Miyaura Coupling Reaction Research Articles

EDTA-functionalized metal–organic framework of TMU-16-NH2 decorated with Pd nanoparticles as an efficient and effective nanocatalyst in the Suzuki – Miyaura coupling reaction

EDTA-functionalized metal–organic framework of TMU-16-NH2 decorated with Pd nanoparticles as an efficient and effective nanocatalyst in the Suzuki – Miyaura coupling reaction

AuxPdy‐based Heterogeneous Nanocatalysts for Plasmon‐mediated Enhanced Catalysis under Visible Light Irradiation

AbstractThe formation of hybrid plasmonic nanocatalysts made of Au nanoparticles (NPs) combined with catalytically active NPs has gained great attention owing to their interesting properties and efficient catalysis under visible light irradiation. However, the research on the combination of plasmonic metal NPs with unique support frameworks is still limited. In this report, the varying ratio of AuxPdy prepared by the extrusion method on the CuClP framework has been correlated to its optimized catalysis in the Suzuki‐Miyaura coupling reaction in dark and under visible light irradiation. The prepared catalysts AuxPdy/CuClP were characterized by spectroscopic techniques to understand the structural and electronic modification with different metal ratios. The presence of bimetallic NPs on the surface was confirmed by HR‐TEM measurements and [MCl4]n− species in the framework were validated by XPS, FT‐EXAFS, DR UV‐Vis‐NIR, and Raman analysis. The obtained results display the superior catalytic performance and highest plasmonic enhancement factor over Au1Pd1/CuClP under visible light irradiation, which was facilely recycled and reused for several cycles. The hot‐electron transfer mechanism has been discussed for enhanced catalysis in the plasmon‐driven Suzuki−Miyaura coupling reaction. These results are highly significant in the rational design of new plasmonic photocatalysts combined with unique support materials.

Oxime ligands for Pd catalysis of the Mizoroki–Heck reaction, Suzuki–Miyaura coupling & annulation reactions

Monodentate and bidentate chelating oximes are readily available ligands for the Pd catalysis of the Mizoroki–Heck reaction and the Suzuki coupling. High yields were obtained in the Suzuki coupling in aqueous dioxane with TBABr as additive. The oximes can be easily synthesized from the corresponding ketones or aldehydes and thus provide a very large number of nitrogen-based ligands. They have the advantage of not undergoing oxidative degradation, common for phosphine ligands. Chelating oximes with Pd(OAc)2, activate aryl iodides to give high yields of the substitution products in the Mizoroki–Heck reactions as well as the Suzuki coupling. Acetophenone oxime ligand with Pd(OAc)2, catalyzed the reaction of aryl iodides with 1,2-disubstituted alkenes in moderate to high yields. As a test example, the LaRock indole annulation and synthesis of isocoumarin were achieved with acetophenone oxime ligand and Pd(OAc)2 in high yields.

Immobilized Pd on a NHC functionalized metal–organic framework MIL‐101(Cr): an efficient heterogeneous catalyst in Suzuki−Miyaura coupling reaction in water

A novel Pd−NHC functionalized metal–organic framework (MOF) based on MIL‐101(Cr) was synthesized and used as an efficient heterogeneous catalyst in the C‐C bond formation reactions. Using this heterogeneous Pd catalyst system, the Suzuki−Miyaura coupling reaction was accomplished well in water, and coupling products were obtained in good to excellent yields in short reaction time. The Pd−NHC−MIL‐101(Cr) was characterized using some different techniques, including Fourier transform‐infrared, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy, inductively coupled plasma and elemental analysis. The microscopic techniques showed the discrete octahedron structure of MIL‐101(Cr), which is also stable after chemical modification process to prepare the catalyst system. The TEM images of the catalyst showed the existence of palladium nanoparticles immobilized in the structure of the catalyst, while no reducing agent was used. It seems that the NHC groups and imidazolium moieties in the structure of the MOF can reduce Pd (II) to Pd (0) species. This modified MOF substrate can also prevent aggregation of Pd nanoparticles, resulting in high stability of them in organic transformation. The Pd−NHC−MIL‐101(Cr) catalyst system could be simply extracted from the reaction mixture, providing an efficient synthetic method for the synthesis of biaryls derivatives using the aforementioned coupling reaction. The Pd−NHC−MIL‐101(Cr) catalyst could be recycled in this organic reaction with almost consistent catalytic efficiency.

