Synthesis of ester-functionalized indolo[2,1-a]isoquinolines via iron-catalyzed radical cascade cyclization of 2-aryl-N-acryloyl indoles with carbazates

An FeCl₂·4H₂O-catalyzed oxidative alkoxycarbonylation/cyclization reaction of 2-aryl-N-acryloyl indoles with carbazates leading to ester-functionalized indolo[2,1-a]isoquinoline derivatives has been developed. The reaction features mild reaction conditions and broad functional group tolerance. Moreover, the ester group could be easily converted to the corresponding free acid and alcohol, and has high potential applications in organic and pharmaceutical synthesis. A radical pathway was proposed to explain this experiment.