Enantioselective reduction of <i>N</i>-alkyl ketimines with frustrated Lewis pair catalysis using chiral borenium ions
作者:Dan M. Mercea、Michael G. Howlett、Adam D. Piascik、Daniel J. Scott、Alan Steven、Andrew E. Ashley、Matthew J. Fuchter
DOI:10.1039/c9cc02900a
日期:——
Enantioselective reduction of ketimines was demonstrated using chiral N-heterocyclic carbene (NHC)-stabilised borenium ions in frustratedLewispair catalysis. High levels of enantioselectivity were achieved for substrates featuring secondary N-alkyl substituents. Comparative reactivity and mechanistic studies identify key determinants required to achieve useful enantioselectivity and represent a step
Liquid Chromatographic Resolution of Fendiline and Its Analogues on a Chiral Stationary Phase Based on (+)-(18-Crown-6)-2,3,11,12-tetracarboxylic Acid
作者:Ga Lee、Myung Hyun
DOI:10.3390/molecules191221386
日期:——
analogues were resolved on a CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylicacid. Fendiline was resolved quite well with the separation factor (α) of 1.25 and resolution (RS) of 1.55 when a mobile phase consisting of methanol-acetonitrile-trifluoroacetic acid-triethylamine at a ratio of 80/20/0.1/0.5 (v/v/v/v) was used. The comparison of the chromatographic behaviors for the resolution of fendiline
1,1′-Binaphthyldiamine-Based Lewis Bases as Readily Available and Efficient Organocatalysts for the Reduction of<i>N</i>-Aryl and<i>N</i>-Alkyl Ketimines
development of simple, low-cost, efficient, and sustainable routes to enantiomerically pure amines is a topic of extraordinary interest, specially in view of future industrial applications. In this context, we wish to report a chemical and stereochemical efficient synthesis of chiral amines through the Lewis base activated trichlorosilane reduction of ketimines. An organocatalyst, easily prepared in a single
Enantioselective Hydrogenation of Imines with Chiral (Phosphanodihydrooxazole)iridium Catalysts
作者:Patrick Schnider、Guido Koch、Roger Prétôt、Guozhi Wang、Frank Michael Bohnen、Carl Krüger、Andreas Pfaltz
DOI:10.1002/chem.19970030609
日期:1997.6
AbstractCationic iridium(I) complexes of chiral phosphanodihydrooxazoles were used as catalysts for the enantioselective hydrogenation of prochiral N‐alkyl and N‐aryl imines. The complexes are air‐stable crystalline solids that can be readily prepared and are easy to handle. The structures of two complexes were determined by X‐ray analysis. For N‐alkyl imines of acetophenone, enantiomeric excesses of up to 79% were obtained. Dialkyl ketimines and cyclic imines showed lower reactivity and selectivity. A remarkable dilution effect was observed for the hydrogenation of the N‐phenyl imine of acetophenone: decreasing the substrate and catalyst concentration led to a significant improvement of the enantioselectivity. Thus, up to 89% ee could be achieved using 0.1 mol% of catalyst. The highest enantioselectivities were obtained in weakly coordinating solvents such as CH2Cl2. Additives such as halides, imides, or amines were found to poison the catalyst. Hydrogen pressures of 100 bar were usually employed, but in some cases identical results were achieved with only 1 bar H2.