Hydrogenation Of Acetophenone Research Articles

Synthesis, structures, and properties of manganese(i) complexes featuring tridentate amidine-toting protic amine ligands

Cationic Mn(CO)3 complexes having a protic amine ligand with cyclic amidine side arms were prepared and their catalytic properties of transfer hydrogenation of acetophenone and electrochemical reduction of CO2 were compared.

SYNTHESIS OF NOVEL BIS(PHOSPHINO)AMINE-RUII(ACAC)2 COMPLEXES, AND INVESTIGATION OF CATALYTIC ACTIVITY IN TRANSFER HYDROGENATION

In this study, reactions of (PPh2)2NCH2CH2N(PPh2)2 (L1) and {(PPh2)2NCH2CH2}3N (L2) with [RuII(acac)2(CH3CN)2] led to the production of new dinuclear complex [Ru(acac)2]2(L1) (1) and trinuclear complex [Ru(acac)2]3(L2) (2). Complex 1 and 2 are excellent candidates for the role of catalyst precursors in the transfer hydrogenation (TH) of acetophenone and its derivatives. Compared to complex (1), the trinuclear complex (2) is an exceptional catalyst, producing the corresponding alcohols in 98–99% yields in 20 minutes at 80 oC (TOF≤300 h-1) for the TH process. A comparison of the catalytic properties of the complexes is also briefly discussed. Complex structures have also been characterized by combining nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR), and elemental analysis.

N,S-heterocyclic carbene containing benzothiazol-2-ylidene-Ru(II) and Pd(II) new complexes functionalized with butyl linked carbazole moiety: Synthesis, characterization and their catalytic efficiency and electropolymerizations

In contrast to the large number of polymeric N-heterocyclic carbenes (NHCs) there are relatively few examples of NHCs-containing conductive polymers. However, conducting polymers (CPs) could be excellent hosts for NHC compounds, as they can easily form polymer films electrochemically, and their optical & electrical properties can be easily tuned by electrochemically or changing bonding groups in their structure. In this work, the N,S-heterocyclic carbene (NHC) ligand precursor, N-(4-butylcarbazole)benzothiazolium bromide (1) was prepared by solvent-free alkylation of benzothiazole by 9-(4-bromobutyl)carbazole with high efficiency. The air- and moisture-stable new piano-stool Ru(II)-N,S-NHC (2) and PEPPSI type Pd(II)-N,S-NHC (3) complexes, were synthesized and characterized by 1H- and 13C NMR, FT-IR, UV–vis and ESI-MS spectroscopic methods and elemental analysis. Further confirmations of structural details for benzothiazolium salt (1) and its Ru(II)-N,S-NHC complex (2) were determined by X-ray single-crystal diffraction. The catalytic performance of the complexes (2 and 3) in transfer hydrogenation (TH) of acetophenone and Suzuki–Miyaura cross-coupling reactions of aryl bromides were also investigated, respectively. All compounds (1–3) were electrochemically polymerized and conducting polymer films with pendant carbene complex moieties were obtained. The electrical and optical properties of the resulting polymers were characterized via spectroelectrochemical studies.

Tuning the catalytic performance of Pt/SiO2 catalysts by CoOx modification for selective hydrogenations of unsaturated carbonyl compounds

Tailoring the interface between active metals and promoters to improve catalytic performance is a challenging issue for bicomponent catalysts. Herein, we developed a series of silica supported Pt-CoOx hybrid nanocatalysts though in situ oxidation of supported bimetallic PtCo nanoparticles (NPs) with different Pt/Co ratios. Focusing on the hydrogenation of acetophenone to 1-phenylethanol as the model reaction, the obtained Pt-CoOx/SiO2 catalysts showed superior activity and selectivity compared to Pt/SiO2, and the sample with a Co/Pt molar ratio of 1/3 performed the best. Our research showed that the CoOx on Pt not only changed its electronic and geometric properties, but also promoted the adsorption of reactants and the dissociation of H2. A further increase of the Co/Pt ratio to 1/1, however, reduced the activity due to blockage of the Pt surface.

