- Evidence for a Cooperative Mechanism Involving Two Palladium(0) Centers in the Oxidative Addition of Iodoarenes
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Oxidative addition of iodoarenes (ArI) to Pd0 ligated by 1-methyl-1H-imidazole (mim) in polar solvents leads to cationic arylpalladium(II) complexes [ArPd(mim)3]+. Kinetic analyses evidence that this reaction is second order with respect to the concentration of Pd0, and a mechanism involving the cooperative intervention of two Pd0 centers has been postulated to explain this finding. This unusual behavior is also observed with other nitrogen-containing ligands and it is general for iodobenzenes substituted with electron-donating or weakly electron-withdrawing groups. In contrast, bromoarenes and electron-poor iodoarenes display first-order kinetics with respect to Pd0. Theoretical calculations performed at the density functional theory (DFT) level suggest the existence of mim-ligated ArI-Pd0 complexes, in which the iodoarene is bound to the metal in a halogen-bond-like fashion. Coordination weakens the C?I bond and facilitates the oxidative insertion of another Pd0 center across this C?I bond. This conceptually novel mechanism, involving the cooperative participation of two distinct metal centers, allows a full explanation of the experimentally observed kinetics.
- Perego, Luca Alessandro,Payard, Pierre-Adrien,Haddou, Baptiste,Ciofini, Ilaria,Grimaud, Laurence
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- Nature of the modifying action of white phosphorus on the properties of nanosized hydrogenation catalysts based on bis(dibenzylideneacetone)palladium(0)
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The catalytic properties and nature of the nanoparticles forming in the system based on Pd(dba)2 and white phosphorus are reported. A schematic mechanism is suggested for the formation of nanosized palladium-based hydrogenation catalysts. The m
- Belykh,Skripov,Belonogova,Umanets,Stepanova,Schmidt
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- Synthesis of Indoles by Reductive Cyclization of Nitro Compounds Using Formate Esters as CO Surrogates
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Alkyl and aryl formate esters were evaluated as CO sources in the Pd- and Pd/Ru-catalyzed reductive cyclization of 2-nitrostyrenes to give indoles. Whereas the use of alkyl formates requires the presence of a ruthenium catalyst such as Ru3(CO)12, the reaction with phenyl formate can be performed by using a Pd/phenanthroline complex alone. Phenyl formate was found to be the most effective CO source and the desired products were obtained in excellent yields, often higher than those previously reported using pressurized CO. The reaction tolerates many functional groups, including sensitive ones like a free aldehydic group or a pendant pyrrole. Detailed experiments and kinetic studies allow to conclude that the activation of phenyl formate is base-catalyzed and that the metal doesn't play a role in the decarbonylation step. The reactions can be performed in a single thick-walled glass tube with as little as 0.2 mol-% palladium catalyst and even on a 2 g scale. The same protocol can be extended to other nitro compounds, affording different heterocycles.
- Ahmed Fouad, Manar,Ferretti, Francesco,Formenti, Dario,Milani, Fabio,Ragaini, Fabio
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supporting information
p. 4876 - 4894
(2021/09/20)
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- Preparation method of high-purity tris(dibenzylideneacetone)dipalladium (0)
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The invention discloses a preparation method of high-purity tris(dibenzylideneacetone)dipalladium (0). The method includes 1, in a nitrogen atmosphere, adding ligand dibenzylideneacetone, palladium dichloride and anhydrous sodium acetate to anhydrous ethanol that is in a stirring state to carry out a heating reaction, and performing filtering to obtain solid bis(dibenzylideneacetone)palladium (0); 2, in a nitrogen atmosphere, adding the solid bis(dibenzylideneacetone)palladium (0) obtained in the step 1 to acetone that is in a stirring state, washing a retained product after filtering, and drying the washed retained product to obtain the tris(dibenzylideneacetone)dipalladium (0). The preparation method has the advantages that the bis(dibenzylideneacetone)palladium (0) is prepared from the anhydrous ethanol, the dibenzylideneacetone, the palladium dichloride and the anhydrous sodium acetate at first, and then is treated by an acetone solution to obtain the tris(dibenzylideneacetone)dipalladium (0), and accordingly, the obtained tris(dibenzylideneacetone)dipalladium (0) has high purity.
