- Pd(OAc)2 catalyzed homocoupling of arenediazonium salts in ionic liquids: Synthesis of symmetrical biaryls
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A facile, high yielding, and simple method for the synthesis of a library of symmetrical biaryls by homocoupling of arenediazonium salts is reported, employing catalytic amounts of Pd(OAc)2 and the readily available imidazolium ionic liquids (ILs), without oxidants, ligands, additives, or volatile solvents. Simple product isolation and recycling/reuse of the IL represent additional advantages of this method.
- Savanur, Hemantkumar M.,Kalkhambkar, Rajesh G.,Laali, Kenneth K.
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- Palladium-catalyzed synthesis of symmetrical biaryls under microwave irradiation and conventional heating
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The activity of the [Pd{C6H4(CH2N(CH 2Ph)2)}(μ-Br)]2 complex was investigated in the synthesis of symmetrical biaryls under both conventional and microwave irradiation conditions, and their results were compared. This complex is efficient, stable, and not sensitive to air or moisture and is a catalyst for the homo-coupling reaction of aryl iodides, bromides, and even chlorides. The products were produced in excellent yields in short reaction times using a catalytic amount of [Pd{C6H4(CH2N(CH 2Ph)2)(μ-Br)]2 complex in N-methylpyrolidine (NMP) at 130 °C. In comparison to conventional heating conditions, the reactions under microwave irradiation gave better yields in shorter reaction times.
- Hajipour, Abdol Reza,Rafiee, Fatemeh
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- Palladium-catalyzed reductive homocoupling of aryl sulfonates via cleavage of C─O bond at room temperature
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Palladium-catalyzed reductive homocoupling of aryl sulfonates has been successfully achieved under mild conditions. This transformation is a new method for the homocoupling reaction of aryl sulfonates at room temperature via the cleavage of C─O bonds, thus providing an alternative synthesis of symmetric biaryls. The reported reductive homocoupling reaction is tolerant of many common functional groups regardless of electron-donating or electron-withdrawing nature, making this newly developed transformation important for complementing Ullmann coupling. Experimental Section. Typical procedure for the products.
- Zhong, Shuangling,Chen, Mengxin,Liu, Ge,Sun, Chenggang,Liu, Wencong
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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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- Glucopyranoside-substituted imidazolium-based chiral ionic liquids for Pd-catalyzed homo-coupling of arylboronic acids in water
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Chiral ionic liquids (CILs) are widely used solvents and materials with prominent properties. Carbohydrate-derived imidazolium-based CILs represent a distinctive type of CILs possessing multiple chiral centers from natural chiral pool. Herein, a series of glucopyranoside-substituted imidazolium-based CILs (Glu-imi-CILs) were synthesized and evaluated as ligands for Pd-catalyzed homo-coupling reactions of arylboronic acids in water. The glucopyranoside substituent was instrumental for improving the catalytic activity of the resulting catalysts. Moreover, a Glu-imi-CIL with a free hydroxyl group for additional coordination was found to be the most efficient ligand. A series of symmetric biaryl compounds (13 examples) were synthesized from arylboronic acids by this method in high isolated yields (85?99percent).
- Huang, Zhiqiang,Kong, Lingfang,Li, Jing,Wu, Yue,Xue, Jun,Yuan, Yangyang,Zhou, Zhonggao
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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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- Exploring the coordination confinement effect of divalent palladium/zero palladium doped polyaniline-networking: As an excellent-performance nanocomposite catalyst for C-C coupling reactions
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A pre-formed catalyst Pd2+/PANI composite for C-C coupling reaction was synthesized by combining the self-stabilized dispersion polymerization method with the in-situ composite material. Experiments have confirmed that the relatively high reduced structure (75%) in the polyaniline carrier is more favorable for the coupling reaction. Raman spectroscopy, solid nuclear magnetic, and X-ray photoelectron spectroscopy were performed to characterize the structures. The pre-formed catalyst has uniform coordination of divalent palladium and nitrogen in different valence states of the carrier polyaniline, which shows a good synergistic effect in the catalytic Ullmann reaction, and greatly reduces the use of reducing agents such as hydrazine hydrate. Compared with other studies, we analyzed the catalytic reaction mechanism in detail through real-time online infrared and XPS characterization. The results show that the divalent palladium in the catalyst and the zero-valent palladium generated by the in-situ reaction synergistically promote the reaction, while the polyaniline support acts as a stabilizer and dispersant, which prevents the agglomeration of the metal particles and prolongs increased catalyst life. The prepared Pd2+/PANI composites will become the most attractive alternative to traditional organic materials due to their wide applicability, high catalytic activity, stable recycling and relatively low price. This work provides a new theoretical basis for the understanding of the essential driving force of PANI catalytic activity and the cognition of the micro mechanism of action.
