Indium-catalyzed Annulation of Indoles with Ethyl (2-Ethynylaryl)methyl Carbonates: Synthesis and Photoluminescent Properties of Aryl- and Heteroaryl[b]carbazoles

Two successive carbon–carbon bond-forming annulation of indoles with ethyl (2-ethynylaryl)methyl carbonates and their heteroaryl analogs under indium catalysis provided aryl- and heteroaryl[b]carbazoles, photoluminescent properties of which were then evaluated and compared with those of the corresponding [a]- and [c]-types, thereby showing that the order of light-emitting efficiency is [a]- < [b]- < [c]-type.