Palladium-Catalyzed Oxidative Coupling of the Allenic C-H Bond with α-Diazo Esters: Synthesis of [3]Dendralenes.

A palladium-catalyzed highly regio- and stereoselective allenic C-H oxidative coupling with α-diazo esters is developed. The reaction pathway involves allylic palladium carbene as the key intermediate, which is followed by a carbene migratory insertion process. The reaction proceeds efficiently under mild conditions without external base, providing substituted [3]dendralenes bearing various functional groups.