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Ruthenium(II)-catalyzed [2+2] cycloadditions between bicyclic alkenes and alkynes: Scope and limitations.

机译：双环烯烃和炔烃之间的钌（II）催化的[2 + 2]环加成反应：范围和限制。

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摘要

This is an investigation of the scope and limitations of Cp*RuCl(COD) as a [2+2] cycloaddition catalyst. In particular, the ruthenium(II)-catalyzed [2+2] cycloadditions between strained bicyclic alkynes and functionalized alkynes were investigated. The development of this methodology has potential ramifications in natural product synthesis. Moreover, the development of a better understanding surrounding ruthenium(II)catalyzed [2+2] cycloadditions was required for the advancement of this synthetic tool.; Remote substituent studies have provided some valuable information towards the stereoelectronic properties of ruthenium(II)-catalyzed [2+2] cycloadditions between 2-substituted norborn-5-enes and numerous alkynes. We have demonstrated that the cycloaddition proceeds smoothly under favourable conditions (room temperature in most cases) affording only the exo stereoisomers in moderate to high yields (up to 96%). More importantly, low to excellent (up to 15:1) levels of regioselectivity were obtained with various remote substituents. These remote substituent studies have provided a better understanding for the mechanism of a ruthenium(II)-catalyzed [2+2] cycloaddition between an alkene and alkyne.; The reactivity of a wide range of substituted norbornadienes and norbornenes in ruthenium(II)-catalyzed [2+2] cycloadditions were explored. The cycloadditions were found to be highly stereo-, regio-, and chemoselective affording the cycloadducts in moderate to excellent yields (up to 98%). The observed chemoselectivity revealed that the cycloadditions occurred preferentially on the less-substituted double bond. The results from relative rate experiments indicate that electron-deficient alkenes react slower in ruthenium(II)-catalyzed [2+2] cycloadditions with alkynes.; Ruthenium(II)-catalyzed [2+2] cycloadditions of functionalized alkynes with norbornadiene have also been studied. The cycloadditions were found to be highly stereoselective, affording the exo stereoisomers as the only cycloadducts in poor to good yields (up to 91%). Cp*RuCl(COD) has been demonstrated to possess a high functional group tolerance among substituted acetylenes. Examples of compatible acetylenes include halogenated, carboxylic derivatives, and propargylic alcohol derivatives. Comparative rate findings imply that, generally speaking, electron poor alkynes accelerate ruthenium(II)-catalyzed [2+2] cycloadditions with norbornadiene. Moreover, we have also highlighted the steric limitations between the alkyne component and Cp*RuCI(COD).; Diastereoselective ruthenium(II)-catalyzed [2+2] cycloadditions between symmetrical bicyclic alkenes (norbornadiene and norbornene) and chiral propargylic ethers have also been examined. The cycloadditions afforded the cycloadducts as sole stereoisomers (exo stereochemistry) in moderate to good yields (up to 84%). Moderate levels of diastereoselectivities, up to 4:1, were observed with chiral propargylic ethers.
机译：这是对Cp * RuCl（COD）作为[2 + 2]环加成催化剂的范围和局限性的研究。特别是，研究了在双环炔烃和官能化炔烃之间钌（II）催化的[2 + 2]环加成反应。这种方法的发展对天然产物的合成有潜在的影响。此外，需要进一步了解钌（II）催化的[2 + 2]环加成反应，以开发这种合成工具。远程取代基研究为2-取代的降冰片烯-5-烯与大量炔烃之间钌（II）催化的[2 + 2]环加成反应的立体电子性质提供了一些有价值的信息。我们已经证明，环加成反应在有利的条件下（大多数情况下在室温下）可以顺利进行，仅提供中度至高产率（最高96％）的外向立体异构体。更重要的是，使用各种远程取代基可实现低至极好（高达15：1）的区域选择性。这些远程取代基的研究为在烯烃和炔烃之间钌（II）催化的[2 + 2]环加成反应的机理提供了更好的理解。探索了广泛的取代的降冰片二烯和降冰片烯在钌（II）催化的[2 + 2]环加成中的反应性。发现环加成物具有高度立体选择性，区域选择性和化学选择性，从而以中等至优异的产率（高达98％）提供环加合物。观察到的化学选择性表明，环加成优先发生在较少取代的双键上。相对速率实验的结果表明，缺电子的烯烃与炔烃在钌（II）催化的[2 + 2]环加成反应中反应较慢。还研究了钌（II）催化的炔烃与降冰片二烯的[2 + 2]环加成反应。发现环加成物是高度立体选择性的，提供了外向立体异构体作为仅有的不良或良好产率（高达91％）的环加合物。已证明Cp * RuCl（COD）在取代的乙炔中具有较高的官能团耐受性。相容性乙炔的实例包括卤代，羧酸衍生物和炔丙醇衍生物。速率比较的结果表明，一般而言，贫电子炔烃会加速降冰片二烯与钌（II）催化的[2 + 2]环加成反应。此外，我们还强调了炔烃组分与Cp * RuCI（COD）之间的空间限制。还研究了非对称选择性钌（II）催化的对称双环烯烃（降冰片二烯和降冰片烯）与手性炔丙基醚之间的[2 + 2]环加成反应。环加成以中等至良好的产率（高达84％）提供了作为唯一的立体异构体的环加合物（外立体化学）。用手性炔丙基醚观察到中等水平的非对映选择性，高达4：1。

著录项

  • 作者

    Jordan, Robert William F.;

  • 作者单位

    University of Guelph (Canada).;

  • 授予单位 University of Guelph (Canada).;
  • 学科 Chemistry Organic.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 274 p.
  • 总页数 274
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 有机化学;
  • 关键词

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