Highly Active Large Au Clusters and Even More Active Ag Nanoparticles Supported on Ceria-Zirconia: Impact of Particle Size and Potassium Ion Loading on Activity in Catalytic Transfer Hydrogenation

Although heterogeneous monometallic gold catalysts are commonly more active when the gold particles are smaller, this study shows that the reverse is true in the case of liquid phase catalytic transfer hydrogenation of acetophenone with 2-pentanol. Higher catalytic activity of larger gold particles, i.e., over 30 nm in diameter, than of smaller particles of average 4 nm in size was observed. Moreover, this effect was contradictory to that observed for supported monometallic silver catalysts in which the interaction with the support and hence particle size was shown to cause drastic changes in the activity in this reaction, with the large particles being completely inactive and tiny ones being the most active system studied. In this reaction, the ceria-zirconia solid solutions were used as the supports for the catalysts and both zirconium doped ceria, as well as cerium doped zirconia carriers were tested. The supports themselves exhibited little activity in this reaction. It was shown that the activity of the supports and catalysts depends on the Ce/Zr ratio and potassium content. Both types of catalysts showed excellent selectivity to 1-phenylethanol and conversion of acetophenone, although it was noted that a high loading of potassium carbonate in the gold catalysts propelled undesired reactions, thereby reducing the selectivity to 1-phenylethanol.

Cyclopentadienone Iron Complex-Catalyzed Hydrogenation of Ketones: An Operando Spectrometric Study Using Pressurized Sample Infusion-Electrospray Ionization-Mass Spectrometry

The sulfonate charge-tagged cyclopentadienone iron complexes [FeR(MeCN)(CO)2-SO3]Na (R = TMS, tBu) were prepared and used for mechanistic investigations using pressurized sample infusion-electrospray ionization-mass spectrometry in the hydrogenation of acetophenone. Reactions were conducted in a mixed aqueous/alcoholic solvent. Based on kinetic and mass spectrometric experiments, information about the operating reaction mechanism was obtained. Furthermore, analysis of the kinetic profiles and mass spectra indicated catalyst decomposition. By analysis of the mass spectrometric results, the decomposition cascade was found to start by solvolysis of the trimethylsilyl (TMS) groups flanking the carbonyl group in the cyclopentadienone ligand of the catalyst. Subsequent dimerization, comproportionation to form Fe(I) radical species, and formation of catalytically inactive iron tricarbonyl species were observed, limiting the catalyst lifetime. Replacement of the TMS groups by non-hydrolyzable tert-butyl groups leads to a significant increase in the observed turnover frequency and catalyst longevity. The turnover number, determined to be approximately 65 under standardized reaction conditions, could be increased to >1000 by the mechanism-guided structural change in the catalyst. No compounds corresponding to Fe(I) species or dimerization products could be identified in this case. The present study suggests that for hydrogenations with cyclopentadienone iron complexes, the use of alkyl groups flanking the C═O double bond in the ligand is beneficial over the use of silyl groups when conducted in aqueous media.

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.

The influence of complexing agents on the cobalt-based catalysts properties and activities

In this study, CoAl2O4 samples were synthesized using sol–gel method in the presence of citric acid (CoAlCA), malic acid (CoAlMA), oxalic acid (CoAlOA) and urea (CoAlU) as complexing agents. The presence of cubic spinel structure for both CoAl2O4 and Co3O4 phases was confirmed by XRD. FTIR analysis emphasized that the composition of Co3+ ions decreased in order: CoAlOA (50.3 %) > CoAlU (41.8 %) > CoAlMA (40.7 %) > CoAlCA (24.3 %), which denotes that the presence of oxalic acid as complexation agent favors cobalt oxidation from Co2+ to Co3+ and, consequently, the expansion of Co3O4 phase. In the presence of citric acid, as a complexing agent, tetrahedral Co2+ ions prevailed and CoAl2O4 is the dominant phase.The catalytic performances of CoAl2O4 spinel oxides have been evaluated in lactonization of 1,4-butanediol, coupled with acetophenone hydrogenation and in the Claisen-Schmidt condensation reaction of benzaldehyde with acetophenone and the results provided a good relationship between Co3+/Co2+ ratio, the reactants conversion and the products yield.

