- A Convenient and Stable Heterogeneous Nickel Catalyst for Hydrodehalogenation of Aryl Halides Using Molecular Hydrogen
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Hydrodehalogenation is an effective strategy for transforming persistent and potentially toxic organohalides into their more benign congeners. Common methods utilize Pd/C or Raney-nickel as catalysts, which are either expensive or have safety concerns. In this study, a nickel-based catalyst supported on titania (Ni-phen@TiO2-800) is used as a safe alternative to pyrophoric Raney-nickel. The catalyst is prepared in a straightforward fashion by deposition of nickel(II)/1,10-phenanthroline on titania, followed by pyrolysis. The catalytic material, which was characterized by SEM, TEM, XRD, and XPS, consists of nickel nanoparticles covered with N-doped carbon layers. By using design of experiments (DoE), this nanostructured catalyst is found to be proficient for the facile and selective hydrodehalogenation of a diverse range of substrates bearing C?I, C?Br, or C?Cl bonds (>30 examples). The practicality of this catalyst system is demonstrated by the dehalogenation of environmentally hazardous and polyhalogenated substrates atrazine, tetrabromobisphenol A, tetrachlorobenzene, and a polybrominated diphenyl ether (PBDE).
- Leonard, David K.,Ryabchuk, Pavel,Anwar, Muhammad,Dastgir, Sarim,Junge, Kathrin,Beller, Matthias
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- Metal-Free Heterogeneous Semiconductor for Visible-Light Photocatalytic Decarboxylation of Carboxylic Acids
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A suitable protocol for the photocatalytic decarboxylation of carboxylic acids was developed with metal-free ceramic boron carbon nitrides (BCN). With visible light irradiation, BCN oxidize carboxylic acids to give carbon-centered radicals, which were trapped by hydrogen atom donors or employed in the construction of the carbon-carbon bond. In this system, both (hetero)aromatic and aliphatic acids proceed the decarboxylation smoothly, and C-H, C-D, and C-C bonds are formed in moderate to high yields (35 examples, yield up to 93%). Control experiments support a radical process, and isotopic experiments show that methanol is employed as the hydrogen atom donor. Recycle tests and gram-scale reaction elucidate the practicability of the heterogeneous ceramic BCN photoredox system. It provides an alternative to homogeneous catalysts in the valuable carbon radical intermediates formation. Moreover, the metal-free system is also applicable to late-stage functionalization of anti-inflammatory drugs, such as naproxen and ibuprofen, which enrich the chemical toolbox.
- Shi, Jiale,Yuan, Tao,Zheng, Meifang,Wang, Xinchen
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p. 3040 - 3047
(2021/03/09)
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- Enantioselective hydroarylation or hydroalkenylation of benzo[b]thiophene 1,1-dioxides with organoboranes
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An efficient protocol for the asymmetric hydroarylation and hydroalkenylation of benzo[b]thiophene 1,1-dioxides with organoboranes has been developed. The combination of a rhodium(I) precatalyst and a chiral diene ligand constitutes the catalytic system, which enables the facile synthesis of 2,3-dihydrobenzo[b]thiophene 1,1-dioxides in good yields with high enantioselectivities. The merging of this asymmetric hydroarylation with the downstream alkylations delivers 2,3-dihydrobenzo[b]thiophene 1,1-dioxides that contain two continuous quaternary stereocenters with high enantioselectivities in a diastereodivergent manner.
- Hu, Fangdong,Jia, Jie,Li, Ximing,Xia, Ying
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supporting information
p. 896 - 901
(2021/02/01)
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- Site-Selective Silver-Catalyzed C-H Bond Deuteration of Five-Membered Aromatic Heterocycles and Pharmaceuticals
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Catalytic methods for the direct introduction of hydrogen isotopes into organic molecules are essential to the development of improved pharmaceuticals and to the alteration of their absorption, distribution, metabolism, and excretion (ADME) properties. However, the development of homogeneous catalysts for selective incorporation of isotopes in the absence of directing groups under practical conditions remains a long-standing challenge. Here, we show that a phosphine-ligated, silver-carbonate complex catalyzes the site-selective deuteration of C-H bonds in five-membered aromatic heterocycles and active pharmaceutical ingredients that have been resistant to catalytic H/D exchange. The reactions occur with CH3OD as a low-cost source of the isotope. The silver catalysts react with five-membered heteroarenes lacking directing groups, tolerate a wide range of functional groups, and react in both polar and nonpolar solvents. Mechanistic experiments, including deuterium kinetic isotope effects, determination of kinetic orders, and identification of the catalyst resting state, support C-H bond cleavage from a phosphine-ligated, silver-carbonate intermediate as the rate-determining step of the catalytic cycle.
- Tlahuext-Aca, Adrian,Hartwig, John F.
