Cyclization of Vinyl and Aryl Azides into Pyrroles, Indoles, Carbazoles, and Related Fused Pyrroles

This chapter reviews in detail those reactions that form of a new pyrrole ring from vinyl, aryl, and heteroaryl azides via formal C–H insertion processes under thermal, photochemical, and metal-catalyzed conditions. These reactions proceed via the intermediacy of vinyl or aryl nitrenes (or their metallonitrene equivalents) and generate a wide variety of pyrroles, indoles, carbazoles, and related systems. Methods for the synthesis of the starting azides are summarized, and a comprehensive survey of the cyclization processes is provided. Keywords: pyrrole; indole; carbazole; azidoalkene; azidoarene; vinyl nitrene; aryl nitrene; thermolysis; photolysis; metal catalysis; C–H functionalization; nitrene; 2-azidostyrene; 2-azidobiphenyl