- Energetics of an n → π* interaction that impacts protein structure
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(Figure Presented) The trans/cis ratio of the amide bond in N-formylproline phenylesters correlates with electron withdrawal by a para substituent. The slope of the Hammett plot (ρ = 0.26) is indicative of a substantial effect. This effect arises from a favorable n → π* interaction between the amide oxygen and ester carbonyl. In a polypeptide chain, an analogous interaction can stabilize the conformation of trans peptide bonds, α-helices, and polyproline type-II helices.
- Hodges, Jonathan A.,Raines, Ronald T.
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Read Online
- Designing bimetallic zeolitic imidazolate frameworks (ZIFs) for aqueous catalysis: Co/Zn- ZIF-8 as a cyclic-durable catalyst for hydrogen peroxide oxidative decomposition of organic dyes in water
-
ZIF-8 is well known hybrid material that is self-assembled from inorganic and organic moieties. It has several potential applications due to its unique structure. One of these potential applications is in advanced oxidation processes (AOP) via a heterogeneous catalysis system. The use of modified ZIF-8/H2O2for the destruction of the azo dye methyl orange (MO) is presented in this work to explore its efficacy. This work presents the bimetallic Co/Zn-ZIF-8 as an efficient catalyst to promote H2O2oxidation of the MO dye. Co/Zn-ZIF-8 was synthesized through a hydrothermal process, and the pristine structure was confirmed using XRD, FTIR, and XPS. The Co/Zn-ZIF-8/H2O2system successfully decolorized MO at the selected pH 6.5. It was found that more than 90% of MO (10 ppm) was degraded within only about 50 minutes. Proposed radical and redox mechanisms are presented for H2O2decomposition where the redox mechanism is suggested to predominate via a Co(II)/Co(III) redox consecutive cyclic process.
- Abuzalat, Osama,Alkordi, Mohamed H.,Baraka, Ahmad,Basuni, Mustafa,Tantawy, Hesham
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p. 6025 - 6036
(2022/03/31)
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- Synthesis method of substituted phenol
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The invention provides a synthesis method of substituted phenol. The target product substituted phenol is prepared by taking substituted benzene as an initial raw material, and the whole synthetic process is high in selectivity, high in yield, convenient to operate and high in atom economy.
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Paragraph 0099; 0105; 0109; 0113
(2020/09/16)
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- Optimizing the crystallization process of conjugated polymer photocatalysts to promote electron transfer and molecular oxygen activation
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Photocatalytic reactive oxygen species (ROS)-induced reactions provide an appealing method to solve the environmental and energy issues, whereas the current oxidation reaction generally suffered from low efficiency and poor selectivity due to uncontrollable O2 activation process. In view of the existence of competitive electron and energy transfer pathway, we propose that highly efficient superoxide radical anion (·O2?) generation can be achieved by optimizing the order degree of the photocatalyst. Herein, by taking carbon nitride polymer as an example, we optimized the crystallization process of carbon nitride polymer by selecting precursors of different polymerization degrees with a molten salt method. Benefiting from the high crystallinity, extended π-conjugated system and strong van der-Waals interactions between interlayers, the modified carbon nitride polymer exhibited accelerated charge transport and enhancement in electron induced molecular oxygen activation reactions under visible light. Consequently, the CCN-P exhibits about 1.5 times higher conversion rate in hydroxylation of phenylboronic acid and over 6-fold faster degradation rate in Rh B organic pollutants photodegradation with respect to pristine carbon nitride. This study provides an in-depth understanding on the optimization of the O2 activation process and the design of advanced photocatalysts.
- Anpo, Masakazu,Cheng, Jiajia,Huang, Caijin,Ou, Honghui,Ren, Wei,Wang, Xinchen
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p. 636 - 645
(2020/07/27)
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- Method for N-methylation reaction of nitro-compound
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The invention discloses a method for direct N-methylation reaction by taking a nitro-compound as a raw material. The method adopts a Cu-based catalyst and polyformaldehyde and can realize the direct N-methylation reaction of the nitro-compound under mild conditions.
- -
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Paragraph 0050-0054
(2019/01/23)
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- Heterogeneous Palladium–Chitosan–CNT Core–Shell Nanohybrid Composite for Ipso-hydroxylation of Arylboronic Acids
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Abstract: A novel palladium-nanohybrid (Pd–Chitosan–CNT) catalytic composite has been developed using CNT–chitosan nanocomposite and palladium nitrate. The prepared catalytic platform displays excellent catalytic reactivity for the ipso-hydroxylation of various arylboronic acids with a mild oxidant aqueous H2O2 at room temperature, affording the corresponding phenols in excellent yields. Significantly, the easy recovery and reusability by simple manipulation demonstrate the green credentials of this catalytic platform. Graphical Abstract: [Figure not available: see fulltext.]
