Palladium‐Catalyzed Intermolecular Acylation of Aryl Diazoesters with ortho‐Bromobenzaldehydes

Abstract In this work, we describe a palladium‐catalyzed intermolecular O acylation of α‐diazoesters with ortho ‐bromobenzaldehydes. The C(sp 2 )−H bond activation of the aldehyde is enabled by migratory insertion of a palladium carbene intermediate. The diazoesters act as modular three‐atom units to build up key seven‐membered palladacycles, which are transformed into a variety of isocoumarin derivatives upon reductive elimination. Mechanistic experiments and DFT calculations provide insight into the reaction pathway.