Iridium(III) Photocatalysis: A Visible-Light-Induced Dearomatizative Tandem [4+2] Cyclization to Furnish Benzindolizidines.

A photocatalytic dearomatizative tandem [4+2] cyclization between N-(2-iodoethyl)indoles and a variety of alkenes leads to tri- and tetracyclic benzindolizidines with high diastereoselectivity and yield. The intermolecular annulation reaction is performed under visible-light irradiation and employs [Ir(ppy)3] or [Ir(dtbbpy)(ppy)2] PF6 as photocatalysts, in combination with tertiary amines as electron and hydrogen atom donors.