Reaction Of Catechol Research Articles

Domino Oxidation-Michael Reactions of Catechols with Barbituric Acid Derivatives in Water: An Efficient Synthesis of Polycyclic Pyrimidinones

The oxidative coupling reaction of catechols with barbituric acid derivatives, mediated by ferricyanide, has been investigated in aqueous solution. The results indicate that the barbituric acid derivatives participate in Michael-type addition reactions with in situ generated ortho-benzoquinones, in a domino fashion, to afford a variety of polycyclic pyrimidinones. The method provides a one-step, rapid and efficient procedure for synthesizing a range of polycyclic pyrimidinones of biological significance.

Functional model for intradiol-cleaving catechol 1,2-dioxygenase: Synthesis, structure, spectra, and catalytic activity of iron(III) complexes with substituted salicylaldimine ligands

A series of mononuclear iron(III) complexes with containing phenolate donor of substituted-salicylaldimine based ligands [Fe(L 1)(TCC)] · CH 3OH ( 1), [Fe(L 2)(TCC)] · CH 3OH ( 2), [Fe(L 3)(TCC)] ( 3), and [Fe(L 4)(TCC)] ( 4) have been prepared and studied as functional models for catechol dioxygenases (H 2TCC = tetrachlorocatechol, or HL 1 = N′-(salicylaldimine)- N, N-diethyldiethylenetriamine, HL 2 = N′-(5-Br-salicylaldimine)- N, N-diethyldiethylenetriamine, HL 3 = N′-(4,6-dimethoxy-salycyl-aldimine)- N, N-diethyl-diethylenetriamine, HL 4 = N′-(4-methoxy-salicylaldimine)- N, N-diethyl-diethylenetriamine). They are structural models for inhibitors of enzyme-substrate adducts from the reactions of catechol 1,2-dioxygenases. Complexes 1– 4 were characterized by spectroscopic methods and X-ray crystal structural analysis. The coordination sphere of Fe(III) atom of 1– 4 is distorted octahedral with N 3O 3 donor set from the ligand and the substrate TCC occupying cis position, and Fe(III) is in high-spin ( S = 5/2) electronic ground state. The in situ prepared iron(III) complexes without TCC, [Fe(L 1)Cl 2], [Fe(L 2)Cl 2], [Fe(L 3)Cl 2], and [Fe(L 4)Cl 2] are reactive towards intradiol cleavage of the 3,5-di- tert-butylcatechol (H 2DBC) in the presence of O 2 or air. The reaction rate of catechol 1,2-dioxygenase depends on the redox potential and acidity of iron(III) ions in complexes as well as the substituent effect of the ligands. We have identified the reaction products and proposed the mechanism of the reactions of these iron(III) complexes with H 2DBC with O 2.

Selective electrochemical reactions of an alumina hydrate crystallization inhibitor

Selective reactions of catechol have been studied in regard to its inhibition properties towards alumina hydrate crystallization. Electrochemical reactions of the inhibitor leading to products without inhibition behaviour have been obtained using different conditions. First, a pure sodium hydroxide solution (1.0 M NaOH) was used to electrochemically react the catechol. The inhibitor reactions were then carried out in both saturated and supersaturated sodium aluminate solutions (NaAl(OH)4). Electrocatalytic hydrogenation (ECH) of the aromatic ring over rhodium-based catalysts leads to the saturated non-inhibiting molecule, 1,2-cyclohexanediol. Temperature shows no significant influence on the ECH process within the temperature range where the alumina hydrate crystallization is normally carried out. The presence of aluminate ions in solution has, however, a detrimental effect on the current efficiency. Electro-oxidation of the catechol produces muconic acid by cleavage of the carbon-carbon bound. It also produces other oxidation products and, eventually, may lead to total mineralization of catechol into carbonate, which is a less inhibiting molecule. A detrimental effect of the presence of aluminate on the electro-oxidation is also observed. Electrochemical techniques are proposed as new pathways for organic control in caustic medium.

