- A Short Synthesis of Dibenzofurans and Dibenzothiophenes
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An afficient synthesis of dibenzofurans and dibenzothiophenes from aryl salicylates is described, which involves a novel rearrangement-extrusion-cyclisation sequence of o-substituted phenoxyl and thiophenoxyl radicals.
- Black, Michael,Cadogan, J. I. G.,McNab, Hamish
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- Efficient synthesis of dibenzoxaborininols from diaryl ethers and their application to dibenzofuran synthesis
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A convenient and efficient method for the borylation of diaryl ethers leading to dibenzoxaborininols and the synthesis of dibenzofuran derivatives has been developed. The borylation involves the sequential three-step process: lithiation, borylation and hydrolysis. The synthesized dibenzoxaborininols could be readily transformed into dibenzofuran derivatives in good to excellent yields under palladium catalysis in the presence of iodine, and this is the first example for the formation of an aryl C-C bond from diarylborinic acids. Copyright
- Niu, Liting,Yang, Haijun,Jiang, Yuyang,Fu, Hua
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- Thermal hydrogenolysis of dibenzo-p-dioxin and dibenzofuran
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The behaviour of dibenzo-p-dioxin (DD) and dibenzofuran (DF) was studied in flow reactors in an excess of hydrogen, at atmospheric or elevated pressure (up to 35 bar), in the temperature range 890-1262 K. The experiments at atmospheric pressure were performed with DF or DD as such, while at increased pressures the compounds were introduced as an admixture with benzene. DD gave CO, but also DF as an important product. The rates clearly depended on the hydrogen concentration, and were about an order of magnitude higher than that of the hydrodechlorination of chlorobenzene. The reaction apparently started with the fission of a C-O bond, induced by H atom attack. DF reacted much more slowly, to give CO and hydrocarbons, especially naphthalene and benzene. Its rate was insensitive to the concentration of H2, and the degradation has been interpreted as thermolysis, through C-O bond homolysis, isomerisation and fragmentation, primarily to naphthalene, and C2O as the intermediate to CO. The apparent resistance of DF to hydrogenolysis can be understood from its relatively favourable thermodynamic stability. The consequences for the behaviour of polychlorinated DDs and DFs under similar conditions - relevant for the possible application of thermal hydrogenolysis as a waste management technology - are also discussed briefly. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Cieplik, Mariusz K.,Epema, Onno J.,Louw, Robert
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- Supercritical water oxidation of a PCB of 3-chlorobiphenyl using hydrogen peroxide
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The supercritical water oxidation (SCWO) of a PCB of 3-chlorobiphenyl (1) was carried out at a temperature of 673 K and a pressure of 30 MPa with a flow reactor. The initial concentrations of (1) and hydrogen peroxide ranged from 1.84 X 10 -3 to 8.74 X 10 -2 M (1 M=1 mol dm -3), and 0.181 to 2.67 M, respectively. The decomposition of (1) was higher than 99.9% so long as hydrogen peroxide was stoichiometrically added.
- Hatakeda, Kiyotaka,Ikushima, Yutaka,Ito, Shota,Saito, Norio,Sato, Osamu
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- A One-Pot Synthesis of Dibenzofurans from 6-Diazo-2-cyclohexenones
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A novel and efficient protocol for the rapid construction of dibenzofuran motifs from 6-diazo-2-cyclohexenone and ortho-haloiodobenzene has been developed. The process involves one-pot Pd-catalyzed cross-coupling/aromatization and Cu-catalyzed Ullmann coupling.
- Zhao, Hua,Yang, Ke,Zheng, Hongyan,Ding, Ruichao,Yin, Fangjie,Wang, Ning,Li, Yun,Cheng, Bin,Wang, Huifei,Zhai, Hongbin
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- Visible-Light-Promoted Synthesis of Dibenzofuran Derivatives
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Dibenzofurans are naturally occurring molecules that have received considerable attention for a variety of practical applications, such as in pharmaceuticals and electronic materials. Herein, an efficient and eco-friendly method for the synthesis of dibenzofuran derivatives via intramolecular C-O bond formation, which involves the in situ production of a diazonium salt, is described. The transformation requires a diazotizing agent and is promoted by the use of an organic photosensitizer under visible-light irradiation.
- Cho, Ji Young,Roh, Geum-Bee,Cho, Eun Jin
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- Prediction of polychlorinated dibenzofuran congener distribution from gas-phase phenol condensation pathways
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A model for predicting the distribution of dibenzofuran and polychlorinated dibenzofuran (PCDF) congeners from a distribution of phenols was developed. The model is based on a simplified chemical mechanism. Relative rate constants and reaction order with respect to phenol precursors were derived from experimental results using single phenols and equal molar mixtures of up to four phenols. For validation, experiments were performed at three temperatures using a distribution of phenol and 19 chlorinated phenols as measured in municipal waste incinerator exhaust gas. Comparison of experimental measurements and model predictions for PCDF isomer distributions and homologue pattern shows agreement within measurement uncertainty. The R-squared correlation coefficient exceeds 0.9 for all PCDF isomer distributions and the distribution of PCDF homologues. These results demonstrate that the distribution of dibenzofuran and the 135 PCDF congeners from gas-phase condensation of phenol and chlorinated phenols can be predicted from measurement of the distribution of phenol and the 19 chlorinated phenol congeners.