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p. 1119 - 1127
(2021/02/01)
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- Ceramic boron carbonitrides for unlocking organic halides with visible light
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Photochemistry provides a sustainable pathway for organic transformations by inducing radical intermediates from substrates through electron transfer process. However, progress is limited by heterogeneous photocatalysts that are required to be efficient, stable, and inexpensive for long-term operation with easy recyclability and product separation. Here, we report that boron carbonitride (BCN) ceramics are such a system and can reduce organic halides, including (het)aryl and alkyl halides, with visible light irradiation. Cross-coupling of halides to afford new C-H, C-C, and C-S bonds can proceed at ambient reaction conditions. Hydrogen, (het)aryl, and sulfonyl groups were introduced into the arenes and heteroarenes at the designed positions by means of mesolytic C-X (carbon-halogen) bond cleavage in the absence of any metal-based catalysts or ligands. BCN can be used not only for half reactions, like reduction reactions with a sacrificial agent, but also redox reactions through oxidative and reductive interfacial electron transfer. The BCN photocatalyst shows tolerance to different substituents and conserved activity after five recycles. The apparent metal-free system opens new opportunities for a wide range of organic catalysts using light energy and sustainable materials, which are metal-free, inexpensive and stable. This journal is
- Yuan, Tao,Zheng, Meifang,Antonietti, Markus,Wang, Xinchen
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p. 6323 - 6332
(2021/05/19)
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- New synthesis method of benzothiacyclopentadiene
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The invention discloses a novel synthesis method of benzothiacyclopentadiene, and belongs to the technical field of synthesis. The method comprises the following steps that: under an alkaline condition, chloroacetaldehyde and thiophenol undergo a Williamson condensation reaction to obtain thiophenyl acetaldehyde, the thiophenyl acetaldehyde undergoes a cyclization and dehydration reaction with a dehydrating agent under an acidic condition, water is added, layering is performed, an organic layer is taken, and reduced pressure distillation is performed to obtain the target product benzothiacyclopentadiene. The method has the advantages of simple operation, mild reaction, easy realization of industrialization, and high product yield.
- -
-
Paragraph 0034; 0037-0038; 0041; 0050; 0053
(2020/07/28)
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- Aryl-Nickel-Catalyzed Benzylic Dehydrogenation of Electron-Deficient Heteroarenes
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This manuscript describes the first practical benzylic dehydrogenation of electron-deficient heteroarenes, including pyridines, pyrazines, pyrimidines, pyridazines, and triazines. This transformation allows for the efficient benzylic oxidation of heteroarenes to afford heterocyclic styrenes by the action of nickel catalysis paired with an unconventional bromothiophene oxidant.
- Zhang, Pengpeng,Huang, David,Newhouse, Timothy R.
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supporting information
p. 1757 - 1762
(2020/02/04)
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- Nickel-catalyzed and Li-mediated regiospecific C-H arylation of benzothiophenes
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A nickel-based catalytic system for the regiospecific C2-H arylation of benzothiophene has been established. NiCl2(bpy) is used as a catalyst in combination with LiHMDS as a base in dioxane. The catalytic system is applicable to a variety of functionalized benzothiophenes, as well as other heteroarenes including thiophene, benzodithiophene, benzofuran and selenophene in combination with iodo aryl electrophiles. The role of LiHMDS as a uniquely potent base and a postulated mechanism are discussed. The applicability of this system is finally demonstrated for the synthesis of an intermediate of an active pharmaceutical ingredient.
- Canivet, Jér?me,Grousset, Léonie,Hisler, Ga?lle,Mohr, Yorck,Quadrelli, Elsje Alessandra,Roux, Yoann,Wisser, Florian M.
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supporting information
p. 3155 - 3161
(2020/06/19)
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- Metal-free and base-free decarboxylation of substituted cinnamic acids in a deep eutectic solvent
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A metal-free and base-free strategy was developed in DES to synthesize styrenes for the first time by decarboxylation of cinnamic acid derivatives, which provided a renewable and cost efficiently protocol to access various styrenes including those with functional groups such as 4-vinylphenol and 1-chloro-4-vinylbenzene.
- Chen, Chen,Jian, Yuqing,Lei, Yuxin,Li, Bin,Peng, Caiyun,Sheng, Wen-Bing,Sumera, Yasmin,Wang, Wei,Zhang, Ming
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p. 558 - 563
(2020/01/24)
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- Dioxazolones as masked ester surrogates in the Pd(ii)-catalyzed direct C-H arylation of 6,5-fused heterocycles
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A simple and effective Pd(ii)-catalyzed regioselective C(2)-H arylation of 6,5-fused heterocycles with dioxazolones as a masked ester surrogate under mild conditions is reported. The significance of the arylation is highlighted by the new reactivity demonstrated in dioxazolones via proximal C-H activation of the cyclic carbonate of the hydroxamic acid functionality under protic conditions.
- Saxena, Paridhi,Maida, Neha,Kapur, Manmohan
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supporting information
p. 11187 - 11190
(2019/09/30)
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- Method for removing sulfinyl group in heteroaryl compound
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The invention discloses a method for removing a sulfinyl group in a heteroaryl compound. The method is characterized in that a heteroaryl cyclic sulfoxide compound represented by formula (Ia) or formula (Ib) and trimethylsilylphenyl trifluoromethanesulfonate represented by formula (II) used a substrate are reacted in the presence of cesium fluoride to obtain a sulfinyl group-removed heteroaryl compound represented by formula (IIIa) or (IIIb). The method can rapidly remove the sulfinyl group in the heteroaryl cyclic sulfoxide compound, does not need a metal catalyst with poor safety or highly toxic organic reagents, and is safe. The method has the advantages of mild conditions, strong compatibility with some sensitive benzenesulfonyl groups and Boc groups, simplicity in post-treatment, andsuitableness for industrial production.
