19420-29-2

Metal coordination complexes of the sterically hindered β-diketonate, 2,6-dimesitylbenzoyl pinacolone (esac), are reported for Co, Ni, Cu, and Zn. All four form ML2-type complexes with typical coordination behavior for late-metal β-diketonates, however the effects on established electrochemistry and reactivity vary somewhat per metal. For example, the striking chemical and electrochemical inertness of CoII(esac)2 to oxidation and disproportionation is atypical. Conversely, the behavior of CuII(esac)2 is rather typical relative to other CuII(β-diketonate)2 complexes. These data suggest a relative disfavoring of certain reaction pathways, and represent an important step in modulating the catalysis of the base metals via sterically hindered β-diketonates.

The synthesis and characterization of a series of copper bis(β-diketonate) complexes, functionalized with sterically hindered o-biphenyl and m-terphenyl functional groups, are reported. X-ray structural analysis reveals that the ligands exhibit several mo

High reactivity of trimethoxyphenyl (TMP)-iodonium(III) acetate for phenol O-arylation was achieved. It was first determined that the TMP ligand and acetate anion cooperatively enhance the electrophilic reactivity toward phenol oxygen atoms. The proposed method provides access to various diaryl ethers in significantly higher yields than the previously reported techniques. Various functional groups, including aliphatic alcohol, boronic ester, and sterically hindered groups, were tolerated during O-arylation, verifying the applicability of this ligand- and counterion-assisted strategy.

Functionalized nanocellulose was prepared and employed for immobilization of phenanthroline-copper(I) complex to afford cellulose nanofibril grafted heterogeneous copper catalyst [CNF-phen-Cu(I)]. This nanocatalyst was well characterized using FT-IR, NMR, XRD, CHNS, AAS, TGA, EDX and SEM. The activities of the synthesized catalyst were examined in the synthesis of diaryl ethers via C-O cross-coupling of phenols and aryl iodides, as well as, the preparation of N-aryl amides and N-aryl heterocycles through C-N cross-coupling of amides and N-H heterocycle compounds with aryl halides. In this trend, various substrates containing electron-donating and electron-withdrawing groups were exploited to evaluate the generality of this catalytic protocol. Accordingly, the catalyst demonstrated remarkable catalytic efficiency for both C-N and C-O cross-coupling reactions, thereby resulting in good to excellent yields of the desired products. Furthermore, the recoverability experiments of the catalyst showed that it can be readily retrieved by simple filtration and successfully reused several times with negligible loss of its catalytic activity.

A novel catalytic system based on L-proline N-oxide/CuI was developed and applied to the cross-coupling reactions of various N- and O- nucleophilic reagents with aryl iodides and bromides. This strategy featured in the employment of an-proline derived dihydrazides N-oxide compound as the superior supporting ligand. By using this protocol, a variety of products, including N-arylimidazoles, N-arylpyrazoles, N-arylpyrroles, N-arylamines, and aryl ethers, were synthesized with up to 99% yield.

A quinoxaline-based porous organic polymer (Q-POP) as a mesoporous organic copolymer was developed as a new platform for the immobilization of CuNPs and copper nanocrystals. The prepared materials were characterized by FT-IR, XRD, N2 adsorption-desorption isotherms, ICP, TGA, SEM, HR-TEM, EDX, and single-crystal X-ray crystallography. The obtained catalyst presented extraordinary catalytic activity towards Ullmann C–O coupling reactions with high surface area, hierarchical porosity, and excellent thermal and chemical stability. Due to its high porosity, and synergistic effect of copper nanocrystals incorporated in the polymer composite, the as-synthesized catalyst was successfully utilized for the Ullmann C–O coupling reaction of phenols and different aryl halides to prepare various diaryl ether derivatives. All types of aryl halides (except aryl fluorides) were screened in the Ullmann C–O coupling reaction with phenols to produce diaryl ethers in good to excellent yields (70–97 %), and it was found that aryl iodides have the best results. Besides, due to the strong interactions between CuNPs, N, and O-atoms of quinoxaline moiety existing in the polymeric framework, the copper leaching from the support was not observed. Furthermore, the catalyst was recycled and reused for five consecutive runs without significant activity loss.

