Organocatalytic approach to 3,5,6-trisubstituted and 4,6-disubstituted tetrahydropyran-2-ones

The diarylprolinol ether-catalyzed Michael addition and subsequent cyclization of ethyl 3-methyl-2-oxobut-3-enoate with aldehydes, and γ-substituted β,γ-unsaturated-α-ketoesters with acetaldehyde, afforded the corresponding lactals, which were subjected to oxidation and stereocontrolled hydrogenation to provide 3,5,6-trisubstituted and 4,6-disubstituted tetrahydropyran-2-ones with excellent enantioselectivities.