Metal-Catalyzed Domino Synthesis of Benzophenanthridines and 6H‑Naphtho[2,3‑c]‑chromenes

A new and efficient synthesis of tetracyclic phenanthridines and benzo­[c]­chromenes has been described involving a metal-mediated two-step domino strategy. The first step involved efficient palladium-catalyzed domino carbopalladation/cross coupling, and the second step involved iron-catalyzed domino isomerization/cyclodehydration. The important features of this strategy include high yields, generality, wide substrate scope, and broad functional group tolerance. A plausible mechanism has been proposed to explain the formation of the product.