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In this work, Ru nanoparticles doped with Mo on reduced graphene oxide (RuMo/rGO) are prepared through synchronous reduction of RuCl3, MoCl5, and graphene oxide. The compositions, morphologies, and structures of the as-prepared RuMo/rGO composites are fully characterized. Their catalytic properties in oxidative cleavage of β-O-4 linkages in lignin model compounds and lignin are explored. It is illustrated that with O2 as the oxidant RuMo/rGO shows overall better catalytic performance in the oxidative cleavage of β-O-4 linkages than the catalysts, such as Ru/rGO and RuCo/rGO, reported in our previous work. The catalytic mechanism is elaborated through experiments and density functional theory (DFT) calculation. Pronouncedly, we show that the as-doped Mo can effectively boost the molecular oxygen activation process and the adsorption of β-O-4 model compounds on the Ru nanoparticle surface on rGO, and thus enhance the catalytic activity. It is demonstrated meanwhile that RuMo/rGO can catalyze the depolymerization of organosolv birch lignin yielding 17.1% aromatic compounds under relatively mild conditions (100 °C, 0.3 MPa O2, 12 h, pH = 12). [ABSTRACT FROM AUTHOR]

Upcycling biodegradable polyester waste into value-added chemicals can not only avoid CO2 emissions but also achieve sustainable carbon recycling. Herein, we report a one-pot catalytic process to deconstruct polycaprolactone into 6-aminocaproic acid (EACA) and caprolactam (CPL), two monomers of nylon-6, using aqueous ammonia and Ru catalysts. No additional hydrogen is required, and the total yield of EACA and CPL could reach 90.2% using a ternary catalyst, Ru/CeO2/RGO, at 140 °C. It is verified that 6-hydroxyhexanoic acid and 6-hydroxyhexanoamide are the initial intermediates resulting from polycaprolactone decomposition, which undergo dehydrogenation, amination and re-hydrogenation to transform into EACA and 6-aminohexanoamide over the Ru catalyst. The hydrolysis of 6-aminohexanoamide produces EACA, and the reverse reaction between dehydration of EACA and hydrolysis of CPL results in their coexistence. The protocol demonstrated here provides a novel route to recycle polycaprolactone to valuable chemicals. [ABSTRACT FROM AUTHOR]

The first ever homobimetallic catalyst which efficiently catalyzes the reductive amination (RA) reaction of carbonyl compounds in water is described herein. Two new Ru(II) compounds, homobimetallic [(p-cymene)2(RuCl)2L1] (Ru1) and monometallic [(p-cymene)(RuCl)L2] (Ru2) (where L1 = 2,2′-((1E,1′E)-((3,3′,5,5′-tetraisopropyl-[1,1′-biphenyl]-4,4′diyl)bis-(azaneylylidene))bis(methaneylylidene))diphenoxide) and L2 = (2,6-(((diisopropylphenyl)-imino)methyl)phenoxide) incorporating Schiff-base ligands have been synthesized and characterized by various spectroscopic and analytical techniques. Their molecular structures have been deduced by X-ray diffraction measurements. Both complexes, which are water/air stable at room temperature as well as at high temperature, were employed as catalysts for RA in aqueous media using formate buffer as the hydrogen source. Complex Ru1, in the presence of formic acid/formate buffer as the hydrogen source, catalyzes one-pot RA production of secondary amines in ∼99% yield with just 0.05 mol% of the catalyst exhibiting a turnover number (TON) of 1920 and a turnover frequency (TOF) of 480 h−1. When the catalyst loading was further reduced to 0.0001 mol%, the highest reported TON and TOF for any RA reactions were observed (4.3 × 104 and 107 × 103 h−1, respectively), albeit with reduced selectivity. A comparative study between Ru1 and Ru2 reveals that complex Ru1 is more chemo-selective for the formation of a secondary amine, attributable to a cooperative effect. This cooperative effect is further substantiated through extensive computational methodologies involving Density Functional Theory (DFT) calculations on both bimetallic and monometallic Ru(II) complexes along a hybrid-model complex. [ABSTRACT FROM AUTHOR]

To resolve white plastic pollution and the human carbon footprint, we report an efficient green approach to quantitatively convert polyethylene terephthalate (PET) to high-density C6–C8 cyclic hydrocarbons via single-step water-assisted hydrodeoxygenation (HDO) over a Ru/TiO2 catalyst in a biphasic system. To understand the structure–activity relationships of supported metal catalysts in PET HDO, acidic and neutral support-loaded Ru catalysts were prepared, characterized, and evaluated in mono- and biphasic systems. An experimental study revealed that Ru/TiO2 effectively catalyzed the production of C6–C8 cyclic hydrocarbons from PET. Under mild conditions (220 °C, 50 bar H2, 12 h), the catalyst completely converted PET into fuel-range C6–C8 cyclic hydrocarbons at a remarkably high selectivity of 96.8–99.2%. The catalyst successfully cleaved all C–O bonds in the aromatic plastic in a water–dodecane (O/W) biphasic system via the favorable effects of the metal-acid bifunction, hydrophilicity, and high dispersion of small Ru particles on the support. Due to its hydrophilic behavior, the nanosized catalyst formed stable Pickering emulsion droplets in the biphasic system. The presence of these droplets increased the selectivity towards C6–C8 hydrocarbons by forming a reaction interface with a large area between the oil and water layers. This improves accessibility to the active sites of the catalyst, stabilizes the intermediates, and enhances mass transfer and the separation of the target products. Furthermore, using a model compound study, we identified the pathway involved in the HDO reaction. Moreover, the addition of water to the biphasic system significantly increased the rate of proton transfer on the catalyst support. This study presents an excellent single-step catalytic pathway for application in synthesizing C6–C8 cyclic hydrocarbons using PET waste in a water-assisted biphasic system, providing a viable solution for plastic recycling. [ABSTRACT FROM AUTHOR]

