Homocoupling Of Arylboronic Acids Research Articles

Oyster shell powder-gold nanoparticle composites as a reactive, recyclable, and green catalyst

Oyster shell waste can be utilized as a colloidal solid support to anchor abundant gold nanoparticles (AuNPs) for use as a highly selective, reactive, and recyclable catalyst in C-C bond forming reactions under base-free green reaction conditions. A deposition precipitation method is utilized to effectively incorporate sub-10 nm AuNPs onto the ground oyster shell powder (OSP). Although the loaded AuNPs mainly possess bare surfaces without any capping agents, the resulting composite particles exhibited great dispersity and stability in various solvents, including EtOH and water. After examining their structural and compositional properties, the composite particles are tested as a catalyst in C-C bond forming reactions. These composite particles reveal an unexpectedly high reactivity and selectivity in the homocoupling of arylboronic acid without using any additives, including necessary inorganic bases. This is presumably because the abundant carbonate groups around the OSP surfaces can effectively play a role as a base, while the bare surfaces of the incorporated AuNPs act as catalytically reactive sites. In addition to these synergistic features of the composite particles, establishing reliable reaction conditions requiring only reactants in a green EtOH solvent results in the easy isolation of the product and catalyst, yielding great recyclability. The utilization of marine wastes along with biocompatible and catalytically active metal nanoparticles will lead to the development of economical multi-purpose catalysts that are extremely practical and recyclable in eco-friendly reaction conditions.

Adsorption of Cu2+ by modified chitosan microspheres and its application in homocoupling of arylboronic acid

The C C bond coupling reactions have a wide range of applications in the synthesis of natural substances and the synthesis of physiologically active compounds. We first prepared modified chitosan microspheres by emulsification and investigated the performance of the chitosan adsorbent for the adsorption of copper ions. We then evaluated the catalytic performance of chitosan-supported copper microspheres in the self-coupling of arylboronic acids using 4-methoxybenzene as the model substrate, while exploring a wide range of substrates including aryl boronic acid derivatives and heterocyclic arylboronic acids, including aldehyde, nitro, and aldehyde groups. The experimental results show that good to excellent yields (55%-95%) of the desired dimer products were obtained under mild conditions at room temperature and in air, and the catalytic material could be reused up to five times with no significant decrease in catalytic activity.

Construction of CuII Defects on CuCl Nanoparticles in Metal-Organic Frameworks toward Composite Catalysts with Superior Activity.

Metal-organic frameworks (MOFs) represent an ideal platform for the construction of highly active composite catalysts. However, loading metastable and/or multicomponent metal compounds into MOFs remains a synthetic bottleneck due to the great challenge of keeping the guest and matrix intact during the preparation of a composite. In this work, we develop a new impregnation reduction surface modification (IRSM) strategy to give a new composite catalyst CuCl@MIL-101(Cr), which is successfully postmodified by in situ construction of CuII defects on the surface of loaded CuCl inside MOF pores, leading to the new composite material CuII/CuI@MIL-101(Cr). The new dual-component composite catalyst exhibits a hierarchical structure and superior catalytic activity in C-C homocoupling of arylboronic acids under green conditions. This study presents a facile strategy for improving the catalytic activity by constructing defects on the surface of MOF-based catalysts as well as for forming multiple-component composite materials.

Size-Selective Homocoupling of Arylboronic Acids Mediated by a Copper-Based Metal–Organic-Framework

Size-Selective Homocoupling of Arylboronic Acids Mediated by a Copper-Based Metal–Organic-Framework

Systematic Incorporation of Gold Nanoparticles onto Mesoporous Titanium Oxide Particles for Green Catalysts

This report describes the systematic incorporation of gold nanoparticles (AuNPs) onto mesoporous TiO2 (MPT) particles without strong attractive forces to efficiently serve as reactive and recyclable catalysts in the homocoupling of arylboronic acid in green reaction conditions. Unlike using nonporous TiO2 particles and conventional SiO2 particles as supporting materials, the employment of MPT particles significantly improves the loading efficiency of AuNPs. The incorporated AuNPs are less than 10 nm in diameter, regardless of the amount of applied gold ions, and their surfaces, free from any modifiers, act as highly reactive catalytic sites to notably improve the yields in the homocoupling reaction. The overall physical properties of the AuNPs integrated onto the MPT particles are thoroughly examined as functions of the gold content, and their catalytic functions, including the rate of reaction, activation energy, and recyclability, are also evaluated. While the rate of reaction slightly increases with the improved loading efficiency of AuNPs, the apparent activation energies do not clearly show any correlation with the size or distribution of the AuNPs under our reaction conditions. Understanding the formation of these types of composite particles and their catalytic functions could lead to the development of highly practical, quasi-homogeneous catalysts in environmentally friendly reaction conditions.

