Facile synthesis of 9H-pyrrolo[1,2-a]indoles via Bronsted acid catalyzed cascade reactions

An efficient Bronsted acid catalyzed Friedel-Crafts alkenylation/1,6-addition/condensation cascade reaction has been developed. This protocol enables effective access to various highly functionalized 9H-pyrrolo[1,2-a]indoles in moderate to high yields. Mechanistic studies indicate that the in situ vinylogous reactivity intermediate might be formed in the catalytic system.