The Arnold and Mabel Beckman Laboratories of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., MC 164-30, Pasadena, CA 91125, USA.
Chemistry. 2009 Dec 7;15(47):12978-92. doi: 10.1002/chem.200902172.
The first palladium-catalyzed enantioselective oxidation of secondary alcohols has been developed, utilizing the readily available diamine (-)-sparteine as a chiral ligand and molecular oxygen as the stoichiometric oxidant. Mechanistic insights regarding the role of the base and hydrogen-bond donors have resulted in several improvements to the original system. Namely, addition of cesium carbonate and tert-butyl alcohol greatly enhances reaction rates, promoting rapid resolutions. The use of chloroform as solvent allows the use of ambient air as the terminal oxidant at 23 degrees C, resulting in enhanced catalyst selectivity. These improved reaction conditions have permitted the successful kinetic resolution of benzylic, allylic, and cyclopropyl secondary alcohols to high enantiomeric excess with good-to-excellent selectivity factors. This catalyst system has also been applied to the desymmetrization of meso-diols, providing high yields of enantioenriched hydroxyketones.
首次开发了钯催化的手性仲醇选择性氧化反应，利用易得的手性二胺（-）-sparteine 作为配体，分子氧作为化学计量氧化剂。对碱和氢键供体作用的机理研究导致对原始体系进行了多项改进。即，添加碳酸铯和叔丁醇可大大提高反应速率，促进快速拆分。使用氯仿作为溶剂，可在 23°C 下使用环境空气作为末端氧化剂，从而提高催化剂选择性。这些改进的反应条件允许成功地对苄基、烯丙基和环丙基仲醇进行动力学拆分，获得高对映过量和良好至优异的选择性因素。该催化剂体系还应用于内消旋二醇的去对称化，得到高产率的对映体富集的羟基酮。
