Hydrogenation Of Acetophenone Research Articles

Sacrificial Synthesis of Supported Ru Single Atoms and Clusters on N-doped Carbon Derived from Covalent Triazine Frameworks: A Charge Modulation Approach.

High‐temperature pyrolysis of nitrogen (N)‐rich, crystalline porous organic architectures in the presence of a metal precursor is an important chemical process in heterogeneous catalysis for the fabrication of highly porous N‐carbon‐supported metal catalysts. Herein, covalent triazine framework (CTF) and CTF‐I (that is, CTF after charge modulation with iodomethane) are presented as sacrificial templates, for the synthesis of carbon‐supported Ru catalysts—Ru‐CTF‐900 and Ru‐CTF‐I‐900 respectively, following high‐temperature pyrolysis at 900 °C under N2 atmosphere. Predictably, the dispersed Ru on pristine CTF carrier suffered severe sintering of the Ru nanoparticles (NPs) during heat treatment at 900 °C. However, the Ru‐CTF‐I‐900 catalyst is composed of ultra‐small Ru NPs and abundant Ru single atoms which may have resulted from much stronger Ru—N interactions. Through modification of the micro‐environment within the CTF architecture, Ru precursor interacted on charged‐modulated CTF framework shows electrostatic repulsion and steric hindrance, thus contributing toward the high density of single Ru atoms and even smaller Ru NPs after pyrolysis. A Ru—Ru coordination number of only 1.3 is observed in the novel Ru‐CTF‐I‐900 catalyst, which exhibits significantly higher catalytic activity than Ru‐CTF‐900 for transfer hydrogenation of acetophenone.

Controlling reaction rate of phase transfer hydrogenation of acetophenone by application of low external electric field

AbstractThe controllable mass transfer and reaction rate for phase transfer hydrogenation of acetophenone across a well‐defined boundary were investigated. The effect of solvent was found important and 1‐butanol exhibited the best performance among the five investigated homologous alcohol solvents, consistent with its higher solubility in water and greater dielectric constant. Initial reaction rates increased with increasing electric potential, consistent with enhanced mass transfer across the aqueous/organic boundary. At longer reaction times, deactivation was apparent. It correlated with increasing voltage and is ascribed to lower equilibrium concentration of reactive species at the interface. External control over reaction rate was demonstrated by switching the applied electric potential over the course of the reaction. Effects of external electric field on enantioselectivity were also explored with reversal field direction. The changes correlate with catalyst decomposition.

Asymmetric Hydrogenation of Acetophenone Catalyzed by Chirally Modified Ruthenium Nanoparticles Supported on Carbon Nanotubes

AbstractDifferent types of carbon nanotubes as carriers were used to prepare ruthenium nano‐catalysts loaded outside (named as Ru/CNTs) and inside (named as Ru@CNTs) the tube. The catalysts were modified in situ with chiral ligands (1S, 2S)‐DPEN (1S, 2S)‐DPEN=(1S, 2S)‐1,2‐diphenyl‐1,2‐ethanediamine). In the presence of TPP (TPP=triphenylphosphine) as the stabilization, the catalytic asymmetric hydrogenation of acetophenone was carried out with the modified catalysts. A novel approach to prepare the inside‐loaded catalysts of Ru@CNTs was explored in the preparation. The catalyst can efficiently prevent the Ru nanoparticles from oxidizing in the air in this approach. The catalysts were well characterized by means of TEM, XRD, XPS, BET and H2 Pulse Chemisorption. The effect of the diameter of carbon nanotubes on the particle size of ruthenium nanoparticles loaded on the tubes was also well studied. When Ru@CNTs (8 %, S) (“S” abbreviated from “short”, the same below) was used in the asymmetric hydrogenation of acetophenone, 100 % conversion of acetophenone achieved, and the ee value reached 76.4 %. Under the same reaction conditions, 100 % conversion of acetophenone as well as the highest ee value of 80.8 % were obtained when Ru/CNTs (8 %, S) was applied in the reaction.

Enzyme-Inspired Assembly: Incorporating Multivariate Interactions to Optimize the Host-Guest Configuration for High-Speed Enantioselective Catalysis.

