- Copper catalysed Gomberg-Bachmann-Hey reactions of arenediazonium tetrafluoroborates and heteroarenediazonium o-benzenedisulfonimides. Synthetic and mechanistic aspects
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Gomberg-Bachmann-Hey reactions were carried out in the presence of copper as a catalyst and gave rise to biaryls or heterobiaryls in good yields and in mild reaction conditions. A computational study of some key points of the reaction was performed. The results are coherent with the experimental data and confirm some aspects of the mechanism. The reaction free energies for the reduction in benzene by CuI of a set of 40 (hetero)arenediazonium tetrafluoroborates were calculated. Both the experiments and the calculations showed that in the coupling with substituted solvents (toluene, bromobenzene, nitrobenzene and anisole) the binding to the ortho position was always favoured.
- Antenucci, Achille,Barbero, Margherita,Dughera, Stefano,Ghigo, Giovanni
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- Integrating Organic Lewis Acid and Redox Catalysis: The Phenalenyl Cation in Dual Role
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In recent years, merging different types of catalysis in a single pot has drawn considerable attention and these catalytic processes have mainly relied upon metals. However, development of a completely metal free approach integrating organic redox and organic Lewis acidic property into a single system has been missing in the current literature. This study establishes that a redox active phenalenyl cation can activate one of the substrates by single electron transfer process while the same can activate the other substrate by a donor-acceptor type interaction using its Lewis acidity. This approach has successfully achieved light and metal-free catalytic C-H functionalization of unactivated arenes at ambient temperature (39 entries, including core moiety of a top-selling molecule boscalid), an economically attractive alternative to the rare metal-based multicatalysts process. A tandem approach involving trapping of reaction intermediates, spectroscopy along with density functional theory calculations unravels the dual role of phenalenyl cation.
- Ahmed, Jasimuddin,Chakraborty, Soumi,Jose, Anex,Sreejyothi,Mandal, Swadhin K.
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supporting information
p. 8330 - 8339
(2018/06/19)
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- Convenient, metal-free ipso-nitration of arylboronic acids using nitric acid and trifluoroacetic acid
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A feasible protocol for the direct ipso-nitration of arylboronic acids using trifluoroacetic acid and nitric acid as nitration reagent has been developed. Various aromatic nitro compounds are produced in moderate to good yields under the metal-free conditions. The method is operationally simple and regioselective, and might have potential application in industry.
- Shen, Guodong,Zhao, Lingyu,Liu, Wanxing,Huang, Xianqiang,Song, Huina,Zhang, Tongxin
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supporting information
p. 10 - 14
(2016/12/30)
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- Zeolite-assisted nitration of biphenyl using nitric acid
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The nitration process using 95 % nitric acid instead of the classical nitric acid-sulfuric acid system appears to be attractive and promising in the preparation of nitro compounds. The ratio of 2-nitrobiphenyl (2a) isomer to 4-nitrobiphenyl (2b) can reach 0.69 in a good yield of 78.42 %. The isomeric distribution of the product mononitrobiphenyl was found to be superior to traditional methods. Raising the ratio of 95 % nitric acid and biphenyl to 4:1, the yield of dinitration products can reach more than 78.08 %, as a mixture of 2,2-dinitrobiphenyl (3a), 2,4-dinitrobiphenyl (3b), and 4,4-dinitrobiphenyl (3c).
- Tai, Yanfang,Peng, Xinhua,Shi, Chunjie,Dong, Xiongzi
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p. 867 - 872
(2015/03/03)
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- Palladium(II)-catalyzed coupling of electron-deficient arenes via C-H activation
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Homocoupling and cross-coupling of electron-deficient arenes, including nitrobenzene, (trifluoromethyl)benzene, ethyl benzoate, etc., have been developed to afford biaryls using a catalytic system of Pd(OAc) 2/trifluoroacetic acid (TFA)/O2 or K2S 2O8. The crucial step is to tune the concentrations of arenes and the loading of TFA carefully to enhance the reaction rates and the selectivity of these couplings involving dual C-H activation.
- Zhou, Lihong,Lu, Wenjun
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scheme or table
p. 2124 - 2127
(2012/06/01)
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- Metal-free, visible-light-mediated direct C-H arylation of heteroarenes with aryl diazonium salts
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Visible light along with 1 mol % eosin Y catalyzes the direct C-H bond arylation of heteroarenes with aryl diazonium salts by a photoredox process. We have investigated the scope of the reaction for several aryl diazonium salts and heteroarenes. The general and easy procedure provides a transition-metal-free alternative for the formation of aryl-heteroaryl bonds.
