- The Formation of 1,4-Quinones by Oxovanadium(IV)-Complexes Catalyzed Aerobic Oxygenation of Fused Aromatic Compounds
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In the presence of a catalytic amount of oxovanadium(IV) complexes coordinated with 1,3-diketone ligands, fused aromatic compounds such as naphthalenes and naphthol derivatives are smoothly oxygenated into the corresponding 1,4-naphthoquinones by combined use of molecular oxygen and crotonaldehyde under an atmospheric pressure.
- Takai, Toshihiro,Hata, Eiichiro,Mukaiyama, Teruaki
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- 2-Pyridyldimethylsilyl Group as a Removable Hydrophilic Group in Aqueous Organic Reactions: Formation of Molecular Aggregates and Dramatic Rate Enhancement in Diels-Alder Reactions
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A novel methodology for aqueous organic reactions utilizing a 2-pyridyldimethylsilyl (2-PyMe2Si) group as a removable hydrophilic group has been developed. It was found that 1,3-dienes bearing the 2-PyMe2Si group form molecular aggregates in water when 1.0 equivalent of HCl was added, as evidenced by dynamic light-scattering experiments. The Diels-Alder reaction of 2-PyMe2Si-substituted 1,3-dienes with various dienophiles took place in water at room temperature. The Diels-Alder reaction in organic solvents (Et2O/toluene) under the same reaction temperature and time gave the cycloadduct in much lower yield, indicating the dramatic rate acceleration in water. The removal of the 2-PyMe2Si group was accomplished by desilylation, oxidation, and electrophilic substitution.
- Itami, Kenichiro,Nokami, Toshiki,Yoshida, Jun-Ichi
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- Copper(i)-based oxidation of polycyclic aromatic hydrocarbons and product elucidation using vacuum ultraviolet spectroscopy and theoretical spectral calculations
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Copper(i) complexes supported by fluorinated 1,3,5-triazapentadienyl ligands have been used as catalysts for the oxidation of anthracene, naphthalene, and pyrene to the corresponding quinones, using H2O2 as an oxidant under mild conditions without an acid co-catalyst. Gas chromatography-vacuum ultraviolet spectroscopy (GC-VUV) combined with time-dependent density functional theory theoretical computations of absorption spectra was demonstrated as a new and useful tool-set for unknown determination in complex reaction mixtures, especially when standards are not available for spectral comparisons and product mixtures involve closely related isomers. The anthracene has been converted to 9,10-anthraquinone in quantitative yield using this copper catalyzed process. The oxidation of naphthalene afforded 1,4-naphthoquinone as the major product, and 1-naphthol and 2-naphthol as minor products. The pyrene oxidation resulted in 4,5-, 1,6-, and 1,8-pyrenequinones, among other products. The X-ray crystal structure of [N{(CF3)C(C6F5)N}2]CuNCCH3 is also reported.
- Ponduru, Tharun T.,Qiu, Changling,Mao, James X.,Leghissa, Allegra,Smuts, Jonathan,Schug, Kevin A.,Dias, H. V. Rasika
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- Sodium hypochlorite/Dowex 1X8-200: An effective oxidant for the oxidation of aromatic amines to quinones
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Polymer supported hypochlorite ion is a useful oxidant for the oxidation of aromatic amines to the corresponding quinones.
- Hashemi, Mohammed M.,Beni, Yousef A.
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- Influence of the sulfinyl group on the chemoselectivity and π-facial selectivity of diels-alder reactions of (S)-2-(p Tolylsulfinyl)-1,4-benzoquinone
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Diels-Alder reactions of (S)-2-(p-tolylsulfmyl)-1,4-benzoquinone (1a) with cyclic (cyclopentadiene and cyelohexadiene) and acyclic dienes (1-[(trimethylsilyl)oxy]-1,3-butadiene and trans-piperylene) under different thermal and Lewis acid conditions are reported. Chemoselectivity (reactions on C2-C3 versus C5-C6 double bonds) is mainly related to the cyclic (on C5-C6) or acyclic (on C2-C3) structure of the diene. The high π-facial selectivity observed could be controlled by choosing adequate experimental conditions.
- Carreno, M. Carmen,Garcia Ruano, José L.,Toledo, Miguel A.,Urbano, Antonio,Remor, Cynthia Z.,Stefani, Valter,Fischer, Jean
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- A novel process for selective Ruthenium-Catalyzed oxidation of naphthalenes and phenols
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Arenes are selectively oxidized to the corresponding quinones employing ruthenium(2,2′,6′:2″-terpyridine)(2,6-pyridinedicarboxylate) [Ru(tpy)(pydic] as catalyst and hydrogen peroxide as the terminal oxidant. Applying alkylated naphthalenes and phenols, benzo- and naphthoquinones are obtained in up to 93% yield. The industrially interesting oxidation of 2-methylnaphthalene gave 74% of the corresponding quinones and 60% of menadione (vitamin K3). 2,3,5-Trimethylbenzoquinone which constitutes the key intermediate for vitamin E is obtained in 83% yield.
- Wienhoefer, Gerrit,Schroeder, Kristin,Moeller, Konstanze,Junge, Kathrin,Beller, Matthias
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- Preparation and photocatalytic activity of WO3-MWCNT nanocomposite for degradation of naphthalene under visible light irradiation
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In this study, a WO3-multiwalled carbon nanotube nanocomposite has been prepared for the first time by in situ liquid phase process. The prepared nanocomposite was used for photodegradation of dilute solution of naphthalene under visible light irradiation. Based on our results, comparing photocatalytic activity of WO3 nanoparticle with WO3-multiwalled carbon nanotube nanocomposite showed that the photodegradation of naphthalene is negligible by using pure WO3 nanoparticles while, composition of WO3 nanoparticles with multi walled carbon nanotubes could improve significantly their photocatalytic activity under visible light. Due to its high electrical conductivity, carbon nanotube can transfer photogenerated electron on its surface and in this way decreases electron-hole recombination rate and increases photocatalytic activity. After the reaction, the irradiated solution has been analyzed by gas chromatography and mass spectrometry techniques for identification of the naphthalene photodegradation intermediates and products. 1-Naphthol, 1,4-naphthalenedione and 1,2-benzendicarboxilic acid have been determined as intermediates and based on these intermediates a suitable mechanism for photodegradation of naphthalene was suggested.
- Farhadian, Mousa,Sangpour, Parvaneh,Hosseinzadeh, Ghader
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- Exploiting photooxygenations mediated by porphyrinoid photocatalysts under continuous flow conditions
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Photooxygenation reactions are a powerful synthetic tool to produce oxidized organic compounds; however, these reactions often exhibit experimental limitations including the production of complex mixtures that hinder desired product isolation and scale-up. Herein, we present a photocatalysed protocol under continuous flow conditions using a simple home built photoreactor and porphyrinoids as photocatalysts. Reaction conditions, long-term experiments, and scope demonstrate a protocol that is cost-effective, safe, reproducible and robust, thus allowing the production of relevant substituted naphthoquinones with interest in natural product synthesis and biological activity.
- De Oliveira, Kleber T.,Miller, L. Zane,McQuade, D. Tyler
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- The Oxidation of Methylbenzenes and Naphthalenes to Quinones with H2O2 in the Presence of Palladium Catalyst
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Methylbenzenes and naphthalenes were oxidized to quinones with aqueous(60percent) H2O2 in acetic acid in the presence of a 0.24 wtpercent Pd(II)-sulfonated polystyrene type resin.The selectivities to quinones were higher in naphthalenes than in methylbenzenes.Among the naphthalenes used, 2-methylnaphthalene, 2,3-dimethylnaphthalene, and 2,6-dimethylnaphthalene gave 1,4-quinones in good yields (50-64percent).The increase in the reaction temperature increased the selectivity to quinones from 40percent at 20 deg C to 70percent at 70 deg C.
- Yamaguchi, Satoru,Inoue, Masami,Enomoto, Saburo
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- Direct photooxidation and xanthene-sensitized oxidation of naphthols: Quantum yields and mechanism
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The photoinduced oxidation of 1-naphthol to 1,4-naphthoquinone and of 5-hydroxy-1-naphthol to 5-hydroxy-1,4-naphthoquinone was studied by steady-state and time-resolved techniques. The direct photooxidation of naphthols in methanol or water takes place by reaction of the naphoxyl radical ( ·ONaph) with the superoxide ion radical (O2 ·-), the latter of which results from the reaction of the solvated electron with oxygen after photoionization. The sensitized oxidation takes place by energy transfer from the xanthene triplet state to oxygen. From the two oxygen atoms, which are consumed, one is incorporated into the naphthol molecule giving naphthoquinone and the second gives rise to water. The effects of eosin, erythrosin, and rose bengal in aqueous solution, pH, and the oxygen and naphthol concentrations were studied. The quantum yield of the photosensitized transformation was determined, which increases with the naphthol concentration and is largest at pH > 10. The quantum yield of oxygen uptake is similar. The pathway involving singlet molecular oxygen is suggested to operate for the three sensitizers. The alternative pathway via electron transfer from the naphthol to the xanthene triplet state and subsequent reaction of ·ONaph with O2·-, the latter of which is formed by scavenging of the xanthene radical anion by oxygen, does also contribute.
- Oelgemoeller, Michael,Mattay, Jochen,Goerner, Helmut
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- Ceric ammonium nitrate (CAN) as oxidizing or nitrating reagent for organic reactions in ionic liquids
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The reaction of ceric ammonium nitrate, (NH4)2[Ce(NO3)6] or CAN, with naphthalene and 2-methylnaphthalene in the ionic liquid 1-ethyl-3-methylimidazolium triflate showed that the reaction products are strongly d
- Deleersnyder, Karen,Schaltin, Stijn,Fransaer, Jan,Binnemans, Koen,Parac-Vogt, Tatjana N.
