Triplet di-π-methane rearrangement of a ‘free-rotor’ 2-prop-2-enylcyclopent-2-enone
Abstract
The 2-prop-2-enylcyclopent-2-enone (1) undergoes an inefficient triplet di-π-methane rearrangement to give (2) whereas the side-chain substituted analogue (4), under similar conditions, undergoes only Z–E-isomerisation; the reactivity differences are rationalised on the basis of dissipation of triplet energy by ‘free-rotor’ effects.