Radical Cascade Cyclization of Unactivated Alkene-Tethered Indoles with Aryldiazonium Salt and Sodium Metabisulfite to Access Azo- and Sulfonylated-2,3-Dihyro-1 H -pyrrolo[1,2- a ]indoles.

A method for the construction of heterocyclic scaffold 2,3-dihyro-1 H -pyrrolo[1,2- a ]indoles via arylsulfonyl radical-triggered cascade cyclization of unactivated alkene-tethered indoles in the absence of any external photocatalyst has been developed. This protocol features easily accessible starting materials such as sodium metabisulfite and aryldiazonium tetrafluoroborates at room temperature and offers good functional group compatibility, enabling the introduction of various functionalized sulfonyl and azo groups into pyrrolo[1,2- a ]indoles.