- -
-
Paragraph 0053-0056
(2019/10/01)
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- Desulfurization of Diaryl(heteroaryl) Sulfoxides with Benzyne
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Two benzyne-enabled desulfurization reactions have been demonstrated which convert diaryl sulfoxides and heteroaryl sulfoxides to biaryls and desulfurized heteroarenes, respectively. The reaction accessing biaryls tolerates a variety of functional groups, such as halides, pseudohalides, and carbonyls. Mechanistic studies reveal that both reactions proceed via a common assembly process but divergent disassemblies of the generated tetraaryl(heteroaryl) sulfuranes.
- Chen, De-Li,Sun, Yan,Chen, Mengyuan,Li, Xiaojin,Zhang, Lei,Huang, Xin,Bai, Yihui,Luo, Fang,Peng, Bo
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supporting information
(2019/06/13)
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- Catalytic Deprotonative α-Formylation of Heteroarenes by an Amide Base Generated in Situ from Tetramethylammonium Fluoride and Tris(trimethylsilyl)amine
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Heteroarene formylations in DMF solution proceed in the presence of an amide base catalyst generated in situ from tetramethylammonium fluoride (TMAF) and tris(trimethylsilyl)amine (N(TMS)3). The reaction proceeds at room temperature and has an operationally simple procedure. Various heteroarenes, including benzothiophene, thiophene, benzothiazole, oxazole, and indole derivatives, can be formylated with high functional group tolerance.
- Shigeno, Masanori,Fujii, Yuki,Kajima, Akihisa,Nozawa-Kumada, Kanako,Kondo, Yoshinori
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p. 443 - 451
(2019/04/30)
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- Competing dehalogenation versus borylation of aryl iodides and bromides under transition-metal-free basic conditions
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In this work, selectivity-controllable base-promoted transition-metal-free borylation and dehalogenation of aryl halides are described. Under the conditions of borylation, the dehalogenation which emerges as a competitive side reaction has been well-controlled by carefully controlling the borylation conditions. On the other hand, the dehalogenation using benzaldehyde as a hydrogen source has also been accomplished. The applications of direct radical borylation and dehalogenation of aryl halides demonstrate their synthetic practicability in pharmaceutical-oriented organic synthesis. Based on the experimental evidences, the tBuOK/1,10-Phen-triggered radical nature of both competitive reactions has been revealed.
- Niu, Yi-Jie,Sui, Guo-Hui,Zheng, Hong-Xing,Shan, Xiang-Huan,Tie, Lin,Fu, Jia-Le,Qu, Jian-Ping,Kang, Yan-Biao
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p. 10805 - 10813
(2019/09/30)
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- NITROGEN-CONTAINING BIOPOLYMER-BASED CATALYSTS, THEIR PREPARATION AND USES IN HYDROGENATION PROCESSES, REDUCTIVE DEHALOGENATION AND OXIDATION
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The present invention relates to a process for the preparation of a nitrogen containing biopolymer-based catalyst by pyrolysis of a metal complex with a nitrogen-containing biopolymer and to the nitrogen containing biopolymer-based catalysts obtainable by this process. In particular, the invention relates to a nitrogen containing biopolymer-based catalyst comprising metal particles and at least one nitrogen containing carbon layer. The invention also relates to the use of a nitrogen containing biopolymer-based catalyst in a hydrogenation process, preferably in a process for hydrogenation of nitroarenes, nitriles or imines; in a reductive dehalogenation process of C-X bonds, wherein X is CI, Br or I, preferably in a process for dehalogenation of organohalides or in a process for deuterium labelling of arenes via dehalogenation of organohalides; or in an oxidation process. Further, the invention relates to a metal complex with the nitrogen containing biopolymer, wherein the metal is a transition metal selected from the group consisting of manganese, ruthenium, cobalt, rhodium, nickel, palladium and platinum, preferably cobalt or nickel, and wherein the nitrogen containing biopolymer is selected from chitosan, chitin and a polyamino acid, preferably chitosan or chitin.
- -
-
Page/Page column 19
(2018/07/29)
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- Ag(I)-C-H Activation Enables Near-Room-Temperature Direct α-Arylation of Benzo[ b]thiophenes
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The first example of near-room-temperature α-arylation of benzo[b]thiophenes is reported. The discovery rests on the observation of a switch in α-/β-regioselectivity at different loadings of Pd2(dba)3·CHCl3 in the coupling between benzo[b]thiophene and 4-iodotoluene. We show that this unprecedented regioselectivity switch is driven by a Ag(I)-mediated C-H activation at the α-C-H position, which becomes the dominant mode of reactivity at low concentrations of Pd. Competition experiments, kinetic studies, KIE, and D/H scrambling experiments have been carried out supporting this mechanism.
