Olefin metathesis, asymmetric metathesis, and tandem catalysis

我们研究的一个主要目标是设计强大的、选择性的催化剂，促进碳-碳键的形成。2005年诺贝尔化学奖颁给Schrock、Grubbs和Chauvin的引文中提到，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催化剂的高可调选择性是实现所需有机化合物合成的主要资产，但它们对空气和水的高敏感性是一个问题。Grubbs催化剂，基于不太亲氧的过渡金属钌，更容易处理，并大大扩大了有机合成中烯烃分解的吸收。然而，尽管如此，它们是短暂的。它们在调优活动和选择性方面也受到限制。研究它们的失活途径使我们开发出一种寿命更长、生产率更高的新催化剂家族。它还提供了扩展的潜力，以确定催化剂的活性位点，从而提高选择性。将鲁棒性与选择性相结合，可以统一烯烃复分解实验发展的两大主流。第二个主要主题是如何耦合不同的催化过程。目前，受顺序催化转化的有机分子通常在一个反应后被分离，在应用第二个反应之前。这在溶剂、化学品和时间方面产生了巨大的成本。然而，用于不同类型转化的催化剂的结构有时是强保守的。也就是说，我们可能只需要改变与构成活性位点的金属结合的基团，就可以改变催化活性的模式。在其他情况下，我们可能还需要更改外围组。在这两种情况下，如果在一种催化转化完成后，我们可以选择性地对催化剂进行修饰，我们就可以“开启”第二种反应模式，无需后续处理就可以进行耦合转化。控制的关键是了解潜在的无机化学。我们的研究重点是发展这样的理解，并利用它来设计使串联催化过程。

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.