- Sulfur contamination due to quenching of halogenation reactions with sodium thiosulfate: Resolution of process problems via improved quench protocols
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Many metal-mediated cross-couplings involve the use of organic halides, which are usually accessed by halogenation reactions. Cross-couplings are sensitive to the presence of impurities in the halides. This paper describes the origin of one such problematic impurity (sulfur) during the synthesis of organic halides and proposes alternatives to minimize or eliminate its formation.
- Xiang, Yanqiao,Caron, Pierre-Yves,Lillie, Brett M.,Vaidyanathan, Rajappa
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Read Online
- Photochemically Activated Dimagnesium(I) Compounds: Reagents for the Reduction and Selective C?H Bond Activation of Inert Arenes
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The photochemical activation of dimagnesium(I) compounds, and subsequent high yielding, regioselective reactions with inert arenes are reported. Irradiating benzene solutions of [{(ArNacnac)Mg}2] (ArNacnac=[HC(MeCNAr)2]?; Ar=2,6-diisopropylphenyl (Dip) or 2,4,6-tricyclohexylphenyl (TCHP)) with blue or UV light, leads to double reduction of benzene and formation of the “Birch-like” cyclohexadienediyl bridged compounds, [{(ArNacnac)Mg}2(μ-C6H6)]. Irradiation of [{(DipNacnac)Mg}2] in toluene, and each of the three isomers of xylene, promoted completely regio- and chemo-selective C?H bond activations, and formation of [(DipNacnac)Mg(Ar′)] (Ar′=meta-tolyl; 2,3-, 3,5- or 2,5-dimethylphenyl), and [{(DipNacnac)Mg(μ-H)}2]. Fluorobenzene was cleanly defluorinated by photoactivated [{(DipNacnac)Mg}2], leading to biphenyl and [{(DipNacnac)Mg(μ-F)}2]. Computational studies suggest all reactions proceed via photochemically generated magnesium(I) radicals, which reduce the arene substrate, before C?H or C?F bond activation processes occur.
- Jones, Dafydd D. L.,Douair, Iskander,Maron, Laurent,Jones, Cameron
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p. 7087 - 7092
(2021/03/01)
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- Visible-Light-Induced Decarboxylative Iodination of Aromatic Carboxylic Acids
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A convenient, efficient and practical visible-light-induced decarboxylative iodination of aromatic carboxylic acids has been developed, and the corresponding aryl iodides were obtained in good yields. The method shows some advantages including the use of readily available aromatic carboxylic acids as the starting materials, simple and mild conditions, high efficiency, wide substrate scope and tolerance of various functional groups.
- Jiang, Min,Yang, Haijun,Jin, Yunhe,Ou, Lunyu,Fu, Hua
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supporting information
p. 1572 - 1577
(2018/06/26)
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- Copper-catalysed aromatic-Finkelstein reactions with amine-based ligand systems
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A new efficient and low-cost ligand, diethylenetriamine, has been utilised to promote the iodination of 16 different bromo-substrates via the copper catalysed Finkelstein halogen exchange reaction under mild conditions. In contrast to earlier methods, the use of inert atmosphere conditions was not required to obtain high yields and purity. Studies on the speciation of the catalyst in solution indicate rapid disproportionation of copper(i) in the presence of diethylenetriamine to give copper(0) and a bis-ligated copper(ii) complex which is characterised by X-ray diffraction. This copper(ii) complex was also shown to be catalytically active in the halogen exchange reaction. In contrast, no significant disproportionation was observed using dimethylethylenediamine as the ligand, and the solid-state structures of a copper(i) dimeric complex and a 2D polymeric network of copper(i) iodide tetramers are reported. The catalytic activity of diethylenetriamine and dimethylethylenediamine with both copper(i) and copper(ii) salts are compared, and possible mechanistic implications discussed.
- Jin, Xiaodong,Davies, Robert P.
