123-08-0Relevant articles and documents
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Brady,Jakobovits
, p. 767,769, 777 (1950)
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Practical process for the air oxidation of cresols: Part B. evaluation of the laboratory-scale oxidation process
Barton, Benita,Logie, Catherine G.,Schoonees, Barbara M.,Zeelie, Bernard
, p. 70 - 79 (2005)
Mechanistic proposals and predictions made in a preceding paper (Part A) were evaluated by carrying out the catalytic air oxidation of p-cresol in an alternative solvent system, comprising either a mixture of ethylene glycol and acetic acid (for oxidations under acidic conditions) or ethylene glycol and water (for oxidations under basic conditions). The results obtained in these experiments confirmed that ethylene glycol acts as a nucleophile in these solvent systems, thereby stabilizing the quinomethide intermediate and resulting in highly efficient oxidations in both alkaline and acidic media. 4-Hydroxybenzaldehyde, the desired product, was thus obtained in isolated yields of up to 98% and purities >99%. The inherent draw-backs associated with alkaline methanol and aqueous acetic acid solutions were thus circumvented, and the result is a highly efficient process for the production of 4-hydroxybenzaldehyde.
A novel practical cleavage of tert-butyl esters and carbonates using fluorinated alcohols
Choy, Jason,Jaime-Figueroa, Saul,Lara-Jaime, Teresa
, p. 2244 - 2246 (2010)
Thermolytic cleavage of t-butyl esters and t-butyl carbonates was accomplished using TFE (2,2,2-trifluoroethanol) or HFIP (hexafluoroisopropanol) as solvent. Thus, a practical method to cleanly convert t-butyl esters and carbonates into the corresponding carboxylic acids, decarboxylated products, or alcohols in nearly quantitative yields was developed. The product is recovered by a simple solvent evaporation. The practicality of this methodology was demonstrated on alkyl, aryl, and heteroaromatic esters.
Novel and efficient oxidation of benzyl ethers to benzaldehydes by DMSO/49% aq. HBr
Naik, Ramesh,Pasha
, p. 1723 - 1726 (2007)
Dimethylsulfoxide (DMSO) oxidizes benzyl ethers into corresponding benzaldehydes at 110°C; the reaction is accelerated by 49% aq. HBr. The conditions work well for different aryl-substituted benzyl ethers. This protocol is inert toward dialkyl ethers. Copyright Taylor & Francis Group, LLC.
Aqueous selective photocatalytic oxidation of salicyl alcohol by TiO2 catalysts: Influence of some physico-chemical features
Yurdakal, Sedat,Bellardita, Marianna,Pibiri, Ivana,Palmisano, Leonardo,Loddo, Vittorio
, p. 16 - 24 (2021)
Partial photocatalytic oxidation of salicyl alcohol (2-hydroxybenzyl alcohol) to salicylaldehyde in water was investigated under environmental friendly conditions in the presence of home-prepared and commercial TiO2 (Merck and Aeroxide P25) samples under UVA irradiation. The photocatalysts were characterized by using BET, XRD, SEM and/or TEM techniques. The effects of crystallinity degree, pH (3–11) and presence of a hole trap (ethanol) on the photocatalytic activity and product selectivity were investigated. 4-Hydroxybenzyl alcohol was also used to study the influence of the position of the substituent group in the aromatic ring. High alcohols conversion and product selectivity values were obtained at pH = 11 by using well crystallized TiO2 samples. The conversion values significantly decreased by increasing the hole trap concentration, whereas the selectivity values increased slightly. The selectivity towards the corresponding aldehyde after 30% of alcohol conversion was significantly higher for 4-HBA (48%) than for 2-HBA (32%), due to the role of the para position of the substituent group. In order to clarify the different selectivity of the products, various experiments have been also performed starting from the products; these results indicate that the selectivity is also strongly dependent on the stability of the formed products under the experimental conditions used. By concluding, this article reports that the conversion and selectivity values for the studied reaction depend both on the TiO2 type and on the substrate.
Oxidation of p-cresol to p-hydroxybenzaldehyde with molecular oxygen in the presence of CuMn-oxide heterogeneous catalyst
Wang, Feng,Yang, Guanyu,Zhang, Wei,Wu, Wenhai,Xu, Jie
, p. 633 - 638 (2004)
A high-yield synthesis of p-hydroxybenzaldehyde from p-cresol and molecular oxygen was achieved over a CuMn-oxide supported carbon catalyst. The reaction parameters such as pressure, stirring speed, reaction temperature, solvent, and the amount of sodium hydroxide in the reaction media were optimized. As a result, a high conversion of p-cresol (99%) and a high selectivity to p-hydroxybenzaldehyde (96%) were realized at the same time. Catalyst separation and recycling tests clearly showed that the reaction proceeded on the heterogeneous catalyst but not on dissolved species.
