Synthesis Of Fine Chemicals Research Articles

Steering single-site metallaphotocatalytic pathway by accumulated electron on carbon nitride support

Organic halide transformation is of high importance for fine chemical synthesis and environmental remediation. Integrated photocatalytic platforms open up distinctive reaction pathway for carbon-halogen bond activation/reconstruction. Herein we reveal carbon nitride (CN)-ligated single atom nickel (Ni1/CN), with accumulated electron on the CN, paves Ni-mediated electron-proton transfer, enabling hydrodehalogenation, along with the catalytic carbon–oxygen (C–O) coupling. The preference for hydrodehalogenation positively correlates with density of electron on CN. EPR measurements suggest photo-generated NiI interacts with aryl halides, followed by electron transfer or reductive elimination to give different products. Further kinetic studies on hydrodehalogenation/C–O coupling show the reaction orders of 0.1/0.5 in aryl halide and 1.5/0.03 in (CN) electron, unveiling rate-determining step as oxidative addition to NiI and (CN) electron transfer for the two conversions. Our work advances in modulating aryl halide conversion by carrier accumulation on the photoactive support and guides metallaphotocatalytic platform design/operation toward target transformations.

Revolutionizing carbon chemistry: Solar-powered C(sp3)-N bond activation and CO2 transformation via newly designed SBE-Y cutting-edge dynamic photocatalyst.

A solvent-free sulfur-bridge-eosin-Y (SBE-Y) polymeric framework photocatalyst was prepared for the first time through an insitu thermal polymerization route using elemental sulfur (S8) as a bridge. The addition of a sulfur bridge to the polymeric framework structure resulted in an allowance of the harvesting range of eosin-Y (E-Y) for solar light. This shows that a wider range of solar light can be used by the bridge material's photocatalytic reactions. In this context, supercharged solar spectrum: enhancing light absorption and hole oxidation with sulfur bridges. This suggests that the excited electrons and holes through solar light can contribute to oxidation-reduction reactions more potently. As a result, the photocatalyst-enzyme attached artificial photosynthesis system developed using SBE-Y as a photocatalyst performs exceptionally well, resulting in high 1,4-NADH regeneration (86.81%), followed by its utilization in the exclusive production of formic acid (210.01 μmol) from CO2 and synthesis of fine chemicals with 99.9% conversion yields. The creation of more effective photocatalytic materials for environmental clean-up and other applications that depend on the solar light-driven absorption spectrum of inorganic and organic molecules could be one of the practical ramifications of this research.

Self-Standing Metal Foam Catalysts for Cathodic Electro-Organic Synthesis.

Although electro-organic synthesis is currently receiving renewed interest because of its potential to enable sustainability in chemical processes to value-added products, challenges in process development persist: For reductive transformations performed in protic media, an inherent issue is the limited choice of metallic cathode materials that can effectively suppress the parasitic hydrogen evolution reaction (HER) while maintaining a high activity toward the targeted electro-organic reaction. Current development trends are aimed at avoiding the previously used HER-suppressing elements (Cd, Hg, and Pb) because of their toxicity. Here, this work reports the rational design of highly porous foam-type binary and ternary electrocatalysts with reduced Pb content. Optimized cathodes are tested in electro-organic reductions using an oxime to nitrile transformation as a model reaction relevant for the synthesis of fine chemicals. Their electrocatalytic performance is compared with that of the model CuSn7Pb15 bronze alloy that has recently been endorsed as the best cathode replacement for bare Pb electrodes. All developed metal foam catalysts outperform both bare Pb and the CuSn7Pb15 benchmark in terms of chemical yield and energetic efficiency. Moreover, post-electrolysis analysis of the crude electrolyte mixture and the cathode's surfaces through inductively coupled plasma mass spectrometry (ICP-MS) and scanning electron microscopy (SEM), respectively, reveal the foam catalysts' elevated resistance to cathodic corrosion.

