Acetic anhydride veratrole reaction

Gallium(in)- and iron(lll)-promoted SZ can be supported on mesoporous materials such as MCM-41 silica [86]. The catalysts, named GaSZ/MCM-41 and FeSZ/MCM-41, respectively, are prepared by incipient wetness impregnation using zirconium(lV) sulfate as the precursor in combination with gallium(ni) nitrate or ferric nitrate and calcined at 700°C for 3 h. These catalysts were studied in the acylation of veratrole with acetic anhydride the reaction gives only 3,4-dimethoxyacetophenone. The most active catalyst is GaSZ/MCM-41 (78% yield, 100% selectivity), followed by SZ/MCM-41 alone (68% yield, 100% selectivity) in the reaction carried out at 80°C for 3h (Scheme 3.14). 

The veratrole was introduced into a stainless-steel standard reactor with the HY zeolite and the reaction mixture was then heated to 90 °C and acetic anhydride is added over 4 h. The molar ratio veratrole/acetic anhydride was 1.2. When the reaction was over, the reactor was cooled to 60 °C and the reaction mixture filtered under 2 bar. With a 5-cm cake, the filtration rate was acceptable. After distillation, the acetover-atrole was isolated in 85% yield. The use of a spray-dried form of HY zeolite, a catalyst consisting of 60 wt% silica and 40 wt% H Y zeolite, was another means of increasing the filtration rate. In this last case, the catalyst can easily be recycled. 

To confirm the inhibition effect of the adsorbed diketone on the acylation of veratrole by acetic anhydride over HBFA and HY zeolites, this product was added to reaction mixtures with both zeolites. Its presence caused a significant decrease in the yield in acylated products. For example, the addition of 3% (by weight with respect to veratrole) of diketone caused a loss in yield of more than 50% in both cases. 

For the acylation of anisole by acetic anhydride over HBFA and HY, the reasons for the deactivation accord with those already reported for the reaction with veratrole. Unfortunately, di- or triketones were not extractible and, also, deactivation of the... 

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