共查询到20条相似文献,搜索用时 15 毫秒
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Beta-hydroxyalkyl aryl chalcogenides obtained by regioselective ring-opening of epoxides with benzeneselenolate or -tellurolate were found to undergo efficient hetero-Michael addition when treated with ethyl propiolate. Subsequent carbonylation/reductive cyclization of the resulting vinylogous carbonates in the presence of AIBN/TTMSS and carbon monoxide (80 atm) afforded 2,5-disubstituted tetrahydrofuran-3-ones, predominantly as cis isomers (cis/trans = 4/1-9/1). Starting from a polymer-supported diaryl diselenide, the methodology was also successfully extended to solid-phase synthesis. Vinylogous carbamates prepared by hetero-Michael addition of aziridines to electron-deficient alkynes were regioselectively ring-opened with benzeneselenolate from the sterically least hindered side. Radical carbonylation/reductive cyclization of the resulting N-vinyl-beta-amino-alkyl phenyl selenides afforded 2,5-disubstituted pyrrolidin-3-ones, predominantly as cis isomers (cis/trans = 3/1-12/1). 相似文献
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The reactions of carbon monoxide with the palladium nitrosoarene complexes Pd2(-OCOR)2(—CH2C6H4NO)2 (1, R = Me, CF3, But, or Ph) and Pd2(-OCOR)2(PhNC6H4NO)2 (2, R = Me, CF3, But, or Ph) were studied. Complexes 1 contain the o-nitrosotoluene molecule metallated at the methyl group. In complexes 2, the phenyl-o-nitrosophenylamide ligand coordinated via two nitrogen atoms can be considered as a nitrosobenzene derivative bearing the NPh group in the ortho position of the Ph ring. It all cases, carbonylation of the complexes afforded the corresponding aryl isocyanates Ar—N=C=O or the products of their further transformations. The mechanism of reductive carbonylation of nitroarenes catalyzed by palladium compounds and the role of palladium nitrosoarene complexes as possible intermediates in this process are discussed. 相似文献
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Ezio Bolzacchini Ruggero Lucini Simone Meinardi Marco Orlandi Bruno Rindone 《Journal of molecular catalysis. A, Chemical》1996,110(3):227-233
Three nitroarenes were submitted to Ru3(CO)12-catalyzed reductive carbonylation in acetonitrile and in cis-cyclooctene. The main reaction products were the corresponding amines, ureas and six- or five-membered cyclization products. Optimization of the reaction varying the temperature, the CO pressure, the catalyst/substrate ratio and the reaction time and a statistical analysis of conversion and selectivity data allow to suggest a reaction mechanism in some reaction conditions. 相似文献
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Thanh Tung Nguyen Anh Vy Tran Hye Jin Lee Jayeon Baek Yong Jin Kim 《Tetrahedron letters》2019,60(50):151310
Direct reductive carbonylation of nitrobenzene to phenyl isocyanate with carbon monoxide was performed using various types of palladium catalysts together with many types of N-donor ligands. The effect of reaction time, pressure, temperature, ligand amount, and molar ratio to establish the optimized conditions was also investigated. With this, we were able to achieve up to 100% conversion and 63.5% yield with PdCl2 and alkylimidazole system (1:3) within 2 h at 220 °C and 1400 psi of CO in toluene. 相似文献
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《Journal of Molecular Catalysis #》1987,39(2):261-267
The reaction of methyl esters with synthesis gas and a Co—LiI catalyst results in the formation of anhydrous acetaldehyde and a carboxylic acid in very high yield. At 180 °C and 5000 psig, acetaldehyde is produced from methyl acetate at a rate of 7 M h−1 and >95% selectivity. 相似文献
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Lassauque N Davin T Nguyen DH Adcock RJ Coppel Y Le Berre C Serp P Maron L Kalck P 《Inorganic chemistry》2012,51(1):4-6
For the last step of rhodium-catalyzed methanol carbonylation, high-pressure NMR, and kinetic and experimental data supported by density functional theory calculations are consistent with substitution of I(-) by an AcO(-) ligand on the [RhI(3)(COCH(3))(CO)(2)](-) species followed by reductive elimination of acetic anhydride, which immediately reacts with water to afford acetic acid. 相似文献
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de Oliveira PR Rittner R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(5):1079-1086
