Carbon-carbon Coupling Reactions Research Articles

Highly Selective Acetylene-to-Ethylene Electroreduction Over Cd-Decorated Cu Catalyst with Efficiently Inhibited Carbon-Carbon Coupling.

Electrochemical acetylene reduction (EAR) employing Cu catalysts represents an environmentally friendly and cost-effective method for ethylene production and purification. However, Cu-based catalysts encounter product selectivity issues stemming from carbon-carbon coupling and other side reactions. We explored the use of secondary metals to modify Cu-based catalysts and identified Cd decoration as particular effective. Cd decoration demonstrated a high ethylene Faradaic efficiency (FE) of 98.38 % with well-inhibited carbon-carbon coupling reactions (0.06 % for butadiene FE at -0.5 V versus reversible hydrogen electrode) in a 5 vol % acetylene gas feed. Notably, ethylene selectivity of 99.99 % was achieved in the crude ethylene feed during prolonged stability tests. Theoretical calculations revealed that Cd metal accelerates the water dissociation on neighboring Cu surfaces allowing more H* to participate in the acetylene semi-hydrogenation, while increasing the energy barrier for carbon-carbon coupling, thereby contributing to a high ethylene semi-hydrogenation efficiency and significant inhibition of carbon-carbon coupling. This study provides a paradigm for a deeper understanding of secondary metals in regulating the product selectivity of EAR electrocatalysts.

Efficient heck and Suzuki-Miyaura cross-coupling reactions catalyzed by heterogeneous Pd NPs-decorated porous MOF catalysts under mild conditions

Carbon-carbon coupling reactions are extremely interesting for a variety of applications, including pharmaceuticals and biologically active compounds. In this study, we investigated the utilization of functionalized MIL-101 porous MOF for stabilizing palladium nanoparticles (NPs) and examined their catalytic performance in the cross-coupling reaction of aryl halides with phenylboronic acid and methyl acrylate under mild conditions. To achieve this, MIL-101(Al) was synthesized using a solvothermal method, followed by functionalization with environmentally friendly l-Cysteine (CYS). Subsequently, the MIL-101(Al)-CYS compound was immersed in an ethanolic solution of palladium and stirred overnight. The catalyst exhibited remarkable efficiency (over 90 %) in Suzuki and Heck cross-coupling reactions, demonstrating excellent activity and recyclability. The reactions were conducted in polyethylene glycol 200 (PEG 200), a green reaction medium, at temperatures of 70 °C and 60 °C, with Pd loadings of 0.22 and 0.08 mol%, respectively. MOF-based catalysts, owing to their highly tunable structures and porosity, hold great promise as heterogeneous catalysts in organic reactions.

Sulfur in Waste-Free Sustainable Synthesis: Advancing Carbon-Carbon Coupling Techniques.

This review explores the pivotal role of sulfur in advancing sustainable carbon-carbon (C-C) coupling reactions. The unique electronic properties of sulfur, as a soft Lewis base with significant mesomeric effect make it an excellent candidate for initiating radical transformations, directing C-H-activation, and facilitating cycloaddition and C-S bond dissociation reactions. These attributes are crucial for developing waste-free methodologies in green chemistry. Our mini-review is focused on existing sulfur-directed C-C coupling techniques, emphasizing their sustainability and comparing state-of-the-art methods with traditional approaches. The review highlights the importance of this research in addressing current challenges in organic synthesis and catalysis. The innovative use of sulfur in photocatalytic, electrochemical and metal-catalyzed processes not only exemplifies significant advancements in the field but also opens new avenues for environmentally friendly chemical processes. By focusing on atom economy and waste minimization, the analysis provides broad appeal and potential for future developments in sustainable organic chemistry.

Palladium on carbon-catalysed carbon-carbon coupling reactions of cyclohexanone (KA oil) and alkyl alcohols for the synthesis of zero net emission jet fuels

The cyclohexanone / cyclohexanol mixture (KA oil) is one of the most produced C6 chemicals worldwide, derived from renewable sources if desired; however, the use of KA oil as a precursor for zero net emission fuels has not been studied in-depth yet, as far as we know. We show here that KA oil is converted to an aromatic-free product mixture compatible with the composition of jet fuels after a series of carbon-carbon coupling reactions, of either KA oil with itself or with bioderived alcohols, in the presence of a commercially available solid-supported palladium on carbon catalyst under basic conditions (KOH). Water is the only by-product of the reaction, and phosphines can be used as ligands to variate the final product composition.

