- Electron Spin Resonance of Difluorobiphenyls in the Phosphorescent Triplet States. s-cis and s-trans Conformers and Fluorine Hyperfine Structure
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Electron spin resonance spectra of 2,2'-, 3,3'- and 4,4'-difluorobiphenyls (2DFBP, 3DFBP, and 4DFBP, respectively) in their phosphorescent triplet states have been studied in various matrices at 77 K.Two sets of peaks corresponding to the s-cis and s-trans conformers are observed for 2DFBP and 3DFBP.By using a stretched poly(vinyl alcohol) film as a host, the observed individual peaks are assigned.The 19F hyperfine splitting is obtained for 2DFBP and 4DFBP with a microwave magnetic field parallel to an external magnetic field (BBrf), which is different from the conventional resonance condition of BBrf.
- Tanigaki, Katsumi,Yagi, Mikio,Higuchi, Jiro
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Read Online
- Reductive Coupling of Aryl Halides via C—H Activation of Indene
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This paper describes the first case of a reductive coupling reaction with indene, a non-heteroatom olefin used as a reducing agent. The scope of the substrate is wide. The homo-coupling, cross-coupling, and synthesis of 12 and 14-membered rings were realized. The control experiment, indene-product curve and density functional theory calculations showed that the η3-palladium indene intermediate was formed by C—H activation in the presence of cesium carbonate. We speculate that the final product was obtained through a Pd (IV) intermediate or aryl ligand exchange. In addition, we excluded the formation of palladium anion (Pd(0)?) intermediates.
- Zhang, Bo-Sheng,Yang, Ying-Hui,Wang, Fan,Gou, Xue-Ya,Wang, Xi-Cun,Liang, Yong-Min,Li, Yuke,Quan, Zheng-Jun
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p. 1573 - 1579
(2021/05/28)
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- Synthesis of biaryl compounds via Suzuki homocoupling reactions catalyzed by metal organic frameworks encapsulated with palladium nanoparticles
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Heterogeneous homocoupling reactions of phenylboronic acids were greatly accelerated via Suzuki homocoupling reactions. In this work, a tandem route was designed which firstly one part of phenylboronic acids reacted with iodine to form iodobenzenes, then another part of phenylboronic acids coupled with iodobenzenes to produce biaryl compounds. The tandem reaction were catalyzed by a bifunctional heterogeneous catalyst of metal organic frameworks encapsulated with palladium nanoparticles (Pd?MOFs). This strategy for forming symmetric C-C bond between benzene rings has obvious advantages such as high efficiency, easy separation, good recyclability and no addition of toxic halogenated benzene.
- Bao, Yan-Sai,Cui, Xin-Yu,Han, Zheng-Bo,Li, Xin,Tang, Hong,Yang, Ming,Zhang, Yu-Yang,Zhao, Kun,Zhou, Mei-Li
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- Identification of a Surprising Boronic Acid Homocoupling Process in Suzuki-Miyaura Cross-Coupling Reactions Utilizing a Hindered Fluorinated Arene
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The Suzuki-Miyaura cross-coupling reaction of 2-bromo-1,3-bis(trifluoromethyl)benzene with arylboronic acids was evaluated and determined to suffer from the formation of large amounts of boronic acid homocoupling products in conjunction with dehalogenation. Homocoupling product formation in this process likely occurs through a rare protonolysis/second transmetalation event rather than by the well-established mechanism requiring the involvement of O 2. The scope of this boronic acid homocoupling reaction was investigated and shown to predominate with electron-deficient arylboronic acids. Finally, a good yield of cross-coupling products could be obtained by employing dicyclohexyl(2′,6′-dimethoxybiphenyl-2-yl)phosphine (SPhos) as the ligand.
- Gargaro, Samantha L.,Dunson, Bre'Shon,Sieber, Joshua D.
