- Unexpected activation of carbon-bromide bond promoted by palladium nanoparticles in Suzuki C-C couplings
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Dihydroanthracene derivatives (1-6) containing imide (1-3) and amine (4-6) functions have been used for the stabilization of palladium nanoparticles, starting from Pd(0) and Pd(ii) organometallic precursors. Well-dispersed nanoparticles of mean size in the range ca. 1.9 to 3.6 nm could be obtained using Pd(0) precursors (PdLc and PdLd, where L = 1-6 and c and d mean the organometallic precursor involved, [Pd2(dba)3] and [Pd(ma)(nbd)] respectively). With the aim to evaluate the behaviour of homogeneous species and nanoparticles used as catalytic precursors, palladium complex coordinated to the diamine 6, [Pd(OAc)2(κ2- N,N-6)], was prepared, reporting for the first time the X-ray diffraction structure of a metallic complex containing a ligand with a 9,10- dihydroanthracene backbone. Palladium systems were evaluated in Suzuki C-C coupling reactions and relevant differences were observed comparing the reactivity of the homogeneous systems in relation to that obtained using palladium nanoparticles as starting catalyst in relation to the activation of the C-Br bonds for deactivated substrates.
- Sanhes, Delphine,Raluy, Eva,Retory, Stephane,Saffon, Nathalie,Teuma, Emmanuelle,Gomez, Montserrat
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- Silver nanoparticles doped TiO2 catalyzed Suzuki-coupling of bromoaryl with phenylboronic acid under visible light
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The formation of the carbon?carbon bond in the synthetic chemistry explored in many ways. Suzuki-cross coupling is one of the ways to make bonds between two carbon atoms of similar molecules or different molecules. C–C bond was successfully formed between two aryl rings of aryl halides and phenylboronic acid at room temperature and atmospheric pressure under the visible illuminance. In this work we report, an in-situ synthesis of silver nanoparticles doped TiO2 nanoparticles (NPs) and studied its catalytic activity as an eco-friendly, simple, recyclable and efficient catalyst for one-pot Suzuki-coupling of bromoaryl with phenylboronic acid under visible light. Only, 45 mg of the catalyst resulted in a 98% conversion of p-ethyl bromobenzene with a 97% yield of p-ethyl biphenyl using toluene as the solvent in the presence of visible light at atmospheric pressure. The electron-donating groups (e.g., ethyl group) substituted bromobenzene resulted in the maximum yields than that of the substitution with the electron-withdrawing groups. The catalyst shown significant catalytic activity up to seven recycling runs without any loss. The doping of silver nanoparticles boosted the catalytic activity at titanium dioxide surface as well as inside the pores. The high surface area of the semiconductor support provides the sites for accommodated silver nanoparticles and shows enhanced reactivity towards the coupling reaction of bromoaryl with phenylboronic acid. The as-synthesized catalyst was thoroughly characterized by XRD, TEM, EDX, XPS, FTIR, TGA, UV–vis, Raman and BET analysis. The high recyclability of the photocatalyst remarked the footprints in the C–C coupling reactions.
- Chen, Yuning,Feng, Li
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Read Online
- Ligand- and Counterion-Assisted Phenol O-Arylation with TMP-Iodonium(III) Acetates
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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.
- Kikushima, Kotaro,Miyamoto, Naoki,Watanabe, Kazuma,Koseki, Daichi,Kita, Yasuyuki,Dohi, Toshifumi
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supporting information
p. 1924 - 1928
(2022/03/27)
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- Bis(NHC)-Pd-catalyzed one-pot competitive C-C*C-C, C-C*C-O, C-C*C-N, and C-O*C-N cross-coupling reactions on an aryl di-halide catalyzed by a homogenous basic ionic liquid (TAIm[OH]) under base-free, ligand-free, and solvent-free conditions
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Bis(NHC)-Pd-catalyzed competitive asymmetrical C-C*C-C, C-C*C-O, C-C*C-N, and O-C*C-N cross-coupling reactions were performedviathe one-pot strategy in the presence of a new ionic liquid, which played the roles of solvent, base, and ligand simultaneously. The ionic liquid was prepared based on a methyl imidazolium moiety with hydroxyl counter anionsviaa Hofmann elimination on a 1,3,5-triazine framework (TAIm[OH]). Pd ions could be efficiently coordinated through the bis(NHC)-ligand moiety in the ionic liquid. Based on differences in the competitive kinetics of C-C cross-coupling reactions (Heck, Suzuki, and Sonogashira) with C-N and C-O cross-coupling reactions, and also differences in the kinetics of aryl halides, the coupling reactions could be selectively performed with a low amount of by-products. The competitive cross-coupling reactions were thus performed with high selectivity under mild reaction conditions.
