6-endo-dig Cycloisomerization of N-Propargyl Aminoquinoxalines: A New Route to 1,4,8-Triazaphenanthrenes

We report the preparation of novel 1,4,8-triazaphenanthrenes and show that the target compounds are efficiently obtained from the corresponding 6-aminoquinoxalines after N-propargylation followed by copper-catalyzed 6- endo -dig cycloisomerization and aromatization. The cyclization was found to be completely regioselective.