Kinetic modelling of phenol hydroxylation using titanium and tin silicalite-1s: Effect of tin incorporation

Abstract Effects of tin incorporation in titanium silicalite-1 (TS-1) on the kinetic modelling of phenol hydroxylation to dihydroxybenzenes with aqueous hydrogen peroxide have been investigated. The modelling of the hydroxylation reaction was from the results of a batch reactor, minimizing mass transfer conditions. The kinetic analysis indicates that under the same reaction conditions, titanium-tin silicalite-1 (Ti-Sn-S-1) gave a higher phenol conversion rate than TS-1. This was attributed to the Sn active sites. Incorporation of tin influences the initiation of intermediate reactions of products with hydrogen peroxide. Tin increases the rate of benzoquinone conversion to tar; however, it does not affect hydroquinone and catechol reactions. A Langmuir–Hinshelwood-type mechanism model was used to fit the proposed phenol hydroxylation and parallel reactions of products with the observed rate data. The intrinsic kinetic constants were found to be proportional to the concentration of reactants and the Ti and Sn active sites. The surface reaction yielded the best fit of the model for reactions in the system. It however failed to predict the outcome of the catechol reaction using TS-1, in which the catechol adsorption on the Ti active site was rate-limiting. The model fitted to the experimental data generated in this study was determined to provide the best values for the kinetic parameters. The effect of temperature on the hydroxylation rate is also documented in further detail.

Electrosynthesis of polyaniline in ionic liquid and its electrocatalytic properties

Ionic liquid like 1-butyl-3-methyl-imidazolium tetrafluorobrate ([BMIM]BF4) has been used as solvent and electrolyte for the electropolymerization of aniline at glassy carbon electrode by cyclic voltammetry. Electrode modified with polyaniline (PAn) has obvious electrochemical activity in ionic liquid and acid solution (pH 0–4), and has significant electrocatalytic activity for redox reaction of catechol and hydroquione.

Preparation and characterization of Melanorrhoea usitata lacquer film based on pyrolysis–gas chromatography/mass spectrometry

3-(10-Phenyldecyl)catechol was synthesized by the reaction of catechol and 1-phenyl-10-iododecane, followed by de-protection of the hydroxyl groups of catechol; it was then polymerized into synthetic lacquer film by laccase enzyme, and characterized using pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) in order to reveal the polymerization mechanism of Melanorrhoea usitata lacquer. The molecular weight and molecular structure information for each peak in the total ion chromatograms (TIC) were obtained from the mass spectra analysis. In addition, the synthesized 3-(10-phenyldecyl)catechol monomer and its lacquer films were also investigated by IR and NMR measurement. The results showed that quinone produced by the laccase formed a C O bond not with the phenyl group but with the catechol ring of 3-(10-phenyldecyl)catechol, and 3-(10-phenyldecyl)catechol is only polymerized by the laccase to produce a lacquer film.

Electroenzymatic reactions with oxygen on laccase-modified electrodes in anhydrous (pure) organic solvent

The electroenzymatic reactions of Trametes hirsuta laccase in the pure organic solvent dimethyl sulfoxide (DMSO) have been investigated within the framework for potential use as a catalytic reaction scheme for oxygen reduction. The bioelectrochemical characteristics of laccase were investigated in two different ways: (i) by studying the electroreduction of oxygen in anhydrous DMSO via a direct electron transfer mechanism without proton donors and (ii) by doing the same experiments in the presence of laccase substrates, which display in pure organic solvents both the properties of electron donors as well as the properties of weak acids. The results obtained with laccase in anhydrous DMSO were compared with those obtained previously in aqueous buffer. It was shown that in the absence of proton donors under oxygenated conditions, formation of superoxide anion radicals is prevented at bare glassy carbon and graphite electrodes with adsorbed laccase. The influence of the time for drying the laccase solution at the electrode surface on the electroreduction of oxygen was studied. Investigating the electroenzymatic oxidation reaction of catechol and hydroquinone in DMSO reveals the formation of various intermediates of the substrates with different electrochemical activity under oxygenated conditions. The influence of the content of aqueous buffer in the organic solvent on the electrochemical behaviour of hydroquinone/1,4-benzoquinone couple was also studied.