- Zhu, Yanfang,Xu, Guiyang,Kazemnejadi, Milad
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p. 11662 - 11671
(2021/07/11)
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- Sustainable and recyclable magnetic nanocatalyst of 1,10-phenanthroline Pd(0) complex in green synthesis of biaryls and tetrazoles using arylboronic acids as versatile substrates
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A magnetic nanocatalyst was purveyed as a heterogeneous recoverable palladium-based catalyst anchored on green, sustainable and phosphine free support. Resulted Fe3O4@SiO2-Phen-Pd(0) nanocatalyst bearing powerful phenanthroline ligand was thoroughly characterized by physicochemical approaches like UV–vis, FT-IR, EDX, XRD, TGA, ICP, VSM, DLS, FESEM, and TEM analyses. After finding trustable data, the obtained magnetic catalyst was considered to be applied in the Suzuki-Miyaura type C-C couplings and getting corresponding tetrazoles using arylboronic acid derivatives as alternate precursors of aromatic halides and stupendous data were observed.
- Bagherzadeh, Nastaran,Sardarian, Ali Reza,Eslahi, Hassan
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- Green and sustainable palladium nanomagnetic catalyst stabilized by glucosamine-functionalized Fe3O4@SiO2 nanoparticles for Suzuki and Heck reactions
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A novel magnetic and heterogeneous palladium-based catalyst stabilized by glucosamine-functionalized magnetic Fe3O4@SiO2 nanoparticle was synthesized. The strategy relies on the covalently bonding of glucosamine to cyanuric chloride-functionalized magnetic nanoparticles followed by complexation with palladium. The structure of magnetic nanocatalyst was fully determined by FT-IR, XRD, DLS, FE-SEM, TEM, ICP, UV-Vis, TGA, VSM, and EDX. The obtained results confirmed that the palladium nanoparticles stabilized by glucosamine immobilized onto the magnetic support exhibited high activity in cross-coupling reactions of Suzuki-Miyaura and Mizoroki-Heck. Various aryl halides were coupled with arylboronic acid (Suzuki cross-coupling reaction) and olefins (Heck reactions) under the green conditions to provide corresponding products in high to excellent yields. Interestingly, the catalyst can be easily isolated from the reaction media by magnetic decantation and can subsequently be applied for consecutive reaction cycles (at least seven times) with no notable reduction in the catalytic activity.
- Eslahi, Hassan,Sardarian, Ali Reza,Esmaeilpour, Mohsen
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- Nickel-Catalyzed Etherification of Phenols and Aryl Halides through Visible-Light-Induced Energy Transfer
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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.
- Zhu, Da-Liang,Jiang, Shan,Wu, Qi,Wang, Hao,Li, Hai-Yan,Li, Hong-Xi
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supporting information
p. 8327 - 8332
(2021/10/25)
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- Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates
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A metal-free route for the synthesis of biarenes has been developed. The approach is based on the photoextrusion of a phosphate moiety occurring upon irradiation of biaryl- A nd triaryl phosphates. The reaction involves an exciplex as the intermediate and it is especially suitable for the preparation of electron-rich biarenes.
