共查询到20条相似文献,搜索用时 15 毫秒
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Jędrzej Wysocki Dr. Nuria Ortega Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2014,53(33):8751-8755
An enantioselective hydrogenation of disubstituted furans has been developed by using a chiral ruthenium catalyst with N‐heterocyclic carbene ligands. This reaction converts furans into valuable enantioenriched disubstituted tetrahydrofurans. 相似文献
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Raphael Bigler Kyle A. Mack Jeff Shen Paolo Tosatti Chong Han Stephan Bachmann Haiming Zhang Michelangelo Scalone Andreas Pfaltz Scott E. Denmark Stefan Hildbrand Francis Gosselin 《Angewandte Chemie (International ed. in English)》2020,59(7):2844-2849
Asymmetric hydrogenation has evolved as one of the most powerful tools to construct stereocenters. However, the asymmetric hydrogenation of unfunctionalized tetrasubstituted acyclic olefins remains the pinnacle of asymmetric synthesis and an unsolved challenge. We report herein the discovery of an iridium catalyst for the first, generally applicable, highly enantio‐ and diastereoselective hydrogenation of such olefins and the mechanistic insights of the reaction. The power of this chemistry is demonstrated by the successful hydrogenation of a wide variety of electronically and sterically diverse olefins in excellent yield and high enantio‐ and diastereoselectivity. 相似文献
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In this review article recent developments in the asymmetric transfer hydrogenation of imines from 2008 up to today are presented. The main methodology involves either metal‐catalyzed procedures in the presence of a chiral ligand or organocatalyzed technologies using a Hantzsch ester and a chiral BINOL‐derived phosphoric acid. The most important procedures are collected, paying special attention to the application of this methodology in synthetic organic chemistry.
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M. Belén Díaz-Valenzuela Dr. Scott D. Phillips Marcia B. France Prof. Mary E. Gunn Matthew L. Clarke Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(5):1227-1232
A study on the enantioselective hydrogenation of tertiary alkyl ketones catalysed by a novel class of tridentate–Ru complex is reported. In contrast to the extensively studied [RuCl2(diphos)(di-primary amine)] complexes, this new class of hydrogenation catalyst smoothly reduces these less reactive bulky ketones with up to 94 % ee. The same catalyst system can also selectively reduce other potentially problematic substrates such as bulky heterocyclic ketones. Unusually for a pressure hydrogenation catalyst, similar enantioselectivity can be obtained under transfer hydrogenation conditions. The transfer hydrogenations are somewhat slower than the pressure hydrogenations, but this drawback is readily overcome, since we have discovered that a microwave accelerated transfer hydrogenation of the above ketones occurs within 20 min at about 90 °C with similar selectivity to that obtained in the pressure hydrogenation system. 相似文献
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Alejandro Baeza Dr. Andreas Pfaltz Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(13):4003-4009
We have evaluated a wide range of iridium complexes derived from chiral oxazoline‐based N,P ligands for the asymmetric hydrogenation of imines and identified three efficient catalysts. These catalysts are readily synthesized by straightforward convenient routes and are air and moisture stable. In the reduction of acetophenone N‐arylimines and related acyclic substrates, excellent enantioselectivities (up to 96 % ee) were obtained by using 0.1–0.5 mol % of catalyst at ?20 °C and 5–50 bar hydrogen pressure. 相似文献
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Dr. Jacorien Coetzee Dr. Deborah L. Dodds Prof. Jürgen Klankermayer Sandra Brosinski Prof. Walter Leitner Prof. Alexandra M. Z. Slawin Prof. David J. Cole‐Hamilton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(33):11039-11050
Hydrogenation of amides in the presence of [Ru(acac)3] (acacH=2,4‐pentanedione), triphos [1,1,1‐tris‐ (diphenylphosphinomethyl)ethane] and methanesulfonic acid (MSA) produces secondary and tertiary amines with selectivities as high as 93 % provided that there is at least one aromatic ring on N. The system is also active for the synthesis of primary amines. In an attempt to probe the role of MSA and the mechanism of the reaction, a range of methanesulfonato complexes has been prepared from [Ru(acac)3], triphos and MSA, or from reactions of [RuX(OAc)(triphos)] (X=H or OAc) or [RuH2(CO)(triphos)] with MSA. Crystallographically characterised complexes include: [Ru(OAc‐κ1O)2(H2O)(triphos)], [Ru(OAc‐κ2O,O′)(CH3SO3‐κ1O)(triphos)], [Ru(CH3SO3‐κ1O)2(H2O)(triphos)] and [Ru2(μ‐CH3SO3)3(triphos)2][CH3SO3], whereas other complexes, such as [Ru(OAc‐κ1O)(OAc‐κ2O,O′)(triphos)], [Ru(CH3SO3‐κ1O)(CH3SO3‐κ2O,O′)(triphos)], H[Ru(CH3SO3‐κ1O)3(triphos)], [RuH(CH3SO3‐κ1O)(CO)(triphos)] and [RuH(CH3SO3‐κ2O,O′)(triphos)] have been characterised spectroscopically. The interactions between these various complexes and their relevance to the catalytic reactions are discussed. 相似文献
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Dr. Maurizio Bernasconi Marc‐André Müller Prof. Dr. Andreas Pfaltz 《Angewandte Chemie (International ed. in English)》2014,53(21):5385-5388