Fabrication of BixPdy bimetallic materials characterized by catalytic activity at low temperature: Nitro reduction and Suzuki−Miyaura coupling reactions under green conditions

A simple method for synthesizing the BixPdy bimetallic particles is described. The structure, composition distribution and size of synthesized BixPdy bimetallic particles were characterized using a number of analytical techniques. The Bi:Pd atomic ratio (x:y) of the nanoparticles was determined to be approximately 1:3 (Bi24Pd76), 1:1 (Bi54Pd46) and 3:1 (Bi74Pd26). The (111) diffraction peaks within the X-ray diffraction patterns of the bimetallic nanoparticles shifted from 39.9° to 38.5° as the Bi content increased from 0% to 75%. The d-spacings calculated from the 2θ data of (111) planes were 2.33, 2.34, 2.32 and 2.26 nm for nanoparticles with a Bi:Pd atomic ratio of 3:1, 1:1, 1:3 and 0:1 respectively. The crystalline properties of the surface of the BixPdy bimetallic nanoparticles were observed in high-resolution transmission electron microscopy analysis. The d-spacings between the adjacent lattice planes were measured on the surface of BixPdy bimetallic nanoparticles by averaging 10 lattice fringes distance. A regular face-centered cubic lattice was observed throughout the prepared BixPdy bimetallic nanoparticles. The lattice d-spacing of the Bi3Pd1, Bi1Pd1 and Bi1Pd3, bimetallic nanoparticles was approximately 2.34, 2.33 and 2.32 Å, respectively, which can be indexed to the (111) planes. These measurements correspond to the values calculated using the Bragg equation (d = nλ/2sinθ). The catalytic activity of BixPdy bimetallic nanoparticles was determined for the nitro compound reduction and Suzuki-Miyaura coupling reactions under green conditions (in an aqueous solution). Bi1Pd3 nanoparticles were shown to provide the best catalytic performance during both reactions, resulting in a yield of 98% in both cases.

Palladium-Alumoxane Framework as a Novel and Reusable Nanocatalyst for Suzuki–Miyaura, Stille and Heck Cross Coupling Reactions

Herein for the first time, a Schiff base alumoxane-supported palladium (SBA-Pd°) were successfully synthesized and reported as a new mesoporous nanocatalyst for C–C cross coupling reactions. The SBA-Pd° nanocatalyst could be dispersed in poly(ethylene glycol) and showed excellent catalytic activity for Suzuki–Miyaura, Stille and Heck coupling reactions. In addition, the nanocatalyst could be recovered and reused several times without significant loss of its catalytic activity. Pd leaching from SBA-Pd° is very negligible for this coupling reaction.

Contribution of heterobifunctional ligands to transition metal-catalysed C--C coupling reactions

In this account the authors' latest results in C--C coupling catalysis are reviewed. First, an efficient catalytic system for the Kumada--Tamao--Corriu coupling reaction based on NHC-phosphine (NHC = N-heterocyclic carbene) nickel complexes is presented. Then the use of palladium complexes of chiral ferrocenyl NHC-phosphines in the asymmetric Suzuki--Miyaura coupling reaction is reported. High catalytic activities and moderate enantioselectivities (ee up to 46{\%}) were obtained. Chiral ferrocenyl phosphine--ethers were also tested in the asymmetric Suzuki--Miyaura reaction yielding good activities and moderate enantioselectivities (ee up to 37{\%}). Finally, the original synthesis of a ferrocenyl rhodium(III) complex and its successful use as catalyst for a C--C coupling reaction via C--H activation of 2-phenylpyridine is presented.