- Shin, Eun-Jae,Kim, Han-Sem,Joo, Seong-Ryu,Shin, Ueon Sang,Kim, Seung-Hoi
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- Synergistic catalysis of Cu+/Cu0 for efficient and selective N-methylation of nitroarenes with para-formaldehyde
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In this paper, an inexpensive heterogeneous copper nanoparticles catalyst derived from CuAl-layered double hydroxide via an in situ topotactic transformation process was developed. Cu nanoparticles with uniform size were homogeneously dispersed on amorphous Al2O3 with strong metal-support interaction. Characterization results reveals that the Cu0 and Cu+ were simultaneously formed with Cu+ species as the dominant sites on the surface during the reduction process. The resultant catalyst Cu/Al2O3 demonstrates high catalytic activity, selectivity and durability for the reductive N-methylation of easily available nitroarenes in a cost-efficient, environmentally friendly and cascade manner. A broad spectrum of nitroarenes could be efficiently N-methylated to their corresponding N,N-dimethyl amines with good compatibility of various functional groups. The protocol is also applicable for the late-stage functionalization of biologically and pharmaceutically active nitro molecules. A structure-function relationship discloses that Cu0 and Cu+ sites on the surface pronouncedly boosts the reaction efficiency in a synergistic manner, in which Cu0 could facilitate H2 production and N-methylation of anilines, while Cu+ is considerably more active and participates in the overall process of the selective N-methylation of nitroarenes. Moreover, the catalyst also showed a strong stability and could be easily separated for successive reuses without an appreciable loss in activity and selectivity.
- Dong, Xiaosu,Wang, Zhaozhan,Yuan, Youzhu,Yang, Yong
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p. 304 - 313
(2019/07/02)
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- Cyanide antidote synthesis method
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The invention relates to a cyanide antidote synthesis method, which comprises: adding a formaldehyde solution and p-nitroanisole in an ethanol solution, adjusting the pH value to 4 with hydrochloric acid, heating, slowly adding iron powder, carrying out a reaction after the adding to obtain 4-dimethylaminoanisole, adding the 4-dimethylaminoanisole to toluene, adding aluminum trichloride, carryingout heating reflux, removing the methyl, cooling, adding a saturated sodium bicarbonate solution, filtering out the solid while hot, separating the liquid, carrying out water washing on the toluene phase, separating the liquid, carrying out pressure reducing evaporation to remove the toluene, and carrying out heating evaporation to obtain the product. According to the present invention, the product obtained through the curing has the purity of more than 99% and the yield of more than 80%; and the method has advantages of cheap and easily-available raw materials, no dangerous operation, less wastewater generation, low environmental pollution and high overall yield, and is suitable for large-scale production.
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Paragraph 0030; 0033; 0034
(2018/07/30)
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- POLYMERIC AMINE SYNERGIST
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A polymeric amine synergist is disclosed herein. An example of the polymeric amine synergist includes an aniline moiety, a polyethylene glycol chain, and an ether linkage attaching one end of the polyethylene glycol chain to the aniline moiety. The polymeric amine synergist may be included in a photo curable ink composition.
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Paragraph 0039; 0081; 0082
(2018/05/03)
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- Transformation of N, N-Dimethylaniline N-Oxides into Diverse Tetrahydroquinoline Scaffolds via Formal Povarov Reactions
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A one-pot protocol for the assembly of diversely functionalized tetrahydro-, hexahydrofuro-, hexahydropyrano-, and tetrahydrobenzofuroquinolines from N,N-dimethylaniline N-oxides and various electron-rich olefins in a tandem Polonovski-Povarov sequence is reported. Following activation of the N-O bond with Boc2O, an exocyclic iminium ion is unveiled upon exposure to tin(IV) chloride. A formal inverse-electron-demand aza-Diels-Alder cyclization generates the tetrahydroquinoline core of 29 examples in up to 92% yield.
- Bush, Timothy S.,Yap, Glenn P. A.,Chain, William J.
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supporting information
p. 5406 - 5409
(2018/09/13)
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- Efficient and versatile catalytic systems for the n-methylation of primary amines with methanol catalyzed by n-heterocyclic carbene complexes of iridium
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Efficient and versatile catalytic systems were developed for the N-methylation of both aliphatic and aromatic primary amines using methanol as the methylating agent. Iridium complexes bearing an Nheterocyclic carbene (NHC) ligand exhibited high catalytic performance for this type of transformation. For aliphatic amines, selective N,N-dimethylation was achieved at low temperatures (50-90 °C). For aromatic amines, selective N-monomethylation and selective N,N-dimethylation were accomplished by simply changing the reaction conditions (presence or absence of a base with an appropriate catalyst). These findings can be used to develop methods for synthesizing useful amine compounds having N-methyl or N,N-dimethyl moieties.
