Gold-catalyzed benzannulations of 2-alkenylindoles with alkynes: a protecting-group-free regioselective approach to carbazoles.

A gold(I)-catalyzed protecting-group-free benzannulation approach to functionalized NH-carbazoles was accomplished via the hydroarylation of alkynes with 2-alkenylindoles. A broad spectrum of terminal and internal alkynes and 2-alkenylindoles successfully participated in this annulation reaction. The protocol efficiently enabled the formation of substituted NH-carbazoles with moderate to specific regioselectivities. The synthetic utility of this protocol was demonstrated by a variety of post-functionalizations.