- Qrareya, Hisham,Meazza, Lorenzo,Protti, Stefano,Fagnoni, Maurizio
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supporting information
p. 3008 - 3014
(2021/01/18)
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- Trimethoxyphenyl (TMP) as a Useful Auxiliary for in situ Formation and Reaction of Aryl(TMP)iodonium Salts: Synthesis of Diaryl Ethers
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Herein, we describe a synthetic approach for arylation that exploits the in situ formation and reaction of an unsymmetrical diaryliodonium salt. In this way, aryl iodides are used as reagents in a metal-free reaction with phenols, and a trimethoxyphenyl (TMP) group is used as a “dummy” group to facilitate transfer of a wide range of aryl moieties. The scope of aryl electrophiles and phenol nucleophiles is broad (>30 examples) and the yields are high (52–95%, 80% avg.). One-pot coupling reactions avoid the synthesis of diaryliodonium salts and provide opportunities for sequential reactions and novel chemoselectivity. (Figure presented.).
- Gallagher, Rory T.,Basu, Souradeep,Stuart, David R.
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supporting information
p. 320 - 325
(2019/12/11)
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- Shuttling Catalyst: Facilitating C?C Bond Formation via Cross-Couplings with a Thermoresponsive Polymeric Ligand
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A poly(ethylene glycol) (PEG) linked ortho-MeO-phenyldicyclohexylphosphine (MeO-WePhos) ligand has been synthesized to promote Pd-catalyzed carbon-carbon bond formation by cross-couplings including Sonogashira, Heck, Hiyama and Stille reactions, providing corresponding (hetero)aryl substituted alkynes, alkenes and bi(hetero)aryls in good to excellent isolated yields with low Pd loadings. Facilitated by the lower critical solution temperature behaviour of the polymeric monophosphine ligand, the metal-complex could rapidly shuttle between organic and water phases as regulated by temperature, enabling highly efficient catalyst recycling via a simple phase separation. The chemical structure of ligand was determined by matrix-assisted laser desorption/ionization-time of flight mass spectrometry, nuclear magnetic resonance spectrometry and size-exclusion chromatography measurements. Notably, as demonstrated by the inductively coupled plasma-atomic emission spectrometry measurement, 98% Pd was kept in the water phase after 6 cycles of catalyst recycling experiments. Given the profound impact of transition-metal-catalyzed covalent bond formation and the increasing demand of sustainable chemistry, this work provides an alternative method to conduct cross-couplings with a polymeric shuttling catalyst.
- Wang, Erfei,Zhang, Jiawei,Zhong, Zhuoran,Chen, Kaixuan,Chen, Mao
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p. 419 - 423
(2020/01/08)
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- Immobilized Pd on a NHC functionalized metal–organic framework MIL-101(Cr): an efficient heterogeneous catalyst in Suzuki?Miyaura coupling reaction in water
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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.
- Khalafi-Nezhad, Ali,Niknam, Esmaeil,Panahi, Farhad
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- Nickel(ii) N-heterocyclic carbene complexes as efficient catalysts for the Suzuki—Miyaura reaction
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Catalytic activity of nickel(ii) and palladium(ii) N-heterocyclic carbene (NHC) complexes derived from imidazole, benzimidazole, and 1,2,4-triazole was comparatively evaluated in the cross-coupling reactions of aryl halides with arylboronic acids. Readily available nickel bis-NHC complexes (NHC)2NiX2 (X = Cl, Br, or I) exhibited the activity comparable to that of the structurally related palladium complexes and, consequently, can be applied as efficient catalysts for the Suzuki—Miyaura reaction.
- Astakhov, A. V.,Chernyshev, V. M.,Pasyukov, D. V.,Soliev, S. B.
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p. 683 - 690
(2020/05/04)
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- Synthesis and catalytic activity of ionic palladium N-heterocyclic carbene complexes
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The synthesis of 3 benzimidazole-based ionic Pd(II)-NHC complexes (NHC: N -heterocyclic carbene) is presented. The structures of the complexes are as follows: [NHC-PdBr 3 ] ? [NHC] + . The ionic palladium(II)-NHC complexes were synthesized in high yields and were fully characterized by nuclear magnetic resonance spectroscopy, X-ray diffraction, LC-MS/MS, and elemental analysis. These complexes have been identified as active catalysts in Suzuki–Miyaura reactions in a solution of 2-propanol and water at room temperature for different aryl bromides.
