150-19-6Relevant articles and documents
Synthesis of coumarins via palladium-catalyzed carbonylative annulation of internal alkynes by o-lodophenols
Kadnikov, Dmitry V.,Larock, Richard C.
, p. 3643 - 3646 (2000)
(matrix presented) A variety of substituted coumarins have been prepared in good yields by the palladium-catalyzed coupling of o-iodophenols with internal alkynes and 1 atm of carbon monoxide. Unlike most of the previous work on the palladium-catalyzed carbonylation of alkynes, the insertion of the internal alkyne occurs in preference to the insertion of CO.
Aromatic Hydroxylation with an Iron(III)-Catechol-H2O2 System. Mechanistic Implication of the Role of Catechol
Tamagaki, Seizo,Suzuki, Kenji,Tagaki, Waichiro
, p. 148 - 152 (1989)
The role of catechol in benzene hydroxylation with Fe3+/catechol/H2O2 system, the so-called Hamilton system, has been mechanistically investigated by using tiron as a substitute for pyrocatechol.The yield of phenol progresses linearly with reaction time.The phenol yield is dependent on the mole ratio of Fe3+ relative to tiron, and the ratio of more than unity is particularly important for the effective functioning of the catalyst system.The o-, m-, and p-product isomer distributions for a few aromatic hydrocarbons are nearly identical with those of the Fenton reaction.These and the separate experimental results are consistent with the mechanism involving the rate-limiting redox reaction between tiron and Fe3+ and then the follow-up radical chain sequence as in the Fenton reaction.
Selective production of methoxyphenols from dihydroxybenzenes on alkali metal ion-loaded MgO
Vijayaraj, Munusamy,Gopinath, Chinnakonda S.
, p. 376 - 388 (2006)
Selective O-methylation of dihydroxybenzenes (DHBs; catechol, resorcinol, and hydroquinone) to methoxyphenols (MPs) was carried out with dimethylcarbonate on MgO and alkali metal ion (Li, K, and Cs)-loaded MgO between 523 and 603 K. Catalytic activity and product selectivity varied with respect to DHB substrates. Selectivity for O-methylated products increased with increasing basicity of alkali ions; however, K-MgO showed high and stable activity toward MPs. Selectivity for MPs obtained from three substrates increased in the following order: catechol 2 followed by air and 13C CP-MAS NMR measurements indicated the nature of deposited carbon to be molecular species, graphite, MgCO3 and polyaromatics. XPS revealed the nature and availability of active sites on the spent catalysts, as well as the same changes with reaction conditions and correlated with catalytic activity.
O-methylation of dihydroxybenzenes with methanol in the vapour phase over alkali-loaded Si02 catalysts: A kinetic analysis
Bal, Rajaram,Mayadevi,Sivasanker
, p. 17 - 21 (2003)
The vapour-phase O-methylation of the dihydroxybenzenes (DHBs; o-dihydroxybenzene (catechol), m-dihydroxybenzene (resorcinol), and p-dihydroxybenzene (hydroquinone)) with excess methanol has been investigated over alkali (Li, Na, K, and Cs) oxide loaded-SiO2 as catalysts. The reaction takes place in two consecutive steps, the formation of the monomethoxyphenol in the first step (rate constant, k1) and the dimethoxybenzene in the second step (rate constant, k2). The two steps have been assumed to follow a pseudo-first-order kinetics with respect to the substrates (DHB in the first step and the monomethoxy phenol in the second step) and the kinetic parameters, k1, k2, tmax, and Rmax have been calculated. The trends in the values of the above kinetic parameters have been explained on the basis of the reactivity and electronic properties of the three DHBs, the surface basicity of the catalysts, and the mode of adsorption of the molecules on the support.
Imidazolium-urea low transition temperature mixtures for the UHP-promoted oxidation of boron compounds
Martos, Mario,Pastor, Isidro M.
, (2022/01/03)
Different carboxy-functionalized imidazolium salts have been considered as components of low transition temperature mixtures (LTTMs) in combination with urea. Among them, a novel LTTM based on 1-(methoxycarbonyl)methyl-3-methylimidazolium chloride and urea has been prepared and characterized by differential scanning calorimetry throughout its entire composition range. This LTTM has been employed for the oxidation of boron reagents using urea-hydrogen peroxide adduct (UHP) as the oxidizer, thus avoiding the use of aqueous H2O2, which is dangerous to handle. This metal-free protocol affords the corresponding alcohols in good to quantitative yields in up to 5 mmol scale without the need of further purification. The broad composition range of the LTTM allows for the reaction to be carried out up to three consecutive times with a single imidazolium salt loading offering remarkable sustainability with an E-factor of 7.9, which can be reduced to 3.2 by the threefold reuse of the system.
