Rearrangements photo-Fries rearrangement

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 ... 

Beckmann rearrangement, 4, 292 pyrolysis, 4, 202 synthesis, 4, 223 Wittig reaction, 4, 294 Wolff-Kishner reduction, 4, 291 Indole, 1-acyl-2,3-disubstituted photoisomerization, 4, 204 photo-Fries rearrangement, 4, 204 photoisomerization, 4, 42 synthesis, 4, 82 Indole, 2-acyl acidity, 4, 297 synthesis, 4, 337, 360 Indole, 3-acyl-acidity, 4, 297 cleavage, 4, 289 reduction, 4, 289 synthesis, 4, 360 Indole, 7-acyl-synthesis, 4, 246... 

A photochemical variant, the so-called photo-Fries rearrangement, proceeds via intermediate formation of radical species. Upon irradiation the phenyl ester molecules (1) are promoted into an excited state 11. By homolytic bond cleavage the radical-pair 12 is formed that reacts to the semiquinone 13, which in turn tautomerizes to the p-acylphenol 3. The corresponding ort/zo-derivative is formed in an analogous way ... 

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... 

Figure 1. Photo-Fries rearrangement and other photoinduced degradations of...

Chain cleavage with subsequent formation of phenolic products, rather than the photo-Fries rearrangement to form salicylates and dihydroxybenxophenones, has been identified as the major initial degradation pathway of PC exposed to natural weathering conditions. 

The radiation induced side-chain modification of polymers containing pendant phenyl ester groups has been the object of several studies as some undergo a photo-Fries rearrangement (JJ while others such as... 

Photo-Fries Rearrangement of Styrylpyridine Based Ester and Carbonate-UV-Spectroscopic Studies... 

The present work deals with the photo-Fries rearrangement (PFR) and covers the literature appearing since the first report of Anderson and Reese to the beginning of 2002. It includes both the mechanistic aspects and the synthetic applications of this reaction. The topic of the PFR in polymers is also treated. In addition, a section has been devoted to the photo-Fries rearrangement in organized media, a field of recent interest. 

The modern techniques for detection of short-lived species provided the necessary evidences to establish the three main mechanistic features of the photo-Fries rearrangement ... 

As can be seen, the pathway from the cyclohexadienone to the ortho-rearranged phenol does not imply a jump over an energy barrier (34 kcal/mol), but a tunneling from the vibrational energy levels located at E(vo) = 0 kcal/mol and E(vi) = 3.9 kcal/mol (4.4 kcal/mol for the deuterated compound). Analogous results have been reported for the photo-Fries rearrangement of 2,4-dimethoxy-6-( ara-tolyloxy)-v-triazine (28) to give 2,4-dimethoxy-6-(2-hydroxy-5-meth-ylphenyl)-v-triazine (29) (Scheme 11) [43]. 

---