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supporting information
p. 511 - 516
(2020/09/21)
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- CuO grafted triazine functionalized covalent organic framework as an efficient catalyst for C-C homo coupling reaction
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Designing of low cost catalytic system for new C-C bond formation reactions is very challenging in synthetic organic chemistry. Herein, we report a new copper oxide immobilized covalent organic framework (COF) material CuII-TRIPTA by grafting of CuO nanoparticles at the surface of a nitrogen rich porous COF material TRIPTA. TRIPTA has been synthesized through the extended Schiff base reaction between 2,4,6-triformylphloroglucinol and 1,3,5-tris-(4-aminophenyl) triazine. The COF as well as CuO loaded materials are characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and EPR spectroscopic analyses. CuII-TRIPTA material has been successfully applied as heterogeneous nanocatalyst for the C-C homo-coupling reaction of phenylboronic acids to synthesise wide range of biaryl compounds under mild and eco-friendly conditions (60 °C, methanol solvent). Remarkably high specific surface area of CuII-TRIPTA (583 m2 g?1) and highly accessible catalytic sites in the 2D-hexagonal COF nano-architecture potentially makes it excellent catalyst in the C-C bond formation reaction, which is evident from the high TON of the catalyst in this reaction. The catalyst was recollected and reused till 6th cycles without any noticeable change of its catalytic activity, suggesting its high catalytic efficiency in this C-C bond formation reaction.
- Das, Sabuj Kanti,Krishna Chandra, Bijan,Molla, Rostam A.,Sengupta, Manideepa,Islam, Sk. Manirul,Majee, Adinath,Bhaumik, Asim
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- Efficient Pd-catalyzed oxidative homocoupling of arylboronic acids in aqueous NaClO
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An efficient, mild and practical method was developed for the synthesis of biaryls via the Pd-catalyzed oxidative homocoupling of aromatic/heteroaromatic boronic acids in aqueous NaClO.
- Li, Min-Xin,Tang, Yan-Ling,Gao, Hui,Mao, Ze-Wei
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supporting information
(2020/03/04)
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- Sulfonate Versus Sulfonate: Nickel and Palladium Multimetallic Cross-Electrophile Coupling of Aryl Triflates with Aryl Tosylates
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While phenols are frequent and convenient aryl sources in cross-coupling, typically as sulfonate esters, the direct cross-Ullmann coupling of two different sulfonate esters is unknown. We report here a general solution to this challenge catalyzed by a combination of Ni and Pd with Zn reductant and LiBr as an additive. The reaction has broad scope, as demonstrated in 33 examples (65% ± 11% average yield). Mechanistic studies show that Pd strongly prefers the aryl triflate, the Ni catalyst has a small preference for the aryl tosylate, aryl transfer between catalysts is mediated by Zn, and Pd improves yields by consuming arylzinc intermediates.
- Kang, Kai,Huang, Liangbin,Weix, Daniel J.
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supporting information
p. 10634 - 10640
(2020/07/08)
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- Chromium(II)-Catalyzed Diastereoselective and Chemoselective Csp2-Csp3 Cross-Couplings Using Organomagnesium Reagents
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A simple protocol for performing chromium-catalyzed highly diastereoselective alkylations of arylmagnesium halides with cyclohexyl iodides at ambient temperature has been developed. Furthermore, this ligand-free CrCl2 enables efficient electrophilic alkenylations of primary, secondary, and tetiary alkylmagnesium halides with readily available alkenyl acetates. Moreover, this chemoselective C-C coupling reaction with stereodefined alkenyl acetates proceeds in a stereoretentive fashion. A wide range of functional groups on alkyl iodides and alkenyl acetates are well tolerated, thus furnishing functionalized Csp2-Csp3 coupling products in good yields and high diastereoselectivity. Detailed mechanistic studies suggest that the in situ generated low-valent chromium(I) species might be the active catalyst for these Csp2-Csp3 cross-couplings.
- Li, Jie,Ren, Qianyi,Cheng, Xinyi,Karaghiosoff, Konstantin,Knochel, Paul
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p. 18127 - 18135
(2019/11/19)
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- Industrial production method of 3,3'-difluorobiphenyl
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The invention relates to a novel, safe, economical and environment-friendly production method of a useful chemical 3,3'-difluorobiphenyl. High-purity 3,3'-difluorobiphenyl can be prepared and obtained in a high-yield manner by making 3-fluorophenyl halogenated magnesium react with 1,2-dihalogenethane under the catalytic action of a trivalent ferric salt, and then treating a product by using an alkali or an acid. In addition, the method comprises a step of using and recycling an ethylene gas released in the reaction to prepare the initial raw material 1,2-dihalogenethane of the reaction, wherein the ethylene gas is a potential air pollutant.