- Toyooka, Genki,Tuji, Akiko,Fujita, Ken-Ichi
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p. 4617 - 4626
(2019/02/01)
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- Highly Selective N-Monomethylanilines Synthesis from Nitroarene and Formaldehyde via Kinetically Excluding of the Thermodynamically Favorable N,N-Dimethylation Reaction
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The synthesis of N-monomethylamine remains a challenging topic because the N,N-dimethylation reaction is thermodynamically favorable. In this work, the kinetically controlled N-monomethylamine synthesis from nitroarene and paraformaldehyde/H2 is reported to have superhigh N-monomethylamine selectivity in the presence of a Pd/TiO2 catalyst. The superior selectivity should be attributed to the preferential adsorption of the primary amine over N-monomethylamine on the Pd/TiO2 surface, as elucidated by NH3/Me2NH-TPD, while the excellent catalytic activity could be associated with the good H2 activation ability and high amine adsorbing capacity of the catalyst, as elucidated by NH3-TPD and H2-TPR tests. Good results were obtained with a variety of nitroarenes containing methyl, methoxyl, hydroxyl, fluoride, trifluoromethyl, ester, and amide substituents as starting materials, and the potential synthetic utility of this protocol in pharmaceutical is illustrated by N-monomethylation of drug molecules, such as clinidipine, nimesulide, procaine, and methyl aminosalicylate.
- Wang, Hongli,Yuan, Hangkong,Yang, Benqun,Dai, Xingchao,Xu, Shan,Shi, Feng
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p. 3943 - 3949
(2018/05/23)
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- Recyclable CNT-chitosan nanohybrid film utilized in copper-catalyzed aerobic ipso-hydroxylation of arylboronic acids in aqueous media
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A convenient heterogeneous catalytic system consisting of recyclable and reusable carbon nanotube-chitosan nanohybrid film and copper salt was developed for the aerobic ipso-hydroxylation of arylboronic acids. A variety of arylboronic acids bearing electron-withdrawing or electron-donating groups were smoothly transformed at room temperature in water to afford the corresponding phenols in high yields.
- Kim, Han-Sem,Joo, Sung-Ryu,Shin, Ueon Sang,Kim, Seung-Hoi
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p. 4597 - 4601
(2018/11/23)
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- Expedient Synthesis of N-Methyl- and N-Alkylamines by Reductive Amination using Reusable Cobalt Oxide Nanoparticles
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N-Methyl- and N-alkylamines represent important fine and bulk chemicals that are extensively used in both academic research and industrial production. Notably, these structural motifs are found in a large number of life-science molecules and play vital roles in regulating their activities. Therefore, the development of convenient and cost-effective methods for the synthesis and functionalization of amines by using earth-abundant metal-based catalysts is of scientific interest. In this regard, herein we report an expedient reductive amination process for the selective synthesis of N-methylated and N-alkylated amines by using nitrogen-doped, graphene-activated nanoscale Co3O4-based catalysts. Starting from inexpensive and easily accessible nitroarenes or amines and aqueous formaldehyde or aldehydes in the presence of formic acid, this cost-efficient reductive amination protocol allows the synthesis of various N-methyl- and N-alkylamines, amino acid derivatives, and existing drug molecules.
- Senthamarai, Thirusangumurugan,Murugesan, Kathiravan,Natte, Kishore,Kalevaru, Narayana V.,Neumann, Helfried,Kamer, Paul C. J.,Jagadeesh, Rajenahally V.
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p. 1235 - 1240
(2018/02/09)
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- A competing, dual mechanism for catalytic direct benzene hydroxylation from combined experimental-DFT studies
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A dual mechanism for direct benzene catalytic hydroxylation is described. Experimental studies and DFT calculations have provided a mechanistic explanation for the acid-free, TpxCu-catalyzed hydroxylation of benzene with hydrogen peroxide (Tpx = hydrotrispyrazolylborate ligand). In contrast with other catalytic systems that promote this transformation through Fenton-like pathways, this system operates through a copper-oxyl intermediate that may interact with the arene ring following two different, competitive routes: (a) electrophilic aromatic substitution, with the copper-oxyl species acting as the formal electrophile, and (b) the so-called rebound mechanism, in which the hydrogen is abstracted by the Cu-O moiety prior to the C-O bond formation. Both pathways contribute to the global transformation albeit to different extents, the electrophilic substitution route seeming to be largely favoured.
- Vilella, Laia,Conde, Ana,Balcells, David,Mar Díaz-Requejo,Lledós, Agustí,Pérez, Pedro J.
