共查询到20条相似文献,搜索用时 31 毫秒
1.
A Mild Dihydrobenzooxaphosphole Oxazoline/Iridium Catalytic System for Asymmetric Hydrogenation of Unfunctionalized Dialins 下载免费PDF全文
Dr. Bo Qu Dr. Lalith P. Samankumara Dr. Shengli Ma Dr. Keith R. Fandrick Dr. Jean‐Nicolas Desrosiers Dr. Sonia Rodriguez Dr. Zhibin Li Dr. Nizar Haddad Dr. Zhengxu S. Han Keith McKellop Scott Pennino Dr. Nelu Grinberg Dr. Nina C. Gonnella Dr. Jinhua J. Song Dr. Chris H. Senanayake 《Angewandte Chemie (International ed. in English)》2014,53(52):14428-14432
Air‐stable P‐chiral dihydrobenzooxaphosphole oxazoline ligands were designed and synthesized. When they were used in the iridium‐catalyzed asymmetric hydrogenation of unfunctionalized 1‐aryl‐3,4‐dihydronaphthalenes under one atmosphere pressure of H2, up to 99:1 e.r. was obtained. High enantioselectivities were also observed in the reduction of the exocyclic imine derivatives of 1‐tetralones. 相似文献
2.
Xu Liu Zhaobin Han Zheng Wang Kuiling Ding 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(7):2009-2013
Optically active medium‐sized cyclic carbonyl compounds bearing an α‐chiral carbon center are of interest in pharmaceutical sciences and asymmetric synthesis. Herein, SpinPhox/IrI catalysts have been demonstrated to be highly enantioselective in the asymmetric hydrogenation of the CC bonds in the exocyclic α,β‐unsaturated cyclic carbonyls, including a broad range of α‐alkylidene lactams, unsaturated cyclic ketones, and lactones. It is noteworthy that the procedure can be successfully used in the asymmetric hydrogenation of the challenging α‐alkylidenelactam substrates with six‐ or seven‐membered rings, thus affording the corresponding optically active carbonyl compounds with an α‐chiral carbon center in generally excellent enantiomeric excesses (up to 98 % ee). Synthetic utility of the protocol has also been demonstrated in the asymmetric synthesis of the anti‐inflammatory drug loxoprofen and its analogue, as well as biologically important ε‐aminocaproic acid derivatives. 相似文献
3.
Kostiantyn O. Marichev Kan Wang Kuiyong Dong Nicole Greco Lyne A. Massey Yongming Deng Hadi Arman Michael P. Doyle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(45):16334-16338
The all‐cis stereoisomers of tetrasubstituted azetidine‐2‐carboxylic acids and derivatives that possess three chiral centers have been prepared in high yield and stereocontrol from silyl‐protected Z‐γ‐substituted enoldiazoacetates and imido‐sulfur ylides by asymmetric [3+1]‐cycloaddition using chiral sabox copper(I) catalysis followed by Pd/C catalytic hydrogenation. Hydrogenation of the chiral p‐methoxybenzyl azetine‐2‐carboxylates occurs with both hydrogen addition to the C=C bond and hydrogenolysis of the ester. 相似文献
4.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(15):4199-4203
The first asymmetric hydrogenation of in situ generated isochromenylium derivatives is enabled by tandem catalysis with a binary system consisting of Cu(OTf)2 and a chiral cationic ruthenium–diamine complex. A range of chiral 1H ‐isochromenes were obtained in high yields with good to excellent enantioselectivity. These chiral 1H ‐isochromenes could be easily transformed into isochromanes, which represent an important structural motif in natural products and biologically active compounds. The chiral induction was rationalized by density functional theory calculations. 相似文献
5.
