Phenolic esters, Fries rearrangement

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... 

FRIES Phenol Esier Rearrangement Rearrangement ol phenol esters to o or p ketophenols Lewis acid catalyzed... 

Phenolic esters (1) of aliphatic and aromatic carboxylic acids, when treated with a Lewis acid as catalyst, do undergo a rearrangement reaction to yield ortho- and para-acylphenols 2 and 4 respectively. This Fries rearrangement reaction is an important method for the synthesis of hydroxyaryl ketones. 

A variant of Method B is the cyclization of the phenolic 2-(chloroacetamido)benzophenones 9, produced by photo-Fries rearrangement (see Houben-Weyl, Vol. 7/2a, p 1148 ff) of the esters 8, with ammonia via the corresponding iodoacetyl compounds.195... 

A special case of aromatic acylation is the Fries rearrangement, which is the conversion of an ester of a phenol to an o-acyl phenol by a Lewis acid. 

Fries rearrangement.1 Rearrangement of phenyl esters with Lewis acids results in a mixture of ortho- and para-phenolic ketones. In contrast, reaction of an o-bromophenyl ester with sec-butyllithium results in exclusive formation of the orf/jo-phenolic ketone by an intramolecular acyl rearrangement.2... 

Fries rearrangement org chem The conversion of a phenolic ester into the corresponding 0- and p-hydroxyketone by treatment with catalysts of the type of aluminum chloride. frez re a ranj-mant)... 

Lewis acid-catalyzed rearrangement of phenol esters and lactams to 2- or 4-ketophenols. Also known as the Fries-Finck rearrangement. 

Fries, K. Finck, G. Ber. Dtsch. Chem. Ges. 1908, 41, 4271. Karl Theophil Fries (1875-1962) was born in Kiedrich near Wiesbaden on the Rhine. He earned his doctorate under Theodor Zincke. Although G. Finck co-discovered the rearrangement of phenolic esters, somehow his name has been forgotten by history. In all fairness, the Fries rearrangement should really be the Fries-Finck rearrangement. 

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. 

From the point of view of quantum yields calculation, photo-Fries rearrangement, including phenol and products formation, represents a photoreaction (expressed by Eq. 3) in which all products absorb intensively in the absorption region of the starting phenyl ester A. 

Fries rearrangement of phenolic esters to phenolic ketones (Problem 19.16). 

Fries rearrangement of aromatic formate esters suggests that phenols are the major products (.24) obtained in the reaction. As poly(p-hydroxystyrene) is remarkably clear in the deep UV, it is likely that poly(p-formyloxystyrene) will not suffer from the same problem of photostabilization upon exposure as was the case with poly (p-acetoxystyrene). This expectation was confirmed by our study of the photo-Fries reaction of p-cresyl formate no ortho rearranged product was isolated after reaction while p-cresol and a small amount of starting material were obtained. 

Although there is evidence that chromone syntheses which proceed by the cyclization of phenyl esters under Friedel-Crafts conditions may involve a Fries rearrangement and hence require the formation of one bond adjacent to the heteroatom, syntheses of chromones from phenols will be considered together in this section. The Simonis reaction (530R(7)l)... 

The synthesis of chromanones via a Fries rearrangement differs from the previous route only in that the acrylic ester of the phenol is formed prior to the addition of the Lewis acid catalyst (Scheme 223). 

A minor variant of this, method makes use of the reaction between an anisole and a 3-halogenopropanoyl chloride (14CB2585). These same 3-substituted acid chlorides react with phenols to give esters and a Fries rearrangement is now a prerequisite of chromanone formation (58JCS1190). 

The Fries rearrangement of phenol esters gives a mixture of 2- and 4-acylphenols. Similarly, enol esters undergo rearrangement to give the corresponding 1,2-di ketones. 

The Fries rearrangement of phenol esters gives a mixture of 2- and 4-acylphenols (56). The reaction is catalyzed by Lewis acids such as aluminum chloride or by Brmnsted acids like hydrogen fluoride. This reaction is used in the production of 4-hydroxyacetophenone [99-93-4], a raw material for... 

Fries rearrangement—that is, the transformation of phenolic esters to isomeric hydroxyphenyl ketones—is related to Friedel-Crafts acylations.392,393 Olah et al.394 have found a convenient way to perform the Fries rearrangement of a variety of substituted phenolic esters in the presence of Nafion-H in nitrobenzene as solvent [Eq. (5.153)]. A catalytic amount of Nafion-H is satisfactory, and the catalyst can be recycled. In contrast, Nafion-silica nanocomposites, in general, exhibit low activities in the Fries rearrangement of phenyl acetate to yield isomeric hydroxyacetophe-nones.239,395 In a recent study, BF3-H20 was found to be highly efficient under mild conditions (80°C, 1 h) to transform phenolic esters of aliphatic and aromatic carboxylic acids to ketones (71-99% yields).396 In most cases the para-hydroxyphenyl isomers are formed with high (up to 94%) selectivity. 

Phenolic ketones may be prepared by the Hoesch acylation reaction, which may be regarded as an extension of the Gattermann aldehyde synthesis (Section 6.10.1, p. 990). The procedure involves reaction of a nitrile with a phenol (or phenolic ether) in the presence of zinc chloride and hydrogen chloride best results are usually obtained with polyhydric phenols or their ethers, as for example in the preparation of phloroacetophenone (Expt 6.125). The formation of phenolic ketones by means of the Fries rearrangement of phenolic esters with aluminium chloride is discussed on p. 976. 

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)] ... 

Another example of the effect of confined medium is found during photo-Fries rearrangement of naphthyl esters in zeolites [103,104]. Upon photolysis in isotropic solution 1-naphthyl benzoate undergoes the photo-Fries rearrangement to yield both ortho (2-) and para (4-) phenolic ketones (Sch. 4). When this ester is included in NaY zeolite and irradiated the main product (96%) is the ortho isomer. This remarkable ortho-selectivity within zeolites has been rationalized on the basis of interactions of the reactant 1-naphthyl benzoate and intermediate radicals with the sodium ion. Due to restrictions imposed by the medium the benzoyl radical, once formed, is compelled to react only with the accessible ortho position. 

Photochemical processes of CD complexes,1 Differences in photochemical reactions conducted in solution and in CD complexes have been reviewed. For example, photo-Fries rearrangement of phenyl esters in solvents results in a mixture of o- and p-phenolic ketones via a radical reaction. Rearrangement of the same encapsulated ester results in exclusive rearrangement to the ortho-position (equa-... 

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