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p. 8373 - 8383
(2017/11/27)
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- A catalytic oxidation fragrant boron class compound preparing phenol method (by machine translation)
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The invention discloses a method for catalytic oxidation of phenolic compounds fragrant boron class compound synthesis method, the flux in the solvent in the aqueous solution, under the action of alkali, adding hydrazine hydrate or acid hydrazides catalyst, catalytic oxidation fragrant boron class compound directly for the preparation of phenolic compound. The invention of the method of preparation of the phenol compound, the catalyst is a cheap hydrazine hydrate or hydrazine compound, the oxidizing agent is atmospheric pressure of air or oxygen, the reaction does not need good and activeness metal catalyst, is extensive and stable substrate, substrate-sensitive functional group compatibility good and wide range of application. In the optimized under the reaction conditions, the yield of the target product separation up to 99%. (by machine translation)
- -
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Paragraph 0027; 0039; 0040
(2017/08/08)
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- METHOD FOR SYNTHESIZING PHENOL USING METAL CATALYST
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The present invention relates to a method for synthesizing phenol using a metal catalyst and, more specifically, to a method for preparing phenol, which is a product of cross-coupling reaction by performing reaction of aryl halide and 2-dimethylaminoethanol in the presence of a metal catalyst. According to the present invention, phenol, as a product of cross-coupling reaction by performing reaction of aryl halide and 2-dimethylaminoethanol in the presence of a metal catalyst, can be synthesized with high yield. Also, various phenols having substituents can be synthesized.COPYRIGHT KIPO 2017
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Paragraph 0058; 0060
(2017/10/26)
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- SYNTHESIS OF CEPHALOSPORIN COMPOUNDS
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Provided herein is a method for the synthesis of cephalosporin antibiotic compounds comprising a palladium-catalyzed coupling reaction. Provided herein are methods for the synthesis of cephalosporin compounds of formula (I) employing a palladium-catalyzed alkylation reaction, as well as compositions related to the same. In an aspect, provided herein is a method for preparing a compound of formula (II), or a salt thereof, comprising the step of admixing, e.g., reacting, a compound of formula (III), or a salt thereof, with a nucleophile (Nuc) in the presence of reagents comprising: (a) a palladium source; and (b) a palladium-binding ligand, to form a compound of formula (II), or a salt thereof.
- -
-
Paragraph 0228; 0229; 0230; 0231
(2016/02/29)
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- A series of BiO: XIy/GO photocatalysts: Synthesis, characterization, activity, and mechanism
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A series of bismuth oxyiodide (BiOxIy)-grafted graphene oxide (GO) sheets with different GO contents were synthesized through a simple hydrothermal method. This is the first report where four composites of BiOI/GO, Bi4O5I2/GO, Bi7O9I3/GO, and Bi5O7I/GO have been characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. The assembled BiOxIy/GO composites exhibited excellent photocatalytic activities in the degradation of crystal violet (CV) under visible light irradiation. The order of rate constants was as follows: Bi7O9I3/GO > Bi4O5I2/GO > Bi4O5I2 > Bi7O9I3 > Bi5O7I/GO > BiOI/GO > BiOI > Bi5O7I > GO. The photocatalytic activity of the Bi7O9I3/GO (or Bi4O5I2/GO) composite reached a maximum rate constant of 0.351 (or 0.322) h-1, which was 1.8 (or 1.7) times higher than that of Bi7O9I3 (or Bi4O5I2), 6-7 times higher than that of BiOI/GO, and 119-130 times higher than that of BiOI. The quenching effects of different scavengers and electron paramagnetic resonance demonstrated that the superoxide radical (O2-) played a major role and holes (h+) and hydroxyl radicals (OH) played a minor role as active species in the degradation of crystal violet (CV) and salicylic acid (SA). Possible photodegradation mechanisms are proposed and discussed in this research.
- Chou, Shang-Yi,Chung, Wen-Hsin,Chen, Li-Wen,Dai, Yong-Ming,Lin, Wan-Yu,Lin, Jia-Hao,Chen, Chiing-Chang
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p. 82743 - 82758
(2016/11/01)
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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)
-
- Phenyl Esters Are Potent Inhibitors of Caseinolytic Protease P and Reveal a Stereogenic Switch for Deoligomerization
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Caseinolytic protease P (ClpP) represents a central bacterial degradation machinery that is involved in cell homeostasis and pathogenicity. The functional role of ClpP has been studied by genetic knockouts and through the use of beta-lactones, which remain the only specific inhibitors of ClpP discovered to date. Beta-lactones have served as chemical tools to manipulate ClpP in several organisms; however, their potency, selectivity and stability is limited. Despite detailed structural insights into the composition and conformational flexibility of the ClpP active site, no rational efforts to design specific non-beta-lactone inhibitors have been reported to date. In this work, an unbiased screen of more than 137000 compounds was used to identify five phenyl ester compounds as highly potent ClpP inhibitors that were selective for bacterial, but not human ClpP. The potency of phenyl esters largely exceeded that of beta-lactones in ClpP peptidase and protease inhibition assays and displayed unique target selectivity in living S. aureus cells. Analytical studies revealed that while phenyl esters are cleaved like native peptide substrates, they remain covalently trapped as acyl-enzyme intermediates in the active site. The synthesis of 36 derivatives and subsequent structure-activity relationship (SAR) studies provided insights into conserved structural elements that are important for inhibition potency and acylation reactivity. Moreover, the stereochemistry of a methyl-substituent at the alpha position to the ester, resembling amino acid side chains in peptide substrates, impacted ClpP complex stability, causing either dissociation into heptamers or retention of the tetradecameric state. Mechanistic insights into this intriguing stereo switch and the phenyl ester binding mode were obtained by molecular docking experiments.
