Proline-Catalyzed Ketone-Aldehyde Aldol Reactions are Accelerated by Water
作者:Petri Pihko、Annika Nyberg、Annina Usano
DOI:10.1055/s-2004-831296
日期:——
Proline-catalyzed aldol reactions between acetone or 4-thianone and different aldehydes are accelerated by addition of 1-10 equivalents of water to the reaction medium, allowing stoichiometric aldol reactions to proceed at acceptable rates.
Effect of additives on the proline-catalyzed ketone–aldehyde aldol reactions
作者:Petri M. Pihko、Katri M. Laurikainen、Annina Usano、Annika I. Nyberg、Jatta A. Kaavi
DOI:10.1016/j.tet.2005.09.070
日期:2006.1
The effect of bases, acids, and water as additives in proline-catalyzed ketone–aldehyde aldol reactions has been studied. While the reaction appears to be relatively tolerant to small amounts of tertiary amine bases or weak acids, it stops completely with strong acids. The use of water as an additive had a highly beneficial effect on reactions that were conducted with a stoichiometric ratio of ketone
(S)-NOBIN-L-prolinamide was employed as organocatalyst in the direct aldol reactions of different ketones and aromatic aldehydes using dioxane as solvent and in the presence of water as additive. Acetone led to the aldol products in up to 93% ee, while cyclic ketones furnished the anti-aldols in moderate to high yield, excellent diastereoselectivity (up to > 99/< 1 anti/syn ratio) and high ee (up to 95%). (c) 2007 Elsevier Ltd. All rights reserved.