Catalysts For Asymmetric Hydrogenation Research Articles

Asymmetric Hydrogenations (Nobel Lecture 2001).

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of enantiopure 1,2-diamine attached to cross-linked polystyrene and its application to an insoluble catalyst for asymmetric hydrogenation

A novel enantiopure 1,2-diamine ( 5 ) having two phenolic hydroxy groups was attached into chloromethylated polystyrene through benzyl ether linkage, which was used as a chiral ligand of the catalyst in asymmetric hydrogenation of acetophenone.

Asymmetric Hydrogenation of Enamides in Aqueous Media with a New Water‐Soluble Chiral Rhodium‐α,α‐trehalose‐Derived Phosphine—Phosphinite Catalyst.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Multiple Dendritic Catalysts for Asymmetric Transfer Hydrogenation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Asymmetric Hydrogenations (Nobel Lecture 2001)

AbstractThe start of the development of catalysts for asymmetric hydrogenation was the concept of replacing the triphenylphosphane ligand of the Wilkinson catalyst with a chiral ligand. With the new catalysts, it should be possible to hydrogenate prochiral olefins. Knowles and his co‐workers were convinced that the phosphorus atom played a central role in this selectivity, as only chiral phosphorus ligands such as (R,R)‐DIPAMP, whose stereogenic center lies directly on the phosphorus atom, lead to high enantiomeric excesses when used as catalysts in asymmetric hydrogenation reactions. This hypothesis was disproven by the development of ligands with chiral carbon backbones. Although the exact mechanism of action of the phosphane ligands is not incontrovertibly determined to this day, they provide a simple entry to a large number of chiral compounds.

A Novel System Consisting of Easily Recyclable Dendritic Ru‐BINAP Catalyst for Asymmetric Hydrogenation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of Dendritic BINAP Ligands and Their Applications in Asymmetric Hydrogenation

AbstractA new type of chiral dendritic ligands with 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (BINAP) located at the focal point of the dendrimer has been synthesized through the condensation reaction of 5‐amino BINAP and Fréchet‐type poly (aryl ether) dendrons with carboxyl groups as the linker in high reaction yields, respectively. The ruthenium complexes of these dendritic ligands were found to be very efficient catalysts in asymmetric hydrogenation of 2‐phenylacryclic acids as well as facile catalyst recycling.

Asymmetric Hydrogenations (Nobel Lecture)

AbstractFor Abstract see ChemInform Abstract in Full Text.

Asymmetric hydrogenation of enamides in aqueous media with a new water-soluble chiral rhodium-α,α-trehalose-derived phosphine–phosphinite catalyst

A new chiral rhodium catalyst with α,α-trehalose-derived phosphine–phosphinite (α,α-TREHAPPN) ligand, [(TREHAPPN)Rh(cod)]BF 4 8 has been prepared. This catalyst is soluble in water and is an effective chiral catalyst for asymmetric hydrogenation of N-acyldehydroamino acids in aqueous media to give enantiomerically enriched α-amino acid derivatives with R configuration. The simple decantation allows retrieval of the catalyst from the reaction mixture, the recovered catalyst being re-used without marked loss of enantioselectivity.

Multiple dendritic catalysts for asymmetric transfer hydrogenation.

The first and second generation multiple dendritic ligands based on chiral diamine were synthesized in a convergent approach and were well-characterized by NMR and MS techniques. Their ruthenium complexes prepared in situ had good solubility in the reaction medium (azeotrope of formic acid and triethylamine) and demonstrated high catalytic activity and enantioselectivity comparable to monomeric catalysts in the asymmetric transfer hydrogenation of ketones and imines. Quantitative yields and for some cases a slightly higher enantioselectivity (up to 98.7% ee) were obtained in the dendritic catalysis. Considering the high local catalyst concentrations at the periphery, diones were tested for the possible synergic reactivity between catalytic units at the surface, while no apparent differences were noted.

Asymmetric Hydrogenations (Nobel Lecture) Copyright© The Nobel Foundation 2002. We thank the Nobel Foundation, Stockholm, for permission to print this lecture.

The start of the development of catalysts for asymmetric hydrogenation was the concept of replacing the triphenylphosphane ligand of the Wilkinson catalyst with a chiral ligand. With the new catalysts, it should be possible to hydrogenate prochiral olefins. Knowles and his co-workers were convinced that the phosphorus atom played a central role in this selectivity, as only chiral phosphorus ligands such as (R,R)-DIPAMP, whose stereogenic center lies directly on the phosphorus atom, lead to high enantiomeric excesses when used as catalysts in asymmetric hydrogenation reactions. This hypothesis was disproven by the development of ligands with chiral carbon backbones. Although the exact mechanism of action of the phosphane ligands is not incontrovertibly determined to this day, they provide a simple entry to a large number of chiral compounds.

New Chiral Ligand N‐Toluenesulfonyl‐2,2′‐dimethoxy‐6, 6′‐di‐aminobiphenyl for Catalytic Asymmetric Transfer Hydrogenation of Ketones

AbstractA new chiral ligand N‐p‐toluenesulfonyl‐2,2′‐dimethoxy‐6,6′‐diaminobiphenyl (Ts‐DMBDPPA) was prepared from 2,2′‐dimethoxy‐6,6′‐diaminobiphenyl via N‐tosylation. Its Ru(II) complex was effective catalysts for catalytic asymmetric transfer hydrogenation of aromatic ketones (with ee's up to 69.3%).