- Ya?ar, Sedat,Akko?, Mitat,?zdemir, Nam?k,?zdemir, ?smail
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p. 1622 - 1633
(2020/01/03)
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- Nickel-Catalyzed Amination of Silyloxyarenes through C–O Bond Activation
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Silyloxyarenes were utilized as electrophilic coupling partners with amines in the synthesis of aniline derivatives. A diverse range of amine substrates were used, including cyclic or acyclic secondary amines, secondary anilines, and sterically hindered primary anilines. Additionally, a range of sterically hindered and unhindered primary aliphatic amines were employed, which have previously been challenging with other classes of aryl ether electrophiles. Orthogonal couplings of silyloxyarenes with aryl methyl ethers are illustrated, where selectivity between the two C?O electrophiles is determined by ligand control, thereby allowing complementary and selective late-stage diversification of either electrophile. Finally, a sequential coupling displays the utility of this amination method along with the reversal in intrinsic reactivity between aryl methyl ethers and silyloxyarenes.
- Wiensch, Eric M.,Montgomery, John
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supporting information
p. 11045 - 11049
(2018/07/31)
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- Pd–Ni bimetallic nanoparticles supported on ZrO2 as an efficient catalyst for Suzuki–Miyaura reactions
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Pd–Ni bimetallic nanoparticles (BMNPs) supported on ZrO2 were prepared by an impregnation–reduction method. The BMNPs showed excellent catalytic performance in Suzuki carbon–carbon cross-coupling reactions and almost quantitative conversion of the substrates was obtained under mild conditions in the absence of ligand. The excellent catalytic performance of the bimetallic catalyst could be a result of the synergistic effect between the two metal components. The catalyst showed outstanding recyclability during the reaction process; no obvious decrease in catalytic performance was observed after five cycles.
- Zhang, Li-Jie,Yao, Xian,Sun, Ying-xin,Zhang, Jia-wei,Cai, Chun
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p. 419 - 423
(2018/09/12)
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- Pd-PEPPSI complexes based on 1,2,4-triazol-3-ylidene ligands as efficient catalysts in the Suzuki—Miyaura reaction
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The palladium complexes of the Pd-PEPPSI type with N-heterocyclic carbenes of the 1,2,4-triazole series were synthesized in 76—99% yields by the reactions of PdCl2 with 1,4-di- alkyl-1,2,4-triazolium salts in pyridine in the presence of KBr or KI as sources of halide ions and tetrabutylammonium salts as phase-transfer catalysts. The obtained complexes can be used as efficient catalysts for the Suzuki—Miyaura cross-coupling and are not inferior to the commercially available Pd-PEPPSI catalysts in activity.
- Chernenko, A. Yu.,Astakhov,Pasyukov,Dorovatovskii,Zubavichus, Ya. V.,Khrustalev,Chernyshev
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- The Suzuki-Miyaura Coupling of Nitroarenes
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Synthesis of biaryls via the Suzuki-Miyaura coupling (SMC) reaction using nitroarenes as an electrophilic coupling partners is described. Mechanistic studies have revealed that the catalytic cycle of this reaction is initiated by the cleavage of the aryl-nitro (Ar-NO2) bond by palladium, which represents an unprecedented elemental reaction.
- Yadav, M. Ramu,Nagaoka, Masahiro,Kashihara, Myuto,Zhong, Rong-Lin,Miyazaki, Takanori,Sakaki, Shigeyoshi,Nakao, Yoshiaki
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p. 9423 - 9426
(2017/07/24)
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- Copper-Catalyzed Diaryl Ether Formation from (Hetero)aryl Halides at Low Catalytic Loadings
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Diaryl formation is achieved by coupling phenols and (hetero)aryl halides under the catalysis of CuI/N,N′-bis(2-phenylphenyl) oxalamide (BPPO) or CuI/N-(2-phenylphenyl)-N′-benzyl oxalamide (PPBO) at 90 °C using DMF or MeCN as the solvent. Only 0.2-2 mol % CuI and ligand are required for complete conversion, which represents the lowest catalytic loadings for a general Cu/ligand-catalyzed diaryl ether formation.
