109-00-2Relevant articles and documents
A Method for the Measurement of Site-Specific Tautomeric and Zwitterionic Microspecies Equilibrium Constants
D'Angelo, Joseph C.,Collette, Timothy W.
, p. 1642 - 1650 (1997)
We describe a method for the individual measurement of simultaneously occurring, unimolecular, site-specific "microequilibrium" constants as in, for example, prototronic tautomerism and zwitterionic equilibria.Our method represents an elaboration of that of Nygren et al. (Anal.Chem. 1996, 68, 1706-10), which thereby becomes generalized and improves the accuracy.Specifically, by making spectral measurements as a function of temperature, we demonstrate the ability to determine site-specific microenthalpies unambiguously.Analysis proceeds via multivariate nonlinear regression modeling of, for example, the Gibbs-Helmholtz relation.Additional determinations of macroscopic equilibrium constants as a function of temperature, in combination with the previously determined microenthalpies, in turn enables the determination of all remaining site-specific thermodynamic parameters, i.e., microentropies, micro free energies, and/or microequilibrium constants, and moreover allows us to resolve and measure the spectra of tautomeric isocoulombers.To our knowledge, we have hereby devised the first such universally applicable and accurate measurement method on record.
Reaction of OH with Pyridine. Pulse-Radiolytic and Product-Analysis Studies
Selvarajan, N.,Raghavan, N. V.
, p. 2548 - 2551 (1980)
The products obtained from the reaction of OH radicals, generated radiolytically, with pyridine under conditions where the intermediate 1-azahydroxycyclohexadienyl radicals are oxidized to isomeric hydroxypyridines have been examined by high-performance liquid chromatographic methods.From product-analysis data, the initial radiation chemical yields of o-, m-, and p-hydroxypyridines are 1.0, 3.8, and 0.3, respectively.The high yield of m-hydroxypyridine exemplifies the electrophilic nature of OH.The low yield of p-hydroxypyridine is attributed to the failure to quantitatively oxidize the 1-aza-p-hydroxycyclohexadienyl radical by the more powerful oxidant such as IrCl62-.The isomeric OH adducts of pyridine exhibit selectivity in reactivity with the two oxidants examined, and their reducing strength follows the order meta > ortho > para.From optical pulse radiolysis the second-order rate constant for the electron-transfer processes between hexachloroiridate and meta and ortho pyridine-OH adducts was determined to be 5.8 * 1E8 M-1 s-1.
Conversion of 5-hydroxymethylfurfural into 6-(hydroxymethyl)pyridin-3-ol: A pathway for the formation of pyridin-3-ols in honey and model systems
Hidalgo, Francisco J.,Lavado-Tena, Cristina M.,Zamora, Rosario
, p. 5448 - 5454 (2020)
The formation of 6-(hydroxymethyl)pyridin-3-ol by ring expansion of 5-(hydroxymethyl)furfural (HMF) in the presence of ammonia-producing compounds was studied to determine the routes of formation of pyridin-3-ols in foods. 6-(Hydroxymethyl)pyridin-3-ol was produced from HMF in model systems, mostly at neutral pH values, as a function of reaction times and temperature and with an activation energy (Ea) of 74 ± 3 kJ/mol, which was higher than that of HMF disappearance (43 ± 4 kJ/mol). A reaction pathway is proposed, which is general for the formation of pyridin-3-ols from 2-oxofurans. Thus, it explains the conversions of furfural into pyridin-3-ol and of 2-acetylfuran into 2-methylpyridin-3-ol, which were also studied. When honey and sugarcane honey were heated, they produced different pyridin-3-ols, although 6-(hydroxymethyl)pyridin-3-ol was the pyridine-3-ol produced to the highest extent. Obtained results suggest that formation of pyridin-3-ols in foods is unavoidable when 2-oxofurans are submitted to thermal heating and ammonia (or ammonia-producing compounds) is present.
Cleavage of aromatic methyl ethers by chloroaluminate ionic liquid reagents
Kemperman, Gerardus J.,Roeters, Theodorus A.,Hilberink, Peter W.