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- Polymer incarcerated gold catalyzed aerobic oxidation of hydroquinones and their derivatives
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Polymer-incarcerated gold (PI Au) cluster catalysts mediated aerobic oxidation of hydroquinones and catechols to quinones very efficiently under mild conditions. The characteristic role of water in the reaction system was also observed. Copyright
- Miyamura, Hiroyuki,Shiramizu, Mika,Matsubara, Ryosuke,Kobayashi, Shu
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- One-pot enantioselective synthesis of 1,4-naphthoquinone-derived polycycles through oxidative dearomatization and aminocatalysis
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A synthetic process merging oxidative dearomatization and asymmetric aminocatalysis in a single vessel is reported. The PhI(OAc)2-mediated oxidation of 1,4-dihydroxynaphthalene is followed by a trienamine-mediated Diels-Alder cycloaddition/aldol reaction or a trienamine-mediated Diels-Alder cycloaddition/oxidation sequence depending on the dienal substitution pattern. The polycyclic compounds are obtained in good yields with enantiomeric excesses up to 99%. Additionally, these polycyclic architectures can be synthesized with similar enantioselectivities through an unprecedented one-pot marriage of bodipy-photocatalyzed oxidative dearomatization of 1-naphthol and asymmetric aminocatalysis. A catalytic cycle is suggested to explain the reaction outcome. The asymmetric synthesis of diversely substituted 1,4-naphthoquinone-derived polycycles is described by merging dearomatization and aminocatalysis in a single vessel. The dearomatization step is promoted by PhI(OAc)2 or oxygen in the presence of a bodipy photosensitizer and two products are selectively isolated depending on the dienal substitution.
- Pantaine, Lo?c,Coeffard, Vincent,Moreau, Xavier,Greck, Christine
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- Oxidation of Methoxy- and/or Methyl-Substituted Benzenes and Naphthalenes to Quinones and Phenols by H2O2 in HCOOH
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The oxidation of a number of arenes (methoxybenzenes, methylbenzenes, and naphthalenes) to quinones and phenols by H2O2 in HCOOH has been examined.Methoxybenzenes were much more easily oxidized to p-benzoquinones than methylbenzenes (e.g., 1,3,5-trimethoxybenzene was oxidized to 2,6-dimethoxy-p-benzoquinone in a 75percent yield and 1,2,4-trimethylbenzene to 2,3,5-trimethyl-p-benzoquinone in a 16percent yield).Electron-withdrawing substituents, such as nitro, cyano, and chloro groups, lowered the conversion of reactants and changed the product selectivity from quinones to phenols.Methoxybenzonitriles were oxidized to corresponding phenols in a moder ate yield (e.g., 2,6-dimethoxybenzonitrile to 3-hydroxy-2,6-dimethoxybenzonitrile in a 39percent yield and a 64percent selectivity).
- Orita, Hideo,Shimizu, Masao,Hayakawa, Takashi,Takehira, Katsuomi
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- Intramolecular Reaction Of Nitroxide Radicals With Biradical Intermediates Generated From Aromatic Enediynes
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1,4-Dehydronaphthalene biradicals generated by thermolysis of aromatic enediynes can be trapped with the nitroxide radical TEMPO.The isolated products, however, are not the direct trapping products but 1,4-naphthoquinones resulting from the homolysis of N-O bonds of trapping products.
- Grissom, Janet Wisniewski,Gunawardena, Gamini U.
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- Preparation and Photoisomerization of 2-Formylcinnamaldehyde in Solution
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Naphthalene, in dilute aqueous solution, reacts with ozone to form one or both isomers of 2-formylcinnamaldehyde; an equilibrium mixture of the isomers also results upon irradiation of the E-isomer with long wavelength ultraviolet light.
- Larson, Richard A.,Garrison, Wendy J.,Marley, Karen A.
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- Discovery of juglone and its derivatives as potent SARS-CoV-2 main proteinase inhibitors
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SARS-CoV-2 as a positive-sense single-stranded RNA coronavirus caused the global outbreak of COVID-19. The main protease (Mpro) of the virus as the major enzyme processing viral polyproteins contributed to the replication and transcription of SARS-CoV-2 in host cells, and has been characterized as an attractive target in drug discovery. Herein, a set of 1,4-naphthoquinones with juglone skeleton were prepared and evaluated for the inhibitory efficacy against SARS-CoV-2 Mpro. More than half of the tested naphthoquinones could effectively inhibit the target enzyme with an inhibition rate of more than 90% at the concentration of 10 μM. In the structure-activity relationships (SARs) analysis, the characteristics of substituents and their position on juglone core scaffold were recognized as key ingredients for enzyme inhibitory activity. The most active compound, 2-acetyl-8-methoxy-1,4-naphthoquinone (15), which exhibited much higher potency in enzyme inhibitions than shikonin as the positive control, displayed an IC50 value of 72.07 ± 4.84 nM towards Mpro-mediated hydrolysis of the fluorescently labeled peptide. It fit well into the active site cavity of the enzyme by forming hydrogen bonds with adjacent amino acid residues in molecular docking studies. The results from in vitro antiviral activity evaluation demonstrated that the most potent Mpro inhibitor could significantly suppress the replication of SARS-CoV-2 in Vero E6 cells within the low micromolar concentrations, with its EC50 value of about 4.55 μM. It was non-toxic towards the host Vero E6 cells under tested concentrations. The present research work implied that juglone skeleton could be a primary template for the development of potent Mpro inhibitors.
- Cui, Jiahua,Jia, Jinping
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- Visible-light induced solvent-free photooxygenations of organic substrates by using [60]fullerene-linked silica gels as heterogeneous catalysts and as solid-phase reaction fields
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Novel recyclable heterogeneous catalysts generating singlet-oxygen under visible-light irradiation have been prepared by linking [60]fullerene to amino-functionalized silica gels. The catalysts facilitate various types of photooxygenerations including Diels-Alder reaction, ene reaction, and oxidations of phenol and sulfide in a solid-solvent system and even in a solvent-free system.
- Hino, Tetsuo,Anzai, Takahiro,Kuramoto, Noriyuki
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- The selective oxidation of substituted aromatic hydrocarbons and the observation of uncoupling via redox cycling during naphthalene oxidation by the CYP101B1 system
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The cytochrome P450 monooxygenase enzyme CYP101B1, from Novosphingobium aromaticivorans DSM12444, efficiently and selectively oxidised a range of naphthalene and biphenyl derivatives. Methyl substituted naphthalenes were better substrates than ethylnaphthalenes and naphthalene itself. The highest product formation activity for a singly substituted alkylnaphthalene was obtained with 2-methylnaphthalene. The oxidation of alkylnaphthalenes was regioselective for the benzylic methyl or methine C-H bonds. The products from 1- and 2-ethylnaphthalene oxidation were highly enantioselective with a single stereoisomer being generated in significant excess. The disubstituted substrate, 2,7-dimethylnaphthalene, had a higher product formation activity than either 1- and 2-methylnaphthalene. Methyl substituted biphenyls were also better substrates than biphenyl and had similar biocatalytic parameters to 1-methylnaphthalene. CYP101B1 catalysed oxidation of 2- and 3-methylbiphenyl was selective for attack at the methyl C-H bonds. The exception was the turnover of 4-methylbiphenyl which generated 4′-(4-methylphenyl)phenol as the major product (70%) with 4-biphenylmethanol making up the remainder. The drug molecule diclofenac was also regioselectively oxidised to 4′-hydroxydiclofenac by CYP101B1. The activity of the CYP101B1 system with naphthalene was more complex and the rate of NADH oxidation increased over time but very little product, 1-naphthol, was generated. Addition of samples of 1-naphthol and 2-naphthol and low concentrations of 1,4-naphthoquinone induced rapid NADH oxidation activity in the in vitro turnovers in both the presence and absence of the cytochrome P450 enzyme. Hydrogen peroxide was generated in these reactions in absence of the P450 enzymes demonstrating that the ferredoxin and ferredoxin reductase in combination with quinones from naphthol oxidation and oxygen can undergo redox cycling giving rise to a form of uncoupling of the reducing equivalents.
- Hall, Emma A.,Sarkar, Md Raihan,Bell, Stephen G.
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- Convenient Synthesis of 1,4-Naphthoquinones from Polymethoxynaphthalenes. Oxidative Demethylation with Silver-Catalyzed Ammonium Peroxodisulfate
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The oxidative demethylation of polymethoxynaphthalenes such as 1,4-di, 1,4,5-tri, 1,4,5,8-tetra-, and 1,2,4,5,8-pentamethoxynaphthalenes with silver-catalyzed ammonium peroxodisulfate gave the corresponding 1,4-naphthoquinones in good yield under mild reaction conditions.
- Tanoue, Yasuhiro,Sakata, Kazunori,Hashimoto, Mamoru,Morishita, Shin-ichi,Hamada, Moritsugu
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- Fullerene-coated beads as reusable catalysts
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New heterogeneous catalysts that use oxygen and light to generate singlet oxygen (102) have been prepared. The catalysts facilitate various types of singlet oxygenation reactions including the Ene reaction, the Diels-Alder reaction, and others. The catalysts are made by stirring a heterogeneous mixture of fullerene-C60(dissolved in toluene) with aminomethylated poly(styrene-co-divinylbenzene) beads. Also, catalysts for aqueous photooxidations are made by reacting the initial catalysts with poly(allylamine) to create an outer layer that is more hydrophilic.
