- DNA-Triggered Enhancement of Singlet Oxygen Production by Pyridinium Alkynylanthracenes
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There is an ongoing interest in 1O2 sensitizers, whose activity is selectively controlled by their interaction with DNA. To this end, we synthesized three isomeric pyridinium alkynylanthracenes 2 o–p and a water-soluble trapping reagent for 1O2. In water and in the absence of DNA, these dyes show a poor efficiency to sensitize the photooxygenation of the trapping reagent as they decompose due to electron transfer processes. In contrast, in the presence of DNA 1O2 is generated from the excited DNA-bound ligand. The interactions of 2 o–p with DNA were investigated by thermal DNA melting studies, UV/vis and fluorescence spectroscopy, and linear and circular dichroism spectroscopy. Our studies revealed an intercalative binding with an orientation of the long pyridyl-alkynyl axis parallel to the main axis of the DNA base pairs. In the presence of poly(dA : dT), all three isomers show an enhanced formation of singlet oxygen, as indicated by the reaction of the latter with the trapping reagent. With green light irradiation of isomer 2 o in poly(dA : dT), the conversion rate of the trapping reagent is enhanced by a factor >10. The formation of 1O2 was confirmed by control experiments under anaerobic conditions, in deuterated solvents, or by addition of 1O2 quenchers. When bound to poly(dG : dC), the opposite effect was observed only for isomers 2 o and 2 m, namely the trapping reagent reacted significantly slower. Overall, we showed that pyridinium alkynylanthracenes are very useful intercalators, that exhibit an enhanced photochemical 1O2 generation in the DNA-bound state.
- Fudickar, Werner,Bauch, Marcel,Ihmels, Heiko,Linker, Torsten
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- Photochemical Reactions of Bromoanthraquinones in Ethanol at Room Temperature Studied by Steady-State Photolysis and Laser Photolysis
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Photolyses of α-bromoanthraquinones (1-bromo-, 1,5-dibromo- and 1,8-dibromoanthraquinones) with 366 nm light in ethanol at room temperature gave rise to the formation of debrominated 9,10-anthracenediol as a final product.This was interpreted in terms of the sequence of the formation of α-bromo-9,10-anthracenediols followed by the photochemical dehydrobromination yielding the corresponding anthraquinones with one less bromine atom than original ones.Photolysis of 2-bromoanthraquinone gave rise to the formation of 2-bromo-9,10-anthracenediol, and no dehydrobromination was observed.Combined with the values of the quantum yields of photoreduction, the results of the laser photolyses revealed that the rate constant for the hydrogen-atom abstraction from ethanol decreased as an increase of the ??* character of the lowest triplet states of a α-bromoanthraquinones.
- Hamanoue, Kumao,Nakayama, Toshihiro,Sawada, Kazuhide,Yamamoto, Yoshiaki,Hirase, Susumu,Teranishi, Hiroshi
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- Radical-Pair Dynamics in the Photoreduction of Anthraquinone in Sodium Dodecyl Sulfate Micellar Solution Detected by Pulse-Mode Product-Yield-Detcted Electron Spin Resonance: Temperature and Salt Dependence
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The dynamical behavior of the radical pair (RP) produced in the photoreduction of anthraquinone in sodium dodecyl sulfate (SDS) micellar solutions has been observed at various temperatures and salt concentrations by using the pulse-mode product-yield-detected ESR (PYESR) technique.Trough the numerical calculation of the time-domain PYESR response by the Runge-Kutta method applied to a reaction scheme, dynamical parameters such as the escape rate of the RP (kESC) and the rate of spin trapping directly from the RP (kST) have been obtained.Since these kinetic parameters are very informative for elucidating the micelle dynamics, we may call this method the "spin-pair-probe" technique.