To achieve a rapid asymmetry conversion, the substrate objects suffer from accelerated kinetic velocity and random rotation at the cost of selectivity. Inspired by natural enzymes, optimizing the host-guest configuration will realize the high-performance enantioselective conversion of chemical reactions. Herein, multivariate binding interactions were introduced into the 1D channel of a chiral catalyst to simulate the enzymatic action. An imidazolium group was used to electrophilically activate the C═O unit of a ketone substrate, and the counterion binds the hydrogen donor isopropanol. This binding effect around the catalytic center produces strong stereo-induction, resulting in high conversion (99.5% yield) and enantioselectivity (99.5% ee) for the asymmetric hydrogenation of biomass-derived acetophenone. In addition, the turnover frequency of the resulting catalyst (5160 h-1 TOF) is more than 58 times that of a homogeneous Ru-TsDPEN catalyst (88 h-1 TOF) under the same condition, which corresponds to the best performance reported till date among all existing catalysts for the considered reaction.

Impact of the surface hydrophobicity/hydrophilicity ratio on the catalytic properties of Ni nanoparticles/MCM-41 system used in the hydrogenation of acetophenone

Three nickel catalysts were prepared supporting pre-synthetized monodisperse Ni nanoparticles of 16 nm. As support, nanospheres of MCM-41 were used. Two batches of these supports were superficially modified by silylation treatments with different functionalizing agents: methyltrimethoxysilane and hexamethyldisilazane. These procedures led to three catalysts whose only structural differences were the surface hydrophobicity degrees. These catalysts were tested in chemoselective hydrogenation of acetophenone and the conversion level was increased by effect of the silylation. Instead, selectivity to 1-phenylethanol, the product of interest, stayed at very similar and high values, about 95 %. The sequence of activity levels was explained considering local effects (steric and energetic) of the different functionalizing groups.

Electrochemical Synthesis of Fe–Cu Composites Based on Copper(II) Ferrite and Their Electrocatalytic Properties

Copper(II) ferrite is synthesized by the co-precipitation method in the absence and in the presence of polyvinyl alcohol which is followed by thermally treatment at 300, 500, 700, and 900°С. The specific surface area of thus prepared samples is determined. X-ray diffraction data point to the partial thermal reduction of CuFe2O4 + polymer samples. CuFe2O4 samples synthesized in the absence of polymer are reduced in the electrochemical system to form Fe–Cu composites with the different content of reduced metals depend on the temperature of thermal treatment. Electronic spectroscopy studies of samples reduced electrochemically reveal the presence of crystallites shaped as hexagonal prisms presumably formed by copper and iron-copper layers and covered by reduced iron and its oxide Fe3O4. The experiments show that the thus synthesized Fe–Cu composites exhibit electrocatalytic activity in electrochemical hydrogenation of acetophenone: its hydrogenation rate is higher by a factor of 2.5–6.4 as compared with its electrochemical reduction.

Synthesis, thermal, electrochemical and catalytic behavior toward transfer hydrogenation investigations of the half-sandwich RuII complexes with 2-(2′-quinolyl)benzimidazoles

A series ligands (L3-14) of derived from 2-(2′-quinolyl)benzimidazole (QuBim, L1) and 2-(2′-quinolyl)-5,6-dimethylbenzimidazole (QuDmBim, L2) which are an NN-type ligands have been synthesized and characterized with various techniques such as NMR, UV–vis, FT-IR spectroscopy, elemental analysis and X-ray diffraction. The substituted ligands derived from QuBim and QuDmBim have been used as sustaining ligands in the RuII-catalyzed transfer hydrogenation (TH) of acetophenone to secondary alcohols in the presence i-PrOH/KOH. The half-sandwich complexes (C1-14) of RuII with NN-type ligands have been synthesized by cleavage of [(η6-p-cymene)Ru(μ-Cl)]2 dimer. The resulting complexes have been characterized by NMR, UV–vis, FT-IR spectroscopy and elemental analysis. The thermal and electrochemical properties of selected complexes and ligands were investigated.

Microwave-Assisted Synthesis of Zirconium Phosphate Nanoplatelet-Supported Ru-Anadem Nanostructures and Their Catalytic Study for the Hydrogenation of Acetophenone

The catalytic hydrogenation of organic compounds containing carbonyl groups has been extensively studied and widely used in industrial processes. Herein, we report the preparation of a novel nanomaterial, α-zirconium phosphate (α-ZrP) nanoplatelet-supported ruthenium nano-anadem catalyst, which possesses high selectivity in the catalytic hydrogenation of aromatic ketones. The α-ZrP nanoplatelets were prepared using a modified reflux method. Through an ion-exchange and reduction reaction pathway, ruthenium nanoparticles were loaded on ZrP to produce Ru-ZrP with a nano-anadem structure. The successful synthesis of Ru-ZrP composites is supported by a series of characterization techniques (PXRD, SEM, TEM, EDS, XPS, FT-IR, etc.). Compared with pure ZrP nanoplatelets, the catalytic hydrogenation of acetophenone has been dramatically improved when using Ru-ZrP. Full conversion was achieved at room temperature, and the yield of 1-cyclohexylehtanol was up to 95%. The effects of reaction time, reaction temperature, and hydrogen pressure were investigated. The investigation illustrates that there are two proposed reaction pathways in the hydrogenation of acetophenone, which are further supported by computational analyses. Recycling experiments indicate that the Ru-ZrP material could be reused four times without a noticeable activity decrease.

