HAFNIUM(IV) TRIFLUOROMETHANESULFONATE, AN EFFICIENT CATALYST FOR THE FRIEDEL-CRAFTS ACYLATION AND ALKYLATION REACTIONS

Hafnium(IV) trifluoromethanesulfonate (hafnium(IV) triflate, Hf(OTf)(4)) was synthesized from hafnium tetrachloride and trifluoromethanesulfonic acid. The triflate thus prepared was found to be effective in the catalytic Friedel-Crafts acylation reactions of various substituted benzenes with acid anhydrides in lithium perchlorate-nitromethane (LiClO4-MeNO(2)). Lithium perchlorate-nitromethane is an excellent solvent system, and the catalytic activity of the Lewis acid was much improved in this medium. The product was obtained in up to 250000% molar amounts based on the catalyst. Hafnium(IV) triflate was also found to be quite effective in the catalytic Friedel-Crafts alkylation reactions of aromatic compounds with alkyl chlorides. The reactions proceeded smoothly in the presence of 5% molar amount of Hf(OTf)(4) and 50% molar amount of LiClO4 by using a slow addition procedure.