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Iridium catalyzed aromatic borylation and its applications in one-pot preparations of substituted aromatic building blocks.

机译：铱催化的芳香族硼酸酯化及其在一锅法制备取代的芳香族结构单元中的应用。

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摘要

Selective functionalization of hydrocarbons represents one of the most challenging problems in homogeneous and heterogeneous catalysis. During the last decade, iridium catalyzed aromatic borylation has emerged as one of the most convenient methodologies for the regioselective functionalization of aromatic as well as heteroaromatic hydrocarbons. The most striking feature of this new tool available to the synthetic chemist is that the regioselectivities are governed by sterics, and hence, are complementary to those found in electrophilic aromatic substitution or directed ortho metalation. This unique feature allows for the synthesis of new aromatic building blocks, which were previously either unknown or difficult to synthesize. Another useful feature of this new methodology is the tolerance to several common functional groups such as halogens, esters, amides, etc.;Iridium catalyzed borylation ortho to substituents other than H is typically hindered. Evaluation of steric effects of several substituents showed that CN is one of the smallest substituents. Since regioselectivities in Ir catalyzed borylation are controlled by sterics, we reasoned that borylations ortho to CN, an electronic meta director, should be possible. As a test, we examined several 4-substituted benzonitriles and found good ortho selectivity for several substrates. Regioselectivities greater than 99% were obtained for bulkier substituents such as ester, amine, acetanilide and trifluoromethyl. These borylations were the first general examples of ortho-functionalization of 4-benzonitriles. This contrasts with meta-functionalizations, which have been known for more than a century.;Good to high regioselectivities were observed in mono- and di-borylation of a variety of substituted thiophenes. The BPin group was found to survive during electrophilic aromatic bromination reactions. Poor regioselectivities observed with dibpy ligand were improved by using bis-oxazoline derived ligands.;Since Ir catalyzed borylations leave aryl halogen (Cl, Br, and I) bonds intact, it might be useful if chemo-selective cross couplings can be accomplished at the halide positions while retaining the boronate functionality. We have found that under anhydrous basic conditions, cross coupling reactions such as amination, Sonogashira coupling, and C--S coupling can be carried out on the C--halogen bond, while keeping the C--B bond completely intact. The resulting amino boronate esters, aryl alkynyl boronate esters, and aromatic thio ether boronate esters are all new compounds and are difficult to synthesize by any other rout.;5-Coordinate, 16-electron, bi-dentate ligated iridium tris-boryl complexes have been proposed to be the active catalysts in the iridium catalyzed aromatic borylation. Our attempts to synthesize the proposed active catalysts using various bidentate ligands is presented, ultimately culminating in the successful synthesis of couple of (bis-phosphine)Ir(BPin)3 complexes, which are the first examples of stable, 16-electron, iridium tris-boryl complexes. The complex (dippe)Ir(BPin)3 borylates aromatic compounds at room temperature.
机译：烃的选择性官能化是均相和非均相催化中最具挑战性的问题之一。在过去的十年中，铱催化的芳族硼化已经成为芳族和杂芳族烃的区域选择性官能化的最方便的方法之一。合成化学家可以使用的这种新工具最显着的特征是，区域选择性受空间位阻的支配，因此与亲电子芳族取代或定向邻位金属化中的互补。这种独特的功能允许合成新的芳香族结构单元，而这些芳香族结构单元以前是未知的或难以合成的。这种新方法的另一个有用特性是对几种常见官能团（如卤素，酯，酰胺等）的耐受性；通常会阻碍铱催化的硼氢化邻位取代H以外的取代基。评估几个取代基的空间效应表明，CN是最小的取代基之一。由于Ir催化的硼化反应中的区域选择性受空间位阻的控制，因此我们认为与电子元导向器CN相邻的硼烷基化应该是可能的。作为测试，我们检查了几种4-取代的苄腈，发现对几种底物具有良好的邻位选择性。对于较大的取代基如酯，胺，对乙酰苯胺和三氟甲基，获得了大于99％的区域选择性。这些硼化是4-苄腈的邻位官能化的第一个一般实例。这与一个多世纪以来已知的亚功能化形成对比。在各种取代的噻吩的单-和二-硼化中观察到良好的区域选择性至高的区域选择性。发现BPin基团在亲电子芳族溴化反应中存活。通过使用双恶唑啉衍生的配体改善了用二苯并基配体观察到的区域选择性差。由于Ir催化的硼化反应可完整保留芳基卤素（Cl，Br和I）键，如果可以在此处完成化学选择交叉偶联，则可能有用。在保留硼酸酯官能度的同时卤化位置。我们发现，在无水碱性条件下，可以在C-卤素键上进行交叉偶联反应，如胺化，Sonogashira偶联和C-S偶联，同时保持C-B键完全完整。所得的氨基硼酸酯，芳基炔基硼酸酯和芳族硫醚硼酸酯都是新化合物，很难用其他任何途径合成。; 5-配位，16-电子，双齿连接铱三硼烷基络合物有人提出将其作为铱催化的芳族硼化反应中的活性催化剂。提出了我们尝试使用各种双齿配体合成拟议的活性催化剂的尝试，最终最终成功合成了双（双膦）Ir（BPin）3配合物，这是稳定的16电子铱三-硼基配合物。配合物（dippe）Ir（BPin）3在室温下硼化芳族化合物。

著录项

  • 作者

    Chotana, Ghayoor Abbas.;

  • 作者单位

    Michigan State University.;

  • 授予单位 Michigan State University.;
  • 学科 Chemistry Inorganic.;Chemistry Organic.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 280 p.
  • 总页数 280
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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