Two-Carbon Annulation of N-Arylpyrroles to Benzoindoles and Pyrroloquinolines

Significance

Reported is a Pd-catalyzed synthesis of nitrogen-containing condensed heterocycles 3 which involves an annulation of N-aryl­pyrrole 1 with a strained alkene, followed by an in situ retro-Diels-Alder reaction of the intermediate 2. Achievement of heteroaromaticity appears to be the driving force. It is an interesting one-step process, based on the Catellani methodology (M. Catellani Synlett 2003, 298-313) to give heterocycles 3 in good to excellent yields. The functional group tolerance and scope of substrates were not sufficiently investigated.