Stereoselective Synthesis of Pyrrolo/Pyrido[2,1-a]isoindoles via Alkyne Iminium Ion Cyclization of Vinylogous Carbamates.

An efficient, acid-mediated, intramolecular alkyne iminium ion cyclization of oxoisoindolidene for the diastereoselective synthesis of pyrrolo/pyridoisoindole is described. This protocol features broad substrate scope and easy scalability. An unusual N to C-1,3-alkyl shift is observed with substrates bearing strong electron donating group at the phenyl ring attached to alkyne with concomitant hydration of alkyne to the ketone.