Showing papers on "Quinone published in 2013"
TL;DR: It was found that the ductile S-Radel membrane, which has a similar aromatic backbone structure to the most-studied polyaromatic VRFB membranes that have shown high performance, became brittle and discolored after 3 days of immersion in 1.7 M V(V) + 3.3 M H2SO4 solution at 40 °C.
Abstract: Insight into the degradation mechanisms of aromatic proton conducting membrane separators for vanadium redox flow batteries (VRFBs) is urgently needed for the development of long lifetime VRFBs. Other than in-cell observations of performance degradation, there is little fundamental evidence on the specific degradation pathways of aromatic ion exchange membranes for VRFBs. Herein we investigated a sulfonated Radel® membrane (S-Radel) as the degradation target to study the degradation mechanism of aromatic polymers by V(V) (or generally V5+) oxidation. It was found that the ductile S-Radel membrane, which has a similar aromatic backbone structure to the most-studied polyaromatic VRFB membranes that have shown high performance, became brittle and discolored after 3 days of immersion in 1.7 M V(V) + 3.3 M H2SO4 solution at 40 °C. The membrane's intrinsic viscosity was reduced to about half of its original value after this exposure to V(V) while the ion exchange capacity did not change. In addition to chain scission, it was found that –OH groups were introduced to the backbone of S-Radel as the major degradation product. Quinone groups were also observed at 1677 cm−1 in FTIR measurements. While the V(V) species in VRFBs is usually denoted as VO2+, V(V)O in VOCl3 was found to not have degradation activity for S-Radel. Therefore, we hypothesized that there were other reactive forms of V(V) species that first attacked the S-Radel by incorporating hydroxyl groups into the polymer's aromatic backbone, followed by the oxidation of these hydroxyl groups to quinone functionalities through a redox mechanism.
130 citations
TL;DR: An iron-catalyzed cross-coupling reaction of electron-deficient heterocycles and quinone with organoboron species via innate C-H functionalization is reported and its application for the synthesis of anticancer marine pyrazine alkaloid botryllazine A.
Abstract: Here, we report an iron-catalyzed cross-coupling reaction of electron-deficient heterocycles and quinone with organoboron species via innate C–H functionalization. Iron(II) acetylacetonate along with oxidant (K2S2O8) and phase-transfer catalyst (TBAB) under open flask conditions efficiently catalyzed the cross-coupling of pyrazine with arylboronic acids and gave monoarylated products in good to excellent yields. Optimized conditions also worked for other heterocylces such as quinoxalines, pyridines, quinoline, and isoquinoline as well as quinones. In addition, we demonstrated as a first example its application for the synthesis of anticancer marine pyrazine alkaloid botryllazine A.
97 citations
TL;DR: The results showed that the phenolic monomers firstly turned into quinone intermediates by laccase catalysis, and through further oxidation, the intermediates formed covalent bonds.
Abstract: Enzymatic polymerization of phenolic compounds (catechol, resorcinol, and hydroquinone) was carried out using laccase. The mechanism of polymerization and the structures of the polymers were evaluated in terms of UV–Vis and Fourier transform infrared spectroscopy. The molecular weights of the produced polyphenols were determined with GPC. The results showed that the phenolic monomers firstly turned into quinone intermediates by laccase catalysis. Through further oxidation, the intermediates formed covalent bonds. Finally, catechol units were linked together with ether bonds, and both resorcinol and hydroquinone units were linked together with C-C bonds. The number-average molecular weights of the polyphenols ranged from 1,000 to 1,400 Da (corresponding to the degree of polymerization that varied from 10 to 12) with a lower polydispersity value of about 1.10, showing selective polymerization of phenolic compounds catalyzed by laccase.
97 citations
TL;DR: These pathways provide a structure-based description of the quinone-mediated proton transfer responsible for generation of the transmembrane electrochemical potential gradient in oxygenic photosynthesis.
