The Experts below are selected from a list of 777 Experts worldwide ranked by ideXlab platform
Lei Wang - One of the best experts on this subject based on the ideXlab platform.
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triethanolamine as an efficient and reusable base ligand and reaction medium for phosphane free palladium catalyzed heck reactions
European Journal of Organic Chemistry, 2006Co-Authors: Lei WangAbstract:Triethanolamine was found to be an efficient and reusable base, ligand and reaction medium for phosphane-free palladium-catalyzed Heck reactions. The olefination of iodo- and Bromoarenes generated the corresponding products in good to excellent yields in the presence of catalytic amounts of palladium acetate in triethanolamine without any additive. Moderate yields of the desired products were obtained with activated chloroarenes. In addition, triethanolamine could be recovered and recycled for five consecutive trials without significant loss of its reactivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
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Triethanolamine as an Efficient and Reusable Base, Ligand and Reaction Medium for Phosphane‐Free Palladium‐Catalyzed Heck Reactions
European Journal of Organic Chemistry, 2006Co-Authors: Lei WangAbstract:Triethanolamine was found to be an efficient and reusable base, ligand and reaction medium for phosphane-free palladium-catalyzed Heck reactions. The olefination of iodo- and Bromoarenes generated the corresponding products in good to excellent yields in the presence of catalytic amounts of palladium acetate in triethanolamine without any additive. Moderate yields of the desired products were obtained with activated chloroarenes. In addition, triethanolamine could be recovered and recycled for five consecutive trials without significant loss of its reactivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
John F. Hartwig - One of the best experts on this subject based on the ideXlab platform.
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Nickel-Catalyzed Asymmetric α-Arylation and Heteroarylation of Ketones with Chloroarenes: Effect of Halide on Selectivity, Oxidation State, and Room-Temperature Reactions
Journal of the American Chemical Society, 2011Co-Authors: John F. HartwigAbstract:We report the α-arylation of ketones with a range of aryl chlorides with enantioselectivities from 90 to 99% ee catalyzed by the combination of Ni(COD)2 and (R)-BINAP and the coupling of ketones with a range of heteroaryl chlorides with enantioselectivities up to 99% ee catalyzed by Ni(COD)2 and (R)-DIFLUORPHOS. The analogous reactions of Bromoarenes occur with much lower enantioselectivities. Mechanistic studies showed that the difference in the rates of decomposition of the arylnickel(II) halide intermediates to {[(R)-BINAP]NiX}2 likely accounts for the difference in the enantioselectivities of the reactions of Bromoarenes and chloroarenes. This catalyst decomposition can be overcome by conducting the reactions with [(R)-BINAP]Ni(η2-NC-Ph) (4), which undergoes oxidative addition to haloarenes at room temperature.
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Autocatalytic oxidative addition of PhBr to Pd(PtBu3)2 via Pd(PtBu3)2(H)(Br).
Journal of the American Chemical Society, 2008Co-Authors: Fabiola Barrios-landeros, Brad P. Carrow, John F. HartwigAbstract:We report that oxidative addition of bromobenzene to Pd(PtBu3)2 occurs by an unusual autocatalytic mechanism. Studies on the effect of various additives showed that the degree of rate acceleration followed the trend: (PtBu3)Pd(Ph)(Br) approximately (HPtBu3)Br < [(PtBu3)Pd(mu-Br)]2 < (PtBu3)2Pd(H)(Br). Studies on the reactions of Pd(PtBu3)2 in the presence of (PtBu3)2Pd(H)(Br) showed that the concentration of (PtBu3)2Pd(H)(Br) decreased only after the Pd(0) complex had been consumed. These data indicated that the catalyst in this process is (PtBu3)2Pd(H)(Br). Thermal decomposition of the three-coordinate oxidative addition product (PtBu3)Pd(Ar)(Br) during the reaction of Pd(PtBu3)2 and Bromoarenes ultimately leads to formation of (PtBu3)2Pd(H)(Br). Parallel reactions of bromobenzene with (PtBu3)2Pd(H)(Br) and Pd(PtBu3)2 showed that the Bromoarenes reacted considerably faster with the Pd(II) species than with the Pd(0) species. We therefore propose a catalytic cycle for oxidative addition in which PBut3.HBr reacts with the Pd(0) species to form (PtBu3)2Pd(H)(Br), and (PtBu3)2Pd(H)(Br) reacts with the Bromoarene, possibly though the anionic species [HPtBu3+][(PtBu3)Pd(Br)-], to form [Pd(PtBu3)(Ar)(Br)].
