photo-Fries Rearrangement Research Articles

Modification of photochemical reactivity by cyclodextrin complexalion: product selectivity in photo-fries rearrangement

Cyclodextrin encapsulation, both in the solid state and in aqueous solution brings about a remarkable regulation of the photo-Fries rearrangement of phenyl esters and anilides. In comparison to the nonselective mixture of ortho and para-rearranged isomers along with the deacylated product obtained in organic solvents, the solid β-cyclodextrin complexes of unsubstituted esters and anilides show a remarkable ‘ortho-selectivity’. An impressive regio-selectivity’ among the two ortho-rearranged isomers is observed for meta-substituted esters and anilides upon irradiation as β-cyclodextrin complexes. Specific orientations of the unsubstituted and meta-substituted esters and anilides in the β-cyclodextrin cavity are suggested to be responsible for the observed selectivity.

Studies on the Synthesis of Preconcenes. The Photo-Fries Rearrangement of Ester of a,b-Unsaturated Carboxylic Acid and meta-Oxygenated Phenols

Studies on the Synthesis of Preconcenes. The Photo-Fries Rearrangement of Ester of a,b-Unsaturated Carboxylic Acid and meta-Oxygenated Phenols

Photolysis of segmented polyurethanes. The role of hard‐segment content and hydrogen bonding

AbstractThe photodegradation of segmented polyurethanes based on methylene 4, 4′‐diphenyldiisocyanate (MDI) is shown to be dependent on the physical structure of the polymer. As the hard segment content of the polyurethane is increased, the photodegradation efficiency is lowered. In particular, the extent of the photolytic decomposition is inversely dependent on the degree of hydrogen bonding in the aryl carbamate groups in the polyurethane backbone. Utilizing appropriate model compounds for comparison, the formation of the ortho photo‐Fries rearrangement product, as detected by fluorescene spectroscopy, is also shown to be dependent onthe degree of hydrogen bonding. In general, the restrictive mobility imposed by hydrogen bonding is a critical factor which must be considered in the photochemistry of segmented polyurethanes.

Kinetic (oxygen-18 and carbon-14) and magnetic (carbon-13) isotope effects in the photo-Fries rearrangement of 4-methoxyphenyl acetate

Kinetic (oxygen-18 and carbon-14) and magnetic (carbon-13) isotope effects in the photo-Fries rearrangement of 4-methoxyphenyl acetate

Photolytic Degradation of Benorylate: Effects of the Photoproducts on Cultured Hepatocytes

The photodegradation of benorylate [4′-(acetamido)phenyl-2-acetoxybenzoate], a drug frequently used in rheumatoid arthritis therapy, has been examined under different sets of experimental conditions. Several photoproducts have been isolated and identified on the basis of their IR, NMR, and MS spectra. The most significant photochemical process is the photo-Fries rearrangement of benorylate, leading to 5-acetamido-2′-acetoxy-2-hydroxybenzophenone (1). This compound undergoes a rapid transacylation to the isomeric 5′-acetamido-2′-acetoxy-2-hydroxybenzophenone (2). A primary culture of rat hepatocytes has been used to evaluate the possible toxicity of these two benzophenones, keeping in mind the following criteria: leakage of cytosolic enzymes, attachment index to culture plates, gluconeogenesis from lactate and fructose, glycogen balance, and albumin synthesis. At the concentrations assayed, neither of the two major photoproducts of benorylate (benzophenones 1 and 2) had significant toxic effects on liver cells in culture.

10-Acetyl-10-hydroxyxantho[2,3-f]tetralin 8-glycosides as angular chromophore analogues of anthracyclines: synthesis, redox properties, microsomal oxygen consumption, and antileukemic evaluation.

10-Acetyl-7,8-dihydroxyxantho[2,3-f]tetralin is obtained by photo-Fries rearrangement of an acylated and double ketal protected tetralin followed by sodium thiocresylate catalyzed rearrangement of the resulting benzoyltetralin. Introduction of the 10-hydroxy function with base, triethyl phosphite, and molecular oxygen affords six products. These include the desired epimeric 10-acetyl-7,8,10-trihydroxyxantho[2,3-f]tetralins in addition to products resulting from novel valence tautomerism and cycloreversion reactions in the oxidation reaction. Glycosidic coupling to the fully functionalized cis-8,10-dihydroxy epimer of the aglycon to protected chlorodaunosamine by a modified Koenigs-Knorr method proceeded satisfactorily. By contrast the epimeric trans-8,10-dihydroxy compound failed to undergo coupling under these conditions. This is attributed to facile competing intramolecular hemiketal formation in the latter case. The new angular glycosides are very resistant to electrochemical reduction and display very low (3-10%) augmentation of hepatic microsomal oxygen consumption relative to doxorubicin. The observed, albeit low, cytotoxicity against leukemia L1210 in cell culture provides an additional example where the presence of the quinone moiety in the parent anthracyclines, which is implicated in the clinical cardiotoxicity, may not be necessary for the expression of anticancer properties.

