19191-03-8Relevant academic research and scientific papers
Inner-Sphere versus Outer-Sphere Coordination of BF4- in a NHC-Gold(I) Complex
Veenboer, Richard M. P.,Collado, Alba,Dupuy, Stéphanie,Lebl, Tomas,Falivene, Laura,Cavallo, Luigi,Cordes, David B.,Slawin, Alexandra M. Z.,Cazin, Catherine S. J.,Nolan, Steven P.
, p. 2861 - 2869 (2017)
The role of counterions in chemistry mediated by gold complexes stretches much further than merely providing charge balance to cationic gold species. Interplay between their basicities and coordination strengths influences interactions with both the gold center and substrates in catalysis. Actual monogold(I) active species are generally believed to be monocoordinated species, formed from the abstraction or the decoordination of a second ligand from precursor complexes, but only a small amount of experimental evidence exists to underpin the existence of these transient species. The formation of a bench-stable neutral IPrCl-gold(I) tetrafluoroborate complex is reported herein. Experimental studies by X-ray diffraction analysis and NMR spectroscopy and theoretical studies by DFT calculations were conducted to determine the composition, structure, and behavior of this complex. The absence of an auxiliary ligand resulted in inner-sphere coordination of the counterion in the solid state. In solution, an equilibrium between two conformations was found with the counterion occupying inner-sphere and outer-sphere positions, respectively. Stoichiometric and catalytic reactivity studies with the tetrafluoroborate complex have been conducted. These confirmed the lability of the inner-sphere coordinating counterion that gives the IPrCl-gold(I) fragment behavior similar to that of related systems.
Palladium-catalyzed C-C bond formation: Synthesis of 1,1-dialkylbuta-1,3-dienes and β-phenylstyrenes via organoboron intermediates
Deagostino, Annamaria,Prandi, Cristina,Zavattaro, Chiara,Venturello, Paolo
, p. 2612 - 2616 (2003)
α,β-Unsaturated and α-phenyl acetals show different reactivity when treated with LIC-KOR superbase and trialkylboranes, in the presence of the reagent system PdL4-ArX (Suzuki-Miyaura cross-coupling conditions). In particular, unsaturated acetal
Palladium-Catalyzed Reductive Cross-Coupling Reaction of Aryl Chromium(0) Fischer Carbene Complexes with Aryl Iodides
Wang, Kang,Lu, Yu,Hu, Fangdong,Yang, Jinghui,Zhang, Yan,Wang, Zhi-Xiang,Wang, Jianbo
supporting information, p. 1 - 10 (2018/01/17)
The first palladium-catalyzed reductive cross-couplings of aryl chromium(0) carbene complexes with aryl iodides have been realized. This coupling reaction shows excellent functional group tolerance and high efficiency. Mechanistically, aryl chromium(0) carbene complexes undergo transmetalation with arylpalladium species to generate palladium(II) carbene intermediates, which is followed by migratory insertion. The catalytic cycle is then completed by hydrogen transfer and reductive elimination. Consistent with the mechanistic hypothesis, density functional theory (DFT) calculations support the involvement of a palladium carbene intermediate, and carbene migratory insertion is a facile step with an energy barrier of 5.1 kcal/mol. The carbene transfer step and the hydrogen transfer step are confirmed as the rate-limiting steps in the catalytic cycle.
Stereoselective gold(I)-catalyzed intermolecular hydroalkoxlation of alkynes
Veenboer, Richard M. P.,Dupuy, Stphanie,Nolan, Steven P.
, p. 1330 - 1334 (2015/02/19)
(Chemical Equation Presented) We report the use of cationic gold complexes [Au(NHC)(CH3CN)][BF4] and [{Au(NHC)}2(μ-OH)][BF4] (NHC = N-heterocyclic carbene) as highly active catalysts in the solvent-free hydroalkoxylation of internal alkynes using primary and secondary alcohols. Using this simple protocol, a broad range of (Z)-vinyl ethers were obtained in excellent yields and high stereoselectivities. The methodology allows for the use of catalyst loadings as low as 200 ppm for the addition of primary alcohols to internal alkynes (TON = 35 000, TOF = 2188 h-1).