(1)H NMR data for cis-3-n-propoxycyclohexanol (cis-3-PCH) and cis-3-isopropoxy-cyclohexanol (cis-3-ICH) show that a concentration increase shifts the conformational equilibrium from the diaxial (aa) conformer, stabilized by an intramolecular hydrogen bond (IAHB), to the diequatorial (ee) conformer [X(ee)=42% and 21% (at 0.01molL(-1)) to 58% and 56% (at 0.40molL(-1)), in CCl(4,) respectively] due to intermolecular hydrogen bonds (IEHB), as confirmed by IR data. The Deltanu values, obtained by IR spectra, indicated that increasing the size of the OR group [R=CH(3), CH(2)CH(2)CH(3) and CH(CH(3))(2)], increases the IAHB strength, due to an increase in the inductive effect of R group, which makes the oxygen lone pairs more available for an IAHB with OH group, in opposition to the steric effect. The percentage of ee conformer increases with the solvent basicity for cis-3-PCH and cis-3-ICH, from 48% and 36% in CCl(4) to 97% and 96% in DMSO, respectively. Values of 4.58, 6.06 and 6.33kcalmol(-1) for the IAHB strength in cis-3-PCH, cis-3-ICH and cis-3-TCH (cis-3-tert-butoxycyclohexanol), respectively, were obtained, from the theoretical data through the CBS-4M method, confirming the experimental results and indicating that the IAHB strength increases with the increasing bulk of OR substituent in this series of compounds. 相似文献
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Condensation of 3-methyl-3-buten-1-ol with pentanal or acetone occurs on metal salt surfaces at room temperature to give di- and tetrahydropyrans.For Communication 2, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1019–1021, August, 1990. 相似文献
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《Tetrahedron》1987,43(7):1635-1642
Irradiation of acrolein vapors in the presence of films of nickel and other metals results in the formation of thin films of polyacrolein on the metal surface. The polyarcrolein film protects the metal surface from abrasion and corrosion. Polymer growth is more rapid on oxidized vs. unoxidized metal surfaces indicating a role for surface oxide sites in the polymerization process. Several other monomers investigated fail to form adhesive polymer films on metal films, but can be copolymerized with acrolein. 相似文献
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A. Ya. Tontegode 《Progress in Surface Science》1991,38(3-4):201-429
The review surveys the conditions of formation and properties of four forms of surface carbon on transition metals, to wit, adsorbed atoms and clusters, surface carbide and graphite, and their role in the physical and chemical processes on the surface. The first-order phase transition in the adlayer, when graphite islands coexist with carbon gas, are considered. The effect of intercalation, when atoms (Cs, K, Na, Ba, Pt, Si) penetrate spontaneously under the graphite islands physisorbed on the metal, and its mechanism are discussed. An analysis is made of the poisoning of platinum-group metal catalysts in the reaction of dissociation, when graphite islands characterized by extreme adsorption and catalytic passivity form in the adlayer. The method of CsCl dissociation to probe the surface carbon is treated. Attention is drawn to the adsorption of a number of atoms (Cs, K, Ba, Pt) on a graphite monolayer on metals, and the properties of such systems are discussed. The effects observed in coadsorption of CsCl molecules with K, Na, Ba, Tm atoms on a graphite monolayer on metals are covered. By analogy with the bulk carbides, surface carbides of fixed stoichiometry and very strong metal-carbon bonding have been revealed to form on the surface of transition metals (W, Re, Mo). The effect of displacement of surface carbon into the bulk of the metal stimulated by the adsorption of some atoms (Si, S, O) is discussed. The carbon clusters adsorbed on metals are considered. The transport of surface carbon, its desorption and diffusion between the surface and the bulk of the metal with a single- and double-phase adlayer are reviewed. 相似文献
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《Journal of organometallic chemistry》2001,628(2):222-232
