Palladium-Catalyzed Triple Successive C–H Functionalization: Direct Synthesis of Functionalized Carbazoles from Indoles

A novel Pd­(II)-catalyzed approach for the direct synthesis of differentially substituted carbazoles from free (NH) indoles via regioselective triple successive oxidative Heck (Fujiwara–Moritani reaction) has been achieved. It is demonstrated that both electron-deficient and electron-rich alkenes could be used successively for the incorporation of two different functional groups into the product. The proposed mechanistic pathway was well supported by isolating the first and second successive oxidative Heck intermediates as well as by trapping with styrene-d3.