Summary: o-Aryloxenium ions undergo intramolecular C-0-C bond formation readily as shown by the cyclizations yielding dibenzofurans. m-Aryloxenium ions cyclize via CC bond formation provided the molecule can adopt the appropriate conformation for ring closure to occur. When an oxygen atom is ortho to the T-aryl cation center, cyclization to form five-or six- membered rings does not occur and this is attributed to an interaction between oxygen ...