Surface-Modified Pd/CeO2 Single-Atom Catalyst Shows Increased Activity for Suzuki Cross-Coupling.

Single-atom catalysts (SACs) comprise catalytically active atoms dispersed on supports; they combine the high activity and site uniformity of homogeneous catalysts with the ease of separability of heterogeneous catalysts. However, SACs lack fine control over the active site, provided by ligands in homogeneous catalysts. In this work, we demonstrate that modification of the support with an organic monolayer is a viable approach to improving the catalytic performance. The addition of catechol-type monolayers to a Pd/CeO2 SAC increases its catalytic activity for Suzuki cross-coupling, a central reaction in the synthesis of fine chemicals and pharmaceuticals. Kinetic trials reveal that the coating reduces the activation energy from 49 ± 9 to 22 ± 5 kJ/mol and produces a 4-fold rate enhancement at 25 °C, an effect we attribute to π-π interactions between the reactant and the catechol coating. Further development of this approach could vastly increase the utility of SACs in organic synthesis.

Friedel-Crafts Acylation of Aromatics with Acetic Anhydrideover Nano-Sized Rare Earth Cation Exchanged ZSM-5 Catalysts

Friedel-crafts acylation of aromatic compounds used to synthesize aromatic ketones and significance has commercial importance in diverse areas of fine chemical synthesis and pharmaceutical manufacturing industry. Conventionally, acylation reactions are catalysed by corrosive metal halides or mineral acids. The present work reports on the catalytic activity of nanocrystalline ZSM-5 and rare earth metal cation such as La3+, Ce3+ and Nd3+ exchanged ZSM-5 in the liquid phase acylation of veratrole with acetic anhydride. The catalyst was thoroughly characterized for its structure. The nanocrystalline Ce-ZSM-5 displayed highest activity towards the acylation of veratrole. The catalytic performance of Ce-ZSM-5 was used to compare its activity for the acylation of other aromatics; such as toluene, anisole and veratrole. The nanocrystalline Ce-ZSM-5 shows highest activity over nanocrystalline ZSM-5 in acylation reactions of aromatics. It was established that smaller size crystal of Ce-ZSM-5showed superior activity, which is due to the enhanced density of acidic sites along with increased external surface area of smaller crystal which facilitate the activity of the acylation reaction. The catalysts used in this study are reusable without any loss of activity.

ELECTROCHEMICALLY TREATED LIGNIN IN PHENOLIC RESINS FOR PLYWOOD PANELS

In achieving the European Union's goal of making Europe the first climate-neutral continent by 2050, the scientific community is striving to develop processes and products that are technologically and economically sustainable to replace/substitute fossil-based feedstocks. In this effort, the European project LIBERATE has demonstrated the commercial opportunities of converting low-cost lignin feedstocks into high-value bio sustainable chemicals such as vanillin and mixed phenolic derivatives.Lignin is the largest regenerative source of aromatic organics. In current wood pulping industries, lignin is underutilized and widely considered a side stream primarily exploited for its energy content. A promising approach for the synthesis of biobased fine chemicals is a depolymerisation process for lignin using sodium peroxodicarbonate (PODIC®), an electrochemically produced oxidiser. Within the LIBERATE project, SINTEF has built a pilot scale plant for the electrochemical lignin depolymerisation. The plant provided CHIMAR with the phenol-rich reactor product solution from both kraft and organosolv lignin, which was used as phenol substitutes with up to 50wt% in the formulation of phenol-formaldehyde (PF) resins. These resins have been able to produce successful plywood panels on a laboratory scale. Although their quality is somewhat lower than that of the reference material with traditional PF resin, this work showed that the use of lignin fractions obtained by electrochemical treatment in such an application is possible and promising.