Theoretical calculations for modeling carbon-carbon coupling reactions on copper surface: A comprehensive review

Theoretical calculations for modeling carbon-carbon coupling reactions on copper surface: A comprehensive review

Palladium nanoparticles immobilized on N-decorated porous carbon as synergistic catalyst for carbon-carbon coupling reactions

N-decorated porous carbon (NDC) was obtained by one step direct pyrolysis of NH2−MIL-125. The content of nitrogen in the NDC-1000 (2 h) was 4.2 %. Palladium nanoparticle was deposited on the NDC by an impregnation strategy. The NDC-1000-Pd catalyst was characterized by powder X-ray diffraction, TEM, XPS and N2 adsorption. Due to the synergetic interaction of metal species and NDC, the catalyst exhibited excellent catalytic performance for Heck coupling and Suzuki-Miyaura reactions. The catalyst can be reused for five cycles without obvious change in its activity.

Controlling C–C coupling reactivity through pore shape engineering of B-doped graphyne family

Graphyne is an interesting carbon allotrope characterized by sp-sp2 hybridized carbon bonds, which allow for structure variability. Though there are studies evaluating the electrical and mechanical properties of various structures, studies utilizing its structural variety toward catalyst applications are minor. In electrocatalytic CO2 reduction reactions (CRR), producing valuable C2+ products, such as C2H4 or C2H5OH, under mild conditions is still challenging. The bottleneck has been assigned to the carbon-carbon (C–C) coupling reaction, such as 2*CO → *OCCO. In this reaction, one requires strong binding to the catalyst to enhance neighboring CO concentration, but at the same time, one needs to have low C–C coupling barriers making the OC-CO bond. Following our previous study, which showed B-doped γ-graphyne can be a catalyst for ethanol production, we conducted theoretical investigations on a range of B-doped graphyne families using density functional theory. Out of the 15 different structures studied, four, 4,12,2-, sR-, γ-, and 6,6,12-graphynes, show promising potential for CRR. B-doped 4,12,2-graphyne, with small square and rectangular pores, had a very low C–C coupling barrier of 0.34 eV with strong 2*CO adsorption (−2.5 eV). Furthermore, our research revealed a correlation between the heat of reaction (2*CO → *OCCO) and the average pore area around the acetylenic linker reaction site. Smaller pores give a favorable orientation of two CO molecules, resulting in low reaction barriers.

Micellar catalysis: Polymer bound palladium catalyst for carbon-carbon coupling reactions in water.

Metallosurfactants, defined here as hydrophobic metal-containing groups embedded in hydrophilic units when dispersed in water, emanate in the formation of metallomicelles. This approach continues to attract great interest for its ability to serve as micellar catalysts for various metal-mediated chemical transformations in water. Indeed, relevant to green chemistry, micellar catalysis plays a preeminent function as a replacement for organic solvents in a variety of chemical reactions. There are several methods for the interaction of metal complexes (catalysts or catalyst precursors) and surfactants for producing micellar aggregates. A very effective manner for achieving this involves the direct bonding of the metal center to the amphiphilic polymeric materials. Herein, we describe the synthesis of a metallosurfactant containing a palladium complex covalently incorporated into a CO2-based triblock polycarbonate derived using a dicarboxylic acid chain-transfer agent. This amphiphilic polycarbonate was shown to self-assemble in water to provide uniform and spherical micelles, where the catalytic metal center is located in the hydrophobic portion of the micelle. The resulting metallosurfactant was demonstrated to effectively catalyze carbon-carbon coupling reactions at very low catalyst loadings.

Catalytic Asymmetric Synthesis of Zinc Metallacycles.

Transition-metal-catalyzed reductive coupling reactions of alkynes and imines are attractive methods for the synthesis of chiral allylic amines. Mechanistically, these reactions involve oxidative cyclization of the alkyne and the imine to generate a metallacyclic intermediate, which then reacts with H2 or a H2 surrogate to form the product. As an alternative to this hydrogenolysis pathway, here we show that transmetalation to zinc can occur, forming a zinc metallacycle product. This organozinc product serves as a versatile nucleophile for carbon-carbon and carbon-heteroatom coupling reactions. Mechanistic studies based on isotopic labeling experiments and DFT calculations suggest that the key transmetalation step occurs between a Co(II) species and ZnCl2.

Palladium immobilized in Fe3O4@PEG/cryptand 222 core-shell nanostructure for enhanced cross-coupling reactions under sonication

The ultrasound-assisted reaction has been regarded as a promising strategy for boosting cross-coupling reactions. Herein, we described the ultrasound-assisted carbon-carbon, carbon-nitrogen, and carbon-oxygen coupling reactions via Pd@Crypt-222/Fe3O4@PEG core-shell nanostructure. First, the Fe3O4@PEG core-shell nanostructure was prepared and then cryptand 222 (Crypt-222) ligand was decorated onto the surface catalyst for coordinating palladium (Pd) ions. Well-affinity Crypt-222 ligand toward adsorption of Pd ions had a prominent role in the long-term stability of Pd. X-ray diffraction (XRD) pattern and Fourier transform infrared spectroscopy (FT-IR) spectra revealed that Crypt-222 ligand and Pd ions have successfully stabilized on the surface of Fe3O4@PEG. The synergistic effect of the catalyst with ultrasound irradiation enhanced the activity of the Pd ions in the cycle of the cross-coupling reactions, which significantly decreased the reaction time and temperature. Meanwhile, the results revealed that the proposed nanostructure could be conveniently recovered by applying an external magnetic field. The present study not only provides new horizons into the design of magnetic-based core-shell structures but also develops ultrasound-assisted reactions.