Notwithstanding some progress in nickel-catalyzed etherification of alkanols and arylhalides, the ability of such a Ni-catalyzed transformation employing phenols to diaryl ethers is unsuccessful due to phenolates with much lower reduction potentials, which suppress the oxidation of nickel(II) intermediates into requisite Ni(III) species. We herein report visible-light-initiated, nickel-catalyzed O-arylation of phenols with arylhalides using t-BuNH(i-Pr) as the base and thioxanthen-9-one as the photosensitizer under visible light. This photocoupling exhibits a broad substrate scope.

The present article describes the synthesis of a new magnetic polyacrylonitrile-based Pd catalyst involving polyacrylonitrile modified via 2-aminopyridine as an efficient support to immobilize Pd nanoparticles. The simple reusability, easy separation and high stability of this Pd complex make it an excellent candidate to generate a C–O bond via Ph-X activation which is a really important subject in achieving biologically active compounds. It is worth to note access to good and high yields as well as broad substrate scope have resulted from superior reactivity of this catalyst complex. Furthermore, the structure of the magnetic polyacrylonitrile-based heterogeneous catalyst was characterized by fourier transmission infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), X-ray diffraction (XRD). Also, its thermal properties were studied by thermogravimetric analysis (TGA).

Abstract: In this paper, we report the synthesis of Fe3O4?AMCA-MIL53(Al)-NH2-CoII NPs based on the metal–organic framework structures as a magnetically separable and environmentally friendly heterogeneous nanocatalyst. The prepared nanostructured catalyst efficiently promotes the C–O cross-coupling reaction in solvent-free conditions without the need for using toxic solvents and/or expensive palladium catalyst. Graphic Abstract: [Figure not available: see fulltext.].

Guillermo Calleja and co-workers from @urjc describe URJC-1-MOF as a new heterogeneous recyclable catalyst for c-heteroatom coupling reactions. The capacity of copper-based URJC-1-MOF as a MOF catalyst in cross-coupling reactions has been evaluated, focusing on the Chan-Lam-Evans arylation-type reactions on amines and alcohols without extra additives or ligands. The extraordinary chemical and structural stability of URJC-1-MOF and its good specific surface, make this material a promising alternative to homogeneous Cu (II) catalysts for cross-coupling reactions. URJC-1-MOF showed a remarkable catalytic activity for cross-coupling C?N and C?O reactions, higher than other heterogeneous and homogeneous copper-based catalyst, such as CuO, HKUST-1, Cu?MOF-74, Cu(OAc)2 and CuSO4?5H2O. Moreover, its easy recovery by simple filtration and reusability in successive runs without any loss of activity and stability, demonstrates the potential of URJC-1-MOF as an alternative catalyst for this kind of reactions in different chemical media of industrial interest.

The invention relates to a preparation method of a diaryl ether compound. Particularly, under catalysis of chitosan supported cuprous oxide, an arylation reaction used for phenols is achieved, the corresponding diaryl ether compound is obtained, the technological condition is simple, the yield is good, operability is high, and wide functional group durability is achieved.

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. Graphical Abstract: [Figure not available: see fulltext.].

A benchtop-stable reagent for the catalytic Nicholas reaction was developed. By combining a propargyl dicobalt hexacarbonyl cluster with an ortho-alkynylbenzoate unit and a fluorous tag, introduction of a propargyl hexacarbonyl complex on various aromatic compounds having acid- or base-sensitive functional groups becomes possible by using a gold(i) catalyst. In addition, the presence of a fluorous tag facilitates convenient separation of the target products from byproducts.