Well-crafted semiconductors exhibiting favorable band structures and strong electron-donating properties can provide a viable pathway for solar-driven nitrogen activation under ambient conditions. In this study, we demonstrate that the nitrogen photo-fixation process can be enhanced by introducing oxygen vacancies and a Ru co-catalyst. The Ru-loaded ZrO2−x photocatalyst achieved an impressive NH3 production rate of 3256 μg g−1 h−1 under visible light irradiation (at 400 nm). Defective ZrO2−x with its enhanced reducing ability and narrow band gap possesses a low work function and excellent electron-donating capability, resulting in remarkable photocatalytic performance for ammonia synthesis under visible light. The supported Ru co-catalyst induces upward band bending in defective ZrO2−x, forming an interfacial Schottky barrier that facilitates the separation of photogenerated charge carriers and provides energetic electrons for nitrogen activation. Mott–Schottky photocatalysts with enhanced back donation ability establish a one-way channel for the transmission of photoexcited electrons, thereby further improving the photocatalytic performance of ammonia synthesis at room temperature. [ABSTRACT FROM AUTHOR]

For effective overall water splitting (OWS) in alkaline media, a novel Ru-doped bimetal oxide (Ru-NiCo2O4) catalyst deposited onto a conductive nickel foam (NF) is fabricated by a multi-step hydrothermal reaction, ion exchange, and subsequent annealing process. The distinctive 3D nanoneedle-like arrays not only provide an even distribution of Ru decorated NiCo2O4, but also expose additional active sites, facilitating electron transport and improving reaction kinetics. Besides, density functional theory (DFT) studies elucidate the electronic structure regulation in Ru-NiCo2O4 and the modification of the d-band center optimizes H* adsorption energy, which considerably increased the hydrogen production efficiency. Considering the aforementioned advantages, the as-prepared Ru-NiCo2O4 electrocatalyst exhibits greatly improved catalytic activity, requiring only 25 mV and 249 mV at 10 mA cm−2 for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, as well as robust stability. Amazingly, the Ru-NiCo2O4 electrode in a two-electrode alkaline electrolyzer only needs 1.55 V to produce 10 mA cm−2, making it more efficient than the commercial RuO2‖‖Pt/C electrode (1.62 V). More importantly, 0.33 M urea only needs a low voltage of 1.427 V to drive the urine-mediated electrolysis, which is about 123 mV less than the urea-free electrolysis cell. This work presents an effective electronic structure engineering approach based on heteroatom doping that may be extended to design and fabricate novel high-performance OWS catalysts. [ABSTRACT FROM AUTHOR]

One of the key steps in producing value-added chemicals from biomass-derived compounds is the conversion of levulinic acid (LA) into useful products. In the present work, a novel catalyst was prepared by immobilizing ruthenium nanoparticles on bimodal N,S-doped ordered mesoporous carbon (IBOMC). Various analytical methods, including TEM, XRD, XPS and N2 adsorption-desorption, were used to characterize both IBOMC and the synthesized catalyst (Ru@IBOMC). Ru@IBOMC was then successfully utilized in the continuous flow catalytic hydrogenation of LA to γ-valerolactone and N-containing heterocycles at room temperature. The effects of different reaction variables (such as temperature, H2 gas pressure, solvent, LA concentration, and flow rate) were examined. This catalytic protocol exclusively affords quantitative yields of γ-valerolactone at room temperature under continuous flow conditions under 30 bar H2 pressure. The catalyst also exhibits excellent activity for producing N-containing heterocycles at room temperature by using either aniline or acetonitrile as the amine source. The catalyst shows consistent performance for at least 72 hours without significant loss of activity and selectivity in a wide range of solvents, giving an excellent weight hourly space velocity (WHSV) of 48 h-1. These results confirmed that nitrogen and sulfur active centres in IBOMC can effectively stabilize ruthenium nanoparticles and synergistically enhance the performance of Ru active centers in the hydrogenation of LA. [ABSTRACT FROM AUTHOR]

The utilization of stimuli-responsive hydrogels as bifunctional catalysts for an aqueous sequential organic transformation to prepare chiral organic molecules is not only environmentally friendly, but also complements the synthetic limitations of mutually contradictory multistep reactions. However, finding a solution to the incompatible issue arising from complicated multicomponent cross-interactions in sequential transformations is a significant challenge. To address this issue, we have developed a core–shell-structured hydrogel as a site-isolated bifunctional catalyst. This catalyst features thermoresponsive poly(N-isopropylmethacrylamide) with a switching function via a reversible transition between its hydrogel and solution phases that perfectly matches a temperature-tuned base-catalyzed aldol condensation/oxa-Michael addition at 70 °C and the ruthenium-catalyzed dynamic kinetic resolution asymmetric transfer hydrogenation (DKR-ATH) process at 40 °C. As we envisioned, through the harmonization of the conflicting sequential reactions, this aldol condensation/oxa-Michael addition/DKR-ATH cascade process can be achieved by transitioning from being incompatible to compatible, enabling direct access to chiral chromanols with 1,3-positioned dual stereocenters from commercially available ortho-hydroxyl arylketones and aldehydes. Mechanistic investigations, which involve monitoring the cascade reaction and analyzing the deuterium-labeling experiments, reveal a domino-like aldol condensation/oxa-Michael addition/DKR-ATH sequential route comprising an initial aldol condensation/oxa-Michael addition followed by the subsequent DKR-ATH process. [ABSTRACT FROM AUTHOR]

