3669-52-1Relevant articles and documents
Magnetic Isotope and External Magnetic Field Effects upon the Photo-Fries Rearrangement of 1-Naphthyl Acetate
Nakagaki, Ryoichi,Hiramatsu, Mitsuo,Watanabe, Takeshi,Tanimoto, Yoshifumi,Nagakura, Saburo
, p. 3222 - 3226 (1985)
The reaction mechanism of the photo-Fries rearrangement of 1-naphtyl acetate has been studied by means of steady-state photolysis and laser flash photolysis.A radical pair consisting of the 1-naphtoxyl and acetyl radicals is concluded to be a reaction intermediate.The yield of an in-cage product (2-acetyl-1-naphtol) exhibits a positive external magnetic field effect for the ester labeled by magnetically active 13C, but no effect for the normal 12C ester.The magnetic field effect observed for the abeled ester is quantitatively or semiquantitatively explained in terms of the radical-pair mechanism by considering hyperfine coupling between magnetically active nuclei (1H and 13C) and an unpaired electron in the acetyl radical.The in-cage product is formed through the singlet radical pair.
Laser flash photolysis and CIDNP studies of 1-naphthyl acetate photo-fries rearrangement
Gritsan, Nina P.
, p. 4448 - 4458 (1996)
The steady-state and time-resolved CIDNP and flash photolysis methods were used in a detailed study of the photo-Fries rearrangement of 1-naphthyl acetate (I) in acetonitrile and methanol. The main reaction channel is the decay of I through the excited singlet state with the quantum yields 0.17 ±0.02 in acetonitrile and 0.42 ± 0.04 in methanol at room temperature. The absorption spectra of the naphthoxyl radical and triplet state of 1-naphthyl acetate were detected. The quantum yield of triplet was estimated as 0.4 ±0.2 and 0.35 ± 0.17 in acetonitrile and methanol, respectively. It has been established that the triplet-born radical pairs make a main contribution to the CIDNP of the photo-Fries rearrangement products. The involvement in the process of two different triplet states of I was supposed. The main decay channel of the lowest triplet state is the triplet-triplet annihilation, while the CIDNP of photo-Fries rearrangement products results from the decay of the upper triplet state of I with a lifetime of a few nanoseconds. The kinetics of CIDNP formation in reaction products has been analyzed, and the rate constants of the rearrangement of the preceding intermediates at room temperature have been estimated.
Photorelease of phosphates: Mild methods for protecting phosphate derivatives
Senadheera, Sanjeewa N.,Yousef, Abraham L.,Givens, Richard S.
, p. 2038 - 2054 (2014/11/07)
We have developed a new photoremovable protecting group for caging phosphates in the near UV. Diethyl 2-(4-hydroxy-1-naphthyl)- 2-oxoethyl phosphate (14a) quantitatively releases diethyl phosphate upon irradiation in aq MeOH or aq MeCN at 350 nm, with quantum efficiencies ranging from 0.021 to 0.067 depending on the solvent composition. The deprotection reactions originate from the triplet excited state, are robust under ambient conditions and can be carried on to 100% conversion. Similar results were found with diethyl 2-(4-methoxy-1-naphthyl)-2-oxoethyl phosphate (14b), although it was significantly less efficient compared with 14a. A key step in the deprotection reaction in aq MeOH is considered to be a Favorskii rearrangement of the naphthyl ketone motif of 14a,b to naphthylacetate esters 25 and 26. Disruption of the ketone-naphthyl ring conjugation significantly shifts the photoproduct absorption away from the effective incident wavelength for decaging of 14, driving the reaction to completion. The Favorskii rearrangement does not occur in aqueous acetonitrile although diethyl phosphate is released. Other substitution patterns on the naphthyl or quinolin-5-yl core, such as the 2,6-naphthyl 10 or 8-benzyloxyquinolin-5-yl 24 platforms, also do not rearrange by aryl migration upon photolysis and, therefore, do not proceed to completion. The 2,6-naphthyl ketone platform instead remains intact whereas the quinolin-5-yl ketone fragments to a much more complex, highly absorbing reaction mixture that competes for the incident light.
Comparisons of O-acylation and Friedel-Crafts acylation of phenols and acyl chlorides and Fries rearrangement of phenyl esters in trifluoromethanesulfonic acid: Effective synthesis of optically active homotyrosines
Murashige, Ryo,Hayashi, Yuka,Ohmori, Syo,Torii, Ayuko,Aizu, Yoko,Muto, Yasuyuki,Murai, Yuta,Oda, Yuji,Hashimoto, Makoto
experimental part, p. 641 - 649 (2011/03/19)
Reactions involving phenol derivatives and acyl chlorides have to be controlled for competitive O-acylations and C-acylations (Friedel-Crafts acylations and Fries rearrangements) in acidic condition. The extent for these reactions in trifluoromethanesulfonic acid (TfOH), which is used as catalyst and solvent, is examined. Although diluted TfOH was needed for effective O-acylation, concentrated TfOH was required for effective C-acylations in mild condition. These results have been applied to the novel synthesis of homotyrosine derivatives. Both Fries rearrangement of N-TFA-Asp(OBn)-OMe and Friedel-Crafts acylation of phenol with N-TFA-Asp(Cl)-OMe in TfOH afforded the homotyrosine skeleton, followed by reduction and deprotection afforded homotyrosines maintaining stereochemistry of Asp as an optically pure form.
