Lewis Base Catalyzed, Enantioselective Aldol Addition of Methyl Trichlorosilyl Ketene Acetal to Ketones
- 20 May 2005
- journal article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 70 (13) , 5235-5248
- https://doi.org/10.1021/jo0506276
Abstract
The catalytic enantioselective addition of an acetate enolate equivalent to ketones is described. Methyl trichlorosilyl ketene acetal reacts with a wide range of ketones in the presence of pyridine N-oxide to afford the aldol addition products in excellent yields. Chiral 2,2‘-pyridyl bis-N-oxides bearing various substituents at the 3,3‘- and 6,6‘-positions also provide excellent yields of the aldol products with variable enantioselectivities ranging from 94/6 er for aromatic ketones to nearly racemic for aliphatic ketones. An X-ray crystal structure of the complex between a catalyst and silicon tetrachloride (((P)-(R,R)-19·SiCl4)) has been obtained. Extensive computational analysis provides a stereochemical rationale for the observed trends in enantioselectivities.Keywords
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