- Mild olefin formationviabio-inspired vitamin B12photocatalysis
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Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12to be a powerful platform for developing mild olefin-forming reactions.
- Bam, Radha,Pollatos, Alexandros S.,Moser, Austin J.,West, Julian G.
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p. 1736 - 1744
(2021/02/22)
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- Heterogeneous Isomerization for Stereoselective Alkyne Hydrogenation to trans-Alkene Mediated by Frustrated Hydrogen Atoms
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Stereoselective production of alkenes from the alkyne hydrogenation plays a crucial role in the chemical industry. However, for heterogeneous metal catalysts, the olefins in cis-configuration are usually dominant in the products due to the most important and common Horiuti-Polanyi mechanism involved over the metal surface. In this work, through combined theoretical and experimental investigations, we demonstrate a novel isomerization mechanism mediated by the frustrated hydrogen atoms via the H2 dissociation at the defect on solid surface, which can lead to the switch in selectivity from the cis-configuration to trans-configuration without overhydrogenation. The defective Rh2S3 with exposing facet of (110) exhibits outstanding performance as a heterogeneous metal catalyst for stereoselective production of trans-olefins. With the frustrated hydrogen atoms at spatially separated high-valence Rh sites, the isolated hydrogen mediated cis-to-trans isomerization of olefins can be effectively conducted and the overhydrogenation can be completely inhibited. Furthermore, the bifunctional Rh-S/Pd nanosheets have been synthesized through the surface modification of Pd nanosheets with rhodium and sulfide. With the selective semihydrogenation of alkynes into cis-olefins catalyzed by the small surface PdSx ensembles, the bifunctional Rh-S/Pd nanosheets exhibit excellent activity and stereoselectivity in the one-pot alkyne hydrogenation into trans-olefin, which surpasses the most reported homogeneous and heterogeneous catalysts.
- Zhang, Weijie,Qin, Ruixuan,Fu, Gang,Zheng, Nanfeng
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supporting information
p. 15882 - 15890
(2021/10/02)
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- Pd catalysts supported on dual-pore monolithic silica beads for chemoselective hydrogenation under batch and flow reaction conditions
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Two different types of palladium catalysts supported on dual-pore monolithic silica beads [5% Pd/SM and 0.25% Pd/SM(sc)] for chemoselective hydrogenation were developed. Alkyne, alkene, azide, and nitro functionalities and the aromatic N-Cbz protecting group were chemoselectively hydrogenated using 5% Pd/SM. On the other hand, 0.25% Pd/SM(sc) showed unique and higher hydrogenation catalyst activity toward a wide variety of reducible functionalities. Furthermore, the catalyst activities of both 5% Pd/SM and 0.25% Pd/SM(sc) under flow hydrogenation conditions were also evaluated. A pre-packed 5% Pd/SM cartridge could be used continuously for at least 72 h without any loss of catalyst activity. The 0.2% Pd/SM(sc) catalyst prepacked in a cartridge showed high catalyst activity for the flow hydrogenation of trisubstituted alkenes under mild reaction conditions. This journal is
- Yamada, Tsuyoshi,Ogawa, Aya,Masuda, Hayato,Teranishi, Wataru,Fujii, Akiko,Park, Kwihwan,Ashikari, Yosuke,Tomiyasu, Noriyuki,Ichikawa, Tomohiro,Miyamoto, Riichi,Bai, Hongzhi,Matsuyama, Kiyoshi,Nagaki, Aiichiro,Sajiki, Hironao
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p. 6359 - 6367
(2020/11/03)
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- Synthesis of alkyl sulfones from alkenes and tosylmethylphosphonium iodide through photo-promoted cc bond formation
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A new synthetic method for alkyl sulfones through CC bond formation between alkenes and tosylmethylphosphonium iodide is reported. A tosylmethyl radical is generated from the phosphonium iodide under irradiation of visible light with the aid of fac-Ir(ppy)3. It undergoes regioselective 1,2-addition across the carboncarbon double bond to afford an elongated alkyl radical, which abstracts a hydrogen atom from C6F5SH, producing an alkyl sulfone with one-carbon extension.
- Miura, Tomoya,Miyakawa, Sho,Moriyama, Daisuke,Murakami, Masahiro
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supporting information
p. 1382 - 1385
(2020/11/26)
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- Visible-Light-Induced [4+2] Annulation of Thiophenes and Alkynes to Construct Benzene Rings
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The [4+2] annulation represents an elegant and versatile synthetic protocol for the construction of benzene rings. Herein, a strategy for visible-light induced [4+2] annulation of thiophenes and alkynes, to afford benzene rings, is presented. Under simple and mild reaction conditions, the ready availability and structural diversity of thiophenes and alkynes permit the facile synthesis of several substituted aromatic rings. Valuable drugs and amino acids are also well tolerated. Moreover, DFT calculations explain the high regioselectivity of the reaction.
- Song, Chunlan,Dong, Xin,Wang, Zhongjie,Liu, Kun,Chiang, Chien-Wei,Lei, Aiwen
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supporting information
p. 12206 - 12210
(2019/07/31)
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- The catalytic cleavage of carbon-carbon double bond in polychloroprene induced by Schwartz's reagent via chlorine self-assisted β-alkyl elimination mechanism
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The carbon-carbon double bonds (C[dbnd]C) in polychloroprene (PCP) was broken down by Schwartz's reagent ([Cp2ZrClH]n) under mild conditions. The reaction mechanism for cleaving C[dbnd]C bonds in PCP was studied in detail. It was found that the cleavage pathway was chlorine self-assisted β-alkyl elimination reaction, namely, β-alkyl elimination was promoted while chlorine in PCP was eliminated by releasing Cp2ZrCl2. The molecular weights of chain-scission products were controlled ranging from starting molecular weights of PCP to 0.2 kg mol?1; at the same time, microstructures of chain-scission products were similar to chain structures of original PCP. In addition, chain-scission products could be chain-end functionalized by electrophiles quenching chain scission reaction. More importantly, efficient catalytic chain cleavage was achieved under the synergistic effect of [Cp2ZrClH]n with both LiH and H2.
