A Tandem Approach to Functionalized Carbazoles from Indoles via Two Successive Regioselective Oxidative Heck Reactions Followed by Thermal Electrocyclization

A direct one-pot approach to the synthesis of carbazoles (mono-, di-, and trisubstituted) and alpha-carbolines from readily available indoles or 7-azaindoles and alkenes is described. Based on mechanistic studies, the tandem reaction follows the sequence: palladium-catalyzed regioselective C-3 alkenylation/palladium-catalyzed C-2 alkenylation/thermal electrocyclization.