Defect engineering enables synergistic action of hierarchical porosity and multifunctionality for efficient catalysis of diverse reactions

The limitations of embedding suitable functional groups as Brønsted and Lewis pairs in metal–organic materials hinder their application especially to promote catalysis reactions. Due to the generation abundance of unsaturated inorganic nodes upon partial ligand decarboxylation, Quasi-MOFs (Q-MOFs) are considered as a potential candidate for the installation of amino acids. Here for the first time, we demonstrated that Q-HKUST-1 possessing a Lewis acid site could be transformed into an excellent multifunctional chiral MOF (Q-HKUST-Cys), via post-synthetic modification by L-Cysteine. Applying this approach, we can fabricate a pore environment spatially decorated with multiple functional groups. The post-modified MOF has been characterized by a variety of techniques including PXRD, N2 sorption, 1HNMR, FT-IR, CD, and SEM/EDS mapping. Q-HKUST-Cys features unique properties, such as mesoporosity, high Lewis acid sites including Cu2+, Lewis base sites (NH2 group), Bronsted acid sites (COOH group), open channels, and optical activity. So, this chiral MOF exhibits excellent catalytic performance in various asymmetric reactions under mild conditions. The Q-HKUST-Cys is highly enantioselective heterogeneous and recyclable catalyst, in ring-opening of epoxide and nitroaldol reaction with up to 99 % ee, as well as 100 % and 90 % conversion, respectively. Besides, in the cycloaddition of CO2 to styrene-epoxide (STO), and production of the corresponding cyclic carbonate, this catalyst showed high performance (90 % conversion, 89 % ee) under mild conditions, at the atmospheric pressure of CO2 and in the solvent-free situation. The simultaneous presence of these properties makes Q-HKUST-Cys an attractive catalyst for the eco-friendly synthesis of fine chemicals through CC and CO bond formation. As a result, in this study, we showed that anchoring defective MOFs with multifunctional amino acids can be an effective approach for the utilization of synergistic effects in the promotion of many catalysis reactions.

Carbon Monoxide as C1 Building Block in Fine Chemical Synthesis†

Comprehensive SummaryCarbon monoxide (CO) has become one of the most relevant and versatile renewable C1 building blocks for chemical synthesis, especially in the fine chemicals industry, due to the development of efficient and selective catalysts for its activation. In this review, we present a comprehensive critical analysis of the last 10 years literature on the use of CO as a renewable feedstock for fine chemicals production. The review is organized by type of catalytic reaction, namely alkene and alkyne carbonylation, hydroformylation, carbonylation of aryl halides, carbonylative cross‐coupling and C—H carbonylation. Notable examples of the synthesis of relevant building blocks and/or known pharmaceuticals are highlighted. Emphasis is placed on examples of utilizing CO as the C1 building block in one or more catalytic steps. The catalyst used and the reaction conditions are consistently presented throughout all of the examples.

Partially reduced-linked covalent organic frameworks: A new approach for heterogeneous catalysis and naked-eye HCl sensing

Compared to the traditionally made imine-linked covalent organic frameworks (COFs), amine-linked COFs provided by in-situ reduction of the linkages represent significant potential for advanced applications, including catalysis and sensing. The current paper deals with preparing a partially reduced COF with secondary amine groups (IR-COF) via in-situ reduction of imine linkages as a dual-functional material adopted for heterogeneous catalysis and acid-sensing. This COF was synthesized using formic acid as a reductant and catalyst in a solvothermal reaction between 2,4,6-tris-(4-formyl-phenoxy)-1,3,5-triazine and p-phenylenediamine. The IR-COF was used as a basic organocatalyst for the efficient synthesis of tetrahydro-4H-chromenes through the Knoevenagel-Michael cyclocondensation. Excellent yields, short reaction times, easy workup, absence of toxic organic solvents, easy recovery, and reusability of the catalyst are outstanding aspects of this catalytic method, making it convenient and useful for fine chemical synthesis. Moreover, the immediate naked-eye color change of IR-COF upon exposure to the hydrochloric acid by protonating the secondary amine groups was investigated. The (time-dependent) density functional theory (TD)DFT PBE/DNP+ method was used to investigate the mechanism of color change during the sensing. The appearance of a new absorption band at higher wavelengths upon protonation is proved to be due to intermolecular or interlayer electron transitions.

