Stereoselective Mannich Reaction of
<i>α</i>
‐Acetoxy‐
<i>β</i>
‐keto Esters with Isatin Imine: An Efficient Access to Vicinal Tetra‐Substituted Stereocenters
Synthesis of optically active 3-substituted-3-aminooxindoles containing vicinal quaternary stereogenic centers was achieved using a quinine thiourea organocatalyst. α-Acetoxy-β-keto esters have been introduced as nucleophiles to undergo Mannichreaction with isatinimines for asymmetric organocatalysis.
An organocatalytic asymmetric aza-Henry reaction of ketimines derived from isatins with nitroalkanes has been achieved using Cinchona alkaloid organocatalysts. This method works efficiently with several ketimines to produce a good (up to 82%) yield of the corresponding 3-substituted 3-amino-2-oxindoles with a good (up to 89%) enantiomeric excess.