The Effects of Intramolecular Hydrogen Bonding on the Reaction of Phenols with Epoxide in the Presence of Nano Calcium Carbonate

The reaction of phenols and dihydroxybenzenes with epoxide in the presence of nano CaCO3 was studied. Catechol could react with epoxide and gave monochlorohydrin derivative; other dihydroxybenzenes and monomeric phenols had no reaction under the same conditions. The reaction of catechol with epoxide did not occur when nano CaCO3 was replaced by a normal one. These were attributed to the strong interaction between nano CaCO3 and the substrate as catechol possessed intrahydrogen bond and excess active hydrogen, which can induce the intramolecular proton transfer via the intramolecular hydrogen bond and promote the reaction of hydroxyl and epoxide. This is an example revealing the unique role of the hydrogen bond played in chemical reactions.

Oxidation of catechol to muconic acid: A theoretical study

The oxidation reaction of catechol to cis– cis muconic acid was studied with the B3LYP density functional and the 6-311G** basis set to explore the singlet and triplet potential surfaces. The singlet potential surface was treated with the broken symmetry formalism, and the stability of the wave function was confirmed. The calculations indicate that, in absence of catalyst, the reaction must undergo photo-excitation in order to promote the system to the singlet potential surface, which leads to a lower-lying transition state and the final products. Oxidation is a two step process; the singlet transition state is peroxide-like, while that of the triplet state involves a cyclic structure. Intermediates along the triplet surface lie at substantially higher energy.

Possible involvement of NO-mediated oxidative stress in induction of rat forestomach damage and cell proliferation by combined treatment with catechol and sodium nitrite

To clarify the mechanisms underlying forestomach carcinogenesis in rats by co-treatment with catechol and sodium nitrite (NaNO 2), we investigated the involvement of oxidative stress resulting from reaction of the two compounds. Since generation of semiquinone radical, hydroxyl radical ( OH), and peroxynitrite (ONOO −) arose through the reaction of catechol with NO, we proposed that superoxide resulting from catechol oxidation reacted with excess NO, consequently yielding OH via ONOO −. Male F344 rats were co-treated with 0.2% catechol in the diet and 0.8% NaNO 2 in the drinking water for 2 weeks. Prior to occurrence of histological evidence indicating epithelial injury and hyperplasia, 8-hydroxydeoxyguanosine levels in forestomach epithelium significantly increased from 12 h together with appearance of immunohistochemically nitrotyrosine-positive epithelial cells. There were no remarkable changes in rats given each chemical alone. We conclude that oxidative stress due to NO plays an important role in induction of forestomach epithelial damage, cell proliferation, and thus presumably forestomach carcinogenesis.

Iron acquisition mechanisms of Flavobacterium psychrophilum

Forty strains of Flavobacterium psychrophilum were tested for the production of siderophores using the universal Chrome Azurol S (CAS) assay. The majority of the strains (85%) were CAS positive (CAS+) and some (15%) were CAS negative (CAS-). The cryptic plasmid pCP1 was carried by all positive strains and was lacking from negative strains. While a weak catechol reaction was detectable in CAS+ culture supernatants, the CAS reaction was, to some extent, heat sensitive, questioning whether the positive reaction was caused only by siderophores. The ability to grow in vitro under iron-restricted conditions did not correlate with the CAS reactivity, as growth of both CAS+ and CAS- strains was similarly impaired under iron restriction induced by 2,2 dipyridyl. Suppressed growth under these conditions was restored by addition of FeCl3, haemoglobin and transferrin for both CAS+ and CAS- strains.

Influence of chemical kinetics on postcolumn reaction in a capillary Taylor reactor with catechol analytes and photoluminescence following electron transfer.

