Asymmetric Synthesis of Chiral Pyrrolidinones by a Formal Aza‐[3+2] Cycloaddition: An Organocatalytic One‐Pot Michael/Hemiacetalization Approach

An organocatalytic one‐pot synthesis of 3,4‐disubstituted chiral pyrrolidinones has been developed, featuring excellent diastereo‐ and enantioselectivity. The reaction sequence involves an initial asymmetric Michael reaction between an aldehyde and 3‐nitro‐ N ‐(phenylmethyl)‐2‐propenamide, catalyzed by diphenylprolinol silyl ether, followed by intramolecular hemiacetal formation and subsequent nucleophilic addition. This sequence constitutes a formal asymmetric catalytic aza‐[3+2] cycloaddition.