Catalytic Transfer Hydrogenation Research Articles

Catalytic transfer hydrogenation of α-angelica lactone over Nickel(II) modified UiO-66 metal organic framework under mild conditions

In the realm of biomass valorization, catalysts play a pivotal role, and UiO-66(Zr), a type of metal organic framework (MOF), emerges as a promising heterogeneous catalyst. This study focuses on incorporating Ni2+ into UiO-66(Zr) for application in catalytic transfer hydrogenation (CTH) of bio-derived α-angelica lactone (a-AL) to ɣ-valerolactone (GVL). The synthesis of UiO-66(Zr) occurs through a solvothermal process at 120 °C for 24 h. Ni(II) modification, achieved through wet impregnation with loadings of 2.5 and 5.0 wt%, results in no observable diffraction peaks associated with Ni particles in XRD analysis. FTIR analysis indicates significant shifts, suggesting deprotonation of the carboxylic moiety from the ligand and coordination with Zr4+ metal ion. Nitrogen sorption isotherms show a reduction in surface area and pore volume upon Ni(II) incorporation. FESEM analysis reveals particle agglomeration and increased size with Ni(II) introduction. EDX and HRTEM confirm the presence of 0.9 and 1.8 wt% Ni(II) on UiO-66(Zr). TG/DTA analysis affirms that Ni(II) does not affect the thermal stability of UiO-66(Zr). Ultimately, the introduction of Ni(II) enhances the catalytic performance of UiO-66(Zr), increasing the conversion and selectivity towards ɣ-valerolactone from 67 to 83.3 % and 71.6 % to 97.4 %, respectively, under mild reaction conditions.

A combo Zr–zeolite and Zr(OH)4 mixture composition for one–pot production of γ–valerolactone from furfural

The one–pot cascade transformation of biomass–derived furfural (FUR) to γ–valerolactone (GVL) has attracted great attention but always facing relative low reaction rates. In this work, a combo ZrO2 supported on ZSM–5 nanosheet (ZrO2/NS) and Zr(OH)4 were mixed as a hybrid catalysts system, which was prepared by impregnation and precipitation, respectively. Then the catalytic system was used for conversion of FUR to produce GVL through catalytic transfer hydrogenation in isopropanol. NS zeolite with hierarchical pores promoted the dispersion of ZrO2 and exposed surface assisted the conversion of FUR to isopropyl levulinate (IPL). Moreover, the addition of Zr(OH)4 facilitated the cascade transformation of the intermediate IPL to GVL through the enhanced adsorption of IPL and isopropanol with the cooperation of basic sites. The ZrO2/NS and Zr(OH)4 catalyst system with optimized proportion delivers >90 wt% yield of GVL at 180 °C after 2h reaction, with generation rates of GVL (RGVL) up to 9.2 mmol g−1 h−1.

Alkaline modified Zr-loading on nanosheet zeolite towards production of γ-valerolactone from levulinic acid through catalytic transfer hydrogenation

A self-pillared nanosheet ZSM-5 zeolite (SP) loading Zr catalyst is prepared for conversion of levulinic acid (LA) to produce γ-valerolactone (GVL). The hierarchical pore by nanosheet aggregates promotes Zr dispersion with establishment of strong interaction between Zr and zeolite. Moreover, Na ions are introduced to modify the chemical environment of Zr on nanosheet zeolite (Zr/NaSP). In catalytic transfer hydrogenation of LA using isopropanol as H-donor, uniformly dispersed Zr species on SP zeolite is conducive for both conversion of LA as well as production of GVL, in comparison with samples using conventional microporous ZSM-5 as supports (Zr/CZ). More importantly, different from protonated zeolite sample (Zr/HSP), the introduction of alkali sites could attract protons in hydroxyl groups of isopropanol, which accelerates the generation rates of GVL. The as-designed Zr/NaSP catalyst delivers GVL generation rates of 31.9 mmol·g-1·h-1, which provides a potential catalyst for GVL production.

