Gas Phase Thermal Reactions of exo-8-Cyclopropyl-bicyclo[4.2.0]oct-2-ene (1- exo)

Abstract

The title compound 1- exo (with minor amounts of its C8 epimer 1- endo ) was prepared by Wolff-Kishner reduction of the cycloadduct of 1,3-cyclohexadiene and cyclopropylketene. The [1,3]-migration product 2- endo was synthesized by efficient selective cyclopropanation of endo-5-vinylbicyclo[2.2.2]oct-2-ene at the exocyclic π-bond. Gas phase thermal reactions of 1- exo afforded C8 epimerization to 1- endo , [1,3]- migrations to 2- exo and 2- endo , direct fragmentation to cyclohexadiene and vinylcyclopropane, and CPC rearrangement in the following relative kinetic order: k _ep > k ₁₃ > k _f > k _CPC .