共查询到20条相似文献,搜索用时 15 毫秒
1.
A highly organocatalytic stereoselective double Michael reaction: efficient construction of optically enriched spirocyclic oxindoles 总被引:1,自引:0,他引:1
Wang LL Peng L Bai JF Jia LN Luo XY Huang QC Xu XY Wang LX 《Chemical communications (Cambridge, England)》2011,47(19):5593-5595
An effective double Michael reaction has been disclosed to access spirocyclic oxindoles in high yields (up to 98%) and excellent enantioselectivities (up to 98% ee). 相似文献
2.
《Tetrahedron: Asymmetry》2006,17(3):336-346
The diastereoselective allylation and reduction of camphor-derived α-ketoamides to give optically enriched α-hydroxyl amides with high to excellent stereoselectivities are described. Allylation was carried out using allyltributylstannane in the presence of a stoichiometric amount of a Lewis acid to afford the desired homoallylic alcohols in relatively high chemical yields (up to 98%) and stereoselectivities (up to 98% de). Diastereoselective reductions were performed with the relatively bulky hydride K-Selectride at −78 °C to give the corresponding α-hydroxy amides in excellent chemical yields (up to 98%) and stereoselectivities (up to 98% de). The absolute configuration of the new stereogenic center of the major diastereomer was established by X-ray crystallographic analysis. Finally, stereochemical induction and the Lewis acid dependent reversal of stereoselectivity is described. 相似文献
3.
Sugita M Yamaguchi A Yamagiwa N Handa S Matsunaga S Shibasaki M 《Organic letters》2005,7(23):5339-5342
[reaction, structure: see text] Chiral Y{N(SiMe3)2}3/linked-BINOL catalyst generated Y-enolate in situ from various hydroxyketones (R2 = aryl, heteroaryl). Beta-amino-alpha-hydroxy ketones (R1 = aryl, heteroaryl, alkenyl) were obtained syn-selectively (up to 96/4) in high ee (up to 98%) and good yield (up to 98% yield). 相似文献
4.
Chonticha SuttibutYoshihito Kohari Ko IgarashiHiroto Nakano Masafumi HiramaChigusa Seki Haruo MatsuyamaNobuhiro Takano Yuko OkuyamaKenichi Osone Mitsuhiro TakeshitaEunsang Kwon 《Tetrahedron letters》2011,52(37):4745-4748
An easily prepared chiral amino alcohol catalyst was found to provide an efficient synthetic intermediate of oseltamivir with excellent chemical yield and enantioselectivity (up to 98% yield and up to 98% ee) in enantioselective Diels-Alder reactions of 1,2-dihydropylidines with acroleins. 相似文献
5.
Sladojevich F Trabocchi A Guarna A Dixon DJ 《Journal of the American Chemical Society》2011,133(6):1710-1713
A new class of readily accessible chiral amino-phosphine precatalysts derived from 9-amino(9-deoxy) epicinchona alkaloids has been developed. In combination with Ag(I) salts, these amino-phosphines performed as effective cooperative Br?nsted base/Lewis acid catalysts in the asymmetric aldol reaction of isocyanoacetate nucleophiles. Under optimal conditions, high diastereoselectivities (up to 98%) and enantioselectivities (up to 98%) were obtained. 相似文献
6.
Bai JF Wang LL Peng L Guo YL Jia LN Tian F He GY Xu XY Wang LX 《The Journal of organic chemistry》2012,77(6):2947-2953
A highly diastereoselective and enantioselective Michael addition of α-substituted isocyanoacetates with maleimides catalyzed by bifunctional tertiary amine thioureas has been developed. Various chiral succinimide derivatives bearing adjacent quaternary and tertiary stereocenters were prepared in excellent yields (up to 98%), diastereoselectivities (up to 99:1), and enantioselectivities (up to 98% ee). The synthetic utility of chiral succinimide derivatives is also demonstrated in the preparation of h5-HT(1d) receptor agonist motifs. 相似文献
7.
A new class of chiral ligand, tethered bis(8-quinolinol) (TBOxH), is developed. Its chromium complex, TBOxCrCl (3 mol %), effectively catalyzes the pinacol coupling reaction of aromatic aldehydes at room temperature with high yield (up to 94%), high diastereoselectivity (up to dl:meso = 98:2), and high enantioselectivity (up to 98%). The scope of the present method turns out not to be limited to aromatic aldehyde derivatives, as cyclohexanecarboxaldehyde undergoes pinacolization as well (44% yield, dl:meso = 93:7, 84% ee). The method provides an efficient access to enantioenriched 1,2-diols. 相似文献
8.
Panagiota Revelou Christoforos G. Kokotos Panagiota Moutevelis-Minakakis 《Tetrahedron》2012,68(42):8732-8738
Among the various versions of the aldol reaction, the enantioselective reaction between cyclic ketones and aldehydes constitutes a typical reaction model for the evaluation of novel organocatalysts. A multifunctional organocatalyst consisting of a prolinamide moiety, a gem diamine unit and a urea group was successfully employed in this asymmetric transformation. The products of the reaction between various ketones and aldehydes were obtained in high yields (up to 98%) with excellent diastereo- (up to >98:2 dr) and enantioselectivities (up to 99% ee). 相似文献
9.
