Coupling Reactions Of Aryl Halides Research Articles

Chitosan modified Ti-PILC supported PdOx catalysts for coupling reactions of aryl halides with terminal alkynes

Biopolymer of chitosan (CS) and titanium pillared clays (Ti-PILCs) have been combined in a hybrid as advanced supports for immobilization of PdOx=0,1 species to prepare novel PdOx=0,1@Ti-PILC/CS nano-composite catalysts. The Ti-PILC materials showed high specific surface areas and abundant meso-porous structure with many irregular pore channels caused by collapses of layered structure of clay during Ti pillaring process. Both CS chains and sub-nano sized PdOx particles were successfully incorporated into the pore channels of Ti-PILC, resulting in a decrease in both the specific surface areas and uniform distribution of pore size. Besides conventional methods characterizations, the strong interactions between PdOx species and Ti-PILC/CS support were further evidenced with positron annihilation lifetime spectroscopy studies. The resultant PdOx@Ti-PILC/CS catalyst was highly active for the coupling reactions of aryl halides with phenyl acetylenes. It was recyclable and gave excellent yield up to 13 runs with low leaching of Pd species.

Efficient Pyrazole Moiety‐Containing Ligands for Cu‐Catalyzed O‐Arylation of Phenols

AbstractSeven pyrazole‐ or pyridine‐containing N2‐ and N3‐ligalitnds (L1–L7) were developed for the ligand‐assisted CuI‐catalyzed coupling reactions of aryl halides with phenols. The structural and electronic effects were studied for various combinations of pyridine and/or imine nitrogen binding sites in the ligands. Screening their abilities showed most of them to be better than 4,4’‐dimethoxybipyridine (L8). Among them, 2‐(1‐pyrazolyl)pyridine (L1) featuring two types of binding sites gave the best results, with yields of up to 95% at 100 °C at a catalyst loading of 10 mol% (CuI/L in 1 : 1 ratio). Free radical scavengers, 2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) (1.0 eq.) and cumene (1.0 eq.), lowered the yields by more than half, but the reaction was not completely quenched even when 3.0 eq. of TEMPO was used. A non‐radical and a radical mechanisms, are proposed for the L1‐promoted coupling reaction, well explained the experiments results. In addition, the structure of the catalyst species were elucidated through single crystal XRD and DFT (density functional theory) calculations.

A Bio‐Inspired Magnetically Recoverable Palladium Nanocatalyst for the Ullmann Coupling reaction of Aryl halides and Arylboronic acids In Aqueous Media

AbstractPalladium nanoparticles supported on polydopamine‐coated iron oxide nanoparticles (Pd/Fe3O4@PDA) were found to catalyze the Ullmann homocoupling of a wide variety of aryl halides, arylboronic acids and aryldiazonium salts in aqueous media in the presence of randomly methylated β‐cyclodextrin (RM‐β‐CD). The synthesized nanoparticles were characterized by techniques such as TEM, SEM, EDX, XPS, ICP‐AES and XRD. The synthesized catalyst can be easily recovered magnetically and reused up to five cycles without any significant loss of activity. This is the first report demonstrating the use of magnetically recoverable catalyst for Ullmann homocoupling reactions of aryl halides, arylboronic acids and aryldiazonium salts in water.

Copper nanoparticles supported on 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41: An efficient and recyclable catalyst for one‐pot three‐component C–S coupling reaction of aryl halides with benzyl bromide and thiourea

An environmentally friendly copper‐based catalyst supported on 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41 was prepared and characterized by Fourier transform‐infrared, transmission electron microscopy, field emission‐scanning electron microscopy, X‐ray diffraction and inductively coupled plasma techniques. The catalyst was applied for the one‐pot three‐component C–S coupling reactions of aryl halides with benzyl bromide and thiourea under aerobic conditions to afford the corresponding coupled products in good yields in water. The catalyst could be recovered and recycled five times. These results prove 2‐methoxy‐1‐phenylethanone‐functionalized MCM‐41 supported Cu (II) complex was not leached during the reaction. Also it shows the correct heterogeneous nature of the catalyst.

Synthesis of novel and room temperature-operable palladium complexes on graphene oxide: An efficient recyclable catalyst for Suzuki-Miyaura coupling reactions

Novel palladium complexes composed of palladium and a conjugated ligand (imine–aldehyde) were immobilized on graphene oxide. The developed catalyst was characterized by XPS, and TEM. The novel catalyst was proven to be highly efficient for the Suzuki-Miyaura coupling reaction of aryl halides (Br, Cl) with arylboronic acids under mild conditions with a low amount of catalyst (0.1 mol%). In particular, excellent yields could be also obtained at room temperature within 1 h for monosubstituted aryl bromide coupling. Furthermore, the novel catalyst could be reused at least ten times without significant loss of its catalytic activities.