- Hackl, Mathias W.,Lakemeyer, Markus,Dahmen, Maria,Glaser, Manuel,Pahl, Axel,Lorenz-Baath, Katrin,Menzel, Thomas,Sievers, Sonja,B?ttcher, Thomas,Antes, Iris,Waldmann, Herbert,Sieber, Stephan A.
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supporting information
p. 8475 - 8483
(2015/07/15)
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- Reaction of 1,2-difunctionalized ethanes with aryl iodides in copper-catalyzed cross-coupling: Application to synthesis of phenols
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A series of 1,2-difunctionalized ethanes, such as ethylene glycol, 2-aminoethanol, 1,2-diaminoethane, 2-dimethylaminoethanol N',N'-dimethylethane-1,2-diamine, were investigated to test the reactivity with aryl iodides in the presence of copper catalysts. Under the reaction conditions, they produce the various Cheteroatom cross-coupled products. Interestingly, ethylene glycol and 2-dimethylaminoethanol afforded mainly the phenolic compounds while the others produced different cross-coupled products. Although ethylene glycol and 2-dimethylaminoethanol resulted in the same product, their behaviors in the reaction were quite different: ethylene glycol appears to mostly act as the ligand and 2-dimethylaminoethanol appears to serve as both the ligand and reactant. This finding led to a copper-catalyzed synthesis of phenols using either ethylene glycol or 2-dimethylaminoethanol, which can be applied to a variety of aryl iodides, providing an alternative synthetic route to phenols.
- Kim, Jihye,Battsengel, Oyunsaikhan,Liu, Yajun,Chae, Junghyun
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supporting information
p. 2833 - 2840
(2016/02/05)
-
- Carbon Dioxide Reduction to Methylamines under Metal-Free Conditions
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The first metal-free catalysts are reported for the methylation of amines with carbon dioxide. Proazaphosphatrane superbases prove to be highly active catalysts in the reductive functionalization of CO2, in the presence of hydroboranes. The new methodology enables the methylation of N-H bonds in a wide variety of amines, including secondary amines, with increased chemoselectivity. Organocatalysis: Proazaphosphatrane superbases prove to be highly active catalysts in the reductive functionalization of CO2, in the presence of hydroboranes. The new method makes possible the methylation of N-H bonds in a wide variety of amines, including secondary amines (see picture), with increased chemoselectivity.
- Blondiaux, Enguerrand,Pouessel, Jacky,Cantat, Thibault
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p. 12186 - 12190
(2016/02/23)
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- Aryl imidazylates and aryl sulfates as electrophiles in metal-free ArSN1 reactions
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Some oxygen-bonded substituents were investigated as leaving groups in photoinduced ArSN1 reactions. Irradiation of aryl imidazylates and of the corresponding imidazolium salts mainly caused homolysis of the ArO-S bond. However, previously unexplored trifluoroethoxy aryl sulfates were found to undergo efficient metal-free arylation. The sulfates were conveniently generated in situ by dissolving the corresponding imidazolium salts in basic 2,2,2-trifluoroethanol.
- Qrareya, Hisham,Protti, Stefano,Fagnoni, Maurizio
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p. 11527 - 11533
(2015/01/16)
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- Continuous-flow synthesis of functionalized phenols by aerobic oxidation of grignard reagents
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Phenols are important compounds in chemical industry. An economical and green approach to phenol preparation by the direct oxidation of aryl Grignard reagents using compressed air in continuous gas-liquid segmented flow systems is described. The process tolerates a broad range of functional groups, including oxidation-sensitive functionalities such as alkenes, amines, and thioethers. By integrating a benzyne-mediated in-line generation of arylmagnesium intermediates with the aerobic oxidation, a facile three-step, one-flow process, capable of preparing 2-functionalized phenols in a modular fashion, is established. Putting on airs: Aerobic oxidation of (hetero)aryl Grignard reagents using compressed air proceeds with a gas-liquid continuous-flow system, thus enabling preparation of fucntionalized phenols. By integrating an in-line generation of ArMgBr intermediates with the aerobic oxidation, ortho-functionalized phenols can be assembled. The method demonstrates good functional-group (FG) compatibility, mild reaction conditions, and short reaction times.
- He, Zhi,Jamison, Timothy F.
-
supporting information
p. 3353 - 3357
(2014/04/03)
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- Metal-free arylations via photochemical activation of the Ar-OSO 2R bond in aryl nonaflates
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The photolysis of electron-rich aryl nonaflates (ArONfs) in protic media was investigated and heterolysis of the Ar-OS bond (from 3ArONf) took place. The reaction generated a triplet phenyl cation that added to π-bond nucleophiles. This metal-free arylation method was made further useful by adopting in situ preparation of ArONf from the corresponding phenol.