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Paragraph 0024-0026; 0029-0031; 0034-0036
(2019/10/04)
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- A synthesis method according to sets up qu tan hydrobromide
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The invention discloses a synthesis method of eletriptan hydrobromate, which comprises the following steps: reacting (R)-1-acetyl-3-(N-methylpyrrolidinyl-2-methy)-5-bromo-1H-indole and metal in an organic solvent to form a metal complex, reacting the metal complex with a boron reagent in an organic solvent to form aryl borane or aryl borate, carrying out acid-catalyzed hydrolysis to obtain aryl boric acid, and carrying out coupling and hydrolysis on the aryl boric acid and 2-chloroethylphenyl sulfone under the actions of a catalyst and an alkali to obtain eletriptan, or directly carrying out coupling and hydrolysis on the metal complex and 2-chloroethylphenyl sulfone to obtain eletriptan; and carrying out salification on the eletriptan and hydrobromic acid in an organic solvent to finally obtain the eletriptan hydrobromate. The method is simple to operate, has the advantages of high safety, high stability, low cost and higher yield, and is suitable for industrial production.
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Paragraph 0050-0052
(2017/10/22)
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- Factors determining the chemoselectivity of phosphorus-modified palladium catalysts in the hydrogenation of chloronitrobenzenes
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The precursor nature effect on the state of the Pd–P surface layer in palladium catalysts and on their properties in the liquid-phase hydrogenation of chloronitrobenzenes under mild conditions has been investigated. A general feature of the Pd–P-containing nanoparticles obtained from different precursors and white phosphorus at P/Pd = 0.3 (PdCl2 precursor) and 0.7 (Pd(acac)2 precursor) is that their surface contains palladium in phosphide form (BE(Pd3d5/2) = 336.2 eV and BE(Р2р) = 128.9 eV) and Pd(0) clusters (BE(Pd3d5/2) = 335.7 eV). Factors having an effect on the chemoselectivity of the palladium catalysts in chloronitrobenzenes hydrogenation are considered, including the formation of small palladium clusters responsible for hydrogenation under mild conditions.
- Skripov,Belykh,Sterenchuk,Akimov,Tauson,Schmidt
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- Formation of palladium phosphides in the reaction of bis(dibenzylideneacetone)palladium(0) with white phosphorus
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The reaction of bis(dibenzylideneacetone)palladium(0) with white phosphorus was studied using the methods of NMR, UV spectroscopy, and X-ray powder diffraction. The products of the reaction are shown to be palladium phosphides, their composition depending on the ratio of the reagents. The mechanism of the formation of the palladium-enriched phosphides is suggested, which includes the formation of palladium diphosphide PdP2 that subsequently reacts with the excess of bis(dibenzylideneacetone)palladium(0) leading to palladium phosphides Pd5P2, Pd3P0.8, Pd 4.8P, and free dibenzylideneacetone. Pleiades Publishing, Ltd., 2012.
- Skripov,Belykh,Belonogova,Rokhin,Stepanova,Shmidt
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p. 206 - 211
(2012/07/02)
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- Palladium(0)-dibenzylidene acetone complexes
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Palladium(0)-dibenzylidene acetone complexes Pdx(dba)y, with y/x being from 1.5 to 3, are provided according to the invention at a purity of at least 99.5 wt. %. The use of said Pdx(dba)y complexes according to
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Page/Page column 3; 4
(2011/09/13)
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- High enantio-selective process for producing pure enantiomeric cyclopentane and cyclopentene-(β)-amino acids
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The present invention relates to a highly enantioselective process for the preparation of enantiomerically pure cyclopentane- and -pentene β-amino acids of the general formula (I) STR1 in which A and L, A and D or E and L, D and E, R2, R3, T and R1 have the meaning given in the description.
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- The Stereochemistry of Organometallic Compounds. XXIX Synthesis of Stereoidal 1,4-, 1,3- and 1,6-Diphosphines and Their Evaluation as Ligands in Metal-Catalyzed Asymmetric Synthesis
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The steroidal 1,4-diphosphines 3α- and 3β-diphenylphosphino-2α-(2'-diphenylphosphinoethyl)-5α-cholestanes and their 5H-benzophosphindole derivatives have been prepared and shown to be useful ligands in asymmetric hydrogenation reactions.Interestingly the 3α- and 3β-derivatives lead to opposing enantioselection preferences when used in these reactions.A steroidal 1,3-diphospine, 3α-diphenylphosphino-2α-diphenylphosphinomethyl-5α-cholestane, has been prepared as a mixture containing some of the 3β-epimer.The 3α-1,3-diphosphine led to similar enantioselection in hydrogenation reactions as the 3α-1,4-diphosphine, and a model is proposed to explain the sense of the enantioselectivity in the 1,4- and 1,3-diphosphines.A steroidal 1,6-diphosphine has also been prepared but leads to lower optical yields in the hydrogenation reactions.These ligands have been shown to lead to only poor to moderate optical yields when used in asymmetric carbon-carbon bond forming reactions.
- Thomson, Robin J.,Jackson, W. Roy,Haarburger, David,Klabunovsky, Evgeny I.,Pavlov, Valery A.
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p. 1083 - 1106
(2007/10/02)
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