Methyl Formate, an Alternative Transfer Hydrogenating Agent for Chemoselective Reduction of N-Heteroarenes and Azoarenes.

The search for efficient molecular hydrogen precursors and their catalytic exploration is necessary for the evolution of catalytic transfer hydrogenation. Methyl formate (MF) having high hydrogen content still remains unexplored for such transformations. Herein, we disclosed a bifunctional Ir(III)-complex catalyzed chemoselective TH protocol for N-heteroarenes and azoarenes using MF. A variety of substrates including ten bioactive molecules have been synthesized under mild reaction conditions. A probable mechanistic pathway was proposed based on control experiments and mechanistic studies.

Tandem hydrogenation/hydrogenolysis of furfural to 2-methylfuran over multifunctional metallic Cu nanoparticles supported ZIF-8 catalyst

Catalytic transfer hydrogenation (CTH), that employs protic solvents as hydrogen sources to alleviate the use of molecular hydrogen H2, has gained great attention. This work, reports multifunctional, metallic Cu nanoparticles supported ZIF-8 material for CTH of furfural to a highly valued fuel additive, 2-methylfuran (2-MF) using 2-propanol. Of all as-synthesized xCu(yM)/ZIF-8 catalysts with varied NaBH4 concentration (yM) and Cu loading (x), 11Cu(1.5 M)/ZIF-8 exhibited higher catalytic activity with > 99 % FAL conversion and 93.9 % 2-MF selectivity. This is ascribed to its high specific surface area, and existence of optimum amount of Lewis acid-base sites along with Cu0 species, which are responsible for hydrogenation of furfural to furfuryl alcohol and subsequent hydrogenolysis to produce 2-MF. The present work reports a highly efficient and stable, metal-MOF hybrid material for CTH of FAL to 2-MF, which is one among the best reports available in literature, therewith suggests a promising approach for bio-oil upgradation.

Heteropolyacid promoted lignin-MOF derived spherical catalyst for catalytic hydrogen transfer of 5-hydroxymethylfurfural

Catalytic conversion of biomass-derived value-added chemicals was of great significance for the utilization of renewable biomass resources to instead of fossil chemicals. Biomass-derived lignin was regarded as an important support and 5-hydroxymethylfurfural (HMF) was a vital platform chemical derived from cellulose. Herein, a series of lignin-MOF hybrid catalysts were prepared and modified with different heteropolyacids (HPAs), which were then successfully introduced into the selective conversion of HMF to 5-hydroxymethylfurfuryl alcohol (MFA). The effect of different HPA, calcination temperature, etc. were all studied, and all catalysts were well characterized. It was confirmed that silicotungstic acid modified catalyst (Ni3Co-MOF-LS@HSiW) exhibited the best catalytic performance, while the highest conversion of HMF was up to 100%, with the best MFA yield of 86.5%. The finding in this study could provide novel insights for the utilization of lignin and preparation of value-added biomass-derived chemicals.

Magnetically Reusable Carbon Nanotube Coated Co‐based Catalysts towards Highly Efficient Transfer Hydrogenation of Nitroarenes

AbstractDevelopment of efficient and stable non‐noble metal catalysts applied to the catalytic transfer hydrogenation of nitroarenes under mild conditions is still challenging. Herein, we report magnetically recyclable catalysts prepared via simple two‐stage pyrolysis of Co‐MOF‐74 and melamine composites. The optimized catalyst Co@C/CNTs‐10‐700 shows excellent conversion and selectivity towards transfer hydrogenation of nitroarenes with different hydrogen donors. Its excellent stability against formic acid corrosion makes it can be used in a wide range. The excellent catalytic performance can be ascribed to the synergistic effect between carbon nanotubes and Co nanoparticles. Furthermore, the catalyst was easily recycled owing to its magnetism and reused up to ten consecutive cycles without significant loss of activity, indicating that the excellent catalytic stability holds great promise in fields of industrial application.

