Diastereo- and Enantioselective Tandem Michael Addition and Lactonization Catalyzed by Chiral Quaternary Ammonium Phenoxide: Stereoselective Synthesis of the Two Enantiomers by Using a Single Chiral Source

Diastereo- and enantio-selective synthesis of 3,4-dihydropyran-2-ones from various silyl enolates and α,β-unsaturated ketones were successfully carried out by using cinchonidine-derived quaternary ammonium phenoxide. In this reaction, a synthesis of the two enantiomers was achieved by an appropriate choice of a substituent on the bridgehead nitrogen of cinchonidine.