Efficient two-step synthesis of structurally diverse indolo[2,3-b]quinoline derivatives.

A general and efficient synthesis of diverse tetracyclic indolo[2,3-b]quinoline derivatives was achieved through palladium-catalyzed domino carboannulation/cross-coupling and DDQ-mediated double cross-dehydrogenative C-N bond formation. This approach provides a straightforward, atom-economical and concise route to easily access a diverse range of tetracyclic indolo[2,3-b]quinolines and their analogues in excellent yields with good tolerance of functional groups.