Synthesis, characterisation, and catalytic application of a soluble molecular carrier of sodium hydride activated by a substituted 4-(dimethylamino)pyridine

Recently main group compounds have stepped into the territory of precious transition metal compounds with respect to utility in the homogeneous catalysis of fundamentally important organic transformations. Inspired by the need to promote more sustainability in chemistry because of their greater abundance in nature, this change of direction is surprising since main group metals generally do not possess the same breadth of reactivity as precious transition metals. Here, we introduce the dihydropyridylsodium compound, Na-1,2-tBu-DH(DMAP), and its monomeric variant [Na-1,2-tBu-DH(DMAP)]·Me6TREN, and demonstrate their effectiveness in transfer hydrogenation catalysis of the representative alkene 1,1-diphenylethylene to the alkane 1,1-diphenylethane using 1,4-cyclohexadiene as hydrogen source [DMAP = 4-dimethylaminopyridine; Me6TREN = tris(N,N-dimethyl-2-aminoethyl)amine]. Sodium is appealing because of its high abundance in the earth’s crust and oceans, but organosodium compounds have been rarely used in homogeneous catalysis. The success of the dihydropyridylsodium compounds can be attributed to their high solubility and reactivity in organic solvents.

Microwave-Assisted Transfer Hydrogenation of Carbonyl and ­Nitro Compounds Using Bimetallic Ru(II) Cymene Complexes

AbstractWe report an investigation of the microwave-assisted catalytic transfer hydrogenation (TH) of carbonyl and nitro compounds by employing Ru(II) complexes: bimetallic [(p-cymene)2(RuCl)2L1]2X (X = BF4 (Cat2); X = PF6 (Cat3)) and mononuclear [(p-cymene)(RuCl)L2]BF4 (Cat4) (where L1 = N,N′-(3,3′,5,5′-tetraisopropyl-[1,1′-biphenyl]-4,4′-diyl)bis(1-(pyridin-2-yl)methanimine) and L2 = N-(2,6-diisopropylphenyl)-1-(pyridin-2-yl)methanimine). At a low catalyst loading of 0.01 mol% (Cat2/Cat3), a broad range of substrates, comprising aromatic as well as aliphatic ketones and aldehydes, undergo the TH reaction in a short reaction time of just 10 minutes. Additionally, chemoselective hydrogenation of nitroaromatic compounds is achieved under microwave irradiation in the presence of Cat2 within 5 minutes. Control experiments demonstrate that microwave heating conditions outperform conventional heating in terms of improved catalytic activity and reaction efficiency. The bimetallic catalyst Cat2 is used at a very low loading of 0.001 mol% to achieve high TONs and TOFs of 7.7 × 104 and 2.3 × 105 h–1, respectively, for the TH reaction. Spectrometry experiments involving trapping of intermediates are used to propose a mechanism for the TH of the carbonyl compounds.

Zn Single-Atom Catalysts Enable the Catalytic Transfer Hydrogenation of α,β-Unsaturated Aldehydes.

Highly active nonprecious-metal single-atom catalysts (SACs) toward catalytic transfer hydrogenation (CTH) of α,β-unsaturated aldehydes are of great significance but still are deficient. Herein, we report that Zn-N-C SACs containing Zn-N3 moieties can catalyze the conversion of cinnamaldehyde to cinnamyl alcohol with a conversion of 95.5% and selectivity of 95.4% under a mild temperature and atmospheric pressure, which is the first case of Zn-species-based heterogeneous catalysts for the CTH reaction. Isotopic labeling, in situ FT-IR spectroscopy, and DFT calculations indicate that reactants, coabsorbed at the Zn sites, proceed CTH via a "Meerwein-Ponndorf-Verley" mechanism. DFT calculations also reveal that the high activity over Zn-N3 moieties stems from the suitable adsorption energy and favorable reaction energy of the rate-determining step at the Zn active sites. Our findings demonstrate that Zn-N-C SACs hold extraordinary activity toward CTH reactions and thus provide a promising approach to explore the advanced SACs for high-value-added chemicals.