Palladium nanoparticles immobilized on the magnetic nanoparticles@2-amino-N-(2-aminoethyl) benzamide (MNPs@A-N-AEB.Pd0) have been presented as an efficient, and reusable magnetically heterogeneous catalyst for the C-O coupling reaction, namely Ullmann condensation reactions in an aqueous medium. This heterogeneous catalyst shows superior reactivity for the C-O arylation of different aryl halide (chloride, bromide, and iodide) with phenol derivatives to afford the desired products in good to excellent yields within short reaction time. Moreover, the catalyst can be easily recovered and reused for seven runs without loss of catalytic activity. The catalyst was characterized by several techniques, such as FT-IR, SEM, TEM, EDS, XRD, TGA and ICP-OES.

It was found that introduction of only 0.03 mol % Ag(I) into the framework of Cu3(BTC)2 ? xH2O in maghemite anchored CuBTC activated the inert CuBTC astonishingly to exhibit unexpected high catalytic activity for C?Cl activation in coupling of chloroarenes with phenols without the use of expensive ligands. This is the first application of mixed-metal MOFs in the C?X activation. Putting reusability and activity together, a TON over 15000 was obtained which is the highest TON compared with all its precedents even better than the results by Pd catalysts.

Ether-exchange reaction of alkyl aryl ethers with alcohols and thiols via the cleavage of the C(sp2)-O bond is described. Bi(OTf)3 was found to be a most effective catalyst, and etherification of fused-aromatic ethers proceeded efficiently. Monitoring of reactions revealed conceptually new transether-ification between two different ethers, which can be regarded as single-bond metathesis under the same reaction conditions.

The copper(I)-doped zeolite CuI-USY proved to be a versatile, efficient, and recyclable catalyst for various Ullmann-type coupling reactions. Easy to prepare and cheap, this catalytic material enables the arylation and heteroarylation of diverse O-, N-, S-, and C-nucleophiles under ligand-free conditions while exhibiting large functional group compatibility. The facility of this catalyst to promote C-O bond formation was further demonstrated with the total synthesis of 3-methylobovatol, a naturally occurring diaryl ether of biological relevance. From a mechanistic viewpoint, two competitive pathways depending on the nature of the nucleophile and consistent with the obtained results have been proposed.

A metal and solvent free strategy to functionalize aryl methyl ethers through direct nucleophilic substitution of aryl C-OMe bond has been described. A wide range of O, S, N, and C-centered uncharged nucleophiles has been successfully employed. Using this protocol, functional derivatives of bisthiophene have been synthesized in a straightforward way. The reactions are highly atom-efficient and generate methanol as the only byproduct.

The hydroxyl groups of naphthol and tautomerizable phenol derivatives have been substituted by O-, S-, N-, and C-centered nucleophiles under solvent-free reaction conditions. The products are generated in good to excellent yields. para-Toluenesulfonic acid exhibits the best catalytic activity compared to other Bronsted acids. Experimental observations suggest that the reaction proceeds through the intermediacy of the keto tautomer of naphthol. Nucleophilic addition to the carbonyl group followed by elimination of water generates the desired product. The present methodology provides access to substituted naphtho[2,1-b]furan derivatives. The products generated using N-centered nucleophiles can be further transformed to important classes of organic molecules such as benzocarbazole and imidazole derivatives.

With visible-light irradiation, a simple and metal-free photocatalytic system for the synthesis of diaryl ethers from arylboronic acids and diaryliodonium salts has been developed. The reaction proceeded in high yield for a range of different substrates in the presence of eosin Y under mild reaction conditions.

This paper describes an efficient procedure for palladium(0)-catalyzed N-arylation and O-arylation of aryl halides by Ullmann-type cross coupling reaction under mild reaction conditions in a short reaction time. Two phosphine sulphide ligands and their corresponding Pd(0) complexes namely [Pd(p2S2)(dba)] and [Pd(pp3S4)(dba)], were synthesized, where p2S2 is 1,2-bis(diphenylphosphino)ethane disulfide, pp3S4 is tris[2-(diphenylphosphino)ethyl]phosphine tetrasulfide and dba is dibenzylideneacetone. Optimal reaction conditions were determined for the arylation reactions using iodobenzene and benzimidazole by varying temperature, solvent, base and catalyst loading. The cross coupling reactions were carried out taking iodobenzenes/bromobenzenes and a wide variety of substituted aryl amines/phenols/alcohols with different steric and electronic properties to afford the desired N-aryl amines/diaryl ethers/alkyl aryl ethers in good to excellent yield (70-94%).

