Brønsted acid-catalyzed synthesis of benzo[f]indole and naphtho[2,3-b]furan derivatives via an intramolecular cascade isomerization/cyclization/aromatization.

Herein, we demonstrated a PTSA-catalyzed facile and efficient synthesis of tricyclic benzo[f]indole and naphtho[2,3-b]furan derivatives via a cascade isomerization/cyclisation/aromatisation reaction in good yields. This protocol offers several advantages, including ease of preparation of the substrate, metal-free reaction conditions, broad functional group tolerance, mild reaction conditions, and a wide range of substrate scope.