- External Oxidant-Dependent Reactivity Switch in Copper-Mediated Intramolecular Carboamination of Alkynes: Access to a Different Class of Fluorescent Ionic Nitrogen-Doped Polycyclic Aromatic Hydrocarbons
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An interesting case of external oxidant-controlled reactivity switch leading to a divergent set of ionic nitrogen-doped polycyclic aromatic hydrocarbons (N-doped PAHs), is presented here, which is quite unrecognized in copper-mediated reactions. In the current scenario, from the same pyridino-alkyne substrates, the use of the external oxidant PhI(OAc)2, in combination with Cu(OTf)2, gave N-doped spiro-PAHs via a dearomative 1,2-carboamination process; whereas, without the use of oxidant, an alkyne/azadiene [4 + 2]-cycloaddition cascade occurred to exclusively afford ionic N-doped PAHs. These newly synthesized N-doped PAHs further exhibit tunable emissions, as well as excellent quantum efficiencies.
- Shaikh, Aslam C.,Banerjee, Somsuvra,Mule, Ravindra D.,Bera, Saibal,Patil, Nitin T.
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- Secondary phosphine oxide-triggered selective oxygenation of a benzyl ligand on palladium
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The oxygenation of a benzyl ligand in [PdBnCl(cod)] was dramatically accelerated by using secondary phosphine oxides (SPOs), selectively affording either BnOOH or BnOH, depending on the concentration of O2. The SPOs coordinate to palladium in the form of phosphinous acids, operating as Br?nsted acids to facilitate further reaction with O2. This journal is
- Oka, Sayaka,Shigehiro, Yuma,Kataoka, Yasutaka,Ura, Yasuyuki
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supporting information
p. 12977 - 12980
(2020/11/05)
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- Indium-Mediated Synthesis of Benzylic Hydroperoxides
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An indium(0)-metal-mediated efficient synthesis of benzylic hydroperoxides is described. The reaction proceeds efficiently with a broad range of benzyl bromides under aerobic conditions at room temperature to afford benzyl hydroperoxides in good to excellent yields. In addition, the tandem hydroperoxidation-Michael addition of (E)-1-(bromomethyl)-2-(2-nitrovinyl)benzene was also demonstrated.
- Hou, Yuxuan,Hu, Jinjin,Xu, Ruigang,Pan, Shulei,Zeng, Xiaofei,Zhong, Guofu
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supporting information
p. 4428 - 4432
(2019/06/17)
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- Oxygenation of a benzyl ligand in SNS-palladium complexes with O2: Acceleration by anions or Br?nsted acids
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A cationic SNS-benzylpalladium complex was reacted with O2 under several conditions, affording oxygenated compounds derived from the benzyl ligand. The addition of n-Bu4NX remarkably accelerated the oxygenation, furnishing benzaldehyde as a main organic product and dinuclear complexes; in contrast, HX also promoted the oxygenation, but mainly produced benzyl hydroperoxide and mononuclear complexes.
- Shimokawa, Reina,Kawada, Yumi,Hayashi, Miki,Kataoka, Yasutaka,Ura, Yasuyuki
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supporting information
p. 16112 - 16116
(2016/10/31)
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- Synthesis of alkyl hydroperoxides via alkylation of gem -dihydroperoxides
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2-Fold alkylation of 1,1-dihydroperoxides, followed by hydrolysis of the resulting bisperoxyacetals, provides a convenient method for synthesis of primary and secondary alkyl hydroperoxides.
- Kyasa, Shivakumar,Puffer, Benjamin W.,Dussault, Patrick H.