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p. 2110 - 2117
(2017/07/22)
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- Easy Access to Difluoromethylene-Containing Arene Analogues through Palladium-Catalysed C–H Olefination
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An efficient palladium-catalysed ortho-C–H olefination of α,α-difluorophenylacetic acid derivatives using 8-aminoquinoline as a bidentate directing group has been developed. A range of olefinated arenes can thus be synthesized in a concise way. This reaction provides an easy and straightforward route to a panel of difluoromethylated arene analogues in moderate to good yields, with a satisfactory tolerance of common functional groups. Transformation of the products into a variety of other difluoromethylene-containing compounds demonstrates the utility of this method.
- Shao, Changdong,Shi, Guangfa,Zhang, Yanghui
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supporting information
p. 5529 - 5538
(2016/11/25)
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- Copper-Catalyzed Cyanation of Aryl- and Alkenylboronic Reagents with Cyanogen Iodide
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Direct catalytic cyanation of organoboronic acids with cyanogen iodide has been achieved by using a copper-bipyridine catalyst system. The cyanation reaction is likely to occur through two catalytic cycles: copper(II)-catalyzed iodination of organoboronic acids and the following cyanidocopper(I)-mediated cyanation of organic iodides.
- Okamoto, Kazuhiro,Sakata, Naoki,Ohe, Kouichi
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p. 4670 - 4673
(2015/10/12)
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- Sterically controlled iodination of arenes via iridium-catalyzed C-H borylation
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A mild method to prepare aryl and heteroaryl iodides by sequential C-H borylation and iodination is reported. The regioselectivity of this process is controlled by steric effects on the C-H borylation step and is complementary to existing methods to form aryl iodides. The iodination of boronic esters has potential for the synthesis of radiolabeled aryl iodides, as demonstrated by the concise synthesis of a potential tracer for SPECT imaging.
- Partridge, Benjamin M.,Hartwig, John F.
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p. 140 - 143
(2013/03/28)
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- Copper-catalyzed halogenation of arylboronic acids
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In this Letter, a copper-catalyzed halogenation of arylboronic acids was described. This reaction tolerates a variety of functional groups, providing aromatic halides with good yields. It represents a facile and mild procedure to aryl halides.
- Zhang, Guangyou,Lv, Guanglei,Li, Liping,Chen, Fan,Cheng, Jiang
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experimental part
p. 1993 - 1995
(2011/04/25)
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- Copper(I) Phenoxide complexes in the etherification of aryl halides
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"Chemical Equation Presented" No copping out! Copper(I) phenoxide complexes containing chelating ligands (see picture), proposed intermediates in copper-catalyzed etherification of aryl halides, have been synthesized and fully characterized. The kinetic and chemical competence of the isolated complexes are demonstrated for the synthesis of aryl phenyl ethers, and experiments provide evidence against mechanistic pathways involving the formation of either free or caged radicals.
- Tye, Jesse W.,Weng, Zhiqiang,Giri, Ramesh,Hartwig, John F.
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supporting information; experimental part
p. 2185 - 2189
(2010/06/19)
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- Efficient copper-catalyzed N-arylation of sulfoximines with aryl iodides and aryl bromides
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Two simple and inexpensive systems for copper-catalyed N-arylations of sulfoximines with aryl bromides and aryl iodides have been developed. Using 10 mol % of a copper(I) salt in combination with 20 mol % of a 1,2-diamine and Cs2CO3 provides N-arylated sulfoximines in high yields. Various functional groups and heteroatoms are tolarated. The method is complementary to the known protocols for N-arylations of sulfoximines, which require stoichiometric quantities of copper salts or cost-intensive palladium/BINAP catalysts.