Highly active nanostructured Co3O4 catalyst with tunable selectivity for liquid phase air oxidation of p-cresol
Kshirsagar, Vikas S.,Vijayanand, Subramanian,Potdar, Hari S.,Joy, Pattayil A.,Patil, Kashinath R.,Rode, Chandrashekhar V.
, p. 310 - 311 (2008)
This is a first report of highly efficient heterogeneous nanostructured Co3O4 catalyst (6-8 nm) having high surface area (95 m2/g) developed for selective liquid phase air oxidation of p7-cresol under atmospheric pressure conditions. Copyright
Reduced Graphene Oxide Composite with Oxidizable Manganese/Cobalt Mixed Oxide for p-Cresol Oxidation by Using Molecular Oxygen
Jha, Ajay,Patil, Sagar H.,Solanki, Bhanu P.,Ribeiro, Ana P. C.,Castro, Carlos A. N.,Patil, Kashinath R.,Coronas, Alberto,Rode, Chandrashekhar V.
, p. 1164 - 1169 (2015)
A composite of graphene oxide (GO) with mixed oxide (MnCo) was prepared by using a solvothermal method. During the synthesis, both the reduction of GO and growth of metal oxides took place simultaneously. The as-prepared composite material was highly selective for the liquid-phase oxidation of p-cresol to form p-hydroxybenzaldehyde in 71% yield within 1 h. The composite material was characterised by SEM, X-ray photoelectron spectroscopy, high-resolution TEM and cyclic voltammetry (CV). A CV study revealed that the increase in the redox potential of the mixed oxide after being supported on GO, led to its higher activity of the catalyst for the oxidation reaction. The stability of the catalyst under the reaction conditions was studied by its successful reuse in three cycles.
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Amakasu,T.,Sato,K.
, p. 1428 - 1432 (1967)
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Novel synthesis of Ag decorated TiO2 anchored on zeolites derived from coal fly ash for the photodegradation of bisphenol-A
Hlekelele, Lerato,Franklyn, Paul J.,Dziike, Farai,Durbach, Shane H.
, p. 1902 - 1912 (2018)
The disposal of millions of tons of coal fly ash (CFA) threatens the environment, hence means to reuse CFA are highly sought after. In this study, CFA was reused to make materials which were tested for water purification. Zeolitic material (CFA-Zeo) was derived from CFA by a 2-step alkali-fusion hydrothermal method and then composited with TiO2 nanoparticles using a novel resin-gel technique. CFA-Zeo loadings were 15 and 30 wt% in the resulting TiO2/CFA-Zeo composites. These composites were then loaded with 1 wt% Ag nanoparticles by a deposition-precipitation technique using NaOH and urea. CFA-Zeo rods (morphology confirmed by TEM) were confirmed by PXRD to be sodium aluminum silicate hydrate. TEM analyses of the CFA-Zeo rods in the composites revealed them to be completely coated with TiO2 nanoparticles that had Ag nanoparticles on their surfaces. The photoluminescence emission peak of TiO2 was found to be significantly higher than that of TiO2/CFA-Zeo composites, with the TiO2/CFA-Zeo composites that were loaded with Ag having even lower emission intensities. UV-vis DRS spectra showed that CFA-Zeo had no effect on the band gap of TiO2, while composites that contained Ag had a wide absorption band in the visible region. The photocatalytic efficiency of these materials was then determined using bisphenol-A (BPA) as a model compound under both UV and visible light. Except for the 30 wt% TiO2/CFA-Zeo composites without Ag, all of the composites had superior photoactivity to uncomposited TiO2 under both UV and visible light. On the other hand, composites with Ag nanoparticles showed the best photoactivities. The superior photoactivities of these composites under UV-light were mainly attributed to the separation of charge carriers, whereas under visible light it was attributed to the ability of silver to harvest visible light through surface plasmon resonance (SPR).