- Liang, Yanping,Liu, Wanyi,Song, Manrong,Sun, Yanyan,Wang, Gang,Wu, Zhiqiang,Zhan, Haijuan
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- Sustainable Synthesis of Biaryls Using Silica Supported Ferrocene Appended N-Heterocyclic Carbene-Palladium Complex
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Abstract: A novel silica supported ferrocene appended N-heterocyclic carbene-palladium complex (SilFemBenzNHC@Pd) has been prepared and characterized by using fourier transform infrared (FT-IR), fourier transform Raman (FT-Raman), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and energy dispersive X-ray analysis (EDX). This novel complex served as a robust heterogeneous catalyst for the synthesis of biaryls via homocoupling of aryl boronic acids under base-free conditions in water. Recyclability experiments were executed successfully for six successive runs. Graphic Abstract: [Figure not available: see fulltext.]
- Khanapure, Sharanabasappa,Pore, Dattaprasad,Jagadale, Megha,Patil, Vaishali,Rashinkar, Gajanan
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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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- A green protocol for the Pd catalyzed ligand free homocoupling reaction of arylboronic acids under ambient conditions
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A simple, competent, green pathway has been developed for the Pd catalyzed ligand free homocoupling reaction of arylboronic acids in water under ambient conditions. An efficient reaction environment is generated using a combination of Pd(OAc)2and 'green additives', which exhibited excellent activity and results in high yields of the desired coupled products within 15 minutes. This journal is
- Dwivedi, Seema,Bardhan, Soumik,Ghosh, Prasanjit,Das, Sajal
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- Influence of chlorine substituent positions on the molecular structure and the torsional potentials of dichlorinated biphenyls: R2PI spectra of the first singlet transition and AM1 calculations
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Resonance enhanced two-photon ionization (R2PI) spectra of biphenyl and four dichlorinated biphenyl derivatives (2,6-, 2,2'-, 4,4'- and 2,4'-dichlorobiphenyl) cooled in a supersonic jet expansion have been measured in the region of the S1 0 transition (34500-36900 cm-1).The biphenyl derivatives show different torsional angles between the two phenyl rings.The degree of torsion depends on the positions of the substituents due to differing steric and electronic effects on the biaryl chromophore.Furthermore the dihedral angle changes upon electronic excitation.Therefore the electronic spectra of all investigated compounds show a vibronic substructure, dominated by Franck-Condon induced progressions of the torsional mode.Nevertheless the four dichlorobiphenyl spectra differ both in energetic locations and vibronic structure.The molecular structures and torsional potentials have been studied by molecular orbital calculations using the AM1 method.The complex structure of the R2PI spectra has been interpreted with the help of these calculations.In addition, the use of R2PI as an analytical tool is demonstrated.R2PI of jet-cooled aromatic molecules provides the possibility of species and isomer selective ionization from a complex mixture.In the case of polychlorinated biphenyls (PCBs) an isomer selective registration of the important toxic (coplanar) PCBs should be possible.
- Zimmermann, R.,Weickhardt, C.,Boesl, U.,Schlag, E. W.
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- Palladacycles promote the base-free homocoupling of arylboronic acids in air at room temperature
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Homocoupling of arylboronic acids can be successfully achieved in commercial grade THF using [Pd(Phbz)(X)(PPh3)] palladacycles as catalysts (Phbz = N-phenylbenzaldimine; X = imidate or acetate). Symmetric biaryls were obtained in good yields working under mild conditions in an air atmosphere at room temperature. The reaction occurs without the addition of an exogenous base. The reaction conditions were optimized to provide the homocoupled products in excellent yield. Evidence for the transmetallation step being important for precatalyst activation has been gathered. The influence of electronic properties of the arylboronic acids on the outcome of the homocoupling reaction has been assessed through competition experiments. This journal is
- Kapdi, Anant R.,Dhangar, Gopal,Serrano, Jose Luis,De Haro, Jose A.,Lozano, Pedro,Fairlamb, Ian J. S.