ChemInform Abstract: Photo‐Fries Rearrangement: Rearrangement of Acetoxybenzene Derivatives.

AbstractPhoto‐Fries rearrangement of the di‐ and triacetoxybenzenes (I), (V) and (VIIIa) gives the acetylphenols shown in the scheme (38‐60% of the starting material is recover‐ 32 ed).

ChemInform Abstract: The Photo‐Fries Rearrangement in the Presence of Potassium Carbonate: A Convenient Synthesis of o‐Hydroxyacetophenones.

Chemischer InformationsdienstVolume 17, Issue 2 Preparative Organic Chemistry ChemInform Abstract: The Photo-Fries Rearrangement in the Presence of Potassium Carbonate: A Convenient Synthesis of o-Hydroxyacetophenones. H. GARCIA, H. GARCIASearch for more papers by this authorJ. PRIMO, J. PRIMOSearch for more papers by this authorM. A. MIRANDA, M. A. MIRANDASearch for more papers by this author H. GARCIA, H. GARCIASearch for more papers by this authorJ. PRIMO, J. PRIMOSearch for more papers by this authorM. A. MIRANDA, M. A. MIRANDASearch for more papers by this author First published: January 14, 1986 https://doi.org/10.1002/chin.198602112AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue2January 14, 1986 RelatedInformation

Magnetic isotope and external magnetic field effects upon the photo-Fries rearrangement of 1-naphthyl acetate

The reaction mechanisms of the photo-Fries rearrangement of 1-naphthyl acetate has been studied by means of steady-state photolysis and laser flash photolysis. A radical pair consisting of the 1-naphthoxyl and acetyl radicals is concluded to be a reaction intermediate. The yield of an in-cage product (2-acetyl-1-naphthol) exhibits a positive external magnetic field effect for the ester labeled by magnetically active /sup 13/C, but no effect for the normal /sup 12/C ester. The magnetic field effect observed for the labeled ester is quantitatively or semiquantitatively explained in terms of the radical-pair mechanism by considering hyperfine coupling between magnetically active nuclei (/sup 1/H and /sup 13/C) and an unpaired electron in the acetyl radical. The in-cage product is formed through the singlet radical pair. 26 references, 5 figures, 3 tables.

Photo-Fries rearrangement: Rearrangement of benzoyloxy compounds

Photo-Fries migration of the benzoyl group in 1-benzoyloxy-5-methoxy naphthalene, 1,4-dibenzoyloxy-2-methyl naphthalene, 1,4-dibenzoyloxy naphthalene, 1,5-dibenzoyloxy naphthalene, 8-benzoyloxy quinoline, 1,2-dibenzoyloxy benzene, 1,3-dibenzoyloxy benzene, and 1,4-dibenzoyloxy benzene afforded the corresponding mono and di-C-benzoyl products.

Synthesis of a 4-acylcyclohexa-2,5-dienone: 3,4-dihydro-3,3,8a-trimethyl-naphthalene-1,6(2H,8aH)-dione

The synthesis is reported of 3,4-dihydro-3,3,8a-trimethylnaphthalene-1,6(2H,8aH)-dione (11; R = Me). This is the first isolated 4-acylcyclohexa-2,5-dienone, a class of compounds postulated particularly as intermediates in the Fries and photo-Fries rearrangements. The dienone undergoes very easy acyl cleavage in the presence of bases or dilute acids, to form a phenolic acid (18). Similar cleavage, or a retro-Fries migration of the acyl group from the 4-position to the dienone ring oxygen, has prevented isolation of 4-acetyl-4-methylcyclohexa-2,5-dienone. Concentrated aqueous sulphuric acid causes rearrangement of the dienone to 3,4-dihydro-8-hydroxy-3,3,5-trimethylnaphtbale-1 (2H)-one (13; R = Me), via recyclisation of (18). In trifluoroacetic acid solutions the same product (13; R = Me) is formed from the dienone by direct, formal dienone–phenol rearrangement.

Cyclic acetals as carbonyl blocking groups in the photo-fries rearrangement of acyl substituted aryl esters.

The ethylene acetals of o and p -acetoxyacetophenone 3a,b, prepared from the corresponding hydroxyacetophenones by treatment with acetic anhydride in pyridine and subsequently with ethylene glycol and p -toluenesulphonic acid, give upon irradiation the expected photo-Fries products 4a,b (from 3a) or 6 (from 3b). These compounds are converted in part into diacetylphenols 5a,b as a consequence of a deacetalization, occurring to some extent during the irradiation and further in the chromatographic workup. The yields of the photoproducts and the ortho / para ratio (in the case of 3a) are very similar to those given in the literature for phenyl acetate. By contrast, the acetoxyacetophenones 2a,b do not undergo any appreciable change upon irradiation,showing the deactivating effect of the acetyl side chain. Therefore, it is concluded that cyclic acetals are suitable carbonyl blocking groups in order to circumvent the deactivating effect of acyl substituents on the photo-Fries rearrangement of aryl esters.