Improvement of Selectivity in the Fries Rearrangement and Direct Acylation Reactions by Means of P2O5/SiO2 Under Microwave Irradiation in Solvent-Free Media
Eshghi, Hossein,Rafie, Mohammad,Gordi, Zinat,Bohloli, Moosa
, p. 1258 - 1270 (2007/10/03)
P2O5/SiO2 was found to be an efficient new reagent for the Fries rearrangement of acyloxy benzene or naphthalene derivatives and the direct acylation reactions of phenol and naphthol derivatives with carboxylic acids. The reactions proceeded smoothly in the solid state and are highly selective methods for the preparation of the ortho isomers of hydroxyaryl ketones. Microwave irradiation improved the conversion yield to 85-100 percent and the high ortho-regioselectivity of these reactions provides an efficient and versatile procedure for obtaining o-hydroxyaryl ketones in 47-98 percent yield.
Linear Bronsted-type behavior in the aminolysis of substituted naphthyl acetates
Rajarathnam,Ananthakrishna Nadar
, p. 157 - 164 (2007/10/03)
The reactions of 4-acetyl-1-naphthyl acetate (1) and 6-acetyl-2-naphthyl acetate (2) with a series of amines of varying pKa, viz. morpholine, ammonia, ethanolamine, glycine, n-butylamine, piperidine, hydrazine, imidazole, and hydroxylamine, are subjected to a kinetic investigation in aqueous medium, 30 °C, ionic strength 0.1 M (KCl). Pseudo-first-order rate coefficients (kobs) are found under amine excess. The plots of (kobs-kH) against free amine concentration are linear at constant pH. The macroscopic nucleophilic substitution rate coefficients (kN) are obtained as the slopes of these plots and found to be pH-independent for all the amines employed. The Bronsted-type plots obtained (log kN against amine pKa) for the aminolysis of both esters 1 and 2 are linear with slope values of β = 0.74 and β = 0.94, respectively. From these values, the kinetic law and the analysis of products, it is deduced that for both esters aminolysis proceed through a zwitterionic tetrahedral addition intermediate (T±) whereby its dissociation into products is rate-limiting (k2 step). Comparison of kN values among them shows that both esters follow an identical mechanistic pathway with 1 having higher reactivity than 2, the reasons for which are discussed.
Effect of cyclodextrin complexation on photo-fries rearrangement of naphthyl esters
Banu, Habeeb Shayira,Pitchumani, Kasi,Srinivasan, Chockalingam
, p. 9601 - 9610 (2007/10/03)
Photolysis of β-cyclodextrin inclusion complexes of 1- and 2-naphthyl esters (acetates and benzoates) in aqueous medium, results in rearrangement to give one isomer of acylnaphthol in excess, whereas the solid state irradiation of the cyclodextrin complexes yields selectively one isomer. In addition, formation of cleavage product is totally suppressed. This remarkable selectivity is attributed to specific modes of the complexation of the esters into the β-CD cavity.
Kinetics and mechanism of ammonolysis and alkaline hydrolysis of naphthyl acetates in aqueous medium: Part 1 - 4-Substituted 1-naphthyl acetates
Ananthakrishna Nadar,Rajarathinam
, p. 749 - 753 (2007/10/03)
A series of 4- substituted 1-naphthyl acetates have been prepared. The kinetics of their ammonolysis have been followed at 20°, 25° and 30°C under pseudo-first order conditions at different pH in water containing 1% dioxan at an ionic strength of 1.0 mol dm-3. The possible mechanisms suggest the existence of general base catalysis for 4-methyl-1-naphthyl acetate. For esters with electron-withdrawing substituents, ammonolysis proceeds through an unassisted simple nucleophilic substitution pathway. The alkaline hydrolysis of all the esters is also followed under identical reaction conditions.
Photo-Fries reaction of naphthyl esters within zeolites
Pitchumani,Warrier,Cui,Weiss,Ramamurthy
, p. 6251 - 6254 (2007/10/03)
Photolysis of naphthyl esters within zeolites leads to the photo-Fries rearrangements as in isotropic solution. However, a high level of product selectivity is obtained using 'cation as the key'. A key component for predicting the selectivity of photoreactions within zeolites, namely the location of reactants, is missing at this stage.
