Preparation and Properties of Annelated Tropylium Salts

Article abstract of DOI:10.1021/jo00152a037

The insertion of methylene into the aromatic ring of benzocyclobutene leads to a mixture of cyclobutane-fused cycloheptatrienes.Treatment of this mixture with a trityl salt affords the cyclobutane-fused tropylium salt in essentially pure form.If this same synthetic approach is applied to other annelated benzenes, bis- and tris-annelated salts can be prepared.The proton and carbon-13 NMR spectra of a series of annelated tropylium salts have been analyzed and interpreted in terms of a rehybridization theory.Small but meaningful trends have been observed in the ultraviolet absorption spectra and pK_R⁺ values.