Asymmetric catalysis with chiral Lewis bases
Journal
Pure and Applied Chemistry
Journal Volume
70
Journal Issue
8
Pages
1469-1476
Date Issued
1998
Author(s)
Abstract
The trichlorosilyl enolates of methyl ketones, ethyl ketones and cycloalkanones react readily with a variety of aldehydes in aldol addition reactions without external promoters at 0°C - rt. The aldol products are generated in excellent yield and with good to excellent diastereoselectivity (E to syn, Z to anti). In the presence of catalytic amounts (5-15 mol %) of chiral phosphoramide promoters the aldol reactions of enoxytrichlorosilanes now proceed rapidly at -78°C and are extremely diastereoselective (E to anti, Z to syn, 61-99/1). The products are afforded with good to excellent enantioselectivity (anti: 82-97% ee, syn: 58-96% ee).
Type
journal article