Aryl esters Fries rearrangement

Anhydrides—Continued reduction to alcohols, 155 reduction to lactones, 535 Arenes, see Hydrocarbons, aromatic Amdt-Eistert reaction, 433, 487, 573 Aryl esters. Fries rearrangement, 344 hydrolysis, 169 preparation, 169 Aryl halides, see Halides Atyloxy acids, preparation, by aceto-acetic ester synthesis, 430 by malonic ester synthesis, 429 from atyloxy alcohols, 419 from atyloxy cyanides, 414 preparations listed in table 48, 460 Aryloxy acyl halides, preparation, 547 preparations listed in table 61, 553 Aryloxy esters, preparations listed in table 55, 516... 

The preference for O acylation of phenols arises because these reactions are kmetically controlled O acylation is faster than C acylation The C acyl isomers are more stable how ever and it is known that aluminum chloride is a very effective catalyst for the conversion of aryl esters to aryl ketones This isomerization is called the Fries rearrangement... 

Fries rearrangement (Section 24 9) Aluminum chlonde promoted rearrangement of an aryl ester to a ring acylated denvative of phenol... 

The photo-Fries rearrangement of aryl hydrogen (or methyl) succinates 267 leads to 4-(2-hydroxyaryl)-4-oxobutanoic acids (or methyl esters 268), which are readily cyclized to 5-(2-acetoxyaryl)-2(3//)-furanones (269) (Scheme 68). [189-191] Photolysis of 269 [191] or the analogous open-chain enol acetates [192,193] leads to chromones. 

Photo-Fries rearrangement of aryl esters or its participation in addition to other photochemical reactions was reported in numerous papers concerning low-molecular78 or macromolecular79,63 compounds. 

Ortho- and para-rearrangement and phenol formation on uv-irradiation of aryl esters are accompanied in several cases by decarboxylation,37,60,62,64,80,81 represented for 3,5-di-t-butylphenyl benzoate by the equation 118 -> 119-122. It was shown that this reaction cannot be sensitized,64 but the dramatic differences in product distribution could be observed by changing of the solvent.60,84 The results in Table VI indicate that in polar solvents the decarboxylation process is minimized while the formation of the photo-Fries rearrangement 119 is enhanced. The reverse appears to be true when nonpolar ethereal solvents are used. A considerable amount of biaryls are formed, and hence this reaction may prove useful for the preparation of biaryls and alkylary Is. 

Photolysis of phenyl 2-thenoate leads to a 3 2 mixture of ortho and para Fries rearrangement products (Scheme 109) (74H(2)423). The photolytic rearrangement of a thiolester to a thiopyrone has been investigated with thiophenecarbothioic acid S-aryl esters as substrates (79LA2043). In the case of the 2-carbothioic acid esters, a 3-bromo substituent is necessary for this rearrangement. On the other hand, such a substituent is not necessary for the 3-carbothioic acid derivatives. In both cases, aldehydes may also be formed, sometimes as the main products (Scheme 110). 

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)] ... 

The Friedel-Crafts acylation of phenols proceeds via initial esterification followed by Fries rearrangement of the resulting aryl ester to afford the hydroxyaryl... 

Advantageously, catalytic amounts of rare earth metal triflates are used instead of stoichiometric amounts of aluminum trichloride in catalytic Fries rearrangements of carboxylic acid aryl esters furnishing keto building blocks, e.g. 10... 

In each of the aryl esters discussed above, the acyl radical formed upon lysis of the excited singlet state of the ester loses CO very slowly at the temperatures of the irradiations. At 296K, the rates of loss of CO by acetyl and propanoyl radicals in the gas phase are 4.0 and 2.1 x 10 s respectively." As aresult, no products from decarbonylation and rearrangement are expected" (or have been found) when either of the NA or NM isomers is irradiated in liquid solvents or bulk polymers, and kinetic information from photoproducts alone is limited to relative rates of radical pair processes (Scheme 13.3). For example, if no Fries products from 1-NA or 1-NM emanate from reencounter of radicals that have escaped from their initial cages, [2-AN]/[4-AN]/[l-NOL] = /c2a/ 4a/ nol-... 

Olah, G. A., Arvanaghi, M., Krishnamurthy, V. V. Heterogeneous catalysis by solid superacids. 17. Polymeric perfluorinated resin sulfonic acid (Nafion-H) catalyzed Fries rearrangement of aryl esters. J. Org. Chem. 1983,48, 3359-3360. 

The Fries rearrangement used for the preparation of aryl ketones from phenolic esters is now one of the most significant reactions in the synthetic chemistry of aromatic compounds, both in the classical version (equation 99) and in the newest modifications (see Section IV.D.3). 

Arenes of the type Ar-X-Y in vbich the X-Y bond is readily cleaved homolytically undergo facile lateral-nuclear rearrangement. The archetypal example of this process is the photo-Fries rearrangement which occurs with aryl esters and anilides and several reports of these reactions have appeared within the review period. Several... 

The Fries rearrangement is the acid-catalyzed transformation of aryl esters into hydroxy ary Iketones [1] and often plays an important role in the production of hydro-xyarylketones by acylation of phenols with carboxylic acids, anhydrides, or acyl chlorides. 

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. 

Fries rearrangement, review. Martin2 has reviewed the rearrangement of aryl esters to o- and p-hydroxyaryl ketones, usually effected with AICI3. The rearrangement can occur at room temperatures in polar solvents (nitroalkanes). Photo-induced rearrangement usually provides the same products as obtained by Lewis acid induced rearrangement. The review lists 281 references to literature mainly from 1964 to 1990. 

The Fries rearrangement is the name for the very widespread rearrangement of aryl esters to hydroxy aryl ketones,75 thus ... 

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