Synthesis of Chiral Exocyclic Amines by Asymmetric Hydrogenation of Aromatic Quinolin‐3‐amines 下载免费PDF全文
Xian‐Feng Cai Ran‐Ning Guo Mu‐Wang Chen Lei Shi Prof. Yong‐Gui Zhou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7245-7248
Asymmetric hydrogenation of aromatic quinolin‐3‐amines was successfully developed with up to 94 % enantiomeric excess (ee). Introduction of the phthaloyl moiety to the amino group is crucial to eliminate the inhibition effect caused by the substrate and product, to activate the aromatic ring, and to improve the diastereoselectivity. This new methodology provides direct and facile access to chiral exocyclic amines. Notably, this report is the first on the highly enantioselective hydrogenation of aromatic amines. 相似文献
6.
Ruthenium(II) complexes derived from C2‐symmetric ferrocene‐based chiral bis(phosphinite) ligands: synthesis and catalytic activity towards the asymmetric reduction of acetophenones 下载免费PDF全文
Chiral secondary alcohols are very important building blocks and valuable synthetic intermediates both in organic synthesis and in the pharmaceutical industry for producing biologically active complex molecules. A series of new chiral Ru–phosphinite complexes ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ) were prepared from chiral C2‐symmetric ferrocenyl phosphinites and corresponding chloro complex, [Ru(η6‐p‐cymene)(μ‐Cl)Cl]2. The complexes were characterized using conventional spectroscopic methods. The binuclear complexes were tested as pre‐catalysts and were found to be good pre‐catalysts for the asymmetric transfer hydrogenation of substituted acetophenones in basic 2‐propanol at 82°C, providing the corresponding optically active alcohols with almost quantitative conversion and modest to high enantioselectivities (46–97%). Amongst the all complexes, complex 6 gave the highest ee of 97% in the reduction of 2‐methoxyacetophenone to (S)‐1‐(2‐methoxyphenyl)ethanol at 82°C. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
《应用有机金属化学》2017,31(12)
The design and synthesis of three new C 2‐symmetric chiral diphosphoramidite ligands starting from simple and cheap building blocks have been developed. Rhodium(I) cationic complexes bearing these chelate ligands have been prepared and applied in asymmetric hydrogenation of model olefins. A rhodium complex with a diphosphoramidite containing a chiral diamine configurationally stable and two fluxional chiral biphenyl units gave higher enantioselectivity with increasing hydrogen pressure (87% ee) in the hydrogenation of dimethyl itaconate. 相似文献
8.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(20):5955-5959
A facile access to optically active cyclic ureas was developed through palladium‐catalyzed asymmetric hydrogenation of pyrimidines containing tautomeric hydroxy group with up to 99 % ee. Mechanistic studies indicated that reaction pathway proceed through hydrogenation of C=N of the oxo tautomer pyrimidin‐2(1H)‐one, acid‐catalyzed isomerization of enamine–imine, and hydrogenation of imine pathway. In addition, the chiral cyclic ureas are readily converted into useful chiral 1,3‐diamine and thiourea derivatives without loss of optical purity. 相似文献
9.
Dr. Xun Zhang Dr. Jing Li Hua Tian Prof. Dr. Yian Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11658-11663
The dimeric cinchona alkaloid (DHQD)2PHAL is used to catalyze an effective asymmetric bromohydroxylation of unfunctionalized olefins with H2O as nucleophile an N‐bromobenzamide as a bromine source. A variety of optically active bromohydrins are formed with up to 88 % ee. 相似文献
10.
11.
ZnCl2‐Promoted Asymmetric Hydrogenation of β‐Secondary‐Amino Ketones Catalyzed by a P‐Chiral Rh–Bisphosphine Complex 下载免费PDF全文
Qiupeng Hu Dr. Zhenfeng Zhang Prof. Yangang Liu Prof. Tsuneo Imamoto Prof. Wanbin Zhang 《Angewandte Chemie (International ed. in English)》2015,54(7):2260-2264
A new catalytic system has been developed for the asymmetric hydrogenation of β‐secondary‐amino ketones using a highly efficient P‐chiral bisphosphine–rhodium complex in combination with ZnCl2 as the activator of the catalyst. The chiral γ‐secondary‐amino alcohols were obtained in 90–94 % yields, 90–99 % enantioselectivities, and with high turnover numbers (up to 2000 S/C; S/C=substrate/catalyst ratio). A mechanism for the promoting effect of ZnCl2 on the catalytic system has been proposed on the basis of NMR spectroscopy and HRMS studies. This method was successfully applied to the asymmetric syntheses of three important drugs, (S)‐duloxetine, (R)‐fluoxetine, and (R)‐atomoxetine, in high yields and with excellent enantioselectivities. 相似文献
12.
