Total Regio- and Diastereocontrol in the Aldol Reactions of Dienolborinates
摘要:
It is reported that appropriate dienolborinates can provide access to both diastereomers of 2-(hydroxymethyl)but-3-enoates through exclusive alpha-regiocontrol in a non-vinylogous pathway. Contrary to previous reports in which dialkylchloroboranes failed to enolize propanoates, acidity-enhanced but-3-enoates readily undergo enolization, offering unprecedented control over the formation of these valuable synthons. The first example of an aldol reaction in the presence of a phosphine-borane adduct is also reported.
Synthesis of α-alkenyl-β-hydroxy adducts by α-addition of unprotected 4-bromocrotonic acid and amides with aldehydes and ketones by chromium(II)-mediated reactions
作者:Ludger A. Wessjohann、Harry Wild、Leonildo A. Ferreira、Henri S. Schrekker
A NEW METHOD FOR THE SYNTHESIS OF β-HYDROXYESTERS BY USING METALLIC TIN
作者:Taira Harada、Teruaki Mukaiyama
DOI:10.1246/cl.1982.161
日期:1982.2.5
Metallic tin or activated metallic tin, prepared by reduction of stannous chloride with lithiumaluminumhydride, smoothly reacts with α-haloesters to yield tin enolates, which in turn react with carbonylcompounds under mild conditions to give, after hydrolysis, β-hydroxyesters in high yields.