Proline-Catalyzed Asymmetric Aldol Reactions between Ketones and α-Unsubstituted Aldehydes
作者:Benjamin List、Peter Pojarliev、Chris Castello
DOI:10.1021/ol006976y
日期:2001.2.1
[reaction: see text] With this communication we extend the methodology of proline-catalyzed direct asymmetric aldol reactions to include alpha-unsubstituted aldehydes as acceptors. This important aldehyde class gives the corresponding aldols in 22-77% yield and up to 95% ee when the reactions are performed in pure acetone or in ketone/chloroform mixtures. On the basis of these results we have developed
Amino Acid Catalyzed Direct Asymmetric Aldol Reactions: A Bioorganic Approach to Catalytic Asymmetric Carbon−Carbon Bond-Forming Reactions
作者:Kandasamy Sakthivel、Wolfgang Notz、Tommy Bui、Carlos F. Barbas
DOI:10.1021/ja010037z
日期:2001.6.1
lack of nonlinear effects. The reactions tolerate a small amount of water (<4 vol %), do not require inert reaction conditions and preformed enolate equivalents, and can be conveniently performed at room temperature in various solvents. In addition, reaction conditions that facilitate catalyst recovery as well as immobilization are described. Finally, mechanistically related addition reactions such as
Development of an Effective Chiral Auxiliary for Hydroxyalkyl Radicals
作者:Philip Garner、James T. Anderson、Philip B. Cox、Stephen J. Klippenstein、Ray Leslie、Noemi Scardovi
DOI:10.1021/jo010880f
日期:2002.8.1
development of an effective chiral auxiliary for hydroxyalkylradicals is delineated. Both the 2-tetrahydropyranyl (THP) and tri-O-benzyl-2-deoxy-alpha-D-glucopyranosyl (GLU) auxiliaries resulted in diastereoselective radical additions to methyl acrylate at -78 degrees C (ds = 6/1 and 11/1, respectively). The developing stereochemistry at the radical center was completely under auxiliary control. Correlation
Direct asymmetric aldol reactions in aqueous media catalyzed by a β-cyclodextrin–proline conjugate with a urea linker
作者:Kegang Liu、Guoqi Zhang
DOI:10.1016/j.tetlet.2014.11.084
日期:2015.1
Covalently attaching proline to beta-CD through a urea linkage resulted in the synthesis of a water-soluble chiral organocatalyst 1 in high yield. Catalytic asymmetric aldol condensations between aldehydes and acetone were carried out under water-containing conditions by using 5 mol % of 1 as catalyst, and moderate to high yields and enantioselectivities (up to 99% ee) were achieved for a broad range of aldehydes. Substrate selectivity was also tested. Recycling experiments were performed to confirm good recyclability and reusability of the catalyst. (C) 2014 Elsevier Ltd. All rights reserved.
Kinetic Resolution of 4-Hydroxy-2-ketones Catalyzed by a Baeyer–Villiger Monooxygenase