- Direct spectroscopic detection and EPR investigation of a ground state triplet phenyl oxenium ion
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Oxenium ions are important reactive intermediates in synthetic chemistry and enzymology, but little is known of the reactivity, lifetimes, spectroscopic signatures, and electronic configurations of these unstable species. Recent advances have allowed these short-lived ions to be directly detected in solution from laser flash photolysis of suitable photochemical precursors, but all of the studies to date have focused on aryloxenium ions having closed-shell singlet ground state configurations. To study alternative spin configurations, we synthesized a photoprecursor to the m-dimethylamino phenyloxenium ion, which is predicted by both density functional theory and MRMP2 computations to have a triplet ground state electronic configuration. A combination of femtosecond and nanosecond transient absorption spectroscopy, nanosecond time-resolved Resonance Raman spectroscopy (ns-TR3), cryogenic matrix EPR spectroscopy, computational analysis, and photoproduct studies allowed us to trace essentially the complete arc of the photophysics and photochemistry of this photoprecursor and permitted a first look at a triplet oxenium ion. Ultraviolet photoexcitation of this precursor populates higher singlet excited states, which after internal conversion to S1 over 800 fs are followed by bond heterolysis in ～1 ps, generating a hot closed-shell singlet oxenium ion that undergoes vibrational cooling in ～50 ps followed by intersystem crossing in ～300 ps to generate the triplet ground state oxenium ion. In contrast to the rapid trapping of singlet phenyloxenium ions by nucleophiles seen in prior studies, the triplet oxenium ion reacts via sequential H atom abstractions on the microsecond time domain to ultimately yield the reduced m-dimethylaminophenol as the only detectable stable photoproduct. Band assignments were made by comparisons to computed spectra of candidate intermediates and comparisons to related known species. The triplet oxenium ion was also detected in the ns-TR3 experiments, permitting a more clear assignment and identifying the triplet state as the π,π? triplet configuration. The triplet ground state of this ion was further supported by photolysis of the photoprecursor in an ethanol glass at ～4 K and observing a triplet species by cryogenic EPR spectroscopy.
- Li, Ming-De,Albright, Toshia R.,Hanway, Patrick J.,Liu, Mingyue,Lan, Xin,Li, Songbo,Peterson, Julie,Winter, Arthur H.,Phillips, David Lee
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Read Online
- Thiol-reactive derivatives and use thereof
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The present invention relates to a thiol-reactive rosamine derivative and uses of labeling tau thereof, inhibiting tau agglutination, oligomerizing tau, and inhibiting the formation of disulfide bond between tau molecules. The thiol-reactive rosamine derivative is represented by chemical formula 1 or is pharmaceutically acceptable salt thereof.COPYRIGHT KIPO 2016
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Paragraph 0069-0071
(2017/06/02)
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- Room-temperature copper-catalyzed arylation of dimethylamine and methylamine in neat water
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The first room-temperature copper-catalyzed arylations of dimethylamine and methylamine in neat water have been developed. Using a combination of CuI and 6,7-dihydroquinolin-8(5 H)-one oxime as catalyst, dimethylamine is arylated with various aryl halides to give the corresponding products in good to excellent yields. Further, this catalysis enables the selective arylation of methylamine to afford the high yields of monoarylated methylamines as the sole products.
- Wang, Deping,Kuang, Daizhi,Zhang, Fuxing,Yang, Chunlin,Zhu, Xiaoming
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supporting information
p. 714 - 718
(2015/03/18)
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- Mechanism study on Raney nickel-catalyzed amination of resorcinol
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Amination of resorcinol catalyzed by Raney nickel has been examined with good yield. Using the first principle density functional theory, some detailed mechanism of the amination of resorcinol on the Ni(111) surface is explored. The resorcinol is adsorbed on the Ni surface at the hollow site to form ketone by isomerization. The isomerization has a barrier of 122.1 kJ/mol. Ketone can couple with secondary amine mediated by resorcinol to afford hemiaminal. For the formation of hemiaminal, the steric effect of the alkyl group of secondary amine is obvious. Hemiaminal undergoes dehydration to get final product, which occurs by the preferred adsorption in the bridge site, cleavage of CO bond initially, followed by subsequent cleavage of CH bond.
- Ge, Xin,Pan, Jiong-Bin,Qian, Chao,Feng, Lie,Chen, Yun-Bin,Chen, Xin-Zhi
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p. 201 - 207
(2014/01/23)
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- Boron dipyrromethene as a fluorescent caging group for single-photon uncaging with long-wavelength visible light
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Caged compounds are useful tools for precise spatiotemporal modulation of cell functions, but in most cases uncaging requires ultraviolet (UV) light, which is cytotoxic and has limited tissue penetration. Therefore, caged compounds that can be activated by longer-wavelength light are required. Here we describe a novel photoelimination reaction of 4-aryloxy boron dipyrromethene (BODIPY) derivatives and show that BODIPY can function as a caging group for phenol groups. We developed a novel BODIPY-caged histamine compound, which is photoactivatable with blue-green visible light to stimulate cultured HeLa cells in a spatiotemporally well-controlled manner. This caging strategy is expected to be widely applicable to develop tools for probing various cellular functions. (Chemical Equation Presented).