Method for synthesizing M-hydroxyanisole
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Paragraph 0052-0055; 0058-0059; 0064-0067, (2021/11/03)
The invention provides a method for synthesizing M-hydroxyanisole. Belong to organic synthesis technical field. The synthesis method comprises the following steps: a vapor phase mixture of resorcinol and methanol is subjected to alkylation reaction through a metal phosphate - alumina fixed phase catalyst to obtain m-hydroxyanisole. The method adopts the gas-solid phase alkylation method to synthesize the M-hydroxyanisole without separating the reaction product from the catalyst, has the characteristic of continuous reaction, and can realize continuous production in the industrial production process. The method utilizes the acid-base catalytic activity center on the surface of the stationary phase catalyst to catalyze the reaction of resorcinol and methanol, and has high resorcinol conversion rate. The method has the advantage of high selectivity of m-hydroxyanisole. Methanol is used as a methylation reagent, and the method is environmentally friendly, low in cost and high in economic benefit.
Catalytic SNAr Hydroxylation and Alkoxylation of Aryl Fluorides
Kang, Qi-Kai,Li, Ke,Li, Yuntong,Lin, Yunzhi,Shi, Hang,Xu, Lun
supporting information, p. 20391 - 20399 (2021/08/13)
Nucleophilic aromatic substitution (SNAr) is a powerful strategy for incorporating a heteroatom into an aromatic ring by displacement of a leaving group with a nucleophile, but this method is limited to electron-deficient arenes. We have now established a reliable method for accessing phenols and phenyl alkyl ethers via catalytic SNAr reactions. The method is applicable to a broad array of electron-rich and neutral aryl fluorides, which are inert under classical SNAr conditions. Although the mechanism of SNAr reactions involving metal arene complexes is hypothesized to involve a stepwise pathway (addition followed by elimination), experimental data that support this hypothesis is still under exploration. Mechanistic studies and DFT calculations suggest either a stepwise or stepwise-like energy profile. Notably, we isolated a rhodium η5-cyclohexadienyl complex intermediate with an sp3-hybridized carbon bearing both a nucleophile and a leaving group.
Method for hydrolyzing diarylether compound to generate aryl phenol compound
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Paragraph 0162-0166, (2021/09/29)
The invention discloses a method for hydrolyzing a diarylether compound to generate an arylphenol compound. According to the method, visible light is utilized to excite a photosensitizer for catalysis. In a reaction solvent, the raw material in the formula (1) breaks a C (sp2)-O bond under the auxiliary action of acid, and hydrolysis is performed to obtain the bimolecular aryl phenol compounds in the formula (3) and the formula (4). The method can catalyze the reaction at room temperature, is green and environment-friendly, and is easy to operate; the universality is wide, the reaction yield is relatively high, and the tolerance of functional groups is strong; the synthesis method not only can realize small-scale hydrolysis conversion of various diarylether compounds, but also can realize hydrolysis of herbicidal ether, triclosan and a lignin template substrate, and even can realize large-scale hydrolysis of triclosan and the lignin template substrate to realize gram-level degradation. A new strategy is provided for recovering phenol derivatives through lignin hydrolysis, degrading pesticides and purifying wastewater containing a degerming agent or herbicide. The method has wide application prospect and use value.
Benzoic acid resin (BAR): a heterogeneous redox organocatalyst for continuous flow synthesis of benzoquinones from β-O-4 lignin models
Dias, Kevin de Aquino,Pereira Junior, Marcus Vinicius Pinto,Andrade, Leandro Helgueira
supporting information, p. 2308 - 2316 (2021/04/07)
A polymer-bound organocatalyst for Baeyer-Villiger reaction and phenol oxidation under continuous flow conditions is described for the first time.BARhas revealed two catalytic activities that enabled the generation of a novel approach for the synthesis of benzoquinones from β-O-4 lignin models in a one-pot protocol. High catalytic activities (yields up to 98%), selectivities, recyclability and productivity were achieved.
Hollow, mesoporous, eutectic Zn1?xMgxO nano-spheres as solid acid-base catalysts for the highly regio-selectiveO-methylation of 1,2-diphenols
Liu, Jie,Ma, Xuebing,Wang, Xuri,Xie, Guangxin,Yin, Zuyong,Zhang, Jianing
, p. 7454 - 7466 (2021/11/23)
The highly regio-selectiveO-methylation of catechol with dimethyl carbonate (DMC), catalyzed by a solid acid-base catalyst, is an environmentally friendly chemical process for industrial production of guaiacol. However, a guaiacol yield below 84% and high reaction temperature above 280 °C limit its industrial application. Here, hollow, mesoporous Zn1?xMgxO nano-spheres with a eutectic structure, denoted as Zn1?xMgxO HMNSs (x= 0.012-0.089), are facilely fabricatedviathe calcination of Mg2+/Zn2+ion-adsorbing carbon spheres at 500 °C in air. In theO-methylation of catechol with DMC at 180 °C, Zn1?xMgxO HMNSs (x= 0.052) afford guaiacol in 95.5% yield with a complete catechol conversion. Furthermore, 89.0-95.3% mono-ether yields with high 1,2-diphenol conversions (94.5-100%) are also obtained for the other 1,2-diphenols bearing -CH3and -Br groups. Moreover, a plausible mechanism for highly selectiveO-methylation of catechol with DMC is proposed, in which the single-site activation and double-site activation of phenolic hydroxyls by the basic oxygen of Mg-O afford guaiacol and veratrole, respectively.