- Gu, Yang,Ye, Lin,Lin, Fei,Lin, Yichao,Tang, Tao,Ma, Li
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- Room Temperature Chemoselective Deoxygenation of Aromatic Ketones and Aldehydes Promoted by a Tandem Pd/TiO2 + FeCl3 Catalyst
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A rapid and practical protocol for the chemoselective deoxygenation of various aromatic ketones and aldehydes was described, which used a tandem catalyst composed of heterogeneous Pd/TiO2 + homogeneous FeCl3 with the green hydrogen source, polymethylhydrosiloxane (PMHS). The developed catalytic system was robust and scalable, as exemplified by the deoxygenation of acetophenone, which was performed on a gram scale in an atmospheric environment utilizing only 0.4 mol % Pd/TiO2 + 10 mol % FeCl3 catalyst to give the corresponding ethylbenzene in 96% yield within 10 min at room temperature. Furthermore, the Pd/TiO2 catalyst was shown to be recyclable up to three times without an observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions. Insights toward the reaction mechanism of Pd-catalyzed reductive deoxygenation for aromatic ketones and aldehydes were investigated through operando IR, NMR, and GC-MS techniques.
- Dong, Zhenhua,Yuan, Jinwei,Xiao, Yongmei,Mao, Pu,Wang, Wentao
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p. 11067 - 11073
(2018/09/12)
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- Synthesis of Elongated Esters from Alkenes
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A convenient method for synthesizing elongated aliphatic esters from alkenes is reported. An (alkoxycarbonyl)methyl radical species is generated upon visible-light irradiation of an ester-stabilized phosphorus ylide in the presence of a photoredox catalyst. This radical species adds onto the carbon–carbon double bond of an alkene to produce an elongated aliphatic ester.
- Miura, Tomoya,Funakoshi, Yuuta,Nakahashi, Junki,Moriyama, Daisuke,Murakami, Masahiro
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p. 15455 - 15459
(2018/10/31)
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- Synthesis of quinolinyl-based pincer copper(ii) complexes: an efficient catalyst system for Kumada coupling of alkyl chlorides and bromides with alkyl Grignard reagents
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Quinolinamide-based pincer copper(ii) complexes, κN,κN,κN-{C9H6N-(μ-N)-C(O)CH2NEt2}CuX [(QNNNEt2)CuX (X = Cl, 2; X = Br, 3; X = OAc, 4)], were synthesized by the reaction of ligand (QNNNEt2)-H (1) with CuX2 (X = Cl, Br or OAc) in the presence of Et3N. The reaction of (QNNNEt2)-H with CuX (X = Cl, Br or OAc) also afforded the Cu(ii) complexes 2, 3 and 4, respectively, instead of the expected Cu(i) pincer complexes. The formation of Cu(ii) complexes from Cu(i) precursors most likely occurred via the disproportionation reaction of Cu(i) into Cu(0) and Cu(ii). A cationic complex [(QNNNEt2)Cu(CH3CN)]OTf (5) was synthesized by the treatment of neutral complex 2 with AgOTf. On the other hand, the reaction of (QNNNEt2)-H (1) with [Cu(MeCN)4]ClO4 produced cationic Cu(i) complex, [(QNN(H)NEt2)Cu(CH3CN)]ClO4 (6), in good yield. All complexes 2-5 were characterized by elemental analysis and HRMS measurements. Furthermore, the molecular structures of 2, 3 and 4 were elucidated by X-ray crystallography. Complex 4 crystallizes in a dimeric and catemeric pattern. The cationic complex 5 was found to be an efficient catalyst for the Kumada coupling reaction of diverse nonactivated alkyl chlorides and bromides with alkyl magnesium chloride under mild reaction conditions.
- Pandiri, Hanumanprasad,Gonnade, Rajesh G.,Punji, Benudhar
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supporting information
p. 16747 - 16754
(2018/12/05)
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- Transfer Hydrogenation of Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex: Scope and Mechanism
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The first general catalytic approach to effecting transfer hydrogenation (TH) of unactivated alkenes using ethanol as the hydrogen source is described. A new NCP-type pincer iridium complex (BQ-NCOP)IrHCl containing a rigid benzoquinoline backbone has been developed for efficient, mild TH of unactivated C-C multiple bonds with ethanol, forming ethyl acetate as the sole byproduct. A wide variety of alkenes, including multisubstituted alkyl alkenes, aryl alkenes, and heteroatom-substituted alkenes, as well as O- or N-containing heteroarenes and internal alkynes, are suitable substrates. Importantly, the (BQ-NCOP)Ir/EtOH system exhibits high chemoselectivity for alkene hydrogenation in the presence of reactive functional groups, such as ketones and carboxylic acids. Furthermore, the reaction with C2D5OD provides a convenient route to deuterium-labeled compounds. Detailed kinetic and mechanistic studies have revealed that monosubstituted alkenes (e.g., 1-octene, styrene) and multisubstituted alkenes (e.g., cyclooctene (COE)) exhibit fundamental mechanistic difference. The OH group of ethanol displays a normal kinetic isotope effect (KIE) in the reaction of styrene, but a substantial inverse KIE in the case of COE. The catalysis of styrene or 1-octene with relatively strong binding affinity to the Ir(I) center has (BQ-NCOP)IrI(alkene) adduct as an off-cycle catalyst resting state, and the rate law shows a positive order in EtOH, inverse first-order in styrene, and first-order in the catalyst. In contrast, the catalysis of COE has an off-cycle catalyst resting state of (BQ-NCOP)IrIII(H)[O(Et)···HO(Et)···HOEt] that features a six-membered iridacycle consisting of two hydrogen-bonds between one EtO ligand and two EtOH molecules, one of which is coordinated to the Ir(III) center. The rate law shows a negative order in EtOH, zeroth-order in COE, and first-order in the catalyst. The observed inverse KIE corresponds to an inverse equilibrium isotope effect for the pre-equilibrium formation of (BQ-NCOP)IrIII(H)(OEt) from the catalyst resting state via ethanol dissociation. Regardless of the substrate, ethanol dehydrogenation is the slow segment of the catalytic cycle, while alkene hydrogenation occurs readily following the rate-determining step, that is, β-hydride elimination of (BQ-NCOP)Ir(H)(OEt) to form (BQ-NCOP)Ir(H)2 and acetaldehyde. The latter is effectively converted to innocent ethyl acetate under the catalytic conditions, thus avoiding the catalyst poisoning via iridium-mediated decarbonylation of acetaldehyde.