Promoting effects of residual poly(vinyl alcohol) capping agent on the activity and chemoselectivity of Pt/Al2O3 for catalytic hydrogenation

Capping agents are key to the colloidal synthesis of size- and shape-controlled nanoparticles (NPs) for catalysis. The capping agents on the NP surface are generally removed after synthesis to expose the catalytically active sites. However, the total removal of the capping agents results in the loss of the ability of the capped NPs to regulate the adsorption mode of the reactants, which can, in some cases, decrease selectivity. Here, poly(vinyl alcohol) (PVA)-capped Pt/Al2O3 are prepared and the amount of PVA capping agent remaining on the NP surfaces is controlled by heat treatment to take full advantage of capped NPs. Compared to a surface-clean Pt catalyst, those covered in PVA residues having partially exposed metal sites show enhanced activity and selectivity for the hydrogenation of acetophenone to 1-phenylethanol. Detailed characterization reveals that the promoting effects of the residual PVA are attributed to the combined contributions of electronic modification of the Pt surface, selective exposure of highly active Pt defect sites, and steric hindrance with the aromatic ring of acetophenone. This study offers insights into the roles of residual capping agents in heterogeneous catalysis and provides a new strategy for enhancing the performance of nanocatalysts using capped NPs.

NiOBDP and Ni/NiOBDP catalyzed transfer hydrogenation of acetophenone and 4-nitrophenol

The NiOBDP and Ni/NiOBDP composites obtained by calcination of NiBDP MOF (MOF = metal–organic framework; BDP = 1,4-Bis(pyrazol-4-yl)benzene) in air at 700 °C were characterized by XRD (X-ray diffraction), TEM (Transmission electron microscopy), XPS (X-ray photoelectron spectroscopy) and Raman spectroscopy. Both nanocatalysts presented high activity in selective transfer hydrogenation of acetophenone (APh) and 4-nitrophenol (4-NP) in mild conditions, using 2-propanol/NaOH or NaBH4/H2O as reducing agents. In both reactions, the catalytic activity of Ni/NiOBDP was higher compared to NiOBDP suggesting the participation of Ni(0) in the hydrogenation process.

Hydrogenation of imines catalyzed by ruthenium(II) complexes containing phosphorus-nitrogen ligands via hydrogen transfer reaction

This work describes the synthesis and characterization of Ru(II) compounds with general formula cis-Cl- cis-P cis-N- RuCl2(PN)2 (where PN represents a heterobidentate PN-donor chelated ligand) and their application as catalysts in the reduction of acetophenone and imines hydrogenation via hydrogen transfer reaction using 2-propanol as the hydrogen source. Single crystal diffraction analysis for all synthesized ruthenium complexes shows non-regular octahedral coordination around the metal. All the synthesized Ru(II) complexes achieved high conversions and turnover frequencies in hydrogen transfer reaction to acetophenone (830 h−1) and imine hydrogenation (760 h−1 for N-benzylideneaniline). The complex (dichloro bis-(8-(diphenylphosphino)quinoline)ruthenium(II)) (RuL2) achieved high conversion in imine hydrogenation, while the complex(dichloro bis-(N-(diphenylphosphino)pyridin-2-amine)ruthenium(II)) (RuL3) showed high conversion in acetophenone reduction. It was found that the electronic, structural, and steric properties of the ligands could influence catalytic performance.

Efficient Catalytic Transfer Hydrogenation of Acetophenone to 1-Phenylethanol over Cu–Zn–Al Catalysts

Cu–Zn–Al catalyst was prepared by the co-precipitation method, and the catalytic performance for transfer hydrogenation of acetophenone (AP) to 1-phenylethanol (1-PhE) was evaluated using isopropanol (IPA) as a hydrogen source. The addition of Zn changed the morphology of the catalyst and reduced aggregation of catalyst particles, resulting in highly dispersed Cu active sites. As the Zn content increased, the valence state of Cu species changed. When the Cu/Zn molar ratio was 2/3, the Cu+/Cu0 ratio in the catalyst was 0.81, resulting in good selectivity for 1-PhE. The reaction conditions were optimized over the Cu–Zn–Al catalyst with a Cu/Zn molar ratio of 2/3. When the reaction was performed at 180 °C for 2 h with an IPA/AP molar ratio of 15, the AP conversion was 89.4% and the 1-PhE selectivity was 93.2%. The Cu–Zn–Al catalyst showed good stability, and AP conversion and the 1-PhE selectivity were essentially unchanged after five cycles.

