P-Hydroxyacetophenones

The ester and catalj st are usually employed in equimoleciilar amounts. With R =CjHs (phenyl propionate), the products are o- and p-propiophenol with R = CH3 (phenyl acetate), o- and p-hydroxyacetophenone are formed. The nature of the product is influenced by the structure of the ester, by the temperature, the solvent and the amount of aluminium chloride used generally, low reaction temperatures favour the formation of p-hydroxy ketones. It is usually possible to separate the two hydroxy ketones by fractional distillation under diminished pressure through an efficient fractionating column or by steam distillation the ortho compounds, being chelated, are more volatile in steam It may be mentioned that Clemmensen reduction (compare Section IV,6) of the hj droxy ketones affords an excellent route to the substituted phenols. 

In semiindustrial synthesis, to achieve better yields, it is possible to omit (A), by directly preparing the ester (B) by reaction of p-hydroxy acetophenone on ethyl 2-bromoacetate in the presence of potassium carbonate in butanone. The yield of ester is 90%, and elimination of excess of p-hydroxyacetophenone is effected by washing with sodium hydroxide. 

The phenol ArOH is always a side product, resulting from some ArO that leaks from the solvent cage and abstracts a hydrogen atom from a neighboring molecule. When the reaction was performed on phenyl acetate in the gas phase, where there are no solvent molecules to form a cage (but in the presence of isobutane as a source of abstractable hydrogens), phenol was the chief product and virtually no o- or p-hydroxyacetophenone was found." Other evidence" for the mechanism is that... 

In much the same vein, condensation of the difunctional p-hydroxyacetophenone 64 with diethyl... 

Senecio cannabifolius Lessing Huan Hun Cao (Groundsel) (whole plant) p-hydroxyacetophenone, arbutin.48 Treat heart disease, respiratory infection, sexually transmitted diseases. 

The p-acetoxystyrene monomer, precursor of polymer III, is prepared from p-hydroxyacetophenone using the procedure of Corson et al. (14) which involves acetylation of the phenolic group followed by catalytic hydrogenation of the ketone and dehydration of the resulting benzylic alcohol as shown in Scheme 3. 

Preparation of p-Acetoxystyrene This compound was prepared by a modification of the procedure of Corson et al. (14), using p-hydroxyacetophenone as a starting material. Fractional distillation of the crude material gave a 46% yield of p-acetoxystyrene with b.p. 69-72 °C/0.5 mm Hg (lit. 73-75°C/0.6 mm Hg14). 

Arnett and Bushick (2) have determined the pKA values for the conjugate acids of ferrocenyl ketones in aqueous sulfuric acid. They have found, for example, that acetylferrocene is over 2000 times more basic than acetophenone and 85 times more basic than p-hydroxyacetophenone. These data support the concept that metallocenyl groups are strongly electron-releasing compared to the phenyl group and that they possess extraordinary ability to delocalize adjacent positive charges. 

Fries rearrangement and phenol acetylation The Fries rearrangement is the acid catalysed transformation of aryl esters into hydroxyarylketones. Both this rearrangement and the two-step transformation (esterification, Fries rearrangement) in one-pot operation of phenols with carboxylic acid or anhydrides will be examined hereafter. Most studies in which acid zeolites were used as catalysts (Tables 3.6 and 3.7) deal with the synthesis of o- and p-hydroxyacetophenones (o- and p-HAP) either by the Fries rearrangement of phenyl acetate [Reaction (3.5)] ... 

Reaction scheme The Fries rearrangement of phenyl acetate (PA) was first mentioned as occurring over zeolites in the review paper published in 1968 by Venuto and Landis.[64] This rearrangement was afterwards investigated at 673 K over HFAU and HMFI zeolites.[65] The reaction was not selective the expected o-and p-hydroxyacetophenones (o- and p-HAP) were minor components and phenol the main component. With both zeolites, o-HAP was highly favoured over the para isomer. 

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