- Wang, Yulei,Huang, Zhidao,Leng, Xuebing,Zhu, Huping,Liu, Guixia,Huang, Zheng
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supporting information
p. 4417 - 4429
(2018/04/05)
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- Ru-Catalyzed Transfer Hydrogenation of Nitriles, Aromatics, Olefins, Alkynes and Esters
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This paper reports the preparation of new ruthenium(II) complexes supported by a pyrazole-phosphine ligand and their application to transfer hydrogenation of various substrates. These Ru complexes were found to be efficient catalysts for the reduction of nitriles and olefins. Heterocyclic compounds undergo transfer hydrogenation with good to moderate yields, affording examples of unusual hydrogenation of all-carbon-rings. Internal alkynes with bulky substituents show selective reduction to olefins with the unusual E–selectivity. Esters with strong electron-withdrawing groups can be reduced to the corresponding alcohols, if ethanol is used as the solvent. Possible mechanisms of hydrogenation and olefin isomerization are suggested on the basis of kinetic studies and labelling experiments.
- Alshakova, Iryna D.,Gabidullin, Bulat,Nikonov, Georgii I.
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p. 4860 - 4869
(2018/10/02)
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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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- Metathesis of renewable polyene feedstocks – Indirect evidences of the formation of catalytically active ruthenium allylidene species
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Cross-metathesis (CM) of conjugated polyenes, such as 1,6-diphenyl-1,3,5-hexatriene (1) and α-eleostearic acid methyl ester (2) with several olefins, including 1-hexene, dimethyl maleate and cis-stilbene as model compounds has been carried out using (1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene)-dichloro(o-isopropoxyphenylmethylene)ruthenium (Hoveyda-Grubbs 2nd generation, HG2) catalyst. The feasibility of these reactions is demonstrated by the observed high conversions and reasonable yields. Thus, regardless of the relatively low electron density, =CH–CH= conjugated units of molecules, including compound 2 as a sustainable, non-foodstuff source, can be utilized as building blocks for the synthesis of various value-added chemicals via olefin metathesis. DFT-studies and the product spectrum of the self-metathesis of 1,6-diphenyl-1,3,5-hexatriene suggest that a Ru η1-allylidene complex is the active species in the reaction.
- Kovács, Ervin,Sághy, Péter,Turczel, Gábor,Tóth, Imre,Lendvay, Gy?rgy,Domján, Attila,Anastas, Paul T.,Tuba, Róbert
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supporting information
p. 213 - 217
(2017/09/12)
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- Catalytic Synthesis of “Super” Linear Alkenyl Arenes Using an Easily Prepared Rh(I) Catalyst
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Linear alkyl benzenes (LAB) are global chemicals that are produced by acid-catalyzed reactions that involve the formation of carbocationic intermediates. One outcome of the acid-based catalysis is that 1-phenylalkanes cannot be produced. Herein, it is reported that [Rh(μ-OAc)(η2-C2H4)2]2 catalyzes production of 1-phenyl substituted alkene products via oxidative arene vinylation. Since C C bonds can be used for many chemical transformations, the formation of unsaturated products provides a potential advantage over current processes that produce saturated alkyl arenes. Conditions that provide up to a 10:1 linear:branched ratio have been achieved, and catalytic turnovers >1470 have been demonstrated. In addition, electron-deficient and electron-rich substituted benzenes are successfully alkylated. The Rh catalysis provides ortho:meta:para selectivity that is opposite to traditional acid-based catalysis.
- Webster-Gardiner, Michael S.,Chen, Junqi,Vaughan, Benjamin A.,McKeown, Bradley A.,Schinski, William,Gunnoe, T. Brent
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p. 5474 - 5480
(2017/04/27)
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- Arylation of hydrocarbons enabled by organosilicon reagents and weakly coordinating anions
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Over the past 80 years, phenyl cation intermediates have been implicated in a variety of C-H arylation reactions. Although these examples have inspired several theoretical and mechanistic studies, aryl cation equivalents have received limited attention in organic methodology. Their high-energy, promiscuous reactivity profiles have hampered applications in selective intermolecular processes. We report a reaction design that overcomes these challenges. Specifically, we found that b-silicon-stabilized aryl cation equivalents, generated via silylium-mediated fluoride activation, undergo insertion into sp3 and sp2 C-H bonds. This reaction manifold provides a framework for the catalytic arylation of hydrocarbons, including simple alkanes such as methane. This process uses low loadings of Earth-abundant initiators (1 to 5 mole percent) and occurs under mild conditions (30° to 100°C).
- Shao, Brian,Bagdasarian, Alex L.,Popov, Stasik,Nelson, Hosea M.
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- Terminal-Selective Functionalization of Alkyl Chains by Regioconvergent Cross-Coupling
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Hydrocarbons are still the most important precursors of functionalized organic molecules, which has stirred interest in the discovery of new C?H bond functionalization methods. We describe herein a new step-economical approach that enables C?C bonds to be constructed at the terminal position of linear alkanes. First, we show that secondary alkyl bromides can undergo in situ conversion into alkyl zinc bromides and regioconvergent Negishi coupling with aryl or alkenyl triflates. The use of a suitable phosphine ligand favoring Pd migration enabled the selective formation of the linear cross-coupling product. Subsequently, mixtures of secondary alkyl bromides were prepared from linear alkanes by standard bromination, and regioconvergent cross-coupling then provided access to the corresponding linear arylation product in only two steps.