- Jensen, Anton W.,Daniels, Coreen
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- Immobilization of a Metal Complex in Y-Zeolite Matrix: Synthesis, X-ray Single-Crystal, and Catalytic Activities of a Copper (Schiff-Base)-Y Zeolite Based Hybrid Catalyst
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A new zeolite-immobilized copper(II) complex catalyst has been prepared by entrapping [CuL] [LH2 = N,N′ -(1,1-dimethylethylene)bis(salicylaldiimine)] on NaY zeolite matrix. The reaction of Cu-NaY and molten LH2 affords a green mass of crude catalyst that upon a treatment with CH3CN gives a gray-colored hybrid catalyst (CuL-NaY). The prepared catalyst has been characterized by IR and UV-vis spectroscopic and EPR spectrometric measurements, TG-DTA analysis, powder X-ray diffraction, and surface-area measurements. To ascertain the structure of the immobilized complex, a single-crystal X-ray diffraction analysis of [CuL] was performed. Spectroscopic measurements showed that the green crude of CuL-NaY contains a penta- or hexa-coordinated copper(II) moiety, while the CuL-NaY catalyst contains a distorted square-planar [CuL] complex moiety. A remarkable catalytic activity of the prepared hybrid catalyst has been observed in oxidation reactions of 1-naphthol and norbornene.
- Saha, Pratap Kumar,Banerjee, Surajit,Saha, Sandip,Mukherjee, Alok Kumar,Sivasanker, Subramanian,Koner, Subratanath
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- Strategies for cleaner oxidations using photochemically generated singlet oxygen in supercritical carbon dioxide
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Photochemically generated singlet oxygen, 1O2, has been reacted with four different substrates in supercritical carbon dioxide. By using fluorous surfactants and a co-solvent to solubilise more polar photosensitisers and reactants respectively, the applicability of the system is greatly enhanced. The Royal Society of Chemistry 2009.
- Han, Xue,Bourne, Richard A.,Poliakoff, Martyn,George, Michael W.
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- Molecular growth of PAH-like systems induced by oxygen species: Experimental and theoretical study of the reaction of naphthalene with HO (2Π3/2), O (3P), and O2 (3Σ - G)
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To assess if reactions with oxygen species can induce a mass increase of polycyclic aromatic hydrocarbons, we exposed naphthalene molecules to an oxidative gas flow containing the radicals H and HO (2Π3/2) and the diradicals O (3P) and O2 (3Σ-g). We observed the formation of 1- and 2-naphtol, 1,4-naphthoquinone, naphthalene-derived cyclic ethers, an ester from ring opening, and ether adducts containing two naphthalene units. We investigated the possible reaction pathways as a function of temperature by density functional calculations. We found that the reactivity is characterized by HO, O and H addition to naphthalene, or by H abstraction from it, with roles depending on temperature. In conclusion, oxygen species can promote, under the experimental conditions, mainly naphthalene oxidation and, to a lesser extent, substantial molecular growth, with an efficiency that the calculations indicate to depend on the system temperature. Future experiments should try to quantify key species to allow defining the relative importance of the various reaction mechanisms uncovered by ab initio calculations.
- Scapinello, Marco,Martini, Luca Matteo,Tosi, Paolo,Maranzana, Andrea,Tonachini, Glauco
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- Exponential Molecular Amplification by H2O2-Mediated Autocatalytic Deprotection of Boronic Ester Probes to Redox Cyclers
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Herein, a new molecular autocatalytic reaction scheme based on a H2O2-mediated deprotection of a boronate ester probe into a redox cycling compound is described, generating an exponential signal gain in the presence of O2 and a reducing agent or enzyme. For such a purpose, new chemosensing probes built around a naphthoquinone/naphthohydroquinone redox-active core, masked by a self-immolative boronic ester protecting group, were designed. With these probes, typical autocatalytic kinetic traces with characteristic lags and exponential phases were obtained by using either UV/Visible or fluorescence optical detection, or by using electrochemical monitoring. Detection of concentrations as low as 0.5 μm H2O2 and 0.5 nm of a naphthoquinone derivative were achieved in a relatively short time (2O2 or redox cycling compounds, or for use as a new building block in the development of more complex chemical reaction networks.
- Pallu, Justine,Rabin, Charlie,Creste, Geordie,Branca, Mathieu,Mavré, Fran?ois,Limoges, Beno?t
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- 2-Geranyl-1,4-naphthoquinone, a possible intermediate of anthraquinones in a Sesamum indicum hairy root culture
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2-Geranyl-1,4-naphthoquinone was isolated from the hairy root culture of Sesamum indicum. The structure was determined to be 2-[(E)-3,7-dimethylocta-2,6- dienyl]-1,4-naphthoquinone on the basis of spectroscopic evidence and chemical synthesis. The production of anthrasesamones A, B and C by the hairy root culture was also confirmed for the first time.
- Furumoto, Toshio,Ohara, Tomoko,Kubo, Tetsuya,Kawanami, Yasuhiro,Fukui, Hiroshi
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- Oxidation of hydroquinones to benzoquinones with hydrogen peroxide using catalytic amount of silver oxide under batch and continuous-flow conditions
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Silver oxide (Ag2O) can be utilized as heterogeneous catalyst in the oxidation of hydroquinones to the corresponding benzoquinones with 30% aq. H2O2. The catalytic properties of Ag2O have been explored in the model reaction of methylhydroquinone with H2O2 performed under batch conditions. Results show that the reaction can be carried out in high yield and selectivity at room temperature under environmentally friendly conditions. The truly heterogeneous catalyst can be recovered by filtration and reused for at least five times, giving the same excellent results (～95% yield, ～98% selectivity). The catalyst can be packed in a tubular reactor and utilized under continuous-flow conditions giving similar good results.
- Derikvand, Fatemeh,Bigi, Franca,Maggi, Raimondo,Piscopo, Calogero Giancarlo,Sartori, Giovanni
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- Copper-mediated addition of ethanolamine affording 2-hydroxymethyl naphtho[2,1-d]oxazoles from 2-naphthols
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A new and mild synthetic approach was presented for the synthesis of naphtho[2,1-d]oxazoles. In the presence of copper (II)-ethanolamine, 2-hydroxymethyl naphtho[2,1-d]oxazoles were one-pot synthesized in moderate to good yields through copper-mediated oxidation of 2-naphthols followed with the addition of ethanolamine in acetonitrile.
- Wang, Xiuzhen,Yang, Baoyun,Li, Rui
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- Chromium(VI) oxide-catalyzed oxidation of arenes with periodic acid
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Chromium(VI) oxide was found to catalyze the oxidation of arenes such as naphthalenes and anthrathene to the corresponding quinones with periodic acid as the terminal oxidant in acetonitrile. 2-Methylnaphthalene was oxidized smoothly to 2-methyl-1,4-naphthoquinone (vitamin K3) by the catalytic system in high yield and regioselectivity.
- Yamazaki, Shigekazu
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- Anodic oxidation of 4-methoxy-1-naphthol
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Anodic oxidation of 4-methoxy-1-naphthol 1 in the presence of nucleophiles provided the corresponding products 8-12 and the dimers 13 and 17 were also produced. The reaction mechanism of the oxidation reaction including the [3+2] cycloaddition was investigated.
- El-Seedi, Hesham R.,Yamamura, Shosuke,Nishiyama, Shigeru
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- Thermolysis of 2-Benzylidenebenzocyclobutenols
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The thermolysis of a series of 2-benzylidenebenzocyclobuten-1-ols has been studied.Whenever comparisons can be made, the rate of opening of the benzocyclobutene ring was slower for these compounds than the corresponding 2-ones.The intermediate vinylallenes underwent a variety of electrocyclization reactions which depended on the nature of the additional substituent at C-1. 10-Benzylideneanthrone and 4-benzylidene-1-tetralones, respectively, were obtained when this substituent was phenyl or vinyl. 1-(Alkynylphenyl)-2-benzylidenebenzocylobuten-1-ols were converted to mixtures of 4-benzylidene-1,4-naphthoquinonemethides, 2,3-dibenzylidene-1-indanones, and 10-phenylbenzofluorenone.
- Bradley, Jean-Claude,Durst, Tony,Williams, A. J.
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- Electron-Transfer Kinetics of Quinones at Solid Electrodes in Aprotic Solvents at Low Temperatures
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Activation paramaters for the electrochemical one-electron reduction of quinones were evaluated at glassy carbon, Au, and Pt electrodes from 170 to 290 K in aprotic solvents (N,N-dimethylformamide and propionitrile) by cyclic voltametry.Systematic differences in the activation parameters among electrode materials were observed.The average of the activation enthalpy was 13 +/- 2 kJ /mol for the glassy arbon electrode, 21 +/- 3 kJ/mol for the Au electrode, and 14 +/- 4 kJ/mol for the Pt electrode in N,n-dimethylformamide, showing that the extent of the interaction between the electrode surface and the reactant is different for each electrode material.The Arrheneus plots for 1,4-benzoquinone curved down only at the glassy carbon electrode in both N,N-dimethylformamide and propionitrile, indicating that it was reduced by a different mechanism at law temperatures (250 K) at the glassy carbon electrode.The experimental techniques and a simple cooling system for low-temperature electrochemistry are also described.
- Nagaoka, Tsutomu,Okazaki, Satoshi
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- Photooxygenations of 1-naphthols: An environmentally friendly access to 1,4-naphthoquinones
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Dye sensitized photooxygenations of 1-naphthols were investigated with soluble and solid-supported sensitizers and moderate to excellent yields of the corresponding 1,4-naphthoquinones were achieved in relatively short irradiation times. The mild and environmentally friendly reaction conditions made this application particularly attractive for 'Green Photochemistry'. Consequently, the photooxygenation of 1,5-dihydroxynaphthalene was studied with non-concentrated and moderately concentrated sunlight and 5-hydroxy-1,4- naphthoquinone (Juglone) was obtained in yields up to 71%.
- Suchard, Oliver,Kane, Ronan,Roe, Bernard J.,Zimmermann, Elmar,Jung, Christian,Waske, Prashant A.,Mattay, Jochen,Oelgem?ller, Michael
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- Bis(trifluoroacetoxyiodo)benzene-induced activation of tert-butyl hydroperoxide for the direct oxyfunctionalization of arenes to quinones
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Various aromatic hydrocarbons were oxidized with bis(trifluoroacetoxyiodo) benzene (PIFA)/tert-butyl hydroperoxide system to afford the corresponding quinones. The reaction conditions and scope have been discussed in detail.
