Asymmetric Aza Friedel–Crafts Reaction of 3,4-Dihydroisoquinolines with 1-Naphthols Catalyzed by Chiral Phosphoric Acids

An efficient chiral phosphoric acid-catalyzed asymmetric aza Friedel-Crafts reaction of 3,4-dihydroisoquinolines and 1-naphthols is described. The reaction provides a general method for the synthesis of diverse chiral tetrahydroisoquinoline with 1-naphthol substituents at the C1-position in excellent yields and enantioselectivities. Based on the conducted mechanistic experiments, a plausible catalytic mechanism was proposed. Moreover, the practicability of the reaction is successfully demonstrated by its application on a gram scale.