Tse Man Kin, Bhor Santosh, Klawonn Markus, Anilkumar Gopinathan, Jiao Haijun, Spannenberg Anke, Döbler Christian, Mägerlein Wolfgang, Hugl Herbert, Beller Matthias
Leibniz-Institut für Organische Katalyse an der Universität Rostock e.V. Albert-Einstein-Strasse 29a, 18059 Rostock (Germany).
Chemistry. 2006 Feb 20;12(7):1875-88. doi: 10.1002/chem.200501262.
Asymmetric epoxidation of olefins with 30 % H2O2 in the presence of [Ru(pybox)(pydic)] 1 and [Ru(pyboxazine)(pydic)] 2 has been studied in detail (pybox = pyridine-2,6-bisoxazoline, pyboxazine = pyridine-2,6-bisoxazine, pydic = 2,6-pyridinedicarboxylate). 35 Ruthenium complexes with sterically and electronically different substituents have been tested in environmentally benign epoxidation reactions. Mono-, 1,1-di-, cis- and trans-1,2-di-, tri-, and tetra-substituted aromatic olefins with versatile functional groups can be epoxidized with this type of catalyst in good to excellent yields (up to 100 %) with moderate to good enantioselectivies (up to 84 % ee). Additive and solvent effects as well as the relative rate of reaction with different catalysts have been established. It is shown that the presence of weak organic acids or an electron-withdrawing group on the catalyst increases the reactivity. New insights on the reaction intermediates and reaction pathway of the ruthenium-catalyzed epoxidation are proposed on the basis of density functional theory calculation and experiments.
在[Ru(pybox)(pydic)] 1和[Ru(pyboxazine)(pydic)] 2存在下，使用30%的过氧化氢对烯烃进行不对称环氧化反应已得到详细研究（pybox = 吡啶-2,6-双恶唑啉，pyboxazine = 吡啶-2,6-双恶嗪，pydic = 2,6-吡啶二甲酸酯）。35种具有空间和电子性质不同取代基的钌配合物已在环境友好的环氧化反应中进行了测试。具有多种官能团的单取代、1,1-二取代、顺式和反式1,2-二取代、三取代和四取代芳香烯烃可以用这种类型的催化剂进行环氧化，产率良好至优异（高达100%），对映选择性中等至良好（高达84% ee）。已经确定了添加剂和溶剂的影响以及与不同催化剂反应的相对速率。结果表明，催化剂上存在弱有机酸或吸电子基团会提高反应活性。基于密度泛函理论计算和实验，对钌催化环氧化反应的中间体和反应途径提出了新的见解。
