title: Acid-catalyzed rearrangement of ethynylcycloheptatriene to phenylallene.
abstract: 7-Ethynylcycloheptatriene (1) cleanly isomerizes to phenylallene in the presence of acid. A mechanism involving the protonation of ethynylnorcaradiene, which is in equilibrium with 1, followed by the cleavage of a three-membered ring to give an arenium ion, is proposed. The rearrangement is accelerated by a factor of 370 by introducing tert-butyl groups on C-2 and C-5, indicating the importance of the equilibrium concentration of the norcaradiene form as a rate-controlling factor.
authors.affiliation: Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. kitagawa@scl.kyoto-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Kitagawa
authors.forename: J
authors.initials: J
authors.lastname: Kamada
authors.forename: S
authors.initials: S
authors.lastname: Minegishi
authors.forename: K
authors.initials: K
authors.lastname: Takeuchi