(Salen)Mn(III)-Catalyzed Enantioselective Intramolecular Haloamination of Alkenes through Chiral Aziridinium Ion Ring-Opening Sequence

Asymmetric catalysis with a chiral (Salen)Mn(III) complex is applied successfully to highly enantioselective intramolecular haloamination reactions of alkenes through a chiral aziridinium ion ring-opening sequence. Computational and experimental studies suggested that the C5-C6 bond polarization has a major effect on the regioselectivity of the chiral aziridines ring intermediate, and steric hindrance of groups at C5 or C6 plays a minor role. Various amino-alkenes can cyclize under the reaction conditions to obtain 2-brominated/chlorinated pyrrolidine and indoline derivatives with excellent yield and enantioselectivity.