Highly stable and selective Ru/NiFe2O4 catalysts for transfer hydrogenation of biomass-derived furfural to 2-methylfuran

Spinel ferrites NiFeOsupported Ru catalysts have been prepared via a simple sol–gel route and applied for converting biomass-derived furfural to 2-methylfuran. The as-prepared catalysts were characterized by thermogravimetric analysis（TG）, Nadsorption–desorption, X-ray diffraction（XRD）, scanning electronic microscopy（SEM）, and X-ray photoelectron spectroscopy（XPS）. Results showed that the catalysts had well-dispersed Ru active sites and large surface area for calcination temperature ranging from 300 to 500 ℃. The conversion of biomass-derived furfural into 2-methylfuran was conducted over Ru/NiFeOthrough catalytic transfer hydrogenation in liquid-phase with 2-propanol as the hydrogen source. A significantly enhanced activity and increased 2-methylfuran yield have been achieved in this study. Under mild conditions（180 ℃ and 2.1 MPa N）, the conversion of furfural exceeds 97% and 2-methylfuran yield was up to 83% over the catalyst containing 8 wt% Ru. After five repeated uses, the catalytic activity and the corresponding product yield remained almost unchanged. The excellent catalytic activity and recycling performance provide a broad prospects for various practical applications.

Novel Chiral PNNP-Ru Complexes:Synthesis and Application in Asymmetric Transfer Hydrogenation of Ketones

The efficient catalytic systems generated in situ from RuCl2（PPh3）3 and chiral ligands N,N-bis[2-（di-o-tolylphosphino）-benzyl]cyclohexane-1,2-diamine（2） were employed for asymmetric transfer hydrogenation of aromatic ketones, giving the corresponding optically active alcohols with high activities（up to 99% conversion） and excellent enantioselectivities（up to 96% e.e.） under mild conditions. The chiral ruthenium（Ⅱ） complex （R,R）-3 has been prepared and characterized by NMR and X-ray crystallography.

Magnetic graphene oxide-anchored Ni/Cu nanoparticles with a Cu-rich surface for transfer hydrogenation of nitroaromatics

The bimetallic nanoparticles compositing of Ni-rich core and Cu-rich shell(Ni/Cu NPs)were successfully synthesized by a liquid-phase thermal decomposition method.The content of copper and nickel in Ni/Cu NPs was controllable by adjusting the ratio of two metal precursors,copper formate(Cuf)and nickel acetate tetrahydrate(Ni(OAc)_(2)·4H_(2)O).Ni/Cu NPs were further anchored on graphene oxide(GO)to prepare a magnetic composite catalyst,called Ni/Cu-GO.The dispersibility of Ni/Cu NPs in solution was enhanced by GO anchoring to prevent the sintering and aggregation during the reaction process,thereby ensuring the catalytic and cycling performance of the catalyst.The catalytic transfer hydrogenation(CTH)reaction of nitroaromatics was investigated when ammonia borane was used as the hydrogen source.Cu dominated the main catalytic role in the reaction,while Ni played a synergistic role of catalysis and providing magnetic properties for separation.The Ni_(7)/Cu_(3)-GO catalyst exhibited the best catalytic performance with the conversion and yield of 99%and 96%,respectively,when 2-methyl-5-nitrophenol was used as the substrate.The Ni_(7)/Cu_(3)-GO catalyst also exhibited excellent cyclic catalytic performance with the 5-amino-2-methylphenol yield of above 90%after six cycles.In addition,the Ni_(7)/Cu_(3)-GO catalyst could be quickly recycled by magnetic separation.Moreover,the Ni_(7)/Cu_(3)-GO catalyst showed good catalytic performance for halogen-containing nitroaromatics without dehalogenation.

