- Rhodium(I)-catalyzed regiospecific dimerization of aromatic acids: Two direct C-H bond activations in water
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2,2'-Diaryl acids are key building blocks for some of the most important and high-performance polymers such as polyesters and polyamides (imides), as well as structural motifs of MOFs (metal-organic frameworks) and biological compounds. In this study, a direct, regiospecific and practical dimerization of simple aromatic acids to generate 2,2'-diaryl acids has been discovered, which proceeds through two rhodium-catalyzed C-H activations in water. This reaction can be easily scaled up to gram level by using only 0.4-0.6 mol% of the rhodium catalyst. As a proof-of-concept, the natural product ellagic acid was synthesized in two steps by this method. On the double: An efficient, regiospecific, and general oxidative dimerization of simple aryl acids to generate diaryl acids was developed. The reaction involves two direct aryl C-H activations catalyzed by rhodium, uses water as the solvent, and can be easily scaled up. The natural product ellagic acid was obtained in only two steps by using this method.
- Gong, Hang,Zeng, Huiying,Zhou, Feng,Li, Chao-Jun
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supporting information
p. 5718 - 5721
(2015/05/19)
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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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p. 8354 - 8360
(2015/09/01)
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- Reductive electrochemical formation of 6H-dibenzo[b,d]pyran-6-one and 2-benzopyran-1(1H)-one
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In the present Letter several carbolactones (oxidative products) are obtained under aprotic cathodic conditions in the preparative scaled electrolysis of 1,2-quinones in a divided electrochemical cell and in the presence of oxygen. When 9,10-phenanthrenequinone is reduced 6H-dibenzo[b,d]pyran-6-one and [1,1′-biphenyl]-2,2′-dicarboxylic acid are obtained as major products. In the reduction of 1,2-naphthoquinone, 2-benzopyran-1(1H)-one, and 2-(2-carboxyethenyl)-benzoic acid were formed as main products. The proposed mechanism to explain the formation of these and other products, that involves an electron-transfer reaction to the oxygen in air, is now discussed.
- Batanero, Belen,Barba, Fructuoso,Barba, Isidoro,Elinson, Michail N.
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- Photocatalysis in dimethyl carbonate green solvent: Degradation and partial oxidation of phenanthrene on supported TiO2
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Dimethyl carbonate (DMC) is here proposed-for the first time-as a green organic solvent for photocatalytic synthesis. In this work, the photocatalytic partial oxidation of phenanthrene in dimethyl carbonate (DMC) by using anatase TiO2as the photocatalyst is described as paradigmatic example of a green synthetic process starting from polycyclic aromatic hydrocarbons (PAHs). For comparison, the same reaction carried out also in ethanol, 1-propanol or 2-propanol is reported. The use of DMC as the solvent allowed us to achieve 19% and 23% selectivity towards 9-fluorenone and 6H-benzo[c]chromen-6-one, respectively. The proposed approach may represent both a new green synthetic process and an environmentally friendly route to degradation of PAHs. This journal is
- Bellardita,Loddo,Mele,Panzeri,Parrino,Pibiri,Palmisano
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p. 40859 - 40864
(2015/01/08)
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- Iron (III) perchlorate adsorbed on silica gel: A reagent for organic functional group transformations
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Adsorption of Fe(ClO4)3(H2O)6 onto chromatographic-grade silica gel in the presence of organic solvents (S=water, acetonitrile, or lower fatty acids) produces a supported reagent, Fe(ClO4)3(S)6/SiO2. This reagent has been found to be effective for the rapid organic functional group transformations such as dimerization of alkynes, aromatic hydrocarbons, selective oxidation of thiols to disulfides, and transannular reactions in 1,5-cyclooctadienes on grinding using pestle and mortar in the solid state. Copyright Taylor & Francis Group, LLC.
- Parmar, Anupama,Kumar, Harish
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p. 2301 - 2308
(2008/02/10)
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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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p. 2151 - 2154
(2007/10/03)
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- Cu(I)(2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane)+ as a catalyst for Ullmann's reaction
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Cu(I)L complexes catalyze the Ullmann reaction 2-BrC6H 4CO2- + H2O → 2-HOC 6H4CO2- + Br- + H + however the process is slow and undesirable yields of benzoic acid and diphenoic acid are formed. The optimal ligand, L, for this catalyst should enhance the rate of the process, probably via shifting the redox potential of the Cu(II/I) couple cathodically, inhibit the formation of the diphenoic acid, probably via steric hindrance, and of benzoic acid probably via buffering the solution at pH > 7. The results demonstrate that Cu(I)(2,5,8,11-tetramethyl- 2,5,8,11tetraazadodecane)+, i.e. Cu(I) with a ligand which fulfils these requirements, is a very good catalyst for this process with a selectivity of > 97% and high turnover numbers. The Royal Society of Chemistry 2003.
