Olefin metathesis, asymmetric metathesis, and tandem catalysis

我们研究的一个主要目标是设计坚固、选择性强的催化剂，以促进碳-碳键的形成。正如2005年诺贝尔化学奖授予施罗克、格拉布斯和肖文的引文中指出的那样，烯烃复分解是目前用于这一目的的最强大的工具之一。虽然SchRock催化剂的高选择性、可调是实现所需有机化合物合成的主要优势，但它们对空气和水的高度敏感性是有问题的。格拉布斯催化剂以亲氧性较低的过渡金属Ru为基础，更易于操作，极大地扩大了有机合成中烯烃歧化反应的吸收。然而，尽管有这种强大的生命力，但它们都是短暂的。它们在调节活动性和选择性方面也受到限制。通过研究它们的失活途径，我们开发了一种寿命更长、生产效率更高的新催化剂家族。它还提供了更大的潜力来定义催化剂上的活性中心，从而实现选择性。将稳健性和选择性结合起来，将把烯烃复分解实验开发的两个主流结合起来。第二个主要主题是如何将不同的催化过程结合起来。目前，经历顺序催化转化的有机分子通常是在一个反应后分离出来的，然后再应用第二个反应。这会在溶剂、化学品和时间方面产生巨大的成本。然而，用于不同类型转化的催化剂的结构有时是非常保守的。也就是说，我们可能只需要改变结合在构成活性中心的金属上的基团，就可以改变催化活性的模式。在其他情况下，我们可能也需要更换外围设备组。在任何一种情况下，如果在一种催化转化完成后，我们可以有选择地对催化剂进行修饰，我们就可以打开第二种反应模式，进行耦合转化，而不需要做任何工作。控制的关键是对潜在的无机化学的了解。我们的研究重点是发展这种理解，并利用它来设计使串联催化过程成为可能。

A major goal of our research is the design of robust, selective catalysts that promote the formation of carbon-carbon bonds. Olefin metathesis is one of the most powerful tools now in use for this purpose, as noted in the citation awarding the 2005 Nobel Prize in Chemistry to Schrock, Grubbs, and Chauvin. While the high, tunable selectivity of the Schrock catalysts is a major asset in achieving the synthesis of desired organic compounds, their high sensitivity to air and water is problematic. The Grubbs catalysts, based on the less oxophilic transition metal ruthenium, are much more easily handled, and have greatly expanded the uptake of olefin metathesis in organic synthesis. Despite this robustness, however, they are short-lived. They are also limited in terms of the ease of tuning activity and selectivity. Studying their deactivation pathways led us to develop a new family of catalyst that is longer-lived and more productive. It also offers expanded potential to define the active site at the catalyst, and thus selectivity. Combining robustness with selectivity would unite the two main streams of experimental development in olefin metathesis.  A second major theme centers on ways to couple different catalytic processes. At present, organic molecules that are subjected to sequential catalytic transformations are typically isolated following one reaction, prior to applying the second. This incurs significant costs in terms of solvents, chemicals, and time. However, the structures of catalysts used for different types of transformations are sometimes strongly conserved. That is, we may need to change only the group bound to the metal that constitutes the active site, in order to transform the mode of catalytic activity. In other cases, we may need to change peripheral groups as well. In either case, if we can selectively modify the catalyst after one type of catalytic transformation is complete, we can "turn on" the second mode of reaction, and carry out coupled transformations without workup. Essential to control is an understanding of the underlying inorganic chemistry. Our studies focus on developing such understanding, and using it to design enabling tandem catalytic processes.