Enantiomerically Enriched Aziridine‐2‐carboxylates via Copper‐Catalyzed Reductive Kinetic Resolution of 2H‐Azirines

We present the first reductive kinetic resolution of racemic 2H‐azirines to prepare optically enriched N‐H aziridine‐2‐carboxylates, which are bench stable and easily diversifiable building blocks, concomitantly with the corresponding enantiomerically enriched 2H‐azirines. The N‐H aziridines were obtained with excellent diastereoselectivity (>20:1) and high enantioselectivity (up to 94%). A Hammett study revealed a linear free energy relationship between the ΔΔG⧧ of the diastereomeric transition states and the σp‐ values. DFT calculations and non‐covalent interaction analysis suggested that non‐classical H–bonding interactions and edge‐to‐face aromatic interactions between the substrate and the ligand are responsible for the stereoselectivity and also for the substrate electronic effects observed in the Hammett study.