Remarkable Effect of Lithium Salts in Friedel–Crafts Acylation of 2-Methoxynaphthalene Catalyzed by Metal Triflates

In the presence of a catalytic amount of a metal triflate such as Sb(OTf)3 or Ga(OTf)3, 2-methoxynaphthalene reacted with acetic anhydride in nitromethane–lithium perchlorate to afford 2-acetyl-6-methoxynaphthalene, a well-known intermediate for the synthesis of naproxen, in a high yield.