Moieties photo-Fries rearrangement

Neighboring groups at the ortho position of the aniline moiety can bring about side reactions that would compete with the photo-Fries rearrangement [100,101], (Some examples are shown in Scheme 39.)... 

If the acyl moiety bears the appropriate functional gronps, photo-Fries rearrangement may be followed by reaction between the phenolic hydroxyl and the reactive... 

Irradiation (313 nm) of films of polymers such as 1 leads to UV-Vis, IR, and solid-state 13C nmr changes attributed to a combination of 2 + 2 photocycloaddition and photo-Fries rearrangement [21], the latter presumably leading to cinna-moylphenol moieties, 2, in the irradiated polymer. Films irradiated at 313 nm in... 

The effects that initiator derived residues and functional groups have on polymer properties is an area that needs further study. For example, as discussed above, benzoyl peroxide leads to the formation of benzoyloxyphenyl groups in PS. It is known that the polymerization of p-benzoyloxystyrene [155] and its copolymerization with styrene [156] leads to the formation of photo-reactive polymers. Upon irradiation these polymers undergo a facile photo-Fries Rearrangement resulting in the conversion of the benzoyloxyphenyl groups to hydroxybenzophenone moieties [157]. Other side reactions also lead to the formation of phenolic groups and free benzoyloxy radicals [155]. 

The structure of XIV is difficult to elucidate but may be formed by the combination of the loss of the -COCHg moiety from and Photo-Fries rearrangement of III to yield most probably a semi-qulnone type of structure. If this is the case, then it appears that Photo-Fries rearrangements compete with photodegradation in these processes. Allen, et al. (15.16) have attributed the yellowing of BAE films under UV light to the formation of quinone structures, as shown below (XV), by photo-sensitized oxidation of the blsphenol A unit. 

Salicylate-type additives are largely imsuitable for use in aromatic polyesters, but some UV-stabilising ability has been shown by polyesters which contain moieties capable of transformation in the same way as the salicylates the so-called Photo-Fries rearrangement [20-22]. More recently, re-arrangeable polymers such as poly(phenyl acrylate) and poly(p-methylphenyl acrylate) have been proposed... 

Fluorenone based polyesters such as poly(9,9-bis(4-hydroxyphenyl) lluorene isophthalate) (4.61), poly(9,9-biscresol fluorene isophthalate) and poly(9,9-bis(3,5-dimethyl-4-hydroxyphenyl)fluorene isophthalate) undergo, under UV irradiation, typical photo-Fries rearrangement, during which linear o-hydroxybenzophenone moieties can be formed [1346] ... 

Arenes of the type ArX-Y, where X may be O, S, or NR, frequently undergo facile photoinduced homolytic cleavage of the X-Y bond with the Y radical subsequently attacking the aromatic ring. The photo-Fries reaction is the most common process of this type and has been reported within the year for aromatic esters which form part of a ptolymer chain or are pendant groups on a polymer chain. In the former case, the rearrangement of fluorene-based polyacrylates [for example, (292)] was studied. Formation of the o-hydroxybenzophenone moiety in the product (293) was monitored by u.v. and... 

All experimental observations with respect to these reactions, including the dependence on neither orbital character nor spin multiplicity of the excited state (which is in striking contrast to a-cleavage of carbonyl compounds) and the influence of substituents of the aryl moiety on the reaction rate, could be rationalized by correlation diagrams that were obtained on the basis of semiempirical MO calculations [105]. /1-Cleavage of phenoxyketones as well as photo-Fries and photo-Claisen rearrangements were characterized to be no photodissociations. 

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