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p. 3452 - 3456
(2013/06/26)
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- Method for oxidizing hydrocarbons
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The invention relates to a method for oxidizing substrates such as hydrocarbons, waxes or soot. The method involves the use of a compound of formula (I) in which: R1 and R2 represent H, an aliphatic or aromatic alkoxy radical, carboxyl radical, alkoxycarbonyl radical or hydrocarbon radical, each having 1 to 20 hydrocarbon atoms, SO3H, NH2, OH, F, Cl, Br, I and/or NO2, whereby R1 and R2 designate identical or different radicals or R1 and R2 can be linked to one another via a covalent bonding; Q1 and Q2 represent C, CH, N, CR5, each being the same or different; X and Z represent C, S, CH2, each being the same or different; Y represents O and OH; k=0, 1, 2; l=0, 1, 2; m=1 to 3, and; R5 represents one of the meanings of R1. Said compound is used as a catalyst in the presence of a radical initiator, whereby the molar ratio of the catalyst to the hydrocarbon is less than 10 mol %. Peroxy compounds or azo compounds can be used as the radical initiator. Preferred substrates are aliphatic or aromatic hydrocarbons.
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- The oxidation of ethylbenzene and other alkylaromatics by dioxygen catalysed by iron(III) tetrakis(pentafluorophenyl)porphyrin and related iron porphyrins
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The oxidation of ethylbenzene with dioxygen catalysed by iron(III) porphyrins in a solvent free system has been studied over the temperature range 30-110°C. The time dependence of the formation of the three main products, 1-phenylethanol, acetophenone and 1-phenylethyl hydroperoxide, and the fate of the iron porphyrin are interpreted in terms of a free radical autoxidation mechanism. The yields of the oxidation products are determined by the rate of reaction and by the lifetime of the catalyst. Catalyst degradation is shown to involve reaction of the porphyrin ligand with 1-phenylethoxyl and 1-phenylethylperoxyl radicals. The disadvantages of increased induction periods and longer reaction times of the oxidations observed at lower reaction temperatures are counter balanced by increased catalyst turnovers. Less extensive studies on the oxidations of toluene, cumene, (2-methylpropyl)-benzene and tert-butylbenzene support the overall mechanism proposed for ethylbenzene. A comparative study using the catalysts iron(III) 2,3,7,8,12,13,17,18-octachloro-5,10,15,20-tetrakis-(2,6-dichlorophenyl)porphyrin and iron(III) tetrakis(pentafluorophenyl)porphyrin and five of its derivatives reveals that halogenation of the β-pyrrole positions markedly increases the activity of the catalysts but not the stability of the porphyrin towards degradation. The highest yields were obtained with the μ-oxodimer of iron(III) tetrakis(pentafluorophenyl)porphyrin and iron(III) tetrakis(4-dimethylamino-2,3,5,6-tetrafluorophenyl)-porphyrin.
- Evans, Steven,Smith, John R. Lindsay
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p. 1541 - 1551
(2007/10/03)
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- Methyltrioxorhenium catalyzed oxidation of saturated and aromatic hydrocarbons by H2O2 in air
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Alkanes (cyclohexane, cyclooctane, n-heptane) and aromatic compounds (benzene, toluene, and ethylbenzene) are oxidized by anhydrous H2O2 in MeCN in air in the presence of catalytic amounts of MTO. The reaction in accelerated by addition of pyrazine-2-carboxylic acid. Alkanes give alkyl hydroperoxides as main products, as well as alcohols and ketones. Arenes yield predominantly phenols.
- Schuchardt, Ulf,Manddli, Dalmo,Shul'Pin, Georgiy B.
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p. 6487 - 6490
(2007/10/03)
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- Mikroporoese Mischoxide - Katalysatoren mit einstellbarer Oberflaechenpolaritaet
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Keywords: Katalyse; Mischoxide; Oxidationen; Siliciumverbindungen; Titanverbindungen
- Klein, Stephan,Maier, Wilhelm F.
