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

Abstract

Abstract 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 2′-, 3′-, and 4′-methylacetophenones in the distribution of 9–10% 2′-, 1–2% 3′- and 89–90% 4′-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 4′-methoxyacetophenone for the acetylation of anisole with acetic anhydride.