- Zhai, Yuntong,Chen, Xiaofei,Zhou, Wei,Fan, Mengyang,Lai, Yisheng,Ma, Dawei
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p. 4964 - 4969
(2017/05/12)
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- CuI/oxalamide catalyzed couplings of (hetero)aryl chlorides and phenols for diaryl ether formation
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Couplings between (hetero)aryl chlorides and phenols can be effectively promoted by CuI in combination with an N-aryl-N′-alkyl-substituted oxalamide ligand to proceed smoothly at 120 °C. For this process, N-aryl-N′-alkyl-substituted oxalamides are more effective ligands than bis(N-aryl)-substituted oxalamides. A wide range of electron-rich and electron-poor aryl and heteroaryl chlorides gave the corresponding coupling products in good yields. Satisfactory conversions were achieved with electron-rich phenols as well as a limited range of electron-poor phenols. Catalyst and ligand loadings as low as 1.5 mol % are sufficient for the scaled-up variants of some of these reactions. Aryl and alkyl: N-Aryl-N′-alkyl-substituted oxalamide ligands promote the CuI catalyzed coupling of (hetero)aryl chlorides and phenols at 120 °C more effectively than bis(N-aryl)-substituted oxalamides. A wide range of electron-rich and electron-poor aryl and heteroaryl chlorides were converted into the corresponding coupling products in good yields.
- Fan, Mengyang,Zhou, Wei,Jiang, Yongwen,Ma, Dawei
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supporting information
p. 6211 - 6215
(2016/05/24)
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- A counteranion triggered arylation strategy using diaryliodonium fluorides
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A mild and transition metal-free counteranion triggered arylation strategy has been developed using diaryliodonium fluorides. The fluoride counteranion within the hypervalent iodonium species displays unusual reactivity that activates a phenolic O-H bond leading to electrophilic O-arylation. A wide range of phenols and diaryliodonium salts are compatible with this transformation under remarkably mild conditions. Furthermore, we pre-empt the wider implications of this strategy by demonstrating the compatibility of the arylation tactic with latent carbon nucleophiles.
- Chan,McNally,Toh,Mendoza,Gaunt
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p. 1277 - 1281
(2015/02/05)
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- Mesoporous nitrogen-doped carbon for copper-mediated Ullmann-type C-O/-N/-S cross-coupling reactions
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Copper-driven Ullmann-type cross-coupling reactions are regarded as one of the most important methods for the C-O, C-N, C-S and some other bonds formation. Herein, we report that mesoporous nitrogen-doped carbon materials with high nitrogen content function as novel, active and recyclable N-type heterogeneous promoters for copper-catalyzed cross-couplings. By using CuI as the catalyst and a mesoporous nitrogen-doped carbon material as the promoter, the Ullmann-type coupling reactions of various aryl halides with phenols, amines, imidazol, and thiophenols at 100 °C gave the corresponding products in good yields. Inspired by the efficiency of mesoporous nitrogen-doped carbon material as a promoter, nitrogen-doped carbon supported CuO nanoparticles are prepared and successfully employed as efficient heterogeneous catalysts in the C-O cross-coupling reactions. Furthermore, the nitrogen-doped carbon material supported CuO can be simply recycled by centrifugation and reused at least four times with trace copper leaching. The mesoporous nitrogen-doped carbon materials as heterogeneous promoters or copper-based catalyst supports may represent a promising catalyst system in modern Ullmann chemistry, which indeed could lead to improved processing steps.
- Zhang, Pengfei,Yuan, Jiayin,Li, Haoran,Liu, Xiaofeng,Xu, Xuan,Antonietti, Markus,Wang, Yong
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p. 1890 - 1895
(2013/03/13)
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- Ligand free, highly efficient synthesis of diaryl ether over copper fluorapatite as heterogeneous reusable catalyst
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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.
- Mulla, Shafeek A.R.,Inamdar, Suleman M.,Pathan, Mohsinkhan Y.,Chavan, Santosh S.
