Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA.
J Am Chem Soc. 2012 Apr 25;134(16):7126-34. doi: 10.1021/ja3012534. Epub 2012 Apr 11.
Linear free energy relationship (LFER) substituent parameters are commonly employed for exploring reaction mechanisms and very recently have been used to guide the design of asymmetric catalysts, but their usage in dynamic covalent chemistry is rare. Herein, the properties of an in situ-generated dynamic multicomponent covalent assembly that creates tris(pyridine) metal complexes incorporating chiral secondary alcohols were explored using LFER-based steric parameters. The diastereomeric ratio (dr) of the assembly was correlated with the magnitude of the exciton-coupled circular dichroism (ECCD) induced by chiral alcohols. Charton steric parameters were successfully correlated with the dr values. Through the combination of these correlations, both the dr and CD intensity were predicted for test alcohols. These correlations were also employed to measure a few new Charton parameters. Finally, the prediction of enantiomeric excess (ee) of test samples with various alcohol structures was also successfully achieved. The prediction of spectral properties in advance by using well-established steric parameters is shown to be useful for rapid ee screening because the need for calibration curves and enantiomerically enriched samples is avoided.
线性自由能关系（LFER）取代参数通常用于探索反应机制，最近也被用于指导不对称催化剂的设计，但它们在动态共价化学中的应用很少。在此，使用基于 LFER 的空间参数研究了一种原位生成的动态多组分共价组装的性质，该组装可生成包含手性仲醇的三（吡啶）金属配合物。组装的非对映选择性（dr）与手性醇诱导的激子耦合圆二色性（ECCD）的大小相关。Charton 空间参数与 dr 值成功相关。通过这些相关性的结合，既预测了测试醇的 dr 值，又预测了 CD 强度。这些相关性还用于测量一些新的 Charton 参数。最后，还成功地预测了具有各种醇结构的测试样品的对映体过量（ee）。通过使用成熟的空间参数预先预测光谱性质，对于快速 ee 筛选非常有用，因为避免了对校准曲线和对映体富集样品的需求。
