Hydrogenation Of Aromatic Ketones Research Articles

New palladium(II) complexes with ferrocenyl Schiff bases in the hydrogenation of aromatic ketones

Two new palladium complexes with chelating phosphorus-free ferrocenyl-imine ligands derived from 1,2-diaminocyclohexane and 1,2-diphenylethylenediamine were investigated in the hydrogenation of aromatic ketones. It was found that these catalysts are active in reactions performed with H2 as well as in transfer hydrogenation using 2-propanol/NaOH as a hydrogen donor. In the hydrogenation of acetophenone (APh), two products could be formed, 1-phenylethanol (PhE) and ethylbenzene (EtB), and the reaction selectivity in the studied system was controlled by the kind of solvent and the amount of free ligand excess. In the hydrogenation of acetophenone derivatives, higher selectivity to 1-arylethanol was achieved under hydrogen transfer conditions than under 10 bars of H2 and some ketones were hydrogenated only using this method.

Ketone transfer hydrogenation reactions catalyzed by catalysts based on a phosphinite ligand

Reaction of (±)-1-(2-furyl) ethanol with an equivalent Ph2PCl in the presence of Et3N proceeds in dry toluene under an argon atmosphere to give 1-(furan-2-yl)ethyl diphenylphosphinite (1) in good yield. Mononuclear complexes [dichloro(η6-p-cymene)(1-furan-2-ylethyl diphenylphosphinite)ruthenium(II)] (2), [dichloro(η6-benzene)(1-furan-2-ylethyl diphenylphosphinite)ruthenium(II)] (3), [chloro(η4-1,5-cyclooctadiene)(1-furan-2-ylethyl diphenylphosphinite)rhodium(I)] (4) and [dichloro(η5-pentamethylcyclopentadienyl)(1-furan-2-ylethyl diphenylphosphinite)iridium(III)] (5) were synthesized and characterized by microanalysis, infrared, MS, and NMR spectroscopies. The complexes are employed as catalysts in transfer hydrogenation of aromatic ketones. The complexes catalyzed reduction of a variety of aromatic ketone substrates bearing electron-withdrawing or donating substituents with very high conversion rates (up to 99%); 5 was the most efficient catalyst for the transfer hydrogenation of ketones.

Commercial Cu2Cr2O5Decorated with Iron Carbide Nanoparticles as a Multifunctional Catalyst for Magnetically Induced Continuous‐Flow Hydrogenation of Aromatic Ketones

AbstractCopper chromite is decorated with iron carbide nanoparticles, producing a magnetically activatable multifunctional catalytic system. This system (ICNPs@Cu2Cr2O5) can reduce aromatic ketones to aromatic alcohols when exposed to magnetic induction. Under magnetic excitation, the ICNPs generate locally confined hot spots, selectively activating the Cu2Cr2O5surface while the global temperature remains low (≈80 °C). The catalyst selectively hydrogenates a scope of benzylic and non‐benzylic ketones under mild conditions (3 bar H2, heptane), while ICNPs@Cu2Cr2O5or Cu2Cr2O5are inactive when the same global temperature is adjusted by conventional heating. A flow reactor is presented that allows the use of magnetic induction for continuous‐flow hydrogenation at elevated pressure. The excellent catalytic properties of ICNPs@Cu2Cr2O5for the hydrogenation of biomass‐derived furfuralacetone are conserved for at least 17 h on stream, demonstrating for the first time the application of a magnetically heated catalyst to a continuously operated hydrogenation reaction in the liquid phase.

The solvent determines the product in the hydrogenation of aromatic ketones using unligated RhCl3 as catalyst precursor

RhCl3-catalysed hydrogenation/hydrodeoxygenation of aromatic ketones produced alkylcyclohexanes in TFE and cyclohexyl alkyl alcohols in water at moderate temperatures. Rh-nanoparticles were found to be the true catalysts.

The Comparative Effect of Particle Size and Support Acidity on Hydrogenation of Aromatic Ketones

AbstractA comparative study was reported for both the effects of shape‐confined cubic Pd particle size (8, 13, and 21 nm) and surface property of most commonly used supports (SiO2, Al2O3, and silica‐alumina) on catalytic performance in the chemoselective hydrogenation of three model bio‐oil chemicals (benzaldehyde, acetophenone, and butyrophenone). The results showed that the size of Pd particles could be more associated with the hydrogenation reaction than acidities of the supports. Smaller size of Pd particles, regardless of the type of the support, provided the higher catalytic performance. XPS data showed that the electronic properties of Pd particles were similar, therefore, the possible reasons were the higher fraction of Pd atoms on corner in smaller particles, the lower accessibility of hydrogen atom to reactant on bigger particles, and the more low‐coordinated sites in the small‐size particles due to the short‐range ordering. In addition, Pd/SA catalysts (Brønsted acid sites on the support) showed the highest conversion and TOF compared to Pd/Al2O3 and Pd/SiO2 catalysts. This might be due to the enhanced the diffusion rates of the chemicals on the surface of the catalysts although they could not induce the ionic effect from the metal surface. Pd/SiO2 catalysts performed better than Pd/Al2O3 catalysts (Lewis acid sites on the support). The flexible SiOH groups on surface made the easy interaction with the metal particles and promote the reaction.

