Asymmetric Hydrogenation Of Aromatic Ketones Research Articles

Heterogeneous Enantioselective Catalysis with Chiral Encoded Mesoporous Pt-Ir Films Supported on Ni Foam.

The development of heterogeneous catalysts for asymmetric synthesis is one of the most challenging topics in chemistry, as it allows obtaining enantiomerically pure compounds. Recently, metal layers incorporating molecular chiral cavities, obtained by electroreduction of a metal source in the simultaneous presence of a non-ionic surfactant and asymmetric molecules, have been proposed for a wide range of applications, including enantioselective electroanalysis and electrosynthesis, as well as chiral separation. In contrast to this previous work, solely based on electrochemical phenomena, herein we designed and employed nanostructured chiral encoded Pt-Ir alloys, supported on high surface area nickel foams, as heterogeneous catalysts for the asymmetric hydrogenation of aromatic ketones. Fine-tuning the experimental conditions allows achieving very high enantioselectivity (>80%), combined with improved catalyst stability.

Carboxyl Group-Directed Iridium-Catalyzed Enantioselective Hydrogenation of Aliphatic γ-Ketoacids

Although the transition metal-catalyzed asymmetric hydrogenation of aromatic ketones has been extensively explored, the enantioselective hydrogenation of aliphatic ketones remains a challenge becau...

Asymmetric hydrogenation of pro-chiral ketones catalyzed by chiral Ru(II)-benzene organometallic compounds containing amino acid based aroylthiourea ligands

A series of Ru(II)-benzene organometallic compounds (1–6) constructed from [RuCl2(η6-benzene)]2 and chiral aroylthiourea ligands (L1-L6) obtained from D/L-phenylalanine, was fully characterized. The chiral complexes along with 2-propanol and NaOH effected the asymmetric hydrogenation of aromatic ketones at 82 °C within 8–10 h. The reduction reactions proceeded with excellent conversions and enantiomeric excesses (up to 99%).

Copper encapsulated alkaloids composite: An effective heterogeneous catalyst for electrocatalytic asymmetric hydrogenation

A novel heterogeneous catalyst, alkaloid@Cu was prepared by the entrapment of commercially purchased alkaloids within non-noble metallic copper nanoparticles. This composite was compacted into a coin and directly used as cathode for electrocatalytic asymmetric hydrogenation of aromatic ketones. Using water as hydrogen source, optically active alcohols with 71% ee value and 93% yield were obtained under very mild conditions.

ChemInform Abstract: Asymmetric Hydrogenation of Aromatic Ketones by New Recyclable Ionic Tagged Ferrocene—Ruthenium Catalyst System.

AbstractSimple process, water tolerance, and high activity make the introduced catalysis practical and appealing.

Mechanism of Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by a Combined System of Ru(π-CH2C(CH3)CH2)2(cod) and the Chiral sp(2)N/sp(3)NH Hybrid Linear N4 Ligand Ph-BINAN-H-Py.

The combination of a Goodwin-Lions-type chiral N4 ligand, (R)-Ph-BINAN-H-Py ((R)-3,3'-diphenyl-N(2),N(2')-bis((pyridin-2-yl)methyl)-1,1'-binaphthyl-2,2'-diamine; L), with Ru(π-CH2C(CH3)CH2)2(cod) (A) (cod = 1,5-cyclooctadiene) catalyzes the hydrogenation of acetophenone (AP) to (R)-1-phenylethanol (PE) with a high enantiomer ratio (er). Almost no Ru complex forms, with A and L remaining intact throughout the reaction while generating PE quantitatively according to [PE] = k(obs)t(2). An infinitesimal amount of reactive and unstable RuH2L (B) with C2-Λ-cis-α stereochemistry is very slowly and irreversibly generated from A by the action of H2 and L, which rapidly catalyzes the hydrogenation of AP via Noyori's donor-acceptor bifunctional mechanism. A CH-π-stabilized Si-face selective transition state, CSi, gives (R)-PE together with an intermediary Ru amide, D, which is inhibited predominantly by formation of the Ru enolate of AP. The rate-determining hydrogenolysis of D completes the cycle. The time-squared term relates both to the preliminary step before the cycle and to the cycle itself, with a highly unusual eight-order difference in the generation and turnover frequency of B. This mechanism is fully supported by a series of experiments including a detailed kinetic study, rate law analysis, simulation of t/[PE] curves with fitting to the experimental observations at the initial reaction stage, X-ray crystallographic analyses of B-related octahedral metal complexes, and Hammett plot analyses of electronically different substrates and ligands in their enantioselectivities.