Abstract: As much as two-thirds of the proton gradient used for transmembrane free energy storage in oxygenic photosynthesis is generated by the cytochrome b6f complex. The proton uptake pathway from the electrochemically negative (n) aqueous phase to the n-side quinone binding site of the complex, and a probable route for proton exit to the positive phase resulting from quinol oxidation, are defined in a 2.70-A crystal structure and in structures with quinone analog inhibitors at 3.07 A (tridecyl-stigmatellin) and 3.25-A (2-nonyl-4-hydroxyquinoline N-oxide) resolution. The simplest n-side proton pathway extends from the aqueous phase via Asp20 and Arg207 (cytochrome b6 subunit) to quinone bound axially to heme cn. On the positive side, the heme-proximal Glu78 (subunit IV), which accepts protons from plastosemiquinone, defines a route for H+ transfer to the aqueous phase. These pathways provide a structure-based description of the quinone-mediated proton transfer responsible for generation of the transmembrane electrochemical potential gradient in oxygenic photosynthesis.
90 citations
TL;DR: The present method is operationally simple, scalable, does not require prefunctionalization of the heterocycle or quinone, and can tolerate a wide variety of functional groups in the coupling partners.
83 citations
TL;DR: In this paper, an electron-rich CpNi N-heterocyclic carbene (NHC) with quinoid ligand motifs was used for tetrahydroquinaldine (TQ) dehydrogenation.
Abstract: We now report the electrocatalytic dehydrogenation of tetrahydroquinaldine by an electron-rich CpNi N-heterocyclic carbene (NHC) with quinoid ligand motifs and explore the effects of quinone additives on CpNi compounds without quinoid NHC ligands. Our CpNi(NHC) catalyst exhibits dehydrogenative electrocatalytic activity and demonstrates that a molecular catalyst precursor can be viable in the electrode-driven (H+ + e−) release step of “virtual hydrogen storage”.
67 citations
TL;DR: The development of highly enantioselective arylation of encarbamates to give α-amino-β-aryl ethers wherein quinone imine ketals act as functionalized aromatic ring surrogate and chiral β-aryl amines and α-aryl esters is succeeded.
Abstract: The synthetic utility of quinone imine ketals in the context of asymmetric catalysis was disclosed for the first time. By expanding the utility of chiral Bronsted acid catalysis to the electrophilic activation of quinone imine ketals, we succeeded in the development of highly enantioselective arylation of encarbamates to give α-amino-β-aryl ethers wherein quinone imine ketals act as functionalized aromatic ring surrogate. Further transformations of the products were also examined to establish procedures to provide chiral β-aryl amines and α-aryl esters.
65 citations
TL;DR: Assessment of the catalytic role of the oxidoreductase laccase in the binding of sulfamethazine to Leonardite humic acid and to four synthetic humic acids shows that binding to soil organic matter (SOM) is an important process governing the fate, bioactivity, and extractability of sulfonamides in soils.
Abstract: Sulfonamide antibiotics form stable covalent bonds with quinone moieties in organic matter via nucleophilic addition reactions. In this work, we combined analytical electrochemistry with trace anal...
62 citations
TL;DR: PFPDA possesses excellent photostability and exhibits no cytotoxicity, which makes it a good fluorescent material for pH sensing and cell imaging and can also be used for autophagy imaging of HeLa cells with good selectivity.
Abstract: A dopamine-modified conjugated polymer PFPDA is synthesized and characterized. At low pH, dopamine exists in its hydroquinone form and lacks the ability to quench fluorescence. At high pH, the proportion of the quinone form of dopamine increases due to its autooxidation, and efficient intramolecular electron transfer from the polymer main chain to quinone occurs, resulting in the quenching of the fluorescence of PFPDA. Thus, PFPDA exhibits a fluorescence “turn-on” response at low pH. PFPDA possesses excellent photostability and exhibits no cytotoxicity, which makes it a good fluorescent material for pH sensing and cell imaging. A light-induced hydroxyl anion emitter, MGCB, is also used to change the pH of the solution and thus regulate the fluorescence of PFPDA via remote control under light irradiation. Because the cytoplasm becomes acidic when cell autophagy occurs, PFPDA can also be used for autophagy imaging of HeLa cells with good selectivity.
59 citations
TL;DR: The reactivity of the arylboronic acids/esters and the inhibition or facilitation of QM formation can now be predictably adjusted, important as some applications may benefit and others may be limited by QM generation.