- Polyakov, Nicolai E.,Okazaki, Masaharu,Konishi, Yoshinari,Toriyama, Kazumi
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- Formation of Anthrahydroquinones (XAQH2) via Excited Singlet Charge-transfer Complexes (or Singlet Ion Pairs) of Anthraquinones with 2,5-Dimethylhexa-2,4-diene (DMHD), and Photochemical Reaction of XAQH2 with DMHD
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Upon picosecond excitation of a ground-state complex formed between anthraquinone (AQ, a typical planar molecule) and 2,5-dimethylhexa-2,4-diene (DMHD), an excited singlet charge-transfer complex 1(AQδ--DMHDδ+)*> or a singlet ion pair 1(AQ.--DMHD.+)> is produced within the duration of the excitation light pulse.This transient complex decays following a single-expotential function with a lifetime of 90 ps and the decay process is ascribed to the intracomplex proton transfer, yielding the semiquinone radical of AQ and the 2,5-dimethylhexa-2,4-dienyl radical.A similar result has been obtained for non-planar 1,8-dichloroanthraquinone (cf.Hamanoue et al., J.Photochem.Photobiol.A: Chem., 1993, 76, 7), and so nanosecond laser photolysis of XAQ (anthraquinone or 1,8-dichloroanthraquinone) has also been performed and the second-order decay rate constant of the semiquinone radical (XAQH(1.) of XAQ generated in DMHD-toluene is found to be one order of magnitude greater than that generated in ethanol without DMHD.Hence, it is concluded that XAQH(1.) abstracts a hydrogen atom from the 2,5-dimethylhexa-2,4-dienyl radical yielding a photoreduced product (XAQH2, i.e. anthrahydroquinone or 1,8-dichloroanthrahydroquinone) and a biradical of DMHD; probably the reactions of this biradical yield the dimeric and oligomeric compounds of DMHD.Although steady-state photolysis of XAQ in neat DMHD causes the disappearance of the reactant absorption without the accompanying formation of XAQH2, examination of the effect of DMHD concentration on the formation of XAQH2 upon steady-state photolysis of XAQ in DMHD-toluene (or benzene) reveals that XAQH2 disappears by its photochemical reaction with ground-state DMHD.For anthrahydroquinone, the formation of 4',4'-dimethyl-3'-(2-methylprop-1-en-1-yl)spiro-9(10H)-one is confirmed.
- Nakayama, Toshihiro,Nakamura, Noriyasu,Miki, Sadao,Hamanoue, Kumao
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- Luminescence of a new Ru(II) polypyridine complex controlled by a redox-responsive protonable anthra[1,10]phenanthrolinequinone
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Redox-controlled luminescence quenching is presented for a new Ru(II)-bipyridine complex [Ru(bpy)2(1)]2+ where ligand 1 is an anthra[1,10]phenanthrolinequinone. The complex emits from a short-lived metal-to-ligand charge transfer, 3MLCT state (τ = 5.5 ns in deaerated acetonitrile) with a low luminescence quantum yield (5 × 10 -4). The emission intensity becomes significantly enhanced when the switchable anthraquinone unit is reduced to corresponding hydroquinone. On the contrary, chemical one-electron reduction of the anthraquinone moiety to semiquinone in aprotic tetrahydrofuran results in total quenching of the emission.
- Hartl, Frantisek,Vernier, Sandrine,Belser, Peter
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- Solvent Effects on the Formation and Decay of Ionic Intermediates for the Photoreduction of Anthraquinone by Triethylamine in Ethanol, Toluene, and Acetonitrile at Room Temperature
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In toluene and ethanol containing triethylamine (TEA), a reaction of the lowest excited triplet state 3AQ(T1)> of anthraquinone (AQ) with ground-state TEA gave rise to the formation of an exciplex 3(AQ-TEA)*> which converted into a contact ion pair between the AQ radical anion (AQ-.) and the TEA radical cation (TEA+.).By an intramolecular proton transfer, this contact ion pair yielded anthrasemiquinone radical followed by the formation of 9,10-anthracenediol (AQH2); in ethanol, the monoanion (AQH-) of AQH2 was also produced.In ethanol TEA, moreover, not only the decay rate constant of 3(AQ-TEA)* but also the quantum yield for the photoreduction of AQ were affected by the change of TEA concentration.This was interpreted in terms of the existence of a rapid interconversion between 3(AQ-TEA)* and a triplex 3(AQ-TEA2)*> of 3AQ(T1) with ground-state TEA.In contrast to the exciplex formation in ethanol and toluene, free AQ-anion radical (and TEA-cation radical) and 3(AQ-TEA)* 3(AQ-TEA)* or the contact (or solvent-separated) ion pair dissocited into the radical ions (AQ-anion radical and TEA-cation radical) followed by their second-order reaction yielding finally AQH2 and AQH-.