Electro-Oxidative Coupling Reactions Leading to π-Conjugated Compounds.

Electrochemical reactions are rapidly gaining attention today as a powerful and environmentally benign reaction processes for organic synthesis. We found that the electro-oxidation of palladium acetate afforded cationic palladium species and thus-generated cationic Pd species were efficient mediators for electro-oxidative coupling reactions. Homo-coupling of arylboronic acids and terminal alkynes proceeded efficiently to afford biaryls and butadiyne, respectively. Cross-coupling reactions between terminal alkynes and arylboronic acids were also achieved with the use of a Ag anode. As an advantage of electrochemical reactions, we developed a sequential reaction system switched between oxidative and neutral conditions by the on/off application of electricity, and several π-extended butadiynes were obtained in one-sequence by the system. Electrochemical intramolecular C-S coupling for the synthesis of thienoacene was also developed. The use of Bu4 NBr as a halogen mediator was essential for the reaction.

Sustainable Synthesis of Biaryls Using Silica Supported Ferrocene Appended N-Heterocyclic Carbene-Palladium Complex

A novel silica supported ferrocene appended N-heterocyclic carbene-palladium complex (SilFemBenzNHC@Pd) has been prepared and characterized by using fourier transform infrared (FT-IR), fourier transform Raman (FT-Raman), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and energy dispersive X-ray analysis (EDX). This novel complex served as a robust heterogeneous catalyst for the synthesis of biaryls via homocoupling of aryl boronic acids under base-free conditions in water. Recyclability experiments were executed successfully for six successive runs.

Stability of Palladium(II) beta-cyclodextrin nanocomposite in aqueous media and its catalytic activity in Homocoupling of Arylboronic acid

Stability of Palladium(II) beta-cyclodextrin nanocomposite in aqueous media and its catalytic activity in Homocoupling of Arylboronic acid

Functionalized NHC-incorporated Te−Fe−Cu clusters: Facile synthesis, electrochemistry, and catalytic reaction

Two novel TeFe3(CO)9-containing functionalized NHC dicopper complexes, [TeFe3(CO)9{Cu(Me2-bimy)}2] (1) and [TeFe3(CO)9{Cu(iPr2-bimy)}2] (2), were prepared from the reaction of the ternary Te−Fe−Cu complex [TeFe3(CO)9{Cu(MeCN)}2] with bis-N-methyl- or bis-N-isopropyl-substituted benzimidazol-2-ylidene (Me2-bimy or iPr2-bimy) under appropriate conditions, respectively. X-ray analysis showed that Me2-bimy-introduced complex 1 displayed a TeFe3(CO)9Cu(Me2-bimy) trigonal-bipyramidal core geometry having the Fe2Cu face capped by a Cu(Me2-bimy) fragment with the two bonded Cu atoms, whereas the bulkier iPr2-bimy-incorporated complex 2 exhibited a similar TeFe3(CO)9Cu(iPr2-bimy) core having the Fe3 triangle coordinated by a Cu(iPr2-bimy) fragment with the two unbonded Cu atoms. On the other hand, when [TeFe3(CO)9{Cu(MeCN)}2] reacted with the 4,5-dichloro-substituted 1,3-dimethylimidazolium salt (Me2-Cl2-imy·HI) in the presence of KOtBu, a different type of [TeFe3(CO)9{Cu(Me2-Cl2-imy)}2] (3) was produced in good yields. Cluster 3 was shown to possess a tetrahedral TeFe3 core geometry in which the two Fe−Fe edges were each bridged by a Cu(Me2-Cl2-imy) group. According to solid-state packings, complex 1 revealed a cluster-based 3D-supramolecular framework and complexes 2 and 3 each formed a 1D-supramolecular chain, which was stabilized by intermolecular C−H…O interactions between COs and CH moieties of the corresponding NHC ligands. Further, these di-Cu(I) based complexes 1−3 exhibited catalytic activities toward the homocoupling of arylboronic acid with high yields. Importantly, the catalytic efficiencies of this series of functionalized NHC-incorporated TeFe3(CO)9Cu2-based complexes perfectly paralleled the ease of their first oxidation and the greater electron density of the carbene atom in the NHC ligands, which was elucidated by electrochemistry, 13C NMR, and DFT calculations.