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p. 2376 - 2379
(2007/10/03)
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- A Kinetic and Mechanistic Study of the Self-Reaction and Reaction with H2O of the Benzylperoxy Radical
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The kinetics and mechanism of the reactions C6H5CH2O2 + C6H5CH2O2 -> 2C6H5CH2O + O2 (3a), C6H5CH2O2 + C6H5CH2O2 -> C6H5CHO + C6H5CH2OH + O2 (3b), and C6H5CH2O2 + HO2 -> C6H5CH2OOH + O2 (4) have been investigated using two complementary techniques: flash photolysis/UV absorption for kinetic measurements and continuous photolysis/FTIR spectroscopy for end-product analyses and branching ratio determinations.The reaction of chlorine atoms with toluene was found to yield benzyl radicals exclusively and was used to generate benzylperoxy radicals in excess oxygen.During this study, relative reaction rate constants of chlorine atoms with compounds related to those involved in the reaction mechanism have been measured at room temperature: k(Cl+toluene) = (6.1 +/- 0.2)E-11, k(Cl+benzaldehyde) = (9.6 +/- 0.4)E-11, k(Cl+benzyl chloride) = (9.7 +/- 0.6)E-12, k(Cl+benzyl alcohol) = (9.3 +/- 0.5)E-11, k(Cl+benzene) 3 molecule-1 s-1.The products identified following the self-reaction 3 were benzaldehyde, benzyl alcohol, and benzyl hydroperoxide.The latter is the product of the reaction of C6H5CH2O2 with HO2.The yield of products allowed us to determine the branching ratio α = k3a/k3 = 0.4.The UV absorption spectrum of the benzylperoxy radical was determined from 220 to 300 nm.It was similar to those of alkylperoxy radicals, with a maximum cross section at 245 nm of 6.8E-18 cm2 molecule-1.Kinetic data were obtained from the detailed simulation of experimental decay traces recorded at 250 nm over the temperature range 273-450 K.The resulting rate expression are k3 = (2.75 +/- 0.15)E-14 exp cm3 molecule-1 a-1 and k4 = (3.75 +/- 0.32)E-13 exp3 molecule-1 s-1 (errors = 1?).The UV absorption traces in the flash-photolysis kinetic study were well accounted for by the identified products in the FTIR study, thus providing good confidence in the results.However, about 20percent of the products have remained unidentified.Some uncertainties persist in the reaction mechanism leading us to assign a fairly large uncertainty of about 50percent to the rate constants k3 and k4 over the whole temperature range.This work shows that the aromatic substituent does not provide any specificity in the reactivity of peroxy radicals and confirms that large radicals tend to react faster with HO2 than generally assumed in current atmospheric models.
- Noziere, Barbara,Lesclaux, Robert,Hurley, Michael D.,Dearth, Mark A.,Wallington, Timothy J.
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p. 2864 - 2873
(2007/10/02)
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- Self-Reaction of Benzylperoxy Radicals in the Oxidation of Toluene. A Chemiluminescence and Product Study
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The CL study of the oxidation of toluene initiated by AIBN has shown that both triplet and singlet benzaldehyde is formed (T/S ca. 10.5).The lifetimes in toluene are: τS ca. 4*10-9 s and τT ca. 1.9*10-7 s. - In the presence of DPA the kinetic curve of the CL light shows a maximum at above 10-4 M.The CL spectrum of the oxidation of toluene lacks both the fluorescence and phosphorescence peaks of the excited benzaldehyde (due to the very low efficiency of photon emission and very strong quenching by O2 and toluene). - Analysis of product distribution by HPLC revealed the formation of benzaldehyde, benzylalcohol, benzylhydroperoxide and benzoic acid.A small amount of H2O2 was also detected by spectrophotometry.Since the ratio of aldehyde/alcohol is always higher than unity detailed study of all circumstances led as to the conclusion that benzylperoxy radicals terminate both by the Russell-mechanism and by the transition state containing two five-membered rings suggested by Bennett and Summers. - The activation energy of hydrogen abstraction from toluene by benzylperoxy radicals is 53 kJ/mol and the rate constant of this reaction does not differ essentially from the same reaction of ethylbenzene.The kinetic chain length of oxidation calculated from the analytical data is equal to 2 +/- 0.2 (75-90 deg C).
- Vasvari, G.,Gal, D.