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Organic Syntheses - α‐Arylation of Esters Catalyzed by the Pd(I) Dimer [P(t‐Bu)3Pd(μ‐Br)]2
Organic letters, 2008Co-Authors: Takuo Hama, John F. HartwigAbstract:Conditions for the coupling of Bromoarenes with esters using a single base and catalyst with improved turnover numbers are described. These general conditions were made possible by using the Pd(I) catalyst {[P(t-Bu)3]PdBr}2. Reactions of acetates, propionates, and isobutyrates are presented, and reactions of all three classes of esters on a 10 g scale are described.
C. Deraedt - One of the best experts on this subject based on the ideXlab platform.
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Efficient Click‐Polymer‐Stabilized Palladium Nanoparticle Catalysts for Suzuki–Miyaura Reactions of Bromoarenes and Reduction of 4‐Nitrophenol in Aqueous Solvents
Advanced Synthesis & Catalysis, 2013Co-Authors: C. Deraedt, L. Salmon, J. Ruiz, Didier AstrucAbstract:Palladium nanoparticles (size=1.6±0.3 nm) stabilized by a polyethylene glycol containing triazolyl rings, synthesized by click reaction in water, are efficient catalysts for the Suzuki-Miyaura coupling of Bromoarenes in aqueous ethanol and the borohydride reduction of 4-nitrophenol in water. Turnover numbers (TONs) reach 99,000 and turnover frequencies (TOFs) are up to 198,000 h−1 for the C-C cross coupling reactions in water/ethanol.
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Efficient click-polymer-stabilized palladium nanoparticle catalysts for Suzuki-Miyaura reactions of Bromoarenes and reduction of 4-nitrophenol in aqueous solvents
Advanced Synthesis and Catalysis, 2013Co-Authors: C. Deraedt, L. Salmon, J. Ruiz, Dominique AstrucAbstract:Palladium nanoparticles (size=1.6±0.3 nm) stabilized by a polyethylene glycol containing triazolyl rings, synthesized by click reaction in water, are efficient catalysts for the Suzuki-Miyaura coupling of Bromoarenes in aqueous ethanol and the borohydride reduction of 4-nitrophenol in water. Turnover numbers (TONs) reach 99,000 and turnover frequencies (TOFs) are up to 198,000 h−1 for the C-C cross coupling reactions in water/ethanol.
Jochanan Blum - One of the best experts on this subject based on the ideXlab platform.
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Lanthanide assisted cross-coupling of aryl bromides with triethylaluminum
Tetrahedron Letters, 2003Co-Authors: Margarita Shenglof, Dmitri Gelman, Gary A. Molander, Jochanan BlumAbstract:Cerium trichloride, as well as some other lanthanide salts, promote the palladium-catalyzed cross-coupling of triethylaluminum with Bromoarenes. The lanthanide compounds also increase the selectivity by diminishing the undesired hydrodebromination process.
Didier Astruc - One of the best experts on this subject based on the ideXlab platform.
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Efficient Click‐Polymer‐Stabilized Palladium Nanoparticle Catalysts for Suzuki–Miyaura Reactions of Bromoarenes and Reduction of 4‐Nitrophenol in Aqueous Solvents
Advanced Synthesis & Catalysis, 2013Co-Authors: C. Deraedt, L. Salmon, J. Ruiz, Didier AstrucAbstract:Palladium nanoparticles (size=1.6±0.3 nm) stabilized by a polyethylene glycol containing triazolyl rings, synthesized by click reaction in water, are efficient catalysts for the Suzuki-Miyaura coupling of Bromoarenes in aqueous ethanol and the borohydride reduction of 4-nitrophenol in water. Turnover numbers (TONs) reach 99,000 and turnover frequencies (TOFs) are up to 198,000 h−1 for the C-C cross coupling reactions in water/ethanol.
