Construction of quaternary carbon centers by a base-catalyzed enantioselective aldol reaction and related reactions of trimethoxysilyl enol ethers
摘要:
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.
Aldol reaction of trichlorotitanium enolates. Revaluation of the boat transition state
作者:Eiichi Nakamura、Isao Kuwajima
DOI:10.1016/s0040-4039(00)86265-6
日期:1983.1
The trichlorotitanium enolates generally undergo an erythro selective aldolreaction except one case which gives a threo aldol. A new form of the boat transition state has been proposed.