Hydrolytic Enantioselective Protonation of Cyclic Dienyl Esters and a β-Diketone with Chiral Phase-Transfer Catalysts

Hydrolytic enantioselective protonation of dienyl esters and a beta-diketone catalyzed by phase-transfer catalysts are described. The latter reaction is the first example of an enantio-convergent retro-Claisen condensation. Corresponding various optically active alpha,beta-unsaturated ketones having tertiary chiral centers adjacent to carbonyl groups were obtained in good to excellent yields and enantiomeric ratios (83-99%, up to 97.5:2.5 er).