chiral Ir/H8‐binapo catalyst exhibits unprecedented reactivity and excellent enantioselectivity in the hydrogenation of quinoxalines at a high ratio of substrate to catalyst (from 100 to 20 000). This new method provides a practical synthetic approach to give optically active chiral tetrahydroquinoxaline derivatives (see scheme; cod=1,5‐cyclooctadiene).
在底物与催化剂的高比例(100至20000)下,一种容易获得的手性Ir / H 8联苯胺催化剂在喹喔啉加氢中表现出空前的反应性和出色的对映选择性。这种新方法提供了一种实用的合成方法,可以得到光学活性的手性四氢喹喔啉衍生物(参见方案; cod = 1,5-环辛二烯)。
Chiral tetrahydroquinoxalines and dihydroquinoxalinones represent the core structure of many bioactive molecules. Herein, a simple and efficient Rh–thiourea-catalyzed asymmetrichydrogenation for enantiopure tetrahydroquinoxalines and dihydroquinoxalinones was developed under 1 MPa H2 pressure at room temperature. The reaction was magnified to the gram scale furnishing the desired products with undamaged
手性四氢喹喔啉和二氢喹喔啉酮代表了许多生物活性分子的核心结构。在此,开发了一种简单高效的Rh-硫脲催化的对映纯四氢喹喔啉和二氢喹喔啉酮的不对称氢化反应,在室温下1 MPa H 2压力下进行。将反应放大至克级,提供具有未受损的产率和对映选择性的所需产物。该方法的应用在连续流动条件下也成功进行。此外,1 H NMR实验表明,强布朗斯台德酸HCl的引入不仅激活了底物,而且在底物和配体之间建立了阴离子结合。更重要的是,氯离子促进了二氢的异裂,以再生活性二氢物质和HCl,这被计算为决定速率的步骤。进一步的氘标记实验和密度泛函理论(DFT)计算表明,该反应在这种新的催化转化中经历了合理的外球机制。
Asymmetric Hydrogenation of 2- and 2,3-Substituted Quinoxalines with Chiral Cationic Ruthenium Diamine Catalysts
作者:Jie Qin、Fei Chen、Ziyuan Ding、Yan-Mei He、Lijin Xu、Qing-Hua Fan
DOI:10.1021/ol2029096
日期:2011.12.16
The enantioselective hydrogenation of 2-alkyl- and 2-aryl-subsituted quinoxalines and 2,3-disubstituted quinoxalines was developed by using the cationic Ru(η6-cymene)(monosulfonylated diamine)(BArF) system in high yields with up to 99% ee. The counteranion was found to be critically important for the high enantioselectivity and/or diastereoselectivity.