- Dupuy, Stéphanie,Zhang, Ke-Feng,Goutierre, Anne-Sophie,Baudoin, Olivier
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p. 14793 - 14797
(2016/11/23)
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- A Pd-Cu2O nanocomposite as an effective synergistic catalyst for selective semi-hydrogenation of the terminal alkynes only
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A new type lead-free catalyst of a Pd-Cu2O nanocomposite was developed for highly selective semi-hydrogenation of alkynes. With unprecedented selectivity for the semi-hydrogenation of terminal alkynes to alkenes, we show for the first time that the catalyst only hydrogenated the terminal alkynes, i.e. did not hydrogenate the internal alkynes.
- Yang, Shuliang,Cao, Changyan,Peng, Li,Zhang, Jianling,Han, Buxing,Song, Weiguo
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supporting information
p. 3627 - 3630
(2016/03/05)
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- Low-temperature and low-pressure non-oxidative activation of methane for upgrading heavy oil
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It is highly desirable to upgrade viscous heavy oil, such as bitumen extracted from Canadian oil sand, to be transportable by pipeline. Conventionally, this is achieved by expensive catalytic hydrogenation under a hydrogen pressure of 15-20 MPa. In this s
- Guo, Aijun,Wu, Chongchong,He, Peng,Luan, Yingqi,Zhao, Lulu,Shan, Wenpo,Cheng, Wei,Song, Hua
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p. 1201 - 1213
(2016/02/27)
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- Synthesis of Ethers via Reaction of Carbanions and Monoperoxyacetals
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Although transfer of electrophilic alkoxyl ("RO+") from organic peroxides to organometallics offers a complement to traditional methods for etherification, application has been limited by constraints associated with peroxide reactivity and stability. We now demonstrate that readily prepared tetrahydropyranyl monoperoxyacetals react with sp3 and sp2 organolithium and organomagnesium reagents to furnish moderate to high yields of ethers. The method is successfully applied to the synthesis of alkyl, alkenyl, aryl, heteroaryl, and cyclopropyl ethers, mixed O,O-acetals, and S,S,O-orthoesters. In contrast to reactions of dialkyl and alkyl/silyl peroxides, the displacements of monoperoxyacetals provide no evidence for alkoxy radical intermediates. At the same time, the high yields observed for transfer of primary, secondary, or tertiary alkoxides, the latter involving attack on neopentyl oxygen, are inconsistent with an SN2 mechanism. Theoretical studies suggest a mechanism involving Lewis acid promoted insertion of organometallics into the O-O bond.
- Kyasa, ShivaKumar,Meier, Rebecca N.,Pardini, Ruth A.,Truttmann, Tristan K.,Kuwata, Keith T.,Dussault, Patrick H.
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p. 12100 - 12114
(2016/01/09)
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- Palladium on carbon-catalyzed aqueous transformation of primary alcohols to carboxylic acids based on dehydrogenation under mildly reduced pressure
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The catalytic dehydrogenation of alcohols to carbonyl products is a green sustainable oxidation with no production of waste except for hydrogen, which can be an energy source. Additionally, a reusable heterogeneous catalyst is valuable from the viewpoint of process chemistry and water is a green solvent. We have accomplished the palladium on carbon (Pd/C)-catalyzed dehydrogenation of primary alcohols to carboxylic acids in water under a mildly reduced pressure (800 hPa). The reduced pressure can be easily controlled by the vacuum controller of the rotary evaporator to remove the excess of generated hydrogen, which causes the reduction (reverse reaction) of aldehydes to alcohols (starting materials) and other undesirable side reactions. The present method is applicable to the reaction of various aliphatic and benzylic alcohols to the corresponding carboxylic acids, and the Pd/C could be reused at least 5 times.
- Sawama, Yoshinari,Morita, Kosuke,Asai, Shota,Kozawa, Masami,Tadokoro, Shinsuke,Nakajima, Junichi,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 1205 - 1210
(2015/04/22)
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- Iron-catalyzed olefin hydrogenation at 1 bar H2 with a FeCl3-LiAlH4 catalyst
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The scope and mechanism of a practical protocol for the iron-catalyzed hydrogenation of alkenes and alkynes at 1 bar H2 pressure were studied. The catalyst is formed from cheap chemicals (5 mol% FeCl3-LiAlH4, THF). A homogeneous mechanism operates at early stages of the reaction while active nanoparticles form upon ageing of the catalyst solution. This journal is
- Gieshoff, Tim N.,Villa, Matteo,Welther, Alice,Plois, Markus,Chakraborty, Uttam,Wolf, Robert,Jacobi Von Wangelin, Axel
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p. 1408 - 1413
(2015/03/18)
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- Rhodium-on-carbon catalyzed hydrogen scavenger- and oxidant-free dehydrogenation of alcohols in aqueous media
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The efficient and catalytic dehydrogenation of alcohols is a clean approach for preparing carbonyl compounds accompanied only by the generation of hydrogen gas. We have accomplished the heterogeneous rhodium-on-carbon catalyzed dehydrogenation of secondary, as well as primary, alcohols to the corresponding ketones and carboxylic acids in water under basic conditions. This journal is the Partner Organisations 2014.