Abstract: A series of arylboronic esters containing different aromatic substituents and various benzylic leaving groups (Br or N(+)Me3Br(-)) have been synthesized. The substituent effects on their reactivity with H2O2 and formation of quinone methide (QM) have been investigated. NMR spectroscopy and ethyl vinyl ether (EVE) trapping experiments were used to determine the reaction mechanism and QM formation, respectively. QMs were not generated during oxidative cleavage of the boronic esters but by subsequent transformation of the phenol products under physiological conditions. The oxidative deboronation is facilitated by electron-withdrawing substituents, such as aromatic F, NO2, or benzylic N(+)Me3Br(-), whereas electron-donating substituents or a better leaving group favor QM generation. Compounds containing an aromatic CH3 or OMe group, or a good leaving group (Br), efficiently generate QMs under physiological conditions. Finally, a quantitative relationship between the structure and activity has been established for the arylboronic esters by using a Hammett plot. The reactivity of the arylboronic acids/esters and the inhibition or facilitation of QM formation can now be predictably adjusted. This adjustment is important as some applications may benefit and others may be limited by QM generation.
45 citations
TL;DR: In this paper, the authors present the synthesis of poly(pyrrol-3-ylhydroquinone) (PPyQ), a polypyrrole derivative with pending hydroquinone groups for investigation of the use of a conducting polymer to immobilize redox active quinone units.
Abstract: While various organic molecules have been suggested as environmentally friendly alternatives to inorganic electrode materials for lithium ion batteries, most of them suffer from slow kinetics as well as capacity fading due to dissolution. Herein we present the synthesis of poly(pyrrol-3-ylhydroquinone) (PPyQ), a polypyrrole (PPy) derivative with pending hydroquinone groups, for investigation of the use of a conducting polymer to immobilize redox active quinone units. This strategy eliminates dissolution of the active material while also increasing the conductivity. The quinone pending groups in PPyQ cycle reversibly in the potential region where the polymer backbone is conducting and chemically stable. In situ spectroelectrochemistry on PPyQ films reveals UV/vis transitions inherent to PPy, as well as quinone centered transitions, allowing detailed investigation of the interplay between the polymer doping process and the quinone redox conversion. Intriguingly, it is found that the charging of the PPy back...
TL;DR: A multiwalled carbon nanotube-modified gold electrode surface-bound electrochemical oxidation of PYR to a highly redox-active surface-confined quinone derivative (PYRO) at an applied potential of 1 V versus Ag/AgCl in pH 7 phosphate buffer solution has been demonstrated in this work.
Abstract: Pyrene (PYR) is a rigid, carcinogenic, unreactive, and nonelectrooxidizable compound. A multiwalled carbon nanotube (MWCNT)-modified gold electrode surface-bound electrochemical oxidation of PYR to a highly redox-active surface-confined quinone derivative (PYRO) at an applied potential of 1 V versus Ag/AgCl in pH 7 phosphate buffer solution has been demonstrated in this work. Among various carbon nanomaterials examined, the pristine MWCNT-modified gold electrode showed effective electrochemical oxidation of the PYR. The MWCNT’s graphite impurity promotes the electrochemical oxidation reaction. Physicochemical and electrochemical characterizations of MWCNT@PYRO by Raman spectroscopy, FT-IR, X-ray photoelectron spectroscopy, and GC-MS reveal the presence of PYRO as pyrene–tetrone within the modified electrode. The quinone position of PYRO was identified as ortho-directing by an elegantly designed ortho-isomer-selective complexation reaction with copper ion as an MWCNT@PYRO-Cu2+/1+-modified electrode. Finall...
TL;DR: It is demonstrated that Capsaicin and structurally similar analogues are converted to reactive intermediates by certain P450 enzymes, which may partially explain conflicting reports related to the cytotoxic, pro-carcinogenic, and chemoprotective effects of capsaicinoids in different cells and/or organ systems.
Abstract: This study characterized electrophilic and radical products derived from the metabolism of capsaicin by cytochrome P450 and peroxidase enzymes. Multiple glutathione and β-mercaptoethanol conjugates (a.k.a., adducts), derived from the trapping of quinone methide and quinone intermediates of capsaicin, its analogue nonivamide, and O-demethylated and aromatic hydroxylated metabolites thereof, were produced by human liver microsomes and individual recombinant human P450 enzymes. Conjugates derived from concomitant dehydrogenation of the alkyl terminus of capsaicin were also characterized. Modifications to the 4-OH substituent of the vanilloid ring of capsaicinoids largely prevented the formation of electrophilic intermediates, consistent with the proposed structures and mechanisms of formation for the various conjugates. 5,5'-Dicapsaicin, presumably arising from the bimolecular coupling of free radical intermediates was also characterized. Finally, the analysis of hepatic glutathione conjugates and urinary N-acetylcysteine conjugates from mice dosed with capsaicin confirmed the formation of glutathione conjugates of O-demethylated quinone methide and 5-OH-capsaicin in vivo. These data demonstrated that capsaicin and structurally similar analogues are converted to reactive intermediates by certain P450 enzymes, which may partially explain conflicting reports related to the cytotoxic, pro-carcinogenic, and chemoprotective effects of capsaicinoids in different cells and/or organ systems.
