共查询到20条相似文献,搜索用时 15 毫秒
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Juan Almena Axel Monsees Renat Kadyrov ThomasH. Riermeier Battsengel Gotov Jens Holz Armin Brner 《Advanced Synthesis \u0026amp; Catalysis》2004,346(11):1263-1266
The new – commercially in multi‐kg quantities available – chiral bisphospholane ligand, catASium® M, has been successfully used in the Rh(I)‐catalysed enantioselective hydrogenation of itaconic acid derivatives. Chiral ß‐substituted succinic acid derivatives were produced in good to excellent enantioselectivities. Turnover frequencies by up to 40,000 h−1 have been achieved. 相似文献
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Nataa Mri Thomas Jerphagnon AdriaanJ. Minnaard BenL. Feringa JohannesG. de Vries 《Advanced Synthesis \u0026amp; Catalysis》2009,351(16):2549-2552
A catalyst made in situ from the (cyclooctadiene)iridium chloride dimer, [Ir(COD)Cl]2, and the monodentate phosphoramidite ligand (S)‐PipPhos was used in the enantioselective hydrogenation of 2‐ and 2,6‐substituted quinoxalines. In the presence of piperidine hydrochloride as additive full conversions and enantioselectivities of up to 96% are obtained. 相似文献
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Sean Newton Steven V. Ley Eva Casas Arc Damian M. Grainger 《Advanced Synthesis \u0026amp; Catalysis》2012,354(9):1805-1812
In this update, the asymmetric homogeneous hydrogenation of a number of trisubstituted olefins utilizing the recently developed tube‐in‐tube gas‐liquid flow reactor is described. A number of chiral iridium‐ and rhodium‐based catalysts and other parameters such as pressure, solvent, temperature and catalyst loading were screened. The advantage of the flow set‐up for rapid screening and optimization of reaction parameters is illustrated. Furthermore, a comparative study using batch conditions aided in the optimization of the flow reaction set‐up. The set‐up was further modified to recycle the catalyst which prolonged catalytic activity. 相似文献
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Nadine Krber Frank Rominger Thomas J.J. Müller 《Advanced Synthesis \u0026amp; Catalysis》2009,351(17):2921-2935
Linear, easily accessible alkyl and (hetero)aryl‐substituted alkynyl allyl alcohols are readily and enantioselectively transformed into 2,7‐dioxabicyclo[3.2.1]octanes by a sequential rhodium‐catalyzed process. Based on the initial cycloisomerization, the in situ generated rhodium(I)‐BINAP complex enables a subsequent reduction with hydrogen and the transformation into bicyclic frameworks. 相似文献
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Borut Zupan
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Barbara Mohar Michel Stephan 《Advanced Synthesis \u0026amp; Catalysis》2008,350(13):2024-2032
The introduction of 1,2‐bis[(o‐anisyl)(phenyl)phosphino]ethane (DiPAMP) as a P‐stereogenic ligand for rhodium(I)‐catalyzed hydrogenation by Knowles et al. came after their evaluation of several diphosphines. However, no in‐depth study was carried out on incorporating various substituents on its P‐o‐anisyl groups. In this work, we have prepared a large series of enantiopure and closely related DiPAMP analogues possessing various substituents (MeO, TMS, t‐Bu, Ph, fused benzene ring) on the o‐anisyl rings. The new ligands were evaluated in rhodium‐catalyzed hydrogenation of several model substrates: methyl α‐acetamidoacrylate, methyl (Z)‐α‐acetamidocinnamate, methyl (Z)‐β‐acetamidocrotonate, dimethyl itaconate, and atropic acid. They displayed enhanced activities and increased enantioselectivities, particularly the P‐(2,3,4,5‐tetra‐MeO‐C6H)‐substituted ligand (4MeBigFUS). Interestingly enough, 88% ee was obtained in the hydrogenation of atropic acid using the Rh‐(4MeBigFUS) catalyst under mild conditions (10 bar H2, room temperature) versus 7% ee using Rh‐DiPAMP. Conversely, the ligand possessing P‐(2,6‐di‐MeO‐C6H3) groups proved to slow down considerably the hydrogenation. X‐Ray structures of their corresponding Rh complexes are presented and discussed. 相似文献
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Kathrin Kutlescha Torsten Irrgang Rhett Kempe 《Advanced Synthesis \u0026amp; Catalysis》2010,352(18):3126-3130
Novel N,N,P ligand stabilized rhodium complexes exhibiting high activities and enantioselectivities in the asymmetric hydrogenation of N‐aryl imines are introduced. The ligands were synthesized from inexpensive starting materials and their modular design allows for the introduction of a broad variety of substitution patterns. Additionally, a rather low catalyst loading could be employed. 相似文献
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Michel Stephan Damjan terk Barbara Mohar 《Advanced Synthesis \u0026amp; Catalysis》2009,351(17):2779-2786
Switching Knowles DiPAMP’s {DiPAMP=1,2‐bis[(o‐anisyl)(phenyl)phosphino]‐ ethane} MeO groups with i‐PrO ones led to the i‐Pr‐SMS‐Phos {i‐Pr‐SMS‐Phos=1,2‐bis[(o‐isoprop‐ oxyphenyl)(phenyl)phosphino]ethane} ligand which displayed a boosted catalyst activity coupled with an enhanced enantioselectivity in the rhodium(I)‐catalyzed hydrogenation of a wide‐range of representative olefinic substrates (dehydro‐α‐amido acids, itaconates, acrylates, enamides, enol acetates, α,α‐diarylethylenes, etc). The rhodium(I)‐(i‐Pr‐SMS‐Phos) catalytic profile was investigated revealing its structural attributes and robustness, and in contrast to the usual trend, 31P NMR analysis revealed that its methyl (Z)‐α‐acetamidocinnamate (MAC) adduct consisted of a reversed diastereomeric ratio of 1.4:1 in favour of the most reactive diastereomer. 相似文献
