- Transition-metal-free decarboxylative bromination of aromatic carboxylic acids
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Methods for the conversion of aliphatic acids to alkyl halides have progressed significantly over the past century, however, the analogous decarboxylative bromination of aromatic acids has remained a longstanding challenge. The development of efficient methods for the synthesis of aryl bromides is of great importance as they are versatile reagents in synthesis and are present in many functional molecules. Herein we report a transition metal-free decarboxylative bromination of aromatic acids. The reaction is applicable to many electron-rich aromatic and heteroaromatic acids which have previously proved poor substrates for Hunsdiecker-type reactions. In addition, our preliminary mechanistic study suggests that radical intermediates are not involved in this reaction, which is in contrast to classical Hunsdiecker-type reactivity. Overall, the process demonstrates a useful method for producing valuable reagents from inexpensive and abundant starting materials.
- Quibell, Jacob M.,Perry, Gregory J. P.,Cannas, Diego M.,Larrosa, Igor
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p. 3860 - 3865
(2018/04/26)
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- Au-Catalyzed Oxidative Arylation: Chelation-Induced Turnover of ortho-Substituted Arylsilanes
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ortho-Substituted aryl silanes have previously been found to undergo much slower Au-catalyzed intermolecular arylation than their m,p-substituted isomers, with many examples failing to undergo turnover at all. A method to indirectly quantify the rates of C-Si auration of o-substituted aryl silanes, under conditions of turnover, has been developed. All examples are found to undergo very efficient C-Si auration, indicative that it is the subsequent C-H auration that is inhibited by the ortho substituent. A simple Ar-Au conformational model suggests that C-H auration can be accelerated by chelation. A series of ortho-functionalized aryl silanes are shown to undergo efficient arylation.
- Robinson, Matthew P.,Lloyd-Jones, Guy C.
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p. 7484 - 7488
(2018/07/30)
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- Selective Suzuki-Miyaura monocouplings with symmetrical dibromoarenes and aryl ditriflates for the one-pot synthesis of unsymmetrical triaryls
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The various parameters that would permit selective Suzuki-Miyaura monocouplings of symmetrical dihaloarenes were studied. High selectivity and efficiency can be obtained for a broad range of substrates by using operationally simple conditions and widely available reagents. The 38 different examples described provide a valuable toolbox for the rapid access to unsymmetrical triaryls, as illustrated by the preparation of diarylpyridine 8, terphenyl 9, and diarylpyrrole 10. By studying several key parameters, the factors that allow selective Suzuki-Miyaura monocoupling of symmetrical dihaloarenes have been outlined. This study serves as the basis for the efficient synthesis of unsymmetrical triaryls from symmetrical dibromoarenes and aryl ditriflates by a one-pot desymmetrizing double Suzuki-Miyaura coupling. Copyright
- Minard, Corinne,Palacio, Carole,Cariou, Kevin,Dodd, Robert H.
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p. 2942 - 2955
(2014/05/20)
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- Gold-catalyzed oxidative coupling of arylsilanes and arenes: Origin of selectivity and improved precatalyst
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The mechanism of gold-catalyzed coupling of arenes with aryltrimethylsilanes has been investigated, employing an improved precatalyst (thtAuBr3) to facilitate kinetic analysis. In combination with linear free-energy relationships, kinetic isotope effects, and stoichiometric experiments, the data support a mechanism involving an Au(I)/Au(III) redox cycle in which sequential electrophilic aromatic substitution of the arylsilane and the arene by Au(III) precedes product-forming reductive elimination and subsequent cycle-closing reoxidation of the metal. Despite the fundamental mechanistic similarities between the two auration events, high selectivity is observed for heterocoupling (C-Si then C-H auration) over homocoupling of either the arylsilane or the arene (C-Si then C-Si, or C-H then C-H auration); this chemoselectivity originates from differences in the product-determining elementary steps of each electrophilic substitution. The turnover-limiting step of the reaction involves associative substitution en route to an arene π-complex. The ramifications of this insight for implementation of the methodology are discussed.
- Ball, Liam T.,Lloyd-Jones, Guy C.,Russell, Christopher A.
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supporting information
p. 254 - 264
(2014/01/23)
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- A simple catalytic system based on PdCl2(CH3CN) 2 in water for cross-coupling reactions using diazonium salts
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Aryl-heteroaryl and heteroaryl-heteroaryl compounds are obtained through the Suzuki-Miyaura cross-coupling reactions between diazonium salts and potassium trifluoroborates using PdCl2(CH3CN)2 as the catalyst in water and in the absence of any additive, ligand or base. In addition, the same mild catalytic system is effective for the Matsuda-Heck reaction between several monoolefins with aryldiazonium salts.
- El Bakouri, Ouissam,Fernández, Martí,Brun, Sandra,Pla-Quintana, Anna,Roglans, Anna
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p. 9761 - 9765
(2013/10/22)
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- Electrophilic substitution of thiophenes with arylpalladium(II) and platinum(II) complexes: Mechanistic studies on palladium-catalyzed CH arylation of thiophenes
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Mechanistic studies on palladium-catalyzed CH arylation of thiophenes which has been shown by our group are carried out by a stoichiometric reaction of organometallic complexes. The reaction of arylpalladium(II) halide with 2,3- dibromothiophene in the pr
- Sugie, Atsushi,Furukawa, Hirotoshi,Suzaki, Yuji,Osakada, Kohtaro,Akita, Munetaka,Monguchi, Daiki,Mori, Atsunori
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experimental part
p. 555 - 562
(2009/11/30)
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- Brominated thiophenes as precursors in the preparation of brominated and arylated anthraquinones
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Brominated anthraquinones can be synthesized directly from bromothiophenes when these are reacted with 1,4-naphthoquinones in the presence of meta-chloroperoxybenzoic acid. The bromoanthraquinones are versatile building blocks in the preparation of arylated anthraquinones and of extended π-systems with interspersed anthraquinone units.
- Thiemann, Thies,Tanaka, Yasuko,Iniesta, Jesus
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experimental part
p. 1013 - 1031
(2009/10/10)
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- Preferential oxidative addition in palladium(0)-catalyzed suzuki cross-coupling reactions of dihaloarenes with arylboronic acids
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The study of Pd(0)-/t-Bu3P system as a powerful catalyst for the cross-coupling of n,m-dihaloarenes with 1 equiv of arylboronic acids is described. Our work demonstrated that the fate of the regenerated Pd(0) catalyst can be controlled when the appropriate ligand is employed. The results described here may lead to the development of new, efficient processes to conjugate polymers with controlled length which are potentially useful in molecular electronics. Copyright
- Dong, Cheng-Guo,Hu, Qiao-Sheng
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p. 10006 - 10007
(2007/10/03)
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