Facile Synthesis Hyper-Crosslinked PdFe Bimetallic Polymer as Highly Active Catalyst for Ullmann Coupling Reaction of Chlorobenzene.

The synthesis of efficient and sustainable heterogeneous Pd-based catalysts has been an active field of research due to their crucial role in carbon-carbon coupling reactions. In this study, we developed a facile and eco-friendly in situ assembly technique to produce a PdFe bimetallic hyper-crosslinked polymer (HCP@Pd/Fe) to use as a highly active and durable catalyst in the Ullmann reaction. The HCP@Pd/Fe catalyst exhibits a hierarchical pore structure, high specific surface area, and uniform distribution of active sites, which promote catalytic activity and stability. Under mild conditions, the HCP@Pd/Fe catalyst is capable of efficiently catalyzing the Ullmann reaction of aryl chlorides in aqueous media. The exceptional catalytic performance of HCP@Pd/Fe is attributed to its robust absorption capability, high dispersion, and strong interaction between Fe and Pd, as confirmed by various material characterizations and control experiments. Furthermore, the coated structure of a hyper-crosslinked polymer enables easy recycling and reuse of the catalyst for at least 10 cycles without any significant loss of activity.

Multi-radicals mediated one-step conversion of methane to acetic acid via photocatalysis

One-step photocatalytic methane conversion to acetic acid possesses high economic and academic value, and carbonyl species (CO, CO2) are usually necessary to be introduced into the reaction system to realize the carbon-carbon coupling reaction, which requires high energy input. In this work, a composite photocatalyst (Ag/AgCl-WO3-x) was constructed to successfully realize the one-step photocatalytic conversion of CH4 to CH3COOH without addition of carbonyl species. Chlorine radicals and hydroxyl radicals could be produced simultaneously under light irradiation over Ag/AgCl. Specifically, CH4 could undergo the hydrogen atom transfer reaction with chlorine radicals to produce methyl species, and hydroxyl radicals could mineralize CH4 to produce carbonyl species. After further combining WO3−x, carbon-carbon coupling reaction between carbonyl and methyl species occurred to effectively produce CH3COOH (188.5 μmol·gcat−1·h−1). This work provides a new prospect of designing photocatalytic system to realize CH4 conversion to C2 products.

Development of an in vitro method for activation of X-succinate synthases for fumarate hydroalkylation

Anaerobic microbial degradation of hydrocarbons is often initiated through addition of the hydrocarbon to fumarate by enzymes known as X-succinate synthases (XSSs). XSSs use a glycyl radical cofactor, which is installed by an activating enzyme (XSS-AE), to catalyze this carbon-carbon coupling reaction. The activation step, although crucial for catalysis, has not previously been possible invitro because of insolubility of XSS-AEs. Here, we take a genome mining approach to find an XSS-AE, a 4-isopropylbenzylsuccinate synthase (IBSS)-AE (IbsAE) that can be solubly expressed in Escherichia coli. This soluble XSS-AE can activate both IBSS and the well-studied benzylsuccinate synthase (BSS) invitro, allowing us to explore XSSs biochemically. To start, we examine the role of BSS subunits and find that the beta subunit accelerates the rate of hydrocarbon addition. Looking forward, the methodology and insight gathered here can be used more broadly to understand and engineer XSSs as synthetically useful biocatalysts.

Mechanistic Views on the Manganese Catalyzed Homogeneous Coupling Reactions

Abstract: The transition metal-catalyzed C-C and C-X (X=heteroatom) homo and crosscoupling reactions were pioneered as a momentous strategy for the total synthesis of natural products, agrochemicals, pharmaceuticals, etc. Among the various transition metal-catalyzed reactions, manganese catalysis held a distinctive identity owing to its earth-abundance and eco-friendliness apart from its unique characteristics. Despite having many synthetic advancements, exploiting manganese as a catalyst for coupling reactions has recently gained pivotal gravity. An in-depth comprehension of the molecular mechanism of the chemical reaction will provide further insight to optimize the reaction conditions. The mechanisms adopted by Mn-catalyzed couplings are found to differ from other first-row transition metal counterparts. Hence in this article, we provide the state-of-the-art on the detailed theoretical aspects of manganese-catalyzed carbon-carbon (C-C) and carbon-heteroatom (C-X; X=Si) coupling reactions.