Palladium nanoparticles immobilized on the magnetic few layer graphene support as a highly efficient catalyst for ligand free Suzuki cross coupling and homo coupling reactions

In this study, we prepared a magnetic metal–graphene nanocomposite for the synthesis of substituted biaryls via Suzuki cross coupling and homo coupling reaction of aryl halides. The magnetic few layer graphene composite was synthesized by using one-step electrochemical exfoliation of graphite foil in aqueous iron (II) ammonium sulfate as electrolyte without using of any additive or corrosive media. Then, Fe2O3@FLG composite was used an efficient support for the immobilization and suitable dispersing of palladium nanoparticles. The obtained Fe2O3@FLG@Pd0 nanocomposite was characterized using FT-IR, SEM, TEM, EDS, XRD, VSM and ICP-AES analysis. Very low loading of this catalyst was displayed high activity in the producing substituted biaryls. It simply recovered from the reaction mixture and reused without any pre-activation in six consecutive runs with no loss of its catalytic activity or the observation of any detectable palladium leaching process.

PdAu alloy nanoparticles supported on nitrogen-doped carbon black as highly active catalysts for Ullmann coupling and nitrophenol hydrogenation reactions.

Noble metal-based catalysts have been proven to be active for catalytic organic reactions. The selectivity and conversion can be improved by integration with proper carrier materials, and further modulated by tuning the composition as well as the electronic structure of the active noble metals. Compared with unsupported monometallic catalysts, the synergistic interactions between neighboring metals and the combined effects between the carrier materials and the active components often give rise to positive influences on the enhancement of the catalytic efficiency and selectivity. In this work, we report a facile process for the fabrication of nitrogen-doped carbon black (NCB) supported PdAu bimetallic nanoparticles (NPs) with a uniform dispersion and narrow size distribution. The PdAu/NCB catalyst with a Pd/Au mole ratio of 1/1 shows the highest activity towards both Ullmann coupling reactions of aryl halides and the hydrogenation reaction of nitrophenols. Moreover, this bimetallic catalyst also exhibits a superior recycling durability to that of monometallic Pd/NCB and Au/NCB catalysts. The enhanced catalytic performance of the bimetallic catalyst is mainly due to the large BET specific surface area (125.45 m2 g−1) and the synergy between the individual components of the catalyst.

Dimethylformamide-stabilised palladium nanoclusters catalysed coupling reactions of aryl halides with hydrosilanes/disilanes.

N,N-Dimethylformamide-stabilised Pd nanocluster (NC) catalysed cross-coupling reactions of hydrosilane/disilane have been investigated. In this reaction, the coupling reaction proceeds without ligands with low catalyst loading. N,N-Dimethylacetamide is a crucial solvent in these reactions. The solvent effect was considered by various techniques, such as transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The Pd NCs can be recycled five times under both hydrosilane and disilane reaction conditions.

Practical heterogeneous photoredox/nickel dual catalysis for C-N and C-O coupling reactions.

Efficient C-N and C-O coupling reactions of aryl halides with amines and alcohols have been developed by using the strategy of heterogeneous visible light photoredox and nickel dual catalysis. Obviously, the joint use of inexpensive and bench-stable CdS and nickel salts, together with mild reaction conditions, makes these two transformations attractive for the synthetic community. This heterogeneous dual catalysis system also proved to be successful in the ligand-free catalytic hydroxylation of aryl bromide with water as a nucleophile. The practicality of this protocol is further emphasized by the scaled-up reaction and the reusability of heterogeneous photocatalysts.

Design of BNPs-TAPC Palladium Complex as a Reusable Heterogeneous Nanocatalyst for the O-Arylation of Phenols and N-Arylation of Amines

The thermally stable new heterogenous nanocatalyst BNPs@SiO2(CH2)3-TAPC-O-CH2CH2NH2-Pd(0) was synthesized, characterized and successfully applied in carbon-heteroatom (C–O and C–N) coupling reactions of aryl halides with phenols and amines. The formation of resultant nanocatalyst was approved by FT-IR, XRD, TGA, XPS and EDX techniques. The morphology of BNPs@SiO2(CH2)3-TAPC-O-CH2CH2NH2-Pd(0) was characterized using scanning and transmission electron microscopes. The leaching of palladium from the surface of the catalyst was studid by ICP-OES technique. Noteworthy, the highly active BNPs@SiO2(CH2)3-TAPC-O-CH2CH2NH2-Pd(0) can be easily recycled and reused for six times with negligible loss in its activity. Some remarkable advantages of this method are the shorter reaction times, milder conditions, no needs for an inert atmosphere, high yields and easy separation.