- Sedelmeier, Joerg,Bolm, Carsten
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p. 6904 - 6906
(2007/10/03)
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- COPPER-CATALYZED FORMATION OF CARBON-HETEROATOM AND CARBON-CARBON BONDS
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One aspect of the present invention relates to copper-catalyzed carbon-heteroatom and carbon-carbon bond-forming methods. In certain embodiments, the present invention relates to copper-catalyzed methods of forming a carbon-sulfur bond between the sulfur atom of a thiol moiety and the activated carbon of an aryl, heteroaryl, or vinyl halide or sulfonate. In other embodiments, the present invention relates to copper(II)-catalyzed methods of forming a carbon-nitrogen bond between the nitrogen atom of an amide and the activated carbon of an aryl, heteroaryl, or vinyl halide or sulfonate. In certain embodiments, the present invention relates to copper-catalyzed methods of forming a carbon-carbon bond between the carbon atom of cyanide ion and the activated carbon of an aryl, heteroaryl, or vinyl halide or sulfonate. In another embodiment, the present invention relates to a copper-catalyzed method of transforming and aryl, heteroaryl, or vinyl iodide. Yet another embodiment of the present invention relates to a tandem method, which may be practiced in a single reaction vessel, wherein the first step of the method involves the copper-catalyzed formation of an aryl, heteroaryl, or vinyl iodide from the corresponding aryl, heteroaryl, or vinyl chloride or bromide; and the second step of the method involves the copper-catalyzed formation of an aryl, heteroaryl, or vinyl nitrile, amide or sulfide from the aryl, heteroaryl, or vinyl iodide formed in the first step.
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- Copper-catalyzed halogen exchange in aryl halides: An aromatic finkelstein reaction
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A mild and general method for the conversion of aryl, heteroaryl, and vinyl bromides into the corresponding iodides was developed utilizing a catalyst system comprising 5 mol % of Cul and 10 mol % of a 1,2- or 1,3-diamine ligand. A variety of polar functional groups are tolerated, and even N-H containing substrates such as sulfonamides, amides, and indoles are compatible with the reaction conditions. Both the reaction rate and the equilibrium conversion of the aryl bromide depend on the choice of the halide salt and the solvent. The best results were obtained using Nal as the halide salt and dioxane, n-butanol, or n-pentanol as the solvents. Copyright
- Klapars, Artis,Buchwald, Stephen L.
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p. 14844 - 14845
(2007/10/03)
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- A radical and an electron transfer process are compared in their regioselectivities towards a molecule with two different C-I bonds: Effect of steric congestion
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Steric compression in 1,4-diiodo-2,6-dimethylbenzene (2a) makes the C-I bond flanked by methyls substantially weaker (a buttressing effect) than the unhindered C-I bond. Calculations also confirm the weaker bonding interaction of the hindered C-I bond of 2a. This causes a remarkable regioselectivity toward the weaker bond in dehalogenation by stannyl radicals. Conversely, a much lower regioselectivity is found for a process -a photostimulated S(RN)1 reaction with the enolate ion of a ketone - which requires the conversion of 2a into a radical anion. A calculation of the BDE of the C-I bond for aa ArI·- system is offered. Finally, the hindered awl radical intermediate resulting from cleavage of the weaker C-I bond of 2a·- shows a modest but detectable discrimination between reduction or substitution, this once again being due to the steric congestion.
- Branchi, Barbara,Galli, Carlo,Gentili, Patrizia,Marinelli, Manuela,Mencarelli, Paolo
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p. 2663 - 2668
(2007/10/03)
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- The synthesis of [18F]fluoroarenes from the reaction of cyclotron-produced [18F]fluoride ion with diaryliodonium salts
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Diaryliodonium salts have been shown to react with fluoride ion at 80°C in acetonitrile to generate aryl fluorides. The regioselectivity is controlled electronically and by the bulk of the ortho-substituents on the rings, with the latter the dominant factor such that electron-rich rings can be fluorinated. ortho-Substituted aryl fluorides can be selectively produced from unsymmetrical diaryliodonium salts. The process has been used to synthesise [18F] labelled aromatics by the use of cyclotron generated [18F]fluoride ion.
- Shah, Aneela,Pike, Victor W.,Widdowson, David A.
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p. 2043 - 2046
(2007/10/03)
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