Syntheses, structures, and immobilization of ruthenium(II) complexes with alkoxysilane groups functionalized N,N′-diamine and phosphine ligands

Treatment of [RuCl2(PPh3)3] with N-(β-aminoethyl)-γ-aminopropylmethylbimethoxysilane (L1) in tetrahydrofuran at room temperature gave a mononuclear ruthenium(II) complex [Ru(PPh3)2Cl2 (κ2-N,N-L1)] (1). Condensation of γ-aminopropyltriethoxysilane and potassium diphenylphosphine in the molar ratio of 1:1 in tetrahydrofuran afforded phosphine (PPh2)(CH2)3Si(OEt)3 (L2) with ethoxysilane groups. Reaction of [Ru(η6-p-cymene)Cl2]2 with L2 in refluxing tetrahydrofuran afforded a ruthenium(II) phosphine complex [Ru(η6-p-cymene)Cl2(κ-P-L2)] (2). Complexes 1 and 2 were systematically characterized by microanalyses, FT-IR, and NMR spectroscopies. Their structures have been unambiguously established by single-crystal X-ray diffraction. Immobilization of 1 and 2 on SBA-15 and characterization of these hybrid heterogeneous catalysts were studied by transmission electron microscopy (TEM), FT-IR, and low-pressure N2 adsorption/desorption measurements. Transfer hydrogenation of acetophenone was also briefly investigated with the heterogeneous catalysts.

Enantioselectivity Enhanced on LDH Layers in Ruthenium Catalyzed Asymmetric Hydrogenation of Acetophenone

AbstractA novel heterogeneous catalyst has been developed by immobilizing Ru complexes on layered double hydroxide (LDH) via an electrostatic adsorption method. The prepared hybrid was characterized by a series of physical and chemical techniques, and the results confirmed the successful immobilization of the Ru complexes on the LDH support. The prepared heterogeneous Ru catalyst was found to be more enantioselective than the corresponding homogeneous analogue in the asymmetric hydrogenation of acetophenone and its ee value was 10% higher than that of the homogeneous analogue. Furthermore, the prepared heterogeneous catalyst could be recovered easily and reused at least six times without a significant loss in catalytic activity and selectivity. Density functional theory (DFT) computations revealed the influence of LDH layer on Ru complexes and the enantioselectivity of the immobilized Ru complexes in asymmetric hydrogenation of acetophenone.

Asymmetric transfer hydrogenation of acetophenone using bis-imine rhodium complexes: Kinetic study and modeling

Asymmetric transfer hydrogenation of acetophenone (APh) to (R)-1-phenylethanol (PhE) was studied in 2-propanol solution in the presence of Rh(1,5-COD)(μ-Cl)]2+L, where COD = cyclooctadiene and L is a bis-aldimine ligand based on (R,R)-1,2-cyclohexanediamine and pyridinecarboxaldehyde. This rhodium (I) complex bearing optically active ligands achieved a maximum turnover frequency (TOF) of 268 h−1 at 78 °C and a moderate maximum enantioselectivity (ee) of 55 % for (R)-1-PhE. A formal kinetic study of the process was carried out using the Rh(1,5-COD)(N,N'-(R,R)-1,2-cyclohexane-1,2-diyl-bis-(1-(pyridine-2-yl)-methanimine)-Cl complex. The induction period for catalyst activation is proposed to involve the rapid reaction of the pre-catalyst with excess iso-propoxide to give the catalytically active Rh(1,5-COD)(N,N'-(R,R)-1,2-cyclohexane-1,2-diyl-bis-(1-(pyridine-2-yl)-methanimine)-OiPr, which leads to the transfer hydrogenation of 1,5-COD. Reaction profiles were obtained by varying the initial concentrations of APh, pre-catalyst, base, acetone, and the temperature. These data were fitted to a kinetic model for the proposed mechanism, and numerical simulation led to a set of rate constants and thermodynamic parameters.

Asymmetric Transfer Hydrogenation of Arylketones Catalyzed by Enantiopure Ruthenium(II)/Pybox Complexes Containing Achiral Phosphonite and Phosphinite Ligands.