- Rusonik, Irena,Cohen, Haim,Meyerstein, Dan
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p. 2024 - 2028
(2007/10/03)
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- PRODUCTION OF AROMATIC CARBOXYLIC ACIDS
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A process for the production of an aromatic carboxylic acid comprising contacting in the presence of a catalyst, within a continuous flow reactor, one or more precursors of the aromatic carboxylic acid with an oxidant, such contact being effected with sai
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- Oxidation of polycyclic aromatic hydrocarbons catalyzed by iron tetrasulfophthalocyanine FePcS: Inverse isotope effects and oxygen labeling studies
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Iron(III) tetrasulfophthalocyanine (FePcS) was shown to catalyze the oxidation of polycyclic aromatic hydrocarbons by H2O2. Benzo[a]pyrene and anthracene were converted to the corresponding quinones while biphenyl-2,2′-dicarboxylic acid was the main product of phenanthrene oxidation. The mechanism of the anthracene oxidation by H2O2 in the presence of FePcS or by KHSO5 with iron(III) mesotetrakis(3,5-disulfonatomesityl)porphyrin (FeTMPS) (see Figure 1 for catalyst structures) has been investigated in details by using kinetic isotope effects (KIEs) and 18O labeling studies. KIEs measured on the substrate consumption in the competitive oxidation of [H10] anthracene and [D10]anthracene by FePcS/H2O2 and FeTMPS/KHSO5 were essentially the same, 0.75 ± 0.02 and 0.76 ± 0.06, respectively. These inverse KIEs on the first oxidation step can be explained by the sp2-to-sp3 hybridization change during the addition of an electrophilic oxoiron complex to the sp2 carbon center of anthracene to form a σ adduct (this inverse KIE being enhanced by stronger slacking interactions between the perdeuterated substrate with the macrocyclic catalyst). Although the first oxidation step seems to be the same, different distribution of the oxidation products of anthracene and very different 18O incorporation into anthrone and anthraquinone in catalytic oxidations performed in the presence of H218O suggested that different active species should be responsible for anthracene oxidation in both catalytic systems. All the results obtained are compatible with an involvement of TMPSFeV=O (or TMPS+FeIV=O), having two redox equivalents above the iron(III) state of the metalloporphyrin precursor, while PcSFeIV=O (one redox equivalent above FeIII state of FePcS) was proposed to be the active species in the metallophthalocyanine-based system.
- Sorokin, Alexander,Meunier, Bernard
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p. 1269 - 1281
(2007/10/03)
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- Iron (III) perchlorate: A novel reagent for functional group as well as ring transformations in organic synthesis
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Oxidative dimerization of some aromatic hydrocarbons, diphenylacetylene and diphenyl amine, selective oxidation of thiols to disulfides, and transformation of 1,5-cyclooctadiene to the corresponding bicyclooctane derivatives through trans-annular reactions have been achieved using iron (III) perchlorate(ITP).
- Kumar, Baldev,Parmar, Anupama,Rajpal, Anita,Kumar, Harish
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p. 593 - 595
(2007/10/03)
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- Generation of Polyphenylene Radical Cations and Their Cosensitization Ability in the 9,10-Dicyanoanthracene-Sensitized Photochemical Chain Reactions of 1,2-Bis(4-methoxyphenyl)cyclopropane
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Cosensitization effects of polyphenylene compounds (PP) such as biphenyl (BP), terphenyls (o-, m-, p-TP), and phenanthrene (Phen) in photoinduced electron-transfer reactions were examined. The 9,10-dicyanoanthracene (DCA)-sensitized cis-trans photoisomerization of 1,2-bis(4-methoxyphenyl)-cyclopropane (CP), which proceeds in a chain reaction via free radical cation of CP (CP.+) as a chain carrier, was accelerated by adding PP, particularly by TP. A similar accelerating effect was observed in the DCA-sensitized photooxygenation of CP as another example. BP and TP were more stable under the oxygenation condition than phenanthrene and naphthalene, which also accelerate the photooxygenation CP. CP.+ is generated by the direct electron transfer from CP to the excited singlet state of DCA (1DCA*) and also by the secondary electron transfer from CP to PP.+, which is generated by the primary electron transfer from PP to 1DCA*. The laser flash photolysis study revealed that the quantum yield for the formation of free CP.+ in the direct electron transfer from CP to 1DCA* (ΦCP.+ ≈ 0.1) was smaller than that in the presence of PP. This is due to the high yield of free PP.+ generation by the primary electron transfer and the efficient secondary electron transfer from CP to PP.+. The secondary electron transfers were found to take place in nearly diffusion-controlled rates (0.9-1.5 × 1010 M-1 s-1). The high yield of PP.+ as free radical ions does not seem to be the sole factor of the cosensitization of PP for the DCA-sensitized photoreactions of CP. The ratio of the quantum yields of the photoreactions to that of the initial CP.+ formation (turnover) also increased by the addition of PP from 3 (isomerization) and 15 (oxygenation) to 32-90 for both reactions. The second-order rate constant for the decay of CP.+ in aerated acetonitrile was decreased by a factor of 0.5-0.8 by the addition of PP. We concluded that the cosensitization effect in the photoreaction involves a π-complex formation between CP.+ and PP assisting the chain reaction as well as initial CP.+ formation.