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experimental part
p. 1826 - 1829
(2012/05/04)
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- Fe3O4@mesoporouspolyaniline: A highly efficient and magnetically separable catalyst for cross-coupling of aryl chlorides and phenols
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A high surface, magnetic Fe3O4@mesoporouspolyaniline core-shell nanocomposite was synthesized from magnetic iron oxide (Fe 3O4) nanoparticles and mesoporouspolyaniline (mPANI). The novel porous magnetic Fe3O4 was obtained by solvothermal method under sealed pressure reactor at high temperature to achieve high surface area. The mesoporouspolyaniline shell was synthesized by in situ surface polymerization onto porous magnetic Fe3O4 in the presence of polyvinylpyrrolidone (PVP) and sodium dodecylbenzenesulfonate (SDBS), as a linker and structure-directing agent, through 'blackberry nanostructures' assembly. The material composition, stoichiometric ratio and reaction conditions play vital roles in the synthesis of these nanostructures as confirmed by variety of characterization techniques. The role of the mesoporouspolyaniline shell is to stabilize the porous magnetic Fe3O4 nanoparticles, and provide direct access to the core Fe3O4 nanoparticles. The catalytic activity of magnetic Fe3O 4@mesoporousPANI nanocomposite was evaluated in the cross-coupling of aryl chlorides and phenols. Copyright
- Arundhathi,Damodara,Likhar, Pravin R.,Kantam, M. Lakshmi,Saravanan,Magdaleno, Travis,Kwon, Sun Hee
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supporting information; experimental part
p. 1591 - 1600
(2011/08/03)
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- Efficient catalytic activity of copper/aluminum hydrotalcite in diaryl ether synthesis
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A simple copper/aluminum hydrotalcite (Cu/Al-HT) catalyzed arylation of phenols with aryl iodides afforded the corresponding diaryl ethers in moderate to excellent yields. This ligand- free Cu/Al-HT catalyzed coupling of aryl iodides with phenols resulted in high yields of diaryl ethers in the absence of an additive. The catalyst was quantitatively recovered from the reaction by simple filtration and reused for a number of cycles. Georg Thieme Verlag Stuttgart New York.
- Sreedhar,Arundhathi,Reddy, M. Amarnath,Kantam, M. Lakshmi
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experimental part
p. 483 - 487
(2009/07/11)
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- Iron-catalyzed C-O cross-couplings of phenols with aryl iodides
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(Chemical Equation Presented) Low-price coupling: A versatile, practical, and cost-efficient iron-catalyzed O-arylation protocol is applied to the synthesis of a variety of diaryl ethers, which are formed in high yields. Best results were obtained by using FeCl3 and a β-diketo ligand.
- Bistri, Olivia,Correa, Arkaitz,Bolm, Carsten
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p. 586 - 588
(2008/09/20)
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- Efficient synthesis of aryl vinyl ethers exploiting 2,4,6- trivinylcyclotriboroxane as a vinylboronic acid equivalent
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The synthesis of functionalized aryl vinyl ether derivatives can be readily achieved utilizing a room-temperature copper(II) acetate mediated coupling of substituted phenols with 2,4,6-trivinylcyclotriboroxane-pyridine complex in the presence of a suitable base. The scope of the procedure was demonstrated by the generation of an array of substituted aryl vinyl ethers. The reaction was seen to be tolerant of a diverse range of functional groups yielding products in high isolated yields. We have shown that one role of an amine base in the reaction sequence is the in situ generation of an amine coordinated boroxine ring. An X-ray crystal structure and low temperature 11B NMR study of 2,4,6-trivinylcyclotriboroxane-pyridine complex demonstrated the nature of the tetracoordinate boron species, which may have a key role to play within the reaction sequence.
- McKinley, Neola F.,O'Shea, Donal F.
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p. 5087 - 5092
(2007/10/03)
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- A Convenient Palladium/Ligand Catalyst for Suzuki Cross-Coupling Reactions of Arylboronic Acids and Aryl Chlorides
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The Pd/ligand A catalyst efficiently catalyzes general Suzuki biaryl cross-coupling reactions of arylboronic acids and aryl chlorides. - Keywords: Arylboronic acid; aryl chloride; catalysis; palladium; phosphine
- Bei, Xiaohong,Crevier, Thomas,Guram, Anil S.,Jandeleit, Bernd,Powers, Timothy S.,et al.
