Direct asymmetric aldol reactions catalysed by trans-4-hydroxy-(S)-prolinamide in solvent-free conditions
摘要:
Direct asymmetric aldol reactions between 4-nitrobenzaldehyde and cyclohexanone were catalysed by trans-4-hydroxy-(S)-prolinamide (10 mol %) in the presence of CH3COOH (10 mol %) as the co-catalyst under solvent-free conditions at 15 degrees C. (2S,4R)-4-Hydroxy-N-((S)-1-phenylethyl)pyrrolidine-2-carboxamide 2 efficiently, catalysed the asymmetric aldol reaction to afford the product in >99% yield and with 95% ee with an antilsyn ratio of 88:12 after 18 h. The additional trans-hydroxyl group on (S)-prolinamide and (S)-1-phenylethylamine both influenced the ee of the predominant anti aldol product. Different benzaldehyde derivatives with cyclohexanone gave the corresponding aldol products in 38-89% yields and with 56-94% ee with antilsyn (100:0-71:29). Catalyst 2 can be used up to 5 continuous cycles for asymmetric aldol reactions between 4-nitrobenzaldehyde and cyclohexanone with overall 91% yield and 86% yield of anti-product with anti/syn (98:2). (C) 2015 Elsevier Ltd. All rights reserved.
(<scp>l</scp>)-Prolinamide imidazolium hexafluorophosphate ionic liquid as an efficient reusable organocatalyst for direct asymmetric aldol reaction in solvent-free condition
作者:Geeta Devi Yadav、Surendra Singh
DOI:10.1039/c6ra23652a
日期:——
We have designed a new hydrophobic ionicliquid derived from bromoester of trans-4-hydroxy-(L)-prolinamide and N-methylimidazole. (L)-Prolinamide imidazolium hexafluorophosphate ionicliquid (2 mol%) found to be an excellent organocatalyst for direct...
Copolymer-supported heterogeneous organocatalyst for asymmetric aldol addition in aqueous medium
作者:Jinqing Zhou、Jinwei Wan、Xuebing Ma、Wei Wang
DOI:10.1039/c2ob25106j
日期:——
conditions. Compared with cyclohexanone, cyclopentanone and acetone showed the less desired enantioselectivities in the same aldolreactions. At the end of the aldolreaction, the copolymer-supported organocatalyst 1a was readily recovered in 95–98% yield from reaction mixture by simple filtration using an organic membrane. Even in the fifth run, there was no significant loss in catalytic activity and stereocontrol
在当前的研究中,提出了一种方便和简单的方法,以AIBN为自由基引发剂,将9-氨基-9-脱氧-表位-辛可宁有机催化剂与丙烯腈共聚,以21-81%的产率合成新型负载型多相有机催化剂。。共聚物1a–d的化学组成(x / y)和重均分子量分别通过1 H NMR和GPC分析确定。它们的多孔和层状结构以及表面形貌通过氮吸附-解吸,XRD和TEM表征。在水中对硝基苯甲醛与对硝基苯甲醛的不对称醛醇加成反应中,所有负载的有机催化剂1a–d可提供出色的分离产率(90.2–94.7%)和立体选择性(96.8–97.8%ee抗,抗/ syn = 91/9)。在优化的条件下,在水中作为唯一的溶剂可获得最高的催化性能(96%的收率,抗/ syn = 90/10和99%ee抗)。与环己酮相比,环戊酮和丙酮在相同的羟醛反应中显示出较低的对映选择性。在醛醇缩合反应结束时,共聚物负载的有机催化剂1a通过使用有机膜的简单过滤,
Intermolecular Antiselective and Enantioselective Reductive Coupling of Enones and Aromatic Aldehydes with Chiral Rh(Phebox) Catalysts
The intermolecular reductive coupling reaction of cyclopent-2-enone and aromatic aldehydes was realized by chiral rhodium-(bisoxazolinyl)phenyl catalysts, Rh(Phebox-Ph)(OAc)(2)(H2O), with diphenymethylsilane as a hydride donor to give the corresponding beta-hydroxyketones in high anti selectivity (up to 96%) with high enantioselectivity (up to 93%).
Water promoted enantioselective aldol Reaction by proline-cholesterol and -diosgenin based amphiphilic organocatalysts
A series of proline-cholesterol and -diosgenin based amphiphilic organocatalysts were developed for the first time, and their catalytic activities for the enantioselective aldol reaction were investigated. The results indicated that water can significantly enhance the activity and stereoselectivity of the transformation via micelle formation. TEM and AFM analysis demonstrated that the diameter of the micelle particles ranged from 200 to 800 nm. (C) 2013 Elsevier Ltd. All rights reserved.
Direct asymmetric aldol reactions catalysed by trans-4-hydroxy-(S)-prolinamide in solvent-free conditions
作者:Geeta Devi Yadav、Surendra Singh
DOI:10.1016/j.tetasy.2015.09.003
日期:2015.11
Direct asymmetric aldol reactions between 4-nitrobenzaldehyde and cyclohexanone were catalysed by trans-4-hydroxy-(S)-prolinamide (10 mol %) in the presence of CH3COOH (10 mol %) as the co-catalyst under solvent-free conditions at 15 degrees C. (2S,4R)-4-Hydroxy-N-((S)-1-phenylethyl)pyrrolidine-2-carboxamide 2 efficiently, catalysed the asymmetric aldol reaction to afford the product in >99% yield and with 95% ee with an antilsyn ratio of 88:12 after 18 h. The additional trans-hydroxyl group on (S)-prolinamide and (S)-1-phenylethylamine both influenced the ee of the predominant anti aldol product. Different benzaldehyde derivatives with cyclohexanone gave the corresponding aldol products in 38-89% yields and with 56-94% ee with antilsyn (100:0-71:29). Catalyst 2 can be used up to 5 continuous cycles for asymmetric aldol reactions between 4-nitrobenzaldehyde and cyclohexanone with overall 91% yield and 86% yield of anti-product with anti/syn (98:2). (C) 2015 Elsevier Ltd. All rights reserved.