- Colletto, Chiara,Panigrahi, Adyasha,Fernández-Casado, Jaime,Larrosa, Igor
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supporting information
p. 9638 - 9643
(2018/07/21)
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- Hydroconversion of Oxidation Products of Sulfur-Containing Aromatic Compounds
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Hydroconversion of benzo- and dibenzothiophene sulfone on a Ni–Mo sulfide catalyst based on mesoporous aluminosilicate Al-HMS and on unsupported catalysts prepared in situ in the course of decomposition of poorly soluble precursors (molybdenum hexacarbonyl, nickel naphthenate) was investigated. Hydrogenation of sulfones was performed at 250°С, 340°С, and 380°С and elevated СО pressure in the presence of H2O ensuring in situ generation of H2 via water-gas shift reaction. The products that are formed by oxidation of organic sulfur compounds and remain in the hydrocarbon medium (mainly sulfones) will not significantly affect the subsequent hydrotreatment since under the conditions of hydroprocesses, they transform into the corresponding benzo- and dibenzothiophenes, which undergo the subsequent hydrodesulfurization to form mono- and diaromatic hydrocarbons.
- Vutolkina,Akopyan,Glotov,Kotelev,Maksimov,Karakhanov
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p. 981 - 989
(2018/08/31)
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- Cu/Fe/O=PPh3-catalyzed etherification for the synthesis of aryl 3-benzo[b]thienyl ethers
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Cu/Fe-cocatalyzed cross-coupling reactions between 3-bromobenzo[b]thiophene and hydroxyaryls are described herein. The combination of Cu and Fe catalysts is important for the progress of the reactions, and the use of triphenylphosphine oxide as a ligand suppresses the dehalogenation of 3-bromobenzo[b]thiophene, and promptly facilitates the reaction. The obtained aryl benzo[b]thienyl ethers can be converted to π-extended thienobenzofuran derivatives via Pd-catalyzed dehy-drogenative cyclizations.
- Mitsudo, Koichi,Asada, Takuya,Inada, Tomohiro,Kurimoto, Yuji,Mandai, Hiroki,Suga, Seiji
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supporting information
p. 1044 - 1047
(2018/08/24)
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- Synthesis, crystal structure and reactivity of η2-thiophyne Ni complexes
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The first synthesis and crystal structures of five-membered ring aryne complexes, Ni(dcpe)(η2-thiophyne) and Ni(dcpe)(η2-benzo[b]thiophyne), are described. The aryne fragments retain considerable aromatic character and the two coordi
- Terada, Misaki,Nishii, Yuji,Miura, Masahiro
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p. 2918 - 2921
(2018/03/23)
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- Palladium/Copper Dual Catalysis for the Cross-Coupling of Aryl(trialkyl)silanes with Aryl Bromides
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Whereas aryl(trialkyl)silanes are considered to be ideal organometallic reagents for cross-coupling reactions owing to their stability, low toxicity, solubility, and easy accessibility, they are generally inert under typical cross-coupling conditions. Disclosed herein is a palladium/copper catalytic system that enables the cross-coupling of trimethyl, triethyl, tert-butyldimethyl, and triisopropyl aryl silanes with aryl bromides. This process is applicable to the sequential C?H and C?Si bond arylation of thiophenes and the synthesis of poly(thiophene–fluorene)s.
- Komiyama, Takeshi,Minami, Yasunori,Furuya, Yuki,Hiyama, Tamejiro
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supporting information
p. 1987 - 1990
(2018/02/10)
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- Decarbonylation of Aromatic Aldehydes and Dehalogenation of Aryl Halides Using Maghemite-Supported Palladium Catalyst
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A facile decarbonylation reaction of a variety of aromatic and heteroaromatic aldehydes using maghemite-supported palladium catalyst has been developed. The magnetic properties of catalyst facilitated an easy and efficient recovery of the catalyst from the reaction mixture using an external magnet. It was found that the catalyst could be reused up to four consecutive catalytic runs without a significant change in activity. In addition, the catalyst was also very effective in the dehalogenation of aryl halides. This is the first report on efficient utilization of directly immobilized Pd on maghemite in decarbonylation and dehalogenation reactions.
- Ajda?i?, Vladimir,Nikoli?, Andrea,Simi?, Stefan,Manojlovi?, Dragan,Stojanovi?, Zoran,Nikodinovic-Runic, Jasmina,Opsenica, Igor M.
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p. 119 - 126
(2017/12/27)
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- Transition-metal-free hydrogenation of aryl halides: From alcohol to aldehyde
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A transition-metal-and catalyst-free hydrogenation of aryl halides, promoted by bases with either aldehydes or alcohols, is described. One equivalent of benzaldehyde affords an equal yield as that of 0.5 equiv of benzyl alcohol. The kinetic study reveals that the initial rate of PhCHO is much faster than that of BnOH, in the ratio of nearly 4:1. The radical trapping experiments indicate the radical nature of this reaction. Based on the kinetic study, trapping and KIE experiments, and control experiments, a tentative mechanism is proposed. As a consequence, a wide range of (hetero)aryl iodides and bromides were efficiently reduced to their corresponding (hetero)arenes. Thus, for the first time, aldehydes are directly used as hydrogen source instead of other well-established alcohol-hydrogen sources.
- Zheng, Hong-Xing,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 5114 - 5117
(2017/11/07)
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- Carboxylation of Aromatic and Aliphatic Bromides and Triflates with CO2 by Dual Visible-Light–Nickel Catalysis
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We report the efficient carboxylation of bromides and triflates with K2CO3 as the source of CO2 in the presence of an organic photocatalyst in combination with a nickel complex under visible light irradiation at room temperature. The reaction is compatible with a variety of functional groups and has been successfully applied to the synthesis and derivatization of biologically active molecules. In particular, the carboxylation of unactivated cyclic alkyl bromides proceeded well with our protocol, thus extending the scope of this transformation. Spectroscopic and spectroelectrochemical investigations indicated the generation of a Ni0 species as a catalytic reactive intermediate.
