- 2-Bromoanthraquinone as a highly efficient photocatalyst for the oxidation ofsec-aromatic alcohols: experimental and DFT study
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Anthraquinones are recognized as high efficiency photocatalysts which can perform various redox reactions in aqueous or organic phases. We have experimentally proven that 2-BrAQ can undergo hydrogen transfer with an alpha-aromatic alcohol under light conditions, thereby efficiently oxidizing the aromatic alcohol to the corresponding product. The yield of 1-phenethanol to acetophenone can reach more than 96%. In subsequent catalyst screening experiments, it was found that the electronegativity of the substituent at the 2 position of the anthraquinone ring and the acidity of the solvent affect the photocatalytic activity of anthraquinones. After using various aromatic alcohol substrates, 2-BrAQ showed good conversion and selectivity for most aromatic alcohols, but showed C-C bond cleavage and low selectivity with non-α-position aromatic alcohols. In order to explore the mechanism of the redox reaction of 2-BrAQ in acetonitrile solution, the corresponding free radical reaction pathway was proposed and verified by density functional theory (DFT). Focusing on calculations for 2-BrAQ during the reaction and the first-step hydrogen transfer reaction between the 2-BrAQ triplet molecule and the 1-phenylethanol molecule, we recognized the changes that occurred during the reaction and thus have a deeper understanding of the redox reaction of anthraquinone compounds in organic systems.
- Chen, Guanghui,Liao, Shengfu,Liu, Jianguo,Liu, Qiying,Ma, Longlong,Yan, Long
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p. 37014 - 37022
(2020/10/27)
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- Synthesis of polyfluoroaromatic ketones from polyfluoroarylzinc compounds and acyl chlorides in the presence of CuCl
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Polyfluoroaromatic ketones ArFCOAlk and ArFCOPh (ArF = C6F5, 3- and 4-F3CC 6F4, 4-NCC6F4, 4-EtOCOC 6F4, C5F
- Vinogradov,Krasnov,Platonov
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experimental part
p. 344 - 351
(2010/09/12)
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- Aryl palladium carbene complexes and carbene-aryl coupling reactions
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Transmetalation of an aminocarbene moiety from [W(CO) 5{C(NEt2)R}] to palladium leads to isolable monoaminocarbene palladium aryl complexes [{Pd(μ-Br)Pf[C(NEt 2)R]}2] (R = Me, Ph; Pf = C6F5). When [W(CO)5{C(OMe)R}] is used, the corresponding palladium carbenes cannot be isolated since these putative, more electrophilic carbenes undergo a fast migratory insertion process to give alkyl palladium complexes. These complexes could be stabilized in the η3-allylic form for R = 2-phenylethenyl or in the less stable η3-benzylic fashion for R = Ph. Hydrolysis products and a pentafluorophenylvinylic methyl ether (when R = Me) were also observed. The monoaminocarbenes slowly decompose through carbene-aryl coupling to produce the corresponding iminium salts and, depending on the reaction conditions, the corresponding hydrolysis products. The electrophilicity of the carbene carbon, which is mainly determined by the nature of the heteroatom group, controls the ease of evolution by carbene-aryl coupling. Accordingly, no carbene-aryl coupling was observed for a diaminocarbene palladium aryl complex.
- Albeniz, Ana C.,Espinet, Pablo,Manrique, Raul,Perez-Mateo, Alberto
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p. 1565 - 1573
(2007/10/03)
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- Formation of radical anions on the reduction of carbonyl-containing perfluoroaromatic compounds in aqueous solution: A pulse radiolysis study
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Radical anions are formed on addition of hydrated electrons to pentafluoroacetophenone (PFA) and pentafluorobenzaldehyde (PFB) in aqueous solutions. On the other hand, addition of hydrated electrons to pentafluorobenzoic acid (PFBA) leads to rapid fluoride elimination. The spectrum of the radical anion of PFA has λmax at 300 and 440 nm with absorption coefficient at 440 nm ε440 = 2100 L mol-1 cm-1. PFA?- decays with a rate constant of (7 ± 3.0) × 103 s-1. It has a pKa = 7.5 and the spectrum of the conjugate acid has λmax at 270 and 460 nm with ε460 = 900 L mol-1 cm-1. The spectrum of the radical anion of PFB has λmax at 285 and 430 nm with ε430 = 800 L mol-1 cm-1. PFB?- decays with a rate of (4 ± 2) × 103 s-1. It has a pKa = 7.2 and the spectrum of the conjugate acid has weak absorption at 330 nm. Evidence for the formation of the radical anion was obtained from intermolecular electron transfer from the radical anions of PFA and PFB top-benzoquinone (Q), methyl viologen (MV2+), and 9,10-anthraquinone-2-sulfonate (AQS-). Strong reductants derived from reduction of 2,2-bipyridine (BpyH?) and 1,10-phenanthroline (PhenH?) can reduce both PFA and PFB. From the kinetics of these electron transfer reactions the reduction potentials of PFA and PFB have been determined to be -0.86 ± 0.1 and -0.75 ± 0.1 V vs NHE at pH 9.4. Addition of OH? radical to the aromatic ring of these fluorinated compounds led to rapid HF elimination and the formation of phenoxyl radicals, and addition of H? atoms led to the formation of cyclohexadienyl radical.
