Niobium pentachloride–silver perchlorate as an efficient catalyst in the Friedel–Crafts acylation and Sakurai–Hosomi reaction of acetals

Friedel–Crafts acylation catalyzed by niobium pentachloride with silver salt is described. Aromatic compounds with Ac2O or Bz2O were smoothly converted into the corresponding ketones in good to excellent yields. This system was also applied to the Sakurai–Hosomi reaction using acetals. The reaction proceeded quite rapidly to give the desired products in excellent yields.