- Meng, Qing-Yuan,Wang, Shun,K?nig, Burkhard
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supporting information
p. 13426 - 13430
(2017/10/07)
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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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- Hydrodehalogenation of Haloarenes by a Sodium Hydride–Iodide Composite
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A simple protocol for hydrodebromination and -deiodination of halo(hetero)arenes was enabled by sodium hydride (NaH) in the presence of lithium iodide (LiI). Mechanistic studies showed that an unusual concerted nucleophilic aromatic substitution operates in the present process.
- Ong, Derek Yiren,Tejo, Ciputra,Xu, Kai,Hirao, Hajime,Chiba, Shunsuke
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supporting information
p. 1840 - 1844
(2017/02/05)
-
- A Biomass-Derived Non-Noble Cobalt Catalyst for Selective Hydrodehalogenation of Alkyl and (Hetero)Aryl Halides
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Hydrodehalogenation is a straightforward approach for detoxifications of harmful anthropogenic organohalide-based pollutants, as well as removal of halide protecting groups used in multistep syntheses. A novel sustainable catalytic material was prepared from biowaste (chitosan) in combination with an earth-abundant cobalt salt. The heterogeneous catalyst was fully characterized by transmission electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy measurements, and successfully applied to hydrodehalogenation of alkyl and (hetero)aryl halides with broad scope (>40 examples) and excellent chemoselectivity using molecular hydrogen as a reductant. The general usefulness of this method is demonstrated by successful detoxification of non-degradable pesticides and fire retardants. Moreover, the potential of the catalyst as a deprotection tool is demonstrated in a multistep synthesis of (±)-peronatin B (alkaloid).
- Sahoo, Basudev,Surkus, Annette-Enrica,Pohl, Marga-Martina,Radnik, J?rg,Schneider, Matthias,Bachmann, Stephan,Scalone, Michelangelo,Junge, Kathrin,Beller, Matthias
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supporting information
p. 11242 - 11247
(2017/09/02)
-
- Palladium-Catalyzed Synthesis of 2,3-Disubstituted Benzothiophenes via the Annulation of Aryl Sulfides with Alkynes
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A new method has been developed for the synthesis of 2,3-disubstituted benzothiophenes involving the palladium-catalyzed annulation of aryl sulfides with alkynes. This convergent approach exhibited good functional group tolerance, providing rapid access to a diverse array of derivatives from simple, readily available starting materials. This protocol can also be used to synthesize 2-silyl-substituted benzothiophenes, which can be used as versatile platforms for the synthesis of 2,3-unsymmetrically substituted benzothiophenes.
- Masuya, Yoshihiro,Tobisu, Mamoru,Chatani, Naoto
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supporting information
p. 4312 - 4315
(2016/11/03)
-
- Palladium Nanoparticles Supported on Fibrous Silica (KCC-1-PEI/Pd): A Sustainable Nanocatalyst for Decarbonylation Reactions
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A practical and convenient decarbonylation of a variety of aromatic, heteroaromatic, and alkenyl aldehydes by using palladium nanoparticles supported on novel, fibrous nanosilica, named KCC-1-PEI/Pd, has been developed. Complete conversion of aldehyde functionalities into deformylated products was achieved in all cases and in nearly all cycles tested by reusing the catalyst systems. This method eliminates further purification of products after their isolation. Syntheses of at least three different deformylated products have been shown in sequence with the same catalyst system, which neither requires use of any additives, such as oxidants and bases, nor CO scavengers.
- Kundu, Pintu K.,Dhiman, Mahak,Modak, Atanu,Chowdhury, Arindam,Polshettiwar, Vivek,Maiti, Debabrata
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p. 1142 - 1146
(2016/11/23)
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- Bimetallic Cu/Pd Catalysts with Bridging Aminopyrimidinyl Phosphines for Decarboxylative Cross-Coupling Reactions at Moderate Temperature
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A bimetallic catalyst system is presented that enables the decarboxylative cross-coupling of triflates with carboxylate salts at only 100 °C, which is 70 °C lower than with previous Cu/Pd-based systems. The new protocol allows the coupling of a broad range of aryl triflates with various substituted 2-nitrobenzoates in good to excellent yields. The key feature of the catalyst system is a bidentate P,N-ligand designed to bridge the Pd and Cu centres and thereby facilitating the rate-determining transmetalation step. Mass spectrometry (ESI-MS) studies support the ability of the aminopyrimidinyl phosphine to simultaneously coordinate copper and palladium.
- Hackenberger, Dagmar,Song, Bingrui,Grünberg, Matthias F.,Farsadpour, Saeid,Menges, Fabian,Kelm, Harald,Gro?, Cedric,Wolff, Timm,Niedner-Schatteburg, Gereon,Thiel, Werner R.,Goo?en, Lukas J.