- Ryu, Jae-Yong,Mulholland, James A.,Oh, Jeong-Eun,Nakahata, Duane T.,Kim, Do-Hyong
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- Mechanisms of dioxin formation from the high-temperature oxidation of 2-bromophenol
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The homogeneous, gas-phase oxidative thermal degradation of 2-bromophenol was studied in a 1 cm i.d., fused silica flow reactor at a concentration of 88 ppm, reaction time of 2.0 s, over a temperature range from 300 to 1000 °C. Observed products in order of yield were dibenzo-p-dioxin (DD) > 4,6-dibromodibenzofuran (4,6-DBDF) > 4-monobromodibenzofuran (4-MCDF), dibenzofuran (DF), 1-monobromodibenzo-p-dioxin (1-MBDD), naphthalene, bromonaphthalene, 2,4-dibromophenol, 2,6-dibromophenol, phenol, bromobenzene, and benzene. This result is in contrast to the oxidation of 2-chlorophenol, where the major product is 4,6-dichlorodibenzofuran (4,6-DCDF). 4,6-DBDF was observed in high yields in contrast to our previous results for the pyrolysis of 2-bromophenol, where 4,6-DBDF was not detected. The increase in 4,6-DBDF yields is attributed to hydroxyl radical being the major chain carrier under oxidative conditions, which favors hydrogen-abstraction reactions that lead to formation of 4,6-DBDF. However, DD is still the highest yield product under oxidative conditions because of the relative ease of displacement of Br? in the ring-closure reaction.
- Evans, Catherine S.,Dellinger, Barry
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- Cubic nano-copper(I) oxides as reusable catalyst in consecutive decarboxylative C[sbnd]H arylation and carbonylation: rapid synthesis of carbonyl dibenzofurans
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Consecutive chemo- and regio-selective decarboxylative C[sbnd]H arylation, followed by carbonylative C[sbnd]C coupling of aryl halide with isocyanide/alcohol was applied for the first time in one-step synthesis of carbonyl dibenzofurans with nanodomain cuprous oxide under aerobic condition. As a proof of concept, several novel dibenzofurans were synthesized from 2-(3-iodophenoxy)benzoic acid in good yield. The tandem protocol eliminates the use of excess catalysts, hazardous organic solvents, heavy metals like palladium or rhodium, ligands, oxidants, or external additives. More importantly, the cubic Cu(I) nanocatalyst can be recovered and recycled for three consecutive reactions without any significant loss of catalytic activity or any change in its morphology. Use of water as solvent and reusable catalyst makes the reaction environment friendly.
- Pal, Rammyani,Chatterjee, Nivedita,Roy, Manas,Sarkar, Sabyasachi,Sarkar, Swarbhanu,Sen, Asish Kumar
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- The thermodynamic properties of dibenzofuran
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Measurements leading to the calculation of the ideal-gas thermodynamic properties for dibenzofuran are reported.Experimental methods included combustion calorimetry, adiabatic heat-capacity calorimetry, comparative, ebulliometry, inclined-piston manometry, and differential scanning calorimetry.Entropies, enthalpies, and Gibbs energies of formation were derived for the ideal gas for selected temperatures between 298.15 K and 720 K.The critical temperature and critical density were determined with a differential scanning calorimeter, and the critical pressure was derived.These are the first reported experimental critical properties for dibenzofuran.Measured combustion enthalpies, vapour pressures, critical properties, and ideal-gas entropies are compared with literature values.
- Chirico, R. D.,Gammon, B. E.,Knipmeyer, S. E.,Nguyen, A.,Strube, M. M.,et al.
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- Photoinduced Synthesis of Dibenzofurans: Intramolecular and Intermolecular Comparative Methodologies
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The SRN1 reaction has been used as a powerful tool for the synthesis of heterocycles, and only a few studies about photoinduced intramolecular cyclization to generate a new C-O bond by a radical pathway have been reported. This work introduces two strategies for the synthesis of substituted dibenzofurans by electron transfer (eT) reactions. The first one is a three-step process that comprises bromination of o-arylphenols, Suzuki-Miyaura cross-coupling and photoinduced cyclization in order to obtain the above-mentioned products. The second one is a metal-free procedure and does not require any photocatalyst. Different solvents were tested, and the yields ranged from low to moderate. A comparison was established between both methodologies, showing that the second one is the most suitable for the synthesis of dibenzofurans.
- Camargo Solórzano, Patricia,Brigante, Federico,Pierini, Adriana B.,Jimenez, Liliana B.
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- Synthesis of Dibenzofurans by Cu-Catalyzed Deborylative Ring Contraction of Dibenzoxaborins
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An efficient transformation of dibenzoxaborins to dibenzofurans by deborylative ring contraction was achieved under mild conditions using a copper catalyst. The method showed a broad substrate scope enabling the preparation of various dibenzofurans, including those bearing a functional group. The ready availability of various dibenzoxaborins enhances the utility of this method, as demonstrated by the regiodivergent synthesis of dibenzofurans.
- Sumida, Yuto,Harada, Ryu,Sumida, Tomoe,Johmoto, Kohei,Uekusa, Hidehiro,Hosoya, Takamitsu
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- The Pschorr Cyclization of Aromatic Amines with t-Butyl Thionitrate in Nonaqueous Media
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The Pschorr cyclization of various arylamines with t-butyl thionitrate under nonaqueous conditions gave the corresponding cyclic products in moderate yields.The same reaction was also found to proceed readily with p-toluenesulfonyl nitrite at room tempoerature.Treatment of o-aminophenyl allyl ether or sulfide with t-butyl thionitrate resulted in the intramolecular Meerwein arylation to the olefinic bond affording 3-chlorochroman or - thiochroman, through the yield was low.The plausible mechanism of the Pschorr cyclization with t-butyl thionitrate is discussed.
- Oae, Shigeru,Iida, Kazuyuki,Shinhama, Koichi,Takata, Toshikazu
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- A C-to-O atom-swapping reaction sequence enabled by Ni-catalyzed decarbonylation of lactones
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Advances in site-selective functionalization reactions have enabled single atom changes on the periphery of a complex molecule, but reaction manifolds that enable such changes on the core framework of the molecule remain sparse. Here, we disclose a strategy for carbon-to-oxygen substitution in cyclic diarylmethanes and diarylketones to yield cyclic diarylethers. Oxygen atom insertion is accomplished by methylene and Baeyer-Villiger oxidations. To remove the carbon atom in this C-to-O atom swap process, we developed a nickel-catalyzed decarbonylation of lactones to yield the corresponding cyclic diaryl ethers. This reaction was enabled by mechanistic studies with stoichiometric nickel(ii) complexes that led to the optimization of a ligand capable of promoting a challenging C(sp2)-O(aryl) reductive elimination. The nickel-catalyzed decarbonylation was applied to 6-8 membered lactones (16 examples, 32-99%). Finally, a C-to-O atom-swapping reaction sequence was accomplished on a natural product and a pharmaceutical precursor.