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- Pd-catalyzed oxidative homocoupling of arylboronic acids in WEPA: A sustainable access to symmetrical biaryls under added base and ligand-free ambient conditions
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Symmetrical and unsymmetrical biaryls comprises a diverse class of biologically eloquent organic compounds. We herein report, a quick and eco-friendly protocol for the synthesis of biaryls by an oxidative (aerobic) homocoupling of arylboronic acids (ABAs) using Pd(OAc)2 in water extract of pomogranate ash (WEPA) as an efficient agro-waste(bio)-derived aqueous (basic) media. The reactions were executed at ambient aerobic conditions in the absence of external base and ligand to result symmetrical biaryls in excellent yields. The use of renewable media with an effective exploitation of waste, short reaction times, excellent yields of products, easy separation of the products, unnecessating the external base, oxidant, ligand or volatile organic solvents and ambient reaction conditions are the vital insights of the present protocol.
- Appa, Rama Moorthy,Lakshmidevi, Jangam,Naidu, Bandameeda Ramesh,Venkateswarlu, Katta
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- A site-selective and stereospecific cascade Suzuki-Miyaura annulation of alkyl 1,2-bisboronic esters and 2,2′-dihalo 1,1′-biaryls
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A cascade Suzuki-Miyaura cross-coupling giving rise to 9,10-dihydrophenanthrenes has been developed. Using biaryls with unsymmetrical substitution-pattern full site-selectivity was observed. Furthermore, this cross-coupling of an alkyl 1,2-bisboronic pinacol ester proceeds through the challenging coupling of a secondary boronate with complete stereoretention.
- Willems, Suzanne,Toupalas, Georgios,Reisenbauer, Julia C.,Morandi, Bill
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supporting information
p. 3909 - 3912
(2021/04/26)
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- Palladium/Sensory Component-Catalyzed Homocoupling Reactions of Aryl Halides
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A novel and efficient catalyst system was developed for homocoupling reactions of aryl halides. The catalyst system consists of Pd(OAc) 2and the peppery sensory component of tobacco leaves. This is the first time that a sensory component has been used in an organic reaction. Experiments using the catalyst system showed that the reactions proceeded smoothly under air in the absence of both an additional ligand and a reductant. Furthermore, the catalyst system can be applied to the coupling reactions of hetaryl iodides. Many functional groups (including a hydroxy group) are tolerated.
- Bai, Haixin,Bao, Fengyu,Chai, Guobi,Liu, Pengfei,Liu, Zhikai,Zhang, Haiyan,Zhang, Qidong
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supporting information
(2020/09/09)
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- Method for preparing 2,2'-dichlorobiphenyl
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The invention provides a preparation method of 2,2'-dichlorobiphenyl. The preparation method comprises the following steps: under the catalytic action of an N-heterocyclic carbene coordinated palladium complex containing a carbohydrate unit, carrying out cross coupling reaction on 2-bromochlorobenzene and 2-chlorophenylboronic acid to generate 2,2'-dichlorobiphenyl. The method is characterized inthat an N-heterocyclic carbene coordinated palladium complex containing an alpha-D-altropyranose unit, a beta-D-altropyranose unit, an alpha-D-idopyranose unit or a beta-D-idopyranose carbohydrate unit is used as a catalyst, wherein an imidazolyl nitrogen atom of the N-heterocyclic carbene coordinated palladium complex is connected to the 2-position or 3-position of a pyranoid ring.
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Paragraph 0014-0015
(2020/05/05)
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- Desulfurization of Diaryl(heteroaryl) Sulfoxides with Benzyne
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Two benzyne-enabled desulfurization reactions have been demonstrated which convert diaryl sulfoxides and heteroaryl sulfoxides to biaryls and desulfurized heteroarenes, respectively. The reaction accessing biaryls tolerates a variety of functional groups, such as halides, pseudohalides, and carbonyls. Mechanistic studies reveal that both reactions proceed via a common assembly process but divergent disassemblies of the generated tetraaryl(heteroaryl) sulfuranes.