- Umeda, Nobuhiro,Takahashi, Hironori,Kamiya, Mako,Ueno, Tasuku,Komatsu, Toru,Terai, Takuya,Hanaoka, Kenjiro,Nagano, Tetsuo,Urano, Yasuteru
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p. 2242 - 2246
(2015/02/19)
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- RANEY nickel-catalyzed reductive N-methylation of amines with paraformaldehyde: Theoretical and experimental study
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RANEY Ni-catalyzed reductive N-methylation of amines with paraformaldehyde has been investigated. This reaction proceeds in high yield with water as a byproduct. RANEY Ni can be easily recovered and reused with a slight decrease of the yield. Using density functional theory (DFT), the mechanism of RANEY Ni-catalyzed reductive N-methylation is discussed in detail. The reaction pathway involves the addition of amine with formaldehyde, dehydration to form the imine and hydrogenation. In the transition state of hemiaminal dehydration, the C-O bond cleavage of the aromatic amine is more difficult than that of the aliphatic amine. For the aromatic amine, a higher energy barrier must be overcome, which results in a relatively low yield. After addition of amine with formaldehyde and dehydration, imine is obtained and preferred to adsorb on the bridge site of the Ni(111) surface. The preferential pathways of imine hydrogenation involve the pre-adsorbed hydrogen atom attacking the nitrogen atom of the imine. The energy barrier of hydrogenation is much lower than that of addition and dehydration. Thus, the hydrogenation of imine is a relatively rapid reaction step. In the reductive N-methylation of secondary amine, the possible dehydration pathway is different from the one of the primary amine. In the dehydration of the secondary amine, the intermediate hemiaminal is initially adsorbed on the bridge site of the Ni(111) surface, then undergoes C-O bond cleavage, and eventually the hydroxyl is located in the bridge site. With the final hydrogenation, the product is obtained by adsorption on the top site of the Ni(111) surface.
- Ge, Xin,Luo, Chenxi,Qian, Chao,Yu, Zhiping,Chen, Xinzhi
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p. 43195 - 43203
(2015/02/19)
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- A quantitative assessment of the production of OH and additional oxidants in the dark Fenton reaction: Fenton degradation of aromatic amines
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This paper reports the results of a kinetic study into the transformation of 2,4- and 3,4-dichloroaniline (2,4-DCA, 3,4-DCA) and of methyl yellow (MY) with the Fenton reagent in aqueous solution. All the substrates can be degraded in the presence of Fe(II) + H2O2, but the reaction between Fe(II) and H2O2 causes substrate degradation and Fe(II) oxidation within seconds under the adopted conditions. The HPLC, GC-MS and IC analyses only allow the monitoring of the reaction after all Fe(II) has been consumed, when degradation proceeds more slowly via Fe(III) reduction to Fe(II). Substrate degradation in the first part of the reaction was studied by stopped-flow spectrophotometry, using MY as substrate. The results are consistent with a reaction involving OH, where both Fe(II) and H 2O2 compete with MY for the hydroxyl radical. However, the experimental data indicate that OH is unlikely to be the only product of the reaction between Fe(II) and H2O2. Another species, possibly the ferryl ion (FeO2+), is formed as well but has a negligible role in MY degradation. The Fenton reaction would thus yield both OH (about 60% at pH 2) and ferryl (about 40%), and the 60:40 branching ratio between OH and the other species is compatible with additional data here reported concerning the degradation of 2,4-DCA and 3,4-DCA in the first ferrous step of the Fenton reaction. The reported findings will hopefully indicate a way out of a long-lasting controversy concerning the mechanism of the Fenton process, also suggesting an approach to quantitatively determine the formation yields of the reactive species as well as a strategy to identify the reactant that is actually involved in substrate transformation.
- Minero, Claudio,Lucchiari, Mirco,Maurino, Valter,Vione, Davide
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p. 26443 - 26450
(2013/12/04)
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- Mild cleavage of aryl mesylates: Methanesulfonate as potent protecting group for phenols
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A mild protocol for the chemoselective deprotection of aryl methanesulfonates is described. The transformation can be conducted on highly functionalized substrates and renders the methanesulfonate a useful, previously underutilized protecting group for phenols.
- Ritter, Tobias,Stanek, Kyrill,Larrosa, Igor,Carreira, Erick M.
