Cyclopentadiene–Phosphine/Palladium-Catalyzed Cleavage of C–N Bonds in Secondary Amines: Synthesis of Pyrrole and Indole Derivatives from Secondary Amines and Alkenyl or Aryl Dibromides

An efficient Pd-catalyzed cleavage of C­(sp3)–N bonds in secondary amines and a consequent C­(sp2)–N and C­(sp3)–N coupling process was developed. Various secondary amines could be used to react with alkenyl or aryl dibromides, affording pyrroles and indoles in high yields. Cyclopentadiene–phosphine ligands, a new type of P–olefin ligand, were found to be able to promote the efficiency of this Pd-catalyzed process remarkably. A reactive Pd complex coordinated with a cyclopentadiene–phosphine ligand was successfully isolated and structurally characterized.