- Hamanoue, Kumao,Nakayama, Toshihiro,Sasaki, Hideyuki,Ikenaga, Koichiro,Ibuki, Kazuyasu
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- PHOTOCHEMICAL REACTIONS OF CHLOROANTHRAQUINONES
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Irradation of 1,5-dichloroanthraquionone (1,5-DCAQ) with 366 nm light in ethanol gives anthrahydroquinone (AQH2) as a final product.This is interpreted interms of the following cosecutive reactions; 1,5-DCAQ --hν--> 1,5-dichloroanthrahydroquinone --hν--> 1-chloroanthraquinone --hν--> 1-chloroanthrahydroquinone --hν--> anthraquinone --hν--> AQH2.Similar reactions were also observed for other α-chloroanthraquinones.
- Hamanoue, Kumao,Yokoyama, Kazuo,Miyake, Takao,Kasuya, Toshihiro,Nakayama, Toshihiro,Teranishi, Hiroshi
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- Mechanism of С-Н cyclization of alkynylanthraquinones into thienoanthraquinones with the participation of sodium sulfide
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The CH-cyclization of alkynyl-9,10-anthraquinones 1 into thienoanthraquinones 2 is shown to be initiated by the neutral S2 molecule and not by the sulfide anion as it is assumed in the existing model of CH-cyclization with the nucleophiolic substitution of H. The formation of S2 takes place in the reaction medium due to the partial reduction of the substrate 1 by Na2S into the corresponding anthrahydroquinone, which is inactive in the main reaction. We present a new cyclization mechanism with the key stage involving the electrophilic displacement of H, which results in the formation of the reaction product 2 and elimination of S. In the reaction medium atomic sulfur is transformed into S2, which initiates the next cyclization act. This determines the chain nature of cyclization with the participation of S2. Within this model, the route to increase the yield of target thienoanthraquinones is proposed through the introduction of a neutral quinone able to generate S2 by means of easy reduction.
- Fedenok, Lidiya,Dultsev, Fedor,Barabanov, Igor,Polyakov, Nikolay
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- Th-symmetrical hexakisadducts of C60 with a densely packed π-donor shell can act as energy- or electron-transducing systems
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For the first time several Th-symmetrical hexakisadducts of C60 bearing up to six electro- and photoactive o-phenylene diamine or 9,10-dialkoxyanthracene moieties were synthesized and subjected to photoinduced electron/energy-transfer studies. Both donors form a densely packed π-donor shell surrounding the fullerene core. In these novel core-shell ensembles (7 and 19), either an efficient energy transfer from the dialkoxyanthracene periphery, or an electron transfer from the o-phenylene diamine periphery transduces the flow of excited-state energy or electrons, respectively, to the fullerene moiety, which resides in the central core. Due to the relatively high reduction potential of the fullerene core, which is anodically shifted by ≈0.7 V, compared with that of pristine C60, the outcome of these intramolecular reactions depends mainly on the donor ability of the peripheral system. Interestingly, the charge-separated state in the o-phenylene diamine heptad (7; τ = 2380 ns in benzonitrile) is stabilized by a factor of 20 relative to the corresponding o-phenylene diamine dyad (6; τ = 120 ns in benzonitrile), an effect that points unequivocally to the optimized storage of charges in this highly functionalized fullerene ensemble.
- Diekers, Michael,Luo, Chuping,Guldi, Dirk M.,Hirsch, Andreas
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- Anthraquinone thin-film electrodes for reversible CO2 capture and release
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We report reversible electrochemical capture and release of carbon dioxide using the well-known dye precursor and industrial catalyst anthraquinone. Although quinones are well-studied for electrochemical capture and release of CO2 in solution, we have discovered that a 100 nm film of anthraquinone can realize this in a heterogeneous fashion. In-depth spectroelectrochemical studies were performed in order to study the mechanism of this CO2 capture and release. Anthraquinone films reached an uptake capacity of 5.9 mmolCO2 gAQ-1.
