Oxidation Of 2-naphthol Research Articles

Development of Ti4O7 reactive electrochemical membrane and electrochemical oxidation of naphthols in aqueous solution

Naphthols (NAPs), commonly used phenolic compounds, have significant impact on environmental risk and human health, necessitating advanced treatment methods for their degradation. In this study, a Ti4O7 reactive electrochemical membrane (REM) was developed for the electrochemical oxidation of NAPs. The Ti4O7 REM presented a porosity of 42.18 ± 2.3% and a median pore diameter of 1.21 µm. High permeability (846 LMH bar−1) was achieved at relatively low transmembrane pressure and resulted in a convection-enhanced rate constant for Fe (CN)64- oxidation of 1.7 × 10−4 m/s. The increase in current density and decrease in plate spacing had a positive influence on NAPs degradation. The TOC removal efficiencies of 1-naphthol (1-NAP) and 2-naphthol (2-NAP) were 68.6% and 63.5%, respectively at the current density of 6 mA/cm2 and plate spacing of 10 mm. Additionally, quantum chemical calculation using density functional theory (DFT) was employed to identify the active sites of NAPs through atom charge and frontier electron density (FED) calculations. Results showed that C14 and C10 were identified as the active sites for 1-NAP, while C9 and C13 were the active sites for 2-NAP. Hydroxyl radical and sulfate radical produced on the electrode surface were the main oxidants for NAPs degradation during the electro-oxidation process. The degradation pathway included hydroxylation, oxygenation, decarbonylation, and ring-open processes, which was in agreement with the theoretical calculations. Furthermore, the quantitative structure-activity relationship (QSAR) predictive model was used to assess the toxicity changes during the electrochemical oxidation process of NAPs, suggesting that the toxicity of intermediates increased at the beginning and significantly reduced at the end. This comprehensive study provides practical and theoretical insights into the application of electrochemical oxidation technique for the reduction of refractory compounds in wastewater.

Comparative study on the removal of 1- naphthol and 2-naphthol by ferrate (VI): Kinetics, reaction mechanisms and theoretical calculations

In this study, the oxidation of 1-naphthol (1-NAP) and 2-naphthol (2-NAP) by Fe(VI) was investigated. The impacts of operating factors were investigated through a series of kinetic experiments, including Fe(VI) dosages, pH and coexisting ions (Ca2+, Mg2+, Cu2+, Fe3+, Cl−, SO42−, NO3− and CO32−). Almost 100% elimination of both 1-NAP and 2-NAP could be achieved within 300 s at pH 9.0 and 25 °C. Cu2+ could significantly improve the degradation efficiency of 1-NAP and 2-NAP, but the impacts of other ions were negligible. The liquid chromatography-mass spectrometry was used to identify the transformation products of 1-NAP and 2-NAP in Fe(VI) system, and the degradation pathways were proposed accordingly. Electron transfer mediated polymerization reaction was the dominant transformation pathway in the elimination of NAP by Fe(VI) oxidation. After 300 s of oxidation, heptamers and hexamers were found as the final coupling products during the removal of 1-NAP and 2-NAP, respectively. Theoretical calculations demonstrated that the hydrogen abstraction and electron transfer reaction would easily occur at the hydroxyl groups of 1-NAP and 2-NAP, producing NAP phenoxy radicals for subsequent coupling reaction. Moreover, since the electron transfer reactions between Fe(VI) and NAP molecules were barrierless and could occur spontaneously, the theoretical calculation results also confirmed the priority of coupling reaction in Fe(VI) system. This work indicated that the Fe(VI) oxidation was an effective way for removing naphthol, which may help us understand the reaction mechanism between phenolic compounds with Fe(VI).

