On the stereochemistry of anion-accelerated [1,3]-sigmatropic rearrangement of 2-vinylcyclobutanols

Stereochemical studies on the oxyanion-accelerated [1,3]-sigmatropic rearrangement 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.