Herein, a novel class of room temperature chiral phosphine-functionalized polyether imidazolium ionic liquids (RTCP-PolyIMILs) was synthesized for the first time by an ion exchange reaction between the 5,5′-disulfonato-(S)-BINAP ligand and polyether imidazolium ILs. The interactions with the polyether imidazolium transformed the solid sulfonated BINAP with a high melting point into a room temperature IL, which can act as a phosphine ligand and a carrier. Using the attractive dual functionality of RTCP-PolyIMILs, an efficient and sustainable homogeneous catalysis and biphasic separation system (HCBS) was constructed for Ru(II)-catalyzed enantioselective hydrogenation of β-keto esters to optically active β-hydroxy esters. Only a catalytic amount of RTCP-PolyIMIL was needed in the absence of any external carrier ILs, allowing the easy recovery and recycling of the chiral Ru catalyst. The Ru(II)-RTCP-PolyIMIL catalyst showed higher activity and better adaptability to a wide range of solvents than the traditional Ru(II)-BINAP catalyst. Specifically, a TOF value of up to 3900 h−1, an enantioselectivity of up to 99%, long-term stability up to a total TON value of nearly 17 000, an extremely low Ru loss rate of only 0.08–0.09%, and good universality for structurally diverse β-keto esters with different electronic and steric properties were demonstrated. These dramatic enhancing effects can be attributed to the structure of RTCP-PolyIMILs integrated with a phosphine ligand and polyether ILs, where polyether-induced clustering blocking-up and polarity enhancement effects played critical roles. [ABSTRACT FROM AUTHOR]

Direct C–H functionalisation methodologies represent an opportunity to improve the overall 'green' credentials of organic coupling reactions, improving atom economy and reducing overall step count. Despite this, these reactions frequently run under reaction conditions that leave room for improved sustainability. Herein, we describe a recent advance in our ruthenium-catalysed C–H arylation methodology that aims to address some of the environmental impacts associated with this procedure, including solvent choice, reaction temperature, reaction time, and loading of the ruthenium catalyst. We believe that our findings demonstrate a reaction with improved environmental credentials and showcase it on a multi-gram scale within an industrial setting. [ABSTRACT FROM AUTHOR]

A set of macrocyclic unsaturated musk compounds was obtained from unbiased dienes via ring-closing metathesis at 20–40 times higher concentration than recommended in state-of-the-art, proceeding via formation of oligomers and then by a backbiting metathesis reaction. As the commercial Schrock catalyst Mo1 does not lead to the parasitic C–C double bond migration process, the above reactive distillation proceeded with very high chemical selectivity, leading to pure macrocyclic musk products in 24–92% yield and selectivity around 90% or higher. It was also shown that this process can be performed under user-friendly conditions, using Schrock catalyst Mo1 suspended in paraffin tablet, cheap PAO-6 engine oil as a diluent, on air, in simple distillation glassware, and with a standard laboratory vacuum pump. In addition, most of the substrates were obtained from bio-sourced oleic acid, making the high-concentration RCM (HC-RCM) process even more environmentally friendly. [ABSTRACT FROM AUTHOR]

Selective hydrodeoxygenation of lignin-derived phenolics to value-added aromatic products such as phenol with high efficiency and low energy consumption remains an important challenge in the field of biomass conversion. Herein, we fabricated a series of Ti-modified SiO2 supported catalysts (Ru/Ti–SiO2) with rich Ti3+ defects and size-controllable Ru particles via a facile wet impregnation method for the conversion of guaiacol in an aqueous phase. Under relatively mild conditions (240 °C and 0.4 MPa H2), Ru/Ti–SiO2 exhibited higher activity for C–O bond cleavage compared with both Ru/SiO2 and Ru/TiO2 catalysts, and achieved high guaiacol conversion (83.6%) and phenol selectivity (70.4%). The catalytic activity was increased with the introduction of the Ti modifier, and the deoxygenation ability of the Ru/Ti–SiO2 catalyst gradually increased with the Ti content. The presence of Ti–O–Si linkages in the Ti-modified SiO2 support promoted the formation of defect-rich TiOx species, which further inhibited the aggregation of Ru particles and increased their dispersion, regardless of the high reduction temperature and high Ru loading. Besides, those small-sized TiOx interacted with Ru electronically and promoted the formation of Ru0 species. The interface between Ru and TiOx species (Ru0–Ti3+) of the Ru/Ti–SiO2 catalyst was confirmed as the main active sites for the deoxygenation of guaiacol, benefiting the activation of the C–O bond. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) have been used for the first time as a sustainable medium in a ruthenium-catalyzed C–H activation reaction. This study describes an efficient, simple and straightfoward protocol for the direct C–H activation of a broad range of aromatic substrates and reaction with several olefins and alkynes, affording interesting heterocyclic systems as products. A simple, robust and commercially available ruthenium catalyst was used along with different DESs under different reaction conditions. This methodology was compatible with the use of either internal or external oxidant (oxygen from air) using a catalytical amount of copper salts for the last case. Different functional directing groups were well tolerated obtaining promising results, that were comparable and even better that those reported in the literature. Also, the reaction medium could be recycled up to 3 consecutive times and this transformation could be carried out on a gram scale with excellent yield. Several green chemistry mass metrics, such as reaction mass efficiency, process mass intensity and optimum efficiency, as well as qualitative parameters were calculated and compared with those of the classical protocols, showing the advantages of using DESs for C–H activation processes. [ABSTRACT FROM AUTHOR]

The direct construction of a C(sp)–S–P(O) moiety from unactivated terminal alkynes remains highly challenging. Alkynyl phosphorothioates are obtained by coupling terminal alkynes and P(O)SH. Using commercially available and inexpensive Ru(bpy)3Cl2 and copper as a catalyst, this cross dehydrogenative coupling reaction is first performed under photoirradiation. Direct use of stable P(O)SH and terminal alkynes without the need to prepare unstable S–X and P–X derivatives represents a prominent advantage of this method. More attractively, this operationally simple reaction avoids the use of odorous thiols and poisonous alkynyl bromides. [ABSTRACT FROM AUTHOR]

Herein, we present a novel protocol for the catalytic depolymerisation of bio-based polyhydroxybutyrate and polylactic acid over Ru/CeO2. The corresponding monomers of 3-hydroxybutyric acid and lactic acid were afforded with yields of 79 and 94%, respectively. Moreover, the transformation of a mixture of both biopolyesters was possible with a comparable outcome. [ABSTRACT FROM AUTHOR]