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Xiang‐Hong Huo Jian‐Hua Xie Qiu‐Shi Wang Qi‐Lin Zhou 《Advanced Synthesis \u0026amp; Catalysis》2007,349(16):2477-2484
A racemic 1,1′ ‐ spirobitetralin‐8,8′‐diol (SBITOL) was conveniently synthesized from 3‐methoxybenzaldehyde in 26 % yield over 9 steps and resolved via its bis‐(S)‐camphorsulfonates. The corresponding chiral spirobitetraline monophosphoramidite ligands have been prepared and their rhodium complexes were applied in the asymmetric hydrogenation of dehydroamino esters with good to excellent enantioselectivities (up to 99.3 % ee). 相似文献
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Hctor Fernndez‐Prez MiquelA. Perics Anton Vidal‐Ferran 《Advanced Synthesis \u0026amp; Catalysis》2008,350(13):1984-1990
The preparation of a library of new P‐O‐P ligands (phosphine‐phosphites and phosphine‐phosphinites), easily available in two synthetic steps from enantiopure Sharpless epoxy ethers, is reported. The “lead” catalyst of the series has proven to have outstanding catalytic properties in the rhodium‐catalysed asymmetric hydrogenation of a wide variety of functionalised alkenes (16 examples). The excellent performance and modular design of the catalysts makes them attractive for future applications. 相似文献
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Jeroen Wassenaar Mark Kuil Joost N.H. Reek 《Advanced Synthesis \u0026amp; Catalysis》2008,350(10):1610-1614
(S)‐3‐Hydroxy‐2‐methylpropionate, known as the Roche ester, and several of its derivatives were successfully synthesized through asymmetric rhodium‐catalyzed hydrogenation, using INDOLPHOS (diisopropyl{1‐[(S)‐3,5‐dioxa‐4‐phosphacyclohepta[2,1‐a;3,4‐a′]dinaphthalen‐4‐yl]‐3‐methyl‐2‐indolyl}phosphine) as the chiral ligand, in excellent yield and the highest ee reported up to now (TOF over 5500 h−1 at 25 °C; up to 98% ee at −40 °C). 相似文献
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Marc Renom‐Carrasco Piotr Gajewski Luca Pignataro Johannes G. deVries Umberto Piarulli Cesare Gennari Laurent Lefort 《Advanced Synthesis \u0026amp; Catalysis》2016,358(16):2589-2593
Herein we describe a new methodology for the asymmetric hydrogenation (AH) of 2‐substituted pyridinium salts. An iridium catalyst based on a mixture of a chiral monodentate phosphoramidite and an achiral phosphine was shown to hydrogenate N‐benzyl‐2‐arylpyiridinium bromides to the corresponding N‐benzyl‐2‐arylpiperidines with full conversion and good enantioselectivity. The mechanism of the reaction under optimized conditions was investigated via kinetic measurements and isotopic labeling experiments. Our study suggests that the hydrogenation starts with a 1,4‐hydride addition and that the enantiodiscriminating step involves the reduction of an iminium intermediate.
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A new class of low‐cost and easy‐to‐prepare monodentate phosphoramidite ligands (CydamPhos) has been developed from readily accessible and cheap trans‐1,2‐diaminocyclohexane as starting material through a three‐step transformation. This type of ligands exhibited excellent enantioseletivities and high activities in rhodium(I)‐catalyzed asymmetric hydrogenations of dehydro‐α‐amino acid methyl esters 9 (ee: 96.2–99.8 %) and acetylenamides 11 (91.8–98.8 %). The remarkable substituent effects exhibited by the ligands on the enantioselective control of the catalysis are rationalized on the basis of molecular structure of the catalyst precursor. 相似文献
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NataliaV. Dubrovina IvanA. Shuklov Mandy‐Nicole Birkholz Dirk Michalik Rocco Paciello Armin Brner 《Advanced Synthesis \u0026amp; Catalysis》2007,349(13):2183-2187
We herein describe the beneficial effect of fluorinated alcohols on asymmetric hydrogenation using chiral self‐assembling rhodium complexes. Previously, the application of these catalysts has been hampered by low reaction rates in non‐polar solvents, which are essential for establishing the self‐assembling architecture via hydrogen bonding. Excellent reaction rates are usually observed in alcohols as solvents, but the characteristic hydrogen bonds are cleaved in those media, resulting in poor ee values. We now show for the first time that the disadvantageous properties of both solvent classes on the catalytic reaction can be overcome by using fluorinated alcohols. Due to this key finding, homogeneous catalysis with self‐assembling catalysts is much closer to practical application. 相似文献
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Philippe Dupau Christian Bruneau Pierre H. Dixneuf 《Advanced Synthesis \u0026amp; Catalysis》2001,343(4):331-334
The enantioselective hydrogenation of enamides bearing an endocyclic tetrasubstituted carbon‐carbon double bond has been performed in the presence of ruthenium catalyst precursors prepared from Ru(cod)(methallyl)2, Duphos, or BPE as optically active ligand and HBF4. This promising catalytic system makes possible the selective cis‐hydrogenation with satisfactory enantioselectivities (up to 72% ee) for this type of tetrasubstituted double bonds. 相似文献