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Paragraph 0067-0073; 0076-0078
(2017/03/25)
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- Iron-Catalyzed Isopropylation of Electron-Deficient Aryl and Heteroaryl Chlorides
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Traditional methods for the preparation of secondary alkyl-substituted aryl and heteroaryl chlorides challenge both selectivity and functional group tolerance. This contribution describes the use of statistical design of experiments to develop an effective procedure for the preparation of isopropyl-substituted (hetero)arenes with minimal isopropyl to n-propyl isomerization. The reaction tolerates electronically diverse aryl chloride coupling partners, with excellent conversion observed for strongly electron-deficient aromatic rings, such as esters and amides. Electron-rich systems, including methyl- and methoxy-substituted aryl chlorides, were found to be less reactive. Furthermore, the reaction was found to be most successful when heteroaryl chlorides were submitted to the cross-coupling protocol. By mapping substituent effects on reaction selectivity, we were able to show that electron-deficient aryl chlorides are essential for efficient coupling, and use electronic structure calculations to predict the likelihood of successful coupling through the estimation of the electron affinity of each aryl chloride. Moderate isolated yields were achieved with selected aryl chlorides, and moderate to good isolated yields were obtained for all the heteroaryl chlorides coupled. Excellent selectivity was observed when a 2,6-dichloroquinoline was used, allowing mono-substitution on a challenging substrate. (Figure presented.).
- Sanderson, James N.,Dominey, Andrew P.,Percy, Jonathan M.
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p. 1007 - 1017
(2017/03/27)
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- Powerful, Thermally Stable, One-Pot-Preparable, and Recyclable Electrophilic Trifluoromethylating Agents: 2,8-Difluoro- and 2,3,7,8-Tetrafluoro-S-(trifluoromethyl)dibenzothiophenium Salts
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Although many electrophilic trifluoromethylating agents have been reported to date, practically useful reagents have yet to be developed. S-(Trifluoromethyl)dibenzothiophenium salts, known as Umemoto's reagents, have two significant drawbacks that have ha
- Umemoto, Teruo,Zhang, Bin,Zhu, Tianhao,Zhou, Xiaocong,Zhang, Peng,Hu, Song,Li, Yuanqiang
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p. 7708 - 7719
(2017/08/14)
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- HALOGENATED S-(PERFLUOROALKYL) DIBENZOTHIOPHENIUM SALT AND ITS PRODUCTION METHODS
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Halogenated S-(perfluoroalkyl) dibenzothiophenium salt represented by the following general formula (I). This compound is a new, reactive, and industrially useful reagent for perfluoroalkylating organic compounds. The reagent can be prepared by a one-pot process or a two-step reaction process from a halogenated biphenyl and easily isolated by a filtration method. In addition, the halogenated biphenyl can be recovered by desulfurization from a halogenated dibenzothiophene obtained as a side-product by the usage of the reagent.
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Page/Page column 31-32
(2016/07/27)
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- Homocoupling reactions of terminal alkynes and arylboronic compounds catalyzed by in situ formed Al(OH)3-supported palladium nanoparticles
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Palladium nanoparticles supported on newly generated Al(OH)3was found to be a highly efficient catalyst in oxidative homo-couplings of (Het)aryl alkynes, (Het)arylboronic acids and potassium (Het)aryltrifluoroborates, respectively. Moderate to excellent yields of symmetrical 1,3-diynes and biaryls were obtained under mild conditions.
- Li, Xing,Li, Dongjun,Bai, Yana,Zhang, Congxia,Chang, Honghong,Gao, Wenchao,Wei, Wenlong
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supporting information
p. 6996 - 7002
(2016/10/14)
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- Homocoupling of heteroaryl/aryl/alkyl Grignard reagents: I2-promoted, or Ni- or Pd- or Cu- or nano-Fe-based salt catalyzed
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Five efficient processes for the homo-coupling of various Grignard reagents including aryl, heteroaryl and aliphatic ones in the presence of I2, Pd(OAc)2, Ni(OAc)2, CuI, and nano-Fe3O4 were developed, respectively.
