Reactivity of 5-(3-azidophenyl)-1-(1H-pyrrol-3-yl)pyrroles in TFMSA. A route for new ring systems as DNA-interactive agents

Acid catalyzed decomposition of 5-(3-azidophenyl)-1-(1H-pyrrol-3-yl)pyrroles did not afford the expected dipyrrolo[2,1-a:3,4-c]isoquinoline derivatives, but the planar dipyrrolo[2,1-a:3,2-c]isoquinoline derivatives and related non planar derivatives 11bH-dipyrrolo[2,1-a:3,2-c]isoquinoline derivatives. In strong acid media (trifluoromethanesulfonic acid) the α-(1-pyrrol-3yl) position even if blocked, was more prone to undergo cyclization with respect to the free β one. Despite the steric hindrance, these compounds were obtained in moderate to good overall yields, depending on the nature and position of the substituents on the 1-(1H-pyrrolyl) moiety.