- Wielend, Dominik,Apaydin, Dogukan Hazar,Sariciftci, Niyazi Serdar
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- ANTI-MIGRATION PHOTOPOLYMERIZATION SENSITIZER
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PROBLEM TO BE SOLVED: To provide a photopolymerization sensitizer that realizes a practically sufficient photocuring rate without the problem of an additive such as a photopolymerization sensitizer exuding to a surface resulting in coloring or chalking of a cured product, caused by blooming or the like during photocuring or during storage of the cured product. SOLUTION: There is provided a 9,10-bis(cycloalkyl-substituted alkoxycarbonylalkyleneoxy)anthracene compound having an ester group represented by the general formula (1) in the figure. (In the general formula (1), A represents a C1-20 alkylene group that may be branched to an alkyl group; and R represents a C3-20 cycloalkyl group or C4-20 cycloalkylalkyl group.) SELECTED DRAWING: None COPYRIGHT: (C)2021,JPOandINPIT
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Paragraph 0229-0230
(2020/11/04)
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- Intermediates in the cleavage of endoperoxides
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The decomposition of anthracene endoperoxides has been investigated under various conditions. Thermolyses proceed via radical intermediates and afford anthracenes and rearrangement products, depending on the substitution pattern. Interestingly, not only the O–O but also the C–O bond can be cleaved homolytically. Under basic conditions fragmentations take place, affording anthraquinone, and reactive oxygen species. This mechanism explains the often observed decomposition of endoperoxides during work-up. Finally, an acid-catalyzed cleavage has been observed under release of hydrogen peroxide. The results should be interesting for the mechanistic understanding of peroxide decomposition and the endoperoxides might serve as mild sources of reactive oxygen species for future applications. Copyright
- Bauch, Marcel,Klaper, Matthias,Linker, Torsten
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supporting information
(2017/03/24)
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- Visible light-responsive micelles formed from dialkoxyanthracene-containing block copolymers
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A class of dialkoxyanthracene-containing diblock copolymers is synthesized which possesses visible light-responsivity. These copolymers can self-assemble into a micellar structure in water. Green visible light (540 nm) is able to scissor these anthracene species and cleave the diblock copolymer into two fragments, inducing disassembly of the self-assembled micelles.
- Yan, Qiang,Hu, Jun,Zhou, Rong,Ju, Yong,Yin, Yingwu,Yuan, Jinying
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supporting information; experimental part
p. 1913 - 1915
(2012/03/13)
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- 1,9-dialkoxyanthracene as a 1O2-sensitive linker
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We developed a 1O2-sensitive linker based on a 9,10-dialkoxyanthracene structure. Its cleavage in the presence of 1O2 is quick and high-yielding. A phosphoramidite containing this fragment was prepared and coupled to a variety of molecular fragments, including nucleosides, fluorescent dyes, and a cholesteryl derivative. On the basis of this building block we prepared a fluorogenic probe for monitoring 1O2 in live mammalian cells and visible-light-activated "caged" oligodeoxyribonucleotides. In particular, the fluorogenic 1O2 probe is a conjugate of 4,7,4′,7′-tetrachlorofluorescein and N,N,N′,N′- tetramethylrhodamine coupled to each other via the 1O 2-sensitive linker. Fluorescence of the dyes in this probe is quenched. In the presence of 1O2, the linker is cleaved with formation of 9,10-anthraquinone and two strongly fluorescent dyes: 4,7,4′,7′-tetrachlorofluorescein and N,N,N′,N′- tetramethylrhodamine derivatives. We observed that the fluorescence of the probe correlates with the amount of 1O2 present in solution. The red-light-activated "caged" oligodeoxyribonucleotides are stable duplexes, which consist of an unmodified strand and a blocker strand. The 1O2-sensitive linker is introduced in the interior of the blocker strand. Upon exposure of the duplex to red light in the presence of In3+(pyropheophorbide-a) chloride, the linker is cleaved with formation of the unstable duplex structure. This product decomposes spontaneously, releasing the unmodified strand, which can bind to the complementary target nucleic acid. This uncaging reaction is high-yielding. In contrast, previously reported visible-light-activated reagents are uncaged inefficiently due to competing reactions of sulfoxide and disulfide formation.
