together! A selective Fe‐catalysed enantioselective reduction of quinoxalines and benzoxazines with hydrogen is demonstrated. Key to success is the combination of a chiral Brønsted acid and a well‐defined non‐chiral Fe hydrogenation catalyst. This methodology constitutes an attractive and environmentally favourable alternative to well‐established asymmetric hydrogenations by using precious‐metal‐based catalysts
Asymmetric Transfer Hydrogenation of 2-Substituted Quinoxalines with Regenerable Dihydrophenanthridine
作者:Zaiqi Han、Xiangqing Feng、Haifeng Du
DOI:10.1021/acs.joc.3c02954
日期:2024.3.1
represents one of the most efficient approaches for the synthesis of optically active tetrahyroquinoxalines. In this paper, we demonstrate a metal-free asymmetric transfer hydrogenation of 2-substituted quinoxalines with regenerable dihydrophenanthridine under H2 using a combination of chiral phosphoric acid and achiral borane as catalysts. A wide range of optically active 2-substituted tetrahydroquinoxalines
喹喔啉的不对称氢化是合成光学活性四氢喹喔啉的最有效方法之一。在本文中,我们展示了在H 2下,使用手性磷酸和非手性硼烷作为催化剂,2-取代的喹喔啉与可再生二氢菲啶的无金属不对称转移氢化。以≤98% ee 的高产率生产了多种光学活性 2-取代四氢喹喔啉。
A novel Ir-catalyzed asymmetric hydrogenation protocol for the synthesis of chiral tetrahydroquinoxaline (THQ) derivatives has been developed. By simply adjusting the reaction solvent, bothenantiomers of mono-substituted chiral THQs could be selectively obtained in high yields with excellent enantioselectivities (toluene/dioxane: up to 93% yield and 98% ee (R); EtOH: up to 83% yield and 93% ee (S))
开发了一种用于合成手性四氢喹喔啉 (THQ) 衍生物的新型 Ir 催化不对称氢化方案。通过简单地调整反应溶剂,即可高产率地选择性地获得单取代手性 THQ 的两种对映体,且具有优异的对映选择性(甲苯/二恶烷:收率高达 93%,ee ( R ) 高达 98%;EtOH:收率高达 83%)和 93% ee ( S ))。对于2,3-二取代的手性THQ,获得的顺式氢化产物的收率高达95%,dr为20:1,ee为94%。值得注意的是,该方法也适用于连续流动条件下,产生具有相当收率和对映选择性的克级产品(二恶烷:91% 收率和 93% ee ( R );EtOH:90% 收率和 87% ee ( S ))。与之前报道的 Ir 催化不对称氢化方案不同,该系统表现出显着的改进,因为它不需要额外的添加剂。此外,还进行了全面的机理研究,包括氘标记实验、对照实验、动力学研究和密度泛函理论(DFT)计算,以揭示两种对映体对映选择性的潜在机制。
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.