1129-21-1Relevant articles and documents
IBS-catalyzed regioselective oxidation of phenols to 1,2-quinones with oxone
Uyanik, Muhammet,Mutsuga, Tatsuya,Ishihara, Kazuaki
, p. 8604 - 8616 (2012)
We have developed the first example of hypervalent iodine(V)-catalyzed regioselective oxidation of phenols to o-quinones. Various phenols could be oxidized to the corresponding o-quinones in good to excellent yields using catalytic amounts of sodium salts of 2-iodobenzenesulfonic acids (pre-IBSes) and stoichiometric amounts of Oxone as a co-oxidant under mild conditions. The reaction rate of IBS-catalyzed oxidation under nonaqueous conditions was further accelerated in the presence of an inorganic base such as potassium carbonate (K2CO3), a phase transfer catalyst such as tetrabutylammonium hydrogen sulfate (nBu4NHSO4), and a dehydrating agent such as anhydrous sodium sulfate (Na2SO4).
Bioinspired Mo, W and V complexes bearing a highly hydroxyl-functionalized Schiff base ligand
Salonen, Pasi,Peuronen, Anssi,Lehtonen, Ari
, (2020)
A series of bioinspired dioxidomolybdenum(VI), dioxidotungsten(VI) and oxidovanadium(V) complexes [MoO2(H2LSaltris)], [WO2(H2LSaltris)] and [VO(HLSaltris)]2 were prepared by the reaction of a hydroxyl-rich Schiff base proligand N-(1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl)-3,5-di-tert-butylsalicylaldimine (H4LSaltris) with metal precursors in methanol solutions. Molybdenum and tungsten complexes crystallize as mononuclear molecules, whereas the vanadium complex forms dinuclear units. From the complexes, [VO(HLSaltris)]2 shows activity in the oxidation of 4-tert-butylcatechol and 3,5-di-tert-butylcatechol, mimicking the action of the dicopper enzyme catechol oxidase.
Bis-benzimidazolyl diamide copper (II) complexes: Synthesis, crystal structure and oxidation of substituted amino phenols
Ahuja, Gauri,Mathur, Pavan
, p. 42 - 48 (2012)
A new tetradentate ligand N,N′-Bis (1-butyl-benzimidazol-2-yl-methyl) -hexane-1,6-dicarboxamide (b-GBSA) has been utilized to synthesize mononuclear copper (II) complexes with inner sphere anionic ligands like NO3 -, Br- and Cl-. Two of the complexes [Cu(L)NO3]NO3 (1) and [Cu(L)Br]Br (2) have been structurally characterized. The geometry of copper (II) in (1) is a distorted octahedral with NO3- anion acting as a bidentate ligand, while for (2) the geometry is found to be a near square pyramidal. The complexes carry out the oxidation of substituted amino phenols in the presence of molecular oxygen. The oxidation gets blocked at the dihydrophenoxazinone stage for 2-amino-5-methyl phenol, and to o-quinone for 2-amino-4-tertiary butyl phenol, quite like the enzyme phenoxazinone synthase.
A Biomimetic Mechanism for the Copper-Catalyzed Aerobic Oxygenation of 4-tert-Butylphenol
Askari, Mohammad S.,Esguerra, Kenneth Virgel N.,Lumb, Jean-Philip,Ottenwaelder, Xavier
, p. 8665 - 8672 (2015)
Controlling product selectivity during the catalytic aerobic oxidation of phenols remains a significant challenge that hinders reaction development. This work provides a mechanistic picture of a Cu-catalyzed, aerobic functionalization of phenols that is selective for phenoxy-coupled ortho-quinones. We show that the immediate product of the reaction is a Cu(II)-semiquinone radical complex and reveal that ortho-oxygenation precedes oxidative coupling. This complex is the resting state of the Cu catalyst during turnover at room temperature. A mechanistic study of the formation of this complex at low temperatures demonstrates that the oxygenation pathway mimics the dinuclear Cu enzyme tyrosinase by involving a dinuclear side-on peroxodicopper(II) oxidant. Unlike the enzyme, however, the rate-limiting step of the ortho-oxygenation reaction is the self-assembly of the oxidant from Cu(I) and O2. We provide details for all steps in the cycle and demonstrate that turnover is contingent upon proton-transfer events that are mediated by a slight excess of ligand. Finally, our knowledge of the reaction mechanism can be leveraged to diversify the reaction outcome. Thus, uncoupled ortho-quinones are favored in polar, coordinating media, highlighting unusually high levels of chemoselectivity for a catalytic aerobic oxidation of a phenol. (Chemical Equation Presented).
Aerobic Oxidation of Dihydroxyarenes Substrates Catalyzed by Polymer-Supported RuII-Pheox/Silica-Gel: A Beneficial Route for Purification of Industrial Water
Abu-Elfotoh, Abdel-Moneim
supporting information, p. 236 - 243 (2022/04/09)
A broad class of dihydroxyarenes were easily oxidized by aerobic oxygen to quinone products in excellent yields under the catalytic effect of polymer-supported RuII-Pheox/silica-gel catalyst. By using this combined catalyst, hydroquinone and catechol derivatives with electron-donating groups were easily oxidized by molecular oxygen to quinone products in 90% to >99% yield, while in the case of electron-withdrawing group, only 70% was obtained. The biologically useful 1,4-Naphthoqinone products were obtained in 83% to 90%. The catalyst was easily obtained and reused many times without a significant decrease in reactivity. Interestingly, a sample of industrial water contaminated with phenolic compounds was subjected to aerobic oxidation by using this catalyst, and the resultant quinones were detected within one day and the catalyst was removed and reused several times with different contami-nating samples with the same efficiency. Other catalytic oxidations by using this promising catalyst were investigated.