- Arian, Dumitru,Kovbasyuk, Larisa,Mokhir, Andriy
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experimental part
p. 3972 - 3980
(2011/05/09)
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- Photocatalytic degradation of polycyclic aromatic hydrocarbons in GaN:ZnO solid solution-assisted process: Direct hole oxidation mechanism
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GaN:ZnO exhibits excellent activity for the photodegradation of PAHs, and the activity can be obviously improved by loading Pt. The degradation of PAHs in the system of GaN:ZnO is induced by the formation of holes. The holes generated then interact with PAHs to produce PAHs+, which is active enough to react with O2.
- Kou, Jiahui,Li, Zhaosheng,Guo, Yong,Gao, Jun,Yang, Ming,Zou, Zhigang
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experimental part
p. 48 - 54
(2010/10/01)
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- Photolytic transformations of p-quinones
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Quantum yields, apparent photolysis rate constants, and energies of activation of the dark stages in the decomposition of 3,6-di-tert-butyl-2,3- epoxy-5-hydroxycyclohex-2-ene-1,4-dione, 1,4-naphthoquinone, and 9,10-anthraquinone under irradiation at λ 313 nm and of 1,4-benzoquinone under irradiation at λ 232-254 nm were determined. Products of photochemical transformations of these compounds in saturated hydrocarbons were identified, and a probable mechanism of these transformations was proposed.
- Mishchenko,Maslennikov,Spirina,Kurskii,Faerman,Maslennikov
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body text
p. 1529 - 1532
(2009/06/28)
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- Photoinduced electron-transfer systems consisting of electron-donating pyrenes or anthracenes and benzimidazolines for reductive transformation of carbonyl compounds
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Photoinduced electron-transfer reactions of several ketone substrates were studied to evaluate the utilities of 1,6-bis(dimethylamino)pyrene (BDMAP), 1,6-dimethoxypyrene (DMP), 9,10-bis(dimethylamino)anthracene (BDMAA), and 9,10-dimethoxyanthracene (DMA) as electron-donating sensitizers cooperating with 2-aryl-1,3-dimethylbenzimidazolines. BDMAP and DMP generally led higher conversion of ketones and better yield of reduction products compared to BDMAA and DMA.
- Hasegawa, Eietsu,Takizawa, Shinya,Seida, Takayuki,Yamaguchi, Akira,Yamaguchi, Naoto,Chiba, Naoki,Takahashi, Tomoya,Ikeda, Hiroshi,Akiyama, Kimio
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p. 6581 - 6588
(2007/10/03)
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- Facile and selective aerobic oxidation of arylalkanes to aryl ketones using cesium carbonate
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Various arylalkanes such as fluorenes, xanthene, anthrone, 9,10-dihydroanthracene, and diphenylmethane are effectively transformed into the corresponding aryl ketones, while amino and aldehyde functionalities remain intact, under air in the presence of cesium carbonate. Georg Thieme Verlag Stuttgart.
- Park, Kwanghee Koh,Tsou, Lun K.,Hamilton, Andrew D.
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p. 3617 - 3620
(2008/03/13)
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- Photoreduction of 9,10-Anthraquinone Derivatives: Transient Spectroscopy and Effects of Alcohols and Amines on Reactivity in Solution
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The photoreduction of 9,10-anthraquinone (AQ), the 2-methyl, 2-ethyl, 2,3-dimethyl, 1,4-difluoro, 1-chloro and 1,8-dichloro derivatives as well as 1,4,4a,9a-tetrahydroanthraquinone, 1,2-benzanthraquinone and 6,13-pentacenequinone in nonaqueous solution at room temperature was studied by time-resolved UV-visible spectroscopy. Upon 308 nm excitation of AQ the triplet state reacts with alcohols and triethylamine (TEA). The rate constant of triplet quenching by amines is close to the diffusion-controlled limit. The semiquinone radical .QH/Q.- is the main intermediate, and the half-life of the second-order decay kinetics depends significantly on the donor and the medium. Photoinduced charge separation after electron transfer from amines to the triplet state of AQ in acetonitrile and the subsequent charge recombination or neutralization also were measured by transient conductivity. The maximum quantum yield, λirr = 254 nm, of photoconversion into the strongly fluorescing 9,10-dihydroxyanthracenes is close to unity. The fluorescence with maximum at 460-480 nm and a lifetime of 20-30 ns disappears as a result of a complete recovery into AQ, when the dihydroxyanthracenes are exposed to oxygen. The mechanisms of photoreduction of parent AQ in acetonitrile by 2-propanol and in benzene and acetonitrile by TEA are discussed. The effects of AQ follow essentially the same pattern. The various functions of oxygen, e.g. (1) quenching of the triplet state; (2) quenching of the semiquinone radical, thereby forming HO2 ./O2.- radicals; and (3) trapping of the dihydroxyanthracenes are outlined.