Preparation of New Buchwald-Type Secondary Phosphine Oxide Ligands and Applications in Suzuki−Miyaura Reactions

Two air- and moisture-stable secondary phosphine oxides (SPOs), namely, 2-(tert-butylhydrophosphoryl)-1-(2-R-phenyl)-1H-imidazole (3a, R = H; 3b, R = OMe) were prepared and characterized. A tautomeric equilibrium exists between the secondary phosphine oxide 3a (or 3b) and its corresponding phosphinous acid 3a′ (or 3b′). The reaction of phosphinous acid 3a′ (or 3b′) with Pd(COD)Cl2 (or PdBr2) yielded the corresponding monopalladium complex bis(2-(tert-butylhydrophosphoryl)-1-(2-R-phenyl)-1H-imidazole)PdX2 (5a, R = H, X = Cl; 5b, R = OMe, X = Br) in cis-form as well as dipalladium complex [(μ2-2-(tert-butylhydrophosphoryl)-1-(2-R-phenyl)-1H-imidazole-N,P)Pd(I)X]2 (6a, R = H, X = Cl; 6b, R = OMe, X = Br). The phosphinous acids 3a′ and 3b′ act as P,N-chelating ligands in the formation of 6a and 6b, which feature direct Pd(I)−Pd(I) bonds. Good to excellent reactivities were observed by applying these ligand-chelated palladium complexes in Suzuki−Miyaura coupling reactions.

Chiral Diene as the Ligand for the Synthesis of Axially Chiral Compounds via Palladium-Catalyzed Suzuki−Miyaura Coupling Reaction

The first palladium-diene-catalyzed asymmetric Suzuki-Miyaura coupling reaction has been achieved. A number of functionalized biaryls were obtained in high yields and in moderate to high enantioselectivities. The existence of an ortho-formyl group greatly improves the catalyst efficiency and permits further synthetic elaborations.

Abnormal N-Heterocyclic Carbene Promoted Suzuki−Miyaura Coupling Reaction: A Comparative Study

A C2-protected imidazolium salt that generates an abnormal N-heterocyclic carbene (NHC) was applied for the palladium-catalyzed Suzuki−Miyaura coupling reactions. The abnormal NHC precursor promoted the reactions while suppressing homocoupling of aryl boronic acid, which was observed with the corresponding normal NHC precursor. The related well-defined abnormal NHC-based palladium complexes also showed better activity than the normal NHC-based analogues, exhibiting faster reaction rates especially at the initial stage of the reaction.

Glucopyranoside-Incorporated N-Heterocyclic Carbene Complexes of Silver(I) and Palladium(II): Efficient Water-Soluble Suzuki−Miyaura Coupling Palladium(II) Catalysts

Glucopyranoside-incorporated silver(I) bis(carbene) complexes have been prepared through the reactions of silver oxide with related imidazolium salts. The palladium(II) bis(carbene) complexes were synthesized from their corresponding silver(I) complexes via the technique of transmetalation. In solution, both trans-anti and trans-syn rotamers are observed for these square-planar Pd(II) complexes. In the solid state, the complex [1-methyl-3-(methyl 2,3,4-tri-O-benzoyl-6-deoxy-α-d-glucopyrano-6-yl)imidazol-2-ylidene]2PdBr2 adopts a trans-anti conformation, while the complexes [1-ethyl-3-(methyl 2,3,4-tri-O-benzoyl-6-deoxy-α-d-glucopyrano-6-yl)imidazol-2-ylidene]2PdBr2 and [1-n-butyl-3-(methyl 2,3,4-tri-O-benzoyl-6-deoxy-α-d-glucopyrano-6-yl)imidazol-2-ylidene]2PdBr2 adopt a trans-syn conformation. The steric congestion between the two glucopyranoside groups in the last two trans-syn compounds are perhaps relaxed through tilting of the imidazole rings and rotation of the flexible CH2 spacer, which connects the imidazole ring and the glucopyranoside group. The palladium(II) complexes were further hydrolyzed to produce water-soluble hydrolysates. Preliminary catalytic studies show that these hydrolyzed palladium precatalysts are efficient in the Suzuki−Miyaura coupling reaction between phenylboronic acid and a hydrophilic substrate, 2-chlorobenzoic acid, in aqua medium. In the presence of tetra-n-butylammonium bromide (TBAB), these precatalysts also display efficient catalytic properties in the reaction of phenylboronic acid with both the hydrophilic substrate 1-chloro-3-nitrobenzene and the hydrophobic substrate 2-chlorophenol. In all cases, the catalytic systems are stable, which allow them to be reused for at least three cycles. This catalytic system also facilitates the separation of products from the catalyst and, therefore, is environmentally benign.