- Sawama, Yoshinari,Morita, Kosuke,Yamada, Tsuyoshi,Nagata, Saori,Yabe, Yuki,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 3439 - 3443
(2014/07/08)
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- PtII-catalyzed hydrophenylation of α-olefins: Variation of linear/branched products as a function of ligand donor ability
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The PtII complexes [(xbpy)Pt(Ph)(THF)]+ (xbpy = 4,4′-X2-2,2′-bipyridyl; x = OMe (1a), tBu (1b), H (1c), Br (1d), CO2Et (1e) and NO2 (1f)] catalyze the formation of n-propylbenzene and cumene from benzene and propene. The catalysts are selective for branched products, and the cumene/n-propylbenzene ratio decreases with increasing donor ability of the xbpy ligand. DFT(D) calculations predict more favorable activation barriers for 1,2-insertion into the Pt-Ph bond to give branched products. The calculations indicate that 1,2-insertion of propene should be faster than 2,1-insertion for all Pt(II) catalysts studied, but they also indicate that cumene/n-propylbenzene selectivity is under Curtin-Hammett control.
- McKeown, Bradley A.,Prince, Bruce M.,Ramiro, Zoraida,Gunnoe, T. Brent,Cundari, Thomas R.
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p. 1607 - 1615
(2014/05/20)
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- Copper nanoparticle-catalyzed cross-coupling of alkyl halides with Grignard reagents
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A cross-coupling reaction between alkyl bromides and chlorides and various Grignard reagents was carried out in the presence of commercially available copper or copper oxide nanoparticles as a catalyst and an alkyne additive. The catalytic system shows high activity, a broad scope, and good functional group tolerance.
- Kim, Ju Hyun,Chung, Young Keun
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supporting information
p. 11101 - 11103
(2013/11/19)
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- Reactivities of mixed organozinc and mixed organocopper reagents: 9. Solvent dependence of group transfer selectivity in sp3C coupling and acylation of mixed diorganocuprates and diorganozincs
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The selectivity and/or reactivity of organyl group transfer of mixed diorganocuprates in their alkyl coupling in THF depends on N- or O-donor solvents as cosolvents. Selective n-Bu group transfer is observed in room temperature alkylation of Grignard reagent derived stoichiometric n-BuPhCuMgBr reagent in THF:cosolvent and solvation effects do not change the group transfer ability. However, in the alkylation of catalytic mixed cuprates derived from CuI catalyzed n-BuPh2ZnMgBr and n-Bu2PhZnMgBr, group transfer ability depends on the solvation effect and it can be controlled by using N- or O-donor solvents. In alkylation of CuI catalyzed mixed zincate n-BuPh 2ZnMgBr and also n-Bu2PhZnMgBr in THF at reflux temperature Ph group transfer takes place (n-Bu/Ph transfer ratio is 1:9 and 4:6, respectively) whereas n-Bu transfer increases in THF:NMP (1:1) resulting n-Bu/Ph transfer ratio of 4:6 and 8:2, respectively. Group transfer ability in allylation of n-BuPhZn seems not to be solvent dependent. The solvent effect on the group transfer ability has been found to be dependent also on the R 1 and R2 partnership in room temperature benzoylation of catalytic mixed cuprates, R1R2CuZnI, derived from CuI catalyzed R1R2Zn. These results are briefly discussed in terms of solvation of mixed diorganocuprate and diorganozinc reagents and provide useful information in their atom-economic alkyl, allyl and acyl coupling reactions.
- Erdik, Ender,Ero?lu, Fatma,Kalkan, Melike,Pekel, ?zgen ?mür,?zkan, Duygu,Serdar, Ebru Z.
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p. 235 - 241
(2013/10/01)
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- Catalytic synthesis of n-alkyl arenes through alkyl group cross-metathesis
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n-Alkyl arenes were prepared in a one-pot tandem dehydrogenation/olefin metathesis/hydrogenation sequence directly from alkanes and ethylbenzene. Excellent selectivity was observed when (tBuPCP)IrH2 was paired with tungsten monoaryloxide pyrrolide complexes such as W(NAr)(C 3H6)(pyr)(OHIPT) (1a) [Ar = 2,6-i-Pr2C 6H3; pyr = pyrrolide; OHIPT = 2,6-(2,4,6-i-Pr 3C6H2)2C6H3O]. Complex 1a was also especially active in n-octane self-metathesis, providing the highest product concentrations reported to date. The thermal stability of selected olefin metathesis catalysts allowed elevated temperatures and extended reaction times to be employed.
- Dobereiner, Graham E.,Yuan, Jian,Schrock, Richard R.,Goldman, Alan S.,Hackenberg, Jason D.
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supporting information
p. 12572 - 12575
(2013/09/23)
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- Iron-catalysed reduction of olefins using a borohydride reagent
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The iron-catalysed reduction of olefins has been achieved using a simple iron salt and sodium triethylborohydride. A wide range of mono- and trans-1,2-disubstituted alkenes have been reduced (91-100%) using 25 mol% iron(II) triflate, 1 mol% N-methyl-2-pyrrolidinone and 4 equivalents of sodium triethylborohydride. The reduction of alkynes to alkanes is also reported (up to 84%). Significantly, the reduction of trisubstituted alkenes has also been achieved (60-86%). Copyright
- Carter, Tom S.,Guiet, Lea,Frank, Dominik J.,West, James,Thomas, Stephen P.
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supporting information
p. 880 - 884
(2013/05/08)
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- A continuous process for the reductive deoxygenation of aromatic ketones over Cu30Cr10/γ-Al2O3
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A continuous process for reduction of aromatic ketones to the corresponding aromatic alkanes over Cu30Cr10/γ-Al 2O3 was established in a fixed-bed reactor. A series of aromatic ketones were examined, and all of the corresponding aromatic hydrocarbons were obtained in more than 95% yield. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and H 2-temperature programmed reduction. Cu0 is believed to be the active center of the catalyst. Cr was found to have an important effect on catalytic activity and stability. Springer Science+Business Media B.V. 2011.
