Ring Expansion via Palladium-Catalyzed Aryne Insertion into C-C Bonds of Benzocyclobutenones.

Insertion of arynes into cyclic C-C bonds provides a straightforward approach for ring expansion with an ortho-phenylene moiety; however, the current scope of substrates has been restricted to enolizable ketones. Here we report the first example of aryne-insertion into non-enolizable ketones through Pd-catalyzed C-C bond activation of benzocyclobutenones. 2-Haloaryl boronates were employed as an unconventional aryne precursor. The reaction shows a wide substrate scope and high functional group tolerance. The mechanistic studies reveal an interesting dual role of the Pd catalyst for both aryne generation and C-C bond activation.