Cross-coupling Reaction Of Aryl Halides Research Articles

Nickel-Catalyzed Cross-Coupling Reaction of Aryl Bromides/Nitriles with Imidazolium Salts Involving Inert C-N Bond Cleavage.

We herein present a nickel-catalyzed cross-coupling reaction of aryl halides and nitriles with imidazolium salts. A series of 2-arylated imidazoles could be obtained in moderate to good yields through inert C-N bond cleavage. The imidazolium salt in this reaction acts as both a coupling partner and N-heterocyclic carbene (NHC) ligand precursor. Mechanistic studies reveal that consecutive steps of migratory insertion of the NHC into the aryl C-Ni bond and β-C elimination might be involved in the proposed reaction mechanism.

Synthesis of amide functionlized bidentate NHC-Pd complex for application as catalyst in Suzuki‐Miyaura cross-coupling, in distilled water, under mild reaction conditions

An amide functionlized bidentate NHC-Pd complex was successfully prepared by a facile solvothermal methodology from a bridged bis-benzimidazolium chloride and K2PdCl4. The new bidentate NHC-Pd complex has been effectively applied as catalyst in Suzuki-Miyaura cross-coupling reactions of aryl halides with arylboronic acids in distilled water (yields up to 99.0%). The bridged bis-benzimidazolium ligand from the Pd complex, bearing the amide functional groups on the nitrogen atom, showed to distinctly influence the electronic and steric effects on the catalytic process. The potential of application of the new NHC-Pd catalyst in diverse CC bond forming processes, working under environmentally friendly conditions, is further outlined.

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.

A new air-stable Pd-PEPPSI N-heterocyclic carbene complex: Synthesis, structure, computational and catalytical studies

In this work, we have synthesized a new, air and moisture stable, Pd-PEPPSI (pyridine enhanced pre-catalyst preparation, stabilization and initiation) complex, [PdBr2(NHC)Py] (NHC is 3-benzyl-1-(4-methoxyphenyl)-1H-imidazolline-2-ylidiene) and successfully employed as catalyst under mild conditions (35 °C, 0.5 mol% Pd loading) Suzuki-Miyaura cross-coupling reactions of aryl halides with aryl boronic acids in aqueous isopropanol. A wide range of aryl bromides / iodides were effectively utilized as coupling partners with arylboronic acids to afford corresponding biaryls in moderate-to-excellent yields. The complex was characterized by ESI-MS, 1H and 13C NMR spectroscopy and the molecular structure was determined by X-ray single crystal analysis. In order to gain more insight about structure, bonding and electronic properties, density functional theory (DFT) studies were performed. Moreover, TDDFT calculations were also performed to interpret the observed electronic absorption bands in the UV-VIS spectra. A good agreement between experimental and theoretical data was observed.

Development of Photoredox Cross-Electrophile Coupling of Strained Heterocycles with Aryl Bromides Using High-Throughput Experimentation for Library Construction.

Microscale high-throughput experimentation was used to develop a photoredox-assisted reductive cross-coupling reaction of aryl halides with strained aliphatic heterocycles facilitated via a ring-opening reaction. This methodology was found to be applicable to medicinally relevant substrates including Boc-protected strained aliphatic heterocycles and (hetero)aryl bromides and was used for compound library construction via parallel medicinal chemistry. Furthermore, the coupling reactions were shown to be scalable to the gram scale by continuous flow reaction. A possible reaction mechanism is also discussed.

Catalysis of a Bis-Caffeine Palladium(II) NHC-Pincer Complex

A tridentate bis-NHC Pd complex, based on caffeine, was studied for its catalytic activity. This complex displayed a high catalytic activity in the Suzuki–Miyaura and Mizoroki–Heck cross-coupling reactions of aryl halides. The Sonogashira cross-coupling was also investigated but reveals a fast plateauing of the reaction. Aryl iodides as well as aryl bromides react when equipped with either electron-donating or electron-withdrawing substituents. Aryl chlorides, which contained electron-withdrawing groups, were also reactive under the applied conditions.

Gold Catalysis: A New Contender for Cross-Coupling Reactions with Aryl Halides

Cross-coupling reactions of aryl halides catalyzed by transition metals such as Pd, Ni, Cu etc have shown to be effective tools for the generation of carbon–carbon and carbon–heteroatom bonds. However, because of the difficulties associated with the oxidative addition of organohalides or pseudohalides on gold complexes, such cross- coupling reactions are non-trivial in gold catalysis. Recent research revealed that gold- catalyzed cross-coupling reactions of aryl iodides are possible and the current article shall briefly discuss the state-of-the-art in the field.

