Photo-Fries-type rearrangement

Attempts to isomerize the 2-methylene-3/f- azepine (45 R1 = H, R2 = PhCO) to the AT-benzoyl- 1H-azepine under acid- or base-catalyzed conditions failed. Irradiation of the 3//-azepine resulted only in a photo-Fries type rearrangement of the benzoyl group to give aminoketone (45 R1 = PhCO, R2 = H) (74JOC3076). 

Iwasaki, S. (1976) Photochemistry of imidazolides. I. The photo-Fries-type rearrangement of N-substituted imidazoles. Helvetica Chimica Acta, 59 (8), 2738-2752. 

Other N-substituted indoles have also been reported to undergo a photo-Fries type rearrangement of the substituent to other positions in the indole nucleus. The substituents that have been shown to migrate in this fashion include tosyl [34], alkoxy [34], aminocarbonylmethyl [38], and methoxycarbonylmethyl [38] (Scheme 6). 

Photo-Fries rearrangement-. Photo-Fries rearrangement involve migra-fSi of a group across a double bond (1,3 migration) in structures of the Plowing type ... 

Ramamurthy and coworkers studied the photo-Fries rearrangement of phenyl acetate and phenyl benzoate and photo-Claisen rearrangement of allyl phenyl ether (Fig. 34) included in two types of zeolite (faujasites X and Y and pen-tasils ZSM-5 andZSM-11) [192], The photolysis was performed with the zeolite slurry in either hexane or iso-octane. One of the most remarkable observations is that the product distribution is altered within zeolites from that in isotropic solvent. Furthermore, while in solution, nearly a 1 1 mixture of ortho and para isomers 40 and 41 (Fig. 34) was obtained, within zeolites one is able to direct the photoreaction selectively toward either the ortho or the para products by conducting the reaction either within faujasites or pentasils, respectively (Fig. 34). 

Irradiation of lower molecular weight samples in the fluid N phase at 313 or 366 nm led to an unusual result [21]. In the first few seconds of irradiation the perturbed spectrum of the N phase exhibited hyperchromism (an increase in absorbance) and its shape became similar to that of the spectrum of the isotropic melt. This effect is also observed upon triplet sensitization which, like 366-nm irradiation, suppresses photo-Fries rearrangement [28]. It has not yet been proved that this effect is accompanied by a phase change from N to I induced by photoproducts essentially acting as impurities in the mesophase. The effect could be at the microscopic level where formation of a cyclobutane dimer or other photoproduct could interrupt H-type aggregated chromophore stacks, or confor-... 

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... 

Polyurethanes.—The photo-oxidation of polyurethane elastomers based on aromatic isocyanate units has been studied and found to involve two principal reactions. The first is a photo-Fries rearrangement with light wavelengths <330 nm and the second is a photoinduced hydroperoxidation.Several hydroperoxide structures were identified [e.g., (5)—(8)] and their importance examined." " Type (5) hydroperoxides are the most photolabile and are... 

Tsutsumi, K., Matsui, K., Shizuka, H. Substituent effects on the photo-Fries rearrangement of aryloxy-s-triazines Norrish type I dissociation. 

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 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... 

Photolytic decomposition of polycarbonate films was shown to produce products that are also consistent with the photo-Fries reaction. These are salicylic acid and bisphenol type species [580]. This is in agreement with earlier studies that showed that a variety of processes, including rearrangements (photo-Fries) and photo-oxidation, can occur when bisphenol A-based polycarbonate is photolyzed [581, 582]. 

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