Web Release Date: June 4,
A Highly Efficient Organocatalyst for Direct Aldol Reactions of Ketones with Aldedydes
Contribution from the Key Laboratory for Asymmetric Synthesis and Chirotechnology of Sichuan Province, Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041, China, and Graduate School of Chinese Academy of Sciences, Beijing, China
Received February 17, 2005
Abstract:
L-Proline amides derived from various chiral 
-amino alcohols that bear substituents with various
electron natures at their stereogenic centers are prepared and evaluated for catalyzing the direct Aldol
reaction of 4-nitrobenzaldehyde with acetone. Catalysts with strong electron-withdrawing groups are found
to exhibit higher catalytic activity and enantioselectivity than their analogues with electron-donating groups.
The presence of 2 mol % catalyst 4g significantly catalyzes the direct Aldol reactions of a wide range of
aldehydes with acetone and butanone, to give the -hydroxy ketones with very high enantioselectivities
ranging from 96% to >99% ee. High diastereoselectivity of 95/5 was observed for the anti Aldol product
from the reaction of cyclohexanone, and excellent enantioselectivity of 93% ee was provided for anti Aldol
product from the reaction of cyclopentanone.
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