(Digital Presentation) Biocatalytic Synthesis of Chiral Compounds in Microemulsions Using Electrode-Driven Enzyme Activation

Biocatalysis in bicontinuous microemulsions is a promising approach for synthetic routes to regio- and stereoselective and efficient synthetic processes. Redox enzymes such as peroxidases and monooxygenases can be attached to surfaces for biocatalysis and operated in low toxicity microemulsions to enhance the dissolution of non-polar reactants, but still provide a water rich environment for the enzyme catalysis resulting in high product yield and chiral products. Here we report a new hybrid electrocatalyst system for biocatalysis using a synthetic Cu-polymer catalyst deposited on an electrode and cross-linked films of poly(L-lysine) (PLL) and redox enzymes horseradish peroxidase (HRP) and cytochrome P450 (Cyt P450) in films on oxidized pyrolytic graphite (PG) electrodes or carboxylate functionalized magnetic particles. Enzymes in these catalytic films are activated by O2 conversion to H2O2 by the Cu polymer. In microemulsions, enzyme reactions occur in a water-rich film environment with delivery of non-polar reactants from the oil-rich regions of the microemulsion. Reactions can be achieved that cannot be run in water due to lack of reactants solubility. Rotating-disk voltammetry (RDV) was used to assess catalytic activity of cross-linked enzyme/PLL films in the presence of H2O2. Activity of cross-linked HRP on magnetic particles was similar to that of 3 mg/mL of free HRP, and these HRP-beads can be used for synthesis up to 95 °C. Oxidation of 2-naphthol by HRP/PLL coated magnetic particles in microemulsions resulted in (R)- and (S)-1,1’-Bi-2-naphthol with chiral ratio determined by chiral HPLC. High product yields of oxidation products were achieved at 80 °C than 20 °C, with product analysis suggesting increasing catalytic efficiency and selectivity at higher temperatures. Additional chiral HRP reactions will be described, and cross-linked Cytochrome P450s are also being explored for stereoselective oxidation and hydroxylation of substrates including styrene, ethyl benzene and 1-tetralone.

Synthesis of the bioactive fungal natural product daldiquinone

We report the first total synthesis of the biologically active fungal natural product daldiquinone (5), which was accomplished with a longest linear sequence of 8 steps in 41% overall yield. The construction of the unsymmetrical binaphthalene core was realized by a Suzuki-Miyaura cross-coupling in 88% yield on gram scale. Oxidation of naphthol 17 with IBX afforded the key naphthoquinone intermediate 18 in high yield (92%).

Switching of Electron Transport Direction from the Long Axis to Short Axis in a Radial SnO2(Head)-Rutile TiO2 Nanorod(Tail) Heteromesocrystal Photocatalyst.

Heteroepitaxial growth of rutile TiO2 nanorods from SnO2 seeds yielded radial heteromesocrystals consisting of SnO2(head) and rutile TiO2 nanorod(tail) with the SnO2(head) oriented toward the center (TiO2-NR//SnO2 HEMCs). Iron oxide clusters were formed on the surface by the chemisorption-calcination technique. The FeOx-surface modification gives rise to drastic increases in the photocatalytic activity for aerobic oxidation of 2-naphthol under irradiation of UV and visible light. As a 2D-model for 3D-TiO2-NR//SnO2 HEMC, electrochemical measurements were performed for the rutile TiO2-NR array formed on a fluorine-doped tin oxide (SnO2:F) electrode. The results showed that the FeOx clusters possess electrocatalytic activity for a multielectron oxygen reduction reaction, and the high photocurrent of the electrode is remarkably reduced by the FeOx-surface modification. Consequently, the striking photocatalytic activity of FeOx/TiO2-NR//SnO2 HEMCs was ascribable to the switching of the electron transport direction necessary for the charge separation from the long axis of the TiO2 NR to the short axis.

Chirally modified cobalt-vanadate grafted on battery waste derived layered reduced graphene oxide for enantioselective photooxidation of 2-naphthol: Asymmetric induction through non-covalent interaction

The cobalt oxide-vanadium oxide (Co3O4-V2O5) combined with reduced graphene oxide (rGO) having band gap of ∼ 3.3 eV appeared as a suitable photocatalyst for selective oxidation of 2-naphthol to BINOL. C2-symmetric BINOL was achieved with good yield using hydrogen peroxide as the oxidant under UV-light irradiation. The same catalyst was chirally modified with cinchonidine and a newly synthesized chiral Schiff base ligand having a sigma-hole center. The strong interaction of the chiral modifiers with the cobalt-vanadium oxide was truly evident from various spectroscopic studies and DFT calculations. The chirally modified mixed metal oxide transformed the oxidative CC coupling reaction with high enantioselectivity. High enantiomeric excess upto 92 % of R-BINOL was obtained in acetonitrile solvent and hydrogen peroxide as the oxidant. A significant achievement was the formation of S-BINOL in the case of the cinchonidine modified catalyst and R-BINOL with the Schiff base ligand anchored chiral catalyst. The UV-light induced catalytic reaction was found to involve hydroxyl radical as the active reactive species. The spin trapping ESR and fluorescence experiment provided relevant evidence for the formation of such species through photodecomposition of hydrogen peroxide on the catalyst surface. The chiral induction to the resultant product was found to induce through supramolecular interaction like OH…π, H…Br interaction. The presence of sigma hole center was believed to play significant role in naphtholate ion recognition during the catalytic cycle.