Copper‐Catalyzed Coupling Reactions of Aryl Halides and Phenols by 4,4’‐Dimethoxy‐2,2’‐bipyridine and 4,7‐Dimethoxy‐1,10‐phenanthroline

AbstractSeveral Cu(I) complexes of 2,2’‐bipyridines were studied for the catalytic coupling of aryl iodides and phenols and 4,4’‐dimethoxy‐2,2’‐bipyridine was shown to be an effective ligand of CuI in 1:2 (CuI:ligand) ratio for the synthesis of a wide range of diaryl ethers (up to 97% yield) using K3PO4 as base in DMF at 100 °C. The catalysis was highly dependent on the reaction temperature and was successfully applied in the coupling with more attractive and challenging substrates, aryl bromides, at 140 °C in good‐to‐excellent yields (78−95%). Moreover, the heteroaromatic effect for the reaction was studied and gave a comparable result with phenyl group (up to 95% yield). Significantly, a structurally related N,N‐bidentate ligand, 4,7‐dimethoxy‐1,10‐phenanthroline, exhibited better performance for less‐reactive combinations of aryl halides and phenols.

Magnetically retrievable N-heterocyclic carbene-silver complex with wingtip ferrocenyl group for Sonogashira coupling

A new magnetically retrievable N-heterocyclic carbene-silver complex with wingtip ferrocenyl group has been prepared by multi-step procedure. The formation of complex was confirmed on the basis of analytical techniques such as FT-IR, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD), transmission electron microscopy (TEM) and VSM (vibrating sample magnetometer) analysis. The complex was successfully employed as an efficient heterogeneous catalyst for Sonogashira coupling reaction of aryl halides with terminal alkynes. The complex could be separated easily by applying external magnet. The reusability studies revealed that complex can be reused up to eight times without significant decrease in catalytic activity.

Synthesis of chiral α-amino anilides via a DMEDA-promoted selective C─N coupling reaction of aryl halides and α-aminoamides

A DMEDA-promoted and copper-catalyzed approach has been designed for the coupling of aryl halides and chiral α-aminoamides to afford a range of functionalized chiral α-amino anilides. This method has a higher yield and better reproducibility than those under ligand-free conditions. Of the two amino groups in the same molecule, only the amide NH2 is observed to react, showing high regioselectivity. In addition, no racemization occurs, and the ee can reach 99%. For certain hydroxyl-containing substrates, such as l-tyrosine amide and l-threonine amide, addition of a phase transfer catalyst (15-Crown-5) is necessary for such a transformation.

Facile Synthesis of Magnetic Hierarchical Core–Shell Structured Fe3O4@PDA‐Pd@MOF Nanocomposites: Highly Integrated Multifunctional Catalysts

AbstractA magnetic hierarchical core–shell structured Fe3O4@PDA‐Pd@[Cu3(btc)2] nanocomposite has been fabricated via a facile layer‐by‐layer assembly method. It contains a core of polydopamine (PDA)‐modified magnetic Fe3O4 nanoparticles (NPs), a transition layer of Pd NPs, and a porous outer shell of copper‐based metal–organic framework (MOF) with controllable thickness. This novel nanocomposite was characterized by TEM, FTIR, XRD, XPS, N2 adsorption–desorption isotherms, and VSM. The prepared Fe3O4@PDA‐Pd@[Cu3(btc)2] (n=5) nanocomposite shows ultrahigh catalytic activity for the 4‐nitrophenol reduction and Suzuki–Miyaura coupling reactions of aryl halides (Br, Cl) with arylboronic acids. Moreover, the nanocomposite also can be easily separated by an external magnet and reused at least 8 runs with excellent yields for both the reactions. The catalyst has outstanding catalytic performance, mainly because the integration of [Cu3(btc)2] with Fe3O4@PDA‐Pd that combines the advantages of each component could exhibit a synergistic effect in the catalytic system.

Preparation of cobalt substituted zinc aluminium chromite: photocatalytic properties and Suzuki cross coupling reaction

A series of cobalt substituted zinc aluminium chromite nanoparticles were synthesized by simple, cost effective sol–gel auto-combustion method. The synthesized samples were characterized by different sophisticated techniques. The thermal properties of chromite nanoparticles were evaluated using thermogravimetric analysis and differential thermal analysis. X-ray diffraction analysis reveals the formation of single cubic spinel phase with an average crystallite size 25 nm. Morphological studies were carried out by scanning electron microscopy and transmission electron microscopy. The chemical compositions of chromites have been examined by energy dispersive spectroscopy and X-ray photoelectron spectroscopy technique which reveals the purity of the prepared samples. The photocatalytic performance of the synthesized material was studied towards decomposition of aqueous Rhodamine B dye solution. We systematically investigated the effect of various parameters such as irradiation time of UV light, palladium doping and kinetic parameters of photocatalysis with chromites. The catalytic performance of the samples was studied for the two-component coupling reaction of aryl halide and phenyl boronic acid. The effects of solvent, temperature, and palladium loading on the material were also discussed.

