π-Conjugated carbocycles and heterocycles via annulation through C-H and X-Y activation across CC triple bonds

In this account our own research results on the methods of annulation and hetero-annulation across alkynes are summarized, especially emphasizing the annulation and hetero-annulation through C-H and X-Y activation. A wide range of quinolines, isoquinolines, indoles, benzofurans, indenes, and benzothiophenes can be synthesized via mono-annulation of ortho-alkynylaryl derivatives using transition metal catalysts and/or iodine reagents. Benzocarbazoles, benzonaphthothiophenes, and indenochromenes can be synthesized via cascade annulation of 1,2-dialkynyl substituted benzene derivatives. Palladium-catalyzed crossover annulation of compounds bearing two vicinal CC triple bonds attached to an unsaturated ring gives dibenzopentalenes through C-H activation, and intramolecular cross annulation of bis-biarylalkynes affords 9,9-bifluorenylidenes via dual C-H activation.