TL;DR: In this paper, a black pearl (BP) carbon powder was chemically modified with chloroanthraquinone groups by spontaneous reduction of 1-amino, 5-chloroanthrasquinone with the aim of determining the quinone content of the modified carbon.
Abstract: Black Pearls (BP) carbon powder was chemically modified with chloroanthraquinone groups by spontaneous reduction of 1-amino, 5-chloroanthraquinone with the aim of determining the quinone content of the modified carbon. This information is essential to determine the increase of capacitance associated to the grafted quinone molecules. The capacitance of pristine carbon electrode was doubled due to the presence of the grafted electroactive molecules. The modified BP powder was characterized by thermogravimetric and elemental analyses. The modified powder was also used to fabricate composite electrodes that were characterized by electrochemistry to determine the loading of electroactive quinone molecules. The presence of the chlorine atom on the anthraquinone moiety allows an estimation of the loading from elemental analysis, which is in relatively good agreement with the value estimated by electrochemistry.
TL;DR: In this article, a binuclear CoIIICoII (1) and another cyclic trinuclear Co IIICo II2 (2) complexes based on hydroxyl rich Schiff base ligands are synthesized and structurally characterized by X-ray crystallography.
TL;DR: The antifungal evaluation of twenty seven simple and heterocycle-fused prenyl-1,4-naphthoquinones and 1, 4-anthracenediones was performed in vitro against human pathogenic yeasts and filamentous fungi, and time-kill curves determined for the most potent compounds showed their fungistatic mode of action similar to that of itraconazole.
TL;DR: A general synthesis of bridged isoxazolidines from a double hetero-Michael addition of N-substituted hydroxylamines to quinone monoketals has been developed and the various functionalities in the isoxAZolidine products allow facile derivatization.
TL;DR: Analysis of the small molecule byproducts of DNA scission supports the conclusion that cleavage occurs via H-atom abstraction from the sugar moieties, consistent with a PCET mechanism.
Abstract: Visible light irradiation of a ruthenium(II) quinone-containing complex, [(phen)2Ru(phendione)]2+ (12+), where phendione = 1,10-phenanthroline-5,6-dione, leads to DNA cleavage in an oxygen independent manner. A combination of NMR analyses, transient absorption spectroscopy, and fluorescence measurements in water and acetonitrile reveal that complex 12+ must be hydrated at the quinone functionality, giving [(phen)2Ru(phenH2O)]2+ (1H2O2+, where phenH2O = 1,10-phenanthroline-6-one-5-diol), in order to access a long-lived 3MLCThydrate state (τ ∼ 360 ns in H2O) which is responsible for DNA cleavage. In effect, hydration at one of the carbonyl functions effectively eliminates the low-energy 3MLCTSQ state (RuIII phen-semiquinone radical anion) as the predominant nonradiative decay pathway. This 3MLCTSQ state is very short-lived (<1 ns) as expected from the energy gap law for nonradiative decay,(1) and too short-lived to be the photoactive species. The resulting excited state in 1H2O2+* has photophysical properti...
TL;DR: The relevance of the anion-π interaction in the enzymatic mechanism for SQR is demonstrated by analyzing the X-ray structures of SQRs available in the Protein Data Bank and using DFT calculations.