- Ma, Jianchao,Liu, Shuai,Kong, Xiangjin,Fan, Xiaopeng,Yan, Xilong,Chen, Ligong
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p. 1341 - 1349
(2012/10/29)
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- Microwave-assisted silica-supported aluminum chloride-catalyzed Friedel-Crafts alkylation
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Microwave irradiation is a popular method in organic synthesis to achieve high yields in shorter reaction times. This decreases total 'man-hours' in a synthetic setting. Another technique used in organic chemistry to decrease manual manipulations, is solid support reagents. The benefits of this approach is that upon completion of a reaction, a simple filtration can be performed which expedites the work-up and also produces less organic waste. Friedel-Crafts alkylation has been explored using microwave chemistry as well as with solid-supported reagents. In comparison with traditional heating, as well as with AlCl3, superior yields were observed with silica-gel bound aluminum chloride (Si-AlClx) when microwave irradiated for only 5 min.
- Zupp, Laurine R.,Campanella, Veronica L.,Rudzinski, Diandra M.,Beland, Franois,Priefer, Ronny
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p. 5343 - 5346
(2012/10/30)
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- Higher-order zincates as transmetalators in alkyl-alkyl Negishi cross-coupling
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Negishi revisited: Higher-order alkyl zincates have been subjected to Negishi coupling with alkyl bromides. For the first time, coupling takes place in straight THF, i.e., without a salt additive and a high dielectric co-solvent. This provides evidence that it is the higher-order zincate that undergoes transmetalation to Pd, and not mono-anionic zincates or any of the other species present in the Schlenk equilibrium. Copyright
- McCann, Lucas C.,Hunter, Howard N.,Clyburne, Jason A. C.,Organ, Michael G.
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supporting information; scheme or table
p. 7024 - 7027
(2012/10/18)
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- Iron-catalysed, hydride-mediated reductive cross-coupling of vinyl halides and Grignard reagents
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An iron-catalysed, hydride-mediated reductive cross-coupling reaction has been developed for the preparation of alkanes. Using a bench-stable iron(ii) pre-catalyst, reductive cross-coupling of vinyl iodides, bromides and chlorides with aryl- and alkyl Grignard reagents successfully gave the products of formal sp3-sp3 cross-coupling reactions.
- Le Bailly, Bryden A. F.,Greenhalgh, Mark D.,Thomas, Stephen P.
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supporting information; experimental part
p. 1580 - 1582
(2012/03/26)
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- DEHYDROGENATION OF CYCLOHEXANONE TO PRODUCE PHENOL
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In a process for the dehydrogenation of cyclohexanone to produce phenol, a feed comprising cyclohexanone is contacted with a dehydrogenation catalyst under dehydrogenation conditions comprising a temperature of less than 4000C and a pressure of less than 690 kPa, gauge, such 0.1 to 50 wt% of the cyclohexanone in said feed is converted to phenol and the dehydrogenation product contains less than 100 ppm by weight of alkylbenzenes.
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Page/Page column 22; 25
(2011/09/14)
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- Reactivity of mixed organozinc and mixed organocopper reagents: 6. Nickel-catalyzed coupling of methylarylzincs with primary alkyl halides; An atom-economic aryl-alkyl coupling
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A nickel-catalyzed process for the cross-coupling of mixed arylzincs and primary alkyl halides has been developed. The reaction of a methylarylzinc with a primary alkyl halide in THF in the presence of NiCl2/PPh 3 takes place with selective aryl transfer at room temperature in moderate yields. This protocol provides an atom-economic alternative to aryl-primary alkyl coupling using diarylzincs.
- Pekel, ?zgen ?mür,Erdik, Ender
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experimental part
p. 7087 - 7090
(2012/01/06)
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- Cuprous-catalyzed cross-coupling reaction of grignard reagents with alkyl halides
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For the first time in the presence of a catalytic amount of cuprous iodide, alkyl bromide reacted with aryl magnesium bromide (Grignard reagent) to obtain the cross-coupling product in good yields. The conditions of the cross-coupling reaction were studied. The suitable amount of catalyst, reaction temperature and time are 2 % mol (based on alkyl halide), 67 °C (reflux), 6 h, respectively. Under the optimal conditions, the yields of the cross-coupling could reach up to 90 %. Moreover, Grignard reagent with an electron-rich group reacted rapidly and with an electron-withdrawing group reacted sluggishly.
- Dai,Zhang,Zhang,Wei,Yang
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experimental part
p. 4087 - 4089
(2012/01/04)
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- Photo-driven anti-Markovnikov alkyne hydration in self-assembled hollow complexes
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Under UV-light irradiation, the anti-Markovnikov hydration of internal arylalkynes proceeds in the cavity of an electron-deficient coordination cage to give benzyl ketones; the reaction is triggered by cage-mediated, photo-induced electron transfer from the alkynes to the cage.
- Murase, Takashi,Takezawa, Hiroki,Fujita, Makoto
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supporting information; scheme or table
p. 10960 - 10962
(2011/11/13)
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- Selective palladium-loaded MIL-101 catalysts
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Palladium nanoparticles (NPs) of different mean particle size have been synthesized in the host structure of the porous coordination polymer (or metal-organic framework: MOF) MIL-101. The metal-organic chemical vapor deposition method was used to load MIL-101 with the Pd precursor complex [(η5-C5H5)Pd(η3-C 3H5)]. Loadings higher than 50 wt.% could be accomplished. Reduction of the Pd precursor complex with H2 gave rise to Pd NPs inside the MIL-101 (Pd@MIL-101). The reduction conditions, especially the temperature, allows us to make size-conform (size of the Pd NPs correlates with the size of the cavities of the host structure of MIL-101) and undersized Pd NPs. The Pd@MIL-101 samples were characterized by X-ray diffraction, IR spectroscopy, Brauner-Emmett-Teller (BET) analysis, elemental analysis, and transmission electron microscopy (TEM). Catalytic studies, hydrogenation of ketones, were performed with selected Pd@MIL-101 catalysts. Activity, selectivity, and recyclability of the catalyst family are discussed.