- Li, Xing,Li, Dongjun,Li, Yingjun,Chang, Honghong,Gao, Wenchao,Wei, Wenlong
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p. 86998 - 87002
(2016/09/23)
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- Dimerization of Aryl Sulfonates by in situ Generated Nickel(0)
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A mild and user-friendly nickel-catalyzed method for the reductive homocoupling of aromatic tosylates is presented. The reaction proceeds between room temperature and 60 °C, with stable substrates (ArOTs) easily prepared from inexpensive and commercially available phenols or naphthols. It relies on a catalytic amount (10 mol%) of a robust catalyst (NiBr2bipy) that does not require the preparation of sensitive organometallic intermediates. Yields are good to excellent.
- Maddaluno, Jacques,Durandetti, Muriel
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supporting information
p. 2385 - 2388
(2015/10/19)
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- Fe3O4 nanoparticle-supported Cu(ii)-β- cyclodextrin complex as a magnetically recoverable and reusable catalyst for the synthesis of symmetrical biaryls and 1,2,3-triazoles from aryl boronic acids
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We report here on the preparation of an efficient, easily recoverable and reusable Fe3O4 magnetic nanoparticle-supported Cu(ii)-β-cyclodextrin complex catalyst for the synthesis of symmetrical biaryls and 1,2,3-triazoles from arylboronic acids. The presented Fe 3O4 magnetic nanoparticle-supported Cu(ii)-β- cyclodextrin complex catalyst was characterized by TEM, XRD, VSM, TGA, and FT-IR spectrometer. By using the catalyst, we have developed an efficient protocol for the homocoupling of aryl boronic acids for the synthesis of biaryls. The catalyst is also active in the synthesis of 1,2,3-triazoles via a one-pot reaction of an arylboronic acid with sodium azide in water followed by a click cyclization reaction with an alkyne at room temperature in air without any additives. The reusability of the prepared nanocatalyst was successfully examined four times with only a very slight loss of catalytic activity.
- Kaboudin, Babak,Mostafalu, Ramin,Yokomatsu, Tsutomu
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p. 2266 - 2274
(2013/09/24)
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- Palladium-catalyzed Suzuki-Miyaura coupling of aryl sulfamates with arylboronic acids
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Readily available NHC-Pd(ii)-Mp complexes 2 showed efficient catalytic activity toward the Suzuki-Miyaura coupling of aryl sulfamates with arylboronic acids or potassium phenyltrifluoroborate, giving the expected coupling products in good to high yields.
- Wang, Zhan-Yong,Ma, Qin-Na,Li, Ren-Hao,Shao, Li-Xiong
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p. 7899 - 7906
(2013/11/19)
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- Highly porous chitosan microspheres supported palladium catalyst for coupling reactions in organic and aqueous solutions
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Porous chitosan microspheres (PCMS) were prepared from crosslinking chitosan/polyethylene glycol (PEG) interpenetrating microspheres through selective dissolution of the water-soluble PEG component for the immobilization of palladium catalyst. The resultant Pd/PCMS supported palladium has been demonstrated as a highly active and easily recyclable heterogeneous catalyst for the Ullmann-type reductive homocoupling of aromatic halides and the Heck cross-coupling of aromatic halides with acrylates. Most interestingly, the prepared Pd/PCMS heterogeneous palladium catalyst can also be employed in the environmentally-benign aqueous solution due to the highly hydrophilic hydroxyl and amino functional groups of chitosan. The large size of the microsphere structure can greatly facilitate separation and recycling of the expensive and toxic palladium catalysts from the reaction mixture and the recovered Pd/PCMS catalyst can preserve the catalytic activity and selectivity for the Heck reaction without any observable degradation over ten recycling times. The high activity and stability of the Pd/PCMS catalyst have been attributed to a combination of the high specific surface area of the porous structure as well as the strong chelation of palladium species with the abundant chitosan surface hydroxyl, amino and carbonyl functional groups.