Polyaniline-encapsulating CuFe2O4/Cu2O composite: a simple, effective and reusable heterogeneous catalyst for ligand-free N-arylation of amines and nitrogen heterocycles

Cu2O supported on polyaniline (PANI) encapsulating CuFe2O4 was found to be highly efficient, magnetically separable and recyclable heterogeneous catalyst for the C-N cross-coupling reaction of arylhalides with amines. It was successfully synthesized and characterized using FT-IR, VSM, TGA, TEM, SEM, EDX, and XRD. The applicability of PANI/nano-CuFe2O4/Cu2O catalyst was considered in the C-N cross-coupling reaction of aryl halides with alkyl and aryl amines in good yields without using external ligands or additives as promoters. Notably, the PANI/nano-CuFe2O4/Cu2O catalyst was separated from the reaction by using an external magnet and recycled for seven runs without significant loss of catalytic activity.

The Mizoroki-Heck reaction between in situ generated alkenes and aryl halides: cross-coupling route to substituted olefins.

This review covers palladium-catalyzed typical Mizoroki-Heck cross-coupling reactions of aryl halides with in situ generated alkenes, by following a typical Heck coupling mechanism to form substituted olefins unlike direct cross-coupling of alkenes with aryl halides in Heck olefination. These reactions solve the issue of alkenes undergoing polymerization at high temperatures and increase reaction efficiency by reducing the reaction time and purification steps.

Shining Visible Light on Reductive Elimination: Acridine-Pd-Catalyzed Cross-Coupling of Aryl Halides with Carboxylic Acids.

Despite the recent tremendous progress on transition-metal/photoredox dual catalysis in organic synthesis, single transition-metal catalysis under visible-light irradiation, which can utilize light energy more efficiently, is still underdeveloped. Herein, we report the design of photosensitizing phosphinoacridine bidentate ligands for visible-light-induced transition-metal catalysis, expecting that the electron-accepting acridine moiety would create a highly reactive electron-deficient metal center toward reductive elimination via metal-to-ligand charge transfer (MLCT). Using these ligands, we have achieved a palladium-catalyzed cross-coupling reaction of aryl halides with carboxylic acids under visible-light irradiation. Electronic tuning of the phosphinoacridine ligands not only enabled the use of a variety of aryl halides as the coupling partner, including less reactive aryl chlorides, under blue light irradiation, but also realized the employment of lower-energy green and red light for the cross-coupling. Experimental mechanistic studies have proved that the reductive elimination of aryl esters is induced by photoirradiation of phosphinoacridine-ligated arylpalladium(II) carboxylate complexes. The theoretical calculation suggests that the reductive elimination in the excited state is promoted by decreasing the electron density of the Pd center through photoinduced intramolecular electron transfer, i.e., MLCT, in the transition state owing to the electron-deficient acridine scaffold. This is a very rare example of photoinduced reductive elimination on palladium(II) complexes.

Conversion of monodentate benzoylthiourea palladium(II) complex to bidentate coordination mode: Synthesis, crystal structure and catalytic activity in the Suzuki-Miyaura cross-coupling reaction

Trans-dichloro bis[N,N-dibutyl-N'-(4-chloro-benzoyl)thioureato-κS]palladium(II) complex (Trans-[PdIICl2(HBTU-κS)2]) is formed by reaction between PdCl2 and N,N-dibutyl-N'-(4-chlorobenzoyl)thiourea (BTU) in acetonitrile. Cis-bis[N,N-dibutyl-N'-(4-chlorobenzoyl) thioureato-κ2O,S]palladium(II) (cis-[PdII(BTU-κ2S,O)2]) is obtained by recrystallization of trans-[PdIICl2(HBTU-κS)2] in ethanol:dichloromethane solvent mixture. The prepared ligand coordinates with Pd(II) ion in monodentate coordination mode for trans-[PdIICl2(HBTU-κS)2] and in bidentate coordination mode for cis-[PdII(BTU-κ2S,O)2]. Both Pd(II) complexes have been characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR, and UV-Vis techniques. The detail structural formulations of trans-[PdIICl2(HBTU-κS)2] and cis-[PdII(BTU-κ2S,O)2] have been defined by X-ray single-crystal diffraction. The palladium complexes were also applied as an efficient catalyst for the Suzuki-Miyaura cross-coupling reaction of aryl halides with aryl boronic acids at 110°C using a very high substrate/catalyst ratio.