The magnetically heated hydrotreatment of levulinic acid, furfural and hydroxymethylfurfural over a composite Ru-based nanocatalyst in a batch reactor was investigated. The nanocatalyst's dual role as a heating agent and catalytically active material was demonstrated. The in-depth analysis and modelling of the hydrogenation and deoxygenation processes showed that the surface of the nanocatalyst reaches a higher temperature (137 °C) than the bulk of the medium (85 °C), resulting in an increased rate of conversion for isopropyl levulinate (formed in a competing reaction) to γ-valerolactone and thus increasing the yield under mild conditions. The nanocatalyst remained stable and active (100% yield of GVL), even when recycled four times. [ABSTRACT FROM AUTHOR]

A versatile synthetic pathway for the production of valuable alkyl phenols and anilines has been developed based on the selective hydrodeoxygenation of a wide range of hydroxy-, amino-, and nitro-acetophenone derivatives as readily available substrates. Bimetallic iron ruthenium nanoparticles immobilized on an imidazolium-based supported ionic liquid phase (Fe25Ru75@SILP) act as highly active and selective catalysts for the deoxygenation of the side-chain without hydrogenation of the aromatic ring. The catalytic system allows operation under continuous flow conditions with high robustness and flexibility as demonstrated for the alternating conversion of 3′,5′-dimethoxy-4′-hydroxyacetophenone and 4′-hydroxynonanophenone as model substrates. [ABSTRACT FROM AUTHOR]

We studied the hydrogenation at temperatures from 313–393 K of a biomass-derived platform molecule, 5-hydroxymethyl furfural (HMF)-acetone-HMF (HAH) over Pd, Ru, and Cu based catalysts. HAH was selectively hydrogenated to produce partially-hydrogenated monomers (PHAH) over Cu and Ru catalysts and to fully-hydrogenated HAH monomers (FHAH) over the Ru catalyst. Pd based catalysts yielded a mixture of partially and fully hydrogenated monomers. Lumped reaction kinetics models were employed to quantify the kinetic behavior for hydrogenation over Ru, Cu, and Pd catalysts. The 5-step pathway exhibited over Pd and Ru catalysts consists of both series and parallel reaction steps, where HAH is both converted to fully hydrogenated products sequentially via series reactions of partially hydrogenated intermediates, as well as converted directly in parallel reactions to form the fully hydrogenated products. In contrast, the 3-step pathway over the Cu catalyst consists only of the consecutive reaction steps, where the final product was formed via series reactions of intermediate products. Additionally, reaction over the Cu catalyst did not hydrogenate the furan rings of the HAH molecule and yielded a different final product than those hydrogenation over Pd and Ru catalysts. Batch conditions are determined for each hydrogenated product that give the highest yields in both batch and plug flow reactors. [ABSTRACT FROM AUTHOR]

Esters are an important class of chemicals in industry. Traditionally, ester production is a multi-step process involving the use of corrosive acids or acid derivatives (e.g. acid chloride, anhydride, etc.). Therefore, the development of a green synthetic protocol is highly desirable. This work reports the development of a metal–organic framework (MOF) supported tandem catalyst that can achieve direct alcohol to ester conversion (DAEC) using oxygen as the sole oxidizing agent under strictly solvent-free conditions. By incorporating Ru nanoparticles (NPs) along with a homogeneous Lewis acid catalyst, scandium triflate, into the nanocavities of a Zr MOF, MOF-808, the compound catalyst, Sc–Ru⊂MOF-808, can achieve aliphatic alcohol conversion up to 92% with ester selectivity up to 91%. A mechanistic study reveals a unique "via acetal" pathway in which the alcohol is first oxidized on Ru NPs and rapidly converted to an acetal on Sc(III) sites. Then, the acetal slowly decomposes to release an aldehyde in a controlled manner for subsequent oxidation and esterification to the ester product. To the best of our knowledge, this is the first example of DAEC of aliphatic alcohols under solvent-free conditions with high conversion and ester selectivity. [ABSTRACT FROM AUTHOR]

In this paper, 2-methylquinoline compounds were synthesized continuously from nitroarenes and the ethanol/water system by a simple hydrogen transfer reaction in the presence of the Ru–Fe/γ-Al2O3 catalyst. This new simple synthesis reaction was heterogeneous and continuous. At the same time, green solvents were used, and strong acids, oxidants, and other environmentally harmful substances were not added, which conformed to the principles of green chemistry. Through the impregnation method, the nanocatalysts with a smaller particle size and uniform dispersion were obtained on the γ-Al2O3 particles (1–2 mm) and had good activity. The effects of the alcohol water volume ratio, pressure, flow rate and Ru–Fe mass ratios on the yields of 2-methylquinoline compounds in the reaction were investigated. The reaction can proceed smoothly for nitroarenes with different substituents, and a moderate to good yield (46%–88%) was obtained. [ABSTRACT FROM AUTHOR]

Cyclohexanol is an essential intermediate in the chemical industry for the synthesis of nylon and other materials, but the direct hydrogenation of phenol to produce cyclohexanol is problematic owing to excessive energy consumption associated with the harsh reaction conditions. In this regard, novel composite catalysts (Ru/Nb2O5-nC18PA) coated with octadecylphosphonic acid (C18PA) were prepared via an impregnation method to be applied for the efficient hydrogenation of phenol to produce cyclohexanol in a biphasic system consisting of water and decalin solvent. Under a hydrogen pressure of 12 bar and 80 °C, nearly 100% conversion of phenol and 93% yield of cyclohexanol were achieved within 4 hours. With the introduction of more Lewis acid sites the aromatic ring is activated, which promotes the HYD (hydrogenation) path of phenol, thereby giving improved selectivity to cyclohexanol. A mechanism-exploration experiment was carried out and showed that the strong binding effect between the surface of the Ru/Nb2O5-nC18PA catalysts and the benzene ring allows the aromatic ring in phenol to be hydrogenated, increasing the selectivity to cyclohexanol. This biphasic catalytic system enhances the potential value of lignin via the catalytic hydrogenation of lignin-derived phenols. [ABSTRACT FROM AUTHOR]