- Raviola, Carlotta,Canevari, Veronica,Protti, Stefano,Albini, Angelo,Fagnoni, Maurizio
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supporting information
p. 2704 - 2708
(2013/10/08)
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- One-pot synthesis of N,N-dimethylanilines from nitroarenes with skeletal Cu as chemoselective catalyst
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A range of N,N-dimethylanilines were synthesized with excellent yields in one-pot by the hydrogenation and alkylation of nitroarenes with H2 and HCHO over quenched skeletal Cu catalyst, which provides a facile, economical, and environmentally benign alternative methodology for C-N bonds formation.
- Rong, Zeming,Zhang, Wenjun,Zhang, Peng,Sun, Zhuohua,Lv, Jinkun,Du, Wenqiang,Wang, Yue
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p. 115 - 118
(2013/09/02)
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- Copper(II)-catalyzed hydroxylation of aryl halides using glycolic acid as a ligand
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Copper(II)-catalyzed hydroxylation of aryl halides has been developed to afford functionalized phenols. The protocol utilizes the reagent combination of Cu(OH)2, glycolic acid, and NaOH in aqueous DMSO, all of which are cheap, readily available, and easily removable after the reaction. A broad range of aryl iodides and activated aryl bromides were transformed into the corresponding phenols in excellent yields. Moreover, it has been shown that C-O(alkyl)-coupled product, instead of phenol, can be predominantly formed under similar reaction conditions.
- Xiao, Yan,Xu, Yongnan,Cheon, Hwan-Sung,Chae, Junghyun
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p. 5804 - 5809
(2013/07/25)
-
- The effect of solvent accessible surface on Hammett-type dependencies of infinite dilution 29Si and 13C NMR shifts in ring substituted silylated phenols dissolved in chloroform and acetone
-
Infinite dilution 29Si and 13C NMR chemical shifts were determined from concentration dependencies of the shifts in dilute chloroform and acetone solutions of para substituted O-silylated phenols, 4-R-C6H4-O-SiR′2R″ (R = Me, MeO, H, F, Cl, NMe2, NH2, and CF3), where the silyl part included groups of different sizes: dimethylsilyl (R′ = Me, R″ = H), trimethylsilyl (R′ = R″ = Me), tert-butyldimethylsilyl (R′ = Me, R″ = CMe3), and tert-butyldiphenylsilyl (R′ = C6H5, R″ = CMe3). Dependencies of silicon and C-1 carbon chemical shifts on Hammett substituent constants are discussed. It is shown that the substituent sensitivity of these chemical shifts is reduced by association with chloroform, the reduction being proportional to the solvent accessible surface of the oxygen atom in the Si-O-C link. Copyright
- Blechta, Vratislav,Sabata, Stanislav,Sykora, Jan,Hetflejs, Jiri,Soukupova, Ludmila,Schraml, Jan
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body text
p. 128 - 134
(2012/08/07)
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- Oxidative modification of native protein residues using cerium(IV) ammonium nitrate
-
A new protein modification strategy has been developed that is based on an oxidative coupling reaction that targets electron-rich amino acids. This strategy relies on cerium(IV) ammonium nitrate (CAN) as an oxidation reagent and results in the coupling of tyrosine and tryptophan residues to phenylene diamine and anisidine derivatives. The methodology was first identified and characterized on peptides and small molecules, and was subsequently adapted for protein modification by determining appropriate buffer conditions. Using the optimized procedure, native and introduced solvent-accessible residues on proteins were selectively modified with polyethylene glycol (PEG) and small peptides. This unprecedented bioconjugation strategy targets these under-utilized amino acids with excellent chemoselectivity and affords good-to-high yields using low concentrations of the oxidant and coupling partners, short reaction times, and mild conditions.
- Seim, Kristen L.,Obermeyer, Allie C.,Francis, Matthew B.
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supporting information; experimental part
p. 16970 - 16976
(2011/12/04)
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- Photo-Fenton and photo-Fenton-like processes for the degradation of methyl orange in aqueous medium: Influence of oxidation states of iron
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Degradation of methyl orange (MO) was carried out by the photo-Fenton process (Fe2+/H2O2/UV) and photo-Fenton-like processes (Fe3+/H2O2/UV, Fe2+/S2O82-/UV, and Fe3+/S2O82-/UV) at the acidic pH of 3 using hydrogen peroxide and ammonium persulfate (APS) as oxidants. Oxidation state of iron had a significant influence on the efficiency of photo-Fenton/photo-Fenton-like processes. It was found that a process with a source of Fe3+ ions as the catalyst showed higher efficiency compared to a process with the Fe2+ ion as the catalyst. H2O2 served as a better oxidant for both oxidation states of iron compared to APS. The lower efficiency of APS is attributed to the generation of excess protons which scavenges the hydroxyl radicals necessary for degradation. Further, the sulfate ions produced from S2O82- form a complex with Fe2+/Fe3+ ions thereby reducing the concentration of free iron ions in the solution. This process can also reduce the concentration of hydroxyl radicals in the solution. Efficiency of the various MO degradation processes follows the order: Fe3+/H2O2/UV, Fe3+/APS/UV, Fe2+/H2O2/UV, Fe2+/APS/UV.