Polyethyleneimine-Modified Polymer as an Efficient Palladium Scavenger and Effective Catalyst Support for a Functional Heterogeneous Palladium Catalyst.

The polyethyleneimine-modified polymers, polystyrene–divinylbenzene-based (TAs) and polymethacrylate-based polymers (TAm), were used as palladium scavengers to eliminate residual palladium species after palladium on carbon-catalyzed Sonogashira-type coupling reaction. Since both TAs and TAm indicated relatively favorable elimination abilities toward residual palladium species in the reaction mixture, the affinities of TAs and TAm for palladium species were used as supports for palladium catalysts. The TAm-supported palladium catalyst (Pd/TAm) indicated better catalyst properties for the chemoselective hydrogenation compared to those of the corresponding TAs-supported palladium catalyst (Pd/TAs). Aromatic benzyl ethers; aromatic and aliphatic N-Cbzs; and aromatic carbonyl groups were smoothly hydrogenated in the presence of 1–5 mol % of Pd/TAm in MeOH or 2-PrOH. In contrast, the hydrogenation of aromatic ketones was selectively suppressed in morpholine which act as appropriate catalyst poison and solvent. Furthermore, Pd/TAm-catalyzed chemoselective hydrogenation was applicable to continuous-flow reaction.

Solvent and substituent effects in hydrogenation of aromatic ketones over Ru/polymer catalyst under very mild conditions

The paper reports on the solvent and the substituent effects in hydrogenation of aromatic ketones (acetophenone and its derivatives) in the presence of Ru catalyst supported on functionalized gel-type methacrylate-styrene resin under very mild conditions (1 bar H2, 40 °C). The investigated solvents included methanol, 2-propanol, tetrahydrofuran, toluene, isooctane, and cyclohexane, with and without addition of water. The best catalytic activity was obtained in biphasic solvent system consisting of isooctane/water (1:1). In methanol and 2-propanol the beneficial role of water was observed. The effects are discussed in terms of solvent protic/aprotic and polar/apolar properties. The impact of substituents depended on their electron-donating/withdrawing character, and on the position on the aromatic ring of acetophenone. The presence of electron donating substituents tended to increase the reaction rate, and the electron withdrawing group slowed down the process. Steric effect was observed for methylacetophenone isomers with CH3 group at ortho, meta and para positions.

Synthesis, Crystal Structure of Chiral Ferrocenyl Amino Alcohols, and Its Use for Asymmetric Transfer Hydrogenation

Two chiral ferrocenyl amino alcohols (IIIa and IIIb) have been synthesized for the iridium catalyzed asymmetric transfer hydrogenation of aromatic ketones. The structures of two chiral ferrocenyl amino alcohols have been determined by single crystal X-ray diffraction (CIF files CCDC nos. 1056737 (IIIa) and 1056734 (IIIb)). The results show that the activity and enantioselectivity of the chiral iridium catalyst are very sensitive to the substrate structure. Ir(I)-catalyzed asymmetric transfer hydrogenation of acetophenone resulted in moderate to good yield and lower enantioselectivity; asymmetric transfer hydrogenation of proopiophenone and 2-benzoylpyridine resulted in lower yield and lower enantioselectivity; as for 4-benzoylpyridine, good results have been achieved.

Chiral α-hydroxy acid-coadsorbed TiO2photocatalysts for asymmetric induction in hydrogenation of aromatic ketones

Modification of titanium dioxide (TiO2) photocatalysts with chiral reagents was evaluated by the hydrogenation of aromatic ketones. The strong adsorption of chiral mandelic acid (R)-MA on TiO2 was confirmed by comparing the inhibition effect IR values. The enantioselectivities were affected by not only the chiral reagents but also the TiO2 crystalline samples, suggesting that the interaction between aromatic ketones and MA on TiO2 should depend on the surface structure and morphology of TiO2 particles.

Developments in transfer hydrogenations of aromatic ketones catalyzed by boron compounds

Boron complexes BL1 and BL2 were prepared from O-donor ligands, 2,2′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L1) and 2,2′-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L2). The complexes were fully characterized by 1H and 13C NMR, LC-MS/MS, TGA/DTA, UV-Vis, elemental analysis, SEM, and FTIR. The transfer hydrogenation of acetophenone derivatives was investigated by the boron complexes in the presence of isoPrOH, as the hydrogen source, under basic condition with NaOH. The results showed that the boron complexes were promising catalytic precursors for transfer hydrogenation of aromatic ketones in 0.1 M isoPrOH solution (up to 99%). Both steric and electronic factors of this class of molecules had a significant impact on the catalytic properties.