Nickel(II) complex based on bis-(1-(pyridin-2-yl-methyl)-benzimidazol-2-yl-methyl) ether and its utilization in the oxidation of 2-amino-4-tert-butylphenol
Khattar, Raghvi,Yadav, Anjana,Mahiya, Kuldeep,Mathur, Pavan
, p. 36 - 42 (2017/08/04)
A mononuclear nickel(II) complex [Ni(L)2].(NO3)2.H2O is synthesized utilizing a bis-benzimidazolyl ligand (L = bis-(1-(pyridin-2-yl-methyl)-benzimidazol-2-yl-methyl)ether) and characterized by single-crystal X-ray diffraction, elemental analysis, UV-vis and IR spectroscopy. Ni(II) complex crystallizes in the tetragonal system with space group I41/a and appears to be propeller-shaped when viewed along the c-axis. The [Ni(L)2].(NO3)2 complex has been utilized for the oxidation for 2-amino-4-tert-butylphenol to 4-tert-butyl-o-benzoquinone in the presence of hydrogen peroxide and the average rate of reaction is calculated to be 63×10–7 M min–1. The presence of externally added acetate ion tends to inhibit the rate of reaction.
Controlling the catalytic aerobic oxidation of phenols
Esguerra, Kenneth Virgel N.,Fall, Yacoub,Petitjean, Laurène,Lumb, Jean-Philip
supporting information, p. 7662 - 7668 (2014/06/10)
The oxidation of phenols is the subject of extensive investigation, but there are few catalytic aerobic examples that are chemo- and regioselective. Here we describe conditions for the ortho-oxygenation or oxidative coupling of phenols under copper (Cu)-catalyzed aerobic conditions that give rise to ortho-quinones, biphenols or benzoxepines. We demonstrate that each product class can be accessed selectively by the appropriate choice of Cu(I) salt, amine ligand, desiccant and reaction temperature. In addition, we evaluate the effects of substituents on the phenol and demonstrate their influence on selectivity between ortho-oxygenation and oxidative coupling pathways. These results create an important precedent of catalyst control in the catalytic aerobic oxidation of phenols and set the stage for future development of catalytic systems and mechanistic investigations.
Air oxygenation chemistry of 4-TBC catalyzed by chloro bridged dinuclear copper(ii) complexes of pyrazole based tridentate ligands: Synthesis, structure, magnetic and computational studies
Banerjee, Ishita,Samanta, Pabitra Narayan,Das, Kalyan Kumar,Ababei, Rodica,Kalisz, Marguerite,Girard, Adrien,Mathonière, Corine,Nethaji,Clérac, Rodolphe,Ali, Mahammad
supporting information, p. 1879 - 1892 (2013/03/13)
Four dinuclear bis(μ-Cl) bridged copper(ii) complexes, [Cu 2(μ-Cl)2(LX)2](ClO 4)2 (LX = N,N-bis[(3,5-dimethylpyrazole-1-yl)- methyl]benzylamine with X = H(1), OMe(2), Me(3) and C
Inverse electron demand hetero-Diels-Alder reaction in preparing 1,4-benzodioxin from o-quinone and enamine
Zhang, Jinsong,Taylor, Chris,Bowman, Erich,Savage-Low, Leo,Lodewyk, Michael W.,Hanne, Larry,Wu, Guang
supporting information, p. 6298 - 6302 (2013/11/06)
A process for synthesizing 1,4-benzodioxin, through oxidation of a phenol to an o-quinone followed by treatment with an enamine, has been developed. Adduct stereochemistry is found to be retained via this one-pot reaction. The method uses hypervalent iodine reagent under mild conditions and is compatible with a wide scope of phenols and enamines.
Dirhodium-catalyzed phenol and aniline oxidations with T-HYDRO. Substrate scope and mechanism of oxidation
Ratnikov, Maxim O.,Farkas, Linda E.,McLaughlin, Emily C.,Chiou, Grace,Choi, Hojae,El-Khalafy, Sahar H.,Doyle, Michael P.
scheme or table, p. 2585 - 2593 (2011/06/19)
Dirhodium caprolactamate, Rh2(cap)4, is a very efficient catalyst for the generation of the tert-butylperoxy radical from tert-butyl hydroperoxide, and the tert-butylperoxy radical is a highly effective oxidant for phenols and anilines. These reactions are performed with 70% aqueous tert-butyl hydroperoxide using dirhodium caprolactamate in amounts as low as 0.01 mol % to oxidize para-substituted phenols to 4-(tert-butyldioxy) cyclohexadienones. Although these transformations have normally been performed in halocarbon solvents, there is a significant rate enhancement when Rh 2(cap)4-catalyzed phenol oxidations are performed in toluene or chlorobenzene. Electron-rich and electron-poor phenolic substrates undergo selective oxidation in good to excellent yields, but steric influences from bulky para substituents force oxidation onto the ortho position resulting in ortho-quinones. Comparative results with RuCl2(PPh 3)3 and CuI are provided, and mechanistic comparisons are made between these catalysts that are based on diastereoselectivity (reactions with estrone), regioselectivity (reactions with p-tert-butylphenol), and chemoselectivity in the formation of 4-(tert-butyldioxy)cyclohexadienones. The data obtained are consistent with hydrogen atom abstraction by the tert-butylperoxy radical followed by radical combination between the phenoxy radical and the tert-butylperoxy radical. Under similar reaction conditions, para-substituted anilines are oxidized to nitroarenes in good yield, presumably through the corresponding nitrosoarene, and primary amines are oxidized to carbonyl compounds by TBHP in the presence of catalytic amounts of Rh 2(cap)4.
