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1.
Asymmetric Radical–Radical Cross‐Coupling through Visible‐Light‐Activated Iridium Catalysis
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Chuanyong Wang Jie Qin Xiaodong Shen Radostan Riedel Dr. Klaus Harms Prof. Dr. Eric Meggers 《Angewandte Chemie (International ed. in English)》2016,55(2):685-688
Combining single electron transfer between a donor substrate and a catalyst‐activated acceptor substrate with a stereocontrolled radical–radical recombination enables the visible‐light‐driven catalytic enantio‐ and diastereoselective synthesis of 1,2‐amino alcohols from trifluoromethyl ketones and tertiary amines. With a chiral iridium complex acting as both a Lewis acid and a photoredox catalyst, enantioselectivities of up to 99 % ee were achieved. A quantum yield of <1 supports the proposed catalytic cycle in which at least one photon is needed for each asymmetric C? C bond formation mediated by single electron transfer. 相似文献
2.
A Rhodium Catalyst Superior to Iridium Congeners for Enantioselective Radical Amination Activated by Visible Light
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Xiaodong Shen Dr. Klaus Harms Michael Marsch Prof. Dr. Eric Meggers 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(27):9102-9105
A bis‐cyclometalated rhodium(III) complex catalyzes a visible‐light‐activated enantioselective α‐amination of 2‐acyl imidazoles with up to 99 % yield and 98 % ee. The rhodium catalyst is ascribed a dual function as a chiral Lewis acid and, simultaneously, as a light‐activated smart initiator of a radical‐chain process through intermediate aminyl radicals. Notably, related iridium‐based photoredox catalysts reported before were unsuccessful in this enantioselective radical C?N bond formation. The surprising preference for rhodium over iridium is attributed to much faster ligand‐exchange kinetics of the rhodium complexes involved in the catalytic cycle, which is crucial to keep pace with the highly reactive and thus short‐lived nitrogen‐centered radical intermediate. 相似文献
3.
Combining Photoredox‐Catalyzed Trifluoromethylation and Oxidation with DMSO: Facile Synthesis of α‐Trifluoromethylated Ketones from Aromatic Alkenes
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Ren Tomita Dr. Yusuke Yasu Dr. Takashi Koike Prof. Dr. Munetaka Akita 《Angewandte Chemie (International ed. in English)》2014,53(28):7144-7148
Trifluoromethylated ketones are useful building blocks for organic compounds with a trifluoromethyl group. A new and facile synthesis of ketones with a trifluoromethyl substituent in the α‐position proceeds through a one‐pot photoredox‐catalyzed trifluoromethylation–oxidation sequence of aromatic alkenes. Dimethyl sulfoxide (DMSO) serves as a key and mild oxidant under these photocatalytic conditions. Furthermore, an iridium photocatalyst, fac[Ir(ppy)3] (ppy=2‐phenylpyridine), turned out to be crucial for the present photoredox process. 相似文献
4.
Development of Chiral Spiro P‐N‐S Ligands for Iridium‐Catalyzed Asymmetric Hydrogenation of β‐Alkyl‐β‐Ketoesters
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Deng‐Hui Bao Hui‐Ling Wu Chao‐Lun Liu Prof. Jian‐Hua Xie Prof. Qi‐Lin Zhou 《Angewandte Chemie (International ed. in English)》2015,54(30):8791-8794
The chiral tridentate spiro P‐N‐S ligands (SpiroSAP) were developed, and their iridium complexes were prepared. Introduction of a 1,3‐dithiane moiety into the ligand resulted in a highly efficient chiral iridium catalyst for asymmetric hydrogenation of β‐alkyl‐β‐ketoesters, producing chiral β‐alkyl‐β‐hydroxyesters with excellent enantioselectivities (95–99.9 % ee) and turnover numbers of up to 355 000. 相似文献
5.
Octahedral Chiral‐at‐Metal Iridium Catalysts: Versatile Chiral Lewis Acids for Asymmetric Conjugate Additions
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Xiaodong Shen Haohua Huo Chuanyong Wang Bo Zhang Dr. Klaus Harms Prof. Dr. Eric Meggers 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9720-9726
Octahedral iridium(III) complexes containing two bidentate cyclometalating 5‐tert‐butyl‐2‐phenylbenzoxazole ( IrO ) or 5‐tert‐butyl‐2‐phenylbenzothiazole ( IrS ) ligands in addition to two labile acetonitrile ligands are demonstrated to constitute a highly versatile class of asymmetric Lewis acid catalysts. These complexes feature the metal center as the exclusive source of chirality and serve as effective asymmetric catalysts (0.5–5.0 mol % catalyst loading) for a variety of reactions with α,β‐unsaturated carbonyl compounds, namely Friedel–Crafts alkylations (94–99 % ee), Michael additions with CH‐acidic compounds (81–97 % ee), and a variety of cycloadditions (92–99 % ee with high d.r.). Mechanistic investigations and crystal structures of an iridium‐coordinated substrates and iridium‐coordinated products are consistent with a mechanistic picture in which the α,β‐unsaturated carbonyl compounds are activated by two‐point binding (bidentate coordination) to the chiral Lewis acid. 相似文献
6.
