Ring Expansion via Cleavage of Benzylic C-C Bonds Enabling Direct Synthesis of Medium Ring-Fused Benzocarbocycles

A fluoride-anion-induced, regioselective ring expansion of benzocyclic ketones and -aryl cycloketones has been developed via insertion of arynes into unactivated benzylic C-C bonds. This reaction provides a straightforward, transition-metal-free avenue to prepare medium ring-fused benzocarbocycles by creating noble seven-, eight-, and nine-membered rings. Applications of this method in the creation of medium-sized exocyclic and inner benzocyclic olefins, nine-membered lactones, and lactams are described.