共查询到20条相似文献,搜索用时 15 毫秒
1.
Nishibayashi Y Yamauchi A Onodera G Uemura S 《The Journal of organic chemistry》2003,68(15):5875-5880
Oxidative kinetic resolution of racemic secondary alcohols by using acetone as a hydrogen acceptor in the presence of a catalytic amount of [RuCl(2)(PPh(3))(ferrocenyloxazolinylphosphine)] (2) proceeds effectively to recover the corresponding alcohols in high yields with an excellent enantioselectivity. When 1-indanol is employed as a racemic alcohol, the oxidation proceeds quite smoothly even in the presence of 0.0025 mol % of the catalyst 2 to give an optically active 1-indanol in good yield with high enantioselectivity (up to 94% ee), where turnover frequency (TOF) exceeds 80,000 h(-1). From a practical viewpoint, the kinetic resolution is investigated in a large scale, optically pure (S)-1-indanol (75 g, 56% yield, >99% ee) being obtained from racemic 1-indanol (134 g) by employing this kinetic resolution method twice. 相似文献
2.
《Tetrahedron: Asymmetry》2007,18(11):1338-1344
A set of racemic cyclic and linear ketones, as well as 2-phenylpropionaldehyde, were tested as substrates in the enzymatic Baeyer–Villiger oxidation catalyzed by two Baeyer–Villiger monooxygenases: phenylacetone monooxygenase (PAMO) and 4-hydroxyacetophenone monooxygenase (HAPMO). Excellent enantioselectivites (E > 200) can be obtained in the kinetic resolution processes depending on the substrate structure and the reaction conditions. The parameters affecting the biocatalytic properties of these enzymes were also studied, in order to establish a deeper understanding of these novel biocatalysts. 相似文献
3.
We report a new method for the preparation of chiral 2-aryl-2-fluoropropanoic acids, including 2-fluoroibuprofen, a fluorinated analogue of non-steroidal anti-inflammatory drugs (NSAIDs), by the kinetic resolution of racemic 2-aryl-2-fluoropropanoic acids using enantioselective esterification. By applying pivalic anhydride (Piv2O) as a coupling agent, bis(α-naphthyl)methanol [(α-Np)2CHOH] as an achiral alcohol, and (+)-benzotetramisole (BTM) as a chiral acyl-transfer catalyst, a series of racemic 2-aryl-2-fluoropropanoic acids were kinetically separated to afford the optically active carboxylic acids and the corresponding esters with good to high enantiomeric excesses. This technology can provide a convenient approach to furnish the chiral α-fluorinated drugs containing quaternary carbons at the α-positions in the 2-aryl-2-fluoropropanoic acid structure. 相似文献
4.
A synthetic route to a series of 4-alkyl- or arylquinolines, bearing in 2- and 3-position fluorinated and phosphonate functions at the same time, is reported for the first time. These compounds are synthesized via regioselective heterocyclization of XCF2-alkynylphosphonates (X=F, Cl, Br, H, CF3) with ortho-aminoaryl ketones (R=CH3, CF3, Ph) in the presence of K2CO3 or Li2CO3/TMEDA as mediators. 2-Fluoro- and 3-phosphorus-containing 4-Me, 4-CF3 or 4-Ph quinolines are obtained in good to excellent yields. The influence of substituents in the aromatic ketone, the XCF2-group in the alkyne as well as mediators and the reaction medium on the reactivity and specificity of the reaction is also investigated. 相似文献
5.
Treatment of 2-hydroxybenzaldehydes by potassium t-butoxide in THF at 0°C, followed by addition of β-nitroenones 1 affords 2-acyl-2-alkyl-4-hydroxy-3-nitrochromanes 3. Subsequent treatment of these nitro alcohols by silica gel at 50°C leads to the desired 2-acyl-2-alkyl-3-nitro-2H-chromenes 4 in good yields. 相似文献
6.
An efficient acylative kinetic resolution of racemic aromatic β-hydroxy esters with cyclohexanecarboxylic anhydride was achieved using newly designed (R)-N-methylbenzoguanidine ((R)-NMBG) derivatives. A series of (R)-NMBG derivatives was synthesized by modifying the original (R)-NMBG catalyst with the introduction of branched N-substituents containing a stereogenic center, and their catalytic performance was evaluated. (R,R)-N-(1-(β-1-Naphthyl)ethyl)benzoguanidine [(R,R)-NβNpEtBG] was found to function as an efficient acyl transfer catalyst for the reaction of a broad variety of substrates, regardless of the substituent type and substitution pattern. 相似文献
7.
Nonenzymatic kinetic resolution of racemic β-hydroxyalkanephosphonates with a chiral copper catalyst
Atsushi Moriyama Shintaro Matsumura Masami Kuriyama Osamu Onomura 《Tetrahedron: Asymmetry》2010,21(7):810-824
Kinetic resolution of β-hydroxyalkanephosphonates was efficiently performed by 2-fluorobenzoylation in the presence of copper(II) triflate and (R,R)-Ph-BOX as a catalyst with good s value of up to 21. 相似文献
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Kinetic resolution of acyclic secondary allylic silyl ethers by chiral dioxiranes generated in situ from chiral ketones (R)-1 and (R)-2 and Oxone was investigated. An efficient and catalytic method has been developed for kinetic resolution of those substrates with a CCl(3), tert-butyl, or CF(3) group at the alpha-position. In particular, high selectivities (S up to 100) were observed for kinetic resolutions of racemic alpha-trichloromethyl allylic silyl ethers 7 and 9-15 catalyzed by ketones (R)-2. Both the recovered substrates and the resulting epoxides were obtained in high enantiomeric excess. On the basis of steric and electrostatic interactions between the chiral dioxiranes and the racemic substrates, a model was proposed to rationalize the enantioselectivities and diastereoselectivities in the chiral ketone-catalyzed kinetic resolution process. 相似文献
10.