- Li, Junqi,Luu, Quang H.
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p. 1095 - 1100
(2022/02/02)
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- Palladium-catalyzed intramolecular aromatic C-H acylation of 2-arylbenzoyl fluorides
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The catalytic intramolecular cyclization of acyl fluorides using a Pd(OAc)2/PCy3 system is described. A wide range of 2-arylbenzoyl fluoride derivatives can be used as fluorenone precursors and the reaction proceeds via an intramolecular coupling between aromatic C-H bonds with acyl C-F bonds. The reaction can be applied to the synthesis of indenofluorenedione derivatives and to the construction of other molecules with fivemembered rings.
- Hayakawa, Kazuki,Ikai, Kana,Ogiwara, Yohei,Sakai, Norio,Sakurai, Yuka
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p. 1882 - 1893
(2021/08/13)
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- A facile and versatile electro-reductive system for hydrodefunctionalization under ambient conditions
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A general electrochemical system for reductive hydrodefunctionalization is described, employing the inexpensive and easily available triethylamine (Et3N) as a sacrificial reductant. This protocol is characterized by facile operation, sustainable conditions, and exceptionally wide substrate scope covering the cleavage of C-halogen, N-S, N-C, O-S, O-C, C-C and C-N bonds. Notably, the selectivity and capability of reduction can be conveniently switched by simple incorporation or removal of an alcohol as a co-solvent.
- Huang, Binbin,Guo, Lin,Xia, Wujiong
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supporting information
p. 2095 - 2103
(2021/03/26)
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- Nickel-Catalyzed Photodehalogenation of Aryl Bromides
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Herein, we describe a Ni-catalyzed photodehalogenation of aryl bromides under visible-light irradiation that utilizes tetrahydrofuran as hydrogen source. The protocol obviates the need for exogeneous amine reductants or photocatalysts and is characterized by its simplicity and broad scope, including challenging substrate combinations.
- Higginson, Bradley,Sanjosé-Orduna, Jesus,Gu, Yiting,Martin, Ruben
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supporting information
p. 1633 - 1636
(2021/04/23)
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- Quinoline Ligands Improve the Classic Direct C?H Functionalisation/Intramolecular Cyclisation of Diaryl Ethers to Dibenzofurans
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The C?H functionalisation approach to the synthesis of dibenzofurans is hampered by a number of problems. Herein we describe the evolution of a cheap, bench stable quinoline ligand, which obviates most of the current limitations and allows for a high yielding synthesis of a range of valuable dibenzofurans. Dibenzofurans are important motifs in natural products and compounds with wide biological activity.
- Mackey, Katrina,Jones, David J.,Pardo, Leticia M.,McGlacken, Gerard P.
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supporting information
p. 495 - 498
(2021/01/12)
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- Catalyst-Free Synthesis of O-Heteroacenes by Ladderization of Fluorinated Oligophenylenes
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A novel catalyst-free approach to benzoannulated oxygen-containing heterocycles from fluorinated oligophenylenes is reported. Unlike existing methods, the presented reaction does not require an oxygen-containing precursor and relies on an external oxygen source, potassium tert-butoxide, which serves as an O2? synthon. The radical nature of the reaction facilitates nucleophilic substitution even in the presence of strong electron-donating groups and enables de-tert-butylation required for the complete annulation. Also demonstrated is the applicability of the method to introduce five-, six-, and seven-membered rings containing oxygen, whereas multiple annulations also open up a short synthetic path to ladder-type O-heteroacenes and oligodibenzofurans.
- Feofanov, Mikhail,Akhmetov, Vladimir,Takayama, Ryo,Amsharov, Konstantin
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supporting information
p. 5199 - 5203
(2021/02/21)
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- Visible-Light-Induced, Base-Promoted Transition-Metal-Free Dehalogenation of Aryl Fluorides, Chlorides, Bromides, and Iodides
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We report a simple and efficient visible-light-induced transition-metal-free hydrogenation of aryl halides. The combined visible light and base system is used to initiate the desired radical-mediated hydrogenation. A variety of aryl fluorides, chlorides, bromides, and iodides could be reduced to the corresponding (hetero)arenes with excellent yields under mild conditions. Various functional groups and other heterocyclic compounds are tolerated.
- Ding, Ting-Hui,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 3084 - 3088
(2020/04/10)
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- Access to Dibenzofurans through Dimerization/Trimerization of Cyclohexanones Followed by Dehydroaromatization
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A novel and efficient method for the synthesis of unsymmetrical substituted dibenzofurans has been developed, which can selectively produce disubstituted dibenzofurans and trisubstituted dibenzofurans products under metal-free conditions. This approach starts from cheap and available nonaromatic cyclohexanones, affording a simple and efficient access to unsymmetrical substituted dibenzofurans.
- Jiang, Pingyu,Chen, Shanping,Xia, Yi,Zhang, Qingqing,Deng, Guo-Jun
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supporting information
p. 8076 - 8081
(2020/11/02)
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- Exploiting the radical reactivity of diazaphosphinanes in hydrodehalogenations and cascade cyclizations
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The remarkable reducibility of diazaphosphinanes has been extensively applied in various hydrogenations, based on and yet limited by their well-known hydridic reactivity. Here we exploited their unprecedented radical reactivity to implement hydrodehalogenations and cascade cyclizations originally inaccessible by hydride transfer. These reactions feature a broad substrate scope, high efficiency and simplicity of manipulation. Mechanistic studies suggested a radical chain process in which a phosphinyl radical is generated in a catalytic cycle via hydrogen-atom transfer from diazaphosphinanes. The radical reactivity of diazaphosphinanes disclosed here differs from their well-established hydridic reactivity, and hence, opens a new avenue for diazaphosphinane applications in organic syntheses.