- Goerner, Helmut
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p. 171 - 179
(2007/10/03)
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- THE SELECTIVE FUNCTIONALIZATION OF SATURATED HYDROCARBONS. PART 28. THE ACTIVATION OF BENZYLIC METHYLENE GROUPS UNDER GOAGGIV AND GOAGGV CONDITIONS
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Under GoAggIV and GoAggV conditions, cyclohexadienes were oxidized to give aromatic products instead of ketones and alcohols.At the same time, anthracene was oxidized to give anthraquinone.Under GoAggIV and GoAggV conditions, xanthene, fluorene and diphenylmethane were oxidized to give the corresponding xanthone, fluorenone and benzophenone following two possible pathways: a) alkane to alkyl t-butylperoxide to ketone, and b) alkane to ketone, in which alkyl hydroperoxide, derived from oxygen, may be the reaction intermediate.Xanthyl azide was formed when sodium azide was added to the reaction mixture of xanthene under GoAggIV and GoAggV conditions.The reaction of triphenylmethane under GoAggV conditions gave triphenylmethyl t-butyl peroxide as the major product and hydroperoxide as the minor product.When TEMPO was added, triphenylmethyl hydroperoxide was the only product.
- Barton, Derek H. R.,Wang, Tie-Lin
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p. 1011 - 1032
(2007/10/02)
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- Reaction of Aluminium Hydride-Triethylamine Complex with Selected Organic Compounds Containing Representative Functional Groups
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The addition of triethylamine to a solution of aluminium hydride in tetrahydrofuran (THF), which was prepared by the addition of a calculated amount of hydrogen chloride in diethyl ether to solutions of sodium aluminium hydride in THF, provides very stable solutions of aluminium hydride-triethylamine complex (AHTEA).The reducing power of AHTEA complex in tetrahydrofuran toward 59 selected organic compounds containing representative functional groups under practical conditions (tetrahydrofuran, room temperature, the quantitative amount of reagent to compound) has been investigated.In this way, we have established that quantitative reduction of various organic functionalities can be readily achieved using the calculated quantity of AHTEA to avoid the use of excess reagent.This permits ready use of the aluminium hydride reagent in organic synthesis with high convenience and efficiency, with the possibility of an improved selectivity than that of aluminium hydride itself in tetrahydrofuran.
- Cha, Jin Soon,Brown, Herbert C.
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p. 3974 - 3979
(2007/10/02)
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- Aluminium triiodide promoted reduction and in situ cycloaddition of benzoquinonoid compounds
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AlI3 efficiently promotes reduction of benzoquinonoid compounds (1a-d) to diols (2a-d). 9,10-Anthraquinone (1c) undergoes facile in situ reductive cycloadditions with N-N-methylmaleimide and fumaronitrile affording 3 and 4 respectively under the influence of AlI3.
- Dutta, Dilip K,Boruah, Romesh C,Sandhu, Jagir S
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p. 780 - 781
(2007/10/02)
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- Photochemical properties of aromatic carbonyl compounds belonging to different spectral luminescence groups of molecular systematics
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The photochemical activity in photo-reduction reactions of a series of carbonyl compounds in ethanol and heptane solutions has been studied at room temperature.The quantum yields of the photo-dissociation of the molecules have been determined.The relative positions of the electronic states of different orbital nature and multiplicity have been compared with the efficiency of the photo-conversion and the mechanism of the photo-reaction in the case of 1,4-quinones and aromatic diketones.
- Kudryasheva, N. S.,Val'kova, G. A.,Shigorin, D. N.,Gorelik, M. V.
