Thermal vs. Visible‐Light Photoredox‐Catalyzed Cascade Radical Cyclization Involving SO2 Fixation to Access 6‐Alkylsulfonylmethyl Phenanthridines

Abstract Convenient access to 6‐alkylsulfonylmethyl phenanthridines has been demonstrated both under non‐catalytic thermal and visible‐light photoredox‐catalyzed conditions. A cascade of radical cyclization is triggered by the exposure of biphenyl vinyl azides to the in‐situ generated alkyl sulfonyl radicals from 4‐substituted Hanztsch esters in the presence of an SO 2 surrogate. Transition metal‐free, mild reaction conditions, and broad substrate scope constitute some of the highlights of the approach. Also, the synthetic utility of the accessed 6‐alkylsulfonylmethyl phenanthridines has been demonstrated.