Exploitation of strongly pi-donating Ylidic substituents

强 pi-donating ylidic 取代基的开发

• 批准号: 386618-2010
• 负责人: Dyker, CAdam
• 金额: $ 2.55万
• 依托单位: University of New Brunswick
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2013
• 资助国家: 加拿大
• 起止时间: 2013-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=528977
• 关键词: Exploitation; strongly; pi; donating; Ylidic

Replacing one or more hydrogen atoms in a molecule by another atom or group of atoms, known as a substituent, will result in a new molecule with altered properties relative to the parent structure. The influence of the substituent can be very dramatic and offers the opportunity to access important chemical properties from even simple frameworks. As an example, the substitution of the four hydrogen atoms in ethene, an inert gaseous molecule, with four nitrogen-based substituents (amino groups) gives rise to an air-sensitive ethene derivative that can be used as a homogeneous reducing agent in chemical synthesis. In another case, it was discovered two decades ago that replacing hydrogen atoms in methylene (the parent "carbene" with a fleeting lifetime as a reactive intermediate) with amino substituents leads to bottle-able(!) solids that have now become ubiquitous in many areas of chemistry. These, and many other achievements, result from the superb "pi-donating" effects of the amino substituents. Recent results, however, have demonstrated that so-called "ylidic" substituents surpass classical amino functionalities as pi-donors. The targeted exploitation of this fact will open up many new avenues of fundamental and applied chemistry, and is the central theme of the proposed research program. Specific goals of this research include: 1) the preparation of the most powerful organic reducing agents as selective and homogeneous alternatives to heterogeneous metals. The absence of metallic by-products is of particular value for pharmaceutical syntheses; 2) the stabilization of as-of-yet elusive reactive intermediates. These compounds are invoked as transient molecules in many synthetic pathways and their stabilization will provide important fundamental knowledge, but also allow for them to be used in other applications (just as for carbenes); 3) the preparation of new families of compounds (ligands) capable of donating above-average amounts of electron density to transition metals. These ligands will subsequently be used in transition metal catalysis, with the goal of discovering highly active catalysts for new or improved synthetic methodologies relevant to natural products, and materials science.

将分子中的一个或多个氢原子替换为另一个原子或原子基团，称为取代基，将导致新分子的性质相对于母体结构发生变化。取代基的影响可以是非常显著的，并提供了机会，以获得重要的化学性质，即使是简单的框架。例如，用四个氮基(氨基)取代惰性气体分子乙烯中的四个氢原子，就得到了一种对空气敏感的乙烯衍生物，它可以在化学合成中用作均质还原剂。在另一个案例中，20年前人们发现，用氨基取代亚甲基中的氢原子(作为活性中间体的母体“卡宾”寿命很短)会导致瓶装(！)固体现在化学的许多领域中无处不在。这些，以及许多其他的成就，都是由于氨基取代基的卓越的“pi捐赠”效应。然而，最近的结果表明，作为pi供体，所谓的叶立德取代基超过了经典的氨基官能团。对这一事实的有针对性的开发将为基础化学和应用化学开辟许多新的途径，也是拟议的研究计划的中心主题。这项研究的具体目标包括：1)制备最强大的有机还原剂，作为多相金属的选择性和均质替代品。没有金属副产物对药物合成具有特殊的价值；2)稳定迄今难以捉摸的活性中间体。这些化合物在许多合成途径中被称为瞬时分子，它们的稳定性将提供重要的基础知识，但也允许它们用于其他应用(就像卡宾一样)；3)能够向过渡金属提供高于平均电子密度的新的化合物(配体)家族的制备。这些配体随后将用于过渡金属催化，目标是发现高活性催化剂，用于与天然产品和材料科学相关的新的或改进的合成方法。