Anchored palladium(ii) in functionalized MCM-41 mesoporous silica was prepared and used as an efficient, recoverable and thermally stable heterogeneous nano catalyst for C-C, C-O and C-N bond formation in cross-coupling reactions in the presence of Ph3SnCl. MCM-41 was prepared trough hydrothermal synthesis using tetraethyl orthosilicate (Si(OC2H5)4) as silica source and cetyltrimethylammonium bromide (CTAB) as a template. The structure of functionalized MCM-41 was studied by FT-IR, XRD, SEM, TEM, TGA, EDS, ICP and BET techniques.

The example of palladium-catalyzed intermolecular cyclization for the synthesis of various diarylfurans in which one of the aromatic rings originates from the phenolic part of the starting ester and the other one from PhI(OAc)2 has been reported. The reaction is carried out through two steps: the rearrangement of palladium-associated iodonium ylides to form o-iodo diaryl ether and then palladium catalyzed intramolecular direct arylation. This reaction can tolerate a variety of functional groups and is alternative or complementary to the previous methods for the synthesis of diarylfurans.

This report summarizes research efforts focused on copper acetate mediated reactions to form new carbon-heteroatom bonds using organoboron reagents under ultrasound irradiation. The method involves the application of ultrasound irradiation to the Chan-Evans-Lam reaction to achieve O-arylation of phenols, N-arylation of anilines and indoles, and S-arylation of thiols. Ultrasound irradiation was found to decrease reaction times from 72 hours to 4 hours while improving the product yields an average of 20%.1 Representative C-O, C-N, and C-S coupling reactions were successfully scaled-up from the milligram to gram levels while maintaining good product yields offering potential applications in industrial processes.

CsF/clinoptilolite was found to be an efficient solid base catalyst for both SNAr and Ullmann ether reactions. A general and efficient one-step procedure was developed for the synthesis of biaryl ethers via direct coupling of electron-deficient aryl halides to phenols using CsF/clinoptilolite. The protocol was also applied to electron-rich aryl halides by addition of a catalytic amount of copper oxide nanoparticles. Both SNAr and Ullmann reactions were rapid and provided good to excellent yields.

A magnetically retrievable, efficient, and benign maghemite-Cu nanocatalyst was synthesized from inexpensive precursors and applied for C-O, C-N, and C-S bond-formation reactions. The obtained maghemite-Cu nanocatalyst was characterized by various techniques such as XRD, X-ray photoelectron spectroscopy, field-emission gun SEM with energy-dispersive spectroscopy, atomic absorption spectroscopy, TEM, high-angle annular dark-field scanning transmission electron microscopy, FTIR spectroscopy, and M?ssbauer spectroscopy. Excellent catalytic activity, ease of recovery, and reusability without a significant loss of yield make the present protocol highly sustainable to deal with industrial and environmental concerns. Magnetic attraction: A magnetically retrievable, efficient, and benign maghemite-Cu nanocatalyst is synthesized from inexpensive precursors and applied for C-O, C-N, and C-S bond-formation reactions. Excellent catalytic activity, ease of recovery, and reusability without significant loss of yield make the present protocol highly sustainable to deal with industrial and environmental concerns.

Palladium-catalyzed coupling reactions of aryl halides and phenols are described employing the bulky and electron-rich MOP-type ligands. When K3PO4 was used as base and toluene as solvent, the catalyst system exhibited high efficiency for the coupling reaction of the activated aryl halides. When NaH was used as base and o-xylene as solvent, unactivated aryl halides can be used as substrates.