Synthesis of 4-Aryl Isoquinolinedione Derivatives by a Palladium-Catalyzed Coupling Reaction of Aryl Halides with Isoquinoline-1,3(2 H,4 H)-diones.

The palladium-catalyzed cross-coupling reaction of aryl halides with isoquinoline-1,3(2 H,4 H)-diones for the synthesis of 4-aryl isoquinoline-1,3(2 H,4 H)-diones was developed. The reaction conditions exhibit remarkable compatibility with various aryl halides and isoquinoline-1,3(2 H,4 H)-diones, and the product could be conveniently transformed to 4-aryl tetrahydroisoquinolines. (±) Dichlorofensine was synthesized using this protocol in two steps with an overall yield of 71%.

Pd-bound functionalized mesoporous silica as active catalyst for Suzuki coupling reaction: Effect of OAcˉ, PPh3 and Clˉ ligands on catalytic activity

Three new palladium catalysts, PdCat-I, PdCat-II and PdCat-III, immobilized over heterogeneous silica support have been synthesized using different ligands attached to the palladium precursor. The ligands that have been used in this study are acetate, triphenylphosphine and chloride in PdCat-I, PdCat-II and PdCat-III, respectively. The ligands have different effect on stability of the compounds and impart different oxidation states to the metal center. The materials have been characterized by powder X-ray diffraction, nitrogen adsorption-desorption studies, transmission electron microscopy, thermal analysis, and different spectroscopic techniques. The Pd-content of the samples have been determined by ICP-AES analysis. The materials have been used as catalysts for Suzuki coupling reaction of aryl halides with phenylboronic acid under mild conditions. A comparative study has been carried out to ascertain the effect of the nature of different ligands on the outcome of the catalytic reactions. Products have been identified and estimated by 1H NMR and gas chromatography. The results show that the best yields are obtained with the catalyst containing triphenylphosphine as the ligand in methanol. Such type of work to study the effect of ligand on Suzuki coupling reaction over functionalized mesoporous silica heterogeneous catalysts have not been carried out so far.

Palladium stabilized on poly and mono sulfonamide ligands as novel, simple, effective, and recyclable nano catalysts for C–C cross-coupling reactions

Poly and mono sulfonamide ligands were successfully used for the stabilization of palladium nanoparticles. The prepared nano catalysts that appeared to be heterogeneous and novel were characterized with various analytical tools. To establish the catalytic activity of the prepared catalysts, they were used in the Suzuki–Miyaura and Sonogashira–Hagihara coupling reactions of aryl halides under low palladium loading conditions. The catalysts showed good stability and could be recovered and reused for seven reaction cycles without significant loss of catalytic activity.

Straightforward and Recyclable System for Synthesis of Biaryl Ketones via Carbonylative Coupling Reactions of Aryl Halides with PhB(OH)2 and (EtO)3 PhSi

Solvent-dispersible magnetite (Fe3O4) chitosan-functionalized with methionine was effectively prepared to immobilize Pd(0) with a metal adsorption method. The catalyst was characterized by Transmission Electron Microscopy (TEM), Field emission scanning electron microscopy (FE-SEM), Powder X-ray Diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX), FT-IR spectra, thermogravimetric analyzer (TGA) and vibrating sample magnetometer (VSM). A variety of biaryl ketones were conveniently synthesized in good to high yields via carbonylative coupling of aryliodides with phenylboronic acid and PhSi(OEt)3 as phenylating reagents in the presence of Mo(CO)6 as a carbon monoxide reagent. Both electron-rich and electron-poor aryl iodides gave diaryl ketones in excellent yields and the catalytic system can be reused up to eight times.

A novel and highly efficient polyaniline‐functionalized multiwall carbon nanotube‐supported cu(I) complex for Sonogashira coupling reactions of aryl halides with phenylacetylene

A polyaniline‐functionalized multiwall carbon nanotube‐supported Cu(I) complex was developed as an efficient catalyst for the Sonogashira reactions of aryl halides with phenylacetylene in the presence of potassium hydroxide in dimethylformamide at 135 °C under nitrogen atmosphere. The corresponding products were generated in good to excellent yields using this catalytic system. Moreover, the multiwall carbon nanotube‐supported Cu(I) catalyst was simply recycled and reused for six consecutive runs.