Chiral Bifunctional Squaramide‐Catalyzed Highly Enantioselective Michael Addition of Allomaltol to β,γ‐Unsaturated α‐Ketoesters

Abstract

Abstract A highly enantioselective Michael addition of allomaltol (5‐hydroxy‐2‐methyl‐4 H ‐pyran‐4‐one) to both aromatic and aliphatic β,γ‐unsaturated α‐ketoesters has been realized. Under the catalysis of a chiral bifunctional tertiary amine‐squaramide that bears a (1 R ,2 R )‐1,2‐diphenylethane‐1,2‐diamine scaffold, the reaction proceeded smoothly with high levels of enantioselectivity to give the desired products in acceptable yields with 86–>99 % enantiomeric excess. This methodology provided an efficient process for the enantioselective synthesis of optically active kojic acid derivatives.