Asymmetric Imine Hydroboration Catalyzed by Chiral Diazaphospholenes
作者:Matt R. Adams、Chieh-Hung Tien、Robert McDonald、Alexander W. H. Speed
DOI:10.1002/anie.201709926
日期:2017.12.22
first use of diazaphospholenes as chiral catalysts has been demonstrated with enantioselective iminehydroboration. A chiral diazaphospholene prepared in a simple three‐step synthesis from commercial materials has been shown to achieve the highest enantioselectivity for the hydroboration of alkyl imines with pinacolborane reported to date. Enantiomer ratios of up to 88:12 were obtained with low (2 mol %)
Asymmetric hydrogenation of N-alkyl and N-aryl ketimines using chiral cationic Ru(diamine) complexes as catalysts: the counteranion and solvent effects, and substrate scope
作者:Fei Chen、Ziyuan Ding、Yanmei He、Jie Qin、Tianli Wang、Qing-Hua Fan
DOI:10.1016/j.tet.2012.03.019
日期:2012.7
Asymmetrichydrogenation of N-alkyl and N-aryl ketimines catalyzed by chiralcationic η6-arene-(N-monosulfonylated diamine) Ru(II) complexes has been investigated. Strong counteranion and solvent effects on the enantioselectivity were observed. The ruthenium catalyst bearing non-coordinating BArF− anion was found to be particularly effective for the hydrogenation of acyclic and exocyclic N-alkyl ketimines
Protic additives or impurities promote imine reduction with pinacolborane
作者:Blake S. N. Huchenski、Alexander W. H. Speed
DOI:10.1039/c8ob02330a
日期:——
enantioinduction. While the reactions described herein are not competitive in conversion with established imine reduction technologies, this work reveals that the presence of protic impurities must be considered as a promoter of side reactions in catalyzed imine hydroborations. Amines also promote imine reduction in certain cases, raising the possibility of a slow autocatalytic reaction. The ability of water
N-TMPN-CH2C6H4B(C6F5)2 (where TMPNH is 2,2,6,6-tetramethylpiperidinyl) which is able to reversibly activate H2 through an intramolecular mechanism is synthesized. This new substance makes use of the concept of moleculartweezers where the active N and B centers are located close to each other so that one H2 molecule can fit in this void and be activated. Because of the fixed geometry of this ansa-ammonium-borate it forms
合成了第一个能够通过分子内机制可逆地激活 H2 的 ansa-aminoborane N-TMPN-CH2C6H4B(C6F5)2(其中 TMPNH 是 2,2,6,6-四甲基哌啶基)。这种新物质利用分子镊子的概念,其中活性 N 和 B 中心彼此靠近,因此一个 H2 分子可以放入这个空隙中并被激活。由于这种柄型硼酸铵的固定几何形状,它形成了一个 1.78 A 的短 NH...HB 二氢键,由 X 射线分析确定。因此,结合氢可以在 100 摄氏度以上释放。 此外,短 H...H 接触和 NH...H(154 度)和 BH...H(125 度)角表明二氢N-TMPNH-CH2C6H4BH(C6F5)2 中的相互作用本质上是部分共价的。作为讨论机制的基础,进行了量子化学计算,发现分裂 H2 所需的能量可以来自所得离子碎片之间的库仑吸引力,或“库仑为 Heitler-London 买单”。空气和水分稳定的
Iron-catalyzed transfer hydrogenation of imines assisted by an iron-based Lewis acid
作者:Hui-Jie Pan、Teng Wei Ng、Yu Zhao
DOI:10.1039/c5ob02119g
日期:——
An iron-catalyzed transfer hydrogenation of N-aryl and N-alkyl imines using isopropanol as the hydrogen donor is reported for the first time.