- Catir, Mustafa,Kilic, Hamdullah
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- Homogeneous oxidation of aromatics in nucleus with peracetic acid catalyzed by iron and manganese phthalocyanine complexes
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The reaction of naphthalene and methylnaphthalenes with peracetic acid catalyzed by Mn(III) (1) or Fe(II) (2) octanitrophthalocyanines in CH3CN at 20°C produces 1,4-naphthoquinones with 35-62% yields. The corresponding 2,3-epoxide-1,4-endoperoxides are proposed as intermediate in reaction catalyzed by 1.
- Barkanova, Svetlana V.,Derkacheva, Valentina M.,Dolotova, Olga V.,Li, Vladimir D.,Negrimovsky, Vladimir M.,Kaliya, Oleg L.,Luk'yanets, Eugene A.
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- Characterization of a chemically reactive propranolol metabolite that binds to microsomal proteins of rat liver
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We have characterized a chemically reactive propranolol (PL) metabolite which binds to proteins in rat liver microsomes. During incubation with rat liver microsomes (1 mg of protein) fortified with an NADPH-generating system, 4-hydroxypropranolol (4-OH-PL) quickly disappeared from the reaction medium, but none of the possible metabolite peaks was detected under the high- performance liquid chromatographic conditions used. The consumption of 4-OH- PL depended on microsomes and NADPH. The reaction was not affected by inhibitors of cytochrome P450 or FAD monooxygenase, but was markedly diminished in the presence of cytosol and ascorbic acid. The effect of cytosol was inhibited by potassium cyanide but not by sodium benzoate or dimethyl sulfoxide, and was also not affected by heating at 60 °C for 30 min, suggesting that superoxide (SO) ion was involved in the reaction and that it was blocked by superoxide dismutase (SOD) present in the cytosol. Cu,Zn-SOD, purified from cytosol, effectively mimicked the suppressive effect of cytosol. Incubation of 4-OH-PL in an SO-generating system of xanthine and xanthine oxidase generated 1,4-naphthoquinone (1,4-NQ), which was identified by TLC, HPLC, and GC/MS. 1,4-NQ was also formed in microsomal incubates containing NADPH and small amounts of microsomes (below 0.1 mg of protein). These results indicate that 4-OH-PL is converted by SO, or some reactive oxygen species derived from it, to 1,4-NQ which binds to proteins and is one of the reactive metabolites of PL.
- Narimatsu,Watanabe,Masubuchi,Horie,Kumagai,Cho,Imaoka,Funae,Ishikawa,Suzuki
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Read Online
- μ-oxo-bridged hypervalent iodine(III) compound as an extreme oxidant for aqueous oxidations
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We have found that in aqueous oxidations the -oxo-bridged hypervalent iodine trifluoroacetate reagent 1 {[(PhI(OCOCF]} is generally more reactive than the corresponding monomeric reagent, especially toward phenolic substrates. -Oxo-bridged 1 in aqueous media thus provided dearomatized quinones 3 in excellent yields in most cases compared to conventional phenyliodine(III) diacetate and bis(trifluoroacetate), as a result of the rapid oxidation of both phenols and naphthols 2. Furthermore, the oxidation reactions proceeded even in water using water-soluble -oxo oxidant 1, which has promise for -oxo-bridged reagent 1 to become the favored reagent over hydrophobic phenyliodine(III) diacetate and bis(trifluoroacetate). Georg Thieme Verlag Stuttgart New York.
- Dohi, Toshifumi,Nakae, Tomofumi,Takenaga, Naoko,Uchiyama, Teruyoshi,Fukushima, Kei-Ichiro,Fujioka, Hiromichi,Kita, Yasuyuki
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- Efficient oxidative ipso-fluorination of para-substituted phenols using pyridinium polyhydrogen fluoride in combination with hypervalent iodine(III) reagents
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Diacetoxyiodobenzene (PIDA) and bis(trifluoroacetoxy)iodobenzene (PIFA) in the presence of pyridinium polyhydrogen fluoride (PPHF) are effective for the fluorination of para-substituted phenols to give a variety of 4-fluorocyclohexa-2,5-dienones in a good yield. (R,S)-1,1′-Bi-5,6,7,8- tetrahydro-2-naphthol (and its monoacetate) yields atropoisomeric fluorocyclohexadienones. The 4-substituted carbamate open-chain phenols were readily converted to fluorohydroindolenone and fluorohydroquinolenone derivatives by intramolecular conjugate addition.
- Karam, Omar,Martin-Mingot, Agnès,Jouannetaud, Marie-Paule,Jacquesy, Jean-Claude,Cousson, Alain
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- Long Optical Path Length Thin-Layer Spectroelectrochemistry. Catalytic Oxidation of Hydroquinones by Oxygen at Platinum
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A clean, open-circuited Pt electrode, in the presence of dissolved oxygen, catalyzes the oxidation of hydroquinones in 1 M H2SO4.The oxidation rate is independent of hydroquinone, but dependent upon O2 concentration.If iodine is preadsorbed onto the Pt surface, the catalysis is inhibited, although reversible electron transfer to electrolyze the dissolved hydroquinone is not.
- Gui, Yupeng,Kuwana, Theodore
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- Synthesis, properties and singlet oxygen generation of thiazolidinone double bond linked porphyrin at meso and β-position
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Meso and β-substituted free base and zinc metallated thiazolidinone-porphyrin conjugates were synthesized by one pot four component Knoevenagel condensation by utilizing substituted amines, carbon disulfide, ethyl chloroacetate and porphyrin aldehydes. These newly synthesized conjugates were characterized by IR, 1H NMR, 13C NMR, UV-Vis, fluorescence and HRMS spectroscopy. The singlet oxygen generation behaviors of these porphyrin conjugates were studied and it was observed that these porphyrin conjugates followed type II singlet oxygen. Fluorescence and singlet oxygen quantum yields among meso-substituted (mono-, di, tetra) and β-substituted conjugates were examined. The photocatalytic photooxidation of naphthols and furan by using these new organic photocatalysts were further analysed and it was observed that meso-tetra substituted (Zn3a) and β-substituted (Zn6a) porphyrins are much efficient for generation of singlet oxygen and for photocatalytic photooxidation.
- Ahmad, Sohail,Yadav, Kumar Karitkey,Narang, Uma,Bhattacharya, Soumee,Singh, Sarangthem Joychandra,Chauhan
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- A facile synthesis of naturally occurring binaphthoquinones: Efficient oxidative dimerization of 4-alkoxy-1-naphthols using silver(II) oxide-40% nitric acid
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Oxidation of 4-alkoxy-1-naphthols with AgO-40% HNO3 occurred along with a dimerization to give the corresponding bi-1,4-naphthoquinones. The oxidative dimerization required one hydroxyl group and took place at its ortho position. This reaction was applicable to syntheses of naturally occurring binaphthoquinones, bivitamin K3 and 3,3′-bijuglone.
- Tanoue, Yasuhiro,Sakata, Kazunori,Hashimoto, Mamoru,Morishita, Shin-Ich,Hamada, Moritsugu,Kai, Norihisa,Nagai, Takeshi
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- Oxidative Dearomatization of Phenols and Polycyclic Aromatics with Hydrogen Peroxide Triggered by Heterogeneous Sulfonic Acids
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We report herein a method for the oxidative dearomatization of phenols and bare polycyclic arenes into the corresponding quinoid derivatives using hydrogen peroxide. The reaction is catalyzed by sulfonic acids and best results were achieved using heterogenized species. The best results using phenols were achieved using a hybrid material, namely a perfluorinated polymer functionalized with sulfonic acid groups supported on silica. The dearomatization of polycyclic aromatic hydrocarbons performed better using the polymeric acid catalyst. These methods operate under mild conditions, using mild and benign oxidants and thus minimizing the formation of waste.
- Pancrazzi, Francesco,Maestri, Giovanni,Maggi, Raimondo,Viscardi, Rosanna
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supporting information
p. 5407 - 5414
(2021/10/25)
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- Menadione structure-based novel coronavirus 3CL protease inhibitor
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The invention discloses a menadione derivative capable of resisting novel coronavirus and medical application of the menadione derivative. The structure of the compound is shown as a formula (I), in the formula, R is a hydrogen atom, methyl, acetyl or hydroxyl, and R1 is hydrogen, methoxy, benzyloxy or benzoyloxy. The compound disclosed by the invention can inhibit the 3CL hydrolase of the 2019-nCoV novel coronavirus, and has the activity of resisting the novel coronavirus. In-vitro activity determination experiments show that the enzyme inhibition rate of part of the compounds reaches 90% or above under the concentration of 1 [mu] M, and is significantly superior to that of a positive control drug alkannin. Cell-level toxicity test experiment results show that the toxicity of menadione and the derivative thereof to host normal cells HSF is significantly lower than that of positive drugs alkannin and juglone, and part of the compounds show relatively strong anti-novel coronavirus activity in vitro, and have an important significance for the development of high-efficiency and low-toxicity new anti-novel coronavirus drugs.
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Paragraph 0040-0043
(2021/04/14)
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- Organophotocatalytic Aerobic Oxygenation of Phenols in a Visible-Light Continuous-Flow Photoreactor
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A mild photocatalytic phenol oxygenation enabled by a continuous-flow photoreactor using visible light and pressurized air is described herein. Products for wide-ranging applications, including the synthesis of vitamins, were obtained in high yields by precisely controlling principal process parameters. The reactor design permits low organophotocatalyst loadings to generate singlet oxygen. It is anticipated that the efficient aerobic phenol oxygenation to benzoquinones and p-quinols contributes to sustainable synthesis.