- Tamai, Toshiyuki,Ichinose, Nobuyuki,Tanaka, Tomoko,Sasuga, Tsuneo,Hashida, Isao,Mizuno, Kazuhiko
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p. 3204 - 3212
(2007/10/03)
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- Photochemical oxidation of phenanthrene sorbed on silica gel
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There have been relatively few detailed studies of PAH photochemical degradation mechanisms and products at solid/air interfaces under controlled conditions. Results from mechanistic studies on particulate simulants are important in understanding the fates of PAH sorbed on similar materials in natural settings. In this study, the photolysis of phenanthrene (PH) on silica gel, in the presence of air, has been carefully examined. Once sorbed onto the silica surface, PH is not observed to repartition into the gas phase, even under vacuum, and dark reactions of PH are not observed at the silica/air interface. Photolysis (254 nm) of PH leads to the formation of 2,2'-biformylbiphenyl (1), 9,10-phenanthrenequinone (2), cis-9,10-dihydrodihydroxyphenanthrene (3), benzocoumarin (4), 2,2'-biphenyldicarboxylic acid (5), 2-formyl-2'-biphenylcarboxylic acid (5), 2-formylbiphenyl (7),1,2-naphthalenedicarboxylic acid (8), and phthalic acid (9). These products account for 85-90% of the reacted PH. The photoproducts are independent of excitation wavelength (254 and 350 nm), and the reaction proceeds entirely through an initial step involving the addition of singlet molecular oxygen to the ground state of phenanthrene with subsequent thermal and/or photochemical reactions of the initially formed product. Singlet molecular oxygen is produced through quenching of the lowest triplet state of PH at the silica gel/air interface. The high material balance and detailed mechanistic information provided by this study serve as a standard for comparisons with the products and mechanism of PH photochemical oxidation on environmentally derived inorganic oxide particulates.
- Barbas, John T.,Sigman, Michael E.,Dabestani, Reza
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p. 1776 - 1780
(2007/10/03)
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- PHOTODEGRADATION OF PHENANTHRENE IN THE PRESENCE OF HUMIC SUBSTANCES AND HYDROGEN PEROXIDE
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The photodegradation of phenanthrene in water was investigated for a variety of reaction conditions employing various fulvic acids (FAs) as photosensitizers and hydrogen peroxide as oxidant. All experiments were conducted by using artificial sunlight from Suntest apparatus (Hanau, Germany) as light source. The relative rates of phenanthrene photodegradation for the different experimental conditions were computed. Fulvic acids of different origins influenced the rate of sunlight-induced photodegradation of phenanthrene in different ways. Hydrogen peroxide vigorously enhanced the photodegradation rate of phenanthrene. The photoproducts identified were oxygenated products of aromatic ring, such as 9,10-phenanthrenquinone, a group of hydroxyphenanthrene with hydroxyl at different position (1, 3, 4, and 9), 2,2'biphenyldicarbonic acid, 2,2'-biphenyldialdehyde and 2-phenylbenzaldehyde. It can be consumed that the phenanthrene photodegraded via free radical mechanism. - Keywords: Phenanthrene; Photodegradation; Fulvic Acids; Hydrogen Peroxide; Interaction
- Wang, C. X.,Yediler, A.,Peng, A.,Kettrup, A.
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p. 501 - 510
(2007/10/03)
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- The Red Membrane Pigments of the Peat Moss Sphagnum rubellum
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The red colour of the peat moss Sphagnum rubellum results from three membrane pigments, the sphagnorubins A, B, and C; they have been isolated and their structures elucidated.Sphagnorubin A (1) is identical with the formerly known sphagnorubin obtained from Sphagnum magellanicum.Sphagnorubin B (3) was identificated as 2-(3',4'-dihydroxyphenyl)-8,9-dihydroxy-11-methoxyphenanthropyrylium chloride.Sphagnorubin C (7) is the 3'-methyl ether of sphagnorubin B.
- Mentlein, Rolf,Vowinkel, Erich
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p. 1024 - 1035
(2007/10/02)
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- MECHANISM OF THE PHOTOOXIDATION OF AND PHOTOEPOXIDATION WITH CYCLIC alpha -DIKETONES.
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The photooxidation of phenanthrenequinone (PhQ) under oxygen afforded diphenic acid and its peroxy acid, while acenaphthenequinone (AcQ) predominantly yielded 1,8-naphthalenedicarboxylic anhydride. The photolysis of PhQ or AcQ in the presence of olefins afforded predominantly 1:1 cycloadducts and the photoepoxidation was a very minor one accompanying significant amount of C-C clevage of olefins. These results show that the photoreaction of PhQ or AcQ with olefins is very fast and competitive with the quenching and/or reaction with oxygen. The photoepoxidation of stilbene in the presence of dimethyl sulfoxide resulted in a high selectivity ( greater than 98%) for the trans-epoxide.
- Sawaki
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p. 3464 - 3470
(2007/10/02)
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