Visible‐Light‐Driven Synthesis of Phenanthridin‐6(5H)‐one and N‐Substituted Carbazole Derivatives through Intramolecular C‐H Arylation.

A visible‐light‐driven approach towards phenanthridin‐6(5H)‐one and carbazole rings synthesis under transition‐metal‐free conditions is here reported. Phenanthridinones and carbazoles are synthesized through an intramolecular arylation of the corresponding N‐(2‐halobenzyl)‐N‐methylanilines or N‐substituted‐N‐phenyl anilines using KOtBu as base in dimethyl sulfoxide (DMSO) at room temperature (rt), employing blue light emitting diodes (LEDs) as the light source. The reaction proceeds through photo‐ and base‐promoted homolytic aromatic substitution via photoinduced electron transfer mechanism and it exhibits good tolerance to different functional groups, resulting in good to very good yields (up to 86 %). [ABSTRACT FROM AUTHOR]