Counter-ion Directed Enantioselective Approaches to Axially Chiral Materials

轴向手性是指由四个基团围绕手性轴成对非平面排列而产生的立体异构体。这类化合物的例子有受阻的联芳基、某些类型的螺环化合物和联烯。异构化是一种限制单键旋转导致立体异构体形成的现象，是天然产物、药物分子和催化剂的一个重要特征。它在所有这些领域的重要性日益增加，这意味着对映体选择性合成阿托品的新方法是极其重要的。本提议的目的是开发和开发用于构建轴向手性分子的新的催化对映选择性方法。我们认为，手性铵反离子可以通过动力学拆分和动态动力学拆分过程来控制这些反应的立体化学。我们还提出了一种光介导的外消旋过程，该过程可以与反离子介导的动力学拆分相结合，使得具有大旋转势垒的联芳烃在室温下能够动态动力学拆分。最后，我们打算以这些反应为例，探讨对映体选择性相转移催化的动力学和机理。

Axial chirality is a term used to refer to stereoisomerism resulting from the non-planar arrangement of four groups in pairs around a chirality axis. Such compounds are exemplified by hindered biaryls, certain classes of spiro compounds, and allenes. Atropisomerism is a phenomenon whereby restricted rotation about a single bond leads to the formation of stereoisomers, and is a key feature of natural products, drug molecules and catalysts. It's increasing importance in all of these fields means that new methods for the enantioselective synthesis of atropisomeric compounds are extremely important. The aim of this proposal is to develop and exploit new catalytic enantioselective methods for the construction of axially chiral molecules. We propose that chiral ammonium counter-ions can be employed to control the stereochemistry of these reactions through kinetic resolution and dynamic kinetic resolution processes. We also propose a light-mediated racemization process that can be coupled with a counter-ion-mediated kinetic resolution, enabling the dynamic kinetic resolution of biaryls with large barriers to rotation at room temperature. Finally, we aim to use these reactions as exemplars to probe the kinetics and mechanism of enantioselective phase-transfer catalysis.