Synthesis of NHC-Oxazoline Pincer Complexes of Rh and Ru and Their Catalytic Activity for Hydrogenation and Conjugate Reduction

We describe the preparation and catalytic reactions of new CCN pincer Rh and Ru complexes containing NCH-oxazoline hybrid ligands. Oxazolinyl-phenyl-imidazolium derivatives (3) were suitable ligand precursors for the CCN pincer scaffold. C–H bond activation of 3 with RhCl3·3H2O in the presence of NEt3 yielded the desired CCN pincer Rh complexes 5 in 13–27% yields. The related CCN pincer Ru complexes 8–10 were synthesized in good yields by C–H bond activation of p-cymene Ru complexes 7 in the presence of NaOAc in DMF. The chiral complexes 8 and 9 had two diastereomers according to the coordination of CO and OAc ligands. The CCN Rh complexes showed catalytic activity for conjugate reduction of ethyl β-methylcinnamate with hydrosilane, with moderate enantioselectivity. The CCN Ru complexes were found to be active in the hydrogenation of aromatic ketones. In particular, hydrogenation of 9-acetylanthracene took place at not only the C═O bond but also the anthracene ring. The Ru complexes were also used as cata...

ChemInform Abstract: Advantageous Asymmetric Ketone Reduction with a Competitive Hydrogenation/Transfer Hydrogenation System Using Chiral Bifunctional Iridium Catalysts.

Hydrogenation of aromatic ketones with chiral bifunctional amidoiridium complexes proceeds in preference to transfer hydrogenation in methanol, in which the pressurised hydrogen can suppress unintended racemisation of the alcoholic product, leading to enhanced enantioselectivity.

Hydrogenation of Aldehydes and Ketones to Corresponding Alcohols with Methylamine Borane in Neat Water

Chemoselective hydrogenation of various aldehydes and ketones with methylamine borane (MeAB) in neat water was investigated. MeAB is suitable for green organic reactions, for MeAB is a nontoxic, environmentally benign, and easily handled reagent. Aldehydes were selectively and rapidly hydrogenated in excellent yields (86–97%) for 30 min, but hydrogenation of aromatic ketones needed over 20 h at room temperature because of their poor water solubility and steric hindrance. Thus we investigated polyethylene glycol (PEG400) and acidic cation-exchange D072 resin as catalysts to accelerate the hydrogenation reaction of aromatic ketones and achieved excellent yields within several hours. PEG 400 and D072 resin are both suitable for green organic reactions. The D072 resin was reused up to four times without any significance loss in activity.

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%.

Asymmetric Transfer Hydrogenation of Aromatic Ketones Catalyzed by New Chiral C2-Symmetric Bis(sulfonyl) tetraaza Ligands Complexed with [Ru(η 6-p-cymene)Cl2]2 in Water

In this report, a new series of C2-symmetric bis(sulfonyl) tetraaza ligands were synthesized from (1S,2S)-1,2-diarylethylenediamine analogues and tested in the asymmetric transfer hydrogenation (ATH) of aromatic ketones by complexing with [Ru(η 6-p-cymene)Cl2]2 employing sodium formate as hydrogen source in neat water. A moderate to excellent conversion (~99.8 %) and overall satisfying enantioselectivity (~92.8 %) were obtained with varied electronic and steric effects of the substituents on ligands and substrates. A new series of C2-symmetric bis(sulfonyl) tetraaza ligands was synthesized from (1S,2S)-1,2-diarylethylenediamine analogues and tested in the asymmetric transfer hydrogenation of aromatic ketones by complexing with [Ru(η6-p-cymene)Cl2]2 employing formate sodium as hydrogen source in neat water. A moderate to excellent conversion (~99.8 %) and overall satisfying enantioselectivity (~92.8 %) were obtained with varied electronic and steric effects of the substituents on ligands and substrates.

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

ChemInform Abstract: A Ruthenium Catalyst with Simple Triphenylphosphane for the Enantioselective Hydrogenation of Aromatic Ketones.

AbstractThe method represents the first example of using a practical Noyori‐type catalyst with a simply achiral monophosphane for highly enantioselective hydrogenation.

Ruthenium-Catalysed Efficient Asymmetric Transfer Hydrogenation of Aromatic Ketones using Cinchona Alkaloids as Chiral Ligands

Cinchona alkaloid derivatives were applied in asymmetric transfer hydrogenation of aromatic ketones in a ruthenium catalytic system using i-PrOH as the hydrogen source. A series of aromatic ketones...

Corrigendum: Ruthenium Catalysts Containing Rigid Chiral Diamines and Achiral Diphosphanes for Highly Enantioselective Hydrogenation of Aromatic Ketones

Corrigendum: Ruthenium Catalysts Containing Rigid Chiral Diamines and Achiral Diphosphanes for Highly Enantioselective Hydrogenation of Aromatic Ketones