New chiral organocatalysts are envisaged based on a pyrrolidine–pyridone conjugate and synthesized from commercially available proline employing standard protocols. These catalysts were found to be useful for asymmetric Michael additions of ketones to nitroolefins to afford the desired products in very good yields (up to 98%) with excellent diastereo- and enantioselectivities (>97:3 syn/anti and up to 98% ee) in very short reaction time compared with the existing reports. 相似文献
10.
A catalytic synthetic route to highly functionalized chiral cyclopropane derivatives was developed by Michael-initiated cyclopropanation of α-substituted acroleins with aryl- and alkyl diazoacetates. In the presence of chiral (S)-oxazaborolidinium cation 1b as a catalyst, the reaction proceeded in high yield (up to 93%) with high to excellent diastereoselectivity (up to 98% de) and enantioselectivity (up to 95% ee). 相似文献
11.
A robust and stable Ru-Biphosphinobioxazoline catalyst system is discovered for the highly enantioselective hydrogenation of enones to allylic alcohols. A series of acyclic α,β-unsaturated ketones react well affording the desired products in high yields (up to 98%) and enantioselectivities (up to 98% ee). Simple manipulation process and tolerance of water and air make this catalysis more practical and appealing. 相似文献
12.
The readily available and inexpensive new chiral oxazolidine in combination with Ti(O(i)Pr)(4) was found to catalyze the reaction of an alkynylzinc reagent with various types of aldehydes to generate chiral propargylic alcohols with high enantioselectivities (up to 95%) and excellent yields (up to 98%). 相似文献
13.
Wang JC Xu ZJ Guo Z Deng QH Zhou CY Wan XL Che CM 《Chemical communications (Cambridge, England)》2012,48(36):4299-4301
The chiral iridium porphyrin [Ir((-)-D(4)-Por*)(Me)(EtOH)] displays excellent reactivity and stereoselectivity towards carbene insertion to C-H and Si-H bonds, affording corresponding products in high yields (up to 96%) and high enantioselectivities (up to 98% ee). 相似文献
14.
[reaction: see text] A novel Cu(I)-catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides with acrylates has been developed. Up to 98/2 exo/endo selectivity and up to 98% enantiomeric excess have been achieved. 相似文献
15.
Enantioselective synthesis of functionalized fluorinated dihydropyrano[2,3-c]pyrazoles has been achieved via a diaminocyclohexane-thiourea catalyzed cascade Michael addition and Thorpe-Ziegler type cyclization in high yields (up to 98%) with moderate to good enantioselectivity (up to 90% ee). 相似文献
16.
T Zhou B Peters MF Maldonado T Govender PG Andersson 《Journal of the American Chemical Society》2012,134(33):13592-13595
A highly efficient and enantioselective Ir-catalyzed hydrogenation of unsaturated sulfones was developed. Chiral cyclic and acyclic sulfones were produced in excellent enantioselectivities (up to 98% ee). Coupled with the Ramberg-B?cklund rearrangement, this reaction offers a novel route to chiral allylic and homoallylic compounds in excellent enantioselectivities (up to 97% ee) and high yields (up to 94%). 相似文献
17.
A bulky group was introduced by design into a diamine catalyst, and a series of robust and tunable bulky chiral primary amine catalysts were developed and successfully applied in the direct conjugate addition of substituted rhodanines to α,β-unsaturated ketones. High yields (up to 99%) and excellent diastereoselectivities (up to 99:1 dr) and enantioselectivities (up to 98% ee) were observed. 相似文献
18.
19.
Reduction of (RS)-N-tert-butanesulfinyl alpha-halo imines afforded chiral aziridines in good to excellent yields. Upon reduction of (RS)-N-tert-butanesulfinyl alpha-halo imines with NaBH4 in THF, in the presence of 10 equiv of MeOH, (RS,S)-beta-halo sulfinamides were formed in excellent yield (up to 98%) with very good stereoselectivity (>98:2). Simple treatment of the latter (RS,S)-beta-halo-tert-butanesulfinamides with KOH afforded the corresponding (RS,S)-N-(tert-butylsulfinyl)aziridines in quantitative yields. On the contrary, its epimer, (RS,R)-N-(tert-butylsulfinyl)aziridine was synthesized by switchover of the reducing agent from NaBH4 to LiBHEt3. (RS,R)-N-(tert-Butylsulfinyl)aziridines were synthesized in good yields (up to 85%) and diastereoselectivity (up to 92:8) by reduction of (RS)-N-tert-butanesulfinyl alpha-halo imines with LiBHEt3 in dry THF and subsequent treatment with KOH. All chiral aziridines were obtained as a single diastereomer after recrystallization (overall yield up to 91%) or after flash chromatography. 相似文献
20.
Cu(I)催化的亚甲胺叶立德和亚环丙基乙酸乙酯参与的不对称endo-1,3-偶极环加成反应,高效构建了多官能化、含有多个连续季碳中心的5-氮杂-[2,4]庚烷化合物.此反应具有广泛的底物适用性,α-取代的和α-非取代的亚甲胺叶立德和亚环丙基乙酸乙酯都能很好的参与反应,并以很高的产率、优秀的非对映选择性(95:5–98:2 d.r)和对映选择性(87%–98%ee)生成相应的在2,3,4位上含有连续季碳中心的螺四氢吡咯化合物. 相似文献