- Hermannsdoerfer, Justus,Kempe, Rhett
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experimental part
p. 8071 - 8077
(2011/09/12)
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- Catalytic coupling of N-benzylic sulfonamides with silylated nucleophiles at room temperature
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In the presence of 2-10 mol% of Tf2NH, a range of N-benzylic sulfonamides smoothly react with allylic, propargylic, benzylic, or hydrido silanes at room temperature via sp3 carbon-nitrogen bond cleavage to afford structurally diverse products in moderate to excellent yields and with high chemo- and regioselectivity.
- Yang, Bai-Ling,Tian, Shi-Kai
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supporting information; experimental part
p. 6180 - 6182
(2010/10/20)
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- Air-stable secondary phosphine oxide or chloride (Pre)ligands for cross-couplings of unactivated alkyl chlorides
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In situ generated and crystallographically well-defined, isolated palladium complexes derived from seven novel air-stable secondary phosphine oxides or chlorides enabled challenging Kumada-Corriu cross-couplings of unactivated alkyl chlorides bearing β-hy
- Ackermann, Lutz,Kapdi, Anant R.,Schulzke, Carola
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scheme or table
p. 2298 - 2301
(2010/08/05)
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- A selective Ru-catalyzed semireduction of alkynes to Z olefins under transfer-hydrogenation conditions
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By using a readily available, air- and moisture-stable dihydrido-Ru complex, a variety of Z olefins are accessible under transfer-hydrogenation conditions with formic acid as the hydrogen source in excellent yields and Z/E selectivities. A discerning transformation: Z-Configured C=C bonds are stereoselectively formed from alkynes in the presence of a Ru catalyst with formic acid as the sole H2 source at room temperature (see scheme). A variety of functional groups are compatible with this novel procedure. Operational simplicity and the lack of overreduction products are characteristics for this unprecedented process.
- Belger, Christian,Neisius, N. Matthias,Plietker, Bernd
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supporting information; experimental part
p. 12214 - 12220
(2011/03/17)
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- Rhodium-catalyzed reductive decyanation of nitriles using hydrosilane as a reducing agent: Scope, mechanism and synthetic application
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A rhodium-catalyzed reductive cleavage reaction of carbon-cyano bonds is developed using hydrosilane as a mild reducing agent. A wide range of nitriles, including aryl, benzyl, and p-hydrogen containing alkyl cyanides are applicable to this decyanation reaction. The method is also applicable to organic synthesis, in which benzyl cyanide is used as a benzyl anion equivalent and a cyano group functions as a removable ortho-directing group.
- Tobisu, Mamoru,Nakamura, Ryo,Kita, Yusuke,Chatani, Naoto
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body text
p. 582 - 587
(2010/08/07)
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- Liquid-crystalline polymorphism of symmetrical azobananas: Bis(4-(4-alkylphenyl)azophenyl) 2-nitroisophtalates
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In this paper we present a series of novel compounds, bis(4-(4-alkylphenyl) azophenyl) 2-nitroisophtalates, which exhibit nematic and banana-type liquidcrystalline phases. The alkyl chain length varies from 1 to 18 carbons. The first ten members of this series exhibit nematic phase. The last eleven compounds exhibit banana-type liquid crystalline phases. The propyl and pentyl derivatives have extra second type of banana mesophase. Copyright Taylor & Francis Group, LLC.
- Zygadlo,Dardas,Nowicka,Hofmann,Galewski
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scheme or table
p. 283 - 291
(2011/08/02)
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- Synergistic effects of alkali metals in the alkylation of naphthalene and toluene with ethene in the ArH-alkali metal systems in THF (ArH - naphthalene, phenanthrene)
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The use of mixtures of metallic lithium and sodium in the naphthalene-alkali metal systems in THF leads to a synergistic acceleration of the naphthalene alkylation with ethene at room temperature and atmospheric pressure. The greatest synergistic effect is observed at a Li:Na molar ratio of 2:1. Under these conditions, the overall conversion of naphthalene into alkylation products (linear 1-alkylnaphthalenes and their dihydro derivatives) attains 88% after 24 h (a (Li + Na):C10H8 ratio is 2:1). The use of mixtures of metallic lithium and potassium in such systems results, however, in a synergistic retardation of the alkylation process. The strongest retarding effect is observed at a Li:K molar ratio of 1:1. The efficiency of the toluene alkylation with ethene in the naphthalene-alkali metal systems in THF is also increased on the replacement of lithium or sodium by their mixtures. The best results are obtained at a Li:Na molar ratio of 1:3. With this Li:Na ratio, toluene is almost quantitatively converted into linear and α-branched higher monoalkylbenzenes (24 h, (Li + Na):C10H8 = 2:1). The rate of the naphthalene alkylation with ethene in the presence of toluene is enhanced as well on an introduction of mixtures of lithium and sodium into the system. However the maximum of the activity is shifted here towards higher lithium content (Li:Na = 1:1). A similar synergistic effect of lithium and sodium was found on studying the toluene alkylation with ethene in the phenanthrene-Li-Na systems in THF (a (Li + Na):phenanthrene ratio is 3:1). An addition of potassium to sodium also considerably increases the efficiency of the toluene and naphthalene alkylation with ethene in the naphthalene-based systems. The possible mechanism of the alkali metal synergism in the above-mentioned alkylation reactions is discussed.