Palladium-catalyzed synthesis of carboxylic acid anhydrides from alkenes

Hydrocarbonylation of alkenes with nucleophiles – water, alcohols and amines, is widely studied and implemented in synthesis of fine chemicals and natural products. Here, an efficient and additive-free palladium-catalyzed hydrocarbonylation reaction of alkenes is described using carboxylic acids as the nucleophile, by which acid anhydrides are obtained in moderate to excellent yields. The relative concentrations of substrate and reagents play an important role in driving the reaction forward, which reaches an equilibrium at equimolar concentrations under a given CO pressure. A ligand-screening study revealed the use of electron-poor phosphine ligands to be crucial for obtaining higher rates of the catalytic reaction. Several substrates including unactivated alkenes were successfully converted to the corresponding symmetric as well as mixed anhydrides. An additional advantage of our synthetic procedure is that the obtained anhydrides can be converted to (primary) amides, thioesters or esters in situ via a simple one-pot derivatization reaction, since acid anhydrides are prone to degradation on isolation.

Biocatalyst Potential Candidate for Human Welfare

Biocatalysis is known since man knew about brewing which was known since 6000 years. Enzymes from microbial sources were then employed in industries such as production of beer, wine, cheese etc. Nearly 100 years down the lane biocatalysts have been used for chemical transformations. In order to access the repertoire of pharmacological and agrochemicals with high chemoselectivity, regioselectivity, and enantioselectivity, biocatalysis integrates microbiologists, enzymologists, and organic chemists. The usual chemical approach is challenged by the saturation of carbon-carbon double bonds by biocatalysts, as they avoid the usage of organocatalysts or precious metals (in combination with chiral ligands and molecular hydrogen). Since past 30 years they have been used for the synthesis of valuable fine chemicals especially pharmaceuticals. This review gives a brief about microbial biocatalyst including the photosynthetic blue-green algae.

Encapsulation of Palladium Carbide Subnanometric Species in Zeolite Boosts Highly Selective Semihydrogenation of Alkynes.

The selective hydrogenation of alkynes to alkenes is a crucial step in the synthesis of fine chemicals. However, the widely utilized palladium (Pd)-based catalysts often suffer from poor selectivity. In this work, we demonstrate a carbonization-reduction method to create palladium carbide subnanometric species within pure silicate MFI zeolite. The carbon species can modify the electronic and steric characteristics of Pd species by forming the predominant Pd-C4 structure and, meanwhile, facilitate the desorption of alkenes by forming the Si-O-C structure with zeolite framework, as validated by the state-of-the-art characterizations and theoretical calculations. The developed catalyst shows superior performance in the selective hydrogenation of alkynes over mild conditions (298 K, 2 bar H2 ), with 99 % selectivity to styrene at a complete conversion of phenylacetylene. In contrast, the zeolite-encapsulated carbon-free Pd catalyst and the commercial Lindlar catalyst show only 15 % and 14 % selectivity to styrene, respectively, under identical reaction conditions. The zeolite-confined Pd-carbide subnanoclusters promise their superior properties in semihydrogenation of alkynes.

