钌催化的炔烃水合还原反应的机理研究及新催化体系的优化设计

Alcohols are used throughout the commodity and fine chemical industries and this large demand renders the production of alcohols from hydrocarbon feedstocks an important goal in catalysis. The conversion of terminal alkynes to alcohols represents such ideal reactions. “One-pot” processes in which a single catalyst carries out several reactions in one vessel are attractive, where a series of reactions could take place to give the final product, avoiding the need for excess reaction auxiliaries, work-up and purification stages. Such an approach has generated much interest within the synthetic community in an effort to enhance the efficiency of chemical synthesis, but it typically promote the formation of by-products as well as the desired ones, and are not amenable to optimization of the individual transformations. Recently, Herzon et al. have advanced the “one-pot” strategy (tandem catalysis) significantly. They reported that a single catalyst (half-sandwich ruthenium-based complex) can support both the hydration and hydrogenation activities, which has led to the development of a method to effect the anti-Markovnikov (linear-selective) reductive hydration of terminal alkynes. Although the tandem catalysis is showcasing its power in organic synthesis to form alcohol, relatively less attention has been paid to this strategy, leaving room for further development. Herein we propose using computational chemistry to deeply understand the mechanisms of Herzon et al.’s tandem catalytic processes choosing experimentally realized reactions as representatives. The mechanistic understanding will be used to rationalize the experimental puzzles and serve as a basis for our new development. After deeply understanding the mechanisms of these tandem catalytic systems, we will use computation as “experimental” manner to explore new tandem catalytic system, mainly including, designing new ligand and expanding the hitherto sole use of ruthenium metal to other transition metals such as cobalt and rhodium. We expect these studies will really enrich the transition-metal-mediated tandem catalytic systems.

醇类化合物普遍存在于日常生活用品和化工产品中。通过碳氢化合物的催化转化来生成新的醇类是一理想化学合成方法，用炔烃作为底物来合成醇就属于这类反应。从原子经济学考虑，化学家期望得到一个既可以催化炔烃水合又可以完成随后加氢还原的催化剂，同时没有副反应可以影响主反应。这样的反应属于串联催化体系，即一个催化剂可以催化一个底物完成一系列反应，但金属催化领域该类反应很有挑战性。Herzon等近来大幅拓展催化串联反应到炔烃的水合还原反应。虽然该串联反应在合成化学中崭露头角，但并没有得到广泛关注。我们将用计算化学来研究实验上新报道的串联反应(炔烃的水合还原反应)的机理来深入认识这些反应并揭示实验上的困惑。在机理研究的基础上，我们将以计算为“实验”手段来探索新的出体系：优化设计新的金属螯合配体和阴离子茂环配体，并拓展现有的钌催化剂到d9系列的钴和铑催化剂。我们期望本课题的研究能够拓展金属催化的串联反应体系。

借助密度泛函理论计算，我们系统性研究了协同催化和串联催化反应体系，研究内容主要涉及钌催化的炔烃水合还原串联反应、[Au]‒[Ru]和[Ru]‒[Ru]催化的炔烃水合还原反应以及相关的协同催化反应过程，通过对势能面、分子构型、分子轨道与电子结构等分析，在分子和原子水平上系统地阐明了其中催化活性、选择性、惰性化学键活化规律、电子转移等关键化学转化过程与机制，探索了杂原子和不同配体对催化反应活性的调控因素，诠释了其中过渡态和重要中间化合物的结构-活性关系，揭示了相关催化反应的基本实验现象，总结了此类反应的基本规律。在过渡金属催化惰性化学键活化领域提出了新的基元反应类型，揭示了过渡金属络合物中吡啶或者含有-NR2等路易斯碱性基团的配体具有“质子中转站”的双官能作用，协助完成惰性化学键的活化与转化。另外，在研究内容基础上的拓展研究了基于镍、钯和铜等相关协同催化反应过程与机制，总结了这一系列催化反应中共性和特性。这些研究为完善和设计构筑具有特定功能的新催化剂和化学反应提供理论指导和预测。我们的研究结果主要以科研论文的形式发表，第一标注在国际高水平期刊论文ACS Catal.、Org. Lett.、J. Org.Chem.等发表研究论文9篇。