An economical and eco-compatible ligand-free protocol for the synthesis of diaryl ethers has been developed using easily accessible alumina-supported nickel nanoparticles as a stable recyclable heterogeneous catalyst in aqueous medium along with a surfactant (SDS) and a mild base (K2CO3). Various sensitive functional groups like allyl, alkoxycarbonyl, formyl, oxo, chloro, bromo, amine and nitro were tolerated in the aforesaid method. Excellent chemoselectivity was demonstrated through competition experiments.

A highly porous Zn-based iso-reticular metal-organic framework (IRMOF-3) has been selected for covalent modification. Pyridine-2-aldehyde has been used to decorate the free amine group of IRMOF-3 in the porous matrix. Schiff base moiety thus generated has been availed to anchor copper(II) ions to prepare the desired catalyst that catalyzes O-arylation reactions heterogeneously under mild reaction conditions. Porous catalyst demonstrates size selectivity in products when various substrates undergo O-arylation with α and β-naphthol.

Use of a bismuth catalyst allowed efficient dehydrative substitution of phenolic hydroxy groups with alcohols and thiols to form C-O and C-S bonds. The reaction required equimolar amounts of two readily available substrates that generated H2O as the only byproduct. The relatively mild reaction conditions were compatible with the functional groups selected, and provided excellent chemoselectivity.

In this article, Pd0-nanoparticles supported on natural nanozeolite clinoptilolite (CP) were successfully synthesized, and the catalytic activity of the nanocatalyst was investigated in C-C and C-O coupling reactions, namely the Sonogashira and Ullmann condensation reactions in an aqueous medium. The nanocatalyst was characterized by various techniques such as powder-XRD, BET, SEM, TEM, HRTEM, TEM-EDS, ICP-OES and XPS. From an electron microscopy (SEM) study it can be inferred that the particles are mostly spherical or of ellipsoidal shape and have diameters ranging from 25 to 80 nm. A HRTEM study reveals that Pd0-nanoparticles supported on nanozeolite CP have an average diameter of ～10 nm. The supported palladium nanoparticles showed excellent catalytic activity in the synthesis of aryl alkynes and diaryl ethers in high yields. In addition, the nanocatalyst could be recycled and reused several times without significant loss of catalytic activity.

Efficient Pd supported on ZnO nanoparticles for the ligand-free O-arylation and N-arylation of phenols and various N-H heterocycles with aryl chlorides, bromides, and iodides were readily synthesized and characterized. The amount of palladium on ZnO is 9.84 wt% (0.005 g of the catalyst contains 462 × 10-8 mol% of Pd) which was determined by ICP analysis. This nano sized Pd/ZnO with an average particle size of 20-25 nm and specific surface area 40.61 m2 g-1 was used as a new reusable heterogeneous catalyst for the formation of C-O and C-N bonds in organic synthesis. This protocol gives the arylated product in satisfactory yields without any N2 or Ar flow. The catalyst can be recovered and recycled several times without marked loss of activity.

A series of salicylaldimine ligands were designed to promote the copper-catalyzed Ullmann cross-coupling reaction. After a screening process, 2-((2-isopropylphenylimino)methyl)phenol was found to serve as a good supporting ligand for this reaction. Employing this Schiff-base ligand as a new supporting ligand, the copper-catalyzed coupling reactions of aryl bromides and aryl iodides with various phenols successfully proceeded in good yields under mild conditions. Various diaryl ethers were obtained with excellent yields in dioxane in the presence of K3PO4 and a catalytic amount of copper(I) salt.

The use of picolinic acid amide derivatives as an effective family of bidentate ligands for copper-catalysed aryl ether synthesis is reported. A fluorine-substituted ligand gave good results in the synthesis of a wide range of aryl ethers. Even bulky phenols, known to be very challenging substrates, were shown to react with aryl iodides with excellent yields using these ligands. At the end of the reaction, the first examples of end-of-life Cu species were isolated and identified as CuII complexes with several of the anionic ligands tested. A preliminary mechanistic investigation is reported that suggests that the substituents on the ligands might have a crucial role in determining the redox properties of the metal centre and, consequently, its efficacy in the coupling process. An understanding of these effects is important for the development of new efficient and tunable ligands for copper-based chemistry.