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Kratzl,Billek
, p. 845,854 (1954)
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Photochromism of the synthetic 4′,7-dihydroxyflavylium chloride
Figueiredo, Paulo,Lima, Jo?o C.,Santos, Helena,Wigand, Marie-Claude,Brouillard, Raymond,Ma?anita, António L.,Pina, Fernando
, p. 1249 - 1254 (1994)
The synthetic compound 4′,7-dihydroxyflavylium chloride shows an interesting photochromic effect at moderately acidic pH values. Pale yellow solutions of this compound, equilibrated in the dark at pH 3.4, become bright yellow upon irradiation with 313-nm light. Switching off the light, gives back the initial pale yellow solution. Photochemical methods, 1H NMR, and molecular orbital calculations were used to elucidate this photochromic behavior. In solutions equilibrated in the dark (pH 5.7), the existence of two main species in equilibrium is demonstrated: the colored flavylium cation and the colorless trans-chalcone. Freshly prepared solutions of this compound at pH 6.2 reveal the existence of another colored form, the quinonoidal base, which reacts thermally to yield trans-chalcone. An analogous reaction takes place in freshly prepared solutions at pH 3.4: the flavylium cation is partially converted into trans-chalcone. The extent of such conversion is pH dependent and nearly complete at pH 6.2. Irradiation of transchalcone at the wavelength of 313 nm partially gives back the initial colored form, with concomitant formation of small amounts of photodegradation products. The turnover of the photochromic reaction is greater at pH 3.4 than at pH 6.2. The photochromism is explained on the basis of a trans-cis photoisomerization. In fact the relative stability of the two chalcone isomers is reversed in the excited state, as predicted from molecular orbital calculations.
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Hodgson,Jenkinson
, p. 469,470 (1929)
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A highly stable zeotype mesoporous zirconium metal-organic framework with ultralarge pores
Feng, Dawei,Wang, Kecheng,Liu, Tian-Fu,Park, Jihye,Wei, Zhangwen,Bosch, Mathieu,Zhou, Hong-Cai,Su, Jie,Zou, Xiaodong,Yakovenko, Andrey
, p. 149 - 154 (2015)
Through topological rationalization, a zeotype mesoporous Zr-containing metal-organic framework (MOF), namely PCN-777, has been designed and synthesized. PCN-777 exhibits the largest cage size of 3.8 nm and the highest pore volume of 2.8 cm3 g-1among reported Zr-MOFs. Moreover, PCN-777 shows excellent stability in aqueous environments, which makes it an ideal candidate as a support to incorporate different functional moieties. Through facile internal surface modification, the interaction between PCN- 777 and different guests can be varied to realize efficient immobilization.
PHOTOCATALYTIC OXIDATION OF p-CRESOL IN AQUEOUS TITANUM DIOXIDE SUSPENSION
Brezova, Vlasta,Brandsteterova, Eva,Ceppan, Michal,Pies, Juraj
, p. 1285 - 1293 (1993)
The reaction products of the photocatalytic oxidation of p-cresol were characterized by high performance liquid chromatography.The influence of p-cresol concentration as well as the presence of dioxygen and hydrogen peroxide on the rate of photocatalytic oxidation was studied.The p-cresol concentration in the irradiated systems was determined by spectroscopic method using α-nitroso-β-naphthol or by the Principal Component Regression method (in the samples with hydrogen peroxide added).The reaction pathway of the photocatalytic oxidation of p-cresol in TiO2 was suggested.
Mechanism of the redox reaction of the aequorea green fluorescent protein (GFP)
Kojima, Satoshi,Hirano, Takashi,Niwa, Haruki,Ohashi, Mamoru,Inouye, Satoshi,Tsuji, Frederick I.
, p. 2875 - 2878 (1997)
A model compound, 4-(4-hydroxypheny])methylideneimidazol-5 undergoes a reversible redox reaction identical to that of the Aequorea green fluorescent protein (GFP), strongly suggesting that the GFP chromophore is derived via the autoxidation of a nonfluorescent dihydro precursor in dihydro-GFP.
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Omura,Matsuura
, p. 1516 (1969)
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Acid-promoted reaction of the stilbene antioxidant resveratrol with nitrite ions: Mild phenolic oxidation at the 4′-hydroxystiryl sector triggering nitration, dimerization, and aldehyde-forming routes
Panzella, Lucia,De Lucia, Maria,Amalfitano, Carmine,Pezzella, Alessandro,Evidente, Antonio,Napolitano, Alessandra,D'Ischia, Marco
, p. 4246 - 4254 (2006)
In 0.1 M phosphate buffer, pH 3.0, and at 37 °C, resveratrol ((E)-3,4′,5-trihydroxystilbene, 1a), an antioxidant and cancer chemopreventive phytoalexin, reacted smoothly at 25 μM or 1 mM concentration with excess nitrite ions (NO2-) to give a complex pattern of products, including two novel regioisomeric α-nitro (3a) and 3′-nitro (4) derivatives along with some (E)-3,4′,5-trihydroxy-2, 3′-dinitrostilbene (5), four oxidative breakdown products, 4-hydroxybenzaldehyde, 4-hydroxy-3-nitrobenzaldehyde, 3,5- dihydroxyphenylnitromethane, and 3,5-dihydroxybenzaldehyde, two dimers, the resveratrol (E)-dehydrodimer 6 and restrytisol B (7), and the partially cleaved dimer 2. The same products were formed in the absence of oxygen. 1H, 15N HMBC and LC/MS analysis of the crude mixture obtained by reaction of 1a with Na15NO2 suggested the presence of 3,4′,5,β-tetrahydroxy-α-nitro-α,β-dihydrostilbene (8) as unstable intermediate which escaped isolation. Under similar conditions, the structurally related catecholic stilbene piceatannol ((E)-3,3′,4, 5′-tetrahydroxystilbene, 1b) gave, besides (E)-3,3′,4,5′- tetrahydroxy-β-nitrostilbene (3b), 3,4-dihydroxybenzaldehyde and small amounts of 3,5-dihydroxybenzaldehyde. Mechanistic experiments were consistent with the initial generation of the phenoxyl radical of 1a at 4′-OH, which may undergo free radical coupling with NO2 at the α- or 3′-position, to give eventually nitrated derivatives and/or oxidative double bond fission products, or self-coupling, to give dimers. The oxygen-independent, NO2--mediated oxidative fission of the double bond under mild, physiologically relevant conditions is unprecedented in stilbene chemistry and is proposed to involve breakdown of hydroxynitro(so) intermediates of the type 8.
