- Reagent Design and Study of p-Benzoquinone Derivatives. The Site-Selective Cycloaddition Reaction of Diquinones and Photochemical Cage Formation of the Adducts
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Cycloaddition reactions of naphthodiquinone derivatives and the photochemical behavior of their adducts have been investigated.Naphthodiquinone (4) and dichloronaphthodiquinone (5) reacted exclusively at the internal double bond with both cyclopentadiene and quadricyclane to give the corresponding 1:1 adducts in high yields.While anthradiquinone (6) reacted also only at the internal double bond with quadricyclane, the reaction with cyclopentadiene took place at both the internal and terminal double bonds of 6.The stereochemistry of the adducts was determined by spectral inspections and chemical transformations.The cyclopentadiene adducts were photochemically converted into the cage compounds in high yields, although the quadricyclane adducts were photoinert.In the photochemical reactions, high site selectivity was observed; the intramolecular ? photoaddition occurred only between enedione (electron poor) and cyclopentene (electron rich) double bonds.
- Yoshino, Setsuo,Hayakawa, Kenji,Kanematsu, Ken
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- Electrochemical and spectral study of the redox behavior and cardiotoxicity of anticancer drugs with antraquinone structure: Quinizarin
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1,4-dihydroxyanthraquinone (quinizarin) is the simplest molecule, which represents the structure of the specific chromophore for some biological and pharmaceutical compounds, being the main part in the chemical structure of daunorubicin, doxorubicin, and mitoxantrone. The present paper investigates the behavior in reduction and oxidation processes of quinizarin in aprotic neutral and basic media by coupled electrochemical and spectral techniques (in-situ techniques), including absorption spectroscopy, in order to identify the intermediate species and to propose a reaction mechanism. The influence of electrogenerated bases (EGB) was investigated by comparison with the spectroelectrochemistry in presence of added tetrabutylammonium hydroxide (TBOH). The proposed reaction sequences are supported by Digisim 3.03 simulations. Semiempirical MO-calculations were performed to determine the electronic structural features implied in reduction and oxidation processes and to analyze the energetics of the electron transfer (ET) from different reduction intermediates to molecular oxygen.
- Latus, Alina,Volanschi, Elena
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scheme or table
p. 1131 - 1140
(2012/07/27)
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- The synthesis of kermesic acid and isokermesic acid derivatives and of related dihydroxyanthraquinones
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Cochinellic anhydride methyl, ethyl and benzyl esters (4-methoxy-4-ethoxy- and 4-benzyloxy-carbonyl-5-hydroxy-3-methylphthalic anhydrides) have been prepared by a single stage Diels-Alder reaction of 2-bromomaleic anhydride with 3-alkoxycarbonyl-2,4-bis(trimethylsilyloxy)penta-1,3-dienes. The corresponding 5-methyl ether ethyl ester has been obtained by a similar addition reaction but with 3-ethoxycarbonyl-2-methoxy-4-trimethylsilyloxypenta-1,3-diene. The synthesis of methyl 6-deoxykermesate by the acylation of 1,4-dimethoxybenzene in the presence of boron trifluoride-diethyl ether with cochinellic anhydride methyl ester is unsuccessful. The preferred route is by the Diels-Alder addition of 3-alkoxycarbonyl-2,4-bis(trimethylsilyloxy)penta-1,3-dienes to naphthazarin (or 2-chloronaphthazarin). Lead tetraacetate oxidation of methyl 6-deoxykermesate affords a bis(quinone), Thiele acetoxylation of which gives after hydrolysis and permethylation, a mixture of derivatives of kermesic and isokermesic acids in equal proportions. The Diels-Alder addition of 3-chlorojuglone and 3-alkoxycarbonyl-2,4-bis(trimethylsilyloxy)penta-1,3-dienes has led to an improved synthesis of aloesaponarin-I (3,8-dihydroxy-2-methoxycarbonyl-1-methylanthra-8,10-quinone), while juglone itself affords an isomer which may be the 3,5-dihydroxy compound.
- Bingham, Stephen J.,Tyman, John H. P.
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p. 3637 - 3642
(2007/10/03)
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- 1H and 13C NMR studies of some anthraquinones and anthracenetetrones
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1H and 13C NMR chemical shifts are reported and assigned for 1,4,9,10- and 2,3,9,10-anthracenetetrone. In addition, NMR data are given for 2,3-dihydroxy-9, 10-anthraquinone, 2,3-dimethoxy-9,10-anthraquinone and 1-hydroxy-2-acetoxy-9,10-anthraquinone, encountered during the preparation of the anthracenetetrones.