, p. 1681 - 1686 (2003)
We have discovered serendipitously that chloroaluminate ionic liquids can cleave aromatic methyl ethers under surprisingly mild conditions. Three ionic liquids, viz. [TMAH]-[Al2Cl7], [BMIM][Al2Cl7], and [EMIM][Al2Cl6I], and aluminum chloride were compared in the selective demethylation of 4,5-dimethoxyindanone at the 4-methoxy-function. The ionic liquids exhibited a remarkably high selectivity (96:4) in comparison with aluminum chloride (70:30). In addition, the reaction time was drastically shortened when the ionic liquids were used. Interestingly, the three ionic liquids displayed the same reactivity in the demethylation of 4,5-dimethoxyindanone. Considering the lower cost and the bulk availability of the precursors of [TMAH][Al2Cl7], we conclude that this is the most attractive ionic liquid from an industrial point of view. To make the large-scale application of [TMAH][Al2Cl7] feasible, we have developed a safe upscalable method for its preparation. Furthermore, the scope of ether cleavage by the ionic liquid reagent [TMAH][Al2Cl7] was investigated and it was found that aromatic methyl-, al- lyl-, and benzyl-ether cleavage is applicable to a variety of heterocyclic compounds. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
Demethylation of methoxypyridines with sodium trimethylsilanethiolate
Shiao, Min-Jen,Ku, Wei-Shen,Hwu, Jih Ru
, p. 323 - 328 (1993)
Demethylation of methoxypyridines was accomplished in 55-87percent yield by use of ca. 1.5-2.5 equivalents of NaSSiMe3 in 1,3-dimethyl-2-imidazolidinone at 120-180 deg C.This method was found applicable to a methoxyquinoline and methoxypyridines containing a second substituent, such as Cl, OMe, and COOMe.
A BODIPY dye as a reactive chromophoric/fluorogenic probe for selective and quick detection of vapors of secondary amines
Fu, Yanyan,He, Qingguo,Zhu, Defeng,Wang, Yuerong,Gao, Yixun,Cao, Huimin,Cheng, Jiangong
, p. 11266 - 11268 (2013)
A new reaction based fluorescence turn-off strategy for detection of secondary amines was developed. The probe shows fast response and high selectivity to secondary amines in solution/film at sub-ppm levels through chromogenic and fluorescent dual-mode signal changes.
Isomeric methoxypyridine-1-oxides and 1-methoxypyridones: electronic spectra and structure
Cignitti, Maurizio,Soccorsi, Laura,Gatta, Franco,Cotta-Ramusino, Marina
, p. 1287 - 1294 (1985)
The electronic spectra of the isomeric of hydroxypyridine-1-oxides and 1-hydroxy-pyridones were calculated by the CNDO/CI method.Transition energies, intensities and assignments were compared with the u.v. spectra recorded for the first time on all the methyl.substituted isomers under similar conditions in non-aqueous solvents.Ground state properties of the same compounds were calculated after a full geometry optimization using the CNDO/2 and MINDO/3 approximations.
A copper nitride catalyst for the efficient hydroxylation of aryl halides under ligand-free conditions
Mitsudome, Takato,Mizugaki, Tomoo,Xu, Hang,Yamaguchi, Sho
supporting information, p. 6593 - 6597 (2021/08/10)
Copper nitride (Cu3N) was used as a heterogeneous catalyst for the hydroxylation of aryl halides under ligand-free conditions. The cubic Cu3N nanoparticles showed high catalytic activity, comparable to those of conventional Cu catalysts with nitrogen ligands, demonstrating that the nitrogen atoms in Cu3N act as functional ligands that promote hydroxylation.
Electrochemical-induced hydroxylation of aryl halides in the presence of Et3N in water
Ke, Fang,Lin, Chen,Lin, Mei,Long, Hua,Wu, Mei,Yang, Li,Zhuang, Qinglong
supporting information, p. 6417 - 6421 (2021/08/03)
A thorough study of mild and environmentally friendly electrochemical-induced hydroxylation of aryl halides without a catalyst is presented. The best protocol consists of hydroxylation of different aryl iodides and aryl bromides by water solution in the presence of Et3N under air, affording the target phenols in good isolated yields. Moreover, aryl chlorides were successfully employed as substrates. This methodology also provides a direct pathway for the formation of deoxyphomalone, which displayed a significant anti-proliferation effect.
Photocatalytic synthesis of phenols mediated by visible light using KI as catalyst
Huiqin, Wei,Wu, Mei
supporting information, (2021/11/30)
A transition-metal-free hydroxylation of iodoarenes to afford substituted phenols is described. The reaction is promoted by KI under white LED light irradiation and uses atmospheric oxygen as oxidant. By the use of triethylamine as base and solvent, the corresponding phenols are obtained in moderate to good yields. Mechanistic studies suggest that KI and catalysis synergistically promote the cleavage of C-I bond to form free aryl radicals.