- Chen, De-Li,Sun, Yan,Chen, Mengyuan,Li, Xiaojin,Zhang, Lei,Huang, Xin,Bai, Yihui,Luo, Fang,Peng, Bo
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supporting information
(2019/06/13)
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- Synthesis of substituted biaryls via Suzuki, Stille and Hiyama cross-coupling and homo-coupling reactions by CN-dimeric and monomeric ortho-palladated catalysts
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The catalytic activity of dimeric [Pd{C6H2(CH 2CH2NH2)-(OMe)2,2,3}(μ-Br)] 2 and monomeric [Pd{C6H2(CH2CH 2NH2)-(OMe)2,2,3}Br(PPh3)] complexes as efficient, stable and air- and moisture-tolerant catalysts was investigated in the Suzuki, Stille and Hiyama cross-coupling and homo-coupling reactions of various aryl halides. Substituted biaryls were produced in excellent yields in short reaction times using catalytic amounts of these complexes. The monomeric complex was demonstrated to be more active than the corresponding dimeric catalyst for the cross-coupling reaction of unreactive aryl bromides and chlorides. The combination of homogeneous metal catalysts and microwave irradiation gave higher yields of products in shorter reaction times. Copyright
- Hajipour, Abdol R.,Rafiee, Fatemeh
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p. 412 - 418
(2013/07/26)
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- Reductive Ullmann coupling of aryl halides by palladium nanoparticles supported on cellulose, a recoverable heterogeneous catalyst
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Palladium nanoparticles supported on cellulose were prepared without using any reducing agent and used as a highly efficient catalyst for the Ullmann reductive coupling of aryl halides in the presence of zinc, in a water-alcohol mixture as solvent in air. The obtained palladium nanoparticles were characterized by scanning electron microscopy (SEM), FTIR, thermogravimetric analysis (TGA) and ICP-AES analysis. The synthesis of biaryls from chloroarenes was performed by this catalyst with good yield. The catalyst remains stable up to 75 °C and can be recovered and reused several times without loss of activity.
- Rasouli, Mohammad Ali,Ranjbar, Parviz Rashidi
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p. 946 - 950
(2013/09/23)
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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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- Coupling reactions of aromatic halides with palladium catalyst immobilized on poly(vinyl alcohol) nanofiber mats
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Nanoporous poly(vinyl alcohol) (PVA) nanofiber mats prepared by means of electrospinning have been used for the immobilization of palladium catalyst. Thermal treatment of the palladium-loaded PVA nanofiber mats results in the cross-linking of the matrix PVA molecules as well as the reduction of the divalent palladium (Pd2+) into zerovalent palladium (Pd0) species. The palladium oxidation states were examined by X-ray photoelectron spectroscopic (XPS) analysis. The PVA nanofiber morphology was characterized by scanning electron microscopy (SEM). The catalytic activity and recyclability of the prepared heterogeneous palladium catalysts have been evaluated for the Ullmann, Heck-Mizoroki and Sonogashira coupling reactions of aromatic halides. The large structure of the Pd/PVA nanofiber mats can greatly facilitate its separation and recycling, and the high catalytic activity and stability of the prepared Pd/PVA nanofiber mats have been attributed to the chelation of palladium species with the abundant hydroxyl functional groups on the PVA matrix surface area.
- Shao, Linjun,Ji, Weixin,Dong, Pengdu,Zeng, Minfeng,Qi, Chenze,Zhang, Xian-Man
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experimental part
p. 267 - 272
(2012/03/26)
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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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- 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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- Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: A non-product specific route to C-8 substituted analogues
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Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO4 oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.
- Berezin, Andrey A.,Koutentis, Panayiotis A.