Encapsulation of Palladium Carbide Subnanometric Species in Zeolite Boosts Highly Selective Semihydrogenation of Alkynes

AbstractThe selective hydrogenation of alkynes to alkenes is a crucial step in the synthesis of fine chemicals. However, the widely utilized palladium (Pd)‐based catalysts often suffer from poor selectivity. In this work, we demonstrate a carbonization‐reduction method to create palladium carbide subnanometric species within pure silicate MFI zeolite. The carbon species can modify the electronic and steric characteristics of Pd species by forming the predominant Pd−C4 structure and, meanwhile, facilitate the desorption of alkenes by forming the Si−O−C structure with zeolite framework, as validated by the state‐of‐the‐art characterizations and theoretical calculations. The developed catalyst shows superior performance in the selective hydrogenation of alkynes over mild conditions (298 K, 2 bar H2), with 99 % selectivity to styrene at a complete conversion of phenylacetylene. In contrast, the zeolite‐encapsulated carbon‐free Pd catalyst and the commercial Lindlar catalyst show only 15 % and 14 % selectivity to styrene, respectively, under identical reaction conditions. The zeolite‐confined Pd‐carbide subnanoclusters promise their superior properties in semihydrogenation of alkynes.

Advances of Single‐Atomic Cobalt Catalysts in Liquid‐Phase Selective Oxidative Reactions

Single‐atom catalysts (SACs) composed of atomically dispersed metal‐active sites embedded in supporting substrates are attracting increasing attention in liquid‐phase selective oxidation reactions with joint merits of both advanced catalytic efficiency and high stability. Co‐based SACs present superior performance in several model oxidative reactions against many other metals, thus they are recognized as a promising solution to the current high‐cost noble‐metal catalysts required for the synthesis of fine chemicals. In this review, the up‐to‐date research on the synthesized Co–SACs in selective oxidation applications is summarized. The strategies of the preparation of Co–SACs with diverse Co‐loading levels and well‐tuned morphologies and chemical structures are showcased, as well as the characterization techniques of the SACs. The applications of Co–SACs in a series of selective oxidation reactions and the influence of different oxidants on the overall reaction efficiency are discussed. In addition, the progress of the mechanism exploration involving active‐site identification, catalytic activation of oxidants, and oxidation pathway elucidation is highlighted. Meanwhile, the existing challenges and the future efforts for the development of the Co–SAC reaction system in selective oxidation processes are outlined.

Synthesis of piperidines and pyridine from furfural over a surface single-atom alloy Ru1CoNP catalyst

The sustainable production of value-added N-heterocycles from available biomass allows to reduce the reliance on fossil resources and creates possibilities for economically and ecologically improved synthesis of fine and bulk chemicals. Herein, we present a unique Ru1CoNP/HAP surface single-atom alloy (SSAA) catalyst, which enables a new type of transformation from the bio-based platform chemical furfural to give N-heterocyclic piperidine. In the presence of NH3 and H2, the desired product is formed under mild conditions with a yield up to 93%. Kinetic studies show that the formation of piperidine proceeds via a series of reaction steps. Initially, in this cascade process, furfural amination to furfurylamine takes place, followed by hydrogenation to tetrahydrofurfurylamine (THFAM) and then ring rearrangement to piperidine. DFT calculations suggest that the Ru1CoNP SSAA structure facilitates the direct ring opening of THFAM resulting in 5-amino-1-pentanol which is quickly converted to piperidine. The value of the presented catalytic strategy is highlighted by the synthesis of an actual drug, alkylated piperidines, and pyridine.

Electrochemical Reversible Reforming between Ethylamine and Acetonitrile on Heterostructured Pd-Ni(OH)2 Nanosheets.

Rational design of electrocatalysts is essential to achieve desirable performance of electrochemical synthesis process. Heterostructured catalysts have thus attracted widespread attention due to their multifunctional intrinsic properties, and diverse catalytic applications with corresponding outstanding activities. Here, we report an in-situ restoration strategy for the synthesis of ultrathin Pd-Ni(OH)2 nanosheets. Such Pd-Ni(OH)2 nanosheets exhibit excellent activity and selectivity towards reversible electrochemical reforming of ethylamine and acetonitrile. In the acetonitrile reduction process, Pd acts as reaction center, while Ni(OH)2 provide proton hydrogen through promoting the dissociation of water. Also ethylamine oxidation process can be achieved on the surface of the heterostructured nanosheets with abundant Ni(II) defects. More importantly, an electrolytic cell driven by solar cells was successfully constructed to realize ethylamine-acetonitrile reversible reforming. This work demonstrates the importance of heterostructure engineering in the rational synthesis of multifunctional catalysts towards electrochemical synthesis of fine chemicals.

