Highly Enantioselective Reductions of 2H-Azirines

Herein, we present the first highly enantioselective reduction of mono- and tri- substituted 2H-azirines mediated by a chiral copper-hydride complex. The reaction tolerates both alkylated and arylated 2H-azirines to afford free N-H aziridines in excellent yield (up to 96%) and enantioselectivity (up to 96% ee). A key finding was the stark difference in copper complex structure necessary for the enantioselective reduction of mono- versus tri- substituted 2H-azirines. Finally, we demonstrate the synthetic value of this reduction for the preparation of bioactive molecules