Abstract: Sulfide:quinone oxidoreductase (SQR) is a flavin-dependent enzyme that plays a physiological role in two important processes. First, it is responsible for sulfide detoxification by oxidizing sulfide ions (S(2-) and HS(-)) to elementary sulfur and the electrons are first transferred to flavin adenine dinucleotide (FAD), which in turn passes them to the quinone pool in the membrane. Second, in sulfidotrophic bacteria, SQRs play a key role in the sulfide-dependent respiration and anaerobic photosynthesis, deriving energy for their growth from reduced sulfur. Two mechanisms of action for SQR have been proposed: first, nucleophilic attack of a Cys residue on the C4 of FAD, and second, an alternate anionic radical mechanism by direct electron transfer from Cys to the isoalloxazine ring of FAD. Both mechanisms involve a common anionic intermediate that it is stabilized by a relevant anion-π interaction and its previous formation (from HS(-) and Cys-S-S-Cys) is also facilitated by reducing the transition-state barrier, owing to an interaction that involves the π system of FAD. By analyzing the X-ray structures of SQRs available in the Protein Data Bank (PDB) and using DFT calculations, we demonstrate the relevance of the anion-π interaction in the enzymatic mechanism.
TL;DR: In this article, the electrochemistry of a series of substituted isoindole-4,7-diones (IIDs) was investigated and three new IID derivatives were synthesized and characterized by various electrochemical and spectroscopic techniques.
Abstract: Quinone derivatives have been proposed as active components in lithium ion battery (LIB) electrode materials. In this work the electrochemistry of a series of substituted isoindole-4,7-diones (IIDs) was investigated. Three new IID derivatives were synthesized and characterized by various electrochemical and spectroscopic techniques. Polymerization was attempted to achieve a conducting polymer with redox active quinone side groups, which would be advantageous in a LIB application. A combination of in situ spectroelectrochemical measurements and density functional theory (DFT) calculations was used to investigate the proton coupled redox reactions of the IIDs. Results from a previous computational study of the IIDs were compared with experimental data here, and the agreement was very good. The energy of the spectroscopic transitions in the UV and in the visible region showed different correlation with redox potential and quinone substituent in the series of IIDs. This behavior was rationalized by examinatio...
TL;DR: Simultaneous binding of two quinones enhances catalytic efficiency of the final electron transfer step in the Na+-NQR, providing the first direct experimental evidence of simultaneous quinone binding with relevance for the catalytic mechanism.
TL;DR: This is the first Fischer-type indole synthesis using an aliphatic hydrazine as the nitrogen source and a quinone monoketal as a masked benzene ring and the feasibility of this method relies on the initial formation of alkylaryldiazene 5 from a 1,2addition/dehydration sequence.
Abstract: The indole ring system is one of the most ubiquitous heterocycles in nature. Many indole-containing natural products show a wide scope of biological activities, in particular because they bind to many receptors with high affinity. Since Baeyer s first synthesis of indole from oxindole in 1866 (indigo!isatin!oxindole!indole), numerous methods for the synthesis of indoles have been reported. One of the most efficient and widely employed syntheses is the Fischer indolization discovered in 1883. Compared with other indole syntheses, the importance of Fischer indolization lies in its simplicity and convenience, that is, formation of a critical C C bond to an unactivated aromatic carbon through a [3,3] sigmatropic rearrangement of enolizable Narylhydrazones. After more than a century of development, the Fischer indole synthesis remains a reliable and versatile method for the preparation of a variety of indole natural products and medicinal compounds. Many new variations have been developed in recent years. Most recently, the first catalytic asymmetric version of Fischer indole synthesis was reported by the group of List. Although the Fischer indole synthesis is widely used, several disadvantages still remain. The classical Fischer indole synthesis starts with arylhydrazines, which are generally made either from anilines through diazonium salts, or from aryl halides through transitionmetal-mediated coupling reactions. These processes involve the use of aniline precursors and toxic reagents (nitrous acid, stannous chloride, etc.) and potentially explosive diazonium intermediates, or expensive transition metals. We report herein a novel variation of the Fischer indolization involving a one-pot condensation of quinone monoketals with aliphatic hydrazines (Scheme 1). To the best of our knowledge, this is the first Fischer-type indole synthesis using an aliphatic hydrazine as the nitrogen source and a quinone monoketal as a masked benzene ring. We envisioned that condensation of quinone monoketal 1 and aliphatic hydrazine 2 would ultimately lead to an indole via alkylaryldiazene 5 and arylhydrazone intermediate 6, as illustrated in Scheme 2. The feasibility of this method relies on the initial formation of alkylaryldiazene 5 from a 1,2addition/dehydration sequence. It should be noted that there has been no report on the synthesis of alkylaryldiazenes 5 from quinone derivatives and aliphatic hydrazines, although arylaryldiazenes (azobenzenes) have been synthesized from condensations of arylhydrazines with quinones, quinols, quinone monoketals, and quinone bisketals. There is a single report on the condensation of an aliphatic hydrazine (N,N-dimethylhydrazine) with naphthoquinone monoketal, which, however, gave a 1,4-addition product in high yield. Therefore, our first object was to test the practicality of the Scheme 1. Strategies for the synthesis of indoles.
