2455-14-3Relevant articles and documents
Oxidation of 3,5,3′,5′-tetra-tert-butyl-4,4′ -dihydroxybiphenyl with atmospheric oxygen in the absence of base catalysts
Bukharov,Fazlieva,Mukmeneva,Akhmadullin,Morozov
, p. 1805 - 1807 (2002)
Use of dimethylformamide as solvent and preliminary addition of 3,5,3′,5′-tetra-tert-butyl-4,4′-diphenoquinone allow oxidation of 3,5,3′,5′-tetra-tert-butyl-4,4′ -dihydroxybiphenyl with atmospheric oxygen to be efficiently performed in the absence of base catalysts.
Pirkle,Koser
, p. 3959 (1968)
Enantioselective Desymmetrization of 1,4-Dihydropyridines by Oxidative NHC Catalysis
Di Carmine, Graziano,Ragno, Daniele,Brandolese, Arianna,Bortolini, Olga,Pecorari, Daniel,Sabuzi, Federica,Mazzanti, Andrea,Massi, Alessandro
, p. 7469 - 7474 (2019)
The unprecedented desymmetrization of prochiral dialdehydes catalyzed by N-heterocyclic carbenes under oxidative conditions was applied to the highly enantioselective synthesis of 1,4-dihydropyridines (DHPs) starting from 3,5-dicarbaldehyde substrates. Synthetic elaboration of the resulting 5-formyl-1,4-DHP-3-carboxylates allowed for access to the class of pharmaceutically relevant 1,4-DHP-3,5-dicarboxylates (Hantzsch esters). DFT calculations suggested that the enantioselectivity of the process is determined by the transition state involving the oxidation of the Breslow intermediate by the external quinone oxidant.
Spectrophotometric determination of formation constants for the Cu-ethylenediamine-halogen (chloride and bromide) system and their catalytic effect on the oxidative coupling of 2,6-di-tert-butyl-phenol
Segoviano-Garfias, José J.N.,Moreno-Esparza, Rafael,Mendoza-Díaz, Guillermo
, p. 3461 - 3468 (2010)
In order to explain the mechanism of the dimerization of 2,6-di-tert-butyl-phenol when catalyzed by the copper-ethylenediamine complexes, a spectrophotometric study of the speciation of copper(II) complexes in methanol of Cu(II), ethylendiamine and Cl- or Br- was carried out at 303 K. The formation constants obtained for the copper chloride system are: log β101 = 2.90 ± 0.03, log β102 = 6.39 ± 0.03 and log β103 = 8.62 ± 0.04, for the copper bromide system are log β101 = 3.01 ± 0.10, log β102 = 5.50 ± 0.08, for the copper-ethylendiamine complexes are log β110 = 6.13 ± 0.05 and log β120 = 10.54 ± 0.08, and for the ternary copper-ethylenediamine chloride or bromide systems are log β111 = 10.21 ± 0.03 and log β111 = 10.07 ± 0.03, respectively. Knowing the speciation of the copper-ethylenediamine-halide systems, the kinetic studies can be correlated with the species in solution. Comparative studies of the oxidation reaction of 2,6-di-tert-butyl-phenol using different copper(II) complexes with chloride or bromide and ethylenediamine as catalyst are reported. Their catalytic activity in the oxidation of 2,6-di-tert-butyl-phenol was monitored in methanol solution, following the corresponding quinone formation, at 418 nm ( = 3.95 × 104 mol-1 L cm-1 at 303 K). The results indicate that the most active species are [Cu(en)X]+, where X is bromide or chloride, Both complexes have similar activity.
Fatiadi
, p. 357 (1973)
Kothari,Tazuma
, p. 180,183 (1976)
Physical and Chemical Properties of Mononuclear Cobalt Dioxygen Complexes with Tetraimidazolyl-Substituted Pyridine Chelates
Tamagaki, Seizo,Kanamaru, Yutaka,Ueno, Masanori,Tagaki, Waichiro
, p. 165 - 174 (1991)
A new class of mononuclear superoxocobalt complexes containing four equal imidazolyl-donors and one pyridyl-donor per cobalt(II) ion was prepared and their chemical and physical properties were compared with those of cobalt(II) Schiff-base type dioxygen complexes.