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- Electron-transfer processes in the electrophilic cleavage of cobalt-carbon bonds of alkylcobalt(III) complexes with iodine
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Contribution of the electron-transfer processes in the cleavage of cobalt-carbon bonds of alkylcobalt(III) complexes cis-[R2Co(bpy)2]+ (R = Me, Et, PhCH2; bpy = 2,2′-bipyridine), trans-[Me2Co(DpnH)] (DpnH = 11-hydroxy-2,3,9,10-tetramethyl-1,4,8,11-tetraazaundeca-1,3,8,10-tetraen-1- olate), and [RCo(DH)2py] (R = Me, Et, PhCH2; (DH)2 = bis(dimethylglyoximato); py = pyridine) with iodine has been studied by detecting the products that could arise only via electron-transfer processes as well as by the kinetic comparison between the electrophilic reactions of iodine with alkylcobalt(III) complexes and the electron-transfer reactions of iodine with ferrocene derivatives in acetonitrile. The coupling products of alkyl groups of dialkylcobalt(III) complexes, derived from the corresponding dialkylcobalt(IV) complexes, are obtained in the cleavage reactions of dialkylcobalt(III) complexes with iodine, with alkyl iodides being the main products. The observed second-order rate constants for the cleavage reactions of alkylcobalt(III) complexes with iodine in acetonitrile at 298 K are compared with those of electron transfer from ferrocene derivatives to iodine, based on the Marcus theory of electron transfer.
- Ishikawa, Kunio,Fukuzumi, Shunichi,Tanaka, Toshio
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p. 1661 - 1665
(2008/10/08)
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- Rate Constants for Reduction of substituted Methylperoxyl Radicals by Ascorbate Ions and N,N,N',N'-tetramethyl-p-phenylenediamine
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Absolute rate constants (k) for reduction of substituted methylperoxyl radicals by ascorbate ions and by TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine) in aqueous solutions have been determined by pulse radiolysis.The rate constants vary from 1E6 to 1E9 M-1 s-1, increasing as the electron-withdraving capacity of the substituent on the peroxyl group increases.Linear correlations are observed between log k and the Taft substituents ?* for a wide variety of substituents, but not all substituents fit the same line.In the case of ascorbate as reductant, the points for peroxyl radicals that contain halogens on the α-carbon lie on a different line (ρ*=0.41) than that for the other substituents (ρ*=1.25).In the case of TMPD there are alsotwo families of peroxyl radicals: Those comprimising the electron-donating groups Me through t-Bu (ρ=5.6) and those containing electron-withdrawing substituents (ρ*=0.64).
- Neta, P.,Huie, R. E.,Mosseri, S.,Shastri, L. V.,Mittal, J. P.,et al.
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p. 4099 - 4104
(2007/10/02)
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- Coenzyme-Catalyzed Cleavage of Cobalt-Carbon Bonds in the Oxidation of cis-Dialkylcobalt(III) Complexes by Oxygen
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Redox coenzyme analogues (riboflavin, aminopterin, and lumazine) catalyze the cleavage of cobalt-carbon bonds in the oxidation of cis-dialkylcobalt(III) complexes, cis-ClO4 (R = PhCH2, C2H5, CH3; bpy = 2,2'-bipyridine) by oxygen in the presenc
- Fukuzumi, Shunichi,Goto, Tatsushi,Ishikawa, Kunio,Tanaka, Toshio
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p. 1923 - 1926
(2007/10/02)
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- CERIUM (IV) AMMONIUM NITRATE CATALYSED PHOTOCHEMICAL AUTOXIDATION OF ALKYLBENZENES
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The autoxidation of alkylbenzenes can be promoted photochemically in the presence of catalytic amounts of cerium (IV) ammonium nitrate (CAN) under very mild conditions, the efficiency of the process being significantly increased by added acids.It is suggested that the reaction is promoted by NO3 radicals formed in the light induced decomposition of CAN and that Ce(III) may be reoxidized to Ce(IV) by benzylperoxy radicals.
- Baciocchi, E.,Giacco, T. Del,Sebastiani, G. V.,Rol, C.
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p. 3353 - 3356
(2007/10/02)
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