- Rummel,Yunusov,Kalyuzhnaya,Shur
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experimental part
p. 1467 - 1472
(2009/09/06)
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- Activation of C-H bonds of hydrocarbons by the ArH-alkali metal systems in THF (ArH - naphthalene, biphenyl, anthracene, phenanthrene, trans-stilbene, pyrene). Alkylation of naphthalene and toluene with ethene
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Systems based on naphthalene and alkali metals (Li, Na, K) in THF are able to induce the alkylation of naphthalene with ethene at room temperature and atmospheric pressure. The highest activity in this reaction is exhibited by the naphthalene-potassium system which converts naphthalene into 1-ethylnaphthalene (1) and small amounts of two isomeric dihydro derivatives of 1 in a yield of 85% (24 h, K:C10H8 = 2:1). The same alkylation products are formed when metallic sodium is used instead of potassium. The interaction of ethene with the naphthalene-lithium system (24 h, Li:C10H8 = 2:1) affords 1 together with 1-n-butylnaphthalene (4), 1-n-hexylnaphthalene (5), 1-n-oktylnaphthalene (6) and dihydro derivatives of 5 and 6 in a total yield of 60%. Alkylation of toluene with ethene in the naphthalene-alkali metal systems leads to the formation of higher monoalkylbenzenes. The greatest toluene conversion (48%, 24 h) is observed on using the lithium-containing system (Li:C10H8 = 2:1), in the presence of which a mixture of n-propylbenzene (11), n-pentylbenzene (12), 3-phenylpentane (13) and 3-phenylheptane (14) is produced from ethene and toluene. On the replacement of lithium by sodium or potassium, only 11 and 13 are obtained. A treatment of biphenyl, phenanthrene, trans-stilbene, pyrene and anthracene with alkali metals in THF also gives systems capable of catalyzing the alkylation of toluene with ethene at 22 °C. Of particularly active is the stilbene-lithium system (Li:stilbene = 3:1) which converts toluene into a mixture of 11-14, n-heptylbenzene and 5-phenylnonane in a yield of 58%. In all cases, the rate of the alkylation considerably increases in the presence of the solid phase of alkali metal. The mechanism of the reactions found is discussed.
- Rummel,Ilatovskaya,Yunusov,Kalyuzhnaya,Shur
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experimental part
p. 1459 - 1466
(2009/09/06)
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- Reactivity of mixed organozinc and mixed organocopper reagents. Part 4: A kinetic study of group transfer selectivity in C-C coupling of mixed diorganocuprates
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The competitive rate data and Taft relationships for the coupling of bromomagnesium n-butyl (substituted phenyl) cuprates with alkyl bromides show that selective n-butyl transfer can be explained by an oxidative addition mechanism. Taft reaction constants
- Erdik, Ender,Oezkan, Duygu
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experimental part
p. 1148 - 1154
(2010/07/13)
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- Iron-catalyzed alkylations of aromatic Grignard reagents
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(Chemical Equation Presented) Any old iron: Two efficient iron-catalyzed cross-coupling reactions between aryl Grignard reagents and alkyl bromides were developed that are suitable for large-scale applications. The first procedure uses iron acetylacetonate and involves a cooperative effect between the two ligands N,N,N′,N′-tetramethylethylenediamine (TMEDA) and hexamethylenetetraamine (HMTA), while the second procedure uses [(FeCl 3)2(tmeda)3] as catalyst. 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
- Cahiez, Gerard,Habiak, Vanessa,Duplais, Christophe,Moyeux, Alban
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p. 4364 - 4366
(2008/03/12)
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- Borrowing hydrogen: Indirect "Wittig" olefination for the formation of C-C bonds from alcohols
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The successful development of an indirect three-step domino sequence for the formation of C-C bonds from alcohol substrates is described. An iridium-catalysed dehydrogenation of alcohol 1 affords the intermediate aldehyde 2. The desired C-C bond can then be formed by a facile Wittig olefination, yielding the intermediate alkene 3. In the final step the alkene is hydrogenated to afford the indirect Wittig product, the alkane 4. The key to this process is the concept of borrowing hydrogen; hydrogen removed in the initial dehydrogenation step is simply borrowed by the iridium catalyst. Functioning as a hydrogen reservoir, the catalyst facilitates C-C bond formation before subsequently returning the borrowed hydrogen in the final step. Herein we present full details of our examination into both the substrate and reaction scope and the limitations of the catalytic cycle. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Black, Phillip J.,Edwards, Michael G.,Williams, Jonathan M. J.
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p. 4367 - 4378
(2007/10/03)
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- Unique and convenient use of Raney nickel for the reduction of aryl bromides, benzyl alcohols, benzyl ethers, and benzylamines in an acidic medium
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A simple and convenient method for laboratory-scale reduction using Raney nickel is described. The reaction was achieved by the inclusion of sulfuric acid to a mixture of a substrate and Raney nickel. Using this method, several aryl bromides, benzyl alcohols, benzyl ethers, and benzylamines were cleaved at the carbon-bromine bond or at the benzylic position to afford corresponding hydrogenated products in good yields without the use of compressed hydrogen gas and without requiring any special apparatus.
- Okimoto, Mitsuhiro,Takahashi, Yukio,Nagata, Yuji,Satoh, Masanori,Sueda, Satoru,Yamashina, Tsunaki
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p. 1405 - 1406
(2007/10/03)
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- Palladium-catalyzed decarboxylation and decarbonylation under hydrothermal conditions: Decarboxylative deuteration
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Equation presented. Decarboxylation of free carboxylic acid was performed by Pd/C catalyst under hydrothermal water (250°C/4 MPa). Under the hydrothermal conditions of deuterium oxide, decarbonylative deuteration was observed to give fully deuterated hydrocarbons from carboxylic acids or aldehydes.
- Matsubara, Seijiro,Yokota, Yutaka,Oshima, Koichiro
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p. 2071 - 2073
(2007/10/03)
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- Reduction of Carbonyl Function to a Methyl Group
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A direct exhaustive reduction of aliphatic carbonyl functions (aldehydes, acyl chlorides, esters and carboxylic acids) to a methyl group by triethylsilane (Et3SiH) in the presence of catalytic amount of tris(pentafluorophenyl)borane [B(C6F5)3] is described. Aromatic carbonyl functions could undergo partial reduction to the corresponding TES-protected benzylic alcohols.
- Bajracharya, Gan B.,Nogami, Tsutomu,Jin, Tienan,Matsuda, Kumiko,Gevorgyan, Vladimir,Yamamoto, Yoshinori
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p. 308 - 311
(2007/10/03)
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