Cover Feature: Influence of Charge Delocalization on Manganese Catalyzed Transfer Hydrogenation (ChemCatChem 7/2024)

Cover Feature: Influence of Charge Delocalization on Manganese Catalyzed Transfer Hydrogenation (ChemCatChem 7/2024)

Efficient synthesis of γ-valerolactone from ethyl levulinate via catalytic transfer hydrogenation in supercritical isopropanol over nickel aluminum oxide nanosheets

This study reports a novel method for γ-valerolactone (GVL) production from ethyl levulinate (EL) utilizing non-noble metal catalysts within a supercritical isopropanol (IPA) system. Nickel-loaded nickel–aluminum oxide nanosheets (NiXAl-R) were fabricated via hydrothermal treatment of Ni–Al layered double hydroxide precursors, followed by hydrogen reduction at 550 °C for 1.5 h. Using NiXAl-R as the catalyst and IPA as the hydrogen donor, we achieved notable results: 82.7% EL conversion, 73.6% GVL yield, and 1.178 molGVL g−1 h−1 reaction efficiency after 1.5 h in supercritical IPA. The catalytic activity of NiXAl-R remained stable over five catalytic cycles. The surface of NiXAl-R exhibits abundant oxygen vacancies and unsaturated Al species (Alx+), which promote the initial transfer hydrogenation of EL to form the ethyl 4-hydroxypentanoate (4-HPE) intermediate. Simultaneously, the supercritical IPA environment overcomes mass transfer limitations at the solid–liquid interface between 4-HPE and the catalyst, thereby facilitating the Alx+-catalyzed intramolecular esterification of 4-HPE into GVL.

A Fluorogenic Substrate for Quinoline Reduction: Pnictogen‐Bonding Catalysis in Aqueous Systems

AbstractIt is often said that pnictogen‐bonding catalysis, and σ‐hole catalysis in general, would not work in aqueous systems because the solvent would interfere as an overcompetitive pnictogen‐bond acceptor. In this study, we show that the transfer of pnictogen‐bonding catalysis from hydrophobic solvents to aqueous systems is possible by replacing only hydrophobic with hydrophilic substrates, without changing catalyst or reaction. This differs from conventional covalent Lewis acid catalysts, which are instantaneously destroyed by ligand exchange. With their water‐proof substituents in place of exchangeable ligands, pnictogen‐bonding catalysts, the supramolecular counterpart of Lewis acid catalysts, are evinced to catalyze transfer hydrogenation of quinolines in neutral aqueous systems. To secure these results, we introduce a water‐soluble fluorogenic substrate that releases a coumarin upon the reduction of quinolines instead of activated quinolidiniums, and stiborane catalysts with deepened σ holes. They demonstrate that pnictogen‐bonding catalysts can operate in higher‐order architectures for supramolecular systems catalysis under biologically relevant conditions, and provide an operational assay for high‐throughput catalyst screening by fluorescence imaging, in situ under relevant aqueous conditions.

Organometallic Mn(I) Complexes in Asymmetric Catalytic (Transfer) Hydrogenation and Related Transformations

AbstractDirect asymmetric hydrogenation (AH) and asymmetric transfer hydrogenation (ATH) are among the most efficient approaches to produce chiral building blocks. Recently, these types of transformations have witnessed a shift towards the use of molecular catalysts based on earth‐abundant transition metals due to their ready availability, economic advantage, and novel properties. With particular regard to manganese, catalyst development has seen both the efficiency and substrate scope in AH and ATH greatly improved, with the emergence of a large number of well‐defined Mn‐complexes employed in this field. The reaction scope includes the AH and ATH of C=O bonds, asymmetric reduction of C=N bonds and the asymmetric reductive transformations of C=C bonds. Herein, our survey of the area focuses on the catalytic activity of such complexes, their versatility towards asymmetric transformations and the routes employed to convert substrates to their target molecules. We consider the collected findings of this article will be helpful to the reader by providing an insight into ligand design, thereby aiding future catalyst development. Moreover, this review is aimed at highlighting the remarkable progress made in the last seven years in the development of manganese complexes for enantioselective reduction.