Application of the Photo-Fries Rearrangement of Aryl Dihydrocinnamates to the Synthesis of Flavonoids

Application of the Photo-Fries Rearrangement of Aryl Dihydrocinnamates to the Synthesis of Flavonoids

Wavelength dependence of the surface photo-oxidation of Bisphenol A polycarbonate

ESCA and difference uv techniques have been used to monitor the changes which take place in the surface and bulk chemistry, during photo-oxidation of Bisphenol A polycarbonate, as a function of irradiation wavelength over the range 280–330 nm. Whereas for the surface, the maximum change is observed at 280 nm, in the bulk this occurs at 290 nm. Irradiation at 310 nm, which gives bulk changes similar to natural weathering, does not involve the carbonate group in the surface so that the initial photo-instability of polycarbonate cannot be attributed to a photo-Fries rearrangement of this moiety. The surface photo-reactions are consistent with photo-oxidation.

Regiospecific synthesis of redox inactive ring C modified aglycones related to anthracyclines. Application of photo-Fries rearrangement and novel nucleophile-catalyzed rearrangements leading to the xantho[2,3-g]tetralin and xantho[2,3-f]tetralin systems

Syntheses de benzo [b] xanthenes et de benzo [c] xanthenes a partir de salicyloyl-6 ou 7 tetrahydro-1,2,3,4 naphtalenes

Surface photochemistry: the amide Photo-Fries rearrangement

The Photo-Fries rearrangement of eight anilides on the surface of dry silica gel has been examined. The rearrangement occurs quite cleanly, giving somewhat more of the para isomer than that obtained in methanolic solution. A test for intermolecularity on the silica gel surface showed that, as in solution, the radical pair intermediates do not separate. This contrasts with the behaviour of a previously reported dibenzyl ketone derivative.

Photo-thermal oxidation of thermoplastic polyurethane elastomers: Part 3—Influence of the excitation wavelengths on the oxidative evolution of polyurethanes in the solid state

The detrimental oxidative reactions which occur in thermoplastic polyurethane elastomers based on aromatic isocyanate monomers during irradiation with polychromatic light ( λ > 300 nm) may be accounted for by the interference of two mechanisms. The first mechanism, observed at λ < 330–340 nm, involves a photo-Fries rearrangement. The second mechanism is a photo-induced hydroperoxidation. The photo-Fries products exhibit an anti-ultraviolet effect and partially inhibit the photo-induced oxidation. In contrast to aromatic polyurethane elastomers, aliphatic models exposed to ultraviolet light undergo a photo-induced oxidation which is independent of the excitation wavelength.

Photo-induced reactions of polycarbonate studied by ESR, viscosity and optical absorption measurements

Photo-induced reactions of polycarbonate (PC) have been investigated by electron spin resonance (ESR), viscosity, ultra-violet (UV) and infra-red (IR) absorption measurements. On irradiating PC films with light from a medium-pressure mercury lamp, phenoxy and phenyl type radicals were formed. The viscosity average molecular weight, M v , decreased in the initial stage of the photo-irradiation and then gradually increased to attain a plateau value in the case of photo-irradiation in a vacuum. This behavior is attributed to mainchain scission and micro-gel formation. Phenolic, phenyl salycylate and 2,2′-dihydroxybenzophenone type compounds were detected by both UV and IR absorption measurements. These compounds are probably produced as a result of main-chain scission and subsequent photo-Fries rearrangement. A possible mechanism for the photo-degradation of PC films is proposed on the basis of these observations. The possibility of photostabilization of PC films by the rearrangement products is suggested.

Surface and bulk aspects of the natural and artificial photo-ageing of Bisphenol A polycarbonate as revealed by ESCA and difference UV spectroscopy

ESCA and difference uv spectroscopy have been used to monitor the changes in surface and bulk chemistry, respectively, of Bisphenol A polycarbonate during natural and artificial weathering. It is shown that photo-oxidation, and not a photo-Fries rearrangement mechanism, is the predominant process in the surface regions for both types of exposure. For a close correlation with natural weathering the use of a black lamp as an artificial uv source is advocated. Difference uv spectra obtained for natural and black lamp exposures reveal that changes in bulk chemistry cannot be interpreted in terms of a photo-Fries reaction.

Photo-fries rearrangement of fluorene-based polyarylates

The fluorene-based polyarylates, 9,9-bis(4-hydroxyphenyl)fluorene isophthalate (BPF-I), 9,9-bis(3,5-dimethyl-4-hydroxyphenyl) fluorene isophthalate (BDMPF-I), are synthesized. The formation of the o-hydroxybenzophenone moiety upon UV irradiation of BPF-I and BCF-I is observed in the UV and IR spectra. The degradation of the polymer structure of BDMPF-I is due to its inability to rearrange into the hydroxybenzophenone structure which functions as an internal UV stabilizer. A mechanism for this degradation is postulated based on the evidence from the IR spectra.