A Novel Dewar-Like Reactor for Maintaining Constant Heat and Enhancing Product Yields during Microwave-Assisted Organic Syntheses

A novel microwave reaction vessel is herein proposed for maintaining constant heat during microwave-assisted organic syntheses. The structure of the vessel is Dewar-like in that it prevents conduction of microwave-generated heat in dielectric substrates into the surroundings. The potential of the double-walled vacuum-filled vessel has been examined for the absence of thermal gradients in aqueous media (homogeneous media) and in the synthesis of biphenyl in a nonpolar solvent (heterogeneous media) involving the Suzuki−Miyaura coupling reaction. The efficiency of the microwave-assisted organic synthesis was enhanced significantly (6- to 7-fold) with this double-walled vessel relative to the conventional single-walled reactor vessel currently used in commercial microwave chemical devices.

Palladium-Catalyzed C−F Activation of Polyfluoronitrobenzene Derivatives in Suzuki−Miyaura Coupling Reactions

Highly fluorinated nitrobenzene derivatives are suitable substrates for palladium-catalyzed C-F bond arylation using readily available palladium catalysts under both conventional heating and microwave conditions. Arylation occurs ortho to the nitro group offering a synthetic route to polyfluorinated 2-arylnitrobenzene systems. The regiochemistry of the arylation reactions suggests that there is a significant directing interaction between the nitro group and the incoming nucleophilic palladium catalyst which is facilitated by the presence of several fluorine atoms attached the ring. Investigations into the regioselectivity and reactivity of several tetrafluoro- and trifluoronitrobenzene derivatives provides further evidence for the highly nucleophilic character of the oxidative addition step in contrast to the concerted mechanism of more conventional Suzuki-Miyaura coupling reactions involving aryl iodides and bromides.

Ligand‐Free and Heterogeneous Palladium on Carbon‐Catalyzed Hetero‐Suzuki–Miyaura Cross‐Coupling

AbstractA ligand‐free and heterogeneous palladium on carbon (Pd/C)‐catalyzed hetero‐Suzuki–Miyaura coupling reaction has been developed. The protocol enables the construction of both heterocyclic‐alicyclic and heterocyclic‐heterocyclic biaryl derivatives in good to excellent yields. Furthermore, Pd/C could be reused. The time‐course study clarified that palladium was leached into the reaction media as the reaction proceeded and then completely deposited on the carbon support.

Palladium Nanoparticles on Graphite Oxide and Its Functionalized Graphene Derivatives as Highly Active Catalysts for the Suzuki−Miyaura Coupling Reaction

Pd(2+)-exchanged graphite oxide and chemically derived graphenes therefrom were employed as supports for Pd nanoparticles. The influence of catalyst preparation, carbon functionalization, and catalyst morphology on the catalytic activity in the Suzuki-Miyaura coupling reactions was investigated. The catalysts were characterized by means of spectroscopy (FT-IR, solid-state (13)C NMR, AAS, XPS), X-ray scattering (WAXS), surface area analysis (BET, methylene blue adsorption), and electron microscopy (TEM, ESEM). In contrast to the conventional Pd/C catalyst, graphite oxide and graphene-based catalysts gave much higher activities with turnover frequencies exceeding 39,000 h(-1), accompanied by very low palladium leaching (<1 ppm).

