Synthesis of 2,3-benzoxepins by sequential cyclopropanation/ring-enlargement reactions of benzopyrylium triflates with diazoesters

Transition metals in organic synthesis: Highlights for the year 2005

“…Silver catalyzed the reaction of ethyldiazoethanoate with aromatic compounds forming cycloheptatrienes [753]. A related copper-catalyzed ring-expansion of benzopyrylium triflates was reported affording 2,3-benzooxepins [754].…”

Reductive (3 + 2) Annulation of Benzils with Pyrylium Salts: Stereoselective Access to Furyl Analogues of cis-Chalcones

“…The ring-closure of 42 generated a pair of cyclopropane diastereomers, trans - 43 and cis - 43 , through stepwise polar cyclopropanation . Facile isomerization between trans - 43 and cis - 43 occurs via a valence tautomeric interconversion between 43 and oxepinium 44 , like the venerable norcaradiene/cycloheptatriene system . Similar to the mechanism of the Paal–Knorr furan synthesis reported by Amarnath et al, an intramolecular cyclization of cis - 43 through intermediates 45 and 46 leads to the final product 47 .…”

Acid- and Base-Promoted Rearrangements of Cycloalkane-Fused Heterocycles

“…2,3-Benzoxepines such as 34 generally reside in their oxepine form, since rearrangement of the latter to the corresponding naphthalene oxide derivative would interrupt the aromaticity of the anullated benzene moiety [17].…”