Dichotomous reactivity in the reaction of triethyl- and triphenylphosphane HBr salts with dimethyl acetals: A novel entry to α-alkoxy-functionalized ylides and general synthesis of vinyl ethers and alkoxy dienes
Das, Priyabrata,McNulty, James
supporting information; experimental part, p. 3587 - 3591 (2010/09/05)
The discovery of dichotomous reactivity in the reaction of trialkyl- vs. triphenylphosphane HBr salts with acetals allows entry to functionalized α-methoxy phosphonium salts and a novel process for tertiary phosphane methylation. The new protocol opens a general entry to the synthesis of vinyl ethers and differentially substituted 1,3-dienes via Wittig reactions of the functionalized ylides derived from the α-methoxy phosphonium salts.
A parahydrogen based NMR study of Pt catalysed alkyne hydrogenation
Boutain, Marie,Duckett, Simon B.,Dunne, John P.,Godard, Cyril,Hernandez, Jose M.,Holmes, A. Jonathan,Khazal, Iman G.,Lopez-Serrano, Joaquin
body text, p. 3495 - 3500 (2010/07/03)
A parahydrogen based NMR study of the platinum(ii) bis-phosphine triflate catalysed hydrogenation of alkynes in methanol reveals that platinum bis-phosphine alkyl cations and methanol functionalised platinum bis-phosphine alkylether cations, are responsible for the observed alkene and vinylether products.
Palladium-catalyzed cleavage reaction of carbon-carbon triple bond with molecular oxygen promoted by lewis acid
Wang, Azhong,Jiang, Huanfeng
, p. 5030 - 5031 (2008/10/09)
A new Lewis acid promoted and palladium-catalyzed cleavage reaction of carbon-carbon triple bond with molecular oxygen was reported, in which alkyne or 1.3-diynes is split into carboxylic ester in various alcohols. Copyright
Heck reactions of α- or β-substituted enol ethers with aryl bromides catalysed by a tetraphosphane/palladium complex - Direct access to acetophenone or 1-arylpropanone derivatives
Battace, Ahmed,Feuerstein, Marie,Lemhadri, Mhamed,Zair, Touriya,Doucet, Henri,Santelli, Maurice
, p. 3122 - 3132 (2008/02/08)
cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphanylmethyl)cyclopentane/ [PdCl(C3H5)]2 efficiently catalyses the Heck reaction of α- and β-substituted enol ethers with aryl bromides. The arylation of 1-phenyl-1-(trimethylsilyloxy) ethylene led directly to the 2-aryl-1-phenylethanones. Similar reaction rates were observed with electron-rich, electron-deficient or sterically congested aryl bromides. Heck reaction with benzyl isopropenyl ether gave a mixture of isomers. However, this mixture gave selectively the 1-arylpropanones after hydrolysis. Employing β-methoxystyrene, 3-ethoxyacrylonitrile or methyl 3-methoxyacrylate, the regioselective α-arylation of these enol ethers was observed in all cases, but mixtures of (Z) and (E) isomers were generally obtained, which in many cases yielded a single ketone product after acid treatment. The stereoselectivity of this reaction depends on steric and electronic factors, and better stereoselectivities in favour of (Z) isomers were observed with electron-rich or sterically congested aryl bromides. Higher yields were obtained for this reaction with electron-rich or sterically congested aryl bromides than with electron-poor aryl bromides. These observations suggest that the rate-limiting step of the catalytic cycle is not the oxidative addition of the aryl bromide to the palladium complex with these substituted enol ethers. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Mild preparation of alkenes from phenyl sulfides: One-pot elimination of phenylthio group via sulfilimine at ambient temperature
Matsuo, Jun-Ichi,Kozai, Takaaki,Ishibashi, Hiroyuki
, p. 6095 - 6098 (2007/10/03)
(Chemical Equation Presented) Various alkenes were prepared from phenyl sulfides in a one-pot manner at room temperature by converting them to the corresponding S-aminosulfonium salts with O-mesitylenesulfonylhydroxylamine, followed by treatment with pota
Functionalization of alkynes catalyzed by t-Bu-P4 base
Imahori, Tatsushi,Hori, Chieko,Kondo, Yoshinori
, p. 1090 - 1092 (2007/10/03)
The addition of O- and N-nucleophiles to alkynes catalyzed by a phosphazene base, t-Bu-P4 base, was investigated. Alkynes were easily transformed to enol ethers and enamines in DMSO by the addition of nucleophiles. When phenylacetylene was reacted with di
