Efficient carbazole synthesis via Pd/Cu-cocatalyzed cross-coupling/isomerization of 2-allyl-3-iodoindoles and terminal alkynes.

The Pd/Cu-cocatalyzed one-pot reaction of 2-allyl-3-iodo-1-tosyl-1H-indoles and terminal alkynes afforded carbazoles highly efficiently via sequential carbon-carbon coupling, isomerization, cyclization, and aromatization forming a benzene ring. Both Pd and Cu are responsible for the coupling step, while K2CO3 was observed to be critical for the subsequent cyclization.