Water promoted photocatalytic transfer hydrogenation of furfural to furfural alcohol over ultralow loading metal supported on TiO_(2)

Photocatalytic hydrogenation of furfural offers an ideal method for selective biomass upgrading into value-added chemicals or fuel additives under mild conditions. However, it is still challenging to control the product selectivity due to side reactions of functional groups and reactive radical intermediates.Herein, photocatalytic transfer hydrogenation of furfural was studied using the TiO_(2)-based photocatalysts with alcohols as both the solvent and hydrogen donor. Ultralow loading metal supported on TiO_(2),together with adding a small amount of water in the system, were demonstrated to greatly increase the selectivity of furfuryl alcohol product. Electron paramagnetic resonance(EPR), ultraviolet-visible spectroscopy(UV-Vis) and photoluminescence(PL) measurements gave evidence that ultralow loading Pt or Pd on TiO_(2)increase the oxygen vacancy concentration and the photogenerated charge separation efficiency, which accelerates the photocatalytic reduction of furfural. In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS) and mechanistic studies confirmed that photogenerated holes and electrons are active species, with dissociatively adsorbed methanol being directly oxidized by holes,furfural hydrogenated by protons and electrons and H_(2)O modifying the intermediate diffusion which contributes to high selectivity of furfuryl alcohol. This work demonstrates a simple approach to design photocatalysts and tune product selectivity in biomass valorization.

A New Catalyst for Hydrogen Transfer Hydrogenation of Acetophenone

A new C-2-symmetric diamine/diphosphine Ruthenium (II) complex, RuCl2P2N2H4, was used as an excellent catalyst to carry out the catalytic hydrogen transfer reduction of acetophenone. The conversion of acetophenone to 2-phenylethanol was up to 99% under the following reaction conditions: substrate:Ru:(CH3)(2)CHOK = 200:1:12; reaction temperature of 65 degrees C; reaction time of 2 h; normal pressure. A hydride transfer mechanism was also discussed.

Enantioselective Transfer Hydrogenation of Aromatic Ketones Catalyzed by New Diaminodiphosphine Ru(Ⅱ) Complexes

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Asymmetric Transfer Hydrogenation of Ketone Catalyzed by Novel Ru(Ⅱ)-Chiral Sulfonamide Complex

Two new chiral Ru(Ⅱ)-sulfonamide complex have been used to catalyze the enantioselective transfer hydrogenation of prochiral ketones and the secondary alcohols are obtained with good to excellent optical yields.

Rhodium-Catalyzed Asymmetric Transfer Hydrogenation of Heterocyclic Diaryl Ketones:Facile Access to Key Intermediate of Baloxavir

Transition metal-catalyzed asymmetric transfer hydrogenation has been proven to be a powerful approach for the synthesis of chiral alcohols.Herein,a highly efficient and enantioselective transfer hydrogenation of dibenzoheptaheterocyclic ketones catalyzed by an arene-tethered TsDPEN-based Rh(ll)catalyst has been successfully developed,and a variety of dibenzoheptaheterocyclic ketones were reduced by a 1/1 mixture of formic acid and DBU(1,8-diazabicyclo[5.4.0]undec-7-ene)with high yields and enantioselectivities.With this method,the asymmetric reduction of 7,8-difluorodibenzo[b,e]thiepin-11(6H)-one has been realized,providing the key intermediate of baloxavir marboxil with>99% yield and>99% ee at a substrate/catalyst molar ratio of 1000.

Carbon coated LaFe_(0.92)Pd_(0.08)O_(3) composites for catalytic transfer hydrogenation:Balance in the ability of substrates adsorption and conversion

Catalytic transfer hydrogenation(CTH)is a green and efficient pathway for selective hydrogenation of unsaturated aldehydes and ketones.However,managing the abilities of solid catalysts to adsorb substrates and to convert them into desired products is a challenging task.Herein,we report the synthesis of carbon coated LaFe_(0.92)Pd_(0.08)O_(3) composites(LFPO-8@C)for CTH of benzaldehyde(BzH)into benzyl alcohol(BzOH),using isopropanol(IPA)as hydrogen source.The coating with carbon improves the ability to adsorb/transfer reactants from solution to active sites,and the doping of Pd2+at Fe3+site strengthens the ability of LaFeO_(3) to convert BzH into BzOH.A balanced point between them(i.e.,abilities to adsorb BzH and to convert BzH into BzOH)is obtained at LFPO-8@C,which exhibits a BzOH formation rate of 3.88 mmol·gcat^(-1)·h^(-1) at 180℃ for 3 h,which is 1.50 and 2.72 times faster than those of LFPO-8 and LaFeO_(3)@C.A reaction mechanism is proposed,in which the acidic sites(e.g.,Fe^(4+),oxygen vacancy)are used for the activation of C=O bond of BzH and O-H bond of IPA,and the basic sites(e.g.,lattice oxygen)for the activation ofα-H(O-H)bond of IPA.

