Palladium-Catalyzed [2 + 2 + 2] Annulation via Transformations of Multiple C-H Bonds: One-Pot Synthesis of Diverse Indolo[3,2- a]carbazoles.

A Pd-catalyzed novel cascade reaction has been developed for the synthesis of indolo[3,2 a]carbazoles involving multiple C-H transformation-annulations between the indoles and alkynes. The method involves molecular oxygen as the sole oxidant and is an effective and step-economic process.