排序方式: 共有73条查询结果,搜索用时 31 毫秒
41.
Védaste Kagisha Egide Kayitare Claver Kayumba Pierre Kaale Eliangiringa 《平面色谱法杂志一现代薄层色谱法》2014,27(5):392-397
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
42.
S Deerenberg O Pàmies M Diéguez C Claver P C Kamer P W van Leeuwen 《The Journal of organic chemistry》2001,66(23):7626-7631
We have investigated a series of enantiopure phosphine-phosphite ligands (P(1)-P(2) = ligands 1-4) in the rhodium-catalyzed asymmetric hydrogenation reaction. Intermediate [Rh(P(1)-P(2))(cod)]BF(4) and [Rh(P(1)-P(2))(5)]BF(4) complexes (cod = 1,5-cyclooctadiene; 5 = methyl acetamidoacrylate ester) were observed by (31)P[(1)H] NMR. The [Rh(P(1)-P(2))(cod)]BF(4) complexes were precursors to active catalysts of the asymmetric hydrogenation reaction of several prochiral dehydroamino acid derivatives under mild reaction conditions (1 bar of hydrogen and 20 degrees C). The enantiomeric excess reached up to 99%. 相似文献
43.
Crozet D Gual A McKay D Dinoi C Godard C Urrutigoïty M Daran JC Maron L Claver C Kalck P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(23):7128-7140
The reactivity of [Rh(CO)(2){(R,R)-Ph-BPE}]BF(4) (2) toward amine, CO and/or H(2) was examined by high-pressure NMR and IR spectroscopy. The two cationic pentacoordinated species [Rh(CO)(3) {(R,R)-Ph-BPE}]BF(4) (4) and [Rh(CO)(2)(NHC(5)H(10)){(R,R)-Ph-BPE}]BF(4) (8) were identified. The transformation of 2 into the neutral complex [RhH(CO)(2){(R,R)-Ph-BPE}] (3) under hydroaminomethylation conditions (CO/H(2), amine) was investigated. The full mechanisms related to the formation of 3, 4 and 8 starting from 2 are supported by DFT calculations. In particular, the pathway from 2 to 3 revealed the deprotonation by the amine of the dihydride species [Rh(H)(2)(CO)(2){(R,R)-Ph-BPE}]BF(4) (6), resulting from the oxidative addition of H(2) on 2. 相似文献
44.
Bianchini C Brüggeller P Claver C Czermak G Dumfort A Meli A Oberhauser W Garcia Suarez EJ 《Dalton transactions (Cambridge, England : 2003)》2006,(24):2964-2973
The bis-cationic diphosphonium-diphosphine 6,7-di(di-2-methoxyphenyl)phosphinyl-2,2,4,4-tetra(di-2-methoxyphenyl)-2 lambda 4,4 lambda 4-diphosphoniumbicyclo[3.1.1]heptane-bis(PF6) ((o-MeO-PCP)(PF6)2) and the diphosphine rac-2,4-bis((di-2-methoxyphenyl)phosphino)pentane (rac-o-MeO-bdpp) have been synthesized. Both ligands have been employed to coordinate PdCl2 and Pd(OAc)2 to give [PdCl2(o-MeO-PCP)](PF6)2 (1a), PdCl2(rac-o-MeO-bdpp) (1b), [Pd(OAc)2(o-MeO-PCP)](PF6)2 (2a) and Pd(OAc)2(rac-o-MeO-bdpp) (2b). The ligands and complexes have been fully characterized in solution by multinuclear NMR spectroscopy. In addition, 1a and 1b have been authenticated by single crystal X-ray structure analyses. The Pd(II) complexes 1a and 1b have been employed as catalyst precursors for the CO/ethene copolymerisation in water-acetic acid mixtures, while 2a and 2b have been tested in methanol in the presence of p-toluenesulfonic acid. Irrespective of the reaction media, perfectly alternating polyketones were obtained in excellent yields and with number-average molecular weights ranging from 7.1-13.9 kg mol(-1) with the diphosphonium-diphosphine catalysts and from 37.2-48.2 kg mol(-1) with the diphosphine catalysts. 相似文献
45.
Diego A. Lomelí-Rosales Dr. Jorge A. Delgado Dr. Miriam Díaz de los Bernardos Dr. Sara Pérez-Rodríguez Dr. Aitor Gual Prof. Carmen Claver Prof. Cyril Godard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(35):8321-8331
A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction. 相似文献
46.
