Journal
TETRAHEDRON
Volume 64, Issue 37, Pages 8668-8675Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2008.07.001
Keywords
inherently chiral calix[4]arene; organocatalyst; enantioselective aldol reaction
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Funding
- National Natural Science Foundation of China [20625206]
- National Basic Research Program [2007CB808004, 2008CB617501]
- Chinese Academy of Sciences
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Two optical pure m-dimethylamino substituted inherently chiral calix[4]arene derivatives 8a and 8b bearing an L-prolinamido group have been synthesized by two routes, and structurally studied by the usual spectroscopic methods and X-ray crystallographic analysis. It was found that both of 8a and 8b could be utilized as bifunctional organocatalysts to efficiently promote the aldol reactions between aromatic aldehydes and ketones in the presence of acetic acid. Especially, with 8a as the catalyst, the reaction between 4-nitrobenzaldehyde and cyclopentanone at -20 degrees C gave the anti-aldol product up to 94% ee, while the anti-aldol product in up to 94:6 dr and 79% ee was obtained when 4-cyanobenzaldehyde was used as the aldol donor. Moreover, it was also demonstrated that the inherently chiral calixarene skeleton with (cS)-conformation in 8a was identified as the matched configuration of the stereogenic elements, and the inherently chiral moiety might play an important role in helping to stereocontrol the reaction. (c) 2008 Elsevier Ltd. All rights reserved.
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