Highly regio- and stereocontrolled brominations of gem-difluorinated vinyloxiranes

摘要

gem-Difluorinated vinyloxiranes, which are useful synthetic intermediates for difluorinated compounds, were brominated regio- and stereoselectively. Introduction of bromide at the allylic epoxide carbon with inversion of stereochemistry was realized by (MgBr2Et2O)-Et-. to furnish an anti vic-bromohydrine, whereas the reaction with LiBr/AcOH afforded the other diastereomer selectively. Moreover, both reactions at high temperature allowed to obtain, the thermodynamically favored products, E-allylic alcohols dominantly. (c) 2005 Elsevier Ltd. All rights reserved.