- Wellauer, Jo?l,Miladinov, Dragan,Buchholz, Thomas,Schütz, Jan,Stemmler, René T.,Medlock, Jonathan A.,Bonrath, Werner,Sparr, Christof
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supporting information
p. 9748 - 9752
(2021/05/27)
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- β-Cyclodextrin-conjugated phthalocyanines as water-soluble and recyclable sensitisers for photocatalytic applications
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Two zinc(ii) phthalocyanines substituted with two and four permethylated β-cyclodextrin moieties at the α positions have been synthesised and immobilised on the surface of adamantane-modified silica nanoparticles through host-guest interactions. These molecular and supramolecular systems can catalyse the photooxygenation of 1-naphthol and 2-furoic acid in organic and aqueous media with high conversion efficiency and reaction yield, and photodegradation of 2-chlorophenol in water. Having a higher photostability and recyclability, the supramolecular nanosystems are particularly promising for these photocatalytic applications.
- Chen, Xiao-Fei,Ng, Dennis K. P.
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supporting information
p. 3567 - 3570
(2021/04/14)
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- Zwitterion-induced organic-metal hybrid catalysis in aerobic oxidation
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In many metal catalyses, the traditional strategy of removing chloride ions is to add silver salts via anion exchange to obtain highly active catalysts. Herein, we reported an alternative strategy of removing chloride anions from ruthenium trichloride using an organic [P+-N-] zwitterionic compound via multiple hydrogen bond interactions. The resultant organic-metal hybrid catalytic system has successfully been applied to the aerobic oxidation of alcohols, tetrahydroquinolines, and indolines under mild conditions. The performance of zwitterion is far superior to that of many other common Lewis bases or Br?nsted bases. Mechanistic studies revealed that the zwitterion triggers the dissociation of chloride from ruthenium trichloride via nonclassical hydrogen bond interaction. Preliminary studies show that the zwitterion is applicable to catalytic transfer semi-hydrogenation.
- Hu, Rong-Bin,Lam, Ying-Pong,Ng, Wing-Hin,Wong, Chun-Yuen,Yeung, Ying-Yeung
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p. 3498 - 3506
(2021/04/07)
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- PHOTOOXIDATION OF PHENOLIC COMPOUNDS
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The present invention relates to the photooxidation of phenolic compounds to the respective quinoid compounds using methylene blue as photosensitizer in a solvent mixture of water and alcohols using light of the high wavelength range of the visible spectrum.
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Page/Page column 18
(2021/11/26)
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- Oxidation of Electron-Rich Arenes Using HFIP-UHP System
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The straightforward oxidation of electron-rich arenes, namely, phenols, naphthols, and anisole derivatives, under mild reaction conditions, is described by means of the use of an environmentally benign HFIP-UHP system. The corresponding quinones or hydroxylated arenes were obtained in moderate to good yields.
- Llopis, Natalia,Baeza, Alejandro
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p. 6159 - 6164
(2020/05/20)
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- Manganese(Ⅳ) bis(hydroxo) complex, preparation method thereof, and oxidation method of naphthalene derivative using the same
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The present invention relates to a manganese(IV)-bis(hydroxo) complex, a preparation method thereof, and a method for oxidizing a naphthalene derivative using the same. The complex represented by chemical formula 1: [Mn^IV(L)(OH)_2]^2+ provided in an aspect of the present invention can easily oxidize naphthalene and derivatives thereof, which are known to have low reactivity and be toxic substances, in the presence of an acid, and thus has an effect of converting naphthalene and derivatives thereof to 1,4-naphthoquinone with low toxicity.COPYRIGHT KIPO 2021
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Paragraph 0156-0163
(2020/11/03)
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- Distribution of Spin Density on Phenoxyl Radicals Affects the Selectivity of Aerobic Oxygenation of Phenols
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Phenoxyl radical was generally suggested as the intermediate during copper-catalyzed aerobic oxygenation of phenols. However, the substrate-dependent selectivity has not been well interpreted, due to insufficient characterization of the radical intermediate under reaction conditions. When studying the CuCl-LiCl-catalyzed aerobic phenol oxidation, we obtained EPR spectra of phenoxyl radicals generated by oxidizing phenols with the preactivated catalyst. Upon correlation to the selectivity of benzoquinone, the hyperfine coupling constant of para-site proton (aH, para) was found to be better than the Hammett constant. The catalysis mechanism was studied based on EPR detection and the reaction results of phenoxyl radicals under N2 or O2 atmosphere. It appeared that the chemoselectivity depended on the attack of activated dioxygen on phenoxyl radicals, and the activation of dioxygen by [CunCln+1]- (n = 1, 2, 3) was suggested as the rate-determining step. Understanding of the substrate-dependent selectivity contributed to predicting the chemoselectivity in the aerobic oxidation of phenols.
- Chen, Kaizhou,Du, Renfeng,Fan, Mengtian,Guan, Jun,Jiang, Zheng,Li, Haoran,Lu, Rui,Mei, Bingbao,Wang, Yongtao,Yao, Jia
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- IBX-TfOH mediated oxidation of alcohols to aldehydes and ketones under mild reaction conditions
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An efficient, practical and facile procedure has been developed for the oxidation of primary and secondary alcohols using IBX-TfOH catalytic system in 1,4-dioxane at ambient temperature. The reaction affords quantitative yields of the corresponding carbonyl compounds without the formation of over oxidized products. The present synthetic protocol is compatible with a variety of substrates having arene, heteroarene and alkene functionalities. The developed synthetic protocol can be used for higher scale reactions as evident by the oxidation of alcohol at 1 g scale in higher yields by a simple filtration process.
- Kumar, Kamlesh,Kumar, Prashant,Joshi, Penny,Rawat, Diwan S
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supporting information
(2020/03/04)
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- Bisketene Equivalents as Diels-Alder Dienes
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2,5-Bis(tert-butyldimethylsilyloxy)furans are established as vicinal bisketene equivalents for application as dienes in the Diels-Alder reaction. Cycloaddition with olefinic dienophiles, under exceptionally mild conditions, enables convergent access to highly substituted para-hydroquinones in unprotected form via a one-pot Diels-Alder/ring-opening/tautomerization sequence. The synthesis of para-benzoquinones from acetylenic dienophiles, including benzynes, is also demonstrated, and 2,5-bis(tert-butyldimethylsilyloxy)pyrroles are established as competent dienes for the synthesis of para-iminoquinones. Application in natural product synthesis enables gram-scale access to the neuroprotective agent (±)-indanostatin.
- Dissanayake, Isuru,Hart, Jacob D.,Becroft, Emma C.,Sumby, Christopher J.,Newton, Christopher G.
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supporting information
p. 13328 - 13333
(2020/09/03)
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- Method for continuously synthesizing quinones in tubular reactor and equipment
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The invention belongs to the technical field of synthesis of organic compounds, particularly relates to a method for continuously synthesizing quinones in a tubular reactor and provides equipment usedin the synthesis method. The method comprises following steps: (1), naphthalene or anthraquinones are dissolved in an organic solvent, and a dissolved solution is obtained; (2), the dissolved solution obtained in the step (1) and an electrolyte Ce are pumped into the tubular reactor respectively; (3), the temperature of the reactor is adjusted to be 30-100 DEG C, and materials stay in the tubular reactor for a reaction; (4), after the reaction, a reaction liquid flowing out of the tubular reactor is directly introduced into a filter device, solid naphthoquinones are obtained, washed by deionized water and dried, and a product is obtained. According to the method and the equipment, continuity of feeding, reaction and discharging is realized, and production efficiency is improved.
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Paragraph 0060; 0061; 0062
(2019/04/02)
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- Dearomatization of Electron-Deficient Phenols to ortho-Quinones: Bidentate Nitrogen-Ligated Iodine(V) Reagents
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Despite their broad utility, the synthesis of ortho-quinones remains a significant challenge, in particular, access to electron-deficient derivatives remains an unsolved problem. Reported here is the first general method for the synthesis of electron-deficient ortho-quinones by direct oxidation of phenols. The reaction is enabled by a novel bidentate nitrogen-ligated iodine(V) reagent, a previously unexplored class of compounds which we have termed Bi(N)-HVIs. The reaction is extremely general and proceeds with excellent regioselectivity for the ortho over para isomer. Functionalization of the ortho-quinone products was examined, resulting in a facile one-pot synthesis of catechols, as well as the incorporation of a variety of heteroatom nucleophiles. This method represents the first synthetic application of Bi(N)-HVIs and demonstrates their potential as a platform for the further development of highly reactive, but also highly tunable, I(V) reagents.
- Xiao, Xiao,Greenwood, Nathaniel S.,Wengryniuk, Sarah E.
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supporting information
p. 16181 - 16187
(2019/11/05)
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- Generation of Endocyclic Vinyl Carbene Complexes via Gold-Catalyzed Oxidative Cyclization of Terminal Diynes: Toward Naphthoquinones and Carbazolequinones
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Carbene cascade reactions involving carbene/alkyne metathesis have attracted much attention over the past decades because this chemistry offers great potential to build complicated cyclic molecules. However, the formed vinyl metal carbenoids in these reactions are limited to exocyclic carbenes, and the generation of endocyclic vinyl carbene complexes remains unexplored. Here, we report an unprecedented gold-catalyzed oxidative cyclization of terminal diynes. Importantly, the generation of endocyclic vinyl carbene complexes was involved in this oxidative cyclization, which is distinctively different from previous protocols. This method allows the facile synthesis of various valuable naphthoquinones and carbazolequinones from readily available diynes under exceptionally mild reaction conditions and features a broad substrate scope and wide functional group tolerance. Moreover, theoretical calculations provide further evidence on the divergent selectivity of this cyclization reaction.