Fe(III) superoxide radicals in halloysite nanotubes for visible-light-assisted benzyl alcohol oxidation and oxidative C[sbnd]C coupling of 2-naphthol

Selective oxidation of benzyl alcohols to aldehydes and 2-naphthol to BINOL was achieved by activation of molecular oxygen (O2) and hydrogen peroxide (H2O2) over an iron-oxide catalyst embedded in halloysite nanotube. Electron spin resonance spectroscopy (ESR), Raman and in situ FTIR spectroscopic analysis provided direct evidence for the involvement of superoxide radical bound FeIII species in the oxidation reaction. Both the analysis suggested the end-on binding of superoxide radical with FeIII-centre. The stability of such radical bound FeIII-species in halloysite nanotube was analyzed through density functional theory (DFT) calculations. Results suggested that end-on (η1) binding was favourable by 13.5 kcal/ mol than the side-on (η2) binding mode. The formation of such reactive species was believed to play the crucial role in bringing the high selectivity in the catalytic oxidation of benzyl alcohol and oxidative CC coupling of 2-naphthol. UV–Vis spectroscopic studies on the oxidation of benzyl alcohol suggested for the initial adsorption of substrate molecule on the catalyst surface followed by its interaction with FeIII -superoxide/hydroperoxide species generated upon photoirradiation with visible light in presence of O2. The presence of a suitable band gap ∼2.14 eV enabled the catalyst to catalyze the reaction under visible light irradiation. Both the reactions (benzyl alcohol and 2-naphthol oxidation) were tested in presence of both O2 and H2O2 as oxidants at ambient temperature. The influence of different parameters like rate of oxygen flow, amount of peroxide, nature of solvent, and catalyst amount on the conversion and selectivity of the reactions were studied to understand their role in the catalytic reactions. Successful oxidation of 2-naphthol with H2O2 as oxidant was a real success to overcome the limitations associated with this reaction using H2O2 as oxidant.

Nonenzymatic Electrochemical Sensor with Ratiometric Signal Output for Selective Determination of Superoxide Anion in Rat Brain.

There is still an urgent need to develop reliable analytical methods of O2•- in vivo for deeply elucidating the roles of O2•- playing in the brain. Herein, a nonenzymatic electrochemical sensor with ratiometric signal output was developed for an in vivo analysis of O2•- in the rat brain. Diphenylphosphonate-2-naphthol ester (ND) was designed and synthesized as a specific recognition molecule for the selective determination of O2•-. An anodic peak ascribed to the oxidation of 2-naphthol was generated via the nucleophilic substitution between ND and O2•- and was increased with the increasing concentration of O2•-. Meanwhile, the inner reference of methylene blue (MB) was co-assembled at the electrode surface to enhance the determination accuracy of O2•-. The anodic peak current ratio between 2-naphthol and MB exhibited a good linear relationship with the concentration of O2•- from 2 to 200 μM. Because of the stable molecule character of ND and its specific reaction with O2•-, the developed electrochemical sensor demonstrated excellent selectivity toward various potential interferences in the brain and good stability even after storage for 7 days. Accordingly, the present electrochemical sensor with high selectivity, high stability, and high accuracy was successfully exploited in monitoring the levels of O2•- in the rat brain and that of the diabetic model followed by cerebral ischemia.

