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

摘要

The reaction of o,o'-dialkyl-substituted aryl isonitriles with N-proparayl-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. [References: 27]