Synthesis of the Pentasaccharide of the K14 Capsular Polysaccharide of Antibiotic Resistant ST25 Acinetobacter baumannii isolate, D46 and O‐Polysaccharide of Acinetobacter baumannii O11

AbstractSynthesis of the pentasaccharide corresponding to the K14 capsular polysaccharide from ST25 Acinetobacter baumannii isolate, D46 and O‐polysaccharide of Acinetobacter baumannii O11 has been achieved in very good yield using a convergent stereoselective [3+2] block glycosylation strategy. The synthetic scheme includes several regio‐ and stereose lective glycosylations as well as orthogonal glycosylation with high yield. Thioglycosides have been used as glycosyl donors using a combination of copper(II) bromide and tetra‐n‐butylammonium bromide (TBAB) as thiophilic activator for 1,2‐cis glycosylation and a combination of N‐iodosuccinimide (NIS) and trimethylsilyl trifluoromethanesulfonate (TMSOTf) as thiophilic activator for 1,2‐trans glycosylation. Glycosyl trichloroacetimidate derivative was used as glycosyl donor using perchloric acid supported on silica (HClO4–SiO2) as activator. A catalytic transfer hydrogenation reaction has been carried out for the removal of benzyloxy and benzylidene functional groups using triethylsilane as hydrogen source.

Poly(divinylbenzene-maleic acid) Hollow Nanospheres Coordinated with Zirconium: An Effective Catalyst for the Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol

Poly(divinylbenzene-maleic acid) Hollow Nanospheres Coordinated with Zirconium: An Effective Catalyst for the Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol

Stabilization of unique Zr>4+ species in NiFe2O4 nanocrystals for unprecedented catalytic transfer hydrogenation reaction

Stabilization of transition metal species (like Zr>4+) with increasingly positive charge density at oxide surfaces is highly important for intrinsically improving catalytic performance for many uses like catalytic transfer hydrogenation (CTH) reaction, which however remains inaccessible. Here, we showcase a water-quenching strategy that stably achieves Zr>4+ species at surfaces of prototype spinel oxide NiFe2O4. Systematic investigation unveils that these Zr>4+species were precisely incorporated into surface octahedral Ni sites of NiFe2O4. The local electronic structure was thus regulated. As a consequence, there simultaneously appear electron depletion (Zr>4+) and accumulation (O2-) at the resulted sites, which play the distinct roles as Lewis acid-base sites in (i) facilitating O-H bond dissociation and CO bond activation, (ii) enhancing the interaction and bonding with substrate molecules, and (iii) reducing the energy barrier for hydrogen transfer process. The resulting catalysts exhibit superior catalytic performance and stability in the CTH reaction of biomass-derived carbonyls and representative aldehydes/ketones, especially the reduction of furfural to furfuryl alcohol with a yield of 90.7% under 120 ℃ for 3 h. This work provides new insights into optimizing catalytic activity in metal oxides by stabilizing transition metal species with unexpectedly positive charge density.

Synthesis, Characterization, and Catalytic Application of Colloidal and Supported Manganese Nanoparticles.