《Journal of carbohydrate chemistry》2013,32(6):377-383
Tri‐O‐acetyl‐d‐glucal (1) was converted via Ferrier type II rearrangement with high α‐selectivity to 2,3‐unsaturated methyl glycosides 2a and 2b using ferric chloride as the catalyst. Palladium induced allylic substitution with sodium tert‐butylacetoacetate as a nucleophile leads to C‐4 branched sugars. Subsequent hydrogenation followed by treatment with trifluoroacetic acid affords the highly functionalized chiral cyclopentene derivative 5a as a versatile chiral building block for cyclopentanoids. 相似文献
13.
Javier Mazuela Alexander Paptchikhine Oscar Pàmies Pher G. Andersson Montserrat Diéguez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(15):4567-4576
A library of readily available phosphite–oxazole/thiazole ligands ( L1 a – g – L7 a – g ) was applied in the Ir‐catalyzed asymmetric hydrogenation of several largely unfunctionalized E‐ and Z‐trisubstituted and 1,1‐disubstituted terminal alkenes. The ability of the catalysts to transfer chiral information to the product could be tuned by choosing suitable ligand components (bridge length, the substituents in the heterocyclic ring and the alkyl backbone chain, the configuration of the ligand backbone, and the substituents/configurations in the biaryl phosphite moiety), so that enantioselectivities could be maximized for each substrate as required. Enantioselectivities were therefore excellent (enantiomeric excess (ee) values up to >99 %) for a wide range of E‐ and Z‐trisubstituted and 1,1‐disubstituted terminal alkenes. The biaryl phosphite moiety was a very advantageous ligand component in terms of substrate versatility. 相似文献
14.
Yong Shen Ai‐Xue Zuo Zhi‐Yong Jiang Xue‐Mei Zhang Hong‐Ling Wang Ji‐Jun Chen 《Helvetica chimica acta》2011,94(1):122-126
Two new C20‐diterpenoid alkaloids, named aconicarchamines A and B ( 1 and 2 , resp.), were isolated from Aconitum carmichaelii. By UV, IR, MS, and 1D‐ and 2D‐NMR analyses, their structures were elucidated as 14,17‐dihydro‐14,17‐dihydroxyajabicine and 15‐O‐acetyllassiocarpine. Compound 1 is the third C20‐diterpenoid alkaloid with the lycoctine skeleton bearing an exocyclic C‐atom at C(14). 相似文献
15.
Highly Enantioselective Direct Synthesis of Endocyclic Vicinal Diamines through Chiral Ru(diamine)‐Catalyzed Hydrogenation of 2,2′‐Bisquinoline Derivatives 下载免费PDF全文
Wenpeng Ma Jianwei Zhang Cong Xu Fei Chen Yan‐Mei He Prof. Dr. Qing‐Hua Fan 《Angewandte Chemie (International ed. in English)》2016,55(41):12891-12894
An asymmetric hydrogenation of 2,2′‐bisquinoline and bisquinoxaline derivatives, catalyzed by chiral cationic ruthenium diamine complexes, was developed. A broad range of chiral endocyclic vicinal diamines were obtained in high yields with excellent diastereo‐ and enantioselectivity (up to 93:7 dl/meso and >99 % ee). These chiral diamines could be easily transformed into a new class of chiral N‐heterocyclic carbenes (NHCs), which are important but difficult to access. 相似文献
16.
17.