A family of complexes of the formula trans-[RuCl2(L)(R-pybox)] (R-pybox = (S,S)-iPr-pybox, (R,R)-Ph-pybox, L = monodentate phosphonite, PPh(OR)2, and phosphinite, L = PPh2(OR), ligands) were screened in the catalytic asymmetric transfer hydrogenation of acetophenone, observing a strong influence of the nature of both the R-pybox substituents and the L ligand in the process. The best results were obtained with complex trans-[RuCl2{PPh2(OEt)}{(R,R)-Ph-pybox}] (2c), which provided high conversion and enantioselectivity (up to 96% enantiomeric excess, e.e.) for the reduction of a variety of aromatic ketones, affording the (S)-benzylalcohols.

Continuous Production Using a T-Shaped Micro/Milli-Reactor for RUCY-Catalyzed Asymmetric Hydrogenation of Acetophenone

Continuous Production Using a T-Shaped Micro/Milli-Reactor for RUCY-Catalyzed Asymmetric Hydrogenation of Acetophenone

Highly selective hydrogenation of acetophenone over supported amorphous alloy catalyst

AbstractAlpha‐phenylethanol (PE) is an essential chemical in the field of medicine and synthetic perfumery. Therefore, in this work, we used a supported Ni–B–P amorphous alloy catalyst (Ni–B–P/SiO2) in the hydrogenation of acetophenone (AP) to α‐PE, which demonstrated excellent catalytic activity and selectivity, compared with Ni–B/SiO2 (KBH4 reduction of nickel salt). Ni–B–P/SiO2 exhibited a high AP hydrogenation conversion of approximately 99%, whereas the PE selectivity reached up to 94%, which is approximately 1.4‐fold higher than that of Ni–B/SiO2 (about 69%), thereby directly proving the unique inhibition of AP hydrogenation over hydrogenation of P in the Ni–B catalytic system. The doped P in Ni–B–P/SiO2 enhances the oxidation resistance and maintains the valence stability of Ni and B. Furthermore, sufficient experimental data were collected to determine the kinetic parameters. Based on the Langmuir–Hinshelwood model, we assumed that (i) AP and H2 compete for adsorption on Ni–B–P/SiO2; (ii) AP has strong adsorptive capacity on Ni–B–P/SiO2; and (iii) PE coverage on the catalyst was negligible. Then, the dynamic equation was derived, which indicated that experimental data agree well with the dynamic model. Finally, the activation energy was confirmed to be 50.73 KJ/mol. This report will open up an avenue for the industrialization of amorphous alloy catalysts.

Synthesis and catalytic activities of bimetallic Ru (II) arene complexes bearing bis-benzimidazoles

In this study, bis-benzimidazole ligands (1a-d) were synthesized using linker groups and they were evaluated as catalyst generated in situ from [RuCl2(p-cymene)]2 for transfer hydrogenation (TH) of acetophenone. The bimetallic Ru (II) arene complex (2b) synthesized from ligand 1b which showed the best activity among the ligands in the catalytic TH reaction. The obtained ligands and 2b complex were characterized by 1H- and 13C-NMR, elemental analysis and IR spectroscopy. The catalytic activities of complexes having different chain lengths and Y (CH3 or H) groups were compared. The highest conversion (99%) was obtained with 2b.0000-0002-7422-6593

Strong Solvent Effects on Catalytic Transfer Hydrogenation of Ketones with [Ir(cod)(NHC)(PR3)] Catalysts in 2-Propanol-Water Mixtures

The synthesis and characterization of the new Ir(I)-complexes [IrCl(cod)(Bnmim)], [Ir(cod)(emim)(PPh3)]Cl and [Ir(cod)(Bnmim)(mtppms)] are reported. The zwitterionic complexes [Ir(cod)(NHC)(mtppms)] and Na2[Ir(cod)(NHC)(mtppts)] (NHC = emim, bmim or Bnmim; mtppms-Na and mtppts-Na3 = sodium salts of mono- and trisulfonated triphenylphosphine, respectively) were found to be effective precatalysts for transfer hydrogenation of aromatic and aliphatic ketones in basic 2-propanol-water mixtures with initial turnover frequencies up to 510 h−1 at 80 °C, and their catalytic performances were compared to those of [IrCl(cod)(NHC)] complexes (NHC = emim, bmim, Bnmim, IMes) and [Ir(cod)(emim)(PPh3)]Cl. Three of the catalysts were characterized by single-crystal X-ray diffraction. The reaction rates of the transfer hydrogenation of acetophenone and benzophenone showed strong dependence on the water concentration of the solvent, indicating preferential solvation of the catalytically active metal complexes.

