- Ultrasmall and Stable Pd and Pt Nanoparticles Within Zeolite HY Through Impregnated Method with Enhanced Semihydrogenation Selectivity
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In this study, with zeolite HY as support, ultrasmall Pd and Pt nanoparticles were successfully immobilized into zeolite HY crystals through an optimized impregnation approach. The success of this new approach mainly relied on the selecting appropriate metal precursor to make Pd and Pt element exists with the cation forms, which can facilitate their diffusion into inner channels of zeolite HY through electrostatic attraction and capillary force. Integration of confinement effect of zeolite HY, taking zeolite HY (Si/Al = 3) encapsulation of ultrasmall Pd NPs (Pd@HY-3) as an instance, Pd@HY-3 catalyst exhibited enhanced catalytic selectivity in semihydrogenation of alkynes, in comparison with Pd/HY, Pd/C, Pd/Al2O3 and lindlar catalysts. This improved catalytic selectivity can be attributed to the constrained upright adsorption conformation of reactant alkyne and corresponding product alkene on encapsulated Pd surface to make alkyne adsorption on Pd surface with larger adsorption energy than that of alkene, thus achieving the high catalytic selectivity. Graphic Abstract: [Figure not available: see fulltext.]
- Wang, Mengyue,Liu, Xuan,Ren, Kui,Zhou, Yiming,Li, Tianhao,Bi, Yunfei,Kang, Haozhe,Xing, Enhui,Chen, Qiang
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p. 2684 - 2695
(2021/01/13)
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- Synthesis of water soluble Pd-Piperidoimidazolin-2-ylidene complexes and their catalytic activities in neat water
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Through the strategy of water soluble N-heterocyclic carbene (NHC) ligand, Pd-catalyzed reactions were developed in aqueous media. Therefore, four new piperidoimidazolinium salts (1a-d) consisting of sulfonate (a), esther (b, c) and carboxylic acid (d) functionalities and their water-soluble Pd-NHC complexes (2a-d) were synthesized. The new compounds were characterized by elemental analysis, FTIR, TGA, UV–vis and NMR spectroscopy. The catalytic activities of water soluble Pd-NHC complexes (2a-d) were investigated using the Suzuki-Miyaura (S-M) reaction and the reduction of nitroarenes. We found that the water-soluble polar or ionic groups on piperidoimidazolin-2-ylidine had an effect on the catalytic activity. The water-soluble catalyst can be recycled efficiently and reused six times with only a very slight loss of catalytic activity.
- ?ak?r, Sinem,Türkmen, Hayati
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- NITROGEN-CONTAINING BIOPOLYMER-BASED CATALYSTS, THEIR PREPARATION AND USES IN HYDROGENATION PROCESSES, REDUCTIVE DEHALOGENATION AND OXIDATION
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The present invention relates to a process for the preparation of a nitrogen containing biopolymer-based catalyst by pyrolysis of a metal complex with a nitrogen-containing biopolymer and to the nitrogen containing biopolymer-based catalysts obtainable by this process. In particular, the invention relates to a nitrogen containing biopolymer-based catalyst comprising metal particles and at least one nitrogen containing carbon layer. The invention also relates to the use of a nitrogen containing biopolymer-based catalyst in a hydrogenation process, preferably in a process for hydrogenation of nitroarenes, nitriles or imines; in a reductive dehalogenation process of C-X bonds, wherein X is CI, Br or I, preferably in a process for dehalogenation of organohalides or in a process for deuterium labelling of arenes via dehalogenation of organohalides; or in an oxidation process. Further, the invention relates to a metal complex with the nitrogen containing biopolymer, wherein the metal is a transition metal selected from the group consisting of manganese, ruthenium, cobalt, rhodium, nickel, palladium and platinum, preferably cobalt or nickel, and wherein the nitrogen containing biopolymer is selected from chitosan, chitin and a polyamino acid, preferably chitosan or chitin.
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Page/Page column 31-32
(2018/07/29)
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- Synthesis and characterization of a stable non-cyclic bis(amino)arsenium cation
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The reaction of Li[Mes?NH] (1, Mes? = 2,4,6-tri-tert-butylphenyl) with aminoarsane Mes?N(H)AsCl2 (2, Mes? = 2,4,6-t-Bu3C6H2) at -80 °C resulted in the formation of bisamino(chloro)arsane (Mes?NH)2AsCl (3Cl) by elimination of LiCl. 3Cl reacted with the Lewis acids such as AlCl3, GaCl3, and Ag[X] (X = AsF6-, OTf-, BF4-; OTf = trifluoromethanesulfonate = OSO2CF3-) upon chloride ion abstraction to give salts bearing the cation [(Mes?NH)2As]+ (3[X]; X = AsF6-, OTf-, BF4-, ECl4; E = Al, Ga). 3+ represents the first NH-functionalized acyclic bis(amino)arsenium cation. The formation of the salts bearing 3+ could also be observed in the reaction of cyclo-1,3-diarsa-2,4-diazane [ClAs(μ-NMes?)]2 (4) with Lewis acids (AlCl3, GaCl3) in the presence of proton sources in solution. All presented salts 3[X] were stable at room temperature and fully characterized.
