Liquid-phase FTIR study of the acylation capacity of supported phospho-tungstic Wells-Dawson heteropoly-acid

S.E. COLLINS, S.R. MATKOVIC, A.L. BONIVARDI, L.E. BRIAND

Rostock-Warnemünde, Alemania

Congreso; III International Operando Congress; 2009

Heropoly-anions [XyMxOm]n- are composed by a close-packed framework of metal-oxygen octahedrons, M-O (M = Mo6+, W6+, V5+) surrounding a central atom, X (Si4+, P5+, etc). Nowadays, many research efforts are devoted to investigate both Keggin [XM12O40]3- and Wells-Dawson-type [X2M18O62]6- anions due to their promising application as catalytic materials. The free acid form of the heteropoly-anions, i.e. Keggin H3XM12O40 and Wells-Dawson H8X2M18O62 type compounds, are solid super-acids since their acid strength is greater than 100% H2SO4. Therefore, many heteropolyacids are more active catalysts than conventional organic and inorganic acids in liquid-phase reaction. The insolubility of the heteropoly-acids in many liquid organic substances allows an easy separation and reutilization of these catalysts. Undoubtedly, the catalytic processes based on heteropoly-acids are an outstanding contribution in the development of environmental benign technologies. On line with this worldwide trend, our group explores the catalytic activity of fosfotungstic Wells-Dawson heteropoly-acid in the Friedel-Crafts acylation of p-isobutylbenzene with acetic anhydride towards p-isobutylacetophenone. This substance is an intermediate species in ibuprofen synthesis. Surprisingly, the preliminary results showed that p-isobutylbenzene was acylated towards 4-isobutylacetophenone and this substance was further condensed towards a dypnone like compound. Therefore, the present investigation was conducted in order to explore both the ability of the HPA to catalyze the Friedel-Crafts acylation and further Aldol condensation of the substituted acetophenone and further understand the deactivation of the heteropoly acid during the acylation.