- Zeng, Minfeng,Zhang, Xin,Shao, Linjun,Qi, Chenze,Zhang, Xian-Man
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experimental part
p. 29 - 37
(2012/04/04)
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- Ferrous salt-promoted homocoupling of arenediazonium tetrafluoroborates under mild conditions
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A simple and efficient protocol has been developed for the synthesis of various symmetrical biaryls in good to excellent yields from the homocoupling reactions of arenediazonium salts with ferrous salt in carbon tetrachloride solution under mild reaction conditions. Moreover, the novel homocoupling has been demonstrated to proceed via an electron transfer reaction mechanism.
- Ding, Yiyuan,Song, Qingbao,Cheng, Kai,Qi, Chenze
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p. 6269 - 6272,4
(2012/12/11)
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- Fe(II)-catalysed homocoupling of arenediazonium tetrafluoroborates
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An efficient procedure for the synthesis of biaryls was catalysed by Fe(acac)2 and zinc powder in carbon tetrachloride solution at 60 °C using arenediazonium salts is reported. Symmetrical bi-aryl molecules with various substituents on the phenyl ring (methyl, trifluoromethyl, halogen, nitro, methoxyl) were synthesised in good yields in a short time under air. Zinc powder was used as reductant in the reaction to facilitate the regeneration of the iron(II) catalyst.
- Zhou, Jiatian,Yu, Shuangshuang,Cheng, Kai,Qi, Chenze
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p. 672 - 674
(2013/02/22)
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- Air-stable and catalytically active phosphinous acid transition-metal complexes
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Secondary phosphane oxides R2P(O)H are most frequently used as preligands for phosphinous acid R2POH (R = alkyl, aryl) transition-metal complexes, which are very efficient catalysts for cross-coupling reactions. To investigate the influence of electron-deficient substituents on the catalytic activity, the coordination properties of bis(trifluoromethyl)-, bis(pentafluoroethyl)-, and bis[2,4-bis(trifluoromethyl) phenyl]phosphinous acid toward catalytically relevant metals, such as palladium and platinum, are studied. The novel phosphinous acid palladium complexes reveal a high catalytic activity in Heck and Suzuki cross-coupling reactions. Because of the strong dependence of these processes on the reaction conditions, a systematic solvent and base screening with 1-bromo-3-fluorobenzene and phenyl boronic acid as model reactants is performed. The most efficient solvent/base system consists of 2-propanol and potassium phosphate, providing a full conversion and a TON of around 10 000 after 20 h at room temperature with a catalyst loading of 0.01 mol % palladium. A catalyst loading of only 0.004 mol % palladium still leads to a nearly full conversion after 20 h at room temperature. During the catalytic reaction, the formation of the corresponding phosphinic acid R2P(O)OH is observed. Further investigations lead to the conclusion that palladium nanoparticles represent the catalytically active species. We also succeeded in the generation of palladium nanoparticles, which exhibit an extremely high catalytic activity in Suzuki cross-coupling reaction with TONs over 60 000 and TOFs larger than 40 000.
- Kurscheid, Boris,Belkoura, Lhoussaine,Hoge, Berthold
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experimental part
p. 1329 - 1334
(2012/04/10)
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- An efficient and recyclable heterogeneous palladium catalyst utilizing naturally abundant pearl shell waste
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An efficient and recyclable ligand-free heterogeneous catalyst has been prepared by the immobilization of palladium onto ground pearl shell powders (Pd/shell powders, Pd/SP). The catalytic activity and recyclability of the prepared Pd/SP along with the charcoal and calcium carbonate supported palladium (Pd/C and Pd/CaCO3) catalysts have been evaluated using the reductive homocoupling of aromatic halides. Pd/SP not only has higher catalytic activity, but also exhibits much stronger stability than Pd/C and Pd/CaCO 3. The remarkable Pd/SP stability has been attributed to the chelation of palladium species with the surface chitin and protein molecules of the supported pearl shell powders. The X-ray photoelectron spectroscopy (XPS) studies show that the reductive Pd0 species can be regenerated in situ from the oxidative Pd2+ species for the Pd/SP catalyzed reductive homocoupling of aromatic halides in ethanol/DMSO solution, suggesting that the heterogeneous and homogeneous palladium catalysis proceeds through a similar Pd0/Pd2+ cycle catalytic mechanism.