TL;DR: An I2-induced 1,3-dipolar cycloaddition reaction has been developed for the synthesis of benzo[f]isoindole-1, 3-dicarboxylates from quinones and N-substituted amino esters, which have been identified in natural products exhibiting important biological activities.
Abstract: An I2-induced 1,3-dipolar cycloaddition reaction has been developed for the synthesis of benzo[f]isoindole-1,3-dicarboxylates from quinones and N-substituted amino esters. The reaction proceeds in good to excellent yields in one step from 3 equiv of amino ester to react with the quinone structure. The utility of this transformation has been highlighted by its use for the construction of benzo[f]isoindole-1,3-dicarboxylates, which have been identified in natural products exhibiting important biological activities.
TL;DR: It was demonstrated that the dichloromethane extract of Physalis pubescens L. (DEPP) had weak potential quinone reductase (QR) inducing activity, but an UPLC-ESI-MS method with glutathione as the substrate revealed that the DEPP had electrophiles (with an α,β-unsaturated ketone moiety).
TL;DR: It is found that the radical form of the carbon-centered quinone ketoxy radical adduct with a recently developed spin-trapping agent BMPO can not only be directly detected and identified using HPLC/high resolution MS, but can also be isolated and purified using semi-preparative HPLC, enabling direct observation of its clean 6-line ESR signal.
TL;DR: In this article, the reactivity of the structurally related molecule dopamine on well-ordered platinum surfaces has been investigated and shown to be electrochemically active and reveals interesting adsorption phenomena at low potentials (0.15-0.25 V vs RHE), sensitive to the single crystal orientation.
TL;DR: In this article, a simple strategy for the sensitive detection of hydroquinone (H2Q) using fluorescent silver nanoclusters (AgNCs) has been developed, in which the fluorescence of AgNCs was quenched efficiently by phenolic compounds.
Abstract: In this paper, a simple strategy for the sensitive detection of hydroquinone (H2Q) using fluorescent silver nanoclusters (AgNCs) has been developed. In the presence of H2O2 and peroxidase, the fluorescence of AgNCs was quenched efficiently by phenolic compounds. The mechanism inherent in the fluorescence quenching could be mainly ascribed to the formation of the quinone intermediates via enzyme-catalyzed oxidation of phenolic compounds. Combined with the high specificity of the enzyme, the method could determine phenolic compounds with a linear relationship ranging from 8.0 × 10−8 to 3.2 × 10−6 mol L−1 and a detection limit of 10−8 mol L−1. In the case of phenols, the presented sensor may serve as a comparative empirical method for the evaluation of contamination.
TL;DR: Electrochemical oxidation of three representative wine polyphenols in the presence of sulfur dioxide in a model wine solution and the mechanism was proposed to be an ECEC mechanism was confirmed by digital simulation of cyclic voltammograms.
Abstract: Electrochemical oxidation of three representative wine polyphenols (catechin, caffeic acid, and quercetin) in the presence of sulfur dioxide in a model wine solution (pH = 3.3) was investigated. The oxidation was undertaken using chronoamperometry at a rotating glassy carbon rod electrode, and the reaction products were characterized by HPLC-MS. The mechanism of electrochemical oxidation of polyphenols in the presence of sulfur dioxide was proposed to be an ECEC mechanism. The polyphenols first underwent a one-electron oxidation to a semiquinone radical, which can be reduced back to the original polyphenol by sulfur dioxide, or further oxidized to the quinone form. In the cases of caffeic acid and catechin, the quinone combined with sulfur dioxide and produced new derivatives. The quercetin quinone underwent further chemical transformations, producing several new compounds. The proposed mechanisms were confirmed by digital simulation of cyclic voltammograms.
TL;DR: In this article, cyclic voltammetry and impedance spectroscopy were used to understand the kinetic limitations of 1-amino-anthraquinone (1-AAN) electrochemistry.
TL;DR: In this paper, the second-order rate constants of substituted ethyl arylacetates with quinone methides and structurally related diethyl benzyl benylidenemalonates have been studied in DMSO.