Highly effective chiral ortho-substituted BINAPO ligands (o-BINAPO): applications in Ru-catalyzed asymmetric hydrogenations of beta-aryl-substituted beta-(acylamino)acrylates and beta-keto esters.

A novel family of chiral ortho-substituted BINAPO ligands (o-BINAPO) were synthesized from BINOL, and their Ru complexes were highly efficient catalysts for asymmetric hydrogenation of beta-aryl-substituted beta-(acylamino)acrylates and beta-aryl-substituted beta-keto esters. The Ru-bisphosphinite catalysts can tolerate an E/Z mixture of beta-aryl-substituted beta-(acylamino)acrylates. These highly enantioselective hydrogenations provide a useful way to prepare beta-aryl-substituted beta-amino acids and beta-hydroxyl acids.

Efficient Asymmetric Hydrogenation of γ-Amino Ketone Hydrochloride Derivatives Catalyzed by (2S,4S)-4-Dicyclohexylphosphino-2-diphenylphosphinomethyl-1-(N-methylcarbamoyl)-pyrrolidine(MCCPM)-Rhodium complex1

The title complex, (2S,4S)-MCCPM-Rh(I) complex, was found to be an efficient catalyst for asymmetric hydrogenation of γ-amino ketone hydrochloride derivatives.

ChemInform Abstract: Dendritic Catalysts for Asymmetric Transfer Hydrogenation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Asymmetric hydrogenation ofo‐Cresol andm‐Cresol catalyzed by silica‐supported methylcellulose–L‐alanine–Pd complex

AbstractSilica‐supported methylcellulose–L‐alanine–palladium complex (SiO2‐MC–LA–Pd) has been prepared and found to be a high optically active catalyst for asymmetric hydrogenation of o‐cresol and m‐cresol to give (S)‐2‐methylcyclohexanone and (R)‐3‐methylcyclohexanone, respectively, at 25 °C and under an atmospheric hydrogen pressure. The optical yields of (S)‐2‐methylcyclohexanone and (R)‐3‐methylcyclohexanone amounted to 91.5 and 68.5%, respectively, when optimum Pd content in SiO2‐MC–LA–Pd complex, reaction temperature and solvent were selected. SiO2‐MC–LA–Pd catalyst also has shown high stability. The optical yields for (S)‐2‐methylcyclohexanone and (R)‐3‐methylcyclohexanone were kept over 90 and 60%, respectively, when the catalyst was reused several times. Moreover, SiO2‐MC–LA–Pd complex is an economical catalyst. The methylcellulose is an abundant natural biopolymer and the procedure for preparation of the complex is very simple. Copyright © 2001 John Wiley & Sons, Ltd.

Preparation of silica‐supported methylcellulose‐L‐proline–Pt complex and its catalytic behaviors in asymmetric hydrogenation of propiophenone

AbstractA new chiral polymer–metal complex, silica‐supported methylcellulose‐L‐proline–Pt complex (SiO2‐MC‐LP–Pt) has been found to be a high optically active catalyst for asymmetric hydrogenation of propiophenone to (R)‐1‐phenyl‐1‐propanol at 30 °C and under atmospheric hydrogen pressure. The product and optical yields of 1–phenyl‐1‐propanol amounted to 62.5 and 92.2%, respectively. The product and optical yields were remarkably affected by the Pt content in the complex, the kind of solvent and the reaction temperature. This catalyst was very stable and could be reused several times without remarkable change in optical catalytic activity. Copyright © 2001 John Wiley & Sons, Ltd.

ChemInform Abstract: Preparation and Use of MeO‐PEG‐Supported Chiral Diphosphine Ligands. Soluble Polymer‐Supported Catalysts for Asymmetric Hydrogenation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Rhodium versus ruthenium: contrasting behaviour in the asymmetric transfer hydrogenation of α-substituted acetophenones

The reduction of a number of α-substituted acetophenones has been achieved using both ruthenium(II)- and rhodium(III)-based asymmetric transfer hydrogenation catalysts employing formic acid as the hydrogen donor.

Asymmetric reduction of ketones via whole cell bioconversions and transfer hydrogenation: complementary approaches

Prochiral aryl and dialkyl ketones were enantioselectively reduced to the corresponding alcohols using whole cells of the white-rot fungus Merulius tremellosus ono991 as a biocatalytic reduction system and ruthenium(II)–amino alcohol and iridium(I)–amino sulfide complexes as metal catalysts in asymmetric transfer hydrogenation. Comparison of the results showed that the corresponding chiral alcohols could be obtained with moderate to high enantioselectivities (e.e.s of up to 98%). The biocatalytic and transfer hydrogenation approaches appear to be complementary. The biocatalytic approach is the most suitable for the enantioselective reduction of chloro-substituted (aryl) ketones, whereas in the reduction of α,β-unsaturated compounds excellent results were obtained using the catalytic hydrogenation protocol.