Ya Chen Yixiao Pan Yan‐Mei He Qing‐Hua Fan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(47):16987-16990
A highly enantioselective iridium‐ or ruthenium‐catalyzed intermolecular reductive amination/asymmetric hydrogenation relay with 2‐quinoline aldehydes and aromatic amines has been developed. A broad range of sterically tunable chiral N,N′‐diaryl vicinal diamines were obtained in high yields (up to 95 %) with excellent enantioselectivity (up to >99 % ee). The resulting chiral diamines could be readily transformed into sterically hindered chiral N‐heterocyclic carbene (NHC) precursors, which are otherwise difficult to access. The usefulness of this synthetic approach was further demonstrated by the successful application of one of the chiral vicinal diamines and chiral NHC ligands in a transition‐metal‐catalyzed asymmetric Suzuki–Miyaura cross‐coupling reaction and asymmetric ring‐opening cross‐metathesis, respectively. 相似文献
7.
An Iridium(I) N‐Heterocyclic Carbene Complex Catalyzes Asymmetric Intramolecular Allylic Amination Reactions
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Dr. Ke‐Yin Ye Qiang Cheng Dr. Chun‐Xiang Zhuo Prof. Li‐Xin Dai Prof. Dr. Shu‐Li You 《Angewandte Chemie (International ed. in English)》2016,55(28):8113-8116
A chiral iridium(I) N‐heterocyclic carbene complex was reported for the first time as the catalyst in the highly enantioselective intramolecular allylic amination reaction. The current method provides facile access to biologically important enantioenriched indolopiperazinones and piperazinones in good yields (74–91 %) and excellent enantioselectivities (92–99 % ee). Preliminary mechanistic investigations reveal that the C?H activation occurs at the position ortho to the N‐aryl group of the ligand. 相似文献
8.
Visible Light Activation of Boronic Esters Enables Efficient Photoredox C(sp2)–C(sp3) Cross‐Couplings in Flow
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Fabio Lima Dr. Mikhail A. Kabeshov Dr. Duc N. Tran Dr. Claudio Battilocchio Dr. Joerg Sedelmeier Dr. Gottfried Sedelmeier Dr. Berthold Schenkel Prof. Steven V. Ley 《Angewandte Chemie (International ed. in English)》2016,55(45):14085-14089
We report herein a new method for the photoredox activation of boronic esters. Using these reagents, an efficient and high‐throughput continuous flow process was developed to perform a dual iridium‐ and nickel‐catalyzed C(sp2)–C(sp3) coupling by circumventing solubility issues associated with potassium trifluoroborate salts. Formation of an adduct with a pyridine‐derived Lewis base was found to be essential for the photoredox activation of the boronic esters. Based on these results we were able to develop a further simplified visible light mediated C(sp2)–C(sp3) coupling method using boronic esters and cyano heteroarenes under flow conditions. 相似文献
9.
Dr. Jian‐Bo Xie Prof. Jian‐Hua Xie Xiao‐Yan Liu Qian‐Qian Zhang Prof. Qi‐Lin Zhou 《化学:亚洲杂志》2011,6(3):899-908
The iridium complexes of chiral spiro aminophophine ligands, especially the ligand with 3,5‐di‐tert‐butylphenyl groups on the P atom ( 1c ) were demonstrated to be highly efficient catalysts for the asymmetric hydrogenation of alkyl aryl ketones. In the presence of KOtBu as a base and under mild reaction conditions, a series of chiral alcohols were synthesized in up to 97 % ee with high turnover number (TON up to 10 000) and high turnover frequency (TOF up to 3.7×104 h−1). Investigation on the structures of the iridium complexes of ligands (R)‐ 1a and 1c by X‐ray analyses disclosed that the 3,5‐di‐tert‐butyl groups on the P‐phenyl rings of the ligand are the key factor for achieving high activity and enantioselectivity of the catalyst. Study of the catalysts generated from the Ir‐(R)‐ 1c complex and H2 by means of ESI‐MS and NMR spectroscopy indicated that the early formed iridium dihydride complex with one (R)‐ 1c ligand was the active species, which was slowly transformed into an inactive iridium dihydride complex with two (R)‐ 1c ligands. A plausible mechanism for the reaction was also suggested to explain the observations of the hydrogenation reactions. 相似文献
10.