Ternary copper-incorporated group 8 (Ru or Fe) carbonyl chalcogenide complexes and polymers: From syntheses to applications

Main-group element-containing mixed-metal carbonyl complexes represent an important field of contemporary chemistry. This account will focus on the development of Cu-incorporated group 8 (Ru or Fe) carbonyl chalcogenide complexes, and will represent a review and discussion, mainly from our group and others, of the rational synthetic methodologies, controlled cluster-growth processes, transformations, as well as their special applications in areas of semiconductors and catalysis. The description of this review is arranged by four types of building blocks, ERu5-, Te2Ru4Cu2-, EFe3-, and TeFe3Cu2-based (E = Te, Se, S) carbonyl clusters, which can further react with copper sources, CuX (X = Cl, Br, I) and [Cu(MeCN)4][BF4], or toward inorganic and organic reagents to construct the ternary E‒M‒Cu‒CO (M = Ru, Fe) complexes or polymers. The NHC-decorated TeFe3Cu2-based complexes exhibited pronounced catalytic activities toward the homocoupling of arylboronic acids with low copper loadings and high yields. Further, the energy gaps of these ternary carbonyl complexes were systematically studied in terms of chalcogen and halide effects, and most importantly, the size and dimensionality of these complexes.

An Operationally Simple and Mild Oxidative Homocoupling of Aryl Boronic Esters To Access Conformationally Constrained Macrocycles.

Constrained macrocyclic scaffolds are recognized as challenging synthetic motifs with few general macrocyclization methods capable of accessing these types of systems. Although palladium catalyzed oxidative homocoupling of aryl boronic acids and esters to biphenyls has been recognized as a common byproduct in Suzuki-Miyaura cross-couplings for decades, this reactivity has not been leveraged for the synthesis of challenging molecules. Here we report an oxidative boronic ester homocoupling reaction as a mild method for the synthesis of strained and conformationally restricted macrocycles. Higher yields and better efficiencies are observed for intramolecular diboronic ester homocouplings when directly compared to the analogous intramolecular Suzuki-Miyaura cross-couplings or reductive Yamamoto homocouplings. Substrates included strained polyphenylene macrocycles, strained cycloalkynes, and a key macrocyclic intermediate toward the synthesis of acerogenin A. Notably, this oxidative homocoupling reaction is performed at room temperature, open to atmosphere, and without the need to rigorously exclude water, thus representing an operationally simple alternative to traditional cross-coupling macrocyclizations. The mechanism of the reaction was investigated indicating that 1-5 nm palladium nanoparticles may serve as the active catalyst.

Active Palladium Colloids via Palladacycle Degradation as Efficient Catalysts for Oxidative Homocoupling and Cross-Coupling of Aryl Boronic Acids

Active palladium colloids formed upon degradation of a palladacyclic complex (Herrmann–Beller 1) have been isolated for the first time and thoroughly characterized with techniques such as transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure spectroscopy. The synthesized palladium colloids have been utilized as efficient catalysts for the oxidative homocoupling of aryl boronic acids. Cross-coupling of two different aryl boronic acids has also been made possible using these active palladium colloids. This is the first report of this kind of coupling between aryl boronic acids.

ChemInform Abstract: [Pd(Phbz)(X)(PPh3)] Palladacycles Promote the Base‐Free Homocoupling of Arylboronic Acids in Air at Room Temperature.

Homocoupling of arylboronic acids can be successfully achieved in commercial grade THF using [Pd(Phbz)(X)(PPh3)] palladacycles as catalysts (Phbz = N-phenylbenzaldimine; X = imidate or acetate). Symmetric biaryls were obtained in good yields working under mild conditions in an air atmosphere at room temperature. The reaction occurs without the addition of an exogenous base. The reaction conditions were optimized to provide the homocoupled products in excellent yield. Evidence for the transmetallation step being important for precatalyst activation has been gathered. The influence of electronic properties of the arylboronic acids on the outcome of the homocoupling reaction has been assessed through competition experiments.

Homocoupling of Arylboronic Acids Catalyzed by a Simple Hydrophilic Palladium(II) Complex in Aqueous Media

Homocoupling of arylboronic acids has been successfully carried out by using the inexpensive hydrophilic palladium( II) complex PdCl2(NH2CH2COOH)2 as catalyst in i-PrOH/H2O (v/v=1:2) under aerobic atmosphere without elevated heating to give rise to symmetrical biaryls in moderate to good yields. The aqueous media, room temperature reaction and the low amounts of catalyst (0.5 mol%) show a practical and environmentally benign protocol. In addition, enhancement of yield was observed in the presence of 0.5 equiv. p-toluenesulfonyl chloride. Furthermore, the byproducts of this reaction were not observed while biaryl is the only product, which results in much more facile in the separation of the product symmetrical biaryls from arylboronic acids. Keywords: Hydrophilic catalyst, homocoupling of arylboronic acids, aqueous media, green chemistry.