Magnetic Field Effects on the Catalytic Oxidation of 2,6-Di-tert-butylphenol
Perito, Richard P.,Corden, Barry B.
, p. 4418 - 4419 (1987)
-
The facile oxidative coupling of a hindered phenol, 2,6-di-t-butylphenol, driven by N,N′-bis(ethoxy-carbonyl)-1,4-benzoquinone diimine; The reaction pattern traced by 1H NMR spectroscopy
Miyagi, Yo,Banjyo, Noriko,Yamamura, Emiko
, p. 857 - 858 (2002)
Good yields of 3,3′,5,5′-tetra-t-butyl-4,4′-dipheno- quinone were obtained by the reaction of 2,6-di-t-butylphenol with N,N′-bis(ethoxycarbonyl)-1,4-benzoquinone diimine, which had been shown to undergo addition with aniline derivatives and phenols. The reaction was followed with 1H NMR spectroscopy to deduce the reaction intermediates.
4-Hydroxyaryl complexes of group 10 metals
So, Shiu-Chun,Cheung, Wai-Man,Sung, Herman H.-Y.,Williams, Ian D.,Leung, Wa-Hung
, p. 1 - 4 (2017)
Attempts have been made to synthesize group 10 metal complexes bearing σ-bonded 4-hydroxyaryl ligands that are potential precursors to metallaquinones. Treatment of 4-bromo-2,6-di-tert-butylphenol with [Pd(PPh3)4] led to formation of the phosphaquinone Ph3P = C6H3tBu2-3,5-O-4 (1), whereas that with [M(PPh3)4] (M = Ni, Pt) yielded the biquinone [C6H3tBu2-3,5-O-4]2 (2). The solid-state structure of 1 features a short C=O double bond and alternate phenyl C-C single and double bonds that are characteristic of quinoidal compounds. Alkylation of [NiCl2(PPh3)2] with (C6H2Me2-3,5-OSiMe3-4)MgBr afforded cis-[Ni(PPh3)2Br(C6H2Me2-3,5-OSiMe3-4)] (3) that reacted with nBu4NF to yield [Ni(PPh3)(C6H2Me2-3,5-OH-4)]2(μ-OH)2 (4) containing a σ-bonded 4-hydroxyaryl ligand.
Observation of a Sterically Hindered Hydroxyarenesulfenyl Chloride: Novel Base-Catalyzed Dimerization to a Diphenoquinone
Pastor, Stephen D.
, p. 5260 - 5262 (1984)
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Horvath et al.
, p. 41,44, 49 (1979)
Destabilizing Character of a π-Conjugated Boron Center in Bisphenol Radicals
Chung, Ming-Han,Yu, Isaac Furay,Liu, Yi-Hung,Lin, Tien-Sung,Peng, Shie-Ming,Chiu, Ching-Wen
, p. 11732 - 11737 (2018)
Although boron-containing radicals are promising materials for molecular electronic devices, the electronic effect of the σ-donating yet π-accepting boron center on the stability of open-shell species has been less discussed. In this work, the role of a tricoordinate boron center in π-conjugated radicals was explored through electron paramagnetic resonance measurement of several boron-linked bisphenol radicals and diradicals. Replacing the bridging methine fragment of a neutral Galvinoxyl radical with an arylboryl group led to the corresponding boron-linked radical anion that requires excessive steric protection at the boron center to be persistent in solution. Experimental and theoretical investigations revealed that the introduction of boron would diminish the quinoidal character of the phenoxyl radical and increase both the electrophilicity and nucleophilicity of the open-shell species. Therefore, it is important to consider the steric protection of the boron center in boron-containing π-conjugated organic radicals.
