Direct Observation of Gold/Palladium Transmetalation in an Organogold Heck Reaction

A new Heck-type reaction accessed the migratory insertion chemistry of palladium from organogold complexes. Observation, isolation, and characterization of a palladium intermediate established the role of gold/palladium transmetalation in this reaction. Recent reports of combining the reactivity of organogold compounds with palladium in organic synthesis generally assume a gold-to-palladium transmetalation step, although this step had not been directly observed in these reactions. The results herein furnish experimental evidence for the mechanisms of reactions mediated or catalyzed by both gold and palladium and reveal a migratory insertion strategy for outcompeting homocoupling pathways.