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- PREPARATIVE ELECROCHEMICAL LIBERATION OF ARENES AND HETEROCYCLES FROM THEIR RESPECTIVE IRONCYCLOPENTADIENYL COMPLEXES
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Electrolysis of arene and heterocycle cyclopentadienyliron hexafluorophosphates led to the liberation of arenes or heterocycles in 69-90percent yield.The procedure described gives yields comparable with or superior to the yields obtained from pyrolytic sublimation used previously.
- Sutherland, Ronald G.,Abd-El-Aziz, Alaa S.,Piorko, Adam,Baranski, Andrzej S.,Lee, Choi Chuck
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p. 189 - 196
(2007/10/02)
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- The Orbital Nature and the Spectral-luminescent and Photochemical Properties of Molecules. V. Radiative and Non-radiative Excited States of Derivatives of Anthraquinone and Their Photochemical Properties
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We have studied the mechanism of the photochemical reactions and determined the quantum yield for the photoreduction of 2-R-derivatives of 9,10-anthraquinone (R = H, Br, I, SnEt3) in hexane and ethanol solutions at 293 K.It is shown that the contribution of the orbitals of the substituents to the electronic structure of the radiative and non-radiative excited electronic states of these molecules influences the efficiency of the photo-process.
- Rudenko, N. A.,Val'kova, G. A.,Shigorin, D. N.,Gorelik, M. V.
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p. 368 - 370
(2007/10/02)
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- Phase-transfer Catalysis under Reductive Conditions: Hydroquinone Dialkyl Ethers from Quinones
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Hydroquinone ethers with alternant and nonalternant topology are prepared in one-pot reactions from the corresponding quinones by using sodium dithionite, sodium hydroxide, and alkylating reagents under phase-transfer conditions (Adogen 464).The use of allyl bromide leads to O- and C-allylation.
- Seitz, Ulrich,Daub, Joerg
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p. 686 - 689
(2007/10/02)
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- Kinetic Isotope Effects and Pressure Effects in Several Hydrogen-Transfer Reactions of Tetralin and Related Compounds
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The H/D kinetic isotope effects and activation volumes have been measured for several hydrogen-transfer reactions using tetralin, dihydronaphthalenes, cyclohexa-1,4-diene, and cyclohexanol as donors.The isotope effects were found to exhibit different patterns for reactions of different mechanisms.They indicate whether hydrogen is in transit in the activated complex and show the number of atoms in transit (one or two).The KIE for the reaction of tetralin with quinones is consistent with concerted transfer of two hydrogens whereas the other reactions were found to be stepwise.The activation volumes lie within the range -23 to -33 mL/mol and do not seem to differetiate among bimolecular mechanisms.The relevance to previous studies of the KIE and ΔV(excit.) for coal hydrogenation reactions is discussed.
- Pajak, Janusz,Brower, K. R.
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p. 2210 - 2216
(2007/10/02)
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- Photooxidation of Leuco Dyes. X. Investigation of the Photooxidation of Di-potassiumantracene 9,10-ylene-di-sulfate
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Photolysis of the title compound (DHAE) in water or ethanol produces anthraquinone and anthrone.In deoxygenated solutions 9,10-dihydroxyanthracene is detected as a long lived intermediate.Laser and conventional flash photolysis reveals three short-lived transients with lifetimes of 200 ns, 2 and 410 ms.Different temperature dependencies are observed for the fluorescence and the photolysis quantum yields.This is interpreted by two successive thermally activated processes: photohomolysis of O-S-bond and escape of the radical pair from the solvent cage.The results are di scussed with the help of a reaction scheme proposed for the photolysis of DHAE.
- Langbein, H.,Hinzmann, G.,Grummt, U.-W.,Koch, R.,Fassler, D.
