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首页> 外文期刊>RSC Advances >Theoretical investigations toward TMEDA-catalyzed [2+4] annulation of allenoate with 1-aza-1,3-diene: mechanism, regioselectivity, and role of the catalyst
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Theoretical investigations toward TMEDA-catalyzed [2+4] annulation of allenoate with 1-aza-1,3-diene: mechanism, regioselectivity, and role of the catalyst

机译：用1-AZA-1,3-二烯的含有1-AZA-1,3-二烯的TMEDA催化[2 + 4]附图的理论研究：机理，区域选择性，催化剂的作用

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摘要

A theoretical investigation on the mechanisms as well as regioselectivity of N,N,N',N'-tetramethylethane-1,2-diamine (TMEDA)-catalyzed [2 + 4] annulation of allenoate with 1-aza-1,3-diene leading to functionalized pyridines has been performed using density functional theory (DFT). Multiple possible reaction pathways (A-C) have been characterized, and the most favorable pathway C is remarkably different from the mechanism (i.e. pathway A) proposed in Angew. Chem., Int. Ed., 2013, 52, 8584. Generally, there are several steps in the entire catalytic cycle, including activation of allenoate by TMEDA, nucleophilic attack to 1-aza-1,3-diene, intramolecular cyclization, 1,3-hydrogen shift, hydrogen elimination by TMEDA and desulfonation. In pathway A, the 1,3-hydrogen shift is rate-limiting and takes place before the intramolecular cyclization. In the alternative pathway C, cyclization takes place before the 1,3-hydrogen shift, and it is found that TMEDA can function as a proton shuttle to mediate the 1,3-hydrogen shift and lower the energy barrier significantly. The results presented here demonstrate that the catalyst TMEDA can not only serve as a Lewis base to activate allenoate, but also as a Bronsted acid/base to mediate the 1,3-hydrogen shift process, thus accelerating the reaction. Furthermore, the observed regioselectivity is attributed to the more developed negative charge on the a carbon atom of activated allenoate, the stronger C-H center dot center dot center dot pi interaction, as well as hydrogen bond interaction between the two fragments. We believe that the present work is helpful to understand the multiple competing pathways for amine-catalyzed annulation reactions of allenoates with electrophiles, and provides valuable insights for predicting the regioselectivity for this kind of reaction.
机译：对N，N，N'，N'-四甲基乙烷-1,2-二胺（TMEDA）的机制的理论研究以及1-AZA-1,3-催化[2 + 4]环催化[2 + 4]环节使用密度泛函理论（DFT）进行导致官能化吡啶的二烯。已经表征了多种可能的反应途径（A-C），最有利的途径C与Angew中提出的机制（即通路A）显着不同。化学。，int。 ED。，2013,52,8584。一般来说，整个催化循环中有几个步骤，包括通过TMEDA激活甲酸酯，亲核发作至1-AZA-1,3-二烯，分子内环化，1,3-氢转移，通过纹理和脱硫消除氢气。在途径A中，1,3-氢转移是速率限制，并在分子内环化之前发生。在替代途径C中，在1,3-氢转移之前进行环化，发现TMEDA可以用作质子梭子，以介导1,3-氢转移并显着降低能量屏障。本文介绍的结果表明，催化剂TMEDA不仅可以用作活化甲酸盐的路易斯碱，还可以作为介导1,3-氢变换过程的伪造酸/碱，从而加速反应。此外，观察到的区域选择性归因于活化血烯酸碳的碳原子上的负电荷较强，C-H中心点中心点中心点PI相互作用以及两种片段之间的氢键相互作用。我们认为，本作本作有助于了解胺催化含有电子药物的胺催化环状反应的多竞争性途径，并提供了预测这种反应的区域选择性的有价值的见解。

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  • 来源
    《RSC Advances》 |2016年第75期|共9页
  • 作者

    Qiao Yan; Yang Wanjing; Wei Donghui; Chang Junbiao;

  • 作者单位

    Zhengzhou Univ Sch Basic Med Sci Dept Pathophysiol Zhengzhou 450001 Henan Peoples R China;

    Zhengzhou Univ Sch Basic Med Sci Dept Pathophysiol Zhengzhou 450001 Henan Peoples R China;

    Zhengzhou Univ Coll Chem &

    Mol Engn Zhengzhou 450001 Henan Peoples R China;

    Zhengzhou Univ Sch Basic Med Sci Dept Pathophysiol Zhengzhou 450001 Henan Peoples R China;

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  • 正文语种 eng
  • 中图分类 化学;
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