The aldol reactions of trimethoxysilyl enol ethers catalyzed by lithium binaphtholate were found to be powerful tools for the construction of quaternary asymmetric carbon centers. The stereoselectivities were greatly affected by the presence of water. Trimethoxysilyl enol ether derived from a cyclic ketone, such as cyclohexanone, was used as a substrate to obtain the anti-adduct preferentially under anhydrous conditions; by contrast, the syn-adduct was preferentially obtained under aqueous conditions with high stereoselectivity. The aldol-Tishchenko reaction of a trimethoxysilyl enol ether derived from acyclic ketones proceeded to give monoacyl 1,3-diol derivatives in high enantioselectivities. (C) 2012 Elsevier Ltd. All rights reserved.
Highly Regioselective Lewis Acid-Mediated Aldol Additions at the More Encumbered α-Side of Unsymmetrical Ketones
作者:Rainer Mahrwald、Bilgi Gündogan
DOI:10.1021/ja973453l
日期:1998.1.1
Alkali Enolates of Unsymmetrical Ketones from Silyl Enol Ethers. Highly Regioselective Aldol Reactions Dependent on the Nature of the Cation