- Shoute, Lian C. T.,Mittal, Jai P.
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p. 14022 - 14027
(2007/10/03)
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- Reactivity of Negative Ions with Trifluoromethyl Halides
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The kinetics of the reactions of selected anions (A(-)) with the trifluoromethyl halides CF3X (X = F, Cl, Br, I) in the gas phase were measured at 300 K.Reaction rate constants and product branching fractions were determined using a selected ion flow tube (SIFT) instrument.The chosen anions were C5F5N(-), o-, m-, and p-CF3C6H4CN(-), C6F5Br(-), C6F5Cl(-), C6F5CF3(-), C6F5COCH3(-), Fe(-), FeCO(-), SF6(-), SO(-), SO2(-), NO(-), NO2(-), and NO3(-).The reactivity of these systems varies from unreactive to collisional, and a variety of reaction types was found.The results of our present and previous measurements on A(-) + CF3X reactions show that, in cases where nondissociative electron transfer (NDET) is energetically allowed, the total reactivity tends to be high, approaching collisional.This suggests that reactivity in these cases is initiated and controlled by electron transfer from the anion.In addition, association reactions tend to be preempted when NDET is energetically allowed.A few exceptions to these tendencies were found and are discussed.
- Morris, Robert A.,Viggiano, A. A.,Miller, Thomas M.,Seeley, John V.,Arnold, Susan T.,et al.
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p. 10641 - 10645
(2007/10/03)
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- KINETICS OF REACTION OF DIALKYL PHOSPHITES WITH α-HALOACETOPHENONES
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The reaction of dialkyl phosphites with α-haloacetophenones is described by a second-order equation.The rate of the reaction is mainly influenced by the nature and number of halogen atoms in the molecule of the initial haloacetophenone.A radical mechanism is proposed.
- Maslennikov, I. G.,Matus, L. I.,Lavrent'ev, A. N.
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p. 890 - 891
(2007/10/02)
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- FLUORINE CONTAINING BIOACTIVE HETEROCYCLES PART III : SYNTHESIS OF SOME NEW FLUORINE CONTAINING PHENYLGLYOXALS AND 1,2,4-TRIAZINE DERIVATIVES
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Some medicinally important new fluorine containing phenylglyoxals have been synthesized by selenium dioxide oxidation of appropriate fluorinated acetophenones and characterized by spectrum studies.The phenylglyoxals were treated with thiosemicarbazide to give corresponding thiosemicarbazones (III) which were cyclized, in situ, to yield 5-(fluorophenyl)-1,2,4-triazine-3(2H)-thiones.The 5-(4-fluorophenyl)-1,2,4-triazine-3-(2H)-thione (IV) undergoes nucleophilic displacement when refluxed with hydrazine hydrate to give corresponding 3-hydrazino-5-(4-fluorophenyl)-1,2,4-tria zine.The hydrazino derivative reacts with fluorinated 1,3-diketones, in glacial acetic acid yielding 5-(4-fluorophenyl)-3--1,2,4-triazines (VII).All synthesized compounds have been characterized on the basis of elemental analyses, ir, pmr and 19F nmr studies.
- Joshi, Krishna C.,Dubey, Kalpana,Dandia, Anshu
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p. 1545 - 1553
(2007/10/02)
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