Anchoring Zn-phthalocyanines in the pore matrices of UiO-67 to improve highly the photocatalytic oxidation efficiency

Metallophthalocyanines (MPcs) with unique photoelectronic properties are a class of very promising photosensitizers for highly efficient photocatalysis; however, their photocatalytic applications are heavily frustrated by the strong π-π self-aggregation issue. We report herein a partial ligand substitution strategy to imbed MPcs in the pore matrices of metal-organic frameworks (MOFs), which could significantly improve the photocatalytic efficiency of MPcs by prohibiting their cofacial self-aggregation. We successfully incorporate ZnPc moieties into the pore matrices of MOF UiO-67 by partially replacing the pristine 4,4′-biphenyldicarboxylate (BPDC) ligands with four-branched ZnPc ligands, in which the ZnPc photosensitizers are easily accessed to reactant molecules in photocatalysis by taking the advantages of porous MOF UiO-67. The ZnPc-incorporated MOF UiO-67-ZnPc demonstrates high photocatalytic efficiency and selectivity in aerobic oxidation of naphthols to produce highly value-added naphthoquinones with high photoactivity, stability and broad substrate applicability under visible light irradiation, which is much superior to its molecular counterpart.

Gold nanoparticle supported on mesoporous vanadium oxide for photo-oxidation of 2-naphthol with hydrogen peroxide and aerobic oxidation of benzyl alcohols

Vanadium oxide supported gold nanocatalysts designated as AuVOx was found to be highly efficient for photocatalytic oxidation of benzyl alcohol and 2-naphthol. The photocatalytic ability of the AuVOx catalyst towards the selective oxidation of 2-naphthol to BINOL was found to be dependent on the nature of the support. The selectivity of the reaction was found to be significantly altered on hybridization with multi-walled carbon nanotubes (AuVOx-MWCNTs). The well-resolved surface plasmon resonance (SPR) band originated from the gold nanoparticles (Au-NPs) on the vanadium oxides support helped in stimulating the photo-oxidation of benzyl alcohol to benzaldehyde and 2-naphthol to BINOL with almost 100% selectivity. The most notable achievement using the AuVOx and AuVOx-MWCNTs catalyst was in the successful photo-oxidation of 2-naphthol to BINOL in presence of hydrogen peroxide (H2O2). The photo-activity of the material and the creation of oxygen defect sites participated in the photochemical processes were estimated from photoluminescence analysis and ESR study. The photochemical reaction was supposed to proceed via superoxide radical generation favored by the oxygen defect sites.

One-Pot Synthesis of 4-Carboalkoxy-Substituted Benzo[h]coumarins from α- and β-Naphthols and Their Excited-State Properties.

One-pot synthesis has been developed for 4-carboethoxybenzo[h]coumarins starting from α-/β-naphthols. Accordingly, diverse 4-carboethoxybenzocoumarins can be synthesized in moderate-to-excellent (31–75%) isolated yields. The synthesis involves initial oxidation of naphthols to the intermediary 1,2-naphthoquinones with 2-iodoxybenzoic acid followed by a cascade of reactions, namely, Wittig olefination, Michael addition, β-elimination, and cyclization. Furthermore, we have comprehensively investigated the excited-state properties of differently substituted 4-carboalkoxybenzo[h]coumarins. It is shown that they exhibit low to high fluorescence quantum yields (1–36%) and excited-state lifetimes (ca. 1–7 ns) depending on the substitution pattern and solvent employed.

Synergetic mediation of reduced graphene oxide and Cu(II) on the oxidation of 2-naphthol in water

Reduced graphene oxide (rGO) is one of the most widely used carbon nanomaterials. When it is released into the environment, rGO can markedly affect the transformation of many pollutants, and change their fate and risk. In this work, the synergetic effects of rGO and Cu(II) on the oxidation of 2-naphthol were examined in water in the dark. It was found that the coexistence of rGO and Cu(II) significantly promoted the oxidation of 2-naphthol. Corresponding products were identified as the coupling oligomers of 2-naphthol (dimer, trimer and tetramer) and hydroxylated compounds (OH-2-naphthol, OH-dimer, di–OH–dimer and naphthoquinone derivatives). In the oxidation reaction, rGO played dual roles, i.e. adsorbent and electron-transfer mediator. rGO firstly adsorbed Cu(II) and 2-naphthol on its surface, and then transferred electrons from 2-naphthol to Cu(II) to yield 2-naphthol radicals and Cu(I). 2-Naphthol radicals coupled to each other to form different oligomers of 2-naphthol. Cu(I) was re-oxidized back to Cu(II) by dissolved oxygen, which sustained the continuous oxidation of 2-naphthol. During the autoxidation of Cu(I), reactive oxygen species were generated, which further reacted with 2-naphthol to form hydroxylated products. These findings provide new insights into the risk assessment of rGO and 2-naphthol in aquatic environments.