Electrochemical Reversible Reforming between Ethylamine and Acetonitrile on Heterostructured Pd‐Ni(OH)2 Nanosheets

AbstractRational design of electrocatalysts is essential to achieve desirable performance of electrochemical synthesis process. Heterostructured catalysts have thus attracted widespread attention due to their multifunctional intrinsic properties, and diverse catalytic applications with corresponding outstanding activities. Here, we report an in situ restoration strategy for the synthesis of ultrathin Pd‐Ni(OH)2 nanosheets. Such Pd‐Ni(OH)2 nanosheets exhibit excellent activity and selectivity towards reversible electrochemical reforming of ethylamine and acetonitrile. In the acetonitrile reduction process, Pd acts as reaction center, while Ni(OH)2 provide proton hydrogen through promoting the dissociation of water. Also ethylamine oxidation process can be achieved on the surface of the heterostructured nanosheets with abundant Ni(II) defects. More importantly, an electrolytic cell driven by solar cells was successfully constructed to realize ethylamine‐acetonitrile reversible reforming. This work demonstrates the importance of heterostructure engineering in the rational synthesis of multifunctional catalysts towards electrochemical synthesis of fine chemicals.

Cross-coupling by a noncanonical mechanism involving the addition of aryl halide to Cu(II).

Copper complexes are widely used in the synthesis of fine chemicals and materials to catalyze couplings of heteroatom nucleophiles with aryl halides. We show that cross-couplings catalyzed by some of the most active catalysts occur by a mechanism not previously considered. Copper(II) [Cu(II)] complexes of oxalamide ligands catalyze Ullmann coupling to form the C-O bond in aryl ethers by concerted oxidative addition of an aryl halide to Cu(II) to form a high-valent species that is stabilized by radical character on the oxalamide ligand. This mechanism diverges from those involving Cu(I) and Cu(III) intermediates that have been posited for other Ullmann-type couplings. The stability of the Cu(II) state leads to high turnover numbers, >1000 for the coupling of phenoxide with aryl chloride electrophiles, as well as an ability to run the reactions in air.

Microwave-Assisted Synthesis of Pd Nanoparticles into Wood Block (Pd@wood) as Efficient Catalyst for 4-Nitrophenol and Cr(VI) Reduction.

Palladium (Pd) nanoparticle catalysis has attracted increasing attention due to its efficient catalytic activity and its wide application in environmental protection and chemical synthesis. In this work, Pd nanoparticles (about 71 nm) were synthesized in aqueous solution by microwave-assisted thermal synthesis and immobilized in beech wood blocks as Pd@wood catalysts. The wood blocks were first hydrothermally treated with 10% NaOH solution to improve the internal structure and increase their porosity, thereby providing favorable attachment sites for the formed Pd nanoparticles. The stable deposition of Pd nanoparticle clusters on the internal channels of the wood blocks can be clearly observed. In addition, the catalytic performance of the prepared Pd@wood was investigated through two model reactions: the reduction of 4-nitrophenol and Cr(VI). The Pd@wood catalyst showed 95.4 g-1 s-1 M-1 of normalized rate constant knorm and 2.03 min-1 of the TOF, respectively. Furthermore, Pd nanoparticles are integrated into the internal structure of wood blocks by microwave-assisted thermal synthesis, which is an effective method for wood functionalization. It benefits metal nanoparticle catalysis in the synthesis of fine chemicals as well as in industrial wastewater treatment.

Zeolite nanocomposites with variable acid and basic properties: effective catalysts for fine chemical synthesis and industrial reaction

Zeolite nanocomposites with variable acid and basic properties: effective catalysts for fine chemical synthesis and industrial reaction