Absolute structures of C-glucosides of resveratrol oligomers from Shorea uliginosa
Ito, Tetsuro,Abe, Naohito,Oyama, Masayoshi,Iinuma, Munekazu
, p. 2516 - 2520 (2009)
Two C-glucosides of resveratrol dimers (uliginoside A (1) and hemsleyanoloside B (2)) consisting of enantiomeric aglycones and two C-glucosides of resveratrol trimers (uliginosides B (3) and C (4)) consisting of diastereomeric aglycones were isolated from
A highly photosensitive covalent organic framework with pyrene skeleton as metal-free catalyst for arylboronic acid hydroxylation
Chen, Ying,Huo, Jianqiang,Zhang, Yubao
, (2022/03/16)
Covalent organic frameworks (COFs) have been widely utilized in metal-free photocatalytic synthesis base on their excellent properties such as super conjugation, porosity and stability. In this work, we synthesized a new COF material using 1,3,6,8-Tetrakis (p-formylphenyl)pyrene (TFPPy) and 2,2′-Dimethylbenzidine (DMBZ) as basic units through Schiff base condensation reaction. The new COF (TF-DM COF) was applied as metal-free catalyst for hydroxylation of arylboronic acids. The results indicated that the extended π conjugation of COFs enhanced the absorption of visible light, and the large porosity (BET surface area: 113.782 m2g?1) accelerated the reaction rate. Good recyclability enables it with multiple applications, which result in a great reducing of the cost. This study reports that TF-DM COF has a broad application prospect as a new generation of metal-free photocatalysts for organic conversions.
Nickel Hydride Catalyzed Cleavage of Allyl Ethers Induced by Isomerization
Kathe, Prasad M.,Berkefeld, Andreas,Fleischer, Ivana
supporting information, p. 1629 - 1632 (2021/02/09)
This report discloses the deallylation of O - and N -allyl functional groups by using a combination of a Ni-H precatalyst and excess Bronsted acid. Key steps are the isomerization of the O - or N -allyl group through Ni-catalyzed double-bond migration followed by Bronsted acid induced O/N-C bond hydrolysis. A variety of functional groups are tolerated in this protocol, highlighting its synthetic value.
SBA-15 Supported Silver Catalyst for the Efficient Aerobic Oxidation of Toluene Under Solvent-Free Conditions
Chen, Lei,Chen, Yanjiao,Dai, Xuan,Guo, Jiaming,Peng, Xinhua
, (2021/12/09)
The efficient SBA-15 supported silver catalysts(Ag/SBA-15) were prepared and characterized by ICP-OES, XRD, TEM, SEM, XPS and N2 adsorption–desorption techniques. The catalysts exhibited an excellent catalytic activity for the aerobic oxidation of toluene to benzaldehyde under solvent-free conditions. Conversion of toluene and selectivity of benzaldehyde were 50% and 89% respectively over catalyst with 9.1 wt% Ag loading (10Ag/SBA-15). A wide range of substrates were tolerated under the selected reaction conditions. The kinetic study shows that the oxidation of toluene over 10Ag/SBA-15 is pseudo-first-order reaction and the activation energy Ea is 45.1?kJ/mol. A plausible mechanism involving oxygen free radicals was proposed for the aerobic oxidation reaction. Compared with the traditional method, the newly designed heterogeneous catalytic system shows better economic applicability, environmental friendliness and broader application prospects. Graphical abstract: [Figure not available: see fulltext.]