One-Pot Sequential Organocatalytic Michael-Tishchenko-Lactonization Reactions. Synthesis of Enantioenriched 4,5,6-Trisubstituted δ-Lactones

Enantioenriched trisubstituted lactones were obtained in good yields and moderate to very good enantioselectivities in one-pot process, which implies a sequential organocatalyzed Michael addition of ketones to enals, followed by catalytic intramolecular diastereoselective Tishchenko reaction and lactonization. The final lactones were obtained as single diastereoisomers, demonstrating that the mixture of the anti and syn diastereomers epimerized to the syn hydroxy ester during the oxido-reduction step.