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experimental part
p. 4069 - 4078
(2011/06/24)
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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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- 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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- Homocoupling of arylboronic acids catalyzed by 1,10-phenanthroline-ligated copper complexes in air
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The efficient homocoupling of arylboronic acids was achieved by using the catalytic combination of inexpensive copper salts and 1,10-phenanthroline as aligand. The homocoupling reaction proceeds at ambient temperature in air without any additives such as base or oxidant. This method tolerates various substituents on the arylboronic acids such as halogens, carbonyls, and a nitro group. As a result, 25 symmetrical biaryls were obtained from readily available arylboronic acids in 19-92% isolated yields. A binuclear (μ- hydroxido)copper complex is assumed as the catalytically active species, which undergoes efficient transmetalation with arylboronic acids to produce dinuclear arylcopper complexes. The binuclear structure is assumed to be essential for the bimetallic reductive elimination of biaryls as well as the oxidative restoration of the catalyst. Wiley-VCH Verlag GmbH & Co, KGaA.
- Kirai, Naohiro,Yamamoto, Yoshihiko
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experimental part
p. 1864 - 1867
(2009/08/17)
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- Copper(I)-catalysed homo-coupling of aryldiazonium salts: synthesis of symmetrical biaryls
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Copper(I) triflate acts as an efficient stoichiometric reagent for the homo-coupling of aryldiazonium salts bearing electron-withdrawing group(s), to yield symmetrical biaryls in acetonitrile under mild reaction conditions. Aryldiazonium salts bearing electron-donating groups undergo the reaction by using catalytic amounts of a copper complex prepared in situ from copper(II) triflate and 2,2′-bipyridine with metallic copper as an ultimate reductant.
- Cepanec, Ivica,Litvi?, Mladen,Udikovi?, Josipa,Pogoreli?, Ivan,Lovri?, Marija
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p. 5614 - 5621
(2007/12/29)
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- Synthesis of 2-nitro- and 2,2′-dinitrobiphenyls by means of the suzuki cross-coupling reaction
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Mechanistic investigations and protocols for the synthesis of 2-nitrobiphenyls and 2,2′-dinitrobiphenyls are disclosed. It is revealed that obstacles appear during the transmetalation step when the phenylboronic acid is substituted with a nitro group in the 2-position, whereas when substituted in the 3- or 4-positions, the reaction follows similar patterns as found in the electrophilic substitution of nitrobenzenes, an observation that may be attributed to the elimination step of the catalytic cycle.
- Gonzalez, Raquel Rodriguez,Liguori, Lucia,Carrillo, Alberto Martinez,Bjorsvik, Hans-Rene
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p. 9591 - 9594
(2007/10/03)
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- Coupling reaction of aryl halides promoted by NiCl2/PPh3/Sm0
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An efficient synthesis of biaryls from various aryl halides has been developed and investigated. The coupling reagent is a catalytic mixture of anhydrous NiCl2 and PPh3 in the presence of metallic samarium. The reaction occurs rapidly under mild conditions, tolerates a variety of functional groups with high yields.
- Zheng, Xingliang,Zhang, Yongmin
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p. 562 - 563
(2007/10/03)
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- Palladium-catalyzed synthesis of biaryls from arylzinc compounds using N-chlorosuccinimide or oxygen as an oxidant
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In the presence of a catalytic amount of Pd2+ or Pd0, oxidative homo-coupling of arylzinc compounds was achieved by the use of N-chlorosuccinimide (NCS) or O2 as an oxidant. Different reaction pathways were involved in the catalytic reactions depending on the oxidants; NCS or O2 probably oxidized I- or Pd0 to I+ or Pd2+, respectively. This reaction disclosed a new and facile synthetic method of biaryls from aryl halides or arenes via arylzinc intermediates.
- Hossain, Kabir M.,Kameyama, Toru,Shibata, Takanori,Takagi, Kentaro
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p. 2415 - 2420
(2007/10/03)
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- Relative resistance of positional isomers of polychlorinated biphenyls toward reductive dechlorination by zerovalent iron in subcritical water
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Relative resistance of positional isomers within the same homologue of polychlorinated biphenyls (PCBs) was studied by comparing the reduction efficiencies (REs) of these isomers by 100-mesh zerovalent iron in subcritical water at 250 °C and 10 MPa. The REs for meta and para isomers were found to be significantly higher than that of the ortho's. These results revealed that variation in relative resistance of the positional isomers to reductive dechlorination does exist, and the order increases from para to meta to ortho substituents. This variation in relative resistance to reduction is correlated with the lowest unoccupied molecular orbital (LUMO) energy of individual PCB congeners. A model based on the empirical relative resistance of the PCBs to reductive dechlorination is developed, and an equation is established to predict the efficiency of a reductive dechlorination system that employs zerovalent iron and pressurized hot water. Relative resistance of positional isomers within the same homologue of polychlorinated biphenyls (PCBs) was studied by comparing the reduction efficiencies (REs) of these isomers by 100-mesh zerovalent iron in subcritical water at 250°C and 10 MPa. The REs for meta and para isomers were found to be significantly higher than that of the ortho's. These results revealed that variation in relative resistance of the positional isomers to reductive dechlorination does exist, and the order increases from para to meta to ortho substituents. This variation in relative resistance to reduction is correlated with the lowest unoccupied molecular orbital (LUMO) energy of individual PCB congeners. A model based on the empirical relative resistance of the PCBs to reductive dechlorination is developed, and an equation is established to predict the efficiency of a reductive dechlorination system that employs zerovalent iron and pressurized hot water.
