Synthesis of Naphtho[1,8‐ bc ]oxepines Through an HFIP‐Promoted P eri ‐Selective Arene–Epoxide Cyclization

We describe a hexafluoroisopropanol (HFIP)‐promoted epoxide ring‐opening cyclization of readily accessible 2‐[(2‐substituted‐1‐naphthyloxy)methyl]‐3‐aryloxiranes, proceeding via a regioselective 7‐ endo cyclization at the peri (C8) position of the naphthalene ring. This transformation provides a new class of naphtho[1,8‐ bc ]oxepine derivatives with complete regio‐ and diastereoselectivity. The C2 substituent on the naphthalene framework, along with the π ‐activating aryl group on the epoxide, plays a pivotal role in enabling the reaction. The method operates under mild conditions, tolerates a broad substrate scope, and is readily amenable to gram‐scale synthesis. Moreover, the versatility of this strategy is underscored by its successful extension to the diastereoselective synthesis of oxepino[4,3,2‐ cd ]indoles.