Colloidal and supported manganese nanoparticles were synthesized following an organometallic approach and applied in the catalytic transfer hydrogenation (CTH) of aldehydes and ketones. Reaction parameters for the preparation of colloidal nanoparticles (NPs) were optimized to yield small (2-2.5 nm) and well-dispersed NPs. Manganese NPs were further immobilized on an imidazolium-based supported ionic phase (SILP) and characterized to evaluate NP size, metal loading, and oxidation states. Oxidation of the Mn NPs by the support was observed resulting in an average formal oxidation state of +2.5. The MnOx@SILP material showed promising performance in the CTH of aldehydes and ketones using 2-propanol as a hydrogen donor, outperforming previously reported Mn NPs-based CTH catalysts in terms of metal loading-normalized turnover numbers. Interestingly, MnOx@SILP were found to lose activity upon air exposure, which correlates with an additional increase in the average oxidation state of Mn as revealed by X-ray absorption spectroscopic studies.

Nitrogen-doped ordered mesoporous carbon supported ruthenium metallic nanoparticles: Opportunity for efficient hydrogenolysis of biomass-derived 5-hydroxymethylfurfural to 2,5-dimethylfuran by catalytic transfer hydrogenation

One of the most promising solutions to the current energy crisis is an efficient catalytic transformation of abundant low-cost renewable raw biomass into high-quality biofuel. Herein, a highly effective catalyst was constructed systematically for the selective synthesis of 2,5-dimethylfuran (DMF) biofuel from biomass-derived 5-hydroxymethylfurfural (HMF) via green catalytic transfer hydrogenolysis (CTH) using a nitrogen-doped ordered mesoporous carbon (N-CMK-1) decorated ruthenium (Ru)-based catalyst in i-propanol as hydrogen source. The structures and properties of different catalysts were characterized by different characterization techniques such as FTIR, XRD, N2-sorption, CO2-sorption, TGA, TEM, ICP-AES, CHNO analysis, and acid-base back titration. A complete HMF conversion with a high DMF yield of 88% was achieved under optimized reaction conditions. Regarding substrate conversion and product yield, the influence of reaction temperature, time, and hydrogen donors was thoroughly investigated. The nitrogen-promoted carbon support enhanced the dispersion of Ru due to the formation of appropriate basic site density which could efficiently promote the activation of alcohol hydroxyl in i-propanol and subsequent release of active hydrogen species. In the meantime, highly dispersed surface Ru nanoparticles (NPs) were beneficial for hydrogen transfer and activation of both carbonyl and hydroxyl groups in HMF. Moreover, Arrhenius kinetic analysis was studied by identifying 5-methyl furfural (5-MF) and 2,5-bishydroxymethylfuran (BHMF) as two key intermediates that dominate a distinct reaction pathway during hydrogenolysis of HMF to DMF via CTH. Furthermore, high stability without obvious loss of activity after three consecutive cycles was observed in a fabricated N-CMK-1 decorated Ru-based catalyst as a result of superior metal-support interaction and the mesoporous framework nature of the catalyst. These findings would not only offer a robust catalyst synthetic approach but also open a new avenue for the exploitation of biomass to specialty chemicals and advanced biofuels.

Reversible Dihydrogen Activation and Catalytic Transfer Hydrogenation with Iminophosphinoyl‐Tethered Ruthenium Carbene Complexes

AbstractIn the last decades, metal ligand cooperativity has intensively been used as tool in homogeneous catalysis for the development of potent catalysts for a variety of applications, above all hydrogenation and transfer hydrogenation reactions. Herein, we report on the synthesis of iminophosphinoyl‐tethered ruthenium carbene complexes and their use in the activation of dihydrogen and the catalytic transfer hydrogenation of p‐fluoroacetophenone. Variation of the N‐substituent to an electron‐withdrawing p‐nitrophenyl group enabled the reversible activation of elemental hydrogen via a 1,2‐addition across the metal carbon double bond both in solution and in solid state. In comparison to the thiophosphinoyl‐tethered carbene complex the presented iminophosphinoyl systems showed a considerably increased catalytic activity in transfer hydrogenation reactions, thus highlighting the tunability of the cooperative behavior of nucleophilic carbene complexes.