Palladium-mediated synthesis of a new eight-membered heterocycle

The eight-membered heterocycle 3 has been prepared in 94% isolated yield starting from phenylnorbornylpalladium chloride dimer, o-iodoacetanilide and carbon monoxide in DMF at room temperature. Compound 3 has been unequivocally characterized by X-ray single crystal diffraction. Formation of 3 must involve coordination of the amido group to palladium which prevents ring closure to a hexahydromethanotriphenylene derivative.