- Zeng, Minfeng,Du, Yijun,Qi, Chenze,Zuo, Shufeng,Li, Xiudong,Shao, Linjun,Zhang, Xian-Man
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experimental part
p. 350 - 356
(2011/04/17)
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- CuSO4-mediated homocoupling of arylboronic acids under ligand- and base-free conditions in air
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The homocoupling of arylboronic acids mediated by very inexpensive and air stable copper(II) sulfate in N,N-dimethylformamide affords the corresponding symmetrical biaryls in moderate to good yields. The homocoupling reaction proceeds in air at 50 C in the presence of molecular sieves without any additives such as base and ligand. Georg Thieme Verlag Stuttgart · New York.
- Kaboudin, Babak,Haruki, Terumitsu,Yokomatsu, Tsutomu
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experimental part
p. 91 - 96
(2011/02/28)
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- CuII-β-cyclodextrin complex as a nanocatalyst for the homo-and cross-coupling of arylboronic acids under ligand-and base-free conditions in air: Chemoselective cross-coupling of arylboronic acids in water
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We report here the transition-metal-catalyzed chemoselective cross-coupling of arylbroronic acids in high yields without using ligand or base. We have developed an efficient copper-catalyzed protocol for the homocoupling and cross-coupling of arylboronic acids. The protocol is also suitable for the cross-coupling of aliphatic primary amines with arylboronic acids. Aminophenols and primary amines bearing an alcoholic substituent on the aliphatic chain were coupled with arylboronic acids, and the products were obtained with high C-N coupling selectivity. An effective catalyst was Cu2-β- cyclodextrin, which is readily available and structurally simple, but has not previously been explored as a catalyst.
- Kaboudin, Babak,Abedi, Yaghoub,Yokomatsu, Tsutomu
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experimental part
p. 6656 - 6662
(2012/01/06)
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- Ethanol-promoted reductive homocoupling reactions of aryl halides catalyzed by palladium on carbon (Pd/C)
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Homocoupling reactions of aryl bromides or iodides proceeded smoothlywith palladium on carbon (Pd/C) catalyst, ethanol and base in dimethyl sulfoxide (DMSO) to afford exclusively symmetric biaryls in good to excellent yields. Ethanol was first used as a reducing agent in situ to reduce the Pd 2+/C species into Pd0/C active species to complete the catalytic redox cycle. It was found that ethanol can promote the Pd/C-catalyzed reductive homocoupling of aryl iodides and bromides efficiently in the presence of base. A reaction mechanism has been put forward and discussed. Copyright
- Shao, Linjun,Du, Yijun,Zeng, Minfeng,Li, Xiudong,Shen, Wenting,Zuo, Shufeng,Lu, Yueqing,Zhang, Xian-Man,Qi, Chenze
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experimental part
p. 421 - 425
(2010/08/06)
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- A recyclable Au(I) catalyst for selective homocoupling of arylboronic acids: Significant enhancement of nano-surface binding for stability and catalytic activity
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Au nanoparticles stabilized by polystyrene-co-polymethacrylic acid microspheres (PS-co-PMAA) were prepared and characterized via X-ray diffraction (XRD), and transmission electron microscope (TEM). The Au nanoparticles supported on the microspheres showed highly selective catalytic activity for homo-coupling reactions of arylboronic acids in a system of aryl-halides and arylboronic acids. X-ray photoelectron spectroscopy (XPS) spectra of the catalyst shows large amounts of Au(l) complexes band to the surface of the Au nanoparticles, which contributes to the selective homocoupling of the arylboronic acids. More importantly, this supported Au complex is a highly recyclable catalyst. The supported Au catalyst can be recycled and reused at least 6 times for a phenylboronic acid reactant, whereas the parent complex shows very low catalytic activity for this compound. The high catalytic activity of this material is attributed to: (1) the high surface to volume ratio which leads to more active sites being exposed to reactants; (2) the strong surface binding of the Au nanoparticle to the Au(1) complexes, which enhances both the stability and the catalytic activity of these complexes. Copyright
- Zhang, Xin,Zhao, Haitao,Wang, Jianhui
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p. 5153 - 5160
(2011/12/15)