Reductive elimination, the final step of the Monsanto and Cativa processes, has been studied using the density functional theory with the hybrid B3LYP exchange and correlation functional. To our knowledge, this is the first systematic computational study of the reductive elimination for which even the experimental studies are rare. We have studied different isomers of the anionic dicarbonyls [Rh(CO)2(COCH3)I3]− (1) and [Ir(CO)2(COCH3)I3]− (2). Several possible reaction routes for the elimination of CH3COI from 1 and 2 have been explored. In addition, different isomers of the neutral tricarbonyl [Ir(CO)3(COCH3)I2] (3) and possible reaction paths connected to 3 have been studied. Our results show mer,trans-1 to be the dominant intermediate in the rhodium system although its transformation to fac,cis-1 and the elimination from this seems to be the most likely reaction pathway. In the anionic iridium system, the dominating intermediate is proposed to be fac,cis-2. In the neutral iridium system, mer,cis-3 is proposed to be the dominant intermediate. While inspecting the iridium system as a whole, one could propose a transformation from anionic dicarbonyl to neutral tricarbonyl that would enhance the total rate of the reductive elimination. This observation is similar to that already verified in the 1,1-insertion in the Cativa process. In general, the geometrical arrangement of the different ligands has a large effect on the catalytic activity of the different possible intermediates of these processes. 相似文献
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Kunio Mori Akira Watanabe Aikou Muroi Yoshiro Nakamura 《Journal of polymer science. Part A, Polymer chemistry》1987,25(10):2893-2907
The three kinds of monomer films on metal surfaces were deposited by adsorption from a solution of 6-polymerizable substituents-1,3,5-triazine-2,4-dithiol monosodium salts (RTDN); the polymerizable substituents such as cis-9-octadecenylamino, di(cis-9-octadecenyl)amino, and p-vinylbenzyl(cis-9-octadecenyl)amino groups were selected in view of the polymerization activity of unsaturated groups in the substituents and the packing degree of monomer molecules. The monomer films were estimated to consist of mainly 6-substituents-1,3,5,-triazine-2,4-dithione (3H, 5H) and to be multimolecular layers that are considerably cross-packed and ordered. The monomer films on metal surfaces were polymerizable under a UV light irradiation in air atmosphere to give polymer films. In the photopolymerization, azobis(isobutyronitrile) (AIBN) was very effective for increasing the monomer conversion and the polymerization rate. The optimum concentration of AIBN in monomer films was very small, about 0.025 mol %. The monomer conversion was influenced by the kind of monomers, namely, the polymerization activity and the packing degree. The effect of the packing degree was especially remarkable. The monomer conversion decreased with an increase in the thickness of monomer films. This is because the polymerization was initiated by oxygen and AIBN, which were diffused into the inner of monomer films. The possibility of polymerization of the unsaturated groups and the thione groups in monomer molecules under UV light irradiation is discussed. 相似文献
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《Materials Chemistry》1977,2(3):113-119
The analysis of the properties of cold welded metallic junctions as monitored by contact resistance measurements is extended to include the effects of impurities. Brittle fracture of both iron and copper similar metal, cold welded junctions was observed. This is in marked contrast to the bulk properties of these materials. It is believed the fracture properties of these materials were influenced by impurities embrittling the junctions. If impurities caused this behavior, the surface energy would consequently be lowered by these impurities and evidence of this is noted. 相似文献
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A general and efficient palladium-catalyzed reductive carbonylation with low catalyst loadings (0.5 mol % Pd or below) has been developed. The formylation of aryl and heteroaryl bromides proceeds smoothly in the presence of palladium/di-1-adamantyl-n-butylphosphine at ambient pressure of synthesis gas to afford the corresponding aromatic aldehydes in good yields and excellent selectivity. In addition, vinyl halides react under similar conditions to form α,β-unsaturated aldehydes in good yield. 相似文献
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S. Tsuji I.S.T. Tsong S.V. Krishnaswamy 《Spectrochimica Acta Part B: Atomic Spectroscopy》1981,36(10):1005-1014
Spectral scans of 12 metals: Al, Co, Cr, Cu, Fe, Mg, Mo, Ni, Pd, Si, Ti and W under Ar+ ion bombardment have been taken with and without backfilled oxygen in the target chamber to study the effect of oxygen on the emission of continuum radiation. Some of the observed broad band features can be attributed to sputtered metal-oxide molecular emission while other continua remain unidentified. In all cases except Pd, increasing the partial pressure of oxygen enhances the continuum emission. 相似文献