TfOH-Catalyzed Synthesis of Bis(pyrrolo[2,1-a]isoquinolinyl) methanes

Abstract The synthesis of bis(pyrrolo[2,1-a]isoquinolinyl)methanes was achieved through TfOH-catalyzed sequential Friedel–Crafts alkylation of pyrrolo[2,1-a]isoquinoline and aldehyde. A series of highly functionalized bis(pyrrolo[2,1-a]isoquinolinyl)methane derivatives can be obtained in acceptable to excellent yields (11 examples, up to 96% yield). Interestingly, deformylation was observed when treating pyrrolo[2,1-a]isoquinoline-derived aldehyde and indole under the current reaction conditions. Furthermore, the replacement of aldehyde with isatin resulted in the formation of methylene-bridged dimeric pyrrolo[2,1-a]isoquinoline.