One-Pot Construction of Indolo[2,3‑<i>b</i>]quinoxalines through Ruthenium-Catalyzed <i>Ortho</i> C–H Bond Functionalization of 2‑Arylquinoxalines with Sulfonyl Azides

The synthesis of N-substituted indolo­[2,3-b]­quinoxalines has been developed through a Ru­(II)-catalyzed ortho C–H functionalization of 2-arylquinoxalines with sulfonyl azides and further oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in one pot. This double C–N bond formation strategy provides a new efficient route for the preparation of a series of biologically relevant 6H-indolo­[2,3-b]­quinoxaline derivatives in up to 94% yield, suggesting a broad substrate scope applicability. The preliminary mechanistic studies reveal that the sequential C–N bond formations proceed through the formation of a five-membered ruthenacyclic intermediate in the first step and a radical mechanism in the second step.