ASYMMETRIC ALDOL ADDITION OF ALDEHYDES TO A DIFLUOROKETENE SILYL ACETAL CATALYZED BY CHIRAL LEWIS-ACIDS

Authors
ISEKI K KUROKI Y ASADA D TAKAHASHI M KISHIMOTO S KOBAYASHI Y
Citation
K. Iseki et al., ASYMMETRIC ALDOL ADDITION OF ALDEHYDES TO A DIFLUOROKETENE SILYL ACETAL CATALYZED BY CHIRAL LEWIS-ACIDS, Tetrahedron, 53(30), 1997, pp. 10271-10280
Citations number
34
Categorie Soggetti
Chemistry Inorganic & Nuclear
Journal title
Tetrahedron → ACNP
ISSN journal
00404020
Volume
53
Issue
30
Year of publication
1997
Pages
10271 - 10280
Database
ISI
SICI code
0040-4020(1997)53:30<10271:AAAOAT>2.0.ZU;2-U
Abstract
Aldol reaction of aldehydes with difluoroketene ethyl trimethylsilyl a cetal (1) in the presence of a substoichiometric amount of chiral Lewi s acid 2 or 3 provides the corresponding alpha,alpha-difluoro beta-hyd roxy esters 4-12 with high enantioselectivities (up to 98% ee). Reacti on temperature has a great influence on the enantiofacial selection of aldehydes; the reactions of benzyloxyacetaldehyde catalysed by Lewis acid 2 at -78 and -30'C gave the (+)- and (-)-alpha,alpha-difluoro bet a-hydroxy esters 7 in optical yields of 98% and 85%, respectively. (C) 1997 Elsevier Science Ltd.