Cationic gold(I) complexes favor formation of six- and seven-membered rings by 6-endo-dig, 6-exo-dig, and 7-exo-dig cyclizations of alkynyl indoles, whereas indoloazocines are favored with AuCl3 as catalyst (see scheme). Allenes are also formed by a fragmentation process.
![Gold-catalyzed intramolecular reaction of indoles with alkynes: Facile formation of eight-membered rings and an unexpected allenylation](https://www.iciq.org/wp-content/uploads/2014/03/Gold-catalyzed-intramolecular_eng_noticies_articles_2006_70.gif)