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p. 633 - 642
(2007/10/02)
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- Aromatic Hydroxylation and Deacylation of 9-Acylanthracenes by Copper(II)-peroxydisulfate
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The Cu2+-S2O82- oxidations of 9-acylanthracenes (1) and 9-acyl-10-methylanthracenes (10) having formyl (a), acetyl (b), or benzoyl (c) groups were studied in refluxing acidic acetonitrile-water.Radical cations 1a-c, 10a, and 10c reacted with water to produce 10-hydroxyl adduct radicals which were oxidized by Cu2+ to produce the corresponding hydroxylated products: 10-acylanthrols (5) from 1 and 9-acyl-10-methyl-9,10-dihydroxy-9,10-dihydroanthracenes (15) from 10.Compounds 5 and 15 were unstable to reaction conditions and underwent subsequent reactions.Compound5 underwent tautomerization competitive with oxidation to respectively produce 10-acyl-9-anthrones (6) and 10-acyl-10-hydroxy-9-anthrones (8).Compounds 6 and 8 were hydrolytically unstable, yielding respectively anthrone and 9,10-dihydroxyanthracene, at rates dependent on acidity (6a, 6b, and 6c exhibited 2.6, 44. and 45 min half-lives, respectively, in 0.1 M HClO4).Compounds 15a and 15c solvolyzed in the acidic media to give 10-methylanthrol which was further oxidized to produce 10-methyl-10-hydroxy-9-anthrone (12).Partial dehydration of 12 produced 10-methylene-9-anthrone.Little product was formed by proton loss from the radical cations of 1a, 10a, and 10c.
- Camaioni, Donald M.,Alnajjar, Mikhail S.
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p. 4456 - 4461
(2007/10/02)
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- Selective Reductions. 36. Reaction of Lithium 9-Boratabicyclononane with Selected Organic Compounds Containing Representative Functional Groups
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The approximate rates, stoichiometry, and products of the reaction of lithium 9-boratabicyclononane with selected organic compounds containing representative functional groups were examined under standard conditions (tetrahydrofuran, room temperature) in order to explore the reducing characteristics of this reagent and to establish the utility of this reagent as a selective reducing agent.Primary alcohols, phenols, and thiols evolve hydrogen rapidly and quantitatively.However, the reaction of 3-hexanol and 3-ethyl-3-pentanol is very slow. n-Hexylamine is inert to this reagent.Aldehydes and ketones are reduced rapidly and quantitatively to the corresponding alcohols.Even the highly hindered ketone, 2,2,4,4-tetramethyl-3-pentanone, is reduced within 30min.Reduction of camphor gives 91percent isoborneol and 9percent borneol, respectively.Cinnamaldehyde is rapidly reduced to the cinnamyl alcohol quantitatively without attacking the double bond.Carboxylic acids liberate hydrogen rapidly and quantitatively, but further reduction is very slow.Anhydrides consume 2 equiv of hydride without further hydride uptake, corresponding to reduction to an equimolar mixture of carboxylic acid and alcohol.Acid chlorides, esters, and lactones are rapidly reduced to the corresponding alcohols.Epoxides utilize 1 equiv of hydride at a moderate rate.In the case of unsymmetrical epoxides, the Markovnikov ring opening is predominant.Acetal, ketal, and ortho esters are inert to this reagent.Primary amides liberate hydrogen slowly.Caproamide undergoes slow reduction, but benzamide is not reduced.Tertiary amides consume 2 equiv of hydride slowly, undergoing reduction to the corresponding amines.Benzonitrile is reduced to the amine stage within 12 h; however, an aliphatic nitrile, capronitrile, is reduced only sluggishly. 1-Nitropropane rapidly liberates 1 equiv of hydrogen, but further reduction is very slow.Nitrobenzene utilizes 2.5 equiv of hydride, 1 for hydrogen evolution and 1.5 for reduction.Azobenzene is inert and azoxybenzene is reduced very sluggishly.Cyclohexanone oxime rapidly evolves 1 equiv of hydrogen, but no reduction is observed.Phenyl isocyanate consumes only 1 equiv of hydride to proceed to the formanilide stage.Pyridine is reduced very slowly.However, pyridine N-oxide undergoes rapid reduction with this reagent.Disulfides are rapidly reduced to the thiol stage, whereas, sulfoxides, sulfones, sulfonic acids, and sulfides are inert to this reagent.Cyclohexyl tosylate is also inert, but n-octyl tosylate undergoes reduction within 3.0 h.This hydride is inert to a typical n-alkyl chloride but reacts moderately with n-alkyl bromide and rapidly with an n-alkyl iodide.A secondary alkyl bromide is almost inert to this hydride.
- Brown, Herbert C.,Mathew, C. Poonoose,Pyun, Chongsuh,Son, Jong Chan,Yoon, Nung Min
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p. 3091 - 3097
(2007/10/02)
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