Transition Metal‐Free Heteroarene Insertion Into C─C Bonds of Benzocyclobutenones

The insertion of five‐membered heteroarenes into the C─C bonds of benzocyclobutenones (BCBs) has been achieved. This process proceeds under mild conditions and does not require the use of a transition metal catalyst. A variety of fused polycyclic compounds based on indoles, 7‐azaindoles, benzothiophenes, benzofurans, and thiophenes relevant to bioactive scaffolds are efficiently accessed through this approach. The reaction is scalable, and the products are suitable for various late‐stage derivatizations. Preliminary mechanistic studies reveal a catalytic role of base in facilitating C─C bond cleavage to generate a reactive intermediate which likely engages in subsequent dearomative cycloaddition with heteroarenes.