- Danielsen,Francis,Aksnes
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p. 1043 - 1045
(2007/10/03)
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- Pulse Radiolytic One-electron Oxidation of some Dihydroxy-substituted Anthraquinones
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The spectroscopic characteristics and the kinetic parameters associated with the transients formed on one-electron oxidation of quinizarin (1,4-dihydroxy-9,10-anthraquinone), quinizarin 2- and 6-sulfonates, 1,5-dihydroxy-9,10-anthraquinone and 1,8-dihydroxy-9,10-anthraquinone have been studied by pulse radiolysis and kinetic spectrophotometric techniques, using OH., O.-, N3., Br2.- and .CH2CHO as the oxidising radicals.The pKa and the disproportionation equilibria of the semi-oxidised quinones have been studied for the water-soluble sulfonates.In contrast to the complex decay of the semi- oxidised naphthazarin (5,8-dihydroxy-1,4-naphthoquinone), the semi-oxidised anthraquinone derivatives decay by simple second-order kinetics.The pKa values of the latter are also much higher (ca. 8) compared to the former (ca. 4).The differences observed are attributed to the loss in symmetry in the free radical structures of the semi-oxidised anthraquinone derivatives.
- Pal, Haridas,,Palit, Dipak K.,Mukherjee, Tulsi,Mittal, Jai P.
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p. 681 - 688
(2007/10/02)
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- Enthalpies of combustion of 1,4-naphthoquinone, 9,10-anthraquinone, 9,10-phenanthraquinone, 1,4,9,10-anthradiquinone, 5,8-dihydroxy-1,4-naphthoquinone, and 1,4-dihydroxy-9,10-anthraquinone
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The standard (p0 = 0.1 MPa) molar enthalpies of combustion in oxygen at 298.15 K were measured by static-bomb calorimetry for some quinones and dihydroxyquinones.The standard molar enthalpies of sublimation at 298.15 K were measured by microcalorimetry for 1,4-naphthoquinone and 9,10-phenanthraquinone; values were selected from the literature for the remaining compounds in order to derive the standard molar enthalpies of formation in the gaseous state. The energies of the intramolecular hydrogen bonds in the dihydroxyquinones were assessed as (25 +/- 3) kJ*mol-1. 1,4,9,10-Anthradiquinone is apparently considerably strained, and although its reaction with water produces 1,4-dihydroxy-9,10-anthraquinone, a concomitant formation of hydrogen peroxide is shown to be thermodynamically improbable.
- Silva, M. A. V. Ribeiro da,Silva, Maria D. M. C. Ribeiro da,Teixeira, J. A. S.,Bruce, J. M.,Guyan, Patricia M.,Pilcher, G.
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p. 265 - 274
(2007/10/02)
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- The Use of 3-Acetoxy-1-trimethylsilylbutadiene in the Synthesis of Anthracyclinone Derivatives
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The Diels-Alder reaction of quinizarin quinone (14) with 3-acetoxy-1-trimethylsilylbutadien (15) affords a tetracyclic adduct, (+/-)-3-acetoxy-1,4,4aα,12aα-tetrahydro-1β-trimethylsilylnaphthacene-5,6,11,12-tetraone (16) in excellent yield.The simultaneous introduction of the C-7 trimethylsilyl substituent in this process allowed later ready conversion into a C-7 acetoxy group by treatment with lead tetra-acetate.The tetracyclic compound (16) was converted in a convenient multistep process into 4-demethoxydaunomycinone (51) in 41percent overall yield from (14).Compound (51) was further elaborated to 14-acetoxy-4-demethoxydaunomycinone (4) by standard reactions, again in good yield (70percent overall).
- Bulman-Page, Philip C.,Ley, Steven V.
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p. 1847 - 1858
(2007/10/02)
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- STUDIES ON QUINONES. XI. SYNTHESIS OF QUINONES FROM HYDROQUINONES BY USING MANGANESE DIOXIDE AND ACID-IMPREGNATED MANGANESE DIOXIDE.
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The preparation of a variety of quinones by oxidation of hydroquinones with manganese dioxide and manganese dioxide impregnated with nitric acid, in methylene chloride solution, is described.
- Cassis, R.,Valderrama, J. A.
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p. 347 - 356
(2007/10/02)
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- Intermediates for polycyclic quinonoid antibiotics
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There is provided a novel method of synthesizing certain tetracyclic quinones. In particular, there is provided a novel route to the synthesis of certain analogs of (+)-7-deoxydaunomycinone which includes the provision of novel tri- and tetracyclic quinone intermediates. The products of the synthetic route provided herein may be converted into compounds of known anti-neoplastic activity.
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