- Cheng, Jin-Pei,Yang, Jin-Dong,Zhang, Jingjing
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p. 4786 - 4790
(2020/06/18)
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- Direct C-H α-Arylation of Enones with ArI(O2CR)2 Reagents
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α-Arylation of α,β-unsaturated ketones constitutes a powerful synthetic transformation. It is most commonly achieved via cross-coupling of α-haloenones, but this stepwise strategy requires prefunctionalized substrates and expensive catalysts. Direct enone C-H α-arylation would offer an atom- and step-economical alternative, but such reports are scarce. Herein we report the metal-free direct C-H arylation of enones mediated by hypervalent iodine reagents. The reaction proceeds via a reductive iodonium Claisen rearrangement of in situ-generated β-pyridinium silyl enol ethers. The aryl groups are derived from ArI(O2CCF3)2 reagents, which are readily accessed from the parent iodoarenes. The reaction is tolerant of a wide range of substitution patterns, and the incorporated arenes maintain the valuable iodine functional handle. Mechanistic investigations implicate arylation via an umpoled "enolonium" species and show that the presence of a β-pyridinium moiety is critical for the desired C-C bond formation.
- Sousa E Silva, Felipe Cesar,Van, Nguyen T.,Wengryniuk, Sarah E.
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- Alumina-promoted oxodefluorination
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A simple protocol for the clean preparation of heterocyclic compounds containing dibenzofuran's core via oxodefluorination of fluoroarenes on activated γ-Al2O3 is reported. Alumina can be considered as a reliable oxygen source enabling one-pot substitution of fluorine atoms and yielding benzoannulated furan derivatives. The corresponding C-F bond activation is selective towards less stable C-Br/C-I and occurs under metal- A nd solvent-free conditions.
- Amsharov, Konstantin,Mikhail, Feofanov,Vladimir, Akhmetov
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p. 10879 - 10882
(2020/03/27)
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- Practical Transition-Metal-Free Protodeboronation of Arylboronic Acids in Aqueous Sodium Hypochlorite
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A concise and practical method was developed for the protodeboronation of arylboronic acids under mild conditions in aqueous NaClO at 100 °C. The strategy is low-cost, transition-metal-free, and base-free.
- Li, Minxin,Tang, Yanling,Gao, Jinchun,Rao, Gaoxiong,Mao, Zewei
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p. 2039 - 2042
(2020/10/21)
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- Hydrodehalogenation of Aryl Halides through Direct Electrolysis
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A catalyst- and metal-free electrochemical hydrodehalogenation of aryl halides is disclosed. Our reaction by a flexible protocol is operated in an undivided cell equipped with an inexpensive graphite rod anode and cathode. Trialkylamines nBu3N/Et3N behave as effective reductants and hydrogen atom donors for this electrochemical reductive reaction. Various aryl and heteroaryl bromides worked effectively. The typically less reactive aryl chlorides and fluorides can also be smoothly converted. The utility of our method is demonstrated by detoxification of harmful pesticides and hydrodebromination of a dibrominated biphenyl (analogues of flame-retardants) in gram scale.
- Ke, Jie,Wang, Hongling,Zhou, Liejin,Mou, Chengli,Zhang, Jingjie,Pan, Lutai,Chi, Yonggui Robin
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supporting information
p. 6911 - 6914
(2019/05/10)
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- Copper-Catalyzed One-Pot Synthesis of Dibenzofurans, Xanthenes, and Xanthones from Cyclic Diphenyl Iodoniums
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Oxygenation of cyclic diphenyl iodoniums (CDPIs) with varied medium-ring sizes has been fully investigated. This practical copper-catalyzed tandem reaction of CDPIs with water as the oxygen source enables the construction of derivatised dibenzofurans and xanthenes at moderate to good yields. Moreover, structurally important xanthones are also successfully accessed under the oxygenation conditions with additional TEMPO.
- Zhu, Daqian,Li, Min,Wu, Zhouming,Du, Yongliang,Luo, Bingling,Huang, Peng,Wen, Shijun
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supporting information
p. 4566 - 4571
(2019/07/09)
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- Facile synthesis of inorganic–organic Fe2W18Fe4@NiO@CTS hybrid nanocatalyst induced efficient performance in oxidative desulfurization of real fuel
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In this work, a new nanocatalyst, Fe2W18Fe4@NiO@CTS, was synthesized by the reaction of sandwich-type polyoxometalate (Fe2W18Fe4), nickel oxide (NiO), and chitosan (CTS) via sol–gel method. The assembled nanocatalyst was systematically characterized by FT-IR, UV–vis, XRD, SEM, and EDX analysis. The catalytic activity of Fe2W18Fe4@NiO@CTS was tested on oxidative desulfurization (ODS) of real gasoline and model fuels. The experimental results revealed that the levels of sulfur content and mercaptan compounds of gasoline were lowered with 97% efficiency. Also, the Fe2W18Fe4@NiO@CTS nanocatalyst demonstrated an outstanding catalytic performance for the oxidation of dibenzothiophene (DBT) in the model fuel. The major factors that influence the desulfurization efficiency and the kinetic study of the ODS reactions were fully detailed and discussed. The probable ODS pathway was proposed via the electrophilic mechanism on the basis of the electrophilic characteristic of the metal-oxo-peroxo intermediates. The prepared nanocatalyst could be reused for 5 successive runs without any appreciable loss in its catalytic activity. As a result, the current study suggested the potential application of the Fe2W18Fe4@NiO@CTS hybrid nanocatalyst as an ideal candidate for removal of sulfur compounds from fuel.
- Rezvani, Mohammad Ali,Maleki, Zeynab
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- Pd-Catalyzed Denitrative Intramolecular C-H Arylation
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A Pd-catalyzed intramolecular C-H arylation of nitroarenes has been developed. Nitroarenes bearing tethered aryl groups at the ortho-position can be readily prepared in one step from 2-halonitroarenes by a nucleophilic aromatic substitution (SNAr). Under Pd/BrettPhos catalysis, activations of the C-NO2 bond as well as the C-H bond on arenes generated the corresponding biaryl linkage in moderate to excellent yields.