Copper-mediated etherification via aryl radicals generated from triplet states

Carbon–heteroatom (C–X) cross-coupling is a common method for bond-forming reactions in chemistry but the more electronegative the heteroatom X is, the more challenging the bond formation becomes. Although reductive elimination from Cu(III) intermediates to form C–X bonds is generally a facile reaction, oxidative addition of Cu(I) into the carbon–(pseudo)halide bond of aryl (pseudo)halides is energetically challenging. Therefore, cross-coupling reactions of aryl halides with a variety of nucleophiles is currently out of reach for methods based on copper. Here we present a strategy to bypass the high-barrier oxidative addition step to aryl halides by the generation of aryl radicals from triplet states. Photoinduced energy transfer to, or direct excitation of, aryl halides even enables the use of aryl chlorides as electrophilic coupling partners. This strategy allows for the use of alcohols, amines and fluoride as nucleophiles and expands the scope of copper-mediated cross-coupling chemistry.

Potassium Trimethylsilanolate-Promoted, Anhydrous Suzuki-Miyaura Cross-Coupling Reaction Proceeds via the "Boronate Mechanism": Evidence for the Alternative Fork in the Trail.

Previous studies have shown that the critical transmetalation step in the Suzuki-Miyaura cross-coupling proceeds through a mechanism wherein an arylpalladium hydroxide complex reacts with an aryl boronic acid, termed the oxo-palladium pathway. Moreover, these same studies have established that the reaction between an aryl boronate and an arylpalladium halide complex (the boronate pathway) is prohibitively slow. Herein, studies on isolated intermediates, along with kinetic analysis, have demonstrated that the Suzuki-Miyaura reaction promoted by potassium trimethylsilanolate (TMSOK) proceeds through the boronate pathway, in contrast with other, established systems. Furthermore, an unprecedented, binuclear palladium(I) complex containing a μ-phenyl bridging ligand was characterized by NMR spectroscopy, mass spectrometry, and computational methods. Density functional theory (DFT) calculations suggest that the binuclear complex exhibits an open-shell ground electronic state, and reaction kinetics implicate the complex in the catalytic cycle. These results expand the breadth of potential mechanisms by which the Suzuki-Miyaura reaction can occur, and the novel binuclear palladium complex discovered has broad implications for palladium-mediated cross-coupling reactions of aryl halides.

Synthesis and characterization of palladium nanoparticles immobilized on graphene oxide functionalized with triethylenetetramine or 2,6-diaminopyridine and application for the Suzuki cross-coupling reaction

Graphene oxide (GO) was functionalized with two organic ligands, triethylenetetramine (TETA) or 2,6-diaminopyridine (DAP), followed by palladium nanoparticles (Pd NPs) for the synthesis of Pd NPs/GO-TETA and Pd NPs/GO-DAP nanocomposites, respectively. The two heterogeneous nanocomposites were fully characterized and their efficiency was investigated for CC bond formation for the synthesis of biaryl compounds via the Suzuki cross-coupling reaction of aryl halides with arylboronic acid derivatives. The obtained results indicated that the Pd NPs/GO-TETA nanocomposite was more effective in the Suzuki coupling reaction as compared to Pd NPs/GO-DAP. Thus, the Suzuki cross-coupling reaction of different aryl halides with arylboronic acid derivatives using Pd NPs/GO-TETA nanocomposite catalyst in the presence of Na2CO3 as base in DMF/H2O (1/1) as solvent at 90 °C was carried out to afford the desired biaryl compounds in high to excellent yields (81–100%) and short reaction times (10–90 min). Additionally, Pd NPs/GO-TETA nanocomposite can be recovered and reused for 8 consecutive runs without any apparent loss of its catalytic activity, proving its high stability and potential use in organic transformations.

Introduction of PdCl2 supported on tartaric acid modified magnetite nanoparticles (Fe3O4@TA-Pd) as a novel catalytic system in Suzuki–Miyaura coupling reaction

In this paper, a new magnetically separable catalytic system based on Palladum (Pd) encapsulated with tartaric acid (TA) as a linker (Fe3O4@TA-Pd) is introduced in which TA as a hydroxy organic acid grafted onto the Fe3O4 nanoparticles (Fe3O4 NPs) readily forms complexes with Pd2+. To assess the catalytic capability of the prepared catalyst bearing Pd chelated with TA, it was exploited for achieving some biaryl compounds through Suzuki–Miyaura cross-coupling reaction of aryl halides with phenylboronic acid (PhB(OH)2). This catalyst was reused up to 7 runs with minimizing the change in its activity. Convenient preparation, easy separation and recoverability of this catalyst, facile and efficient transformation to biaryl products along with relatively excellent yields are of the superiorities of this catalyst.