Asymmetric hydrogenation of maleic and fumaric acid derivatives with iridium catalysts based on N,P ligands provides an efficient route to chiral enantioenriched succinates. A new catalyst derived from a 2,6‐difluorophenyl‐substituted pyridine‐phosphinite ligand was developed and enables the conversion of a wide range of 2‐alkyl and 2‐arylmaleic acid diesters into the corresponding succinates in high enantiomeric purity. Mixtures of cis/trans substrates can be hydrogenated in an enantioconvergent fashion with high enantioselectivity, and further enhances the scope of this transformation. The products are valuable chiral building blocks with a structural motif found in many bioactive compounds, such as metalloproteinase inhibitors. 相似文献
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Christian A. Sandoval Prof. Dr. Yuehui Li Kuiling Ding Prof. Dr. Ryoji Noyori Prof. Dr. 《化学:亚洲杂志》2008,3(10):1801-1810
Chiral binap/pica‐RuII complexes (binap=(S)‐ or (R)‐2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl; pica=α‐picolylamine) catalyze both asymmetric hydrogenation (AH) of ketones using H2 and asymmetric transfer hydrogenation (ATH) using non‐tertiary alcohols under basic conditions. The AH and ATH catalytic cycles are linked by the metal–ligand bifunctional mechanism. Asymmetric reduction of pinacolone is best achieved in ethanol containing the Ru catalyst and base under an H2 atmosphere at ambient temperature, giving the chiral alcohol in 97–98 % ee. The reaction utilizes only H2 as a hydride source with alcohol acting as a proton source. On the other hand, asymmetric reduction of acetophenone is attained with both H2 (ambient temperature) and 2‐propanol (>60 °C) with relatively low enantioselectivity. The degree of contribution of the AH and ATH cycles is highly dependent on the ketone substrates, solvent, and reaction parameters (H2 pressure, temperature, basicity, substrate concentration, H/D difference, etc.). 相似文献
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Yao Ge Dr. Zhaobin Han Dr. Zheng Wang Chen‐Guo Feng Qian Zhao Guo‐Qiang Lin Prof. Dr. Kuiling Ding 《Angewandte Chemie (International ed. in English)》2018,57(40):13140-13144
The first asymmetric hydrogenation of 3‐ylidenephthalides has been developed using the IrI complex of a spiro[4,4]‐1,6‐nonadiene‐based phosphine‐oxazoline ligand (SpinPHOX) as the catalyst, affording a wide variety of chiral 3‐substituted phthalides in excellent enantiomeric excesses (up to 98 % ee). The utility of the protocol has been demonstrated in the asymmetric synthesis of chiral drugs NBP and BZP precursor, as well as the natural products chuangxinol and typhaphthalide. 相似文献
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Prof. Ryoichi Kuwano Yuta Hashiguchi Ryuhei Ikeda Dr. Kentaro Ishizuka 《Angewandte Chemie (International ed. in English)》2015,54(8):2393-2396
The asymmetric hydrogenation of pyrimidines proceeded with high enantioselectivity (up to 99 % ee) using an iridium catalyst composed of [IrCl(cod)]2, a ferrocene‐containing chiral diphosphine ligand (Josiphos), iodine, and Yb(OTf)3 (cod=1,5‐cyclooctadiene). The chiral catalyst converted various 4‐substituted pyrimidines into chiral 1,4,5,6‐tetrahydropyrimidines in high yield. The lanthanide triflate is crucial for achieving the high enantioselectivity as well as for activating the heteroarene substrate. 相似文献
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Marc Renom‐Carrasco Piotr Gajewski Dr. Luca Pignataro Prof. Johannes G. de Vries Prof. Umberto Piarulli Prof. Cesare Gennari Dr. Laurent Lefort 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9528-9532
The use of an equivalent amount of an organic base leads to high enantiomeric excess in the asymmetric hydrogenation of N‐benzylated 3‐substituted pyridinium salts into the corresponding piperidines. Indeed, in the presence of Et3N, a Rh‐JosiPhos catalyst reduced a range of pyridinium salts with ee values up to 90 %. The role of the base was elucidated with a mechanistic study involving the isolation of the various reaction intermediates and isotopic labeling experiments. Additionally, this study provided some evidence for an enantiodetermining step involving a dihydropyridine intermediate. 相似文献
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Asymmetric Hydrogenation of Furans and Benzofurans with Iridium–Pyridine–Phosphinite Catalysts 下载免费PDF全文
Dr. Larissa Pauli Dr. René Tannert Robin Scheil Prof. Dr. Andreas Pfaltz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1482-1487
Enantioselective hydrogenation of furans and benzofurans remains a challenging task. We report the hydrogenation of 2‐ and 3‐substituted furans by using iridium catalysts that bear bicyclic pyridine–phosphinite ligands. Excellent enantioselectivities and high conversions were obtained for monosubstituted furans with a 3‐alkyl or 3‐aryl group. Furans substituted at the 2‐position and 2,4‐disubstituted furans proved to be more difficult substrates. The best results (80–97 % conversion, 65–82 % enantiomeric excess) were obtained with monosubstituted 2‐alkylfurans and 2‐[4‐(trifluoromethyl)phenyl]furan. Benzofurans with an alkyl substituent at the 2‐ or 3‐position also gave high conversions and enantioselectivity, whereas 2‐aryl derivatives showed essentially no reactivity. The asymmetric hydrogenation of a 3‐methylbenzofuran derivative was used as a key step in the formal total synthesis of the cytotoxic naphthoquinone natural product (?)‐thespesone. 相似文献