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p. 3579 - 3588
(2015/11/10)
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- Gold-Catalyzed Proto- and Deuterodeboronation
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A mild gold-catalyzed protodeboronation reaction, which does not require acid or base additives and can be carried out in "green" solvents, is described. As a result, the reaction is very functional-group-tolerant, even to acid- and base-sensitive functional groups, and should allow for the boronic acid group to be used as an effective traceless directing or blocking group. The reaction has also been extended to deuterodeboronations for regiospecific ipso-deuterations of aryls and heteroaryls from the corresponding organoboronic acid. Based on density functional theory calculations, a mechanism is proposed that involves nucleophilic attack of water at boron followed by rate-limiting B-C bond cleavage and facile protonolysis of a Au-σ-phenyl intermediate.
- Barker, Graeme,Webster, Stacey,Johnson, David G.,Curley, Rachel,Andrews, Matthew,Young, Paul C.,MacGregor, Stuart A.,Lee, Ai-Lan
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p. 9807 - 9816
(2015/11/03)
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- Ligand-free, palladium-catalyzed dihydrogen generation from TMDS: Dehalogenation of aryl halides on water
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A mild and environmentally attractive dehalogenation of functionalized aryl halides has been developed using nanoparticles formed from PdCl2 in the presence of tetramethyldisiloxane (TMDS) on water. The active catalyst and reaction medium can be recycled. This method can also be applied to cascade reactions in a one-pot sequence.
- Bhattacharjya, Anish,Klumphu, Piyatida,Lipshutz, Bruce H.
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supporting information
p. 1122 - 1125
(2015/03/14)
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- NaBH4-TMEDA and a palladium catalyst as efficient regio- and chemoselective system for the hydrodehalogenation of halogenated heterocycles
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The pair NaBH4-TMEDA as hydride source and a palladium catalyst in THF prove to be an efficient system for the hydrodehalogenation of halogenated heterocycles with one or more heteroatoms. In general, Pd(OAc) 2-PPh3 rapidly hydrodehalogenates reactive halo-heterocycles such as bromo-pyridines, -quinolines, -thiophenes, -indoles, -imidazoles, etc., at room temperature in very good yields, whereas in most cases PdCl2(dppf) reduces less reactive halides such as chloro-pyridines, -quinolines, -pyrimidines and bromo-indoles, -benzofurans, etc. Moreover, PdCl2(tbpf) shows to be even more active removing the 2- and 5-chlorine from both thiophene and thiazole rings. The reaction conditions tolerate various functional groups, allowing highly chemoselective reactions in the presence of halide, ester, alkyne, alkene and nitrile substituents. Moreover, with a proper selection of the catalyst it is also possible to obtain a good control in the regioselective hydrodehalogenation of a variety of polyhalogenated substrates.
- Chelucci, Giorgio,Figus, Susanna
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p. 191 - 209
(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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- Hydrogenation of sulfoxides to sulfides under mild conditions using ruthenium nanoparticle catalysts
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The first demonstration of the hydrogenation of sulfoxides under atmospheric H2 pressure is reported. The highly efficient reaction is facilitated by a heterogeneous Ru nanoparticle catalyst. The mild reaction conditions enable the selective hydrogenation of a wide range of functionalized sulfoxides to the corresponding sulfides. The high redox ability of RuO x nanoparticles plays a key role in the hydrogenation.
- Mitsudome, Takato,Takahashi, Yusuke,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 8348 - 8351
(2014/08/18)
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- Preparation of functional styrenes from biosourced carboxylic acids by copper catalyzed decarboxylation in PEG
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A general protocol for the copper-catalyzed decarboxylation of α,β-unsaturated carboxylic acids in PEG, particularly of biosourced cinnamic acid analogues, is reported. Moderate to high isolated yields (31-96%) towards the styrene derivatives were obtained. For the first time, decarboxylation of α-amino acids to the corresponding amines was successfully performed with good to high yields and extended to the decarboxylation of a few condensed heterocyclic compounds. Both the use of PEG as a green solvent and direct separation of the pure product of the reaction by distillation permitted the reuse of the solvent and the Cu-based catalytic system over several cycles without deactivation. This was extended to the synthesis of 4-vinylguaiacol on the laboratory scale in an average 92% yield. This journal is the Partner Organisations 2014.
- Cadot, Stephane,Rameau, Nelly,Mangematin, Stephane,Pinel, Catherine,Djakovitch, Laurent
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supporting information
p. 3089 - 3097
(2014/06/10)
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- Protodecarboxylation of carboxylic acids over heterogeneous silver catalysts
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A heterogeneous supported Ag catalyst for the protodecarboxylation of aromatic carboxylic acids has been developed. Control of the metal particle size proved extremely important. The highest activity was achieved with a silver loading of 10 wt%, which had relatively big metal crystallites of 40 nm. It is inferred that the adsorption of the aromatic moiety requires terrace sites rather than edges or corners at the metal nanoparticle. The amphoteric support, γ-Al2O3, gave the most active catalysts. Oxygen coverage of the surface is essential for catalytic activity. A mechanism has been proposed with the critical steps (1) formation of a benzoyl anion by reaction with a base in the reaction medium, (2) binding of the anionic species at the Ag+ surface sites with (3) extrusion of CO2 and (4) proton transfer from another molecule of carboxylic acid, followed by desorption of the decarboxylated species and binding of the benzoate to the active site to complete the catalytic cycle. With 2-nitrobenzoic acid as substrate, the catalyst had a turnover frequency (TOF) of 216 h-1. The catalyst showed good activity for benzoic acid with nitro, methoxy and halogen substituents at the ortho-position as well as for heteroaromatic carboxylic acids. The Royal Society of Chemistry.