Herein, we introduce the first magnetic CuO nanoparticles based on carbon nanotubes as a highly intriguing magnetic catalyst in Ullmann-type coupling of aryl halides with phenols. Two facile procedures were used for the preparation of this magnetically separable catalytic system. Having been treated with FeSO4 and then H2O2, nanotubes accommodated the resulting iron hydroxides on the walls. The resulting nanocomposite was then exposed to argon atmosphere at 450°C giving rise to a carbon nanotube-supported α-Fe2O3 compound. Ultimately, copper acetate was hydrolysed in the presence of CNT supported α-Fe 2O3 at 100°C and our novel catalyst was gained. Some spectroscopic and microscopic techniques such as Infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD), Vibrational sample magnetometry (VSM), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), Inductively coupled plasma (ICP), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) corroborated the structure of the catalyst. The catalyst synthesized showed good activity in C-O cross coupling reactions affording the highest rate of completion. Magnetic feature of the catalyst helped facile separation of it from the reaction medium. The catalyst could also be reused up to six times without any loss of its activity.

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An active and stable magnetically separable Pd nanocatalyst was prepared and characterized. The nanocatalyst exhibited excellent activities and reusabilities in aqueous phase processes including the O-arylation of phenols and Sonogashira cross-coupling reactions. The proposed protocol features mild reaction conditions and an extraordinary simplicity and efficiency using NaOH as base in water.

Potassium tert-butoxide mediated carbon-chalcogen C-E (E=O, S and Se) coupling reaction has been studied from aryl bromide and phenol/aryl disulfide/diselenide substrates. A series of unsymmetrical diaryl chalcogenides were accessed from aryl bromide and diaryl dichalcogenide precursors by using 2.5 equiv of potassium tert-butoxide in DMSO at 80 C. Unsymmetrical diaryl ethers were also obtained by using phenol precursors at 40-45 C. Aryl bromides with methyl, trifluoromethyl, methoxy and nitro substituents showed compatibility in the carbon-chalcogen bond forming reaction. 4-Methoxy, methyl, trifluoromethyl substituted bromobenzene substrates gave two regioisomers: 3-substituted and 4-substituted diaryl chalcogenides when reacted with phenols/diaryl disulfides/diselenides. Formation of two regioisomeric diaryl chalcogenides in the reaction mixture suggests that potassium tert-butoxide reacts with bromobenzene to produce benzyne intermediate, which subsequently reacts with diaryl dichalcogenides and finally give a regioisomeric mixture of 4-substituted and 3-substituted diaryl chalcogenides.

2-Carbomethoxy-3-hydroxyquinoxaline-di-N-oxide was identified as an efficient novel ligand for the copper-catalyzed coupling of aryl halides with various phenols under mild conditions. The catalytic system shows great functional-group tolerance and excellent reactive selectivity.

Herein, an efficient method for the Ullmann C-O coupling reaction between various kinds of phenols and aryl halides, including amino, ketone, cyano, methyl, methoxy, fluoro, chloro and bromo derivatives, is described. The catalyst used, copper ferrite (CuFe2O4) nanoparticles, are easily made, air-stable, and of low cost. The catalyst can be recycled easily just by using an external magnet. Even in the presence of sensitive substituents, the reaction proceeds successfully to provide the desired products in high yields without protection of other functional groups. Copyright

Copper(II) trans-bis-(glycinato) complex, easily prepared by the solid state reaction of copper(II) acetate and glycine (trans-[Cu(glyo) 2·H2O]) was found to be an efficient, recyclable, and high yielding catalyst for the Ullmann type synthesis of diaryl ethers via the cross coupling of phenols with aryl halides without using any additives at relatively low reaction temperature. The catalyst could easily be recovered by simple filtration and was reused for several runs with consistent catalytic activity.

