Opening of the cyclopropane ring of the thujan-3-ols in fluorosulphuric acid

Abstract

The reactions of the isomeric thujan-3-ols with fluorosulphuric acid to give the 2,3-dimethyl-4-isopropylcyclopentenium ion have been investigated. The initial ring opening involves at least two mechanisms yielding a carbocation and an olefin. Subsequent reaction, possibly by elimination and olefin shift, gives the 2,3-dimethyl-4-isopropylcyclopent-2-enol, which rapidly ionises to the observed ion. The reaction has been studied by means of deuterium tracers, in the solvent and in the substrate, and by comparison of the reaction with those of related substrates.