Pd(OAc)2-biuret: A highly efficient, low cost and phosphine-free catalyst system for biaryl synthesis under aerobic conditions at room temperature

A highly efficient, less expensive and phosphine-free protocol for the Suzuki-Miyaura cross-coupling reactions of aryl halides and aryl boronic acids in iPrOH-H2O solvent under aerobic conditions has been developed. The results demonstrate that the biuret played a crucial role and making this protocol highly efficient. The Pd(OAc)2-biuret system exhibited superb catalytic activity towards the Suzuki-Miyaura cross-coupling reaction of a wide range of aryl halides with aryl boronic acids at room temperature, giving high yields even under very low catalytic loading. This system offers an attractive alternative to the existing protocols since the reaction proceeds in green solvent at room temperature with working simplicity, shorter reaction time, cost-effectiveness and provides the desired products in high yields. The effect of solvent, base as well as catalyst loading on the cross-coupling reaction of aryl halide with arylboronic acid is also described.

N-heterocyclic carbene Pd(II) complex supported on Fe3O4@SiO2: Highly active, reusable and magnetically separable catalyst for Suzuki-Miyaura cross-coupling reactions in aqueous media

A new type magnetic nano Fe3O4@SiO2@NHC@Pd-MNPs heterogeneous catalyst was fabricated and characterized by Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Energy Disperse X-ray analysis (EDX), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Scanning Electron Microscopy (SEM). The loading amount of Palladium (Pd) to magnetic nano Fe3O4@SiO2@NHC@Pd-MNPs was measured by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analysis. The catalytic activity of magnetic nano Fe3O4@SiO2@NHC@Pd-MNPs heterogeneous catalyst was examined on Suzuki-Miyaura cross-coupling reactions of aryl halides with different substituted arylboronic acid derivatives. All coupling reactions yielded excellent results and high TOF (up to 76528 h−1) in the presence of 2 mg of Fe3O4@SiO2@NHC@Pd-MNPs catalyst (0.0197 mmolg−1, 0.00394 mmol%Pd) at 80 °C in 2-propanol/H2O (1:2). In addition, the magnetic nano Fe3O4@SiO2@NHC@Pd-MNPs catalyst was easily recovered by using an external Nd-magnet and reused for the Suzuki cross-coupling reactions. The catalyst showed strong structural and chemical stability and was reused six times without losing its catalytic activity substantially.

Fe-MIL-101 modified by isatin-Schiff-base-Co: a heterogeneous catalyst for C–C, C–O, C–N, and C–P cross coupling reactions

Fe-MIL-101-isatin-Schiff-base-Co was synthesized and applied as a catalyst for Ullmann-type, Buchwald–Hartwig, Hirao, Hiyama and Mizoroki–Heck cross-coupling reactions of aryl halides.

Chiral Mn(III) Salen Complex Immobilized on CuFe2O4@SiO2-NH2 NPs: A Cheap and Efficient Catalyst for N-arylation of Aryl Halides and Phenylboronic Acid Under Mild Conditions

A convenient and efficient chiral CuFe2O4@SiO2-Mn(III) Ch.salen nanocatalyst has been developed for the C-N cross-coupling reactions of aryl halides/ phenylboronic acid with N-heterocyclic compounds in water and/or DMSO under mild conditions. The catalyst could be applied for the N-arylation of a variety of nitrogen-containing heterocycles with aryl chlorides, bromides, iodides and phenylboronic acid under mild conditions. Moderate to good yields were achieved for all substrates. The structure of catalyst was characterized using various techniques including FT-IR, FE-SEM, EDX, XRD, TEM and TGA. The catalyst can be simply recovered and reused for several times without significant loss of activity.

Phosphine-Built-in Porous Organic Cage for Stabilization and Boosting the Catalytic Performance of Palladium Nanoparticles in Cross-Coupling of Aryl Halides.

Herein, we report first a novel phosphine-containing porous organic cage (PPOC) from a [2 + 3] self-assembly of triphenyl phosphine-based trialdehyde and (S,S)-1,2-diaminocyclohexane via dynamic imine chemistry, which was employed as a porous material for the controlled growth of palladium nanoparticles (NPs) due to the strong affinity of Pd to the phosphine ligand based on the principle of hard and soft acids and bases. Comprehensive characterizations including X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, NMR, and X-ray absorption spectroscopy reveal that ultrafine Pd NPs with narrow size distribution (1.7 ± 0.3 nm) and enhanced surface electronic density via a strong interaction between NPs and phosphine were homogeneously dispersed in the PPOC. The resultant catalyst Pd@PPOC exhibits remarkably superior catalytic activities for various cross-coupling reactions of aryl halides, for example, Sonogashira, Suzuki, Heck, and carbonylation. The catalytic activity of Pd@PPOC outperforms the state-of-the-art Pd complexes and other Pd NPs supported on N-containing porous cages under identical conditions, owing to the enhanced surface electronic density of Pd NPs and their high stability and dispersibility in solution. More importantly, Pd@PPOC is highly stable and easily recycled and reused without loss of their catalytic activity. This work provides a new functional POC with extended potentials in catalysis and material science.