Friedel-Crafts Acetylation, Propionylation, and Butyrylation of Toluene Catalyzed by Solid Superacids

The liquid-solid phase acetylation of toluene with acetic anhydride was carried out over solid superacids of sulfated metal oxides (SO4/MeOx) and supported metal oxides (Me1Ox/Me2Oy) selected from the results in the benzoylation of toluene with benzoic anhydride [K. Arata, H. Nakamura, and M. Shouji, Appl. Catal. A: General, 197, 213 (2000)]. The reaction was conducted by adding dropwise a mixture of 2 mmol of acetic anhydride and 2 mL of toluene onto 0.5 g of catalyst suspended in 13 mL of toluene with stirring at 110 C in the first period of 30 min, followed by stirring the mixture for 2 h. The yields of 2ʹ-, 3ʹ-, and 4ʹmethylacetophenones in the distribution of 9-10% 2ʹ-, 1-2% 3ʹ- and 89-90% 4ʹ-isomers were 24 and 13% for the sulfated metal oxides of SO4/ZrO2 and SO4/SnO2, those by Pt and Ru promoted sulfated zirconias (Pt-, Ru-SO4/ZrO2) being 21 and 28%, respectively. The supported metal oxides of Fe2O3/ZrO2 and WO3/ZrO2 gave yields of 18 and 15%, respectively. The propionylation and butyrylation of toluene with propionic and butyric anhydrides were performed over SO4/ZrO2, SO4/SnO2, Pt-SO4/ZrO2, and Ru-SO4/ZrO2; the yields of 7-9% o- and 91-93% p-isomers were 31, 26, 32, and 44% for propionylation and 46, 29, 44, and 55% for butyrylation, respectively. The SO4/ZrO2 catalyst gave a 100% yield of 4ʹ-methoxyacetophenone for the acetylation of anisole with acetic anhydride.