Ming‐Sheng Xie Ye‐Fei Zhang Meng Shan Xiao‐Xia Wu Gui‐Rong Qu Hai‐Ming Guo 《Angewandte Chemie (International ed. in English)》2019,58(9):2839-2843
A DMAP‐N‐oxide, featuring an α‐amino acid as the chiral source, was developed, synthesized and applied in asymmetric Steglich rearrangement. A series of O‐acylated azlactones afforded C‐acylated azlactones possessing a quaternary stereocenter in high yields (up to 97 % yield) and excellent enantioselectivities (up to 97 % ee). Compared to the widespread use of pyridine nitrogen, which serves as the nucleophilic site in the asymmetric acyl transfer reaction, we discovered that chiral DMAP‐N‐oxides, in which the oxygen now acts as the nucleophilic site, are efficient acyl transfer catalysts. Our finding might open a new door for the development of chiral DMAP‐N‐oxides for asymmetric acyl transfer reactions. 相似文献
11.
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
12.
The common use of NHC complexes in transition‐metal mediated C–C coupling and metathesis reactions in recent decades has established N‐heterocyclic carbenes as a new class of ligand for catalysis. The field of asymmetric catalysis with complexes bearing NHC‐containing chiral ligands is dominated by mixed carbene/oxazoline or carbene/phosphane chelating ligands. In contrast, applications of complexes with chiral, chelating bis(NHC) ligands are rare. In the present work new chiral iridium(I) bis(NHC) complexes and their application in the asymmetric transfer hydrogenation of ketones are described. A series of chiral bis(azolium) salts have been prepared following a synthetic pathway, starting from L ‐valinol and the modular buildup allows the structural variation of the ligand precursors. The iridium complexes were formed via a one‐pot transmetallation procedure. The prepared complexes were applied as catalysts in the asymmetric transfer hydrogenation of various prochiral ketones, affording the corresponding chiral alcohols in high yields and moderate to good enantioselectivities of up to 68%. The enantioselectivities of the catalysts were strongly affected by the various, terminal N‐substituents of the chelating bis(NHC) ligands. The results presented in this work indicate the potential of bis‐carbenes as stereodirecting ligands for asymmetric catalysis and are offering a base for further developments. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
13.
Cationic Ir/Me‐BIPAM‐Catalyzed Asymmetric Intramolecular Direct Hydroarylation of α‐Ketoamides
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Tomohiko Shirai Prof. Dr. Hajime Ito Prof. Dr. Yasunori Yamamoto 《Angewandte Chemie (International ed. in English)》2014,53(10):2658-2661
Asymmetric intramolecular direct hydroarylation of α‐ketoamides gives various types of optically active 3‐substituted 3‐hydroxy‐2‐oxindoles in high yields with complete regioselectivity and high enantioselectivities (84–98 % ee). This is realized by the use of the cationic iridium complex [Ir(cod)2](BArF4) and the chiral O‐linked bidentate phosphoramidite (R,R)‐Me‐BIPAM. 相似文献
14.
Asymmetric Ring‐Opening of Cyclopropyl Ketones with Thiol,Alcohol, and Carboxylic Acid Nucleophiles Catalyzed by a Chiral N,N′‐Dioxide–Scandium(III) Complex
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Yong Xia Dr. Lili Lin Fenzhen Chang Xuan Fu Prof. Dr. Xiaohua Liu Prof. Dr. Xiaoming Feng 《Angewandte Chemie (International ed. in English)》2015,54(46):13748-13752
A highly efficient asymmetric ring‐opening reaction of cyclopropyl ketones with a broad range of thiols, alcohols and carboxylic acids has been first realized by using a chiral N,N′‐dioxide–scandium(III) complex as catalyst. The corresponding sulfides, ethers, and esters were obtained in up to 99 % yield and 95 % ee. This is also the first example of one catalytic system working for the ring‐opening reaction of donor–acceptor cyclopropanes with three different nucleophiles, let alone in an asymmetric version. 相似文献
15.
Oxydifluoromethylation of Alkenes by Photoredox Catalysis: Simple Synthesis of CF2H‐Containing Alcohols
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Yusuke Arai Ren Tomita Gaku Ando Dr. Takashi Koike Prof. Dr. Munetaka Akita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1262-1265
We have developed a novel and simple protocol for the direct incorporation of a difluoromethyl (CF2H) group into alkenes by visible‐light‐driven photoredox catalysis. The use of fac‐[Ir(ppy)3] (ppy=2‐pyridylphenyl) photocatalyst and shelf‐stable Hu's reagent, N‐tosyl‐S‐difluoromethyl‐S‐phenylsulfoximine, as a CF2H source is the key to success. The well‐designed photoredox system achieves synthesis of not only β‐CF2H‐substituted alcohols but also ethers and an ester from alkenes through solvolytic processes. The present method allows a single‐step and regioselective formation of C(sp3)–CF2H and C(sp3)?O bonds from C=C moiety in alkenes, such as hydroxydifluoromethylation, regardless of terminal or internal alkenes. Moreover, this methodology tolerates a variety of functional groups. 相似文献
16.