Boehmite-supported CuO as a catalyst for catalytic transfer hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan

2,5-bis(hydroxymethyl)furan(BHMF)is an important monomer of polyester.Its oxygen-containing rigid ring structure and symmetrical diol functional group establish it as an alternative to petroleum-based monomer with unique advantages for the prodution of the degradable bio-based polyester materials.Herein,we prepared a boehmite-supported copper-oxide catalyst for the selective hydrogenation of 5-hydroxymethylfurfural into BHMF via catalytic transfer hydrogenation(CTH).Further,ethanol successfully replaced conventional high-pressure hydrogen as the hydrogen donor,with up to 96.9% BHMF selectivity achieved under suitable conditions.Through characterization and factor investigations,it was noted that CuO is crucial for high BHMF selectivity.Furthermore,kinetic studies revealed a higher by-product activation energy compared to that of BHMF,which explained the influence of reaction temperature on product distribution.To establish the catalyst structure-activity correlation,a possible mechanism was proposed.The copper-oxide catalyst deactivated following CTH because ethanol reduced the CuO,which consequently decreased the active sites.Finally,calcination of the catalyst in air recovered its activity.These results will have a positive impact on hydrogenation processes in the biomass industry.

Triazole backbone ligand in an unprecedented efficient manganese catalyst for use in transfer hydrogenation

Noble metal catalysts are generally expensive,and thus,abundant 3d metals recently received significant attention as catalysts in catalytic hydrogenation.Mn catalysts are widely applied in transfer hydrogenations,but the reported catalyst loadings remain up to three orders of magnitude higher than noble metals.Thus,catalyst consumption should be overcome before 3d metal catalytic systems may be utilized practically in industry.Here,a catalytic system based on novel,scalable triazole N5-ligands coordinated to Mn is presented for use in transfer hydrogenations.Based on pre-activation via dehydrohalogenation,an unprecedented,efficient catalytic system operating via synergistic H-bond auxiliary activation was established.The Mn catalysts are practical at metal concentrations 0.0001 mol%,generating alcohol with turnover number(TON)up to 857,200,thus approaching loadings more conventionally observed in precious-metal-based systems.Notably,using this protocol,several pharmaceuticals may be easily synthesized in one pot.

Pincer Ru with a single stereogenic identity for highly efficient asymmetric transfer hydrogenation of ketones

The asymmetric reduction of carbonyl compounds by means of the Ru-chiral diphosphine-chiral diamine catalysts is widely useful in organic synthesis where high levels of enantioselectivities have been attributed to multiple ligand chiral elements as well as essential stereochemical matching synergies within them.Described here is the design and discovery of new pincer-type Ru-catalysts that feature only single stereogenic element within ligands,yet the such significantly simplified structure is demonstrated to be well competent for effecting asymmetric reductions as well as kinetic resolutions over a broad range of highly functionalized ketones/alcohols,including heteroaryl substituted substrates that were challenging by known catalyst systems.Alcohols were furnished not only in excellent enantioselectivities,but with turnover numbers(up to 100,000 TONs)that reach the highest levels known to date in asymmetric transfer hydrogenation of ketones.This work should help shed light on the intricate origin of enantioselection in these important processes,and further stimulate rational understanding as well as optimization of chiral catalysts towards efficiency and simplicity.