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- Palladium-catalyzed reductive homocoupling of aromatic halides and oxidation of alcohols
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Palladium-catalyzed reductive homocoupling of aromatic halides can be performed in alcohol solutions without any auxiliary reducing reagents. Pd(dppf)Cl2 [dppf = 1,1′-bis(diphenylphosphino)ferrocene] has been shown as the most effective catalyst among the palladium catalysts screened for the model reductive homocoupling of iodobenzene in alcoholic solutions. The reduction of iodobenzene is stoichiometrically coupled with the oxidation of solvent alcohol (3-pentanol). The X-ray photoelectron spectroscopic (XPS) studies clearly indicate that the oxidation of solvent alcohol molecules is involved with the in situ regeneration of the reductive Pd0(dppf) active species, indicating that the solvent alcohol also reacts as a reducing reagent for the reductive homocoupling of aromatic halides. Elimination of the external reducing reagents will simplify the product separation and purification. Base is essential for the success of the Pd(dppf)Cl 2-catalyzed redox reaction as 2 molar equiv of base is needed to neutralize the acid byproduct formed. Biaryls are the predominant products for the Pd(dppf)Cl2-catalyzed reductions of the unsubstituted aromatic halides in 3-pentanol solution, whereas the dehalogenation products are predominant for the Pd(dppf)Cl2-catalyzed reductions of the substituted aromatic halides. The reaction mechanisms have been discussed for the palladium-mediated concomitant reduction of aromatic halides and oxidation of alcohols without any auxiliary reductants and oxidants.
- Zeng, Minfeng,Du, Yijun,Shao, Linjun,Qi, Chenze,Zhang, Xian-Man
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experimental part
p. 2556 - 2563
(2010/09/11)
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- Nickel-catalyzed carbonylative Negishi cross-coupling reactions
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Catalytic carbonylative Negishi cross-coupling reactions are described. This method readily provides various enones from enol triflates and diorganozinc reagents with catalytic amounts of nickel(II) chloride-4,4′-dimethoxyl-2,2′-bipyridyl under carbon mon
- Wang, Qiaoling,Chen, Chuo
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p. 2916 - 2921
(2008/09/21)
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- Homocoupling of aryl iodides and bromides promoted by sulfur-containing palladacycles
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Sulfur-containing palladacycles, in particular those derived from the orthometalation of benzylthioethers, effectively promote the homocoupling of aryl iodides and bromides, under relatively mild reaction conditions to furnish symmetrical biphenyls in good yields.
- Silveira, Priscila B.,Lando, Vanusa R.,Dupont, Jairton,Monteiro, Adriano L.
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p. 2327 - 2329
(2007/10/03)
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- Synthesis of symmetrical triarylphosphines from aryl fluorides and red phosphorus: Scope and limitations
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The reaction of aryl fluorides with phosphide anion, generated in situ from the reduction of red phosphorus by lithium metal in liquid ammonia, gave symmetrical triarylphosphines in fair to good yields. Phosphonodiamide, sulfonamide, 2-oxazolyl, and nitrile groups were stable to the reaction conditions, while nitro and bromo substituents were not. para-Substituted aryl fluorides gave higher yields than meta-substituted aryl fluorides, and ortho-substituted aryl fluorides failed to react.
- Schull, Terence L.,Brandow, Susan L.,Dressick, Walter J.
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p. 5373 - 5376
(2007/10/03)
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- Selective synthesis of (Z)-4-aryl-5-[1-(aryl)methylidene]-3-bromo-2(5H)-furanones
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4-Aryl-3-bromo-2(5H)-furanones have been selectively synthesized in satisfactory yields by treatment of easily available 3,4-dibromo-2(5H)-furanone either with arylboronic acids in the presence of Ag2O and a catalytic amount of PdCl2(MeCN)2 or with aryl(trialkyl)stannanes in the presence of a catalyst precursor consisting of AsPh3 and a Pd(II) or a Pd(0) compound. These monobromo derivatives have been then used as precursors to a variety of (Z)-4-aryl-5-[1-(aryl)methylidene]-3-bromo-2(5H)-furanones including the compound with the structure corresponding to that reported for naturally occurring rubrolide N. The structure and stereochemistry of these synthetic compounds have been unambiguously established by NMR techniques.
