The Protonated Cyclopropane Route to Bicyclic Cations

Article abstract of DOI:10.1021/jo00380a007

The protolytic cleavage of tricyclo<2.2.0.0^2,6>hexane (3), tricyclo<3.2.0.0^2,7>heptane (10), methyltricyclo<3.2.0.0^2,7>heptanes (26), tricyclo<3.3.0.0^2,8>octane (53), and tricyclo<3.2.1.0^2,7>octane (58) in acetic acid and in aqueous dioxane has been investigated.Protonation occurred at a specific site (3, 36b,d, 58) or competitively at two sites (10, 26c, 53), depending on the stability of the incipient carbocations.Product distributions and label redistributions, where applicable, were in good to excellent agreement with previous solvolytic studies.We conclude that the protonated cyclopropane and ? routes are equivalent in generating bridged carbocations.Edge-protonated cyclopropanes play a minor role, if any, in product formation.Stereoselectivity appears to be an intrinsic property of the cationic intermediates, largely independent of the specific orientation of their counterions.