- Asahara, Kitty K.,Okita, Toshimasa,Saito, Ami N.,Muto, Kei,Nakao, Yoshiaki,Yamaguchi, Junichiro
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supporting information
p. 4721 - 4724
(2019/06/17)
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- Efficient photocaging of a tight-binding bisubstrate inhibitor of cAMP-dependent protein kinase
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Photocaging of a tight-binding bisubstrate inhibitor of cAMP-dependent protein kinase (PKA) with a nitrodibenzofuran-based group fully abolished its inhibitory potency. The affinity difference between the photocaged and the active inhibitor was over 5 orders of magnitude. The photocaged inhibitor disrupted the PKA holoenzyme in cell lysates upon photolysis under a 398 nm LED.
- S?rmus, Tanel,Lavogina, Darja,Enkvist, Erki,Uri, Asko,Viht, Kaido
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supporting information
p. 11147 - 11150
(2019/09/20)
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- Ni-Catalyzed Reductive Cyanation of Aryl Halides and Phenol Derivatives via Transnitrilation
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Herein, we report a Ni-catalyzed reductive coupling for the synthesis of benzonitriles from aryl (pseudo)halides and an electrophilic cyanating reagent, 2-methyl-2-phenyl malononitrile (MPMN). MPMN is a bench-stable, carbon-bound electrophilic CN reagent that does not release cyanide under the reaction conditions. A variety of medicinally relevant benzonitriles can be made in good yields. Addition of NaBr to the reaction mixture allows for the use of more challenging aryl electrophiles such as aryl chlorides, tosylates, and triflates. Mechanistic investigations suggest that NaBr plays a role in facilitating oxidative addition with these substrates.
- Mills, L. Reginald,Graham, Joshua M.,Patel, Purvish,Rousseaux, Sophie A. L.
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supporting information
p. 19257 - 19262
(2019/12/02)
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- Thiolate-Initiated Synthesis of Dibenzothiophenes from 2,2′-Bis(methylthio)-1,1′-Biaryl Derivatives through Cleavage of Two Carbon-Sulfur Bonds
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A catalytic reaction involving the cleavage of two carbon-sulfur bonds in 2,2′-bis(methylthio)-1,1′-biaryl derivatives is reported. This reaction does not require a transition-metal catalyst and is promoted by a thiolate anion. Notably, based on DFT calculations, the product-forming cyclization step is shown to proceed through a concerted nucleophilic aromatic substitution (CS N Ar) mechanism.
- Chatani, Naoto,Kawashima, Yuki,Kodama, Takuya,Masuya, Yoshihiro,Tobisu, Mamoru
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supporting information
p. 1995 - 1999
(2019/10/22)
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- Intramolecular Aryl Migration of Diaryliodonium Salts: Access to ortho-Iodo Diaryl Ethers
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By using vicinal trifluoromethanesulfonate-substituted diaryliodonium salts, a novel approach was developed for the synthesis of ortho-iodo diaryl ethers by intramolecular aryl migration. The reaction conditions are mild with a broad substrate scope. Mechanistic insight suggests a sulfonyl-directed nucleophilic aromatic substitution pathway. Additionally, the product ortho-iodo diaryl ethers serve as versatile synthons as demonstrated with several coupling reactions. Furthermore, a useful thyroxine analogue of the 3-iodo-l-thyronine (3-T1) derivative was synthesized by this aryl migration procedure.
- Chen, Huangguan,Han, Jianwei,Wang, Limin
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supporting information
p. 12313 - 12317
(2018/09/10)
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- Synthesis process of dibenzofuran derivatives
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The invention relates to a synthesis process of dibenzofuran derivatives, and relates to the fields of natural products with biological activity, medicaments and material chemistry. The used raw material is a cyclic diphenyliodonium trifluoromethanesulfonate derivative, a reaction is carried out in a water phase at 100 DEG C under the catalysis of a 1,10-phenanthroline ligand and cuprous iodide, and a series of dibenzofuran derivatives are obtained. With the adoption of the method provided by the invention, the dibenzofuran derivatives can be obtained by carrying out the reaction at the temperature of 100 DEG C for 24 hours, and the yield is 60-96%. In the reaction, water is taken as a reagent as well as a solvent for participating in the reaction, and the simple, convenient, green, economic, and novel method is provided for synthesizing the derivatives.
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Paragraph 0018; 0019
(2018/09/26)
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- Selective Hydrogenolysis of Dibenzofuran over Highly Efficient Pt/MgO Catalysts to o-Phenylphenol
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Direct selective hydrogenolysis of dibenzofuran (DBF) derived from coal and shale oil to a value-added chemical, ortho-phenylphenol (OPP), with high selectivity (80%) and yield (48%) has been achieved over Pt/MgO at 400 °C and 1.0 MPa by controlling the C-O bond cleavage as well as minimizing the extent of hydrogenation of aromatic rings. Meanwhile, Pt/SiO2, Pt/Al2O3, and Pt/MgO/Al2O3 catalysts were used for the DBF hydrogenolysis and showed lower selectivity for OPP. The influence of reaction parameters has been studied to unveil the optimal reaction conditions. And the phenomenon of OPP dehydrogenation is found over various catalysts for the hydrogenation reaction of OPP. Extensive reactions and catalyst characterizations demonstrated that the OPP selectivity and the dehydrogenation of OPP to DBF follows the order of supports basicity: MgO-900 > MgO > SiO2 > MgO/Al2O3 > Al2O3, which shows that the acid-base properties of supports impact the adsorption and desorption behaviors of DBF and OPP, and results in the disparity of OPP selectivity and the dehydrogenation of OPP. Finally, a plausible reaction pathway and mechanistic understanding are proposed.