A Ru single-atom (Ru SA) catalyst supported on activated carbon was adopted to synthesize 3-pentanone with 83.3% selectivity via heterogeneous ethylene hydroformylation, while 52.1% ethane selectivity was obtained for Ru nanoparticles (Ru NPs). The atomically dispersed Ru species with oxidation state (Ruδ+) and Ru-C4O coordination structure were identified as the active sites for efficient C–C coupling to generate 3-pentanone, while metallic Ru nanoparticles exhibited high activity for ethylene hydrogenation to ethane. Density functional theory (DFT) calculation revealed that the energy barrier of the direct coupling of C2H5CO* with C2H5* to form 3-pentanone on Ru SA was much lower than that on Ru NPs. As a result, the formation of 3-pentanone over Ru SA was more favourable than propanal, which was admittedly generated via coupling of C2H5CO* and H*. This strategy may provide a potential green route for the one-pot synthesis of 3-pentanone with high atomic economy. [ABSTRACT FROM AUTHOR]

N-Methylation of amines with CO2/H2 to N-methylamines over non-noble metal catalysts is very interesting but remains challenging. Herein, we present an alcohol (e.g., ethanol) promoted strategy for the N-methylation of anilines with CO2/H2 with high efficiency under mild conditions (e.g., 125 °C), which is achieved over a cobalt catalytic system composed of Co(OAc)2·4H2O, triphos and Sn(OTf)2. This catalytic system has a broad substrate scope and is tolerant toward a wide range of anilines and N-methyl anilines, and a series of N,N-dimethyl anilines were obtained in high yields. Mechanism investigation indicates that the alcohol solvent shifts the equilibrium of CO2 hydrogenation by forming an alkyl formate, which further reacts with the amine to produce N-formamide, and Sn(OTf)2 promotes the deoxygenative hydrogenation of N-formamides to afford N-methylamines. This is the first example of the N-methylation of amines with CO2/H2 over a cobalt catalytic system, which shows comparable performance to the reported Ru catalysts and may have promising applications. [ABSTRACT FROM AUTHOR]

RuNi nanoparticles (NP) were prepared by decomposition of [Ru(η4-C8H12)(η6-C8H10)] and [Ni(η4-C8H12)2] by H2 in the presence of polyvinylpyrrolidone (PVP) at 85 °C using several Ru/Ni ratios. The nanoparticles display a segregated structure in which Ni is on the surface, as ascertained by wide angle X-ray scattering (WAXS). The catalytic activity in the selective hydrogenation of furfural of these RuNi NP was correlated with the Ru content. High selectivity towards the partially hydrogenated product 2-(hydroxymethyl)furan (HF) was found when carrying out the reaction in tetrahydrofuran (THF). A different scenario was found when using a protic polar solvent, 1-propanol. Catalysts displaying Ru on the surface were able to hydrogenate the heteroaromatic ring, while those with Ni on the surface were highly selective towards the partially hydrogenated product. In addition, Ru surfaces were prone to catalyse the acetalization reaction in the presence of the alcoholic solvent, while the addition of Ni supressed this reactivity. Density functional theory (DFT) calculations performed on hydrogenated Ru nanoparticles (Ru55H70) show differences in the adsorption energies of several reagents, products, reaction intermediates, and solvents onto the Ru NP surface, which are in line with the experimental catalytic results. [ABSTRACT FROM AUTHOR]

A novel and green route for the synthesis of cyclopentane-1,3-diamine (CPDA) from hemicellulosic feedstock is established in this work. Through many explorations and optimizations, the single successful multi-step synthesis was found to comprise: (1) the Piancatelli rearrangement of furfuryl alcohol to 4-hydroxycyclopent-2-enone (4-HCP), (2) a highly improved isomerization of 4-HCP into cyclopentane-1,3-dione (CPDO) using the Ru Shvo catalyst, (3) conversion of CPDO into cyclopentane-1,3-dioxime (CPDX), and (4) a mild oxime hydrogenation of CPDX over Rh/C to afford the desired CPDA. In addition, diastereomerically pure cis- and trans-isomers of CPDA were reacted with (A) bio-based lactones, and (B) 5-(hydroxymethyl)furfural (HMF) to synthesize novel bifunctional diol monomers with internal amide and imine groups, respectively. Monomer 5, derived using γ-valerolactone (GVL), was successfully applied in the synthesis of polyurethanes. [ABSTRACT FROM AUTHOR]

Most current processes for the general synthesis of primary amines by reductive amination are performed with enormously excessive amounts of hazardous ammonia. It remains unclear how catalysts should be designed to regulate amination reaction dynamics at a low ammonia-to-substrate ratio for the quantitative synthesis of primary amines from the corresponding carbonyl compounds. Herein we show a facile control of the reaction selectivity in the layered boron nitride supported ruthenium catalyzed reductive amination reaction. Specifically, locating ruthenium to the edge surface of layered boron nitride leads to an increased hydrogenation activity owing to the enhanced interfacial electronic effects between ruthenium and the edge surface of boron nitride. This enables self-accelerated reductive amination reactions which quantitatively synthesize structurally diverse primary amines by reductive amination of carbonyl compounds with twofold ammonia. [ABSTRACT FROM AUTHOR]

Selectivity control of nitrobenzene hydrogenation remains a great challenge, and it is desirable to develop a green and highly efficient catalytic route toward value-added metastable intermediate products. Herein, we reported that isolated Ru single atoms coordinated with oxygen atoms in CeO2 (Ru-SAs/CeO2) can achieve chemoselective hydrogenation of nitrobenzene to azoxybenzene with a selectivity of 88.2% in a continuous flow reactor using H2 without using any bases or expensive organic reducing agents, while 82.7% aniline selectivity was obtained by Ru nanoparticles. We demonstrated that the unique coordinated structure between Ru single atoms and O atoms preferentially controls the reaction route toward the coupling of nitrosobenzene and phenylhydroxylamine intermediates to form azoxybenzene while greatly suppressing over-hydrogenation. The present work provides an efficient strategy to regulate the reaction pathway of nitrobenzene hydrogenation with a green and industry-friendly process by designing highly dispersed Ru single atoms. [ABSTRACT FROM AUTHOR]