Postcolumn derivatization reactions can enhance detector sensitivity and selectivity, but their successful combination with capillary liquid chromatography has been limited because of the small peak volumes in capillary chromatography. A capillary Taylor reactor (CTR), developed in our laboratory, provides simple and effective mixing and reaction in a 25-microm-radius postcolumn capillary. Homogenization of reactant streams occurs by radial diffusion, and a chemical reaction follows. Three characteristic times for a given reaction process can be predicted using simple physical and chemical parameters. Two of these times are the homogenization time, which governs how long it takes the molecules in the analyte and reagent streams to mix, and the reaction time, which governs how long the molecules in a homogeneous solution take to react. The third characteristic time is an adjustment to the reaction time called the start time, which represents an estimate of the average time the analyte stream spends without exposure to reagent. In this study, laser-induced fluorescence monitored the extent of the postcolumn reaction (reduction of Os(bpy)3(3+) by analyte to the photoluminescent Os(bpy)3(2+)) in a CTR. The reaction time depends on the reaction rates. Analysis of product versus time data yielded second-order reaction rate constants between the PFET reagent, tris(2,2'-bipyridine)osmium, and standards ((ferrocenylmethyl)trimethylammonium cation and p-hydroquinone) or catechols (dopamine, epinephrine, norepinephrine, 3, 4-dihydroxyphenylacetic acid. The extent of the reactions in a CTR were then predicted from initial reaction conditions and compared to experimental results. Both the theory and experimental results suggested the reactions of catechols were generally kinetically controlled, while those of the standards were controlled by mixing time (1-2 s). Thus, the extent of homogenization can be monitored in a CTR using the relatively fast reaction of the reagent and p-hydroquinone. Kinetically controlled reactions of catechols, however, could be also completed in a reasonable time at increased reagent concentration. A satisfactory reactor, operating at 1.7 cm/s (2 microL/min) velocity with solutes having diffusion coefficients in the 5 x 10(-6) cm2/s range, can be constructed from 8.0 cm of 25-microm-radius capillary. Slower reactions require longer reaction times, but theoretical calculations expect that a CTR does not broaden a chromatographic peak (N = 14 000) from a 100-microm-capillary chromatography column by 10% if the pseudo-first-order rate constant is larger than 0.1 s(-1).

Inhibition of brain mitochondrial respiration by dopamine and its metabolites: implications for Parkinson's disease and catecholamine‐associated diseases

A structure-potency study examining the ability of dopamine (DA), its major metabolites and related amine and acetate congeners to inhibit NADH-linked mitochondrial O(2) consumption was carried out to elucidate mechanisms by which DA could induce mitochondrial dysfunction. In the amine studies, DA was the most potent inhibitor of respiration (IC(50) 7.0 mm) compared with 3-methoxytryramine (3-MT, IC(50) 19.6 mm), 3,4-dimethoxyphenylethylamine (IC(50) 28.6 mm), tyramine (IC(50) 40.3 mm) and phenylethylamine (IC(50) 58.7 mm). Addition of monoamine oxidase (MAO) inhibitors afforded nearly complete protection against inhibition by phenylethylamine, tyramine and 3,4-dimethoxyphenylethylamine, indicating that inhibition arose from MAO-mediated pathways. In contrast, the inhibitory effects of DA and 3-MT were only partially prevented by MAO blockade, suggesting that inhibition might also arise from two-electron catechol oxidation and quinone formation by DA and one-electron oxidation of the 4-hydroxyphenyl group of 3-MT. In the phenylacetate studies, 3,4-dihydroxyphenylacetic acid (DOPAC) was equipotent with DA in inhibiting respiration (IC(50) 7.4 mm), further implicating the catechol reaction as the cause of inhibition. All other carboxylate congeners; phenylacetic acid (IC(50) 13.0 mm), 4-hydroxyphenylacetic acid (IC(50) 12.1 mm), 4-hydroxy-3-methoxyphenylacetic acid (HVA, IC(50) 12.0 mm) and 3,4-dimethoxyphenylacetic acid (IC(50) 10.2 mm), were equipotent respiratory inhibitors and two- to fourfold more potent than their corresponding amine. These latter findings suggest that the phenylacetate ion can also contribute independently to mitochondrial inhibition. In summary, mitochondrial respiration can be inhibited by DA and its metabolites by four distinct MAO-dependent and independent mechanisms.

Removal of catechol from aqueous solution by advanced photo-oxidation process

A comprehensive experimental investigation has been made on removal of catechol from aqueous solution by advanced photo-oxidation with hydrogen peroxide in presence of UV light. The effect of different process parameters, such as initial substrate concentration, H 2O 2 to substrate concentration ratio, addition of a solid catalyst (ferrous sulfate) has been studied. It was found that initial rate of conversion of catechol was extremely high compared to the later part of the reaction. Conversion attained within around 10 min of reaction accounted for approximately 90–95% of the conversion attained within 60 min of reaction. A kinetic model for degradation of catechol has been developed, which shows that the degradation reaction of catechol with UV/H 2O 2 follows a pseudo second-order pathway.

