trans-cycloalkenes. Part 10. Reactions of bicyclic trans-cyclo-octenes constrained in chair and twist conformations

Abstract

The following reactions of twist and chair bicyclic trans-cyclo-octenes (1) and (2), and (3) and (4) have been investigated : isomerisation with iodine, epoxidation, Diels–Alder addition of butadiene, addition of phenyl azide and pyrolysis of the resulting triazolines, and addition of iodine azide. In most cases diastereoisomeric products were produced from each olefin and in one case, addition of iodine azide, constitutionally different products were obtained. The chair isomer (4) is converted to the twist isomer (3) at 150 °C, and from ΔG^‡ For this process it is estimated that the twist isomer is some 14 kJ mol^–1 thermodynamically more stable than the chair form.