Synthesis of Novel Isoquinolino[5,4-ab]phenanthridine Derivatives via Pictet–Spengler Reaction

The reaction of 5-amino-2-[2-(dimethylamino)ethyl]-6-phenyl-1H-benzo[de]isoquinoline-1,3(2H)-dione with a series of aldehydes in acidic media (phosphoric acid, trifluoromethanesulfonic acid, and trifluoroacetic acid) is described. This key step is based on the Pictet–Spengler reaction to synthesize ten novel isoquinolino[5,4-ab]phenanthridine derivatives. The most effective acid is phosphoric acid and optimized yields were obtained. The frameworks of target compounds are unique and have never been reported.