K2S2O8-Initiated Cascade Cyclization of 2-Alkynylnitriles with Sodium Sulfinates: Access to Fused Cyclopenta[gh]phenanthridines

A convenient K2S2O8-initiated radical cascade cyclization for the construction of 4-sulfonated cyclopenta[gh]-phenanthridines from 2-alkynylnitriles and sodium sulfinates has been explored under metal-free conditions. This protocol features mild conditions, good functional group tolerance and broad substrate scope. A variety of potentially bioactive 4-sulfonated cyclopenta[gh]phenanthridines were facilely synthesized via direct annulation.