A novel oxygen-catalysed trans–cis thermal isomerization of trans-cycloheptene

Abstract

Contrary to the efficient unimolecular decay to the cis-isomer under an atmosphere of nitrogen, trans-cycloheptene, prepared photochemically in situ at low temperature, underwent second-order trans–cis thermal isomerization under an atmosphere of air without giving any oxidation products. The rate constants and activation parameters are reported for this unique isomerization reaction. Following discussion of the role of oxygen in the isomerization process we propose a mechanism involving termolecular interaction between triplet oxygen and two molecules of the strained cycloalkene.