PdII-Catalyzed Di-o-olefination of Carbazoles Directed by the Protecting N-(2-Pyridyl)sulfonyl Group

Despite the significance of carbazole in pharmacy and material science, examples of the direct C–H functionalization of this privileged unit are quite rare. The N-(2-pyridyl)sulfonyl group enables the PdII-catalyzed ortho-olefination of carbazoles and related systems, acting as both a directing and readily removable protecting group. This method features ample structural versatility, affording typically the double ortho-olefination products (at C1 and C8) in satisfactory yields and complete regiocontrol. The application of this procedure to related heterocyclic systems, such as indoline, is also described.