- Zhang, Jie,Wang, Lei,Li, Chuang,Jin, Shaohua,Liang, Changhai
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- Electron transfer-induced reduction of organic halides with amines
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Reduction of a variety of organo halides was examined by using amines as a sacrificial hydrogen source. UV light-induced reduction of vinyl and aryl halides with triethylamine proceeded smoothly to give the corresponding reduced products. High temperature heating also caused the reduction and DABCO (1,4-diazabicyclo[2.2.2]octane) also served as a good reducing reagent.
- Fukuyama, Takahide,Fujita, Yuki,Miyoshi, Hayato,Ryu, Ilhyong,Kao, Shih-Chieh,Wu, Yen-Ku
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supporting information
p. 5582 - 5585
(2018/06/04)
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- Microwave-Promoted Pd-Catalyzed Synthesis of Dibenzofurans from Ortho-Arylphenols
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ortho-Aryl phenols, synthesized via protecting group free Suzuki–Miyaura coupling of ortho-halophenols and arene boronic acids, undergo a cyclization to dibenzofurans via oxidative C–H activation. The reaction proceeds under microwave irradiation in short reaction times using catalytic amounts of Pd(OAc)2 without additional ligands.
- Schmidt, Bernd,Riemer, Martin
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p. 1287 - 1297
(2017/03/27)
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- Synthesis of 6H-Benzo[c]chromenes via Palladium-Catalyzed Intramolecular Dehydrogenative Coupling of Two Aryl C-H Bonds
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The palladium-catalyzed intramolecular C-H/C-H coupling reaction of two simple arenes to generate 6H-benzo[c]chromenes has been reported for the first time. The approach features broad substrate scope and good tolerance of functional groups and uses molecular oxygen as the terminal oxidant. The high efficiency of the approach is verified by concise total synthesis of natural product cannabinol.
- Guo, Dong-Dong,Li, Bin,Wang, Da-Yu,Gao, Ya-Ru,Guo, Shi-Huan,Pan, Gao-Fei,Wang, Yong-Qiang
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supporting information
p. 798 - 801
(2017/03/01)
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- Radical Hydrodehalogenation of Aryl Bromides and Chlorides with Sodium Hydride and 1,4-Dioxane
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A practical method for radical chain reduction of various aryl bromides and chlorides is introduced. The thermal process uses NaH and 1,4-dioxane as reagents and 1,10-phenanthroline as an initiator. Hydrodehalogenation can be combined with typical cyclization reactions, proving the nature of the radical mechanism. These chain reactions proceed by electron catalysis. DFT calculations and mechanistic studies support the suggested mechanism.
- Hokamp, Tobias,Dewanji, Abhishek,Lübbesmeyer, Maximilian,Mück-Lichtenfeld, Christian,Würthwein, Ernst-Ulrich,Studer, Armido
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supporting information
p. 13275 - 13278
(2017/10/09)
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- Effect of the nature of sulfur compounds on their reactivity in the oxidative desulfurization of hydrocarbon fuels with oxygen over a modified CuZnAlO catalyst
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The reactivity of thiophene, dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), which are the representatives of the main classes of sulfur compounds that are the constituents of diesel fractions, was studied in the course of their oxidative desulfurization with oxygen on a CuO/ZnO/Al2O3 catalyst modified with boron and molybdenum additives. At T ≥ 375°C, the reactivity increased in the order thiophene 2 from hydrocarbon fuel, which was simulated by a solution of 4,6-DMDBT in toluene, was 80%. Under the assumption of a first order reaction with respect to sulfur compound and oxygen, the apparent activation energies of the test processes were calculated. An attempt was made to reveal the role of the adsorption of sulfur compounds in the overall process of oxidative desulfurization with the use of X-ray diffraction analysis, X-ray photoelectron spectroscopy, and differential thermal and thermogravimetric analysis with the massspectrometric monitoring of gas phase composition.
- Yashnik,Salnikov,Kerzhentsev,Saraev,Kaichev,Khitsova,Ismagilov,Yamin,Koseoglu
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- Au-catalyzed biaryl coupling to generate 5- to 9-membered rings: Turnover-limiting reductive elimination versus π-complexation
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The intramolecular gold-catalyzed arylation of arenes by aryl-trimethylsilanes has been investigated from both mechanistic and preparative aspects. The reaction generates 5- to 9-membered rings, and of the 44 examples studied, 10 include a heteroatom (N, O). Tethering of the arene to the arylsilane provides not only a tool to probe the impact of the conformational flexibility of Ar-Au-Ar intermediates, via systematic modulation of the length of aryl-aryl linkage, but also the ability to arylate neutral and electron-poor arenes-substrates that do not react at all in the intermolecular process. Rendering the arylation intramolecular also results in phenomenologically simpler reaction kinetics, and overall these features have facilitated a detailed study of linear free energy relationships, kinetic isotope effects, and the first quantitative experimental data on the effects of aryl electron demand and conformational freedom on the rate of reductive elimination from diaryl-gold(III) species. The turnover-limiting step for the formation of a series of fluorene derivatives is sensitive to the reactivity of the arene and changes from reductive elimination to π-complexation for arenes bearing strongly electron-withdrawing substituents (σ > 0.43). Reductive elimination is accelerated by electron-donating substituents (ρ = -2.0) on one or both rings, with the individual σ-values being additive in nature. Longer and more flexible tethers between the two aryl rings result in faster reductive elimination from Ar-Au(X)-Ar and lead to the π-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step.
- Corrie, Tom J. A.,Ball, Liam T.,Russell, Christopher A.,Lloyd-Jones, Guy C.
