Asymmetric Hydrogenation Using Rhodium Complexes Generated from Mixtures of Monodentate Neutral and Anionic Phosphorus Ligands
作者:Dominik J. Frank、Axel Franzke、Andreas Pfaltz
DOI:10.1002/chem.201202408
日期:2013.2.11
anionic phosphorus ligands was synthesized and evaluated in the asymmetric rhodium‐catalyzed hydrogenation of functionalized olefins by using either catalysts containing identical ligands or catalysts generated from mixtures of two different ligands. We expected that the combination of an anionic ligand with a neutral ligand would favor the formation of hetero over homo bis‐ligand complexes due to charge
通过使用含有相同配体的催化剂或由两种不同配体的混合物生成的催化剂,合成并评估了一系列单齿中性和阴离子磷配体,并在不对称铑催化的官能化烯烃加氢中进行了评估。我们预计,由于电荷排斥,阴离子配体与中性配体的组合将比杂双配体形成杂多。NMR光谱研究证实,电荷效应确实可以使平衡向杂双配体络合物转移。在一些情况下,中性膦与阴离子性膦,一种手性和另一种非手性的组合比两种中性配体的类似混合物具有更高的对映选择性。阴离子亚磷酰胺和中性磷酸二酯的混合物可获得最佳结果。据推测,在这种情况下,两个配体之间的氢键还稳定了杂配体组合。