- Yak, Hwa K.,Lang, Qingyong,Wai, Chien M.
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p. 2792 - 2798
(2007/10/03)
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- A new synthetic method to biaryls from arylzinc iodides using N-chloro-succinimide and a catalytic amount of palladium
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Homo-coupling reactions of aryl- or alkynylzinc iodides were achieved by the use of N-chlorosuccinimide as an oxidant of zinc compounds in the presence of a catalytic amount of Pd.
- Hossain,Shibata,Takagi
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p. 1137 - 1138
(2007/10/03)
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- Nickel- and Palladium-Catalyzed Homocoupling of Aryl Triflates. Scope, Limitation, and Mechanistic Aspects
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Whereas the direct reduction of aryl triflates affords mainly phenols and some arenes, the presence of a catalytic amount of palladium or nickel results in the formation of biaryls. The homocoupling is performed in the presence of an electron source, either a cathode or zinc powder. A judicious choice of the metal (nickel or palladium), the ligand (monodentate or bidentate phosphine), and the reduction process (electrochemical or chemical) allows the synthesis of functional symmetrical biaryls. Nickel and palladium complexes ligated by bidentate ligands such as NiCl2(dppf) and Pd(OAc)2 + 1 BINAP are very efficient for the homocoupling of 1-naphthyl triflate, since the dimer was obtained in almost quantitative yield. However, the homocoupling is sensitive to steric hindrance, excluding for the moment the synthesis of atropisomers. The homocoupling proceeds via an activation of the C - O bond of the aryl triflate by a palladium(0) (or a nickel(0)) complex, providing an intermediate arylpalladium(II) (or nickel(II)) complex that after activation by electron transfer affords a new complex able to undergo a second oxidative addition with the aryl triflates.
- Jutand, Anny,Mosleh, Adil
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p. 261 - 274
(2007/10/03)
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- Carbonylative coupling of iodobenzene to benzophenone with [n-Bu4N][HFe(CO)4]
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The reaction of Bu4N+[HFe(CO)4]- with iodobenzene in a biphasic medium (aqueous NaOH/benzene) under carbon monoxide (1 atm) affords benzophenone in 85% yield. Mechanistic investigations indicate that the reaction first involves an SET from [HFe(CO)4]- to Phi. Evidence for the generation of phenyl radicals and [(PhCO)Fe(CO)4]- species is presented. Separate experiments show that [(PhCO)Fe(CO)4]- does not react with Phi, but does with phenyl radicals, generated from Phi and Smh, leading to benzophenone. Eisevier,.
- Brunet, Jean-Jacques
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- Physical, spectral and chromatographic properties of all 209 individual PCB congeners
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Through the use of two capillary GC columns: 40% octadecyl/ 15% phenyl methyl siloxane and 50% phenyl methyl siloxane, it was possible to separate 201 PCB congeners with only four unresolved pairs. The data compiled in this study for all 209 congeners will aid in the identification of selected individual components of these environmental pollutants. The use of this data also presents the opportunity for the improved quantification of the commercial PCB formulations. -from Authors
- Bolgar,et al.
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p. 2687 - 2705
(2007/10/03)
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- Palladium Catalysed Electrosynthesis using Aryl Trifluoromethanesulfonates (Triflates). Synthesis of Biaryls and Aromatic Carboxylic Acids
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The palladium(II) complex catalyses the electrosynthesis of biaryls from aryl triflates whereas, in the presence of carbon dioxide, this complex catalyses the electrosynthesis of aromatic carboxylic acids.