- Shu, Chao,Shi, Chong-Yang,Sun, Qing,Zhou, Bo,Li, Tian-You,He, Qiao,Lu, Xin,Liu, Rai-Shung,Ye, Long-Wu
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p. 1019 - 1025
(2019/01/15)
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- Sonochemical Preparation of Dipicolinamide Mn-complexes and Their Application as Catalysts Towards Sono-synthesis of Ketones
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A series of non-heme Mn-complexes has been synthesized by the sonication of manganese (II)chloride and bis-amides (condensation products of 2-picolinic acid and o-phenylenediamines). The Mn-complexes effectively promote the oxidation of unactivated aliphatic and benzylic C─H and N-bearing heterocycles substrates with low catalyst loading using eco-friendly hydrogen peroxide in the presence of acetic acid as additive under ultrasonic irradiation. Chromatographic studies revealed that the corresponding ketones are the only detectable products. Noteworthy, the presence of electron donors in the catalyst structure significantly increased the reaction yields. The substantial lowering of the oxidation reaction yields by adding ionol (2,6-di-tert-butyl-4-methylphenol) as a free radical trap suggesting a free radical reaction pathway.
- Arafa, Wael A. A.
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p. 1403 - 1412
(2019/02/25)
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- Oxidation of Naphthalene with a Manganese(IV) Bis(hydroxo) Complex in the Presence of Acid
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Naphthalene oxidation with metal–oxygen intermediates is a difficult reaction in environmental and biological chemistry. Herein, we report that a MnIV bis(hydroxo) complex, which was fully characterized by various physicochemical methods, such as ESI-MS, UV/Vis, and EPR analysis, X-ray diffraction, and XAS, can be employed for the oxidation of naphthalene in the presence of acid to afford 1,4-naphthoquinone. Redox titration of the MnIV bis(hydroxo) complex gave a one-electron reduction potential of 1.09 V, which is the most positive potential for all reported nonheme MnIV bis(hydroxo) species as well as MnIV oxo analogues. Kinetic studies, including kinetic isotope effect analysis, suggest that the naphthalene oxidation occurs through a rate-determining electron transfer process.
- Jeong, Donghyun,Yan, James J.,Noh, Hyeonju,Hedman, Britt,Hodgson, Keith O.,Solomon, Edward I.,Cho, Jaeheung
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supporting information
p. 7764 - 7768
(2018/06/26)
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- Earth-Abundant Mixed-Metal Catalysts for Hydrocarbon Oxygenation
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The oxygenation of aliphatic and aromatic hydrocarbons using earth-abundant Fe and Cu catalysts and "green" oxidants such as hydrogen peroxide is becoming increasingly important to atom-economical chemical processing. In light of this, we describe that dinuclear CuII complexes of pyrrolic Schiff-base macrocycles, in combination with ferric chloride (FeCl3), catalyze the oxygenation of π-activated benzylic substrates with hydroperoxide oxidants at room temperature and low loadings, representing a novel design in oxidation catalysis. Mass spectrometry and extended X-ray absorption fine structure analysis indicate that a cooperative action between CuII and FeIII occurs, most likely because of the interaction of FeCl3 or FeCl4- with the dinuclear CuII macrocycle. Voltammetric measurements highlight a modulation of both CuII and FeIII redox potentials in this adduct, but electron paramagnetic resonance spectroscopy indicates that any Cu-Fe intermetallic interaction is weak. High ketone/alcohol product ratios, a small reaction constant (Hammett analysis), and small kinetic isotope effect for H-atom abstraction point toward a free-radical reaction. However, the lack of reactivity with cyclohexane, oxidation of 9,10-dihydroanthracene, oxygenation by the hydroperoxide MPPH (radical mechanistic probe), and oxygenation in dinitrogen-purge experiments indicate a metal-based reaction. Through detailed reaction monitoring and associated kinetic modeling, a network of oxidation pathways is proposed that includes "well-disguised" radical chemistry via the formation of metal-associated radical intermediates.
- Pankhurst, James R.,Curcio, Massimiliano,Sproules, Stephen,Lloyd-Jones, Guy C.,Love, Jason B.
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supporting information
p. 5915 - 5928
(2018/05/28)
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- Highly Efficient Catalytic Oxidation of Inert C(sp3)–H Bonds by the Synergistic Effect of Copper Nanoparticles/N-Doped Graphene
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The applicability of Cu is still limited in the heterogeneous catalytic oxidation of C(sp3)–H bonds. This problem was resolved by exploiting the synergistic effect existing between Cu nanoparticles (Cu NPs) and N-doped graphene. We demonstrate a highly efficient, green protocol for the catalytic oxidation of inert C(sp3)–H bonds with only oxygen as the oxidant catalyzed by Cu NPs/N-doped graphene (Cu-N-rGO). The new composite materials were obtained through a very simple one-pot solvothermal process. Remarkably, newly prepared Cu-N-rGO showed 34.5 % conversion and 89.2 % selectivity for the catalytic oxidation of cyclohexane to KA oil [mixture of cyclohexanone (K) and cyclohexanol (A)] in a single cycle and thus exhibited significantly higher efficiency than the N-free Cu catalysts. Cu-N-rGO has good stability because the doped nitrogen atoms allow strong interactions between the Cu species and graphene, so that the conversion and selectivity can be maintained over five runs. The delicate relationship between the Cu NPs and nitrogen was investigated by accurate control of the ratio of nitrogen and Cu in doped graphene. A hypothesized free-radical chain mechanism and a peroxidative oxidation process were proven and explained, and the synergistic effect of the Cu NPs and N-doped graphene in facilitating the oxidation process was also elucidated.
- Sun, Wei,Gao, Lingfeng,Feng, Xue,Sun, Xu,Zheng, Gengxiu
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p. 1121 - 1129
(2018/03/13)
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- Selective C(sp3)?H Aerobic Oxidation Enabled by Decatungstate Photocatalysis in Flow
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A mild and selective C(sp3)?H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C?H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (?)-ambroxide, pregnenolone acetate, (+)-sclareolide, and artemisinin, exemplifies the utility of this new method.
- Laudadio, Gabriele,Govaerts, Sebastian,Wang, Ying,Ravelli, Davide,Koolman, Hannes F.,Fagnoni, Maurizio,Djuric, Stevan W.,No?l, Timothy
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supporting information
p. 4078 - 4082
(2018/03/21)
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- Significant effect of 5,10,15,20-meso-tetraarylporphyrinatoiron(III) chloride/triflate and acidic/neutral/basic imidazolium ionic liquids in catalytic oxidation of phenols
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The influence of acidic, neutral and basic ionic liquids and their binary mixture with dichloromethane on the reactivity of iron(III)porphyrins was investigated during oxidation of phenols with hydrogen peroxide catalysed by 5,10,15,20-tetraarylporphyrinatoiron(III) chloride and 5,10,15,20-tetraarylporphyrinatoiron(III) triflate. The generation of different intermediates of iron(III) porphyrin in different ILs was studied through viscosity, density, UV–Vis and 1H NMR spectroscopy. The heterolytic cleavage efficiency of (TAP)FeIII-OOH and formation of quinone using iron(III)porphyrin (TAP)FeIIICl with Cl atom as an axial ligand, is influenced by the structure of imidazolium moiety and the counteranion following the order [(CH2)4SO3HMIm]CF3COO > [Hmim]CF3COO > [bmim]TFA ?? negligible amount in [bmim]CF3SO3, [Hmim]CF3SO3, [bmim]BF4, [bmim]PF6 and [bmim]Cl. On the other hand, the heterolytic cleavage efficiency of (TAP)FeIII-OOH with iron(III)porphyrin (TAP)FeIIICF3SO3 with triflate as an axial ligand, was found in the following order [(CH2)4SO3HMIm]CF3SO3 > [Hmim]CF3SO3 > [(CH2)4SO3HMIm]CF3COO > [Hmim]CF3COO > [bmim] CF3COO > [bmim]PF6 ≈ [bmim]BF4 ≈ [bmim]CF3SO3, while epoxidation and polymerization were mainly observed in basic and neutral ILs. The reactive intermediates formed by the reaction of monooxygen donors with (TAP)FeIIICl varied with ILs, as (TAP)+?FeIV = O intermediate was dominated in acidic ILs, while (TAP)FeIV = O was formed in neutral ILs and (TAP)FeIII-OO– was formed in basic ILs.
- Ahmad, Sohail,Gautam, Renu,Singhal, Anchal,Chauhan
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p. 292 - 303
(2018/04/10)
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- Synthesis, Characterization, and Reaction of a Both Inter- and Intramolecularly Coordinated Pseudocyclic Iodosylbenzene–Trifluoroacetic Acid Complexes
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An ortho-substituted ether-oxygen-coordinated pseudocyclic iodosylbenzene-trifluoroacetic acid (pcISB-TFA) complex was synthesized and characterized by X-ray crystallographic analysis. TFA suppresses the disproportionation by both coordination of the oxygen atom to the iodine(III) center through secondary bonding and by hydrogen bonding to the oxygen anion. This bench-stable reagent is highly soluble in common organic solvents and reacts with various organic substrates under mild reaction conditions to give the corresponding products in good yields.
- Yudasaka, Masaharu,Maruyama, Toshifumi,Yamaguchi, Eiji,Tada, Norihiro,Itoh, Akichika
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p. 550 - 556
(2018/02/09)
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- Selective Cleavage of Inert Aryl C-N Bonds in N-Aryl Amides
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A highly selective, IBX-promoted reaction has been developed for the oxidative cleavage of inert C(aryl)-N bonds on secondary amides while leaving the C(carbonyl)-N bond unchanged. This metal-free reaction proceeds under mild conditions (HFIP/H2O, 25 °C), providing facile access to various useful primary amides, some of which would be otherwise unattainable using conventional aminolysis and hydrolysis approaches.
- Zhang, Zhiguo,Zheng, Dan,Wan, Yameng,Zhang, Guisheng,Bi, Jingjing,Liu, Qingfeng,Liu, Tongxin,Shi, Lei
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p. 1369 - 1376
(2018/02/09)
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- Generation and Confinement of Long-Lived N-Oxyl Radical and Its Photocatalysis
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Generation of controllable carbon radical under the assistance of N-oxyl radical is an efficient method for the activation of C-H bonds in hydrocarbons. We herein report that irradiation of α-Fe2O3 and N-hydroxyphthalimide (NHPI) under 455 nm light generates phthalimide-N-oxyl radical (PINO), which after being formed by oxidation with holes, is confined on α-Fe2O3 surface. The half-life time of the confined radical reaches 22 s as measured by in situ electron paramagnetic resonance (EPR) after the light being turned off. This allows the long-lived N-oxyl radical to abstract the H from C-H bond to form a carbon radical that reacts with molecular oxygen to form R3C-OO· species, decomposition of which leads to oxygenated products.