Determining the contribution of Mo single atoms components in MoO_(2)nanocatalyst in transfer hydrogenation

Nanocatalysts are likely to contain undetected single-atom components,which may have been ignored but have significant effect in catalytic reactions.Herein,we report a catalyst composed of Mo single atoms(SAs)and MoO_(2)nanoparticles(NPs)(MoSAs-MoO_(2)@NC),which is an exact model to understand how the SAs contribute to the nanocatalyst.Both experimental results and the density functional theory calculations reveal that Mo SAs on nitrogen-doped carbon provides the reaction zone for nitro reduction,while MoO_(2)is the active site for decomposing hydrazine hydrate to produce H*.Thanks to the synergy between Mo SAs and MoO_(2)NPs,this catalyst exhibits noble metal-like catalytic activity(100%conversion at 4 min)for the dechlorination-proof transfer hydrogenation.Additionally,the hydrogen migration on the catalyst is verified by the electrochemical tests in the absence of a hydrogen source.This work provides a model for further study on the coexistence of single atoms in nanoparticle catalysts.

Cobalt single atoms supported on monolithic carbon with a hollow-on-hollow architecture for efficient transfer hydrogenations

Single-atom catalysts(SACs)have received considerable attention in hydrogenation of nitroaromatic compounds to aromatic amines.In order to enhance the exposure of single atoms and overcome the mass transfer limitation,construction of hierarchical porous supports for single atoms is highly desirable.Herein,we report a straightforward method to synthesize Co single-atoms supported on a hollow-on-hollow structured carbon monolith(Co_(1)/HOHC-M)by pyrolysis ofα-cellulose monolith loaded with PS-core@ZnCo-zeolite imidazolate frameworks-shell nanospheres(PS@Zn-ZIFs/α-cellulose).The hollow-on-hollow structure consists of a large hollow void with a diameter of~290 nm(derived from the decomposition of polystyrene(PS)nanospheres)and a thin shell with hollow spherical pores with a diameter of~10 nm(derived from the evaporation of ZnO nanoparticles that are in-situ formed during pyrolysis in the presence of CO_(2)fromα-cellulose decomposition).Benefitting from the hierarchically porous architecture,the Co_(1)/HOHC-M exhibits excellent catalytic performance(reaction rate of 421.6 mmol·gCo^(-1)·h^(−1))in the transfer hydrogenation of nitrobenzene to aniline,outperforming the powdered sample of Co_(1)/HCS without the hollow spherical mesopores(reaction rate of 353.8 mmol·gCo^(-1)·h^(−1)).It is expected that this strategy could be well extended in heterogeneous catalysis,given the wide applications of porous carbon-supported single-atom catalysts.

Controlling N-doping type in carbon to boost single-atom site Cu catalyzed transfer hydrogenation of quinoline

Single-atom site(SA)catalysts on N-doped carbon(CN)materials exhibit prominent performance for their active sites being M-Nx.Due to the commonly random doping behaviors of N species in these CN,it is a tough issue to finely regulate their doping types and clarify their effect on the catalytic property of such catalysts.Herein,we report that the N-doping type in CN can be dominated as pyrrolic-N and pyridinic-N respectively through compounding with different metal oxides.It is found that the proportion of distinct doped N species in CN depends on the acidity and basicity of compounded metal oxide host.Owing to the coordination by pyrrolic-N,the SA Cu catalyst displays an enhanced activity(two-fold)for transfer hydrogenation of quinoline to access the valuable molecule tetrahydroquinoline with a good selectivity(99%)under mild conditions.The higher electron density of SA Cu species induced by the predominate pyrrolic-N coordination benefits the hydrogen transfer process and reduces the energy barrier of the hydrogenation pathway,which accounts for the improved catalytic effeciency.

Synthesis of novel chiral N,P-containing multidentate ligands and their applications in asymmetric transfer hydrogenation

Novel chiral PN_4-type multidentate aminophosphine ligands have been successfully synthesized by Schiff-base condensation of bis（o-formylphenyl）phenylphosphane and various chiral amino-sulfonamides.Their structures were fully characterized by IR,EI-MS and NMR.The catalytic systems,prepared in situ from the multidentate ligands and iridium（I） complexes,showed high activity in asymmetric transfer hydrogenation of propiophenone in 2-propanol solution,leading to corresponding optical alcohol with up to 75%ee.