A novel ligand-free, highly efficient, and an inexpensive method has been developed by using ecofriendly, heterogeneous reusable copper fluorapatite (CuFAP) catalyst for the synthesis of diaryl ethers from the cross coupling reaction of the various substituted aryl halides (fluoride, chloride, bromide, and iodide) with the potassium salts of various substituted phenols in the presence of N-methyl 2-pyrrolidone (NMP) as a solvent at 120 °C. The protocol obtained the corresponding cross coupling products in good to excellent yield. The CuFAP catalyst was recovered by simple filtration from the reaction mixture and reused several times without the loss of catalytic activity.

An efficient Cu-catalyzed O-arylation was carried out by involving phenols with iodoarenes to afford various substituted diarylether derivatives with tiny loading of Cu2O and 1H-imidazole-4-carboxylic acid as catalytic system under mild conditions, which provided good to excellent yields with good tolerance of functional groups.

Employing methenamine as a new supporting ligand, the copper-catalyzed coupling reactions of aryl bromides or aryl iodides with various phenols successfully proceeded in good yields under mild conditions. A series of diaryl ethers were obtained with excellent yields in the presence of K 3PO4 and copper(I) salt. Copyright

A practical and mild strategy has been developed for the cross-coupling of O-arylation of phenol with differently substituted aryl halides and heteroaryl iodides using low catalyst loading of copper iodide under low operating temperature in DMF with TMHD as the ligand and Cs2CO3 as the base. This method tolerates a variety of functional groups including sterically hindered phenols and heteroaryl iodides to afford products in good to excellent yields (up to 95%). Georg Thieme Verlag Stuttgart. New York.

Low catalytic amount CuI and Fe(acac)3 were found to effectively promote the C-O cross-coupling reaction in the presence of K2CO 3 as the base. A serious of diaryl ethers with different substitutents can be synthesized in good to excellent yields. This efficient and economic method is attractive for applications on an industrial scale. Georg Thieme Verlag Stuttgart New York.

The alkylation of phenol derivatives can be achieved in good yield via Lewis or Bronsted acid. The only by-product of the reaction is water and the catalyst can be recycled when using Bronsted acid.

An efficient and inexpensive synthesis of diaryl ethers has been developed. The process involves the nucleophilic aromatic substitution of electron-deficient aryl halides and phenols and is mediated by potassium fluoride/Clinoptilolite (KF/CP) in dimethyl sulfoxide (DMSO). The approach affords good to excellent yields of the arylated products without the need for additional cation capture. The solid base is also efficient in the Ullmann ether synthesis. A new, inexpensive solid base for the synthesis of diaryl ethers has been developed. Clinoptilolite, a natural zeolite with a high tendency for cation capture, combined with potassium fluoride, provides an efficientsolid base for the deprotonation of phenols in nucleophilic reactions. The same solid base acts as a reliable base for the copper-catalyzed synthesis of diaryl ethers. Copyright

An efficient alumina-supported CuO-catalyzed O-arylation of phenols and aliphatic alcohols with various aryl as well as heteroaryl halides under ligand-free conditions are reported. This protocol provides a variety of diaryl ether and bis-diaryl ether motifs by reacting different aryl/aliphatic halides with differently substituted phenols and saturated alcohols in the presence of a catalytic amount of CuO on alumina and KOH as a base at moderate temperature under nitrogen atmosphere. The described methodology is simple, straightforward and efficient to afford the cross-coupled products in high yields under ligand-free conditions. The explored catalyst is inexpensive, air-stable and recyclable up to three cycles.

A very simple bishydrazone-type ligand, glyoxal bis(phenylhydrazone) (L1), was found to effectively promote the CuI-catalyzed O-arylation of phenols with aryl bromides. This cross-coupling reaction proceeded in acetonitrile at 60-80 °C in the presence of K3PO4 as base. A diverse array of phenols and bromoarenes was employed as substrates to afford diaryl ethers in good to excellent yields, and some base-sensitive groups, such as ester, aldehyde, and ketone groups, can survive under the mild reaction conditions.