A series of novel diphosphite ligands derived from readily available D-(+)-glucose have been synthesized. These ligands were screened in the Rh-catalyzed hydrogenation of a series of alpha,beta-unsaturated carboxylic acid derivatives. Both excellent enantioselectivities (ee up to >99%) and activities were achieved. The advantage of these ligands is that their modular nature allows an easy systematic variation in the configuration of the stereocenters (C-3, C-5) at the ligand backbone and in the biaryl substituents, so the optimum configuration for maximum enantioselectivity in asymmetric hydrogenation can be determined. Results show that enantiomeric excesses depend strongly on the absolute configuration of C-3 and slightly on the stereocenter carbon C-5, while the sense of the enantiodiscrimination is predominantly controlled by the configuration of the biaryls at the phosphite moieties. Moreover, the presence of bulky substituents at the ortho-positions of the biaryl diphosphite moieties has a positive effect on enantioselectivity. 相似文献
47.
Enantioselective access to Markovnikov regioisomeric perfluoroalcohols is achieved in the presence of chiral cationic rhodium complexes and specific hydroborating reagents. 相似文献
48.
Fran?ois-Thomas Michaud Pierre Claver Havugimana Carl Duchesne Fran?ois Sanschagrin Alice Bernier Roger C. Lévesque Alain Garnier 《Applied biochemistry and biotechnology》2012,167(3):474-488
Liquid chromatography mass spectrometry (LCMS) is a powerful technique that could serve to rapidly characterize cell culture protein expression profile and be used as a process monitoring and control tool. However, this application is often hampered by both the sample proteome and the LCMS signal complexities as well as the variability of this signal. To alleviate this problem, culture samples are usually extensively fractionated and pretreated before being analyzed by top-end instruments. Such an approach precludes LCMS usage for routine on-line or at-line application. In this work, by applying multivariate analysis (MA) directly on raw LCMS signals, we were able to extract relevant information from cell culture samples that were simply lyzed. By using the recombinant adenovirus production process as a model, we were able to follow the accumulation of the three major proteins produced, identified their accumulation dynamics, and draw useful conclusions from these results. The combination of LCMS and MA provides a simple, rapid, and precise means to monitor cell culture. 相似文献
49.
Miguel Rosales‐Guzmán Roberto Alexander‐Katz Patricia Castillo‐Ocampo Alejandro Vega‐Ríos Angel Licea‐Claveríe 《Journal of Polymer Science.Polymer Physics》2013,51(18):1368-1376
Three diblock copolymers of polystyrene‐b‐poly(N‐isopropylacrylamide) (PS‐b‐PNIPAM) were prepared by reversible addition‐fragmentation chain transfer technique (RAFT) with compositions fPS = 0.84, fPS = 0.29, and fPS = 0.33. Block copolymers rich in PNIPAM were blended with polystyrene and its morphological effects were studied. The morphology of thin films was induced by acetone vapor and determined in the dried state by means of TEM. Copolymers with fPS = 0.84 and fPS = 0.29 form hexagonally packed cylinder (HPC) morphologies while that with fPS = 0.33 corresponds to a lamellar structure. In almost all cases where PNIPAM constitutes the continuous phase, a contraction of the PNIPAM blocks with respect to their average unperturbed dimension was observed, contrary to what one expects from the physics of self‐assembly of block copolymers. In contrast, for HPC morphology where PNIPAM is confined in a PS matrix, both blocks are highly extended. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1368–1376 相似文献
50.
A new class of efficient catalysts was developed for the asymmetric hydrogenation of alpha,beta-unsaturated carboxylic acid derivatives by synthesizing a series of novel phosphine-phosphite ligands (4a-d) derived from readily available D-(+)-xylose. Excellent enantioselectivities (> 99%) were achieved under very mild reaction conditions (1 bar H(2) and 20 degrees C). Varying the biphenyl substituents in the phosphite moiety greatly affected the enantioselectivity in the hydrogenation reactions. The results also indicate that the sense of enantioselectivity is mainly controlled by the configuration of the phosphite moiety. (31)P[(1)H] NMR and kinetic studies on intermediates of the catalytic cycle show that the [Rh(P(1)-P(2))(enamide)]BF(4) species is the resting state and that the rate dependence is first order in rhodium and hydrogen pressure and zero order in enamide concentration. 相似文献