- Toy, Xiu Yi,Roslan, Irwan Iskandar Bin,Chuah, Gaik Khuan,Jaenicke, Stephan
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p. 516 - 523
(2014/02/14)
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- An efficient dehydroxymethylation reaction by a palladium catalyst
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A general method for selective dehydroxymethylation has been discovered by using widely available Pd(OAc)2. The present study offers a new synthetic strategy for the regioselective functionalization by employing the steric, electronic and coordinating nature of the hydroxymethyl (-CH 2OH) group temporarily.
- Modak, Atanu,Naveen, Togati,Maiti, Debabrata
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supporting information
p. 252 - 254
(2013/02/22)
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- A novel synthesis of benzo[b]thiophene
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We report a convenient method of preparation of benzo[b]thiophene, using 2-chlorobenzaldehyde and 2-mercaptoacetonitrile as starting materials. The process comprises two steps, neither of which has been reported previously. The reactions in this work are
- Liao, Zutai,Lv, Xuehao,Tao, Ming
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p. 4021 - 4024
(2013/11/19)
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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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- Gold(I)-catalyzed protodecarboxylation of (Hetero)aromatic carboxylic acids
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Readily available, inexpensive and easy to handle, carboxylic acids have been shown to be very effective, greener coupling partners compared to costly organometallic reagents for the formation of C-C bonds. The use of well-defined gold complexes furnished 3 in slightly better yield with butyric acid, and in quantitative yield with adamantane-1-carboxylic acid. All reactions reached completion within 16 h. As with silver systems, this reactivity trend highlights, as previously observed, the benefits of potential coordinating groups in the ortho position to the gold binding site, which possibly facilitate the decarboxylation step. Additional reaction time and increased temperatures were necessary to afford the gold aryl products in satisfactory yields. Yet, some substrates such as 2-nitrobenzoic acids reacted poorly and could only be transformed in 50% yield.
- Dupuy, Stéphanie,Nolan, Steven P.
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supporting information
p. 14034 - 14038
(2013/11/19)
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- Room-temperature hydrodehalogenation of halogenated heteropentalenes with one or two heteroatoms
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The pair NaBH4-TMEDA as a hydride source and catalytic PdCl 2(dppf) in THF prove to be an efficient system for the hydrodehalogenation of bromo(chloro)-heteropentalenes with one or two heteroatoms, while Pd(OAc)2/PPh3 is able to reduce reactive haloheteropentalenes, and PdCl2(tbpf) allows the removal of the 2-chlorine from a thiophene ring. The reaction conditions tolerate various functional groups, allowing highly chemoselective reactions in the presence of halide, ester, alkyne, alkene, and nitrile substituents and also showing good efficiency in the regioselective hydrodehalogenation of a variety of polyhalogenated substrates.
- Chelucci, Giorgio,Baldino, Salvatore,Ruiu, Andrea
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p. 9921 - 9925,5
(2012/12/12)
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- Fluoroform-derived CuCF3 for low-cost, simple, efficient, and safe trifluoromethylation of aryl boronic acids in air
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Easy does it: Aryl boronic acids undergo smooth and selective trifluoromethylation with low-cost fluoroform-derived CuCF3 in DMF in non-dried air. The reaction occurs under mild conditions (1 atm, room temperature), exhibits unprecedented funct
- Novak, Petr,Lishchynskyi, Anton,Grushin, Vladimir V.
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supporting information; experimental part
p. 7767 - 7770
(2012/08/29)
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- Preparation of 4,7-dibromobenzo[b]thiophene as a versatile building block and synthetic application to a bis(ethynylthienyl)oligoarene system
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Benzo[b]thiophene, 4,7-dibromobenzo[b]thiophene, thieno[3,2-b]thiophene, and 3-bromothieno[3,2-b]thiophene were prepared by AuCl-catalyzed cyclization of (t-butylsulfanyl)(ethynyl)benzenes or (t-butylsulfanyl)(ethynyl)thiophenes. Several reactions of 4,7-dibromobenzo[b]thiophene were investigated, including metallation and cross coupling reactions.
- Yamamoto, Takuya,Katsuta, Hiroshi,Toyota, Kozo,Iwamoto, Takeaki,Morita, Noboru
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p. 613 - 623
(2012/06/29)
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- A general and efficient aldehyde decarbonylation reaction by using a palladium catalyst
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A facile decarbonylation reaction of aldehydes has been developed by employing Pd(OAc)2. A wide variety of substrates are decarbonylated, without using any exogenous ligand for palladium as well as CO-scavenger.
- Modak, Atanu,Deb, Arghya,Patra, Tuhin,Rana, Sujoy,Maity, Soham,Maiti, Debabrata
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supporting information; experimental part
p. 4253 - 4255
(2012/05/04)
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- Ligand-free Ni-catalyzed reductive cleavage of inert carbon - Sulfur bonds
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A catalytic reductive cleavage of C(sp2) - and C(sp3) - SMe bonds under ligandless conditions is presented. The method is characterized by its wide scope and high chemoselectivity profile including challenging substrate combinations, allowing the design of orthogonal and site-selectivity approaches.