Combination of Aryl Diselenides/Hydrogen Peroxide and Carbon‐Nanotube/Rhodium Nanohybrids for Naphthol Oxidation: An Efficient Route towards Trypanocidal Quinones

This work reports a combination of aryl diselenides/hydrogen peroxide and carbon-nanotube (CNT)/rhodium nanohybrids (RhCNT) for naphthol oxidation towards the synthesis of 1,4-naphthoquinones and evaluation of their relevant trypanocidal activity. Under a combination of (PhSe)2 /H2 O2 in the presence of O2 in iPrOH/hexane, several benzenoid (A-ring)-substituted quinones were prepared in moderate to high yields. We also studied the contribution of RhCNT as co-catalyst in this process and, in some cases, yields were improved. This method provides an efficient and versatile alternative for preparing A-ring-modified naphthoquinonoid compounds with relevant biological profile.

Selective oxidation of 2-naphthol to 2-hydroxy-1,4-naphthoquinone with hydrogen peroxide catalyzed by 5,10,15,20-tetrakis(p-sulfonatophenyl)porphinatomanganese(III) chloride in aqueous solution.

2-Naphthol has been selectively oxidized to 2-hydroxy-1,4-naphthoquinone (HNQ, Lawsone) with hydrogen peroxide in presence of 5,10,15,20-tetrakis-(p-sulfonatophenyl)porphinatomanganese (III) chloride as catalyst in alkaline aqueous solution. The catalytic oxidation afforded 2-hydroxy-1,4-naphthoquinone in high yield (95%). The effect of reaction parameters on the catalytic activity and the yield of HNQ have been investigated. UV–vis spectral analysis during oxidation reaction indicated that oxomanganese intermediate O=Mn(IV)TPPSCl was the active species in the oxidation reaction.

One-pot multistep synthesis of bipolar carbazolo-phenazines: Hydrogen bond control of Diels-Alder cycloaddition and application for fluoride sensing

Access to novel bipolar carbazolo-phenazines is demonstrated by one-pot IBX-initiated multistep cascade, which involves oxidation of 2-naphthols to 1,2-naphthoquinones, Diels-Alder cycloaddition, aerial dehydroaromatization and cyclocondensation. With unprotected dienic indolylacrylates, NH⋯O hydrogen bonding in the transition state controls the product selectivity almost exclusively in favor of Diels-Alder cycloaddition over the competing Michael addition. The utility of one of the carbazolo-phenzines as applied to selective naked-eye sensing of fluoride is demonstrated.

O-Iodoxybenzoic Acid-Initiated One-Pot Synthesis of 4-Arylthio-1,2-naphthoquinones, 4-Arylthio-1,2-diacetoxynaphthalenes, and 5-Arylthio-/5-Aminobenzo[a]phenazines.

1,2-Naphthoquiones and their derivatives constitute an important category of compounds of relevance in pharmaceutical and material chemistry. It is shown that 1,2-naphthoquinones generated by o-iodoxybenzoic acid-mediated oxidation of 2-naphthols can be subjected to a cascade of reactions, namely oxidation, Michael addition, reduction, acetylation, and cyclocondensation, in the same pot to afford diverse 4-arylthio-1,2-naphthoquinones 2, 4-arylthio-1,2-diacetoxynaphthalenes 3, and 5-arylthio-/5-aminobenzo[a]phenazines 4 in very good isolated yields. The multistep single-pot synthesis occurs smoothly in DMF at rt.

Amplified thrombin aptasensor based on alkaline phosphatase and hemin/G-quadruplex-catalyzed oxidation of 1-naphthol.