- Jutand, Anny,Negri, Serge,Mosleh, Adil
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p. 1729 - 1730
(2007/10/02)
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- Studies of the antenna effect in polymer molecules. 23. Photosensitized dechlorination of 2,2′,3,3′,6,6′-hexachlorobiphenyl solubilized in an aqueous solution of poly(sodium styrenesulfonate-co-2-vinylnaphthalene)
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Photodechlorination of 2,2′,3,3′,6,6′-hexachlorobiphenyl (HCB) solubilized in an aqueous solution of poly(sodium styrenesulfonate-co-2-vinylnaphthalene) (PSSS-VN) was studied with use of solar-simulated radiation. The reaction was found to be photosensitized by the naphthalene antenna units present in the copolymer. Studies performed in a low molecular weight model system have shown that dechlorination of HCB may occur via an exciplex intermediate. Exciplex formation in the system is efficient because of the high local concentration of HCB in proximity to the naphthalene polymeric units.
- Nowakowska,Sustar,Guillet
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p. 253 - 258
(2007/10/02)
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- Homocoupling of aryl halides using Nickel(II) complex and zinc in the presence of Et4NI. An efficient method for the synthesis of biaryls and bipyridines
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Reduction of NiX2(PPh3)2 with zinc in the presence of Et4NI gives a nickel catalyst which has been proven to be useful for the coupling of aryl halides. This nickel catalyst can be prepared in THF without an additional triphenylphosphine and is effective for the homocoupling of aryl chlorides, bromides, and iodides to produce biaryls and bipyridines in good yields. The reported new approach provides a simple access to novel derivatives of biaryls and bipyridines.
- Iyoda,Otsuka,Sato,Nisato,Oda
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- Reductive dehalogenation of halogen compounds
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Aliphatic, cycloaliphatic, aromatic or araliphatic halogen compounds are reductively dehalogenated by reaction with hydrocarbons in the presence of carbon in the liquid phase at from 100° to 450° C. with formation of hydrogen halides.
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- Vapour-phase Chemistry of Arenes. Part 13. Reactivity and Selectivity in the Gas-phase Reactions of Hydroxyl Radicals with Monosubstituted Benzenes at 563 K
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The reactions of hydroxyl radicals with benzene derivates C6H5Z (Z = H, Me, F, Cl, Br, I, CF3, or CN) have been studied in a flow reactor at 563 K in nitrogen, using the thermolysis of ButOOH as a source of .OH.Under these conditions there are two product-forming pathways.The major one involves hydrogen abstraction to give aryl radicals ZC6H4. (II) as the first step; depending on Z, its displacement to form phenol may also occur.Relative rates for hydrogen abstraction were determined in competition experiments using side-chain hydrogen abstraction from added toluene as a reference.This resulted in the order (for Z =): 1,8(Me), 1.0(H), 0.47(F), 0.29(Cl), 0.34(CF3), 0.20(CN), consonant with the electrophilic nature of .OH.The site selectivity of hydrogen abstractions was determined by scavenging part of the aryl radicals (II) with iodine.A Hammett plot, using ? constants for meta and para positions, led to ρ -1.0.The features of hydrogen abstraction by .OH are discussed and compared with those for the analogous reaction of Cl.The formation of phenol was found to decrease in importance in the order F, Cl, Br, and I.This result is rationalized on a thermochemical kinetic basis.
