Photo-Fries carbonates

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

For the initial phase of the photo-Fries rearrangement, IA can be determined approximately by subtracting the absorption due to the strongest absorbing product of the reaction mixture, provided its concentration and molar extinction coefficient are known. By means of this initial rate approach Humphrey8 determined the quantum yields of the photorearrangement of 13 (913-14 = 0.14), of 14 (914-.18 = 0.056), and of poly-2,2-propanebis(4-phenyl carbonate) ([Pg.138]

Andrew, D. Des Islet, B. T. Margaritis, A. Weedon, A. C. Photo-Fries Rearrangement of Naphthyl Acetate in Supercritical Carbon Dioxide Chemical Evidence for Solvent-Solute Clustering. J. Am. Chem. Soc. 1995, 117, 6132-6133. 

Reaction of all of the radical pairs within their initial cages does not preclude one or both of the radicals from undergoing a structural change (N. B., step [6] in Scheme 13.1). In the case of photo-Fries reactions, the most commonly encountered structural change is loss of carbon monoxide (CO) from the acyl radical, leading to formation of an alkyl radical. The rates of decarbonylation of acyl radicals have been measured for a wide variety of acyl structures as a function of the medium viscosity... 

Garcia, H., Miranda, M. A., Prime, J. The photo-Fries rearrangement of acetoxyacetophenones using cyclic acetals as carbonyl blocking groups, in the presence of potassium carbonate. An improved procedure for the synthesis of diacylphenols. J. Chem. Res., Synop. 1986, 100-101. 

Katagi, T. Theoretical studies on the photo-Fries rearrangement of O-aryl N-methylcarbamates. Nippon Noyaku Gakkaishi 1991, 16, 57-62. Grimme, S. MO theoretical investigation on the photodissociation of carbon-oxygen bonds in aromatic compounds. Chem. Phys. 1992,163, 313-330. 

Direct Photochemistry of PC Excitation of PC at short wavelength (e.g., 254 nm) involves mainly two consecutive photo-Fries rearrangements of the aromatic carbonate units leading successively to the formation of phenylsalicylate (Li) and dihydroxybenzophenone (L2) units as shown in Scheme 15.9. Photo-Fries products have been well defined by definite maxima in the UV and in the carbonyl range of the IR domain Lj at 320 nm and 1689 cm-1 andL2 at 355 nm and 1629 cm-1. 

Table 5.17 Photo-Fries rearrangement of PAs in the presence of potassium carbonate...

Miscellaneous Polymers - Soluble fluorescent extraction products from poly(acetylene) have been compared with those present in PVC. Photo-Fries rearran ments in the photodegradation of a Bis-Phenol-A poly(carbonate) are responsible for their stability. PTFE has been irradiated using high energy UV and found to give volatile fluorocarbons while photooxidation of poly(phenyl-ene) gives crosslinked and quinone methide products. A polyradical has been made based on poly(3,5-di-tert-butyl-4-[(2,4,6-tri-tert-butylphenyl)oxalato]phe-... 

More than half a century ago, Anderson and Reese reported the first example of a photo-Fries rearrangement (PFR), where 2-hydroxyphenylacetate was converted into 2,3- and 3,4-dihydroxy acetophenone upon UV irradiation [1]. Since then, hundreds of articles have appeared on this reaction, which has been extended from the initial aryl esters to amides, carbonates, carbamates, thioesters, sulfonates, etc. [2-4]. 

The styrylpyridine based polyarylates and their model compounds were synthesized. The order of the relative char yield and oxygen indices were polyarylates > p,p -bis(B-2-vinylpyridyl)diphenyl terephthalate (p,p -BVPDPT) = p,p -2,6-(3-2-vinylpyridyl)diphenyl dibenzoate >(p,p -2,6 -2,6-(B-2-vinylpyridyl)phenyl benzoate (p-VPPB). This is also probably due to the Diels-Alder reaction of the C=C double bonds present in the main chain with the pryidine group. The result is a highly crosslinked C-C bond char. The styrylpyridine based model compounds of the ester and carbonate underwent the Photo-Fries arrangement when irradiated with UV light to give o-hydroxybenzophenone related structures. 

Also obtained by photo-Fries rearrangement of phenyl salicylate (salol) [219] or of phenyl carbonate in ethanol for 150 h (4%) [68]. 

Obtained by photo-Fries rearrangement of p-tert-butylphenyl carbonate,... 

Preparation by photo-Fries rearrangement of 4-chlorophenyl acetate with potassium carbonate in hexane at r.t. (88%) [2015],... 

Also obtained by UV light irradiation of o-tolyl acetate at 25° (photo-Fries rearrangement), in the presence of potassium carbonate in hexane (74%) [2015] or without potassium carbonate in hexane (32%) [2015] or in ethyl ether (16%) [2193],... 

D Andrew, BT Des Islet, A Margaritis, AC Weedon. Photo-Fries rearrangement of naphthyl acetate in supercritical carbon dioxide chemical evidence for solvent-solute clustering. J Am Chem Soc 117 6132-6133, 1995. 

---