An alkaline phosphatase (ALP)-based biosensor can in situ generate an electroactive product by enzymatic hydrolysis of inactive substrates. To obtain a higher signal-to-background ratio, a chemical redox cycling signal-amplified strategy based on the addition of a strong reducing agent has often be applied in the construction of ALP-based biosensors. However, the strong reducing agent not only affects the activity of ALP but also readily reacts with dissolved oxygen, leading to inaccurate results. In this work, a new signal-amplified strategy for a thrombin (TB) aptasensor based on the catalytic oxidation of ALP-generated products, 1-naphthol (NP), using hemin/G-quadruplex DNAzymes was reported. We implemented gold-nanoparticle-decorated zinc oxide nanoflowers (Au-ZnO) as the matrix for immobilizing ALP and TB aptamer (TBA) and then labeled it with hemin to form hemin/G-quadruplex/ALP/Au-ZnO bioconjugates (TBA II bioconjugates). Through a "sandwich" reaction, TBA II bioconjugates were captured on the electrode surface. The amplified signal was carried out in two steps: (i) an ALP-catalyzed inactive substrate, 1-naphthyl phosphate (NPP), in situ produces NP on the surface of the electrode; (ii) on the one hand, NP as a new reactant could be directly electrooxidized and generated an electrochemical signal, but, on the other hand, NP could be oxidized by hemin/G-quadruplex in the presence of H2O2, resulting in amplification of the electrochemical signal. The proposed TB aptasensor achieved a linear range of 1 pM to 30 nM with a detection limit of 0.37 pM (defined as S/N = 3).

Removal of naphthols and analogues by the combined use of an oxidoreductase polyphenol oxidase and a biopolymer chitosan from aqueous solutions

In this study, the combined use of an amino group-containing polymer chitosan and an oxidoreductase polyphenol oxidase (PPO) was applied to the removal of naphthols and dihydroxynaphthalenes (DHNs) from aqueous solutions. The process parameters, such as the pH value, temperature and enzyme dose, were discussed for PPO-catalysed oxidation of 1-naphthol. The optimum conditions of enzymatic oxidation of 1-naphthol were determined to be pH 8.0 and 40 °C. Under the optimum conditions, PPO-catalysed oxidation of 1-naphthol increased with an increase in the enzyme dose. Quinone derivatives enzymatically generated were chemisorbed on chitosan beads and the initial velocity of PPO-catalysed oxidation increased with an increase in the amount of added chitosan beads. A specific initial velocity of 0.0675 μmol/U·min was obtained in the PPO concentration range below 200 U/cm3 and 1-naphthol was completely removed within 24 h by quinone adsorption on chitosan beads (0.20 cm3/cm3) at a PPO concentration of 100 U/cm3. The removal time was shortened by increasing the enzyme dose or the amount of added chitosan beads. 2-Naphthol was also completely removed at an initial concentration of 0.05 mM or less by prolonging the reaction time, since PPO-catalysed oxidation of 2-naphthol was much slower than that of 1-naphthol. In addition, this procedure was also applied to the removal of DHNs. These results revealed that the procedure constructed in this study was an effective technique to remove naphthols and DHNs from the aqueous medium.

Oxidative coupling of 2-naphthol by zeolite-Y supported homo and heterometallic trinuclear acetate clusters

Trinuclear metal-oxo cluster supported on zeolite-Y is found to be efficient catalyst for oxidation of 2-naphthol to BINOL with high turn over frequency.

Effects of rhamnolipid biosurfactant JBR425 and synthetic surfactant Surfynol465 on the peroxidase-catalyzed oxidation of 2-naphthol

The kinetics of the recombinant Coprinus cinereus peroxidase-catalyzed 2-naphthol oxidation was investigated in the presence of rhamnolipid biosurfactant JBR425 and synthetic surfactant Surfynol465 at pH 5.5 and 25°C, with concentrations of (bio)surfactants both less than critical micelle concentrations (CMC) and larger than CMC. It was shown that monomers of JBR425 as well as monomers of Surfynol465 had an enhancing effect on the conversion of 2-naphthol in dose response manner and did not influence the initial rate of 2-naphthol oxidation. The results were accounted by a scheme, which contains a stadium of enzyme inhibition by oligomeric 2-naphthol oxidation products. The action of the biosurfactant's (or synthetic surfactant's) monomers was explained by avoidance of the enzyme active center clothing with oligomers. Similar results have demonstrated the potential of rhamnolipid biosurfactant JBR425 due to its biodegradability. When biosurfactants' concentrations are larger than CMC, (bio)surfactants have an opposite effect on the oxidation of 2-naphthol by peroxidase.