An efficient method for 3,4‐dihydroisoquinolinium ion formation, leading to a facile introduction of nucleophiles

The ketene silyl acetal derived from ethyl 2‐benzyltetrahydroisoquinoline‐1‐carboxylate undergoes a rapid oxidation reaction with N‐bromosuccinimide to form 3,4‐dihydroisoquinolinium ion, which reacts with Grignard reagents to give 1,1‐disubstituted tetrahydroisoquinolines in good yields.