Chiral N,N′‐Dioxide‐Organocatalyzed Regio‐, Diastereo‐ and Enantioselective Michael Addition–Alkylation Reaction
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Juhua Feng Xiao Yuan Weiwei Luo Dr. Lili Lin Prof. Dr. Xiaohua Liu Prof. Dr. Xiaoming Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(44):15650-15653
A highly regio‐, diastereo‐ and enantioselective Michael addition–alkylation reaction between α‐substituted cyano ketones and (Z)‐bromonitrostyrenes has been realized by using a chiral N,N′‐dioxide as organocatalyst. A variety of substrates performed well in this reaction, and the corresponding multifunctionalized chiral 2,3‐dihydrofurans were obtained in up to 95 % yield with 95:5 dr and 93 % ee. 相似文献
17.
Asymmetric Synthesis of Hydrocarbazoles Catalyzed by an Octahedral Chiral‐at‐Rhodium Lewis Acid
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A bis‐cyclometalated chiral‐at‐metal rhodium complex catalyzes the Diels–Alder reaction between N‐Boc‐protected 3‐vinylindoles (Boc=tert‐butyloxycarbonyl) and β‐carboxylic ester‐substituted α,β‐unsaturated 2‐acyl imidazoles with good‐to‐excellent regioselectivity (up to 99:1) and excellent diastereoselectivity (>50:1 d.r.) as well as enantioselectivity (92–99 % ee) under optimized conditions. The rhodium catalyst serves as a chiral Lewis acid to activate the 2‐acyl imidazole dienophile by two‐point binding and overrules the preferred regioselectivity of the uncatalyzed reaction. 相似文献
18.
Construction of a Chiral Silicon Center by Rhodium‐Catalyzed Enantioselective Intramolecular Hydrosilylation
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Dr. Yuki Naganawa Tomoya Namba Mayu Kawagishi Prof. Dr. Hisao Nishiyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9319-9322
Rhodium‐catalyzed enantioselective desymmetrizing intramolecular hydrosilylation of symmetrically disubstituted hydrosilanes is described. The original axially chiral phenanthroline ligand (S)‐BinThro (Binol‐derived phenanthroline) was found to work as an effective chiral catalyst for this transformation. A chiral silicon stereogenic center is one of the chiral motifs gaining much attention in asymmetric syntheses and the present protocol provides cyclic five‐membered organosilanes incorporating chiral silicon centers with high enantioselectivities (up to 91 % ee). The putative active RhI catalyst takes the form of an N,N,O‐tridentate coordination complex, as determined by several complementary experiments. 相似文献
19.
Design,Synthesis, and Application of Chiral C2‐Symmetric Spiroketal‐Containing Ligands in Transition‐Metal Catalysis
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Alonso J. Argüelles Siyuan Sun Brenna G. Budaitis Prof. Dr. Pavel Nagorny 《Angewandte Chemie (International ed. in English)》2018,57(19):5325-5329
We present an expedient and economical route to a new spiroketal‐based C2‐symmetric chiral scaffold, termed SPIROL. Based on this spirocyclic scaffold, several chiral ligands were generated. These ligands were successfully employed in an array of stereoselective transformations, including in iridium‐catalyzed hydroarylations (up to 95 % ee), palladium‐catalyzed allylic alkylations (up to 97 % ee), intermolecular palladium‐catalyzed Heck couplings (up to 94 % ee), and rhodium‐catalyzed dehydroalanine hydrogenation (up to 93 % ee). 相似文献
20.
Ryuhei Ikeda Prof. Ryoichi Kuwano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8610-8618
The iridium catalyst [IrCl(cod)]2–phosphine–I2 (cod=1,5‐cyclooctadiene) selectively reduced isoxazolium triflates to isoxazolines or isoxazolidines in the presence of H2. The iridium‐catalyzed hydrogenation proceeded in high‐to‐good enantioselectivity when an optically active phosphine–oxazoline ligand was used. The 3‐substituted 5‐arylisoxazolium salts were transformed into 4‐isoxazolines with up to 95:5 enantiomeric ratio (e.r.). Chiral cis‐isoxazolidines were obtained in up to 89:11 e.r., with no formation of their trans isomers, when the substrates had a primary alkyl substituent at the 5‐position. The mechanistic studies indicate that the hydridoiridium(III) species prefers to deliver its hydride to the C5 atom of the isoxazole ring. The hydride attack leads to the formation of the chiral isoxazolidine via a 3‐isoxazoline intermediate. Meanwhile, in the selective formation of 4‐isoxazolines, hydride attack at the C5 atom may be obstructed by steric hindrance from the 5‐aryl substituent. 相似文献