Catalytic asymmetric cycloetherification via intramolecular oxy-Michael addition of enols

Carbonyl compounds employed as carbon nucleophiles have played a dominant role in synthetic organic chemistry; however, there is very limited use of these compounds as oxygen nucleophiles. In particular, there are only a few reports on the oxy-Michael addition of the enol forms of carbonyl nucleophiles. In this study, we present the asymmetric cycloetherification of enols, which are generated in situ from enone-bearing ketones, using chiral bifunctional organocatalysts bearing amino and squaramide groups. This transformation chemo-and enantioselectively afforded dihydropyran derivatives, which are the core structures of building blocks for synthesizing glycans.