- Devi, L. Gomathi,Kumar, S. Girish,Raju, K. S. Anantha,Rajashekhar, K. Eraiah
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experimental part
p. 378 - 385
(2011/10/09)
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- Metal-free cross-coupling reactions of aryl sulfonates and phosphates through photoheterolysis of aryl-oxygen bonds
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Photochemical cleavage of Ar-O bonds in phenyl esters substituted with electron-donating groups offers a convenient method for the arylation of alkenes and arenes. The reaction proceeds by an SN1 mechanism via a triplet phenyl cation to form allylbenzene or biphenyl derivatives under mild conditions (see scheme).
- De Carolis, Marco,Protti, Stefano,Fagnoni, Maurizio,Albini, Angelo
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p. 1232 - 1236
(2007/10/03)
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- Mono-N-methylation of functionalized anilines with alkyl methyl carbonates over NaY faujasites. 4. Kinetics and selectivity
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(Chemical Equation Presented) In the presence of NaY faujasite as the catalyst, the reaction of bifunctional anilines (1-4: XC6H 4-NH2; X = OH, CO2H, CH2OH, and CONH2) with methyl alkyl carbonates [MeOCO2R′: R′ = Me or MeO(CH2)2O(CH2)2] proceeds with a very high mono-N-methyl selectivity (XC6H 4NHMe up to 99%), and chemoselectivity as well, with other nucleophilic functions (OH, CO2H, CH2OH, CONH2) fully preserved from alkylation and/or transesterification reactions. Aromatic substituents, however, modify the relative reactivity of amines 1-4: good evidence suggests that, not only steric and electronic effects, but, importantly, direct acid-base interactions between substituents and the catalyst are involved. Weakly acidic groups (OH, CH2OH, CONH2, pKa ≥ 10) may help the reaction, while aminobenzoic acids (pK a of 4-5) are the least reactive substrates. The solvent polarity also affects the reaction, which is faster in xylene than in the more polar diglyme. The mono-N-methyl selectivity is explained by the adsorption pattern of reagents within the zeolite pores: a BAl2 displacement of the amine on methyl alkyl carbonate should occur aided by the geometric features of the NaY supercavities. Different factors account for the reaction chemoselectivity. Evidence proves that the polarizability of the two nucleophilic terms (NH 2 and X groups) of anilines is relevant, although adsorption and confinement phenomena of reagents promoted by the zeolite should also be considered.
- Selva, Maurizio,Tundo, Pietro,Foccardi, Tommaso
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p. 2476 - 2485
(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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- Atropisomeric benzamides and naphthamides as chiral auxiliaries
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Atropisomeric compounds whose chirality resides in a rotationally restricted aryl-CONR2 bond may be employed as chiral auxiliaries. The electron-withdrawing amide group causes problems in the diastereoselective functionalisation of enolates derived from atropisomeric phenyl esters, but a strategy based on atroposelective nucleophilic addition to a chiral aldehyde followed by stereospecific [3,3] sigmatropic rearrangement allows atropisomeric naphthamides to be used as auxiliaries. The auxiliaries are resolved by dynamic resolution during aminal formation using a proline-derived diamine. The Royal Society of Chemistry 2000.
- Clayden, Jonathan,Helliwell, Madeleine,McCarthy, Catherine,Westlund, Neil
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p. 3232 - 3249
(2007/10/03)
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- Mechanism of dye bleaching upon laser excitation of crystal violet bound to bovine serum albumin
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The laser induced photobleaching of crystal violet non-covalently bound to bovine serum albumin yields leuco crystal violet and Michler's ketone as reaction products. The first step of the bleaching process is postulated to be an electron or hydrogen atom transfer from the protein to the dye moiety.
- Indig, Guilherme L.
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p. 243 - 244
(2007/10/03)
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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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- Preparation and Characterization of Base-Sensitive Destructible Surfactants
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Destructible surfactants 4-n-C12H25C6H4SO2CH2CH2OC6H4X-4 (1, X = N+Me3, NO3-; 2, X = SO3-, K+) were prepared, and their stability/lability characteristics in aqueous micellar solutions with respect to E1cB elimination to give 4-n-C12H25C6H4SO2CH=CH2 (7) and HOC6H4X-4 (8/9) were determined by 1H NMR.In 0.001 and 0.1 M DCl, both 1 and 2 were stable for 24 h at 75 deg C.In D2O alone at 25 deg C, 1 slowly decomposed, and 2 was stable.At 25 deg C, 1 decomposed completely within 10 min in 0.1 M NaHCO3, whereas 2 was more stable in 0.1 M K2CO3.The difference in reactivities for 1 and 2 was ascribed to a combination of electronic and micellar effects.Support for the latter was found in a comparison of 2's behavior with that of 4-MeC6H4SO2CH2CH2OC6H4SO3Na-4 (10).