- Zhang, Chaofeng,Huang, Zhipeng,Lu, Jianmin,Luo, Nengchao,Wang, Feng
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p. 2032 - 2035
(2018/02/19)
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- A new synthetic route to 5,6,11,12-tetraarylethynyltetracenes
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A new synthetic route to 5,6,11,12-tetrakis(arylethynyl)tetracenes, π-extended rubrenes, was developed via [4 + 2] cycloadditions of dialkynylisobenzofuran and 1,4-naphthoquinone. Introduction of arylethynyl groups by double nucleophilic additions to tetracenequinone gave sterically congested (arylethynyl)tetracenes after reductive aromatization. The photophysical properties of the newly prepared π-conjugated molecules are also evaluated.
- Kitamura, Kei,Asahina, Kenta,Nagai, Yusaku,Zhang, Keshu,Nomura, Shogo,Tanaka, Katsunori,Hamura, Toshiyuki
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supporting information
p. 9143 - 9146
(2019/01/03)
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- One-pot oxidation of aromatic and cyclic hydrocarbons using the Au (III) and Pd (II) catalyst under microwave irradiation
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We report here in highly efficient one-pot catalytic system which utilizes in situ generated sodium ferrate for the oxidation of aromatic and cyclic hydrocarbons in the presence of Au (III) and Pd (II) metal ions catalyst under ecofriendly green synthetic method. Results of these studies revealed that Au (III) catalytic system gave higher yield as compared with Pd (II) catalytic system because of the higher electrode potential of Au(III) than Pd(II). All compounds were characterized by infrared and NMR spectral analysis. Copyright
- Srivastava, Manish,Srivastava, Anamika,Goyal, Ashu,Mishra, Aakanksha,Tomer, Preeti,Dwivedi, Jaya,Kishore
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- Liquid-phase oxidation of naphthalene with H 2O 2 in the presence of ordered mesoporous V- m-Al 2O 3 catalysts
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Abstract: The ordered mesoporous V- m-Al 2O 3 catalysts were successfully synthesized via a facile one-pot evaporation-induced self-assembly (EISA) strategy and applied in the liquid-phase oxidation of naphthalene with hydrogen peroxide in the presence of ascorbic acid as a reductant. The physicochemical properties of the catalysts were investigated using various techniques, like XRD, N 2 sorption, UV-Vis spectra, Raman spectroscopy, XPS, XRF and TEM. Small-angle XRD, N 2 sorption and TEM results show that mesoporous V- m-Al 2O 3 catalysts possess a highly ordered mesostructure with large surface areas and narrow pore-size distributions. High-angle XRD, UV-Vis spectra and Raman spectroscopy results indicate that VO x species were homogeneously incorporated in the matrix of mesoporous Al 2O 3.The catalytic performance in the liquid oxidation of naphthalene with H 2O 2 over 8 V- m-Al 2O 3 catalyst (naphthalene conversion 45.4% and phthalic anhydride selectivity 61.0%) was higher than other catalysts. The vanadium species incorporated in the 8 V- m-Al 2O 3 sample were stable, and its catalytic stability was kept well even after repeated use for 5 times, which indicates a green and economical pathway for naphthalene degradation. Graphical Abstract: SYNOPSIS?In the presence of hydrogen peroxide as oxidant and ascorbic acid as reductant, ordered mesoporous V- m-Al 2O 3 catalysts were synthesized via a facile one-pot evaporation-induced self-assembly method and successfully applied to the liquid-phase oxidation of naphthalene.[Figure not available: see fulltext.].
- Zhou, Zhiwei,Yu, Yang,Qin, Juan,Zhang, Jiaqi,Cheng, Fulin,Wu, Wenliang
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p. 1373 - 1380
(2017/09/25)
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- Three Pd-decavanadates with a controllable molar ratio of Pd to decavanadate and their heterogeneous aerobic oxidation of benzylic C-H bonds
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By the combination of Pd-complexes and [V10O28]6-, three Pd-decavanadate compounds [Pd(NH3)4]3[V10O28]·8H2O (1), [Pd(deta)(H2O)]2(NH4)2[V10O28]·2H2O (2) (deta = diethylenetriamine) and [Pd(dpa)2](Hdpa)2(Et3NH)2[V10O28]·2H2O (3) (dpa = 2,2′-dipyridylamine) have been successfully synthesized and thoroughly characterized using single X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), infrared spectroscopy (FT-IR) and elemental analyses (EA). Interestingly, in the three compounds, the molar ratios of Pd to decavanadate vary from 3:1 to 1:1 by changing N-ligands. The three Pd-decavanadates as heterogeneous catalysts are active in the aerobic oxidation of benzylic hydrocarbons under solvent-free conditions without adding any additives and co-catalysts. Moreover, compound 1 can be reused three times without losing its activity.
- Huang, Xianqiang,Li, Jikun,Shen, Guodong,Xin, Nana,Lin, Zhengguo,Chi, Yingnan,Dou, Jianmin,Li, Dacheng,Hu, Changwen
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p. 726 - 733
(2018/04/30)
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- Solvent-controlled selective synthesis of biphenols and quinones: Via oxidative coupling of phenols
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A regioselective synthesis of unsymmetrical and symmetrical biphenols and binaphthols via oxidative coupling of phenols or naphthols in the presence of K2S2O8 in CF3COOH under ambient conditions is described. Interestingly, the 1:1 ratio of H2O and CH3CN solvent mixtures at 80 °C instead of CF3COOH provided substituted unsymmetrical quinones. A gram-scale synthesis of biphenols and binaphthols was demonstrated.
- More, Nagnath Yadav,Jeganmohan, Masilamani
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supporting information
p. 9616 - 9619
(2017/09/01)
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- Electrochemical synthesis of quinones and other derivatives in biphasic medium
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Electrochemical synthesis of quinones has been attempted from phenols, 1,4-dihydroxybenzenes, 1,4-dihydroxynaphthalenes and related compounds using biphasic media. Excellent yields of quinones (98%) or brominated diols have been achieved with good current efficiency. Reuse of the electrolyte without any modification and quantitative conversion of substrate with theoretical amount of current are the advantages of this method.
- Shanmugam,Kulangiappar,Ramaprakash,Vasudevan,Senthil Kumar,Velayutham,Raju
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p. 2294 - 2297
(2017/05/19)
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- Photooxygenation of oxygen-substituted naphthalenes
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The reaction of oxygen-substituted naphthalenes with singlet oxygen (1O2) has been investigated, and labile endoperoxides have been isolated and characterized at –78°C for the first time. Low-temperature kinetics by UV spectroscopy revealed that alkoxy and silyloxy substituents remarkably increase the rate of photooxygenations compared to 1,4-dimethylnaphthalene, whereas acyloxy-substituted acenes are inert towards 1O2. The reactivities nicely correlate with HOMO energies and free activation energies, which we determined by density functional theory calculations. The lability of the isolated endoperoxides is due to their very fast back reaction to the corresponding naphthalenes even at –20°C under release of 1O2, making them to superior sources of this reactive species under very mild conditions. Finally, a carbohydrate-substituted naphthalene has been synthesized, which reacts reversibly with 1O2 and might be applied for enantioselective oxidations in future work.
- Bauch, Marcel,Krtitschka, Angela,Linker, Torsten
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supporting information
(2017/08/23)
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- Oxidation of 4-methoxy-1-naphthol on promoted platinum catalysts
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Oxidative coupling of naphthols is a useful method for the formation of new carbon-carbon bonds in organic synthesis. In the presence of hydrogen peroxide, platinum supported on activated carbon catalyses this reaction. The outcome is influenced by the solvent, the reaction temperature and the physical structure of the catalyst. The catalyst structure is determined by the synthesis method and the modifier used (Bi or Sb). Within 40 min 4-methoxy-1-naphthol can be converted to 4,4'-dimethoxy-2,2'-binaphthalenyl-1,1'-diol with a yield of up to 94%, or to 4,4'-dimethoxy-2,2'-binaphthalenylidene-1,1'-dione with a yield of 92%. High amounts of quinoid byproducts (≤22%) are observed in nitromethane as the solvent.
- Maphoru,Heveling,Kesavan Pillai
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p. 441 - 447
(2017/08/08)
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- Cerium(IV) tetrabutylammonium nitrate (CTAN): A mild and efficient N-dearylation agent for synthesis of N-unsubstituted 2-azetidinones
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A simple and efficient protocol for the conversion of N-p-methoxyphenyl, N-p-ethoxyphenyl, N-p-methoxynaphthyl, N-3,4-dimethoxybenzyl and N-p-methoxybenzyl-2-azetidinones to N-unsubstituted 2-azetidinones using cerium(IV) tetrabutylammonium nitrate (CTAN) in dichloromethane is described. The method is compatible with a number of functional groups, and N-unsubstituted 2-azetidinones can be prepared under mild conditions at room temperature. The reaction is rapid, and pure products are obtained in good yields.
