Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition‐Metal Catalysts
作者:Jan Seliger、Martin Oestreich
DOI:10.1002/anie.202010484
日期:2021.1.4
A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition‐metal‐catalyzedalcoholracemization and enantioselective Cu‐H‐catalyzed dehydrogenative Si‐O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization
Copper(I)-catalyzed asymmetric hydrogenation of heteroaromatic ketones, cyclic and acyclic enones is reported. The choice of the chiral diphosphine ligand highly influenced enantioselectivity as well as chemoselectivity. Highly enantioselective hydrogenation of ortho-substituted heteroaromatic ketones was achieved using BDPP as the ligand. In the 1,2-selective hydrogenation of acylic enone, SEGPHOS
Copper-Catalyzed Asymmetric Hydrogenation of Aryl and Heteroaryl Ketones
作者:Scott W. Krabbe、Mark A. Hatcher、Roy K. Bowman、Mark B. Mitchell、Michael S. McClure、Jeffrey S. Johnson
DOI:10.1021/ol4021223
日期:2013.9.6
High throughput screening enabled the development of a Cu-based catalyst system for the asymmetric hydrogenation of prochiral aryl and heteroarylketones that operates at H2 pressures as low as 5 bar. A ligand combination of (R,S)-N-Me-3,5-xylyl-BoPhoz and tris(3,5-xylyl)phosphine provided benzylic alcohols in good yields and enantioselectivities. The electronic and steric characteristics of the ancillary
Coordination with RuCl2(PPh3)dppb gave ruthenium(II) N-heterocyclic complexes 4b–d. The structure of complex 4b was fully illuminated by X-ray crystallography. The steric environment of these chiral ruthenium complexes 4b–d was evaluated in asymmetric transfer hydrogenation (ATH) of prochiral ketones in the presence of NaOiPr by using 2-propanol as the hydrogen source and solvent. The resultant catalytic
从光学纯的氨基酸开始合成了一组新的基于喹唑啉的手性配体。与RuCl 2(PPh 3)dppb配位得到钌(II)N-杂环配合物4b–d。配合物4b的结构通过X射线晶体学被完全照亮。通过使用2-丙醇作为氢源和溶剂,在NaO i Pr存在的情况下,在手性酮的不对称转移氢化(ATH)中评估了这些手性钌配合物4b-d的空间环境。所得的催化体系可以实现非常好的对映选择性(高达91%)和高产率(高达99%)。
Highly Enantioselective Transfer Hydrogenation of Prochiral Ketones Using Ru(II)-Chitosan Catalyst in Aqueous Media
作者:György Szőllősi、Vanessza Judit Kolcsár
DOI:10.1002/cctc.201801602
日期:2019.1.23
Unprecedentedly high enantioselectivities are obtained in the transferhydrogenation of prochiral ketones catalyzed by a Ru complex formed in situ with chitosan chiral ligand. This biocompatible, biodegradable chiral polymer obtained from the natural chitin afforded good, up to 86 % enantioselectivities, in the aqueous‐phase transferhydrogenation of acetophenone derivatives using HCOONa as hydrogen donor. Cyclic
在与壳聚糖手性配体原位形成的Ru络合物催化的前手性酮的转移氢化中,获得了前所未有的高对映选择性。这种从天然几丁质中获得的生物相容性,可生物降解的手性聚合物,在使用HCOONa作为氢供体的苯乙酮衍生物的水相转移氢化中,提供了高达86%的良好对映选择性。环酮的对映选择性更高,超过90%,而在杂环酮的转移氢化中,进一步增加,最高可达97%。手性催化剂前体制备易地通过扫描电子显微镜,FT-中期和-far-IR光谱法检测。原位结构通过1 H NMR光谱和使用各种壳聚糖衍生物研究了形成的催化剂。结果表明,Ru预催化剂是通过氨基将生物聚合物与金属配位而形成的。加入氢供体后,该前体转化为水不溶性钌氢化物络合物。通过以高收率和光学纯度制备二十多种手性醇,验证了所开发方法的实用价值。在单次结晶后,将催化剂用于以克为单位获得光学纯的手性醇。