- Jaeger, David A.,Finley, C. Timothy,Walter, Mark R.,Martin, Craig A.
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p. 3956 - 3959
(2007/10/02)
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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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- New Oxidatively Removable Carboxy Protecting Groups
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2,6-Dimethoxybenzyl esters are readily oxidized by 2,3-dichloro-5,6-dicyano benzoquinone (DDQ) to generate the corresponding carboxylic acids.Phenyl esters substituted with hydroxy, methoxy and dimethylamino groups are also efficiently oxidized by ceric ammonium nitrate (CAN) under pH control conditions.
- Kim, C. U.,Misco, P. F.
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p. 2027 - 2030
(2007/10/02)
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- OZONIZATION OF TRIPHENYLMETHANE DYES.
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The reaction of Malachite Green (MG, 1a), a model compound of triphenylmethane dye, with ozone proceeded via two paths. The first path involved an ozone attack at the dimethylamino moiety to give a N-formylmethylamino derivative. The second path produced 4-(dimethylamino)benzophenone and p-(dimethylamino)phenol. Other ozonized products were also detected. A discussion is presented of the ozonization mechanism.
- Matsui,Nakabayashi,Shibata,Takase
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p. 3312 - 3316
(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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- AMINE OXIDATION. PART 14. ACID-CATLYSED DEOXYGENATION OF SOME N,N-DIMETHYLANILINE N-OXIDES AND REACTIONS OF THE RESULTANT IMINIUM-BENZENIUM DICATIONS
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The recations of N,N-dimethylaniline N-oxide and three substituted derivatives (4-CH3, 4-CH3O, and 4-NO2) in strong acids have been followed by 1H and 13C n.m.r. spetroscopy and product studies.These N-oxides can be deoxygenated in strong acids to give N,N-dimethyliminium-benzenium dications.With the 4-methoxy-substituted N-oxide the reaction, which is helped by the electron-releasing methoxy-substituent, proceeds at room temperature in trifluoroacetic acid (TFA).By contrast the N,N-dimethylaniline N-oxide with an electron-withdrawing 4-nitro-substituent is stable in TFA and requires the stronger acid fluorosulphonic acid for reaction to occur.The mechanisms of these reactions are discussed.
- Smith, John R. Lindsay,Linford, Janet M.,McKeer, Linda C.,Morris, Paul M.
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p. 1099 - 1106
(2007/10/02)
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- One-Electron Redox Potentials of Phenols. Hydroxy- and Aminophenols and Related Compounds of Biological Interest
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The rate constants for reversible electron transfer between a series of substituted phenolate ions and anilines and various substituted phenoxyl or anilino radicals in aqueous solution were measured by observing the formation or depletion of the radicals involved.Nonequilibrium concentrations of the radicals were produced in the presence of the corresponding phenols or anilines by using the pulse radiolysis technique.The relaxation of the system to equilibrium was monitored by optical detection methods.From the equilibrium constants for one-electron transfer, the one-electron redox potentials (E2) for 38 phenolic or anilino type compounds were determined, many of which are natural products.The redox potentials are strongly influenced by electron-donating or -withdrawing substituents at the aromatic system.
- Steenken, S.,Neta, P.
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p. 3661 - 3667
(2007/10/02)
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- Hydrolysis of Esters and Amides in Strongly Basic Solution. Evidence for the Intermediacy of Carbanions
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Kinetic studies of the decomposition of the carbaninons derived from a number of esters and amides of p-nitrophenylacetic acid in strongly basic solution have been carried out.Kinetic solvents isotop effects and the large Hammett ρ value for substituents on the aromatic ring of substituted phenyl esters of p-nitrophenylacetic acid suggest decomposition occurs by an E1cB mechanism.Furthermore, it appears that the carbanion can decompose by either an ionic or a free-radical mechanism, depeneding on the nucleofugality of the leaving group.An intermediate predicted to be 4-nitrophenyl ketone ha been detected spestroscopically in a number of cases.
- Broxton Trevor, J.,Duddy, Neil W.
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p. 1186 - 1191
(2007/10/02)
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- Aryldiazonium Salts as Photo-affinity Labelling Reagents for Proteins
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Aryldiazonium tetrafluoroborates, substituted in the para-position by electron donating substituents, are potential photo-affinity labelling reagents for proteins and after light activation irreversibly inhibit acetylcholinesterase; using radiolabelled reagent, the inactivation is shown to be approximately stoicheiometric.
- Kieffer, Brigitte L.,Goeldner, Maurice Ph.,Hirth, Christian G.
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p. 398 - 399
(2007/10/02)
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