Palladium-Catalyzed Intermolecular Acylation of Aryl Diazoesters with ortho-Bromobenzaldehydes.

In this work, we describe a palladium-catalyzed intermolecular O acylation of α-diazoesters with ortho-bromobenzaldehydes. The C(sp2 )-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.