Stereoselective Synthesis of Tetrahydroquinolines via Asymmetric Domino Reaction Catalyzed by a Recyclable Ionic‐Liquid‐Supported Bifunctional Tertiary Amine

The most recyclable ionic liquid‐supported bifunctional tertiary amine–squaramide organocatalyst for the asymmetric domino reaction has been found. Over this catalyst, ortho‐aminochalcones protected with Tosyl or Nosyl groups underwent the aza‐Michael/Michael domino reaction with nitroolefins to afford corresponding 2,3,4‐trisubstituted tetrahydroquinolines as single diastereomers in nearly quantitative yield with up to 99 % ee. The catalyst was readily separated from the reaction mixture via a simple centrifugation/decantation workup and 19 times reused in the catalytic reaction without noticeable conversion or enantioselectivity reduction. The N‐nosylated products proved their synthetic value for pharmacology given their facile conversion to fused pirrolidino‐tetrahydroquinolines of high diastreomeric and enantiomeric purity via successive deprotection and reductive amination.