- Zarei, Maaroof
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p. 246 - 249
(2017/05/31)
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- Iron(III) fluorinated porphyrins: Greener chemistry from synthesis to oxidative catalysis reactions
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: Iron(III) fluorinated porphyrins play a central role in the biomimetics of heme enzymes and enable cleaner routes to the oxidation of organic compounds. The present work reports significant improvements in the eco-compatibility of the synthesis of 5,10,15,20-tetrakis-pentafluorophenylporphyrin (H2 TPFPP) and the corresponding iron complex [Fe(TPFPP)Cl], and the use of [Fe(TPFPP)Cl] as an oxidation catalyst in green conditions. The preparations of H2 TPFPP and [Fe(TPFPP)Cl] typically use toxic solvents and can be made significantly greener and simpler using microwave heating and optimization of the reaction conditions. In the optimized procedure it was possible to eliminate nitrobenzene from the porphyrin synthesis and replace DMF by acetonitrile in the metalation reaction, concomitant with a significant reduction of reaction time and simplification of the purification procedure. The Fe(III)porphyrin is then tested as catalyst in the selective oxidation of aromatics at room temperature using a green oxidant (hydrogen peroxide) and green solvent (ethanol). Efficient epoxidation of indene and selective oxidation of 3,5-dimethylphenol and naphthalene to the corresponding quinones is observed.
- Rebelo, Susana L. H.,Silva, Andre M. N.,Medforth, Craig J.,Freire, Cristina
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- ONO-pincer ruthenium complex-bound norvaline for efficient catalytic oxidation of methoxybenzenes with hydrogen peroxide
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The enhanced catalytic activity of ruthenium complex-bound norvaline Boc-l-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.
- Yoshida, Ryota,Isozaki, Katsuhiro,Yokoi, Tomoya,Yasuda, Nobuhiro,Sadakane, Koichiro,Iwamoto, Takahiro,Takaya, Hikaru,Nakamura, Masaharu
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supporting information
p. 7468 - 7479
(2016/08/16)
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- Biphasic copper-catalyzed C–H bond activation of arylalkanes to ketones with tert-butyl hydroperoxide in water at room temperature
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A facile C–H bond activation of arylalkanes to their corresponding ketones catalyzed by copper salts using tert-butyl hydroperoxide as an oxidant in water at room temperature is described. Easy product separation, simple reaction procedures (without using base or phase transfer catalysis), and catalyst recycling make the catalytic system attractive. It is also active beyond activated benzylic methylene positions and could tolerate factionalized arylalkanes with diverse groups.
- Hossain, Md. Munkir,Shyu, Shin-Guang
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supporting information
p. 4252 - 4257
(2016/07/06)
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- Sequential, One-Pot Access to Arylated Benzoquinones/Naphthoquinones from Phenols/Naphthols
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A sequential one-pot approach towards arylated benzoquinones and naphthoquinones is reported. The reaction proceeds through oxidation of phenols/naphthols followed by CH-arylation with a catalytic amount of triflic acid. Preliminary cytotoxic studies were carried out with five different cell lines and some of the compounds show promising activity. This one-pot approach towards arylated benzoquinones and naphthoquinones proceeds through oxidation of phenols/naphthols followed by CH-arylation. Preliminary cytotoxic studies for some of the compounds showed promising activity.
- Jiang, Jia-Heng,Boominathan, Siva Senthil Kumar,Hu, Wan-Ping,Chen, Chung-Yu,Vandavasi, Jaya Kishore,Lin, Ying-Ting,Wang, Jeh-Jeng
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supporting information
p. 2284 - 2289
(2016/05/19)
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- Copper-catalyzed divergent oxidative pathways of 2-naphthol derivatives:: Ortho -naphthoquinones versus 2-BINOLs
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Catalyst-dependent divergent pathways of 2-naphthol derivatives have been investigated. A readily available CuCl2-DMAP catalyst system promotes the aerobic oxidation of 2-naphthol derivatives to ortho-naphthoquinones whereas switching the catalyst system to Cu(OAc)2-DBN under an argon atmosphere allows the oxidative coupling of 2-naphthols to 1,1′-bi-2-naphthols (BINOLs) in good to excellent yields.
- Kim,Takizawa,Oh
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p. 7191 - 7196
(2016/08/05)
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- Synergistic Catalysis: Pd(II) Catalyzed Oxidation of 1,4-Dihydroquinones in the Pd(II) Catalyzed 1,4-Oxidation of Cyclic 1,3-Dienes
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Palladium(II) carboxylate salts have been shown to catalyze the oxidation of various hydroquinones to benzoquinones in the presence of t-BuOOH. This new catalytic system has been integrated into the oxidative 1,4-functionalization of cyclic 1,3-dienes where the palladium plays a remarkable dual role, catalyzing both the diene oxidation itself and the regeneration of the active quinone oxidant, which is required for diene functionalization. These new conditions offer considerable increases in reaction rate over prior art and allow a significant decrease in the equivalents of the nucleophilic carboxylate required for full conversion.
- Zheng, Bin,Schmidt, Michael A.,Eastgate, Martin D.
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p. 3112 - 3118
(2016/05/19)
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- Solvent and Temperature Effects on the Platinum-Catalyzed Oxidative Coupling of 1-Naphthols
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Using H2O2 as the oxidant, 1-naphthols with electron-donating groups at the 2- and 4-positions couple oxidatively over a carbon-supported platinum catalyst to 3,3′-substituted 1,1′-binaphthalenylidene-4,4′-diones and 4,4′-substituted 2,2′-binaphthalenylidene-1,1′-diones, respectively. The binaphthalenyl diols are the intermediates. The selectivity to individual products is influenced by the reaction temperature (room temp. or reflux) and by the solvent used. Under reflux, complete conversions are obtained within 40 min. At room temp. high diol yields can be obtained, e.g. 96 % from 2-methyl-1-naphthol in MeOH. Under reflux the reaction proceeds always further to the diones (at least to some extent), and THF is a promising solvent for the selective one-pot two-step oxidation of 1-naphthols to the diones (e.g. 81 % from 4-methoxy-1-naphthol). In most other solvents (reflux) naphthoquinones are observed as byproducts. In an attempt to optimize the yield of menadione, 30.5 % was obtained in boiling MeNO2.
- Maphoru, Mabuatsela V.,Heveling, Josef,Kesavan Pillai, Sreejarani
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p. 331 - 337
(2016/02/14)
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- A Facile and Selective Procedure for Oxidation of Hydroquinones using Silica Gel Supported Catalytic Cerium(IV) Ammonium Nitrate
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A new procedure for oxidation of hydroquinones to quinones using a silica gel supported cerium(IV) ammonium nitrate-NaBrO3 reagent has been developed. This simple, easy to prepare and use, heterogeneous reagent is highly selective towards oxidation of 1,4-dihydroxybenzenes and produces high yields of quinones. Waste generated by using this procedure is minimal.
- Ali, Mohammed Hashmat,Welker, Andrea,York, Crystal
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p. 3207 - 3211
(2015/10/19)
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- Initial development of a cytotoxic amino-seco-CBI warhead for delivery by prodrug systems
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Abstract Cyclopropabenzaindoles (CBIs) are exquisitely potent cytotoxins which bind and alkylate in the minor groove of DNA. They are not selective for cancer cells, so prodrugs are required. CBIs can be formed at physiological pH by Winstein cyclisation of 1-chloromethyl-3-substituted-5-hydroxy-2,3-dihydrobenzo[e]indoles (5-OH-seco-CBIs). Corresponding 5-NH2-seco-CBIs should also undergo Winstein cyclisation similarly. A key triply orthogonally protected intermediate on the route to 5-NH2-seco-CBIs has been synthesised, via selective monotrifluoroacetylation of naphthalene-1,3-diamine, Boc protection, electrophilic iodination, selective allylation at the trifluoroacetamide and 5-exo radical ring-closure with TEMPO. This intermediate has potential for introduction of peptide prodrug masking units (deactivating the Winstein cyclisation and cytotoxicity), addition of diverse indole-amide side-chains (enhancing non-covalent binding prior to alkylation) and use of different leaving groups (replacing the usual chlorine, allowing tuning of the rate of Winstein cyclisation). This key intermediate was elaborated into a simple model 5-NH2-seco-CBI with a dimethylaminoethoxyindole side-chain. Conversion to a bio-reactive entity and the bioactivity of this system were confirmed through DNA-melting studies (ΔTm = 13°C) and cytotoxicity against LNCaP human prostate cancer cells (IC50 = 18 nM).
- Twum, Elvis A.,Nathubhai, Amit,Wood, Pauline J.,Lloyd, Matthew D.,Thompson, Andrew S.,Threadgill, Michael D.
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supporting information
p. 3481 - 3489
(2015/08/03)
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- Synthesis of o-Carboxyarylacrylic Acids by Room Temperature Oxidative Cleavage of Hydroxynaphthalenes and Higher Aromatics with Oxone
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A simple procedure for the synthesis of a variety of o-carboxyarylacrylic acids has been developed with Oxone (2KHSO5·KHSO4·K2SO4); the oxidation reaction involves the stirring of methoxy/hydroxy-substituted naphthalenes, phenanthrenes, anthracenes, etc. with Oxone in an acetonitrile-water mixture (1:1, v/v) at rt. Mechanistically, the reaction proceeds via initial oxidation of naphthalene to o-quinone, which undergoes cleavage to the corresponding o-carboxyarylacrylic acid. The higher aromatics are found to yield carboxymethyl lactones derived from the initially formed o-carboxyarylacrylic acids.
- Parida, Keshaba Nanda,Moorthy, Jarugu Narasimha
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supporting information
p. 8354 - 8360
(2015/09/01)
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- Study of the Reactivity of [Hydroxy(tosyloxy)iodo]benzene Toward Enol Esters to Access α-Tosyloxy Ketones
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The reactivity of enol esters toward [hydroxy(tosyloxy)iodo]benzene (HTIB) was assessed. These substrates were found to be rapidly converted in high yields to their corresponding α-tosyloxy ketones. This transformation demonstrates that these substrates can act as ketone surrogates. The scope of the method was investigated and aromatic, aliphatic, and cyclic enol esters were found to be suitable substrates for the reaction. The relative reactivity of a model substrate toward HTIB and m-CPBA was investigated, and it was found that the reaction could be performed under catalytic conditions.
- Basdevant, Benoit,Legault, Claude Y.
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p. 6897 - 6902
(2015/10/06)
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