Sigman Matthew S, Miller Jeremie J
Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, USA.
J Org Chem. 2009 Oct 16;74(20):7633-43. doi: 10.1021/jo901698t.
We report the use of Taft steric parameters to correlate the substituent size of a ligand with the enantiomeric ratio of a reaction. Linear free energy relationships can be constructed by plotting the log of enantiomeric ratio (er) versus the steric parameters reported by Taft and modified by Charton. Successful correlations were found for aldehyde and ketone allylation under NHK conditions using modular oxazoline ligands developed in our laboratory. Using these correlations, ligands were designed and evaluated for carbonyl allylation reactions. A break in the Charton plot results and is attributed to a global structural change in the catalyst. Additionally, several previously reported enantioselective reactions are analyzed resulting in excellent correlations for both catalysts and substrates. Finally, limitations and issues are presented with illustrative examples.
我们报道了使用塔夫脱立体参数来关联配体的取代基大小与反应的对映体比例。通过绘制对映体比例（er）的对数与塔夫脱报道并经查尔顿修正的立体参数的关系图，可以构建线性自由能关系。使用我们实验室开发的模块化恶唑啉配体，发现在NHK条件下醛和酮的烯丙基化反应具有成功的相关性。利用这些相关性，设计并评估了用于羰基烯丙基化反应的配体。查尔顿图出现了断点，这归因于催化剂的整体结构变化。此外，对几个先前报道的对映选择性反应进行了分析，结果表明催化剂和底物都具有出色的相关性。最后，通过示例说明了局限性和问题。