Electrode Reactions of Catechol at Tyrosinase‐Immobilized Latex Suspensions

AbstractTyrosinase was immobilized on polystyrene latex particles in order to control amounts of the enzyme. The tyrosinase‐coated latex particles were composed of the core polystyrene and four successive coating layers: polystyrene sulfonate, polyallylamine, tyrosinase and polyallylamine again, built up by the layer‐by‐layer technique. They showed catalytic currents for the enzymatic oxidation of catechol to o‐quinone. The enzyme activity per particle was evaluated as 2.3×10−7 units from UV absorption of o‐quinone. The relation between the catalytic current and the concentration of catechol leads to a Michaelis‐Menten type kinetic equation. The layer‐by‐layer method was found to have a deactivating effect on enzyme catalysis. In spite of this, the catechol oxidation current was larger than the current from free tyrosinase at a common value of enzyme units per volume. This is ascribed to strong adsorption of the latex particles on the electrode, leading to the enhancement of the local concentration of tyrosinase.

Investigation of the electro-oxidation and oxidation of catechol in the presence of sulfanilic acid

The electrochemical oxidation of catechol (1) in the presence of sulfanilic acid (2) was investigated. Some electrochemical (EC) techniques such as cyclic voltammetry and controlled-potential coulometry were used. The oxidation reaction of catechol (1) with periodate in the presence of sulfanilic acid (2) was also investigated spectrophotometrically. The results indicate that the o-quinone derived from catechol participate in Michael addition reaction with sulfanilic acid (2). In addition, according to the ECE mechanism, the observed homogeneous rate constant (kobs) for the reaction of o-quinone derived from catechol (1) with sulfanilic acid (2) has been estimated by digital simulation of cyclic voltammograms.

Six Coordinate Tris(catecholato)silicates of Primary Amine Residues—Synthesis, Characterization, and Thermolysis Studies. X-Ray Structures of [n-C3H7NH3]2[Si(C6H4O2)3]·1/2(C6H14N2) and of a Bulky Secondary Ammonium Ion, [(i-C4H9)2NH2]2[Si(C6H4O2)3]·H2O

Synthesis of the hypervalent tris(catecholato)silicate ion, [(C6H4O2)3-Si]2− having five different primary ammonium cations viz. n-propylammonium (1), isopropylammonium (2) n-butylammonium (3), cyclohexylammonium (4), benzylammonium (5), and a bulky secondary ammonium cation, namely diisobutylammonium (6), have been achieved by the reaction of catechol and tetraethoxysilane (TEOS) in presence of the corresponding amine. Elemental analysis, IR, NMR (1H, 13C, and 29Si), and mass spectral data have been used for their characterization. Single crystal x-ray structures of 1 and 6 indicate nearly same distortion of the “SiO6” octahedron but interesting differences in the hydrogen bonding interactions arising from the catecholato oxygens and the N—H bonds of the ammonium cations. While compound 1 exhibits hydrogen bonding more discretely and by revealing strong interaction between the n-propylammonium ions, compound 6 shows an extended intermolecular hydrogen bonding aided by a water molecule present in the lattice to lead to infinite one dimensional chain arrangement. TG and EG analyses of compounds, 1–5 indicate 1) the formation of the previously observed spirosilane intermediate, [Si(C6H4O2)2] and 2) their less thermal stability compared to those having secondary or tertiary ammonium cations.

Synthesis of mono and binuclear copper(II) complexes using new macrobicyclic tricompartmental unsymmetrical ligands: magnetic, electrochemical and catalytic studies