- Barbero, Nekane,Martin, Ruben
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supporting information; experimental part
p. 796 - 799
(2012/04/23)
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- A continuous protodecarboxylation of heteroaromatic carboxylic acids in sulfolane
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A versatile, scalable method for the decarboxylation of indole-2-carboxylic acids has been found. With one equivalent of DBU in sulfolane, indole-2-carboxylic acid derivatives were cleanly decarboxylated in a 316 stainless steel tube reactor at 300 °C within 20 min. The corresponding indole derivatives were obtained in good yields. It was also found that indole-2-carboxylic acid (1) can be decarboxylated in either pure sulfolane or sulfolane with 3% water at 300 °C within 20 min. (1) The decarboxylation with one equivalent of DBU could successfully be transferred to benzo[b]thiophene-2-carboxylic acid derivatives if a prolonged reaction time was used. (2) Picolinic acid could also be decarboxylated in sulfolane with 3% water, and thiophene-2-carboxylic acid was smoothly decarboxylated with DABCO instead of DBU. (3) Benzoic acid derivatives were either inert or decomposed under the reaction conditions.
- Tilstam, Ulf
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p. 1449 - 1454
(2012/10/30)
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- Selective copper- or silver-catalyzed decarboxylative deuteration of aromatic carboxylic acids
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The practical utility of decarboxylative transformations in organic synthesis is discussed, and the decarboxylative deuteration of (hetero)aromatic carboxylic acids is disclosed as a further example. Various monodeuterated arenes were synthesized under mild conditions, in a single step from easily accessible aromatic carboxylic acids and deuterium oxide. Copper catalysts were found to have the widest scope, but silver catalysts are superior for some ortho-substituted benzoates. A few substrates, e.g. quinoline-2-carboxylic acid, decarboxylate even in the absence of a metal catalyst. Georg Thieme Verlag Stuttgart · New York.
- Rudzki, Martin,Alcalde-Aragones, Ana,Dzik, Wojciech I.,Rodriguez, Nuria,Goossen, Lukas J.
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scheme or table
p. 184 - 193
(2012/03/26)
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- CuI/TMEDA-catalyzed annulation of 2-bromo alkynylbenzenes with Na 2S: Synthesis of benzo[b]thiophenes
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A copper-catalyzed thiolation annulation reaction of 2-bromo alkynylbenzenes with sodium sulfide has been developed. In the presence of CuI and TMEDA, a variety of 2-substituted benzo[b]thiophenes were readily prepared in moderate to good yields by the reaction of 2-bromo alkynylbenzenes and Na2S?9H2O.
- Sun, Lei-Lei,Deng, Chen-Liang,Tang, Ri-Yuan,Zhang, Xing-Guo
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experimental part
p. 7546 - 7550
(2011/11/29)
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- Hyperaromatic stabilization of arenium ions: Cyclohexa- and cycloheptadienyl cations-experimental and calculated stabilities and ring currents
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Measurements of pKR show that the cycloheptadienyl cation is less stable than the cyclohexadienyl (benzenium) cation by 18 kcal mol -1. This difference is ascribed here to "hyperaromaticity" of the latter. For the cycloheptadienyl cation a value of KR = [ROH][H+]/[R+] is assigned by combining a rate constant for reaction of the cation with water based on the azide clock with a rate constant for the acid-catalyzed formation of the cation accompanying equilibration of cycloheptadienol with its trifluoroethyl ether in TFE-water mixtures. Comparison of pKR = -16.1 with pKR = -2.6 for the cyclohexadienyl cation yields the difference in stabilities of the two ions. Interpretation of this difference in terms of hyperconjugative aromaticity is supported by the effect of benzannelation in reducing pKR for the benzenium ion: from -2.6 down to -3.5 for the 1H-naphthalenium and -6.0 for the 9H-anthracenium ions, respectively. MP2/6-311+G* and G3MP2 calculations of hydride ion affinities of benzenium ions show an order of stabilities for substituents at the methylene group consistent with their hyperconjugative abilities, i.e., (H3Si)2 > cyclopropyl > H 2 > Me2> (HO)2 > F2. Calculations of ring currents show a similar ordering. No conventional ring current is seen for the cycloheptadienyl cation, whereas currents in the F 2-substituted benzenium ion are consistent with antiaromaticity. Arenium ions where the methylene group is substituted with a single OH group show characteristic energy differences between conformations, with C-H or C-OH bonds respectively occupying or constrained to axial positions favorable to hyperconjugation. The differences were found to be 8.8, 6.3, 2.4, and 0.4 kcal mol-1 for benzenium, naphthalenium, phenanthrenium, and cyclohexenyl cations, respectively.
- Lawlor, David A.,Bean, David E.,Fowler, Patrick W.,Keeffe, James R.,Kudavalli, Jaya Satyanarayana,More O'Ferrall, Rory A.,Rao, S. Nagaraja
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supporting information; scheme or table
p. 19729 - 19742
(2012/01/31)
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- Electrochemical hydroxylation of organoboron compounds
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Cathodic hydroxylation of organoboron compounds was successfully performed under an oxygen atmosphere, producing the corresponding phenol derivatives with high selectivity and efficiency.
- Hosoi, Kohei,Kuriyama, Yu,Inagi, Shinsuke,Fuchigami, Toshio
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supporting information; experimental part
p. 1284 - 1286
(2010/07/05)
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