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p. 3855 - 3858
(2007/10/03)
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- Palladium/P,O-Ligand-Catalyzed Suzuki Cross-Coupling Reactions of Arylboronic Acids and Aryl Chlorides. Isolation and Structural Characterization of (P,O)-Pd(dba) Complex
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The phenyl backbone-derived P,O-ligands 1 and 2 were investigated for their utility as ligands in palladium/ligand-catalyzed Suzuki reactions. The 2-(2′-dicyclohexylphosphinophenyl)-2-methyl-1,3-dioxolane (ligand 1) in combination with Pd(dba)2 affords an efficient catalyst for general Suzuki reactions of a wide variety of arylboronic acids and aryl chlorides, bromides, and iodides to afford the desired biaryl products in high isolated yields. Arylboronic acids and aryl chlorides containing electron-poor, electron-rich, and ortho substituents participate effectively. In contrast, the structurally related ligand 2-(2′-dicyclohexylphosphinophenyl)-1,3-dioxolane (ligand 2) was found to be less efficient under similar conditions. The reaction of ligand 1 with Pd(dba)2 affords the complex LPd-(dba) (14, L = 1). The NMR spectroscopic and X-ray crystallographic data of complex 14 establish that ligand 1 functions as a P,O-chelating ligand in complex 14. The reaction of ligand 2 (2 equiv) with Pd(dba)2 and excess 4-tBu-C6H4Br or the ligand displacement reaction of {Pd[P(o-tolyl)3](4-tBu-C6H4)(μ-Br)} 2 with ligand 2 affords the bis-phosphine complex L2Pd(4-tBu-C6H4)(Br) (13, L = 2). The NMR spectroscopic data of complex 13 establish that ligand 2 in complex 13 functions as a nonchelating ligand. Thus, the higher efficiency of ligand 1 over ligand 2 in Pd/L-catalyzed Suzuki arylation of aryl chlorides can be ascribed to the ability of ligand 1 to generate and stabilize monophosphine P,O-chelating Pd/L intermediates, which appear to be most suitable for Suzuki arylation reactions involving certain substrates and conditions.
- Bei, Xiaohong,Turner, Howard W.,Weinberg, W. Henry,Guram, Anil S.,Petersen, Jeffrey L.
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p. 6797 - 6803
(2007/10/03)
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- Mechanisms of the photochemical rearrangement of diphenyl ethers
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The mechanism of the photochemical rearrangement of diphenyl ether (1a) was studied. Irradiation of 1a in ethanol gave 2-phenylphenol (2, 42%) and 4-phenylphenol (3, 11%) as rearrangement products, in addition to phenol (4, 30%) and benzene (5, 25%) as diffusion products. Cross-coupling experiments employing [2H10]1a demonstrated that the formation of 2- and 4-phenylphenol was an intramolecular process. Irradiation of 1a in benzene or in toluene gave biphenyls in good yields. The combined yields of rearrangement products (2 and 3) increased with increase of solvent viscosity, with a concomitant decrease in the formation of 4. All the results can be rationalized in terms of excitation of 1a to the singlet state and dissociation to a radical pair intermediate involving phenoxy and phenyl radicals. Intramolecular recombination of these radicals gives rearrangement products, and escape followed by hydrogen abstraction from the solvent gives diffusion products. When position 4 of 1a was occupied by an electron-donating substituent (1b-e), aryloxy-phenyl bond cleavage to give the corresponding rearrangement products prevailed over phenoxy-aryl bond cleavage. The opposite was the case for substrates with an electron-withdrawing substituent at position 4 (1h,i).
- Haga, Naoki,Takayanagi, Hiroaki
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p. 735 - 745
(2007/10/03)
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- Reactions of Organic Derivatives of Divalent Lanthanides with 1,4-Benzoquinone
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Complete and partial deoxygenation of 2,5-cyclohexadienolates formed by reaction of organic derivatives of divalent lanthanides (RLnX, R2Ln) with 1,4-benzoquinone was studied.The reaction directions are determined by a number of factors, namely: ionization potential of the divalent lanthanide, its ionic radius, nucleophilicity and steric characteristics of the group R, and also by contribution of group R to the structural stabilization of deoxygenation products.
- Starostina, T. A.,Syutkina, O. P.,Rybakova, L. F.,Petrov, E. S.
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p. 1014 - 1017
(2007/10/03)
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