Photoluminescent nickel(II) carbene complexes with ligand-to-ligand charge-transfer excited states

While nickel(II) complexes have been widely used as catalysts for carbon-carbon coupling reactions, the exploration of their photophysical and photochemical properties is still in the infancy. Here, a series of square-planar Ni(II) complexes [(diNHC)NiX2] bearing chelating benzimidazole-based bis(N-heterocyclic carbene) ligands and varying anionic coligands (1, X = Cl; 2, X = Br; 3, X = I) are synthesized and structurally characterized. In solid state, both 1 and 2 exhibit orange-red photoluminescence under ambient conditions. The photophysical and electrochemical measurements along with density functional theory (DFT) calculations reveal that the low-energy emissions can be attributed to singlet excited states with ligand-to-ligand charge-transfer (LLCT) character. This work suggests that strong-field N-heterocyclic carbene ligands play a crucial role to achieve the luminescence of Ni(II) complexes.

Recent advances in synthesis of stilbene derivatives via cross-coupling reaction.

The stilbenes are undoubtedly some of the most significant moieties in various bioactive natural and synthetic structures, and they are considered privileged structures. In recent years, the preparation of these structures via cross-coupling reactions has attracted much attention. In the current review, we present a summary of the recent developments in the construction of stilbene and stilbene derivatives by carbon-carbon coupling reactions of organic compounds in the presence of transition metal catalysts or under metal-free conditions. In this context, we outline the features of the important reactions, some product yields, and challenging reaction mechanisms.

Mechanism of Carbon-Carbon Coupling Reactions Catalyzed by Imine-Ligand-Assisted N-Heterocyclic Carbene Palladium Complexes

Mechanism of Carbon-Carbon Coupling Reactions Catalyzed by Imine-Ligand-Assisted N-Heterocyclic Carbene Palladium Complexes

Efficient Ullmann and Suzuki-Miyaura cross-coupling reactions catalyzed by heterogeneous Pd-porous carbon beads catalysts in aqueous media

Carbon-carbon coupling reactions are of great interest for a wide range of applications including pharmaceutical compounds and biologically active molecules. Usually, coupling reactions were performed using a homogeneous catalyst and organic solvent. Thus, the use of greener solvents as well as the heterogenization of the classical metal-based catalyst are desirable and still under development. This contribution describes the synthesis of biaryl compounds in water by Ullmann and Suzuki reactions with carbon-supported Pd nanoparticles. As expected, the microwave activation method drastically decrease the reaction time. The utilization of trioctylphosphine (TOP) or triphenylphosphine (TPP) ligands slow down the Pd leaching without cancelling it compared to the unliganded Pd catalyst. Moreover, a treatment with H2O2 appears beneficial with respect to a thermal-oxidative treatment at 1500 °C due to higher hydrophilicity of the resultant carbon support. These results and methodology contribute to a greener future for C–C coupling reactions.

Ultramicroporous Organophosphorus Polymers via Self-Accelerating P-C Coupling Reactions: Kinetic Effects on Crosslinking Environments and Porous Structures.

Porous organic polymers (POPs) have drawn significant attention in diverse applications. However, factors affecting the heterogeneous polymerization and porosity of POPs are still not well understood. Herein, we report a new strategy to construct porous organophosphorus polymers (POPPs) with high surface areas (1283 m2/g) and ultramicroporous structures (0.67 nm). The strategy harnesses an efficient transition-metal-catalyzed phosphorus-carbon (P-C) coupling reaction at the trigonal pyramidal P-center, which is distinct from the typical carbon-carbon coupling reaction utilized in the synthesis of POPs. As the first kinetic study on the coupling reaction of POPs, we uncovered a self-accelerating reaction characteristic, which is controlled by the choice of bases and catalysts. The self-accelerating characteristic of the P-C coupling reaction is beneficial for the high surface area and uniform ultramicroporosity of POPPs. The direct crosslinking of the P-centers allows 31P solid-state (ss)NMR experiments to unambiguously reveal the crosslinking environments of POPPs. Leveraging on the kinetic studies and 31P ssNMR studies, we were able to reveal the kinetic effects of the P-C coupling reaction on both the crosslinking environments and the porous structures of POPPs. Furthermore, our studies show that the CO2 uptake capacity of POPPs is highly dependent on their porous structures. Overall, our studies paves the way to design new POPs with better controlled chemical and ultramicroporous structures, which have potential applications for CO2 capture and separation.

Synthesis, Characterization, and XPS Study of Woolen-Like Zeolite X-Palladium Nanoparticles: Its Application as a Suitable Catalyst for Carbon-Carbon Coupling Reaction

Synthesis, Characterization, and XPS Study of Woolen-Like Zeolite X-Palladium Nanoparticles: Its Application as a Suitable Catalyst for Carbon-Carbon Coupling Reaction