Quasi-continuous synthesis of cobalt single atom catalysts for transfer hydrogenation of quinoline

Improving the transfer hydrogenation of N-heteroarenes is of key importance for various industrial pro-cesses and remains a challenge so far.We reported here a microcapsule-pyrolysis strategy to quasi-continuous synthesis S,N co-doped carbon supported Co single atom catalysts(Co/SNC),which was used for transfer hydrogenation of quinoline with formic acid as the hydrogen donor.Given the unique ge-ometric and electronic properties of the Co single atoms,the excellent catalytic activity,selectivity and stability were observed.Benefiting from the quasi-continuous synthesis method,the as-obtained cata-lysts provide a reference for the large-scale preparation of single atom catalysts without amplification ef-fect.Highly catalytic performances and quasi-continuous preparation process,demonstrating a new and promising approach to rational design of atomically dispersed catalysts with maximum atomic efficiency in industrial.

Transfer Hydrogenation of Ethyl Levulinate toγ-Valerolactone Catalyzed by Iron Complexes

Conversion of biomass-derived ethyl levulinate toγ-valerolactone is realized by using homogeneous iron-catalyzed transfer hydrogenation(CTH).By utilizing Casey's catalyst and cheap isopropanol as hydrogen source,γ-valerolactone can be generated in 95%yield.Addition of catalytic amount of base is important to achieve good yield.

Catalytic transfer hydrogenation of biomass-derived furfural to furfuryl alcohol with formic acid as hydrogen donor over CuCs-MCM catalyst

Catalytic transfer hydroge nation(CTH)of furfural(FF)to furfu ryl alcohol(FFA)has received great intere st in recent years.He rein,Cu-Cs bimetallic supported catalyst,CuCs(2)-MCM,was developed for the CTH of FF to FFA using formic as hydrogen donor.CuCs(2)-MCM achieved a 99.6%FFA yield at an optimized reaction conditions of 170℃,1 h.Cu species in CuCs(2)-MCM had dual functions in catalytically decomposing formic acid to generate hydrogen and hydrogenating FF to FFA.The doping of Cs made the size of Cu particles smaller and improved the dispersion of the Cu active sites.Impo rtantly,the Cs species played a favorable role in enhancing the hydrogenation activity as a promoter by adjusting the surface acidity of Cu species to an appropriate level.Correlation analysis showed that surface acidity is the primary factor to affect the catalytic activity of CuCs(2)-MCM.

Sulfur Vacancy-Promoted Highly Selective Electrosynthesis of Functionalized Aminoarenes via Transfer Hydrogenation of Nitroarenes with H_(2)O over a Co_(3)S_(4−x) Nanosheet Cathode

Developing a selective hydrogenation strategy over a low-cost electrocatalyst,especially with an inexpensive and safe hydrogen source for efficient synthesis of aminoareneswith fragile functional groups,is extremely desirable.Herein,using H_(2)O as the hydrogen source,Ti mesh-supported Co_(3)S_(4)ultrathin nanosheets with sulfur vacancies(denoted as Co_(3)S_(4−x)NS)have been demonstrated to be a highly efficient cathode for selective transfer hydrogenation of nitroarenes to corresponding aminoarenes at low potential.D_(2)O-labeling experiments confirmed the hydrogen origin.Without sulfur vacancies,the products were a mixture of aminoarenes and azoxyareneswith lowselectivity.This method can deliver a variety of aminoarenes with outstanding selectivity and excellent functional group compatibility with highly reducible groups(e.g.,C–I,C–Br,C=O,C=C,C=N,C≡N,and C≡C).The experimental and theoretical results have revealed that sulfur vacancies can enhance the selective specific adsorption of the nitro group and promote intrinsic activity to form active hydrogen from water electrolysis,thus resulting in high selectivity and outstanding fragile functional groups tolerance.