- Palladium-Catalyzed Arylation of Arylboronic Acids with Yagupolskii-Umemoto Reagents
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A Pd-catalyzed Suzuki cross-coupling of arylboronic acids with Yagupolskii-Umemoto reagents was explored. In contrary to trifluoromethylations, the Pd-catalyzed reaction of R-B(OH)2 and [Ar2SCF3]+[OTf]- provided the arylation products (R-Ar) in good to high yields. The reaction confirms that the S-Ar bonds of [Ar2SCF3]+[OTf]- can be readily cleaved in the presence of Pd complexes. The relatively electron-poor aryl groups of asymmetric [Ar1Ar2SCF3]+[OTf]- salts are more favorably transferred compared to the electron-rich ones. This reaction represents the first report of utilization of [Ar2SCF3]+[OTf]- as arylation reagents in organic synthesis.
- Wang, Shi-Meng,Wang, Xiao-Yan,Qin, Hua-Li,Zhang, Cheng-Pan
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p. 6542 - 6546
(2016/05/02)
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- Reactivity of aryldimesitylboranes under suzuki-miyaura coupling conditions
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Sterically protected triarylboron compounds such as BMes2(Ar) have important applications in organic optoelectronic devices and chemical sensors. Furthermore, the Suzuki-Miyaura cross-coupling reaction is the most commonly used method for building the π skeletons of such conjugated materials. We have found that BMes2(Ar) can also be a highly active and effective coupling partner under typical Suzuki-Miyaura coupling conditions. For BMes2(p-Br-Ph), self-coupling leads to the formation of oligomers Mes2B-(Ph)n-Mes, where the products with n = 1 (1), 2 (2), 3 (3), 4 (4) have been isolated and fully characterized. Examination of cross-coupling reactions of BMes2(Ph) with various aryl bromides has established the generality of BMes2(Ar) as a coupling partner.
- Wang, Nan,Hudson, Zachary M.,Wang, Suning
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experimental part
p. 4007 - 4011
(2011/01/03)
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- Revealing a second transmetalation step in the Negishi coupling and its competition with reductive elimination: Improvement in the interpretation of the mechanism of biaryl syntheses
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This paper presents an experimental and theoretical investigation of the Pd-catalyzed Negishi coupling reaction and reveals a novel second transmetalation reaction between an Ar1-Pd-Ar2 species and the organozinc reagent Ar2-ZnX. Understanding of this second step reveals how homocoupling and dehalogenation products are formed. Thus, the second transmetalation generates Ar2PdAr2 and Ar 1ZnCl, which upon reductive elimination and hydrolysis, respectively, give the homocoupling product Ar2-Ar2 and the dehalogenation product Ar1H. The ratio of the cross-coupling product Ar1-Ar2 and the homocoupling product Ar 2-Ar2 is determined by competition between the second transmetalation and reductive elimination steps. This mechanism is further supported by density functional theoretical calculations. Calculations on a series of reactions suggest a strategy in controlling the selectivity of cross-coupling and homocoupling pathways, which we have experimentally verified.
- Liu, Qiang,Lan, Yu,Liu, Jing,Li, Gang,Wu, Yun-Dong,Lei, Aiwen
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supporting information; experimental part
p. 10201 - 10210
(2009/12/08)
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- Non-symmetrically substituted di-N-heterocyclic carbene palladium(II) complexes: Synthesis, structure and catalytic activity
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The synthesis and characterization of non-symmetric di-N-heterocyclic carbene (diNHC) silver(I) and palladium(II) complexes are described. The activity of the Pd(II) complexes in the Suzuki-Miyaura coupling reaction of bulky substrates was investigated. This synthetic route represents a possible general pathway into a wide variety of non-symmetrically substituted diNHC ligands.
- Paulose, Tressia A.P.,Olson, Jeremy A.,Wilson Quail,Foley, Stephen R.
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p. 3405 - 3410
(2008/12/22)
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- Kumada coupling of aryl and vinyl tosylates under mild conditions
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Aryl and alkenyl tosylates are easily prepared, inexpensive and, thus, attractive for transition-metal-catalyzed couplings, but their reactivity is low. We report examples of mild, palladium-catalyzed coupling of aryl, alkenyl, and alkyl Grignard reagents with aryl and alkenyl tosylates. The resulting biaryls, vinylarenes, and alkylarenes were isolated in good to excellent yield. These couplings were conducted with a nearly equimolar ratio of the two reactants, and many examples were conducted at room temperature.
- Limmert, Michael E.,Roy, Amy H.,Hartwig, John F.
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p. 9364 - 9370
(2007/10/03)
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- DECOMPOSITION OF (NiRR'L2) COMPLEXES INDUCED BY BROMINE OR ANODIC OXIDATION
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A study has been made of the decomposition of the compounds t-(NiRR'L2) (L=PMe2Ph and PEt3; R=aryl or vinyl groups) and (Ni(mes)(o-tol)bipy) (mes=mesityl) oxidatively induced either by electrochemical means or by bromine.No organometallic compound of Ni(III) was isolated in the above reactions, but a pentacoordinate intermediate of Ni(III) is postulated.Breakdown takes place readily after the Ni(III) intermediate is formed.If the decomposition is induced is induced electrochemically, the intermediate decomposes giving only the coupling product R-R'.When bromine is used as the oxidizing agent, the Ni(III) intermediate is only formed if coordination to the central atom is allowed by the volume of the ligands.Thus, (Ni(C2Cl3)(mes)(PMe2Ph)2) dos not decompose at all, and only (Ni(C2Cl3(mesBr2)(PMe2Ph)2) is obtained.The intermediate ' Ni(III)RR'BrL2' undergoes reductive elimination to give R-R', RBr and R'Br.The formation of the products R-R'is increasingly favoured the greater the electronegativity of the organic ligands.The reductive elimination giving RBr takes place more readily the greater the electronegativity of the organic ligand R.The product of the reductive elimination reaction is 'Ni(I)Br', 'Ni(I)R', or 'Ni(I)R'', which in the presence of bromine give Ni(2+), (NiBr(RBr)L2), phosphonium salts, RBr, and R'Br.
- Coronas, Juan M.,Muller, Guillermo,Rocamora, Mercedes
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p. 227 - 236
(2007/10/02)
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