N‐Heterocyclic Carbene‐Catalyzed Kinetic Resolution of 3‐Nitro‐1,2‐Dihydroquinolines: Asymmetric Synthesis of All C2‐, C3‐ and C4‐Functionalized Tetrahydroquinolines

Abstract

AbstractAn efficient N‐heterocyclic carbene (NHC)‐catalyzed kinetic resolution of 2‐substituted 3‐nitro‐1,2‐dihydroquinolines (DHQs) allowing the synthesis of densely functionalized enantioenriched tetrahydroquinolines through the resolution at remote stereocenter is described. The Re‐face addition of α,β‐unsaturated azolium homoenolate intermediate generated in situ from enal with the more kinetically favored (S)‐enantiomer of the racemic 2‐substituted 3‐nitro‐1,2‐dihydroquinolines (rac‐1), affording the enantiopure tetrahydroquinolines (up to >99 : 1 dr, >99 : 1 er) and the opposite (R)‐enantiomer of DHQ (ent‐1) was recovered (up to >99 : 1 er).