Synthesis of Pyrroles, Indoles, and Carbazoles through Transition-Metal-Catalyzed C-H Functionalization

Pyrroles, indoles, and carbazoles are among the most important families of nitrogen-containing heterocycles that occur frequently in natural products, pharmaceuticals, agrochemicals, and other functional molecules. Consequently, improved syntheses of these compounds continue to interest synthetic chemists. This Focus Review describes recent advances in synthetic methods for producing these privileged heterocycles that feature transition-metal-catalyzed C-H activation approaches. Because of the common five-membered pyrrole core, some of the C-H activation approaches are applicable to two or more of the pyrrole, indole, and carbazole skeletons. The reactions discussed here not only serve as atom-and step-economical alternatives to the existing synthetic methods, but also show the latest developments in organometallic chemistry and homogeneous catalysis.