- Bellina, Fabio,Anselmi, Chiara,Viel, Stéphane,Mannina, Luisa,Rossi, Renzo
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p. 9997 - 10007
(2007/10/03)
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- Selective synthesis of unsymmetrical 3,4-disubstituted and 4-substituted 2(5H)-furanones
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Easily available 3,4-dibromo-2(5H)-furanone undergoes regioselective palladium-catalyzed reaction with aryl(trialkyl)stannanes to give the corresponding 4-aryl-3-bromo-2(5H)-furanones in satisfactory yields. These monobromo derivatives have proven to be useful precursors to unsymmetrical 3,4-diaryl-2(5H)-furanones, 4-aryl-3-methyl-2(5H)-furanones and 4-aryl-2(5H)-furanones.
- Rossi,Bellina,Raugei
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p. 1749 - 1752
(2007/10/03)
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- Lithium hydride mediated nickel(0) catalysed biaryl synthesis from aryl chlorides and bromides
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Lithium hydride is efficiently used as a reducing agent in the ligated Ni0 catalysed homocoupling of aryl bromides and chlorides.
- Massicot, Fabien,Schneider, Raphael,Fort, Yves
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p. 664 - 665
(2007/10/03)
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- Homocoupling of aryl halides promoted by tetrabutylammonium fluoride
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The palladium-catalysed homocoupling of aryl halides takes place in the presence of anhydrous, in situ generated, tetrabutylammonium fluoride (TBAF).
- Albanese, Domenico,Landini, Dario,Penso, Michele,Petricci, Silvia
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p. 199 - 200
(2007/10/03)
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- Catalytic alternative of the Ullman reaction
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Symmetrical functionalized biaryls and biheterocycles could be obtained in good yield via homocoupling of aryl halides by using Pd(OAc)2 as catalyst with base and isopropanol. This alternative of the Ullmann reaction has proved to be compatible with sensitive functional groups.
- Hassan, Jwanro,Penalva, Vincent,Lavenot, Laurence,Gozzi, Christel,Lemaire, Marc
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p. 13793 - 13804
(2007/10/03)
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- Direct homocoupling of aryl halides catalyzed by palladium
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Symmetrical functionnalized biaryls are obtained in good yield via homocoupling of aryl halides, bromo or iodo ones, using the combination of Pd(OAc)2 and nBu4NBr as catalyst system.
- Penalva, Vincent,Hassan, Jwanro,Lavenot, Laurence,Gozzi, Christel,Lemaire, Marc
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p. 2559 - 2560
(2007/10/03)
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- Electroreductive coupling of organic halides in alcoholic solvents. An example: The electrosynthesis of biaryls catalysed by nickel-2,2' bipyridine complexes
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Alcohols like methanol or ethanol are suitable solvents for achieving the electrosynthesis of biaryls from aryl halides according to a procedure which involves a catalysis by nickel-2,2'-bipyridine complexes. All electrolyses were carried out at constant current in an undivided cell fitted with an iron or duralumin sacrificial anode.
- Courtois, Valerie,Barhdadi, Rachid,Troupel, Michel,Perichon, Jacques
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p. 11569 - 11576
(2007/10/03)
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- Activation of Reducing Agents. Sodium Hydride Containing Complex Reducing Agents. 31. NiCRAL's as Very Efficient Agents in Promoting Homo-Coupling of Aryl Halides
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Homo-coupling of aryl bromides and chlorides is efficiently performed with nickel-containing complex reducing agents NiCRA-bpy.In a number of cases the presence of alkali iodides improves the procedure.Yields are very high and a number of functional groups are resistant.The mechanistic and catalytic aspect of these reactions are discussed.
- Lourak, Mouhsine,Vanderesse, Regis,Fort, Yves,Caubere, Paul
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p. 4840 - 4844
(2007/10/02)
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- Activation of Reducing Agents. Sodium Hydride Containing Complex Reducing Agents. 32. NiCRAL's as Very Efficient Agents in Promoting Cross-Coupling of Aryl Halides
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Nickel-containing complex reducing agents NiCRA-bpy are shown to be the first nickel reagents able to efficiently perform cross-coupling of aryl halides.The presence of KI in the reaction medium generally improves the procedure.The mechanism and influence of the structures of the substrates are discused.
- Lourak, Mouhsine,Vanderesse, Regis,Fort, Yves,Caubere, Paul
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p. 4844 - 4848
(2007/10/02)
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