The promotion effect of \u03c0-\u03c0 interactions in Pd NPs catalysed selective hydrogenation

The utilization of weak interactions to improve the catalytic performance of supported metal catalysts is an important strategy for catalysts design, but still remains a big challenge. In this work, the weak interactions nearby the Pd nanoparticles (NPs) are finely tuned by using a series of imine-linked covalent organic frameworks (COFs) with different conjugation skeletons. The Pd NPs embedded in pyrene-COF are ca. 3 to 10-fold more active than those in COFs without pyrene in the hydrogenation of aromatic ketones/aldehydes, quinolines and nitrobenzene, though Pd have similar size and surface structure. With acetophenone (AP) hydrogenation as a model reaction, systematic studies imply that the π-π interaction of AP and pyrene rings in the vicinity of Pd NPs could significantly reduce the activation barrier in the rate-determining step. This work highlights the important role of non-covalent interactions beyond the active sites in modulating the catalytic performance of supported metal NPs.

Photocatalytic hydrogenation of acetophenone on a titanium dioxide cellulose film.

A previously developed sustainable immobilization concept for photocatalysts based on cellulose as a renewable support material was applied for the photocatalytic hydrogenation of acetophenone (ACP) to 1-phenyl ethanol (PE). Four different TiO2 modifications (P25, P90, PC105, and PC500) were screened for the reaction showing good performance for PC25 and PC500. PC500 was selected for a detailed kinetic study to find the optimal operating conditions, and to obtain a better understanding of the photocatalytic pathway in relation to conventional and transfer hydrogenation. The kinetic data were analyzed using the pseudo-first-order reaction rate law. A complete conversion was obtained for ACP concentrations below 1 mM using a 360 nm filter and argon as the purge gas within 2–3 hours. High oxygen concentrations slow down or prevent the reaction, and wavelengths below 300 nm lead to side-products. By investigating the temperature dependency, an activation energy of 22 kJ mol−1 was determined which is lower than the activation energies for conventional and transfer hydrogenation, because the light activation of the photocatalyst turns the endothermic to an exothermic reaction. PC500 was immobilized onto the cellulose film showing a 37% lower activity that remains almost constant after multiple use.

Catalyst characterization Ni-Sn nanoparticles supported in Al2O3and MgO: Acetophenone hydrogenation

Monometallic and bimetallic Ni and Sn catalysts were prepared in different ratios by the Solvated Metal Atom Dispersed (SMAD) method for the catalytic hydrogenation of acetophenone to 1-phenylethanol. The preparation of the catalysts was carried out by evaporation of Ni and Sn metal atoms and subsequent co-deposition at 77 K using 2- isopropanol as solvent on alumina and magnesium oxide as supports. X-ray photoelectron spectroscopy (XPS) analysis showed a high percentage of nickel atoms in zero valence, while the tin phases were founded in reduced and oxidized form. The average size of the nanoparticles measured by transmission electron microscopy (TEM) ranged from 8 to 15 nm while the metal dispersion on the surface measured by hydrogen chemisorption ranged from 0.07% for Ni1% Sn0.3%/MgO to 3.2% for Ni5%/MgO. Thermogravimetric analysis shows that γ-Al2O3catalysts exhibit higher thermal stability than MgO catalysts. The catalysis results showed that the best support is MgO reaching 66% conversion in Ni5% Sn0.5%/MgO catalyst.

Ni@C catalyzed hydrogenation of acetophenone to phenylethanol under industrial mild conditions in a flow reactor

The catalytic hydrogenation of organic substrates containing plenty of unsaturated functional groups is an important step in the industrial preparation of fine chemicals and has always been a hot spot in basic catalysis research.

