Synthesis of Enantioenriched Indolines by a Conjugate Addition/Asymmetric Protonation/Aza‐Prins Cascade Reaction

Abstract

Abstract A conjugate addition/asymmetric protonation/aza‐Prins cascade reaction has been developed for the enantioselective synthesis of fused polycyclic indolines. A catalyst system generated from ZrCl 4 and 3,3′‐dibromo‐BINOL enables the synthesis of a range of polycyclic indolines in good yields and with high enantioselectivity. A key finding is the use of TMSCl and 2,6‐dibromophenol as a stoichiometric source of HCl to facilitate catalyst turnover. This transformation is the first in which a ZrCl 4 ⋅BINOL complex serves as a chiral Lewis‐acid‐assisted Brønsted acid.