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p. 1513 - 1514
(2007/10/03)
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- Oxyaniliniums as acetylcholinesterase inhibitors for the reversal of neuromuscular block
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A series of oxyanilinium-based AChE inhibitors have been synthesised and tested for the reversal of vecuronium-induced neuromuscular block. Several compounds, for example 2-hydroxy- and 2-methoxy-N,N-dimethyl-N-allylanilinium bromide (3 and 6) showed comparable reversal potencies to edrophonium and clean in vivo cardiovascular profiles.
- Grove, Simon J.A.,Kaur, Jasmit,Muir, Alan W.,Pow, Eleanor,Tarver, Gary J.,Zhang, Ming-Qiang
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p. 193 - 196
(2007/10/03)
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- Free electron transfer from several phenols to radical cations of non-polar solvents
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Electron-transfer reactions from phenols to parent radical cations of solvents were studied using pulse radiolysis. Phenols bearing electron-withdrawing, electron-donating and bulky substituents were investigated in non-polar solvents such as cyclohexane, n-dodecane, n-butyl chloride and 1,2-dichloroethane. The experiments revealed the direct, synchronous formation of phenoxyl radicals and phenol radical cations in all cases and in nearly the same relative amounts. This was explained by two competing electron-transfer channels which depend on the geometry of encounter between the parent solvent radical cations and the solute phenol molecules. The mechanism is analysed at a microscopic level, treating diffusion as a slow process and the local electron transfer as an extremely rapid event. Furthermore, the effect of various phenol substituents and solvent types on the electron-transfer mechanism and on the decay kinetics of the solute phenol radical cations was analysed. The results were further substantiated using a quantum chemical approach.
- Ganapathi,Hermann,Naumov,Brede
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p. 4947 - 4955
(2007/10/03)
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- Process for the preparation of aminophenols
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Process for the preparation of aminophenols with an increased proportion of the meta isomer comprising reacting hydrogen peroxide in a superacid liquid medium with anilines, N-alkylaniline, or N,N-dialkylanilines for a time and a temperature, ranging from about -50° C. to 0° C., sufficient to form the aminophenols.
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- Hydroxylation directe d'anilines en aminophenols
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Anilines react with hydrogen peroxide in SbF5-HF to give aminophenols.The formation of the products can be accounted for by the reaction of the electrophile H3O2+ on the anilinium ions.For compounds 1a-4a, the reaction yields three possible aminophenols, the meta isomer being the major product.The process is more selective with ortho toluidine 5a and para toluidine 6a, giving aminophenol(s) 5c (42percent)) and 5e (21percent), and 6c (71percent), respectively.With meta toluidine 7a, only aminophenol 7d (35percent) can be isolated from the complex reaction mixture, ring substitution pattern of the substrate favoring para hydroxylation.
- Jacquesy, Jean-Claude,Jouannetaud, Marie-Paule,Morellet, Guy,Vidal, Yves
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p. 625 - 629
(2007/10/02)
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- DIRECT CONVERSION OF ANILINES INTO AMINOPHENOLS
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Hydroxylation of anilines by hydrogen peroxide in SbF5-HF yields the three possible aminophenols, the meta isomer being the major product.The reaction implies attack of protonated hydrogen peroxide H3O2(1+) on the N-protonated substrate.
- Jacquesy, Jean-Claude,Jouannetaud, Marie-Paule,Morellet, Guy,Vidal, Yves
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p. 1479 - 1482
(2007/10/02)
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- Indolyl phthalide compounds
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3-Aryl-3-indolylphthalides, 3-aryl-3-pyrrolylphthalides and 3-aryl-3-carbazolylphthalides prepared by interaction of the appropriate 2-(heteroaryl)carbonylbenzoic acid and the appropriate phenylamine, and 3,3-bis(indolyl)phthalides prepared by the interaction of the appropriate 2-(indolyl)carbonylbenzoic acid and the appropriate indole are useful as color formers in pressure-sensitive carbonless duplicating systems, thermal marking systems and hectographic copying systems.
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- Phthalide compounds, processes and marking systems
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3-Aryl-3-indolylphthalides, 3-aryl-3-pyrrolylphthalides and 3-aryl-3-carbazolylphthalides prepared by interaction of the appropriate 2-(heteroaryl)carbonylbenzoic acid and the appropriate phenylamine, and 3,3-bis(indolyl)phthalides prepared by the interaction of the appropriate 2-(indolyl)carbonylbenzoic acid and the appropriate indole are useful as color formers in pressure-sensitive carbonless duplicating systems, thermal marking systems and hectographic copying systems.
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- Heteroarylphthalides
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3-Aryl-3-indolylphthalides, 3-aryl-3-pyrrolylphthalides and 3-aryl-3-carbazolylphthalides prepared by interaction of the appropriate 2-(heteroaryl)carbonylbenzoic acid and the appropriate phenylamine, and 3,3-bis(indolyl)-phthalides prepared by the interaction of the appropriate 2-(indolyl)carbonylbenzoic acid and the appropriate indole are useful as color formers in pressure-sensitive carbonless duplicating systems, thermal marking systems and hectographic copying systems.
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