Visible-Light-Induced Radical Cascade Cyclization: Synthesis of (20S)-Camptothecin, SN-38 and Irinotecan

(20S)-Camptothecin, irinotecan and SN-38 were successfully synthesized by a photocatalyzed radical cascade cyclization from an N-propargyl iodopyridinone and an arylisonitrile under visible light with a ruthenium catalyst. This synthetic method provided a useful entry into composing camptothecin family of antitumor agents in good yields under mild reaction conditions without the use of heavy metal reagents.