- Selective ortho-hydroxylation-defluorination of 2-fluorophenolates with a Bis(μ-oxo)dicopper(III) species
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The bis(μ-oxo)dicopper(III) species [CuIII 2(μ-O)2(m-XYLMeAN)]2+ (1) promotes the electrophilic ortho-hydroxylation-defluorination of 2-fluorophenolates to give the corresponding catechols, a reaction that is not accomplishable with a (η2:η2-O2) dicopper(II) complex. Isotopic labeling studies show that the incoming oxygen atom originates from the bis(μ-oxo) unit. Ortho-hydroxylation-defluorination occurs selectively in intramolecular competition with other ortho-substituents such as chlorine or bromine. O in, F out: [CuIII2(μ-O) 2(m-XYLMeAN)]2+ is a bis(μ-oxo)dicopper(III) species and promotes the electrophilic ortho-hydroxylation-defluorination of 2-fluorophenolates to give the corresponding catechols. Isotopic labeling shows that the incoming oxygen atom originates from the bis(μ-oxo) unit. Ortho-hydroxylation-defluorination occurs selectively in intramolecular competition with other ortho-substituents such as chlorine or bromine.
- Serrano-Plana, Joan,Garcia-Bosch, Isaac,Miyake, Ryosuke,Costas, Miquel,Company, Anna
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supporting information
p. 9608 - 9612
(2014/10/15)
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- Tyrosinase-like reactivity in a CuIII2(??-O) 2 species
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A study was conducted to demonstrate a bis(??-oxo)dicopper(III) species that binds and ortho-hydroxylates phenolates for reactivity of tyrosinase. The study characterized a metastable species from the low-temperature reaction of sodium p-chloro-phenolate (p-Cl-C6H4ONa) with a bis(??-oxo)dicopper(III) species. The study found that the addition of 10 equivalents of the sodium salt of p-chlorophenol at -90?°C can cause bleaching of the spectral features. High performance liquid chromatography (HPLC) analysis showed that 4-chlorocatechol was formed in 76% yield. The study used UV/UVis monitoring for reaction in acetone to determine the initial features to the bis(??-oxo) species and found that these features disappear after phenolate addition. The study observed that the activation parameters for the monophenolase reaction catalyzed by tyrosinase.
- Company, Anna,Palavicini, Sara,Garcia-Bosch, Isaac,Mas-Ballesteì?, Ruben,Que Jr., Lawrence,Rybak-Akimova, Elena V.,Casella, Luigi,Ribas, Xavi,Costas, Miquel
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supporting information; experimental part
p. 3535 - 3538
(2009/05/07)
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- PHOSPHAZENE COMPOUND, LUBRICANT AND MAGNETIC RECORDING MEDIUM HAVING SUCH COMPOUND, METHOD OF PREPARATION, AND METHOD OF LUBRICATION
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A compound of the formula: (I) is provided, where R is selected from CF3, F, and H, and m is an integer from 1 to 22. The compound may be prepared by reacting a first reactant with a second reactant in a solution, where the first reactant is a 2,4-dichloro-2,4,6,6- tetra(aryloxy)-1,3,5-triaza-2,4,6-triphosphorine, and the second reactant is a perfluoropolyether of the formula CF3CF2CF2O(CF2CF2CF2O)mCF2CF2CH2OH. The aryloxy is selected from 4-(trifluoromethyl)phenoxy (p -CF3-C6H4O), 4-fluorophenoxy (p-F-C6H4O), and phenoxy (C6H5O). The first reactant may be prepared by reacting 2,2,4,4,6,6-hexachloro-1,3,5-triaza-2,4,6-triphosphorine with a phenoxide. The compound may be used in a lubricant for lubricating a surface. The lubricant may be applied to a recording surface in a magnetic recording device including a recording medium.
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Page/Page column 10
(2008/06/13)
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- Do electrostatic interactions with positively charged active site groups tighten the transition state for enzymatic phosphoryl transfer?
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The effect of electrostatic interactions on the transition-state character for enzymatic phosphoryl transfer has been a subject of much debate. In this work, we investigate the transition state for alkaline phosphatase (AP) using linear free-energy relationships (LFERs). We determined fcat/K M for a series of aryl sulfate ester monoanions to obtain the Bronsted coefficient, βIg, and compared the value to that obtained previously for a series of aryl phosphorothioate ester dianion substrates. Despite the difference in substrate charge, the observed Bronsted coefficients for AP-catalyzed aryl sulfate and aryl phosphorothioate hydrolysis (-0.76 ± 0.14 and -0.77 ± 0.10, respectively) are strikingly similar, with steric effects being responsible for the uncertainties in these values. Aryl sulfates and aryl phosphates react via similar loose transition states in solution. These observations suggest an apparent equivalency of the transition states for phosphorothioate and sulfate hydrolysis reactions at the AP active site and, thus, negligible effects of active site electrostatic interactions on charge distribution in the transition state.
- Nikolic-Hughes, Ivana,Rees, Douglas C.,Herschlag, Daniel
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p. 11814 - 11819
(2007/10/03)
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- EFFECT OF THE STRUCTURE OF THE LEAVING GROUP, MEDIUM, AND TEMPERATURE ON THE ALKALINE HYDROLYSIS OF PHENYL BENZOATES IN WATER-DIOXANE MIXTURES
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A spectrophotometric study was carried out on the kinetics of the alkaline hydrolysis of a series of para-substituted phenyl benzoates PhCO2C6H4X-p in water, 30 and 70 vol. percent aqueous dioxane at 15 deg, 25 deg, and 55 deg C.The bimolecular rate constants depend on the medium composition, temperature, and structure of the leaving group.It is of value to apply linear free energy (LFE) principles in studying these factors, which permits description of the entire set of experimental data by a single multidimensional regression equation.The Arrhenius equation parameters were calculated and this reaction series was shown to be compensated, in contrast to the alkaline hydrolysis of phenyl acetates.The dependence of the ρ constants in the Hammett-Taft equation on the medium composition and temperature indicate that this value is not a linear function of the extent of formation and breakage of bonds in the transition state.
- Sukhoruchkov, Yu. I.,Polonov, V. M.,Finkel'shtein, B. L.,Istomin, B. I.
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p. 1014 - 1019
(2007/10/02)
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