Stereoselective and Regioselective Intramolecular Friedel–Crafts Reaction of Aziridinium Ions for Synthesis of 4‑Substituted Tetrahydroisoquinolines

Optically active 4-substituted tetrahydroisoquinolines were synthesized via intramolecular Friedel–Crafts (FC) reactions of aziridinium ions in a highly regio- and stereoselective manner. Control experiments suggest the formation and ring-opening of aziridinium ions as the key intermediates in the Lewis acid catalyzed FC reactions.