Synthesis and Catalytic Application of Knölker-Type Iron Complexes with a Novel Asymmetric Cyclopentadienone Ligand Design

Asymmetric catalysis is an essential tool in modern chemistry, but increasing environmental concerns demand the development of new catalysts based on cheap, abundant, and less toxic iron. As a result, Knölker-type catalysts have emerged as a promising class of iron catalysts for various chemical transformations, notably the hydrogenation of carbonyls and imines, while asymmetric versions are still under exploration to achieve optimal enantio-selectivities. In this work, we report a novel asymmetric design of a Knölker-type catalyst, in which the C2-rotational symmetric cyclopentadienone ligand possesses chiral substituents on the 2- and 5-positions near the active site. Four examples of the highly modular catalyst design were synthesized via standard organic procedures, and their structures were confirmed with NMR, IR, MS, and polarimetry analysis. Density functional theory (DFT) calculations were conducted to elucidate the spatial conformation of the catalysts, and therewith to rationalize the influence of structural alterations. Transfer- and H2-mediated hydrogenations were successfully established, leading to appreciable enantiomeric excesses (ee) values up to 70%. Amongst all reported Knölker-type catalysts, our catalyst design achieves one of the highest ee values for hydrogenation of acetophenone and related compounds.

Hydrogenation Performance of Acetophenone to 1-Phenylethanol on Highly Active Nano Cu/SiO2 Catalyst

In this work, highly active nano Cu/SiO2 catalysts with various copper content were prepared by urea homogeneous precipitation method. The catalysts were characterized by N2 adsorption, XRD, H2-TPR, XPS and TEM. It was found that the nano Cu/SiO2 catalyst displayed excellent catalytic performance for the selective hydrogenation of acetophenone (AP) to 1-phenylethanol (PhE) when copper content was 25 wt%. The Cu/SiO2 catalyst had well dispersed copper species, small particle size, high BET surface area (ca. 540 m2/g) and abundant pore structure. The influence of different reaction conditions on the hydrogenation process were also discussed. AP conversion and the PhE selectivity reached 99.8% and 99.08%, respectively, under the optimal reaction conditions (Temperature: 353 K; Pressure: 2.0 MPa, LHSV: 1.0 h−1 and the molar ratio of H2/AP:15). Besides, the above catalyst maintained a high catalytic performance in the duration of 500 h operation. The synergistic effect between Cu+ and Cu0 improved the activity and stability of Cu/SiO2 catalyst. The research indicated that the catalyst had a wide industrial prospect. The Cu/SiO2 catalyst showed a good performance for AP hydrogenation. The reduced Cu/SiO2 catalyst contains both Cu+ and Cu0 consistent with XPS. Cu+ sties stabilize the methoxy and acyl species and Cu0 facilitates the decomposition of H2. Phenyl in AP and Cu had electrostatic repulsion, which was favorable for desorption of PhE.

Asymmetric ruthenium tricarbonyl cyclopentadienone complexes; synthesis and application to asymmetric hydrogenation of ketones

A series of enantiomerically-pure ruthenium tricarbonyl cyclopentadienone complexes were prepared via the cyclisation of C2-symmetric dialkynes with Ru3(CO)12. Four complexes were characterised by X-ray crystallography and a hydride derivative of one of these was characterised. The complexes were tested in the asymmetric hydrogenation and transfer hydrogenation of acetophenone. Whilst the catalysts were active, acetophenone was reduced in low ee, however a reduction product of up to 46% ee could be obtained when a mild base (iPr2NEt or pyridine) was added to the reaction.

Study of nano‐Cu/SiO2 catalysts for highly selective hydrogenation of acetophenone

Hydrogenation of acetophenone over nano‐Cu/SiO2 catalysts was investigated. The catalysts, prepared by a liquid precipitation method using various precipitating agents, were characterized using low‐temperature nitrogen adsorption, X‐ray diffraction, temperature‐programmed desorption of ammonia, hydrogen temperature‐programmed reduction, transmission electron microscopy and X‐ray photoelectron spectroscopy. It was found that the catalysts prepared by a homogeneous precipitation method had better activity and stability than those prepared by a co‐precipitation method. The catalyst prepared using urea as precipitating agent had well‐dispersed copper species, high surface area and abundant pore structure. The catalytic performance and mechanism of the Cu/SiO2 catalysts were further studied. It was found that the activity and stability of the catalysts could be improved by adjusting the proportion of Cu+/(Cu+ + Cu0). The sample prepared using urea as precipitating agent presented higher activity and selectivity. Also, the catalyst prepared using urea maintained a high catalytic performance while being continuously used for 150 h under the optimal reaction conditions.