Chiral diaminodiphosphine-Ir(I) complexes were found to efficiently catalyze enantioselective oxidation of racemic secondary alcohols in acetone. In the presence of base, oxidative kinetic resolution of the alcohols proceeded smoothly with excellent enantioselectivity (up to 98% ee) under mild conditions. [reaction: see text]. 相似文献
11.
Chengjun Jiang 《Kinetics and Catalysis》2011,52(5):691-696
The highly enantioselective hydrolytic kinetic resolution (HKR) of racemic terminal epoxides by bimetallic chiral (salen)Co
and (salen)Co(III)-OAc mixture provides a simple and effective method for the synthesis of enantiomerically enriched terminal
epoxides (ee > 99%) and diols. At the equimolar amounts of bimetallic chiral (salen)Co and (salen)Co(II)-OAc, the catalytic activity increases
more than two times in comparison with (salen)Co(III)-OAc used alone. The mixed catalytic system can be recycled and reused.
No significant loss of catalytic activity was observed after three runs. 相似文献
12.
V. Yu. Korotaev V. Ya. Sosnovskikh I. B. Kutyashev M. I. Kodess 《Russian Chemical Bulletin》2006,55(11):2020-2031
The nucleophilic addition of acetylacetone and ethyl acetoacetate at the double bond of 3-nitro-2-trihalomethyl-2H-chromenes in the presence of NaH affords 2,3,4-trisubstituted chromanes containing the β-dicarbonyl fragment at position
4. The trans-trans configuration and the enol structure of the reaction products were confirmed by 1H NMR spectroscopy and X-ray diffraction. Treatment of these compounds with hydrazine gives the corresponding 3-nitro-4-(pyrazol-4-yl)-2-trihalomethylchromanes.
The reactions of 3-nitro-2-trihalomethyl-2H-chromenes with nitromethane and nitroethane in the presence of K2CO3 produce 1,3-dinitro derivatives of the chromane series.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1945–1955, November, 2006. 相似文献
13.
A novel, efficient, and unprecedented organocatalytic kinetic resolution has been developed. For the first time, a variety of nitroallylic acetates 1a-i have been resolved with aldehydes in the presence of 2 (2.5 mol %) via conjugate addition-elimination. The densely functionalized products 3a-o were obtained with excellent enantioselectivities (up to >99% ee), and unreacted substrates 1a-i were recovered with good to excellent optical purity (up to 98% ee). 相似文献
14.
Shohei Hamada Yoshiyuki WadaTakahiro Sasamori Norihiro TokitohTakumi Furura Takeo Kawabata 《Tetrahedron letters》2014
A method for oxidative kinetic resolution of racemic alcohols catalyzed by chiral nitroxyl radical (R,R)-1 has been developed. This method is especially effective for the kinetic resolution of tert-butyl aryl carbinols (s = up to 23). 相似文献
15.
V. Yu. Korotaev V. Ya. Sosnovskikh I. B. Kutyashev M. I. Kodess 《Russian Chemical Bulletin》2006,55(2):317-330
The reactions of 3-nitro-2-trifluoromethyl-and 3-nitro-2-trichloromethyl-2H-chromenes with thiols and aromatic amines proceed via the nucleophilic addition type to the activated double bond to form 2,3,4-trisubstituted chromanes in high yields. The stereoisomeric
compositions and structures of the diastereomers were determined by 1H, 19F NMR and 2D NOESY spectroscopies and X-ray diffraction analysis.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 309–321, February, 2006. 相似文献
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Amat M Bassas O Pericàs MA Pastó M Bosch J 《Chemical communications (Cambridge, England)》2005,(10):1327-1329
Cyclocondensation reactions of aminoalcohols and with racemic or prochiral delta-oxoacid derivatives provide polysubstituted lactams with high enantioselectivity in a process that involves dynamic kinetic resolution and/or desymmetrization of enantiotopic or diastereotopic ester groups. 相似文献
20.
Larionov E Mahesh M Spivey AC Wei Y Zipse H 《Journal of the American Chemical Society》2012,134(22):9390-9399
The mechanism of esterification of the secondary alcohol 1-(1-naphthyl)ethanol 9 by isobutyric anhydride catalyzed by 4-pyrrolidinopyridine (PPY, 11) and a series of single enantiomer atropisomeric 4-dialkylaminopyridines 8a-g has been studied computationally at the B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level. Comparison of the levels of enantioselectivity predicted computationally with the results obtained experimentally allowed the method to be validated. The value of the approach is demonstrated by the successful prediction that a structural modification of an aryl group within the catalyst from phenyl to 3,5-dimethylphenyl would lead to improved levels of selectivity in this type of kinetic resolution (KR) reaction, as was subsequently verified following synthesis and evaluation of this catalyst (8d). Experimentally, the selectivity of this type of KR is found to exhibit a significant deuterium isotope effect (for 9 vs d(1)-9). 相似文献