Cascade 4+1 Radical Annulations of 2,6-Disubstituted Phenyl Isonitriles with N-Propargyl-6-Iodopyridones: Scope, Mechanism and Regioselective Synthesis of 7,9-Disubstituted Camptothecin Analogs

Abstract

The reaction of o,o′-dialkyl-substituted aryl isonitriles with N-propargyl-6-iodopyridones provides 11H-indolizino[1,2-b]quinolin-9-ones with significant regioselectivity in favor of the more crowded product. The usefulness of the method is illustrated with a regioselective synthesis of (20S)-7-trimethylsilyl-9-isopropyl camptothecin.

cascade radical annulation - isonitrile - camptothecin - mappicine - quinoline

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Supporting Information Available: A print or pdf file of the characterization data for the compounds in this paper can be obtained on request from DPC.