Heterogeneously catalyzed aerobic oxidative biaryl coupling of 2-naphthols and substituted phenols in water
Matsushita, Mitsunori,Kamata, Keigo,Yamaguchi, Kazuya,Mizuno, Noritaka
, p. 6632 - 6640 (2005)
The oxidative coupling reaction can efficiently be promoted by supported ruthenium catalyst Ru(OH)x/Al2O3. A variety of 2-naphthols and substituted phenols can be converted to the corresponding biaryl compounds in moderate to excellent yields using molecular oxygen as a sole oxidant in water without any additives. The catalysis is truly heterogeneous in nature, and Ru(OH)x/Al2O3 can easily be recovered after the reaction. The catalyst can be recycled seven times with the maintenance of the catalytic performance, and the total turnover number reaches up to 160. The results of competitive coupling reactions suggest that the present oxidative biaryl coupling reaction proceeds via the homolytic coupling of two radical species and the Ru(OH)x/Al2O3 catalyst acts as an one-electron oxidant. Two radical species are coupled to give the corresponding biaryl product, and the one-electron reduced catalyst is reoxidized by molecular oxygen. The amounts of O2 uptake and H 2O formation were almost one-quarter and one-half the amount of substrate consumed, respectively, supporting the reaction mechanism. The kinetic data and kinetic isotope effect show that the reoxidation of the reduced catalyst is the rate-limiting step for the coupling reaction.
Fe(III)-EDTA mediated autoxidation of 2,6-di-t-butylphenol and substituted hydroquinones by molecular oxygen
Sain, Bir,Murthy, Pappu S.,Venkateshwar Rao,Prasada Rao,Joshi, Girish C.
, p. 5083 - 5084 (1994)
Fe(III)-EDTA in aq. MeOH offers a simple environmentally acceptable synthetic tool to oxidize 2,6-di-t-butylphenol to 3,3',5,5'-tetra-t-butyl- 4,4'-diphenoquinone by molecular oxygen with 100% selectivity and several alkyl-substituted hydroquinones to their quinones, in excellent yields, under mild conditions.
Autooxidation of 2,6-Di-tert-butylphenol in Water Catalyzed by Cobalt Phthalocyaninetetrasulfonate Bound to Polymer Colloids
Turk, Hayrettin,Ford, Warren T.
, p. 460 - 462 (1988)
Cobalt phthalocyaninetetrasulfonate (CoPcTs) bound to 54-74-nm styrene-divinylbenzene copolymer latexes substituted with quarternary ammonium ions catalyzes autooxidation of 2,6-di-tert-butylphenol in water ten times faster than does CoPcTs in aqueous solution.
Development of cobalt(3,4-diarylsalen) complexes as tumor therapeutics
Gust, Ronald,Ott, Ingo,Posselt, Diana,Sommer, Klaus
, p. 5837 - 5846 (2004)
[1,6-Bis(2-hydroxyphenyl)-3,4-diaryl-2,5-diazahexa-1,5-diene]cobalt(II) complexes (cobalt(3,4-diarylsalen)) with 2-, 3-, or 4-OCH3/OH substituents in the 3,4-standing aryl rings were synthesized and tested for antitumor activity in vitro on the MCF-7, MDA-MB 231, and LNCaP/ FGC cell lines. The cytotoxicity depended on both the configuration of the diene ligand and the kind of substituents in the 3,4-standing aromatic rings. d,1-7 (2-OCH 3), d,1-8 (3-OCH3), and d,1-9 (4-OCH3) were equipotent to cisplatin, while the respective hydroxy-substituted complexes (d,1-10 (2-OH), d,1-11(3-OH), and d,1-12 (2-OH)) as well as all of the meso-configured compounds (m-7 to m-12) did not influence the cell growth. Interestingly, a high catalytic potency and a rapid and high accumulation in MCF-7 cells (15- to 25-fold compared to the cell culture medium (5 μM)) were demonstrated for m-7 (2-OCH3), m-8 (3-OCH3), and m-9 (4-OCH3). Therefore, a mode of action based on a cobalt-catalyzed oxidative damage of the DNA is not very likely.
Fullerton,Ahern
, p. 139 (1976)
Oxidation of activated phenols by dioxygen catalysed by the H5PV2Mo10O40 heteropolyanion
Lissel,Jansen In De Wal,Neumann
, p. 1795 - 1798 (1992)
The H5PV2Mo10O40 heteropolyanion has been found to catalyse the highly selective aerobic oxidation of dialkylphenols to diphenoquinones and the oxidation of 2,3,5-trimethylphenol to the 2,3,5-trimethyl-1,4-benzoquinone. The rate is highly dependent on the oxidation potential of the substrate and is proceeds by electron transfer from the phenol substrate to the heteropolyanion catalyst.