- Mulder, Peter,Louw, Robert
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p. 1167 - 1174
(2007/10/02)
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- Gas-phase thermolysis of tert-butyl hydroperoxide with benzene and chlorobenzene in the temperature range 200-300 deg C
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Thermolysis of tert-butyl hydroperoxide (1) in nitrogen with an excess of benzene in the temperature range 200-300 deg C, leads to biphenyl (2) as the only observable benzene-derived product.With chlorobenzene, dichlorobiphenyls (4) are formed, together with chlorobiphenyl (5), ca. 12percent on 4, and phenol (20-25percent on 4); chlorophenols are not produced.The use of ca. equimolar quantities of iodine based on 1 results in formation of iodobenzene (3) and chloroiodobenzenes (7), respectively, at the expense of biaryl.In air, chlorobenzene and 1 produce chlorophenols (8), biaryl then being a minor product.Hydroxyl radicals produced from 1 abstract hydrogen from benzene to give phenyl radicals (Ph.) which, in notrogen, arylate benzene.From isomer distributions of 7 and of 4 it is inferred that hydrogen abstraction from chlorobenzene leads to chlorophenyl radicals, with a ratio o/m/p ca. 24/52/24.With chlorobenzene, ipso substitution, PhCl + .OH -> PhOH, also takes place.In the presence of oxygen or iodine, formation of biaryls involves irreversible addition of (chloro)phenyl radical, the intermediate adduct radicals reacting with oxygen or iodine.In nitrogen, however, the first step in arylation is reversible.Apart from undergoing O-O bond homolysis, 1 is attacked by .Me (formed from Me3CO.) and, to some extent, by aryl radicals.A large arene/1 intake ratio (>100), or the addition of either iodine or air suppresses - or even prevents - free-radical-induced decomposition of 1.
- Mulder, Peter,Louw, Robert
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p. 282 - 287
(2007/10/02)
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- PALLADIUM(II)-CATALYZED OXIDATIVE COUPLING OF ARENES BY THALLIUM(III)
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Oxidation of benzenes with electron-donating and moderate electron-withdrawing substituents by thallium(III) trifluoroacetate in the presence of catalytic amounts of palladium(II) acetate affords biaryls in good yields.The GLC study of the isomer distribution has shown that 4,4'-biaryls are the major products.Thus, the 4,4'-biaryls can be easily isolated either by recrystallization or column chromatography.The competitive experiments and kinetic study using arenes and arylthallium derivatives as starting materials as well as quenching experiments have demonstrated the first step of the reaction to be fast thallation of arene to form arylthallium intermediate ArTl(OOCCF3)2.The latter undergoes the rate-determining transmetallation step reacting with monomeric complex Pd(OAc)2, which is formed upon depolymerization of trimer Pd3(OAc)6.Subsequent fast decomposition of arylpalladium species gives the final reaction products.The thallation of arene and substitution of TlIII for PdII in ArTl(OOCCF3)2 are characterized by the slopes of Hammet plots of -5.6 (?+) and -3.0 (?), respectively.
- Yatsimirsky, Anatoly K.,Deiko, Sergei A.,Ryabov, Alexander D.
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p. 2381 - 2392
(2007/10/02)
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- The in Situ-generated Nickel(0)-catalyzed Reaction of Aryl Halides with Potassium Iodide and Zinc Powder
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The in situ-generated nickel(0) species, presumably atomic nickel, from nickel(II) salt and zinc powder has been proved to be an effective catalyst for the Finkelstein-type displacement reaction of aryl bromides with potassium iodide to give aryl iodides under mild conditions.This species was also effective for the Ullmann-type coupling of bromides or aryl iodides by the use of zinc powder to give biaryls.Furthermore, in the presence of excess nickel(II) salt, the coupling reaction proceeded smoothly, even at an ambient temperature, to give various biaryls in very good yields.
- Takagi, Kentaro,Hayama, Naomi,Inokawa, Saburo
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p. 3691 - 3695
(2007/10/02)
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- Synthesis of C 14 labeled environment contaminants
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Upon the reaction of benzene-14C via nitrobenzene-14C and aniline-14C, some 14C-labelled environmental contaminants were were synthesized. By chlorination of aniline-14C and acetanilide-14C the authors prepared chloroanilines-14C. Gomberg-Bachmann or Cadogan reaction of diazotated chloroanilines-14C with different chlorobenzenes gave di, tri- and pentachlorobiphenyls-14C. By boiling anilinediazonium sulfate-14C the authors prepared phenol-14C, which was chlorinated to give 2,4,6-trichlorophenol-14C. Hexachlorobenzene-14C and pentachloronitrobenzene-14C were prepared by chlorination of nitrobenzene- 14C. Chloralkylene 9-14C was synthesized by Friedel-Crafts alkylation of 2,4'-dichlorobiphenyl-14C with 2-chloropropane.
- Sandrock,Attar,Bieniek,et al.
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p. 197 - 204,199,200
(2007/10/16)
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