Functional polyurethanes and polyesters with tunable properties were synthesized from biomass-derived 5-hydroxymethyl furfural (HMF)–acetone–HMF (HAH) monomers. HAH can be selectively hydrogenated over Cu and Ru catalysts to produce partially-hydrogenated (PHAH) and fully-hydrogenated (FHAH). The HAH units in these polymers improve the thermal stability and stiffness of the polymers compared to polyurethanes produced with ethylene glycol. Polyurethanes produced from PHAH provide diene binding sites for electron deficient C＝C double bonds, such as in maleimide compounds, that can participate in Diels–Alder reactions. Such sites can function to create crosslinking by Diels–Alder coupling with bismaleimides and can be used to impart functionality to PHAH (giving rise to anti-microbial activity or controlled drug delivery). The symmetric triol structure of FHAH leads to energy-dissipating rubbers with branched structures. Accordingly, the properties of these biomass-derived polymers can be tuned by controlling the blending ratio of HAH-derived monomers or the degree of Diels–Alder reaction. The polyester produced from HAH can be used in packaging applications. [ABSTRACT FROM AUTHOR]

In this study, the heterogeneously catalyzed alkoxycarbonylation of olefins with CO2 based on a supported ionic-liquid-phase (SILP) strategy is reported for the first time. An [Ru]@SILP catalyst was accessed by immobilization of ruthenium complex on a SILP, wherein imidazolium chloride was chemically integrated at the surface or in the channels of the silica gel support. An active Ru site was generated through reacting Ru3(CO)12 with the decorated imidazolium chloride in a proper microenvironment. Different IL films, by varying the functionality of the side chain at the imidazolium cation, were found to strongly affect the porosity, active Ru sites, and CO2 adsorption capacity of [Ru]@SILP, thereby considerably influencing its catalytic performance. The optimized [Ru]@SILP-A-2 displayed enhanced catalytic performance and prominent substrate selectivity compared to an independent homogeneous system under identical conditions. These findings provide the basis for a novel design concept for achieving both efficient and stable catalysts in the coupling of CO2 with olefins. [ABSTRACT FROM AUTHOR]

In this study, the heterogeneously catalyzed alkoxycarbonylation of olefins with CO2 based on a supported ionic-liquid-phase (SILP) strategy is reported for the first time. An [Ru]@SILP catalyst was accessed by immobilization of ruthenium complex on a SILP, wherein imidazolium chloride was chemically integrated at the surface or in the channels of the silica gel support. An active Ru site was generated through reacting Ru3(CO)12 with the decorated imidazolium chloride in a proper microenvironment. Different IL films, by varying the functionality of the side chain at the imidazolium cation, were found to strongly affect the porosity, active Ru sites, and CO2 adsorption capacity of [Ru]@SILP, thereby considerably influencing its catalytic performance. The optimized [Ru]@SILP-A-2 displayed enhanced catalytic performance and prominent substrate selectivity compared to an independent homogeneous system under identical conditions. These findings provide the basis for a novel design concept for achieving both efficient and stable catalysts in the coupling of CO2 with olefins. [ABSTRACT FROM AUTHOR]

It is highly attractive to produce γ-valerolactone (GVL), an all-purpose biomass-derived platform molecule, by the solvent-free hydrogenation of levulinic acid (LA), but the intense adsorption of the carboxylic group over the catalyst will block the active sites of the catalyst. In this study, the established hydrogen bond between LA and choline chloride (ChCl) suppressed the adsorption of the carboxylic group but enhanced the adsorption of the acyl group of LA over Ru/C, which greatly improved the hydrogenation of the acyl group in LA to afford quantitative GVL yield under solvent-free conditions. [ABSTRACT FROM AUTHOR]

An exclusive asymmetric reduction of C＝O bonds of 2-arylidene four-, five-, six-, and seven-membered cycloalkanones has been studied systematically. The asymmetric transfer hydrogenation was performed using a robust and commercially available chiral diamine-derived ruthenium complex as a catalyst and HCOOH/Et3N as a hydrogen source under mild conditions, giving 51 examples of chiral exocyclic allylic alcohols in up to 96% yield and 99% ee. This method was also applicable to the gram-scale synthesis of the active intermediates of the anti-inflammatory loxoprofen and natural product (−)-goniomitine. [ABSTRACT FROM AUTHOR]

The transformation of levulinic acid (LA) into γ-valerolactone (GVL) in water at room temperature is very interesting. In this work, we designed and prepared single Ru atoms on a TiO2@nitrogen doped porous carbon support catalyst (Ru/TiO2@CN). It was demonstrated that the catalyst had very high activity, selectivity and stability for the conversion of LA into GVL at room temperature in water. The turnover frequency (TOF) could reach 278 molGVL molRu−1 h−1 at complete conversion, which was about 35 times higher than that of commercial Ru/C. In addition, only GVL was generated in the reaction over the catalyst of this work. [ABSTRACT FROM AUTHOR]

The Aldehyde-Water Shift (AWS) reaction uses H2O as a benign oxidant to convert aldehydes to carboxylic acids, producing H2, a valuable reagent and fuel, as its sole byproduct. (Hexamethylbenzene)RuII complexes are demonstrated to have higher activity and selectivity (up to 95%) for AWS over disproportionation than previously reported catalysts. [ABSTRACT FROM AUTHOR]

Levetiracetam is an active pharmaceutical ingredient widely used to treat epilepsy. We describe a new synthesis of levetiracetam by a dynamic kinetic resolution and a ruthenium-catalysed ex-cell anodic oxidation. For the enzymatic resolution, we tailored a high throughput screening method to identify Comamonas testosteroni nitrile hydratase variants with high (S)-selectivity and activity. Racemic nitrile was applied in a fed-batch reaction and was hydrated to (S)-(pyrrolidine-1-yl)butaneamide. For the subsequent oxidation to levetiracetam, we developed a ligand-free ruthenium-catalysed method at a low catalyst loading. The oxidant was electrochemically generated in 86% yield. This route provides a significantly more sustainable access to levetiracetam than existing routes. [ABSTRACT FROM AUTHOR]

