Organocatalytic Asymmetric Conjugate Addition of 2‐Oxindole‐3‐Carboxylate Esters to 2‐Phthalimido Acrylates: Efficient Synthesis of C γ ‐tetrasubstituted α‐Amino Acid Derivatives

An organocatalytic asymmetric conjugate addition of 2‐oxindole‐3‐carboxylate esters to 2‐phthalimidoacrylates catalyzed by a quinine‐derived thiourea is described. The reaction provides efficient access to a variety of quaternary oxindole based C γ ‐tetrasubstituted α‐amino acid derivatives in good to excellent yields (up to 96 %) with moderate to good enantioselectivity (up to 90 % ee ). The opposite enantiomers of the products can also be obtained with comparable yields and stereoselectivity by simply using a quinidine‐derived thiourea catalyst.