Asymmetric hydrogenation of aromatic ketones by new recyclable ionic tagged ferrocene-ruthenium catalyst system.

Newly developed ferrocene-oxazoline-phosphine ligands containing quaternary ammonium ionic groups exhibited excellent catalytic performance for the ruthenium-catalyzed hydrogenation of aromatic ketonic substrates to give chiral secondary alcohols with high levels of conversions and enantioselectivities. Simple manipulation process, water tolerance, high activity and good recyclable property make this catalysis practical and appealing.

ChemInform Abstract: Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by L‐Proline Derivatives Modified Ru/γ‐Al2O3.

ChemInform Abstract: Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by L‐Proline Derivatives Modified Ru/γ‐Al₂O₃.

Why p-Cymene? Conformational effect in asymmetric hydrogenation of aromatic ketones with a η(6) -arene/ruthenium(II) catalyst.

The global reaction route mapping (GRRM) methods conveniently define transition states in asymmetric hydrogenation and transfer hydrogenation of aromatic ketones via the [RuH{(S,S)-TsNCH(C6 H5 )CH(C6 H5 )NH2 }(η(6) -p-cymene)] intermediate. Multiple electrostatic CH/π interactions are the common motif in the preferred diastereometric structures.

Asymmetric Hydrogenation of Aromatic Ketones Catalysed by L-Proline Derivatives Modified Ru/γ-Al2O3

The asymmetric hydrogenation of aromatic ketones catalysed by L-proline derivative- and PPh3-modified 1.0%Ru/γ-Al2O3 was studied. The effects of different stabilisers, P/Ru ratio, modifiers, modifier concentration, solvents, base additives and base concentration on the asymmetric hydrogenation of aromatic ketones were investigated. The results showed that L-proline derivatives had good modification effects on the 1.0%Ru/γAl2O3/2tpp catalyst. Under optimum conditions, the hydrogenation enantioselectivity of acetophenone was 70%. The enantioselectivity of the hydrogenation product of propiophenone could reach 81%.

Heterogeneous asymmetric hydrogenation of aromatic ketones enhanced by silanols on highly monodispersed silica spheres

A triphenylphosphine-stabilized Ir/SiO2 catalyst modified by a chiral diamine was synthesized with four silica spheres as support for the asymmetric hydrogenation of aromatic ketones. The H-bond between substrate and silanols and the interaction between substrate and modifier commonly affected the steric configuration of asymmetric hydrogenation of aromatic ketones. With the silanols increasing, the activity of asymmetric hydrogenation significantly increased. This is the first report of heterogeneous asymmetric hydrogenation of aromatic ketones enhanced by silanols on highly monodispersed silica spheres with >99.9% ee and >99% conversion.

ChemInform Abstract: Asymmetric Hydrogenation of Aromatic Ketones Using an Iridium(I) Catalyst Containing Ferrocene‐Based P—N—N Tridentate Ligands.

Abstract Six ferrocene-based P–N–N tridentate ligands have been synthesized and applied in the Ir-catalyzed asymmetric hydrogenation of aromatic ketones. A wide range of ketones are hydrogenated enantioselectively to afford the corresponding optically active alcohols in the enantioselectivities of up to 86.6% ee. The substituent groups on the P -phenyl and pyridine rings play an important role with regard to the enantioselectivity.

Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by L-Proline-Modified Ru-PPh3/γ-Al2O3 Catalyst

Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by L-Proline-Modified Ru-PPh3/γ-Al2O3 Catalyst

Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by Achiral Mono-phosphine TPPTS-Stabilized Ru in PEG-Water

Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by Achiral Mono-phosphine TPPTS-Stabilized Ru in PEG-Water

Asymmetric hydrogenation of aromatic ketones using an iridium(I) catalyst containing ferrocene-based P–N–N tridentate ligands

Six ferrocene-based P–N–N tridentate ligands have been synthesized and applied in the Ir-catalyzed asymmetric hydrogenation of aromatic ketones. A wide range of ketones are hydrogenated enantioselectively to afford the corresponding optically active alcohols in the enantioselectivities of up to 86.6% ee. The substituent groups on the P-phenyl and pyridine rings play an important role with regard to the enantioselectivity.

Cyclodextrin–[RuCl2(Arene)]2 conjugates: another way to enhance the enantioselectivity of aromatic ketones reduction by aromatic ligands' volume

Eight amino alcohol-modified β-CDs CD-1–CD-8 have been synthesized in acceptable yields and were employed to form artificial metalloenzymes with [RuCl2(Benzene)]2 and [RuCl2(Mesitylene)]2, respectively. All the conformations of CD-1–CD-8, the complexes between CD-1–CD-8 and [RuCl2(Arene)]2, and the inclusion complexes between CD-1–CD-8 and acetophenone were characterized by UV, 1H NMR, 1H ROESY NMR, and quantum calculation. The catalytic activity of the formed artificial metalloenzymes in the asymmetric hydrogenation of aromatic ketones, especially the effect of the aromatic ligands' volume on the enantioselectivity were investigated in detail, in which it was obvious that the enantioselectivity increased as the increase in the aromatic ligands' volume. For the best artificial metalloenzyme constructed from the complex between CD-8 and [RuCl2(Mesitylene)]2, which not only exhibits a good tolerance to a wide range of substrates but also demonstrates some substrate selectivity, 76.39% ee was obtained for acetophenone and 79.67% ee for 2-acetylnaphthalene. A strategy to improve the enantioselectivity in the asymmetric reactions catalyzed by the artificial metalloenzymes based on CDs has been provided.

A Ruthenium Catalyst with Simple Triphenylphosphane for the Enantioselective Hydrogenation of Aromatic Ketones

AbstractAn efficient Ru catalyst constructed from simple and commercially available triphenylphosphane and enantiopure (1S,1′S)‐1,1′‐biisoindoline (BIDN) was applied to the asymmetric hydrogenation of aromatic ketones. A range of simple aromatic ketones could be hydrogenated with good to excellent enantioselectivities (up to 95 % ee). An appropriate enantioselective transition state was proposed to explain the high enantioselectivity obtained with this catalytic system. This study represents the first example to establish a practical Noyori‐type catalyst with a simple achiral monophosphane for highly enantioselective hydrogenation.

High activity iridium catalyst for the asymmetric hydrogenation of aromatic ketones

The asymmetric hydrogenation of aromatic ketones catalyzed by iridium complexes was investigated in the presence of chiral damines and achiral phosphines. The catalytic system with triphenylphosphine and 9-amino(9-deoxy)epicinchonine exhibited high activity and enantioselectivity in the asymmetric hydrogenation of simple aromatic ketones. A series of simple aromatic ketones were hydrogenated completely in just 2 h at room temperature with good ee value (up to 87%).

ChemInform Abstract: Immobilization of Chiral Catalysts on Magnetite Nanoparticles for Highly Enantioselective Asymmetric Hydrogenation of Aromatic Ketones.

Abstract4,4′‐Bisphosphonic acid‐BINAP‐ruthenium catalyst DPR and 4,4′‐disilyl‐BINAP‐ruthenium catalyst DSR are prepared and tested in the title reaction.

Preparation of microgel-supported chiral catalysts and their application in the asymmetric hydrogenation of aromatic ketones

An enantiomerically pure chiral monomer (S,S)-2 was prepared and copolymerized with styrene and four different cross-linkers to produce four distinct microgel-supported chiral TsDPEN derivatives. These chiral copolymers were allowed to form complexes with [RuCl2(cymene)]2 and the resulting homogeneous catalysts were applied in asymmetric hydrogenation reactions of aromatic ketones to give enantioenriched secondary alcohols in quantitative yield. These polymeric catalysts can be easily separated from the reaction mixture and recycled several times without a significant loss in catalytic activity.