ABSTRACT
Ru(II) complexes of TsDPEN containing two alkyl groups on the non-tosylated nitrogen atom are poor catalysts for asymmetric transfer hydrogenation of ketones and imines; this observation provides direct evidence for the importance of the N-H interaction in the transition state for ketone reduction.
Subject(s)
Ethylenediamines/chemistry , Hydrogen/chemistry , Imines/chemistry , Ketones/chemistry , Nitrogen/chemistry , Organometallic Compounds/chemistry , Hydrogenation , Molecular Structure , Oxidation-Reduction , StereoisomerismABSTRACT
A series of kinetic and structural investigations on ruthenium-based catalysts for asymmetric transfer hydrogenation (ATH) of ketones are reported. A method is reported for monitoring the formation of ruthenium hydride species in real time using (1)H NMR spectroscopy.
Subject(s)
Ketones/chemistry , Ruthenium/chemistry , Catalysis , Crystallography, X-Ray , Hydrogenation , Kinetics , Molecular Conformation , Oxidation-ReductionABSTRACT
A series of catalysts have been prepared for use in the asymmetric transfer hydrogenation of ketones. The complexes were prepared using a [4 + 2] cycloaddition reaction at a key step in the reaction sequence. This provides a means for the synthesis of catalysts with modifications at specific sites.
Subject(s)
Amino Alcohols/chemistry , Diamines/chemistry , Organometallic Compounds/chemical synthesis , Ruthenium/chemistry , Catalysis , Cyclization , Hydrogenation , Ketones/chemical synthesis , Ketones/chemistry , Molecular Conformation , Organometallic Compounds/chemistry , StereoisomerismABSTRACT
Stereochemically well-defined ruthenium(II) catalysts have been applied to the asymmetric transfer hydrogenation of a series of ketones. In one case, statistical experimental design was employed to optimize the enantiomeric excess of the product. In the case of the TsDPEN-based systems, the replacement of trans-1,2-diphenyl substitution with cis-, or deletion of one of the phenyl groups, results in significant deterioration of the enantiomeric excess. A new method is described for the synthesis of tethered amino alcohol-containing catalysts.