Study of E/Z isomerization of (arylamino)methylidenefuran‐2(3H)‐ones by 1H, 13C, 15N spectroscopy and DFT calculations in different solvents 下载免费PDF全文
Alexander K. Osipov Alexander A. Anis'kov Vyacheslav S. Grinev Alevtina Yu. Yegorova 《Magnetic resonance in chemistry : MRC》2017,55(8):730-737
The structure and configuration of the series of previously unknown arylaminomethylidenefuran‐2(3H)‐ones have been determined in solution by 1H, 13C, 15N nuclear magnetic resonance spectroscopy including two‐dimensional experiments such as 1H─1H COSY, dqCOSY, 1H─13C HSQC, 1H─13C HMBC. It was found that synthesized substances exist as an equilibrium mixture of E‐ and Z‐enamines in solution. It was established on the basis of density functional theory calculations that the exchange between the two push–pull enamines is a simple rotation around an exocyclic partial double bond that depends on the effect of the solvents. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
18.
Tiziana Benincori Silvana Bruno Giuseppe Celentano Tullio Pilati Alessandro Ponti Simona Rizzo Mara Sada Francesco Sannicol 《Helvetica chimica acta》2005,88(7):1776-1789
A process‐scale stereoselective synthesis of nature‐identical (−)‐(S,S)‐7‐hydroxycalamenal (=(−)‐(5S,8S)‐5,6,7,8‐tetrahydro‐3‐hydroxy‐5‐methyl‐8‐(1‐methylethyl)naphthalene‐2‐carbaldehyde; (−)‐ 1a ) in 96% enantiomeric excess (ee) with the aid of chiral Ru complexes has been developed. The key step was the enantioselective hydrogenation of easily accessible 2‐(4‐methoxyphenyl)‐3‐methylbut‐2‐enoic acid ( 10 ) to (+)‐ 11 in a 86% ee (Scheme 5 and Table 1). A substantial increase in optical purity (96% ee) was achieved by induced crystallization of the intermediate (+)‐3,4‐dihydro‐4‐(1‐methylethyl)‐7‐methoxy‐2H‐naphthalen‐1‐one ((+)‐ 3 ). Computational conformation analysis carried out on the analog (−)‐ 9 rationalized the high diastereoselectivity achieved in the catalytic hydrogenation of the CC bond. 相似文献
19.
Dr. Mingxin Chang Yuhua Huang Shaodong Liu Dr. Yonggang Chen Dr. Shane W. Krska Dr. Ian W. Davies Prof. Xumu Zhang 《Angewandte Chemie (International ed. in English)》2014,53(47):12761-12764
Iridium‐catalyzed asymmetric hydrogenation of N‐alkyl‐2‐alkylpyridinium salts provided 2‐aryl‐substituted piperidines with high levels of enantioselectivity. Simple benzyl and other alkyl groups successfully activated the challenging pyridine substrates toward hydrogenation. The use of the unusual chiral‐phosphole‐based MP2‐SEGPHOS was the key to the success of this approach which provides a versatile and practical procedure for the synthesis of chiral piperidines. 相似文献
20.
Enantioselective Synthesis of Highly Functionalized Dihydrofurans through Copper‐Catalyzed Asymmetric Formal [3+2] Cycloaddition of β‐Ketoesters with Propargylic Esters 下载免费PDF全文
Fu‐Lin Zhu Ya‐Hui Wang De‐Yang Zhang Prof. Dr. Jie Xu Prof. Dr. Xiang‐Ping Hu 《Angewandte Chemie (International ed. in English)》2014,53(38):10223-10227
An enantioselective synthesis of highly functionalized dihydrofurans through a copper‐catalyzed asymmetric [3+2] cycloaddition of β‐ketoesters with propargylic esters has been developed. With a combination of Cu(OTf)2 and a chiral tridentate P,N,N ligand as the catalyst, a variety of 2,3‐dihydrofurans bearing an exocyclic double bond at the 2 position were obtained in good chemical yields and with good to high enantioselectivities. The exocyclic double bond can be hydrogenated in a highly diastereoselective fashion to give unusual cis‐2,3‐dihydrofuran derivatives, thus further enhancing the scope of this transformation. 相似文献