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
A series of chiral cyclometalated iridiumcomplexes have been synthesised by cyclometalating chiral 2-aryl-oxazoline and imidazoline ligands with [Cp*IrCl2]2. These iridacycles were studied for asymmetric transfer hydrogenation reactions with formic acid as the hydrogen source and were found to display various activities and enantioselectivities, with the most effective ones affording up to 63% ee
Catalytic Enantioselective Amination of Alcohols by the Use of Borrowing Hydrogen Methodology: Cooperative Catalysis by Iridium and a Chiral Phosphoric Acid
作者:Yao Zhang、Ching-Si Lim、Derek Sui Boon Sim、Hui-Jie Pan、Yu Zhao
DOI:10.1002/anie.201307789
日期:2014.1.27
synthesis of chiral amines, with reductants ranging from Hantzsch esters, silanes, and formic acid to H2 gas. Alternatively, the amination of alcohols by the use of borrowing hydrogen methodology has proven a highly atom economical and green method for the production of amines without an external reductant, as the alcohol substrate serves as the H2 donor. A catalytic enantioselective variant of this
Cooperative Catalysis: Combining an Achiral Metal Catalyst with a Chiral Brønsted Acid Enables Highly Enantioselective Hydrogenation of Imines
作者:Weijun Tang、Steven Johnston、Chaoqun Li、Jonathan A. Iggo、John Bacsa、Jianliang Xiao
DOI:10.1002/chem.201302437
日期:2013.10.11
Asymmetric hydrogenation of imines leads directly to chiral amines, one of the most important structural units in chemical products, from pharmaceuticals to materials. However, highly effective catalysts are rare. This article reveals that combining an achiral pentamethylcyclopentadienyl (Cp*)–iridium complex with a chiral phosphoric acid affords a catalyst that allows for highly enantioselective hydrogenation