Persistence of stereoselectivity in the thermal cyclizations of 5-alkenylcyclohexa-1,3-dienes; a novel route to some functionalized bridged tricyclic rings

Abstract

Heating of 5-pent-4-enylcyclohexa-1,3-diene at 210° leads to predominantly tricyclo[5,3,1,0^3,8]undec-9-ene, along with minor amounts of the epimeric tricyclo[5,2,2,0^1,5]undec-8-enes which are probably formed through a competing sequence involving the intermediate 1-pent-4-enylcyclohexa-1,3-diene; ketones corresponding in their skeletal structure to the tricyclic hydrocarbons have been obtained by heating α-pyrone with hepta-1,6-dien-3-one.