Reactions and Stereochemistry of Organometallic Compounds Related to Asymmetric Synthesis and Catalytic Activity

有机金属化合物经常被用作将一种有机化合物转化为另一种有机化合物的催化剂。不幸的是，这样的转化经常导致异构体的混合，即分子由相同的原子组成，但其三维结构不同。该项目涉及合成高度不对称的有机金属化合物，旨在作为更具体的催化剂来控制反应产物的三维结构。有机分子的三维结构在生物反应中特别重要，这些有机金属化合物经常用于天然产物的实验室合成。将开展利用金属络合物进行不对称和区域选择性合成的新方法的研究，并阐明立体选择性反应的机理，这些反应在合成上是有用的。更高的氧化态有机金属络合物在这些应用中的潜在用途将被探索。X射线结晶学已经成为表征固体结构的常规工具。然而，许多有机金属化合物在溶液中以构象异构体的混合物的形式重排或存在。本实验室已证明，这些构象的稳定性对产物立体化学的分布起着重要作用。活性中间体和催化物种通常以较低的浓度存在，不能以固体形式分离。将开发一种新的方法来阐明溶液中的详细结构信息。这将涉及到含有与有机金属结合的顺磁性金属离子的配体的设计和合成。这些顺磁性配体产生的各向同性位移和场排列效应将允许详细描述(角度和距离)溶液中的中间体和催化物种。

Organometallic compounds are frequently used as catalysts for the conversion of one organic compound into another. Unfortunately, such conversions often result in mixtures of isomers, i.e., molecules comprised of the same atoms, but differing in their three-dimensional structures. This project involves the synthesis of highly unsymmetrical organometallic compounds designed to function as more specific catalysts to control the three-dimensional structures of reaction products. The three- dimensional structures of organic molecules are especially important in biological reactions, and these organometallic compounds are often used in the laboratory synthesis of natural products. Research will be undertaken to develop new methods using metal complexes for asymmetric and regioselective syntheses and to elucidate the mechanisms of stereoselective reactions which are synthetically useful. The potential utility of higher oxidation state organometallic complexes for these applications will be explored. X-ray crystallography has become a routine tool for structural characterization in solids. However, many organometallic compounds rearrange or exist as mixtures of conformational isomers in solution. It has been shown in this laboratory that the stability of these conformers plays a major role in the distribution of product stereochemistry. Reactive intermediates and catalytic species often exist in lower concentrations and cannot be isolated as solids. A new method will be developed to elucidate detailed structural information in solution. This will involve the design and synthesis of ligands containing paramagnetic metal ions which bind to organometallics. The isotropic shifts and the effects of field alignment produced by these paramagnetic ligands will allow detailed delineation (angles and distances) of intermediates and catalytic species in solution.