On the stereochemistry of anion-accelerated [1,3]-sigmatropic rearrangement of 2-vinylcyclobutanols
作者:Se-Ho Kim、Sung Yun Cho、Jin Kun Cha
DOI:10.1016/s0040-4039(01)01929-3
日期:2001.12
Stereochemical studies on the oxyanion-accelerated [1,3]-sigmatropicrearrangement reactions of nonracemic cis- and trans-2-(1-cyclohexenyl)cyclobutanols are described. Epimerization of cis-2-(1-cyclohexenyl)cyclobutanol to the trans-isomer at −20°C was found to proceed with predominant retention of configuration, the degree of which was enhanced by an increasing amount of 18-crown-6.
Control of stereochemistry in potassium alkoxide accelerated [1,3] sigmatropic rearrangements by the use of a crown ether for the apparent destruction of ion pairs. Evidence for a fragmentation mechanism in a vinylcyclobutane rearrangement