- Kuprat, Marcus,Schulz, Axel,Thomas, Max,Villinger, Alexander
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supporting information
p. 502 - 512
(2018/06/07)
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- Biomass-Derived Catalysts for Selective Hydrogenation of Nitroarenes
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Development of catalytically active materials from biowaste represents an important aspect of sustainable chemical research. Three heterogeneous materials were synthesized from inexpensive biomass-based chitosan and abundant Co(OAc)2 using complexation followed by pyrolysis at various temperatures. These materials were applied in the catalytic hydrogenation of nitroarenes using molecular hydrogen. A variety of diversely functionalized nitroarenes including some pharmaceutically active compounds were converted into aromatic amines in high yields, with high selectivity, and with excellent functional group tolerance. This green protocol has also been implemented for the synthesis of a biologically important TRPC3 inhibitor.
- Sahoo, Basudev,Formenti, Dario,Topf, Christoph,Bachmann, Stephan,Scalone, Michelangelo,Junge, Kathrin,Beller, Matthias
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p. 3035 - 3039
(2017/08/18)
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- Dichloro-Cycloazatriphosphane: The Missing Link between N2P2 and P4 Ring Systems in the Systematic Development of NP Chemistry
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A dichloro-cycloazatriphosphane that incorporates a cyclic NP3 backbone could be synthesized using knowledge gained from the chemistry of N2P2 and P4 ring systems. It fills the gap between the congeneric compounds [ClP(μ-NR)]2 and [ClP(μ-PR)]2 (R=sterically demanding substituent), and thus contributes to the systematic development of nitrogen–phosphorus chemistry in general. The title compound was studied with respect to its formation via a labile aminodiphosphene, which readily underwent different rearrangement reactions depending on the solvent. All compounds were fully characterized by experimental and computational methods.
- Bresien, Jonas,Hinz, Alexander,Schulz, Axel,Suhrbier, Tim,Thomas, Max,Villinger, Alexander
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supporting information
p. 14738 - 14742
(2017/10/12)
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- Synthesis of Aminobismuthanes via Me3SnCl Elimination
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The synthesis of N-trimethylstannylamines of the type RN(SnMe3)H (stannylated anilines) with the sterically encumbered substituents R such as Ter [terphenyl, 2,6-bis(2,4,6-trimethylphenyl)-phenyl], Ar* [2,6-bis(diphenylmethyl)-4-methylphenyl],
- Schulz, Axel,Thomas, Max,Villinger, Alexander
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supporting information
p. 1406 - 1414
(2017/10/05)
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- Fe2O3/NGr@C- and Co-Co3O4/NGr@C-catalysed hydrogenation of nitroarenes under mild conditions
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An improved hydrogenation of nitroarenes using nano-structured iron- and cobalt-based catalysts is presented. Modifications of the heterogeneous catalysts by N-doped graphene-flakes are crucial for the success of selective reductions. The use of polar solvents and basic additives has a significant positive influence on the rate of reduction of nitroarenes. This allows performing non-noble metal-catalysed hydrogenations under very mild reaction conditions (e.g. 70 °C and 20 bar). On the basis of the obtained catalytic results a heterolytic mechanism for the hydrogenation process is postulated, too.
- Formenti, Dario,Topf, Christoph,Junge, Kathrin,Ragaini, Fabio,Beller, Matthias
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p. 4473 - 4477
(2016/07/06)
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- Reaction of aromatic nitroso compounds with chemical models of 'thiamine active aldehyde'
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Aromatic nitroso compounds in the presence of base and 2-(α-hydroxyalkyl)-3,4-dimethylthiazolium trifluoromethanesulfonate and related salts furnish in variable yields O- and N-acyl-aryl hydroxylamines and 3,4-dimethylthiazolium trifluoromethanesulfonate. A primary kinetic isotope effect of 4.9, obtained for the appropriate 2α-deuterated thiazolium salt, points to the C2α-H bond cleavage as the rate determining step. Radical species detected by ESR were unambiguously identified as phenylhydronitroxide, but attempted trapping of the corresponding C-heterocyclic radicals by TEMPO was not successful, and substrates incorporating a potential cyclopropyl radical clock gave products with the cyclopropyl ring intact. Theoretical calculations revealed a large activation energy for such reaction, which thus cannot per se exclude the intervention of such radical species. Evidence for the likely operation of two concurrent mechanisms, a radical and a preponderant ionic pathway, involving the conjugate base of the thiazolium salt, as the chemical model for 'active thiamine', and ArNO is presented for the formation of the products of the reaction.
