Extended Study of Visible-Light-Induced Photocatalytic [4+2] Benzannulation: Synthesis of Polycyclic (Hetero)Aromatics

Herein we report an extended study of [4 + 2] benzannulation reactions of 2-(hetero)aryl-substituted,anilines with alkynes by visible light photocatalysis. The method requires the use of BuONO as a diazotizing agent and 0.3 mol % of fac-Ir(ppy)(3) as a photocatalyst at room temperature. The reaction-proceeded in a chemo-and regioselective manner with high functional group tolerance under mild conditions alloWing the preparation of a wide variety of polycyclic (hetero)arornatic compounds, including phenanthrenes, in moderate to high yields. This procedure is amenable to gram-scale synthesis of 9-phenyliphenanthrene.