A series of new mono and binuclear copper(II) complexes [CuL 1a–eH 2](ClO 4) 2 and [Cu 2L 1a–e(ClO 4)](ClO 4), where L is a macrobicyclic tricompartmental ligand obtained from the condensation of the precursor compound (PC) 3,4:10,11-dibenzo-1,13[ N, N ′-bis{(3-formyl-2-hydroxy-5-methyl) benzyl}diaza]-5,9-dioxocyclohexadecane with various diamines have been synthesized. In this system, there are three compartments: the first compartment (N 2O 2) comprises two ether oxygens and two tertiary nitrogens, the second compartment (N 2O 2) contains two tertiary nitrogens and two phenolic oxygens and the third compartment (N 2O 2) is composed of two phenolic oxygens and two imine nitrogens. In mononuclear complexes the geometry of copper(II) ion present in the phenolic oxygen and imine nitrogen compartment is distorted square planar and in binuclear complexes the geometry of Cu(II) ion present in imine nitrogen and phenolic oxygen compartment is distorted square planar and the another Cu(II) ion present in phenolic oxygen and tertiary nitrogen compartment is square pyramidal. The synthesized complexes were characterized by spectroscopic (IR, UV–Vis and ESR) techniques. Electrochemical studies of the complexes reveal that all the mononuclear copper(II) complexes show a single quasireversible one-electron transfer reduction wave ( E pc=−0.76 to −0.84 V) and the binuclear complexes show two quasireversible one-electron transfer reduction waves ( E 1 pc=−0.86 to −1.01 V, E 2 pc=−1.11 to −1.43 V) in the cathodic region. The ESR spectra of the mononuclear complexes show four lines with nuclear hyperfine splittings with the observed g ∥ values in the range 2.20–2.28, g ⊥=2.01–2.06 and A ∥=125–273. The binuclear complexes show a broad ESR spectra with g=2.10–2.11. The room temperature magnetic moment values for the mononuclear complexes are in the range [ μ eff =(1.70 to 1.72) BM] and for the binuclear complexes the range is [ μ eff =(1.46 to 1.59) BM]. Variable temperature magnetic susceptibility study of the binuclear complex [Cu 2L 1d(ClO 4)](ClO 4) shows that the observed −2 J value is 225 cm −1. The calculated initial rate constant values for oxidation reaction of catechol to o-quinone ranges from 8.52 × 10 −3 to 3.08 × 10 −2 min −1. The catalytic activity of binuclear copper(II) complexes (1.65 × 10 −2 to 3.08 × 10 −2 min −1) is higher than the mononuclear copper(II) complexes (8.52 × 10 −3–9.67 × 10 −3 min −1).

Dopamine Prevents Nitration of Tyrosine Hydroxylase by Peroxynitrite and Nitrogen Dioxide: IS NITROTYROSINE FORMATION AN EARLY STEP IN DOPAMINE NEURONAL DAMAGE?

Peroxynitrite and nitrogen dioxide (NO2) are reactive nitrogen species that have been implicated as causal factors in neurodegenerative conditions. Peroxynitrite-induced nitration of tyrosine residues in tyrosine hydroxylase (TH) may even be one of the earliest biochemical events associated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced damage to dopamine neurons. Exposure of TH to peroxynitrite or NO2 results in nitration of tyrosine residues and modification of cysteines in the enzyme as well as inactivation of catalytic activity. Dopamine (DA), its precursor 3,4-dihydroxyphenylalanine, and metabolite 3,4-dihydroxyphenylacetic acid completely block the nitrating effects of peroxynitrite and NO2 on TH but do not relieve the enzyme from inhibition. o-Quinones formed in the reaction of catechols with either peroxynitrite or NO2 react with cysteine residues in TH and inhibit catalytic function. Using direct, real-time evaluation of tyrosine nitration with a green fluorescent protein-TH fusion protein stably expressed in intact cells (also stably expressing the human DA transporter), DA was also found to prevent NO2-induced nitration while leaving TH activity inhibited. These results show that peroxynitrite and NO2 react with DA to form quinones at the expense of tyrosine nitration. Endogenous DA may therefore play an important role in determining how DA neurons are affected by reactive nitrogen species by shifting the balance of their effects away from tyrosine nitration and toward o-quinone formation.

Effect of the P/Al ratio of Al-P-O on the catalytic activity of o -methylation of catechol with methanol

Al-P-O catalysts with different P/Al ratios from 0 to 2.0 were synthesized by conventional precipitation method. The effect of P/Al ratio on the textural and surface properties, and the catalytic activity in the reaction of catechol with methanol were studied by XRD, IR, BET and TPD methods. At P/Al<1.0, the samples were mixtures of aluminium phosphate and amorphous alumina. With increasing P/Al ratio, crystalline AlPO4 and NH4AlP2O7 phases were formed and the surface area of the samples decreased. The catalytic activities for the O-methylation of catechol with methanol have a correlation with the acid amounts. Guaiacol was obtained as a major product and the highest guaiacol yield of ca. 45% was obtained from the sample with P/Al=1.