Synthesis of pyrrolo[2,3-b]indole via iodine(III)-mediated intramolecular annulation.

New synthetic procedures for the pyrrolo[2,3-b]indole skeleton have been developed via intramolecular annulation of indole derivatives under iodine(III). A series of indole derivatives with different protecting groups or substitutions were explored to facilitate the corresponding pyrrolo[2,3-b]indole compounds in excellent yields.