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-<i>tert</i>-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