An efficient oxidation of 2,6-di-tert-butylphenol to 3,3',5,5'-tetra-tert- butyl-4,4'-diphenoquinone catalyzed by Lewis Acid system in the presence of molecular oxygen
Sheng, Hong-Ting,Wang, Hui,Feng, Yan,Shi, Jian-Hua,Jiao, Yong-Hua,Zhu, Man-Zhou
, p. 609 - 613,5 (2012)
An efficient and simple method for the preparation of 3,3',5,5'-tetra-tert- butyl-4,4'-diphenoquinone (TBDPQ) is reported using Lewis Acid as an effective catalyst in the presence of molecular oxygen from 2,6-di-tert-butylphenol (DBP). The present methodology offers several advantages, such as excellent yields, accessible and inexpensive catalysts, easy work-up and green conditions. The oxidation reaction was found to proceed in two steps and the oxidation kinetics for FeCl3 system was examined in detail.
Lappin,Zannucci
, p. 5085 (1969)
Transformation of Formazanate at Nickel(II) Centers to Give a Singly Reduced Nickel Complex with Azoiminate Radical Ligands and Its Reactivity toward Dioxygen
Ar, Deniz,Kilpatrick, Alexander F. R.,Cula, Beatrice,Herwig, Christian,Limberg, Christian
supporting information, p. 13844 - 13853 (2021/05/04)
The heteroleptic (formazanato)nickel bromide complex LNi(μ-Br)2NiL [LH = Mes-NH-N═C(p-tol)-N═N-Mes] has been prepared by deprotonation of LH with NaH followed by reaction with NiBr2(dme). Treatment of this complex with KC8led to transformation of the formazanate into azoiminate ligands via N-N bond cleavage and the simultaneous release of aniline. At the same time, the potentially resulting intermediate complex L′2Ni [L′ = HN═C(p-tol)-N═N-Mes] was reduced by one additional electron, which is delocalized across the π system and the metal center. The resulting reduced complex [L′2Ni]K(18-c-6) has aS=1/2ground state and a square-planar structure. It reacts with dioxygen via one-electron oxidation to give the complex L′2Ni, and the formation of superoxide was detected spectroscopically. If oxidizable substrates are present during this process, these are oxygenated/oxidized. Triphenylphosphine is converted to phosphine oxide, and hydrogen atoms are abstracted from TEMPO-H and phenols. In the case of cyclohexene, autoxidations are triggered, leading to the typical radical-chain-derived products of cyclohexene.
Structure, Spectroscopy, and Reactivity of a Mononuclear Copper Hydroxide Complex in Three Molecular Oxidation States
Garcia-Bosch, Isaac,Lancaster, Kyle M.,Macmillan, Samantha N.,Rajabimoghadam, Khashayar,Siegler, Maxime A.,Wu, Tong
supporting information, p. 12265 - 12276 (2020/08/06)
Structural, spectroscopic, and reactivity studies are presented for an electron transfer series of copper hydroxide complexes supported by a tridentate redox-active ligand. Single crystal X-ray crystallography shows that the mononuclear [CuOH]1+ core is stabilized via intramolecular H-bonds between the H-donors of the ligand and the hydroxide anion when the ligand is in its trianionic form. This complex undergoes two reversible oxidation processes that produce two metastable "high-valent"CuOH species, which can be generated by addition of stoichiometric amounts of 1e- oxidants. These CuOH species are characterized by an array of spectroscopic techniques including UV-vis absorption, electron paramagnetic resonance (EPR), and X-ray absorption spectroscopies (XAS), which together indicate that all redox couples are ligand-localized. The reactivity of the complexes in their higher oxidation states toward substrates with modest O-H bond dissociation energies (e.g., 4-substitued-2,6-di-tert-butylphenols) indicates that these complexes act as 2H+/2e- oxidants, differing from the 1H+/1e- reactivity of well-studied [CuOH]2+ systems.