Heterogeneous Enantioselective Hydrogenation of Ketones by 2-Amino-2′-hydroxy-1,1′-binaphthyl-Modified CeO2-Supported Ir Nanoclusters

Modification of supported noble metals with chiral modifiers is a promising strategy for the design of effective heterogeneous chiral catalysts. The chiral compounds are generally introduced on the surface of noble metals, often leading to low enantioselectivity and to low activity. Herein, a unique heterogeneous chiral catalyst where a chiral modifier is introduced at the interface between the metal cluster and the support is presented. Modification of CeO2-supported Ir nanoclusters with 2-amino-2′-hydroxy-1,1′-binaphthyl (NOBIN) as a chiral modifier provided a heterogeneous chiral catalyst where NOBIN is introduced at the interface between Ir nanoclusters and the CeO2 support. The heterogeneous chiral catalyst enabled the asymmetric hydrogenation of acetophenone to provide 1-phenylethanol with moderate enantiomeric excess (ee) (up to 53%). The catalyst characterizations showed that about 1 nm Ir metal nanoclusters are formed on CeO2, and density functional theory calculations presented that NOBIN is adsorbed onto Ir nanoclusters and CeO2 at the NH2 and OH groups, respectively, constructing the asymmetric reaction field among NOBIN, Ir nanoclusters, and CeO2.

Mechanochemical, Water‐Assisted Asymmetric Transfer Hydrogenation of Ketones Using Ruthenium Catalyst

AbstractAsymmetric catalytic reactions are among the most convenient and environmentally benign methods to obtain optically pure compounds. The aim of this study was to develop a green system for the asymmetric transfer hydrogenation of ketones, applying chiral Ru catalyst in aqueous media and mechanochemical energy transmission. Using a ball mill we have optimized the milling parameters in the transfer hydrogenation of acetophenone followed by reduction of various substituted derivatives. The scope of the method was extended to carbo‐ and heterocyclic ketones. The scale‐up of the developed system was successful, the optically enriched alcohols could be obtained in high yields. The developed mechanochemical system provides TOFs up to 168 h−1. Our present study is the first in which mechanochemically activated enantioselective transfer hydrogenations were carried out, thus, may be a useful guide for the practical synthesis of optically pure chiral secondary alcohols.

Synthesis of Ruthenium Catalysts with a Chiral Arene Ligand Derived from Natural Camphor

AbstractA ruthenium complex with a chiral arene ligand [(camphor–arene)RuCl2]2 was synthesized by the reaction of RuCl3·nH2O with a chiral diene which was obtained from natural camphor in three steps. This complex catalyzed the asymmetric hydrogenation of acetophenone (64–85% ee), but decomposed in catalytic reactions involving C–H activation of 2-phenylpyridine or benzoic acid derivatives.

Cationic half-sandwich ruthenium (II) complexes ligated by pyridyl-triazole ligands: Transfer hydrogenation and mechanistic studies

A series of novel cationic ruthenium half-sandwich complexes, bearing 1-substituted-4-pyridyl-1H-1,2,3-triazole ligands, were synthesized and fully characterized by a range of analytical techniques. The complexes were found to be efficient catalyst precursors for transfer hydrogenation reactions using ketones as substrates. We demonstrated that the complexes could hydrogenate acetophenone in excellent conversions (∼75 %) within 3 h, employing a low concentration of base of only 2 mol %. Extending the reaction time to 6 h gave near quantitative conversions for both catalysts employed. In addition to this, the transfer hydrogenation of acetophenone was also found to proceed even at low catalyst loadings (0.025–0.05 mol%) and low base concentrations (0.25–1.0 mol%). Under these conditions substrate conversion was moderate (22–60 %). The catalytic efficiency of the most effective catalyst was then evaluated in the transfer hydrogenation of a small library of aromatic and aliphatic ketones. It was shown that more challenging substrates such as benzophenone and 2-octanone could be hydrogenated to the corresponding secondary alcohols in conversions > 90 %. Finally, based on several experimental observations, a possible mechanism for the process is proposed.