Friedel-Crafts Acylation of Anisole with Phthalic Anhydride Catalyzed by Solid Superacid of Sulfated Zirconia

Abstract

Friedel-Crafts acylation of anisole with phthalic anhydride was performed over several types of sulfated zirconia catalysts prepared from zirconia gel, JRC-ZRO-2, JRO-ZRO-3, JRC-ZRO-4, and JRO-ZRO-5, which are reference catalysts supplied by the Reference Catalyst Committee of the Catalysis Society of Japan, by equilibrium adsorption method and the kneading method. The only product was the diacylated product C6H4[CO(C6H4OCH3)]2; no monoacylated product, C6H4[CO(C6H4OCH3)]COOH, was observed. However, a large amount of monoacylated product was obtained when the acylation was catalyzed by the dissolved AlCl3. Phthalic acid monoethyl ester was produced by posttreatment of the catalyst with ethanol. Reaction time and temperature had little effect on the yield of ethyl ester. The diacylated product is probably formed by the addition of two anisoles to one carbonyl group in phthalic anhydride with subsequent rearrangement of the anisole group to the carbon of the other carbonyl group, because the other carbonyl group on phthalic anhydride is likely to be activated on the surface of the superacid. Observations with various solid superacid catalysts indicated the superacid sites on the surface are required for the formation of diacylated product.