions of cyclic allenes. Combined, these results lay the foundation for the development of catalytic asymmetric reactions involving these classically avoided strained intermediates.
机译：不对称镍催化用于拦截瞬时环状联烯中间体，以实现立体循环有机分子，例如雄激素，环状炔烃和环丙烯，具有兴趣的化学家，具有不寻常的结构和高化学反应性（1）。具有可观的环形菌株（每摩尔30-50千千次）（2,3），这些瞬态中间体表征在许多反应中，包括环加成和亲核包装，通常在结构上复杂的产品（4）中赋予高反应性。尽管使用化学计量手性试剂（5,6），但是据报道了控制这些反应中绝对立体化学的策略，但是产生对灭节产物的催化不对称变体难以实现。在这里，我们报告催化不对称反应中的外消旋环苯苯甲烯中间体的截取，并提供了两个不同机制的证据，该方法控制了这种转化中的绝对立体化学：苯丙烯对映体的动力学分化和中间Pi-烯丙基尼克尔络合物的脱差异化。计算研究涉及涉及通过立体选择性烯烃插入，丧失所得立体化学信息的初始动力学分化的催化机制，并通过中间Pi-烯丙基尼克尔络合物的去对称引入绝对立体化学。这些结果揭示了在传统环加成和先前报道的传统环加成和亲核包装之外的循环杂物可用的反应性，从而扩展了这类中间体可访问的产品类型。此外，我们的计算研究表明，在环丙烯的反应中的立体控制两种潜在策略。合并，这些结果为涉及这些典型避免的紧张中间体的催化不对称反应的发展奠定了基础。

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  • 来源
    《Nature》 |2020年第7828期|242-247|共6页
  • 作者

    Yamano Michael M.; Kelleghan Andrew V.; Shao Qianzhen; Giroud Maude; Simmons Bryan J.; Li Bo; Chen Shuming; Houk K. N.; Garg Neil K.;

  • 作者单位

    Univ Calif Los Angeles Dept Chem & Biochem 405 Hilgard Ave Los Angeles CA 90024 USA;

    Univ Calif Los Angeles Dept Chem & Biochem 405 Hilgard Ave Los Angeles CA 90024 USA;

    Univ Calif Los Angeles Dept Chem & Biochem 405 Hilgard Ave Los Angeles CA 90024 USA;

    Univ Calif Los Angeles Dept Chem & Biochem 405 Hilgard Ave Los Angeles CA 90024 USA;

    Univ Calif Los Angeles Dept Chem & Biochem 405 Hilgard Ave Los Angeles CA 90024 USA;

    Univ Calif Los Angeles Dept Chem & Biochem 405 Hilgard Ave Los Angeles CA 90024 USA;

    Univ Calif Los Angeles Dept Chem & Biochem 405 Hilgard Ave Los Angeles CA 90024 USA;

    Univ Calif Los Angeles Dept Chem & Biochem 405 Hilgard Ave Los Angeles CA 90024 USA;

    Univ Calif Los Angeles Dept Chem & Biochem 405 Hilgard Ave Los Angeles CA 90024 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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