Organocatalyzed Asymmetric Michael Addition of 1-Acetylindolin-3-ones to β,γ-Unsaturated α-Ketoesters: An Access to Chiral Indolin-3-ones with Two Adjacent Tertiary Stereogenic Centers.

Asymmetric Michael addition of 1-acetylindolin-3-ones to β,γ-unsaturated α-ketoesters was investigated for the synthesis of chiral indolin-3-ones with two adjacent tertiary stereogenic centers. Under the catalysis of a chiral bifunctional squaramide derived from l-tert-leucine, a wide range of 1-acetylindolin-3-ones and β,γ-unsaturated α-ketoesters were well-tolerated in this transformation to provide the corresponding novel densely functionalized chiral indolin-3-one derivatives in high yield with excellent diastereo- and enantioselectivity under mild reaction conditions.