Diastereo- and Enantioselective Tandem Michael Addition and Lactonization between Silyl Enolates and α,β-Unsaturated Ketones Catalyzed by a Chiral Quaternary Ammonium Phenoxide

Diastereo- and enantioselective tandem Michael addition and lactonization between various silyl enolates derived from phenyl carboxylates and α,β-unsaturated ketones were successfully carried out by using an efficient organic catalyst, a cinchonidine-derived chiral quaternary ammonium phenoxide. In this asymmetric tandem reaction, the corresponding trans-3,4-dihydropyran-2-ones were obtained in high yields with almost complete diastereoselectivities and good to excellent enantioselectivities.