Cobalt-Catalyzed Asymmetric Dearomative [3+2] Annulation of Quinolines, Isoquinolines, and Pyridines

A highly enantioselective dearomative [3 + 2] annulation of quinolines, isoquinolines, and pyridines with donor-acceptor aminocyclopropanes was achieved. With C-1-symmetric imidazoline-pyrroloimidazolone pyridine as the tridentate ligand and Co(OTf)(2) as the Lewis acid, diverse chiral indolizidine and benzo-fused indolizidine derivatives were obtained in good yields (up to 98% yield), excellent diastereoselectivities (>20:1 dr), and excellent enantioselectivities (up to 98% ee). Mechanistic experiments and density functional theory (DFT) calculations revealed that the tridentate nitrogen ligand acted as a bifunctional chiral ligand. The ligand not only coordinated with the Co(II) salt to activate aminocyclopropane via bidentate coordination, but also formed a H-bond with the oxygen atom in the succinimide moiety to fix the orientation of aminocyclopropane, thus facilitating the nucleophilic attack of N-heteroaromatics. Additionally, the high enantioselectivity of the reaction was governed by steric factors.