電気化学的な酸化プロセスを含むカップリング反応の開発と拡張π電子系化合物合成への応用

An electrochemical method to synthesize cationic palladium complexes has been developed. Their counter anions could be changed readily by the electrolyte. The reaction could be incorporated into electro-oxidative palladium catalyzed reactions, such as Wacker-type reaction, homo-coupling of arylboronic acids, oxidative Sonogashira-type coupling, and Glaser-type coupling of terminal alkynes. These reactions exhibited a wide scope and a variety of products were obtained in high yields due to high activity of electrogenerated palladium species. We also developed site-selective sequential reactions by the integration of the electro-oxidative coupling reactions with non-electrochemical reactions. The reaction site could be controlled completely by the on/off application of electricity.

Iron carbonyl cluster-incorporated Cu(I) NHC complexes in homocoupling of arylboronic acids: an effective [TeFe3(CO)9](2-) ligand.

A new type of TeFe3(CO)9-incorporated dicopper NHC complex was obtained directly from one-pot reactions. By the introduction of the cluster anion [TeFe3(CO)9](2-) and NHCs as the ligands, these di-Cu(i)-based complexes exhibited pronounced catalytic activities toward the homocoupling of arylboronic acids with low Cu loadings and high yields (up to 98%).

ChemInform Abstract: Amine‐Bridged Bis(phenol) Ligands for Efficient Pd‐Catalyzed Aqueous C—C Coupling Reactions.

AbstractA highly efficient protocol for the Pd‐catalyzed homocoupling of arylboronic acids (I) as well as Suzuki—Miyaura reactions in aqueous media is developed.

Design of novel indium oxide supported gold nanocatalysts and their application in homocoupling of arylboronic acids

Gold (Au) nanoparticles stabilized on metal oxide supports offer superior catalytic activity and recyclability in organic catalysis. We report for the first time synthesis of indium oxide stabilized gold (Au@In2O3) nanocatalysts using an electrochemical procedure and their application in homocoupling of arylboronic acids. In2O3 nanoparticles prepared via sol-gel process are subjected to sacrificial anode electrolysis (SAE) under inert condition for electrodeposition of nano Au on In2O3. Thus Au@In2O3 nanoparticles obtained are thermally annealed at high temperature to partially oxidize Au and to remove any surfactants. XPS results show the existence of both elemental (nano Au0) and cationic (Au3+) species in Au@In2O3 nanocatalysts, while SEM images confirm the presence of nanoscale Au (<10nm) particles on In2O3 surface. Au@In2O3 nanocatalysts are tested for arylboronic acids homocoupling under different conditions and it is found that they are highly active in organic medium with K2CO3 base and demonstrate excellent conversion (>97%) and selectivity (>98%). The catalyst recyclability and performance towards differently substituted arylboronic acids is also studied and a plausible mechanism of action is proposed.

Correction: [Pd(Phbz)(X)(PPh3)] palladacycles promote the base-free homocoupling of arylboronic acids in air at room temperature

Correction: [Pd(Phbz)(X)(PPh₃)] palladacycles promote the base-free homocoupling of arylboronic acids in air at room temperature

ChemInform Abstract: Fe3O4 Nanoparticle‐Supported Cu(II)‐β‐Cyclodextrin Complex as a Magnetically Recoverable and Reusable Catalyst for the Synthesis of Symmetrical Biaryls and 1,2,3‐Triazoles from Aryl Boronic Acids.

We report here on the preparation of an efficient, easily recoverable and reusable Fe3O4 magnetic nanoparticle-supported Cu(II)-β-cyclodextrin complex catalyst for the synthesis of symmetrical biaryls and 1,2,3-triazoles from arylboronic acids. The presented Fe3O4 magnetic nanoparticle-supported Cu(II)-β-cyclodextrin complex catalyst was characterized by TEM, XRD, VSM, TGA, and FT-IR spectrometer. By using the catalyst, we have developed an efficient protocol for the homocoupling of aryl boronic acids for the synthesis of biaryls. The catalyst is also active in the synthesis of 1,2,3-triazoles via a one-pot reaction of an arylboronic acid with sodium azide in water followed by a click cyclization reaction with an alkyne at room temperature in air without any additives. The reusability of the prepared nanocatalyst was successfully examined four times with only a very slight loss of catalytic activity.