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p. 245 - 254
(2017/05/29)
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- Au-Catalyzed Biaryl Coupling to Generate 5- To 9-Membered Rings: Turnover-Limiting Reductive Elimination versus ?-Complexation
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The intramolecular gold-catalyzed arylation of arenes by aryl-trimethylsilanes has been investigated from both mechanistic and preparative aspects. The reaction generates 5- to 9-membered rings, and of the 44 examples studied, 10 include a heteroatom (N, O). Tethering of the arene to the arylsilane provides not only a tool to probe the impact of the conformational flexibility of Ar-Au-Ar intermediates, via systematic modulation of the length of aryl-aryl linkage, but also the ability to arylate neutral and electron-poor arenes - substrates that do not react at all in the intermolecular process. Rendering the arylation intramolecular also results in phenomenologically simpler reaction kinetics, and overall these features have facilitated a detailed study of linear free energy relationships, kinetic isotope effects, and the first quantitative experimental data on the effects of aryl electron demand and conformational freedom on the rate of reductive elimination from diaryl-gold(III) species. The turnover-limiting step for the formation of a series of fluorene derivatives is sensitive to the reactivity of the arene and changes from reductive elimination to ?-complexation for arenes bearing strongly electron-withdrawing substituents (σ > 0.43). Reductive elimination is accelerated by electron-donating substituents (ρ = -2.0) on one or both rings, with the individual σ-values being additive in nature. Longer and more flexible tethers between the two aryl rings result in faster reductive elimination from Ar-Au(X)-Ar and lead to the ?-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step.
- Ball, Liam T.,Corrie, Tom J. A.,Lloyd-Jones, Guy C.,Russell, Christopher A.
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p. 245 - 254
(2021/09/04)
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- Hydrodeoxygenation of Phenol over Zirconia-Supported Catalysts: The Effect of Metal Type on Reaction Mechanism and Catalyst Deactivation
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This work aims at investigating the effect of the type of metal (Pt, Pd, Rh, Ru, Cu, Ni, Co) on the performance of ZrO2-supported catalysts for the hydrodeoxygenation of phenol in the gas phase at 573 K and 1 atm. Two different reaction pathways take place depending on the type of the metal. For Pt/ZrO2 and Pd/ZrO2 catalysts, phenol is mainly tautomerized, followed by hydrogenation of the C=C bond of the tautomer intermediate formed, producing cyclohexanone and cyclohexanol. By contrast, the direct dehydroxylation of phenol followed by hydrogenolysis might also occur over more oxophilic metals such as Rh, Ru, Co, and Ni. In addition to the metals, the oxophilic sites of this support represented by Zr4+ and Zr3+ cations near the perimeter of the metal particles also increased the selectivity to deoxygenated products. All catalysts were significantly deactivated mainly owing to the growth of metal particle size and the decrease in the density of oxophilic sites.
- Teles, Camila A.,Rabelo-Neto, Raimundo C.,Jacobs, Gary,Davis, Burtron H.,Resasco, Daniel E.,Noronha, Fábio B.
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p. 2850 - 2863
(2017/07/28)
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- CATALYSTS AND METHODS FOR ALCOHOL DEHYDRATION
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Provided is a method for preparing a diaryl ether compound through the dehydration of an aromatic alcohol compound in the presence of a halogenated rare earth element oxide catalyst, wherein the used dehydration catalyst may be regenerated by a halogenation step. The rare earth element oxide is an oxide of a light rare earth element, an oxide of a medium rare earth element, an oxide of a heavy rare earth element, an oxide of yttrium, or a mixtures of two or more thereof.
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Paragraph 0060; 0061
(2016/05/02)
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- Catalysts and methods for alcohol dehydration
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Provided is a process for preparing a diaryl ether compound through the dehydration of an aromatic alcohol compound in the presence of a dehydration catalyst. The dehydration catalyst is an oxide of a medium rare earth element, wherein the medium rare earth element is samarium, europium, gadolinium, or mixtures thereof.
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Page/Page column 12; 13
(2016/10/17)
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- Cu/Mg/Al/Zr non-noble metal catalysts for o-phenylphenol synthesis
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Cu/Mg/Al/Zr hydrotalcite-like precursors with Zr4+:(Al3+ + Zr4+) atomic ratios between 0 and 1 were prepared by co-precipitation methods. The precursors were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric (TG) analysis and Fourier transform infrared spectroscopy (FT-IR). The results confirmed that well-defined layered double hydroxides (LDH) can be synthesized when the added Zr content is less than 0.25 in terms of Zr4+/(Al3+ + Zr4+) atomic ratio. The catalysts of Cu/Zn/Al/Zr mixed oxides can be obtained via thermal decomposition of hydroxide precursors, and can be used in dehydrogenation of 2-(1-cyclohexenyl) cyclohexanone (CHCH) to ortho-phenylphenol (OPP). Copper particles inside the catalyst act as active sites for dehydrogenation. Transmission electron microscopy (TEM), XRD, N2O chemisorption and N2 adsorption-desorption were performed to investigate the effect of Zr content on determining the copper particle size. Based on the catalytic performance test, it was concluded that the conversion of CHCH depends on the copper particle size of these catalysts.
- Zeng, Yongping,Zhang, Tianchi,Xu, Yueyang,Hu, Peili,Ye, Ting,Jia, Zhehua,Ju, Shengui
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p. 6737 - 6746
(2016/02/03)
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- SILYLATION OF AROMATIC HETEROCYCLES BY EARTH ABUNDANT TRANSITION-METAL-FREE CATALYSTS
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The present invention describes chemical systems and methods for silylating aromatic organic substrates, said system or method comprising or consisting essentially of a mixture of (a) at least one organosilane and (b) at least one strong base, the definition of strong base now also including hydroxide, especially KOH, said system being preferably, but not necessarily substantially free of a transition-metal compound, and said methods comprising contacting a quantity of the organic substrate with a mixture of (a) at least one organosilane and (b) at least one strong base, under conditions sufficient to silylate the aromatic substrate; wherein said system is substantially free of a transition-metal compound.
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Paragraph 0190; 0191
(2016/04/26)
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- Preparation of Substituted Phenanthridines from the Coupling of Aryldiazonium Salts with Nitriles: A Metal Free Approach
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A transition metal free approach for the synthesis of substituted phenanthridines from the coupling reaction of aryldiazonium tetrafluoroborates with nitriles has been developed. This operationally simple protocol proceeds through a substitution of aryldiazonium with nitriles followed by an intramolecular arylation to provide the corresponding phenanthridines in moderate to excellent yields. (Chemical Equation Presented).