- Hari, Durga Prasad,Schroll, Peter,Koenig, Burkhard
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supporting information; experimental part
p. 2958 - 2961
(2012/04/04)
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- Biaryl and aryl ketone synthesis via Pd-catalyzed decarboxylase coupling of carboxylate salts with aryl triflates
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A bimetallic catalyst system has been developed that for the first time allows the decarboxylative crosscoupling of aryl and acyl carboxylates with aryl triflates. In contrast to aryl halides, these electrophiles give rise to non-coordinating anions as byproducts, which do not interfere with the decarboxylation step that leads to the generation of the carbon nucleophilic crosscoupling partner. As a result, the scope of carboxylate substrates usable in this transformation was extended from ortho-substituted or otherwise activated derivatives to a broad range of ortho-, meta-, and para-substituted aromatic carboxylates. Two alternative protocols have been optimized, one involving heating the substrates in the presence of CuI/1,10- phenanthroline (10-15 mol %) and PdI2/phosphine (23 mol%) in NMP for 1-24 h, the other involving CuI/l,10-phenanthroline (615mol%) and PdBr2/Tol-BINAP (2 mol % ) in NMP using microwave heating for 5-10 min. While most products are accessible using standard heating, the use of microwave irradiation was found to be beneficial especially for the conversion of non-activated carboxylates with functionalized aryl triflates. The synthetic utility of the transformation is demonstrated with 48 examples showing the scope and limitations of both protocols. In mechanistic studies, the special role of microwave irradiation is elucidated, and further perspectives of decarboxylase crosscouplings are discussed.
- Goossen, Lukas J.,Linder, Christophe,Rodriguez, Nuria,Lange, Paul P.
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supporting information; experimental part
p. 9336 - 9349
(2010/04/03)
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- Synthesis of biaryls and aryl ketones via microwave-assisted decarboxylative cross-couplings
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A protocol for the microwave-assisted decarboxylative cross-couplings of carboxylic acid salts with aryl halides has been developed that allows the synthesis of various biaryls and aryl ketones in high yields. After careful adaptation of the bimetallic ca
- Goossen, Lukas J.,Linder, Bettina Zimmermanns Christophe,Rodriguez, Nuria,Lange, Paul P.,Hartung, Jens
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experimental part
p. 2667 - 2674
(2009/12/31)
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- Method For Decarboxylating C-C Cross-Linking Of Carboxylic Acids With Carbon Electrophiles
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The invention relates to a method for decarboxylating C—C bond formation by reacting carboxylic salts with carbon electrophiles in the presence of transition metal compounds as catalysts. The method represents a decarboxylating C—C bond formation of carboxylic acid salts with carbon electrophiles, wherein the catalyst contains two transition metals and/or transition metal compounds, from which one is present, preferably, in the oxidation step, which are different from each other by one unit, and catalyzes a radical decarboxylation which is absorbed during the second oxidation steps, which are different from each other by two units and catalyzes the two electron processes of a C—C bond formation reaction.
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Page/Page column 4-5
(2008/12/07)
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- Palladium/copper-catalyzed decarboxylative cross-coupling of aryl chlorides with potassium carboxylates
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(Chemical Equation Presented) Even non-activated aryl chlorides undergo decarboxylative cross-coupling reactions in the presence of a catalyst system generated in situ from CuI, 1,10-phenanthroline, PdI2, and di(tert-butyl)biphenylphosphane. The new catalyst is useful for both the synthesis of biaryl compounds from aromatic carboxylates and the synthesis of aryl ketones from salts of α-ketocarboxylic acids (see scheme; FG=functional group; R=aryl, alkyl).
- Goossen, Lukas J.,Zimmermann, Bettina,Knauber, Thomas
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experimental part
p. 7103 - 7106
(2009/04/12)
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- Biaryl synthesis via Pd-catalyzed decarboxylative coupling of aromatic carboxylates with aryl halides
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A new strategy for the regiospecific construction of unsymmetrical biaryls is presented, in which easily available salts of carboxylic acids are decarboxylated in situ to give arylmetal species that serve as the nucleophilic component in a catalytic cross-coupling reaction with aryl halides. The catalyst system consists of a copper phenanthroline complex that mediates the extrusion of CO2 from aromatic carboxylates to generate arylcopper species, and a palladium complex that catalyzes the cross-coupling of these intermediates with aryl halides. This bimetallic system allows the direct coupling of various aryl, heteroaryl, or vinyl carboxylic acids with aryl or heteroaryl iodides, bromides, or chlorides at 160°C in the presence of a mild base such as potassium carbonate. The present scope and potential economic impact of the reaction are demonstrated by the synthesis of 42 biaryls, some of which are of substantial industrial relevance. Remaining challenges and future perspectives of the new transformation are discussed.
- Goossen, Lukas J.,Rodriguez, Nuria,Melzer, Bettina,Linder, Christophe,Deng, Guojun,Levy, Laura M.
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p. 4824 - 4833
(2008/01/27)
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- Protodediazoniation of aryldiazonium fluoroborates by dimethylformamide
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The protodrdiazoniation of aryldiazonium fluoroborates can be effected by warm dimethylformamide (DMF). The conversion of 4-nitrobenzenediazonium fluoroborate to nitrobenzene was studied in detail. Products derived from trapping experiments were consistent with a homolytic process. Studies with deuterated DMF established that H atom abstraction occurred from both sites in DMF with a formyl:methyl preference of 3.5:1.0. This mechanism was consistent with bond energies and kinetic isotope effects calculated for the DMF radical cation.
- Markgraf, J. Hodge,Chang, Raymond,Cort, John R.,Durant Jr., Joseph L.,Finkelstein, Manuel,Gross, Andrew W.,Lavyne, Michael H.,Moore, W. Michael,Petersen, Raymond C.,Ross, Sidney D.
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p. 10009 - 10018
(2007/11/02)
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