Catalytic Atroposelective Aza-Friedel–Crafts Reactions of 2-Arylindoles with Pyrazolinone Ketimines: Simultaneous Construction of Axial and Central Chirality

A CPA-catalyzed atroposelective aza-Friedel–Crafts addition of 2-arylindoles to pyrazolinone ketimines is reported, delivering two separable diastereomeric axially chiral 2-arylindoles bearing a central chirality in high yields with excellent enantioselectivities. Single-crystal X-ray diffraction analysis confirmed identical axial absolute configurations in both diastereomers, proving the axial chirality formed via a dynamic kinetic resolution (DKR) process. Switching the catalyst enantiomer provides all four stereoisomers with high enantioselectivities.