- Ramanathan, Mani,Liu, Shiuh-Tzung
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p. 5329 - 5336
(2015/05/27)
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- Synthesis of Dibenzofurans via C-H Activation of o-Iodo Diaryl Ethers
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An efficient method for the synthesis of dibenzofuran from o-iododiaryl ether using reusable Pd/C under ligand-free conditions has been developed. Synthesis of o-iododiaryl ether was achieved in one pot through sequential iodination and O-arylation of phenol under mild reaction conditions.
- Panda, Niranjan,Mattan, Irshad,Nayak, Dinesh Kumar
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p. 6590 - 6597
(2015/10/06)
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- KOtBu mediated efficient approach for the synthesis of fused heterocycles via intramolecular O-/N-arylations
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A novel and efficient methodology for the synthesis of 6H-benzo[c]chromenes, 6H-benzo[c]chromen-6-ones, carbazoles, dibenzofurans, dibenzooxepins has been developed. The reaction goes through intramolecular O-/N-arylations with sp2C-Br bonds via typical SNAr pathway in presence of potassium-tert-butoxide base.
- Singha, Raju,Ahmed, Atiur,Nuree, Yasin,Ghosh, Munmun,Ray, Jayanta K.
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p. 50174 - 50177
(2015/06/25)
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- Palladium-catalyzed intra-and intermolecular C-H arylation using mesylates: Synthetic scope and mechanistic studies
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This paper describes the development of Pd-catalyzed inter-and intramolecular direct arylation using mesylates. Furthermore, a sequential mesylation/arylation protocol using phenols as substrates is described. These transformations are general with respect to the electronics of the C-H substrates and allow for the synthesis of diverse heterocyclic motifs in good yields. Both arenes and heteroarenes efficiently participate in these reactions. Preliminary mechanistic studies are presented for both inter-and intramolecular arylations.
- Ferguson, Devin M.,Rudolph, Stacey R.,Kalyani, Dipannita
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p. 2395 - 2401
(2014/07/21)
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- Lewis acid/Broensted acid mediated benz-annulation of thiophenes and electron-rich arenes
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A facile preparation of benz-annulated heterocycles were achieved at rt involving a Lewis acid/Broensted acid mediated annulation of heterocycles using 2,5-dimethoxytetrahydrofuran as a four-carbon synthon. The benz-/naphth-annulation was found to be successful with electron-rich arenes as well.
- Rafiq, Settu Muhamad,Sivasakthikumaran, Ramakrishnan,Mohanakrishnan, Arasambattu K.
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supporting information
p. 2720 - 2723
(2014/06/09)
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- Aerobic one-step oxidation of benzene to phenol on copper exchanged HZSM5 zeolites: A mechanistic study
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Various Cu/HZSM5-zeolites were prepared and their catalytic properties were investigated by product analysis via GC/MS chromatography in order to trace down the mechanism of the gas phase one-step oxidation of benzene to phenol with molecular oxygen. Comparison of Cu free and Cu containing zeolites showed that the activation of O2 takes place at copper centers of the zeolite and high copper loadings lead to high yields of deep oxidation products (CO, CO2). No phenol was formed in the absence of Br?nsted acid sites, i.e. on Cu/KZSM5, revealing the bifunctionality of the Cu/HZSM5 zeolite. The yields of the various oxidation products and thus the selectivity toward phenol can be influenced by variation of the relative O2 concentration in the reaction mixture, indicating the possibility of a stoichiometric use of O2. The role of the superoxide radical ion O2- as a reactive intermediate is discussed and a radical ionic reaction mechanism is suggested.
- Tabler, Andreas,H?usser, Anette,Roduner, Emil
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p. 139 - 145
(2013/09/23)
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- CATALYTIC DEHYDRATION OF ARYL ALCOHOLS TO DIARYL ETHERS
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Provided is a process for preparing a diaryl ether compound through the dehydration of an aromatic alcohol compound in the presence of a dehydration catalyst. The dehydration catalyst is an oxide of a light rare earth element, wherein the light earth element is lanthanum, praseodymium, neodymium, or mixtures thereof.
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Page/Page column 8; 12; 13
(2014/01/07)
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- CATALYTIC DEHYDRATION OF ARYL ALCOHOLS TO DIARYL ETHERS
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Provided is a process for preparing a diaryl ether compound through the dehydration of an aromatic alcohol compound in the presence of a dehydration catalyst. The dehydration catalyst is an oxide of a heavy rare earth element, wherein the heavy rare earth element is terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, or mixtures thereof.
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Page/Page column 15; 16
(2014/01/07)
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- Nickel-catalyzed hydrogenolysis of unactivated carbon-cyano bonds
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Selective hydrogenolysis of C-CN bonds can allow chemists to take advantage of ortho-directing ability, α-C-H acidity and electron withdrawing ability of the cyano group for synthetic manipulations. We have discovered hydrogenolysis of aryl and aliphatic cyanides under just 1 bar of hydrogen by using a nickel catalyst. This protocol was applied in the aryl cyanide directed functionalization reaction and α-substitution of benzyl cyanides.
- Patra, Tuhin,Agasti, Soumitra,Modak, Atanu,Maiti, Debabrata
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supporting information
p. 8362 - 8364
(2013/09/23)
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- Nickel-catalyzed intramolecular C-H arylation using aryl pivalates as electrophiles
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This paper describes a method for nickel catalyzed intramolecular C-H arylation using aryl pivalates as electrophiles. The transformation is efficient for the synthesis of diverse electronically and sterically differentiated dibenzofurans. Additionally, the method could be expanded toward the synthesis of carbazoles. Preliminary mechanistic studies of the transformation are also described.
- Wang, Jiayi,Ferguson, Devin M.,Kalyani, Dipannita
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p. 5780 - 5790
(2013/07/19)
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