Heteropoly acid Fries rearrangement

The use of HPAs and multicomponenf polyoxometalates as catalysts in liquid-phase reactions was reviewed by Kozhevnikov. Moreover, an interesting minireview was published concerning the Friedel-Crafts acylation of arenes and the Fries rearrangement catalyzed by HPA-based solid acids. The results show that HPA-based solid acids, including bulk and supported heteropoly acids as well as heteropoly acid salts, are efficient and environmentally friendly catalysis for all reacfions analyzed. 

Kozhevnikova, E. R, Quartararo, J., and Kozhevnikov, I. V. 2003. Fries rearrangement of aryl esters catalysed by heteropoly acid. Appl. Catal. A Gen. 245 69-78. 

Friedel-Crafts acylation and Fries rearrangement catalysed by heteropoly acids... 

A continuous gas-phase catalytic acetylation of phenol with acetic anhydride to phenyl acetate followed by simultaneous Fries rearrangement to yield ortho- and para-hydroxyacetophenones over a silica-supported heteropoly acid has been described. A complete conversion of phenol to phenyl acetate is achieved at 140°C. Upon increasing the temperature to 200°C, the phenyl acetate formed rearranges into hydroxyacetophenones with 10% yield and 90% selectivity to the para isomer. 

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