- Ferreira, Luísa M.,Marques, M. Manuel B.,Glória, Paulo M.C.,Chaves, Humberto T.,Franco, Jo?o-Pedro P.,Mourato, Isabel,Antunes, José-Rafael T.,Rzepa, Henry S.,Lobo, Ana M.,Prabhakar, Sundaresan
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p. 7759 - 7770
(2008/12/21)
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- Silaamidide salts: Synthesis, structure, and reactions
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Five silaamidides have been prepared and characterized: lithium N,N'-bis(2,4,6-tri-tert-butylphenyl)phenylsilaamidide (2), lithium N,N'-bis(2,4,6-tri-tert-butylphenyl)chlorosilaamidide (5), lithium N,N'-bis(2,4,6-tri-tert-butylphenyl)-n-butylsilaamidide (6), lithium N,N'-bis(2,4,6-tri-tert-butylphenyl)-tert-butylsilaamidide (7), and potassium N,N'-bis(2,4,6-tri-tert-butylphenyl)chlorosilaamidide (8). Reactions of silaamidides with alcohols, amines, hydrogen bromide, n-butyllithium, and benzaldehyde are described. The structure of 7·(12-crown-4)(THF) was determined by X-ray analysis: crystals are orthorhombic, space group Pna21; a = 16.289 (7), b = 17.991 (8), c = 17.965 (8) A?; V = 5265 (4) A?3; dcalcd = 1.084 g/mL for Z = 4; R = 5.05%. The Si-N bond distances are 1.594 and 1.626 A?, and the Si and attached N, N, and C atoms are coplanar.
- Underiner, Gail E.,Tan, Robin P.,Powell, Douglas R.,West, Robert
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p. 8437 - 8443
(2007/10/02)
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- REACTIONS OF TRIMETHYL- AND TRIETHYLALUMINIUM WITH 2,4,6-TRI-t-BUTYLNITROSOBENZENE
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Me3Al and Et3Al undergo 1,2-, 1,4- and 1,6-addition to 2,4,6-tri-t-butylnitrosobenzene to give after hydrolysis the corresponding nitrones and oximes.In systems containing Et3Al the addition products partly undergo further reduction to aromatic amines bearing an ethyl group on the nitrogen atom or the ring.Reduction processes, leading to 2,4,6-tri-t-butylaniline, take place along with the addition reactions.
- Florjanczyk, Zbigniew,Langwald, Norbert
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p. 297 - 304
(2007/10/02)
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- Picosecond Laser Photolysis Studies of Hydrogen Atom Transfer Reaction via Heteroexcimer State in Pyrene-Primary and Pirene-Secondary Aromatic Amine Systems: Role of "Hydrogen-Bonding" Interaction between Amino Group of Donor and ? Electron Acceptor in the Heteroexcimer
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The mechanism of charge transfer followed by proton transfer in the hydrogen atom transfer reaction of excited pyrene-primary and -secondary amine systems has been directly demonstrated by means of a picosecond laser photolysis method.In the case of pyrene-N-ethylamine heteroexcimer system in hexane, for example, it has been observed that the 1-hydro-1-pyrenyl radical and the pyrene triplet state are produced simultaneously in the time region of subnanosecond to nanosecond.The deuteration of the NH group of the amine affects considerably the rate of formation of the 1-hydro-1-pyrenyl radical but not the rate of intersystem crossing from the heteroexcimer.On the basis of the results obtained for various pyrene-primary and -secondary aromatic amine heteroexcimer systems, the nature of the interaction between donor and acceptor in these heteroexcimers and their conformation in relation to the mechanism of the hydrogen atom transfer reaction via heteroexcimer have been elucidated.
- Okada, Tadashi,Karaki, Ichiro,Mataga, Noboru
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p. 7191 - 7195
(2007/10/02)
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- Chemistry of N-Thiosulfinylanilines. V. Reactions of N-Thiosulfinylanilines with Nucleophilic Reagents
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2,4-Di-t-butyl-6-methyl-N-(thiosulfinyl)aniline (1) gave 2,4-di-t-butyl-6-methylaniline in the reactions with such reagents as alkylamines, thiourea, butyllithium, alkylmagnesium halides, 1-(1-pyrrolidinyl)cyclopentene, and hydrogen sulfide.Triphenylphosphine reacted with 1 to give (2,4-di-t-butyl-6-methylphenylimino)triphenylphosphorane and bis(2,4-di-t-butyl-6-methylphenyl)sulfur diimide.Reaction of triphenylphosphine with 2,4,6-tri-t-butyl-7,8-dithia-9-azabicyclonona-2,4,9-triene afforded 2,4,6-tri-t-butylaniline, bis(2,4,6-tri-t-butylphenyl)sulfur diimide, and 2,4,6-tri-t-butyl-N-sulfinylaniline (7).The sulfur diimide was considered to be formed via intermediary 2,4,6-tri-t-butylthionitrosobenzene, which was trapped by oxygen to give the N-sulfinyl derivative 7.
- Inagaki, Yoshio,Hosogai, Takeo,Okazaki, Renji,Inamoto, Naoki
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p. 205 - 209
(2007/10/02)
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