Why has Cerium (III) Triflate been Forgotten Among the Catalysts for the Friedel-Crafts Acylation?

Cerium is the less rare “rare earth”; its salts are commercially available and inexpensive. However, screening of lanthanide triflates as Lewis acid catalysts in the Friedel-Crafts acylation of aromatics skipped cerium triflate. Now, catalytic Friedel-Crafts acylations of activated benzenes are performed by using cerium (III) triflate as catalyst. For less activated arenes, addition of lithium perchlorate as co-catalyst is required. In all cases aromatic ketones are obtained in very good yields.