We report the homogeneous catalytic hydrogenation of biomass derived furanic aldehydes to furfuryl alcohols using low loadings of PNP metal complexes under mild conditions. Our strategy represents an efficient and selective approach to the direct hydrogenation of furan derivatives to promising platform chemicals. [ABSTRACT FROM AUTHOR]

Although CaCO3 is a naturally available, inexpensive, abundant and extensively used chemical in various industries, to date, most of its conversions liberate CO2 into the atmosphere, which accounts for about 5–6% of global anthropogenic CO2 emission. Herein, the first synthesis of calcium formate (CF) by hydrogenation of an aqueous mixture of CaCO3 and CO2 using a heterogeneous catalyst in an unconventional CO2 reducing manner is reported. The phosphine-based heterogenized Ru catalyst efficiently converts CaCO3 into CF with good selectivity (>99%) and is readily separated from the reaction product, resulting in promising recycling ability. Thus, this work provides a promising strategy for the design of green and sustainable conversion of carbonate minerals in industry. [ABSTRACT FROM AUTHOR]

Along with the mitigation of CO2 emission, recently, the CO2-derived formic acid process has drawn attention as a promising platform for the renewable-energy-derived hydrogen storage cycle by using formic acid as a liquid organic hydrogen carrier (LOHC). Here, a heterogenized Ru molecular catalyst on a bpyTN-30-CTF support is prepared and successfully implemented in an integrated trickle-bed reactor system for continuous CO2 hydrogenation to produce formic acid. The bpyTN-30-CTF support with an alternative structure of the bpy and TN motif increases the porosity and metal anchoring sites. The Ru/bpyTN-30-CTF catalyst prepared using the bpyTN-30-CTF support displays sufficient catalytic activity for commercialization. Under the continuous process, the catalyst exhibits substantial catalytic performance with the highest productivity of 669.0 gform. gcat−1 d−1 with CO2 conversion of 44.8% for a superficial gas velocity of 72 cm s−1. Furthermore, the catalyst shows excellent stability in the continuous hydrogenation process with a trickle-bed reactor over 30 days of operation, reaching a total turnover number of 524 000 without any significant deactivation. Based on kinetic data, a new process to produce formic acid by CO2 hydrogenation has thus been proposed here. [ABSTRACT FROM AUTHOR]

Visible-light-driven continuous-flow decarboxylative annulation was achieved and used along with a microreactor containing immobilized ruthenium catalyst to construct valuable fused imidazole derivatives with high yields under an open atmosphere. Notably, this chemistry included the use of L -proline and α-azidochalcone as precursors of an α-amino radical and 2H-azirine via photo-induced decarboxylation and denitrogenation, respectively, to give the annulated imidazole derivatives as a result of the formation of two new C–N bonds. Moreover the novel, environmentally benign and efficient continuous-flow protocol was further improved by carrying out the reaction in a polydimethylsiloxane (PDMS) microreactor with immobilized Ru3+ under fluorescent or white LED light, enabling excellent yields (70–94%) at a reaction time (2 min) significantly shorter than that (16 h) of the batch protocol. [ABSTRACT FROM AUTHOR]

Only few dynamic kinetic resolution (DKR) systems are known for chiral aliphatic amines due to the difficult racemization of these amines. In this work, each aspect of the DKR of aliphatic amines is investigated. Various ruthenium catalysts were evaluated to increase their applicability in racemization as an alternative to established heterogeneous palladium catalysts. A heterogeneous Ru(III) on zeolite catalyst showed good activity for racemization in aprotic polar media. Next, kinetic resolution was evaluated; excellent yields (50%) and selectivities (>99%) were obtained in apolar solvents when employing isopentyl propionate as resolving agent. After evaluation of both components, the complete dynamic kinetic resolution of an aliphatic amine was established with good selectivity (97%), enantiomeric excess (96%) and a yield exceeding the kinetic resolution limit of 50%. [ABSTRACT FROM AUTHOR]

The sustainable production of polymers from biogenic platform chemicals shows great promise to reduce the chemical industry's dependence on fossil resources. In this context, we propose a new two-step process leading from dicarboxylic acids, such as succinic and itaconic acid, to N-vinyl-2-pyrrolidone monomers. Firstly, the biogenic acid is reacted with ethanolamine and hydrogen using small amounts of water as solvent together with solid catalysts. For effective conversion, the optimal catalyst (carbon supported ruthenium) has to hold the ability of activating H2 as well as (imide) C＝O bonds. The obtained products, N-(2-hydroxyethyl)-2-pyrrolidones, are subsequently converted in a continuous gas phase dehydration over simple sodium-doped silica, with excellent selectivity of above 96 mol% and water as the sole by-product. With a final product yield of ≥72 mol% over two process steps and very little waste due to the use of heterogeneous catalysis, the proposed route appears promising – commercially as well as in terms of Green Chemistry. [ABSTRACT FROM AUTHOR]

The hydrogenation of amides is a straightforward method to produce (possibly bio-based) amines. However current amide hydrogenation catalysts have only been validated in a rather limited range of toxic solvents and the hydrogenation of aliphatic (acyclic) primary amides has rarely been investigated. Here, we report the use of a new and relatively cheap ruthenium–tungsten bimetallic catalyst in the green and benign solvent cyclopentyl methyl ether (CPME). Besides the effect of the Lewis acid promotor, NH3 partial pressure is identified as the key parameter leading to high primary amine yields. In our model reaction with hexanamide, yields of up to 83% hexylamine could be achieved. Beside the NH3 partial pressure, we investigated the effect of the catalyst support, PGM-Lewis acid ratio, H2 pressure, temperature, solvent tolerance and product stability. Finally, the catalyst was characterized and proven to be very stable and highly suitable for the hydrogenation of a broad range of amides. [ABSTRACT FROM AUTHOR]

