Annulation via Ring Opening/Cyclization of Donor‐Acceptor Cyclobutanes with 2‐Naphthols: Access to Highly Functionalized Naphthalene‐Fused Oxepines

Abstract A mild and straightforward access to various substituted naphthalene‐fused oxepines from readily available Donor‐Acceptor (D‐A) cyclobutanes is reported. This method involves the Lewis acid‐catalyzed reactions of D‐A cyclobutanes with 2‐naphthols to afford ring‐opened products, which can undergo intramolecular cyclization mediated by the NBS‐base system to yield corresponding naphthalene‐fused oxepines. The cyclization protocol involves a nucleophilic attack of the oxygen of 2‐naphthol on the newly formed electrophilic acceptor end of D‐A cyclobutane.