4-((2-Halogeno-5-pyridyl)dimethylsilyl)phenylboronic Acids: New Potential Building Blocks for the Synthesis of Silicon-Containing Drugs

With the synthesis of 4-((2-fluoro-5-pyridyl)dimethylsilyl)phenylboronic acid (1a) and 4-((2-chloro-5-pyridyl)dimethylsilyl)phenylboronic acid (1b), new potential building blocks for the synthesis of silicon-containing drugs have been made available. Compounds 1a,b were characterized by elemental analyses, multinuclear NMR experiments, and single-crystal X-ray diffraction studies. The synthetic potential of 1a was demonstrated by the Suzuki−Miyaura coupling reaction with 4-bromophenol to give (2-fluoro-5-pyridyl)(4′-hydroxy-(1,1′-biphenyl)-4-yl)dimethylsilane (2).

Evolution of Spherical Assemblies to Fibrous Networked Pd(II) Metallogels from a Pyridine-Based Tripodal Ligand and Their Catalytic Property

A series of metal−organic gels (MOGs) were formed in CH3OH−CHCl3 solution based on L1 and Pd(COD)(NO3)2 (L1 = 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tris(N-(pyridin-3-ylmethyl)benzamide, COD = cycloocta-1,5-diene) at different ratios. FT-IR, NMR, and fluorescence spectroscopy show that hydrogen bonding, π−π interaction, and coordination bonding are involved in the gel formation. The morphologies of these metallogels are Pd/L1 ratio dependent ranging from spheres to fibers. The fibrous networked gel shows higher catalytic activity in Suzuki−Miyaura coupling reaction than the spherical gel, acting as recyclable Pd(II) catalyst supported by the air-stable networked gel/xerogel.

Optimization and Scale-Up of a Suzuki−Miyaura Coupling Reaction: Development of an Efficient Palladium Removal Technique

A ligand−solvent−base screen was performed on a Suzuki−Miyaura coupling reaction, and the screening data, followed by a set of focused experiments, helped to optimize reaction conditions. Further work was carried out that centered on reducing the level of residual palladium in the isolated product. Treatment of the reaction mixture with toluene and 20% aqueous NaHSO3 at elevated temperature lowered the palladium content from ∼8000 ppm to 100 ppm or less. The Suzuki−Miyaura coupling and palladium removal process were demonstrated on 20-L scale, are highly efficient and cost-effective, and require short cycle times.

Cyclometalated cis-Chelated Bidentate N-Heterocyclic Carbene Palladium Complexes: Synthetic, Structural, and Catalytic Studies

Novel cyclometalated cis-chelated bidentate N-heterocyclic carbene palladium complexes derived from binaphthyl-2,2′-diamine (BINAM) have been successfully synthesized, and the cyclometalated cis-chelated bidentate NHC−palladium(II) complex 5a has been characterized by X-ray crystal structure diffraction. Moreover, we found that these novel NHC−palladium(II) complexes are quite effective in Suzuki−Miyaura coupling reactions and Friedel−Crafts reactions under mild conditions.

Functionalized Mesostructured Silicates as Supports for Palladium Complexes: Synthesis and Catalytic Activity for the Suzuki−Miyaura Coupling Reaction

The synthesis and characterization of palladium-loaded functionalized mesostructured silicates, designated as Pd-SHSBA-16 and Pd-SHKIT-6, are described. These solids were tested as heterogeneous catalysts for the Suzuki−Miyaura reaction. The materials were characterized by 29Si NMR, 13C NMR, nitrogen adsorption isotherms (BET-DFT), TEM, SEM, XRD, EDS, and ICPMS analysis. Pd(0) or Pd(II) complexes supported on the surface of functionalized mesostructured silica both displayed high activity for this important reaction.