The selective, efficient and sustainable continuous flow hydrogenation of a α,β-unsaturated aldehyde, i.e. cinnamaldehyde, to the corresponding unsaturated alcohol, i.e. cinnamyl alcohol, using a novel catalyst based on Ru-containing scrap waste automotive converters is reported. The catalyst was prepared by recycling and upgrading waste ceramic-cores of scrap automotive catalytic converters as supporting materials. Ruthenium was incorporated into the ceramic structures using a simple, fast and solventless mechanochemically assisted procedure followed by a chemical reduction step. Different catalysts were prepared with varying Ru contents. The materials were characterized by XRD, N2 physisorption, XPS, TEM, HRTEM and SEM/mapping analyses. Compared to Ru supported over most studied silica and alumina supports, the new system displayed an outstanding catalytic performance under continuous-flow conditions in terms of conversion and selectivity and a remarkable stability with time-on-stream, demonstrating a synergistic action between Ru and the waste catalytic converter support. A Ru loading of 10 wt% provided the optimum results, including a cinnamaldehyde conversion of up to 95% with a selectivity to cinnamyl alcohol of 80%. [ABSTRACT FROM AUTHOR]

An efficient and halogen-free catalytic methodology for the synthesis of β-amino alcohols from aromatic amines and biomass-derived carbohydrates is demonstrated for the first time. The activation of C5/C6 sugars by a ruthenium catalyst selectively generates the C2 alkylating reagent glycolaldehyde. The transformation involves metal-catalyzed hydrogen borrowing for the reduction of the imine intermediate. A series of arylamines bearing various substituents were successfully transformed into the desired products in good to excellent yields. [ABSTRACT FROM AUTHOR]

The replacement of mercuric chloride with non-mercury catalysts in acetylene hydrochlorination for the production of a vinyl chloride monomer (VCM), the precursor to polyvinyl chloride (PVC), would meet the requirements of green chemistry. The aim of this tutorial review is to discuss the design criteria for non-mercury catalysts, with the focus on the relationship between the catalytic activity/stability and the electronic properties, adsorption, and reducibility of the catalysts. The developments of Au-based catalysts, Ru-based catalysts and other monometallic catalysts are briefly covered in the first part, with emphasis on the active species, reaction mechanism, and alternative preparation methods of Au-based catalysts. An overview of the development of bimetallic/trimetallic catalysts is highlighted in the second part. Then the modification strategies (e.g. heteroatom modification of support, ionic liquid modification) and explorations of the support/preparation method are addressed. Finally, particular attention is paid to the applications of metal-free catalysts and other catalysts (e.g. heteroatom-doped carbon material, nitride and zeolite). [ABSTRACT FROM AUTHOR]

A sustainable protocol of olefin metathesis in non-degassed, undistilled ethyl acetate under air with commercially available self-scavenging ruthenium catalysts is described. Furthermore, a time economical, cost-effective and scalable method of removal of ruthenium residues is presented. Treatment of post-reaction mixtures with an isocyanide scavenger and then with acid followed by a simple filtration is shown to yield OM products with ruthenium contamination below 5 ppm even in highly challenging cases. Finally, a telescope RCM/Suzuki–Miyaura sequence with a rapid and efficient purification protocol for simultaneous removal of Ru and Pd residues from solution is described. [ABSTRACT FROM AUTHOR]

Hydrothermal reduction under aqueous conditions is widely used to convert biomass into more valuable products. However, the harsh conditions inherent in the process can irreversibly alter the intrinsic structure of the support, as well as dissolve the metal ions into the aqueous solution. In this work, for the first time we have synthesized a new highly hydrothermally stable Ru/LaCO3OH catalyst mostly consisting of Ru nanoparticles partially encapsulated by the LaCO3OH support with a strong metal–support interaction (SMSI), which confers high stability and activity to the catalyst under hydrothermal reduction conditions in the hydrogenolysis of the biomass model molecules guaiacol and glycerol. During impregnation, the RuCl3·3H2O precursor initially reacts with LaCO3OH to form a LaRu(CO3)2Cl2 complex and LaOCl. XPS demonstrated that Ru was present in the oxidized state, TEM and XRD showed the absence of Ru0, and the XRD pattern showed the presence of the characteristic lattice fringe of LaOCl. While the LaRu(CO3)2Cl2 complex was resistant to H2 reduction at 350 °C, the complex underwent facile reduction to Ru0 under hydrothermal conditions at 240 °C. In the subsequent process, LaRu(CO3)2Cl2 and LaOCl underwent hydrolysis, forming crystalline LaCO3OH (confirmed by Ag+ titration and XRD patterns), Ru(OH)3, and HCl. The Ru(OH)3 was reduced in situ to Ru0 nanoparticles, as revealed by XPS and TEM analysis. The simultaneous hydrothermal reduction of Run+ species and the formation of crystalline LaCO3OH result in the formation of Ru nanoparticles encapsulated by a protective LaCO3OH layer, as evidenced by HRTEM and DRIFTS CO adsorption measurements. The preparation of catalysts with this unique structure comprising metal nanoparticles protected by the support itself, which confers additional stability, is a novel strategy to prepare hydrothermally stable catalysts. [ABSTRACT FROM AUTHOR]

We developed a conceptually and methodologically novel ruthenium(0) nanoparticle catalyst, sulfur-modified Au-supported ruthenium nanoparticles (SARu). SARu is easily prepared through a three-step procedure involving simultaneous in situ metal nanoparticle and nanospace organization. This unique method does not require any conventional preformed template to immobilize and stabilize metal nanoparticles. SARu is an ideal ruthenium catalyst for liquid-phase combinatorial synthesis because it repeatedly catalyzes ligand-free Suzuki–Miyaura coupling of aryl halides, including aryl chlorides, with arylboronic acids with low Ru leaching. Physical analysis of SARu showed that the active species in these reactions were ruthenium (0) nanoparticles with a size of 1–3 nm. Also, we developed a continuously irradiating microwave methodology, which can first time discriminate the heating effect and the microwave effect in microwave experiments. [ABSTRACT FROM AUTHOR]