- Solvent-dependent substrate reduction by {Sm[N(SiMe3)2]2(THF)2}. An alternative approach for accelerating the rate of substrate reduction by Sm(II)
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The impact of solvent on electron transfer from Sm(II) to substrates was measured by determining the rate of reduction of 1-bromo-, 1-chlorododecane, and 3-pentanone in THF and hexanes using the highly soluble reductant {Sm[N(SiMe3)2]2(THF)2}. Rates were found to be 3 orders of magnitude faster in hexanes than THF, and reductions of alkyl halides were inverse first order in THF. These findings show the solvent milieu signifi cantly impacts the rate of substrate reduction, a consideration that may prove useful in synthesis. (Chemical Equation Presented).
- Chciuk, Tesia V.,Hilmersson, G?ran,Flowers, Robert A.
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- Development of radical reactions with zirconocene complexes as electron transfer reagents
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Bis(cyclopentadienyl)zirconium chloride hydride (Schwartz reagent) proved to be an efficient radical chain carrier for radical reduction of organic halides. Treatment of 1-bromoadamantane with Cp2Zr(H)Cl in THF at 25°C in the presence of triethylborane furnished adamantane quantitatively. Radical cyclization of 2-haloalkyl allyl ethers afforded five-membered products under the same reaction conditions. Reduction with Cp2Zr(H)Cl generated in situ from Cp2ZrCl2 and sodium bis(2-methoxyethoxy)aluminium hydride (Red-Al) also proceeded smoothly. Moreover, the reduction could function by using a catalytic amount of Cp 2ZrCl2. A zirconocene-olefin complex also induced reductive radical cyclization of 2-haloalkyl allyl ethers in THF. This complex served as a single electron transfer reagent to promote the radical cyclization. Furthermore, the cyclization reaction in DME afforded 3- tetrahydrofuranylmethylzirconium efficiently.
- Fujita, Kazuya,Yorimitsu, Hideki,Oshima, Koichiro
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- Alkylidene fluorene liquid crystalline semiconducting polymers for organic field effect transistor devices
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Organic electronic devices comprising arrays of organic field effect transistors (OFETs) are expected to create a range of novel applications for which the ability to be fabricated in large areas, on flexible substrates, with nonconventional shapes, and at low cost are key enabling factors. To improve the electrical performance of such devices, new solution processable organic semiconductors are required with high charge carrier mobilities and environmental stability. This work describes the molecular design of a p-type charge transport liquid crystalline polymer, in an attempt to control the factors responsible for both mobility and stability. Molecules were designed that were able to exhibit closely packed, π stacked morphologies, which can result in efficient intermolecular charge hopping and hence high mobility. Molecular manipulation of the conjugated π electron system was required to optimize the HOMO energy level, to both resist oxidation and be able to readily accept holes from a source electrode.
- Heeney, Martin,Bailey, Clare,Giles, Mark,Shkunov, Maxim,Sparrowe, David,Tierney, Steve,Zhang, Weimin,McCulloch, Iain
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- Prominent hydrogenation catalysis of a PVP-stabilized Au34 superatom provided by doping a single Rh atom
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A single rhodium atom was precisely doped into a gold cluster Au34 stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP) as revealed by mass spectrometry. The Rh-atom-doped Au:PVP exhibited remarkable catalytic activity for hydrogenation reactions of olefins, which was much higher than that of recently reported Pd-atom-doped Au:PVP.
- Hasegawa, Shingo,Takano, Shinjiro,Yamazoe, Seiji,Tsukuda, Tatsuya
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- DISSOLVING METAL REDUCTION WITH CROWN ETHER----- REDUCTIVE DECYANATION
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Toluene radical anion generated from potassium metal/dicyclohexano-18-crown-6/toluene system has been proved to be highly effective for reductive decyanation reaction of primary, secondary and tertiary cyanides.
- Ohsawa, Tomihiko,Kobayashi, Takao,Mizuguchi, Yuko
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- Fatty methyl ester hydrogenation to fatty alcohol Part II: Process issues
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Fatty alcohols are produced by hydrogenating fatty methyl esters in slurry phase in the presence of copper chromite catalyst at temperatures of 250-300 °C and hydrogen pressures of 2000-3000 psi. The fatty methyl ester, catalyst, and hydrogen are fed to the reactor cocurrently. The product slurry is passed through gas-liquid separators and then through a continuous filtration system for removal of the catalyst. A portion of the used catalyst in crude alcohol is recycled to the hydrogenator. The overall efficiency of the process depends upon the intrinsic activity, life, and filterability of the catalyst. The fatty alcohol producer therefore requires a catalyst with high activity, long life, and good separation properties. The main goal of the present laboratory investigation was to develop a superior copper chromite catalyst for the slurry-phase process. Two copper chromite catalysts, prepared by different procedures, were tested for methyl ester hydrogenolysis activity, reusability, and filtration characteristics. The reaction was carried out in a batch autoclave at 280 °C and 2000-3000 psi hydrogen pressure. The reaction rates were calculated by assuming a kinetic mechanism that was first-order in methyl ester concentration. The catalyst with the narrower particle size distribution was 30% more active, filtered faster, and maintained activity for several more uses than the catalyst with the broader particle size distribution. X-ray photoelectron spectroscopy data showed higher surface copper concentrations for the former catalyst.
- Rieke,Thakur,Roberts,White
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- Spurring radical reactions of organic halides with tin hydride and TTMSS using microreactors
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Tributyltin hydride-mediated radical reactions of organic halides were successfully carried out in a continuous flow system using a microreactor. The reactions proceeded within a very short period of time, coupled with quickly decomposing radical initiators such as V-65 and V-70. The continuous flow reaction system was applied to gram scale synthesis of a key intermediate for furofuran lignans.
- Fukuyama, Takahide,Kobayashi, Masahide,Rahman, Md Taifur,Kamata, Naoya,Ryu, Llhyong
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- Conversion of biomass-derived fatty acids and derivatives into hydrocarbons using a metal-free hydrodeoxygenation process
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A metal-free hydrodeoxygenation process was developed for the production of hydrocarbons from biomass-derived fatty acids and derivatives. Biomass-derived fatty acids and derivatives were converted to alkanes and alkenes under mild reaction conditions. Furthermore, this catalytic system can also be applied to convert real biomass with satisfactory results.
- Li, Xing-Yu,Shang, Rui,Fu, Ming-Chen,Fu, Yao
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- Interactions of alkoxides. XVII. Properties of complex bases from organolithium compounds and various sodium alkoxides affected by the structure and concentration of the alkoxide
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In reactions of a substrate with complex bases (CB) prepared from organolithium compounds and heavier alkalimetal alkoxides the reaction rates and relative product yields depend on the structure and concentration of the CB components.For the model reaction of C6 with alkyl bromides, changes in the identity and concentration of the alkoxide reduced reaction half-times by as much as three orders of magnitude and higher yields of the product of Wurtz coupling were obtained.Sodium 3-methyl-pentoxide-3 was found to be considerably more effective than sodium t-butoxide.
- Lochmann, L.
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- Polycyclic aromatic compounds-mediated electrochemical reduction of alkyl mesylates
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Electrochemical reduction of alkyl mesylates was successfully carried out by using an undivided cell equipped with a Pt cathode and an Mg anode in the presence of biphenyl and t-BuOH. The reaction could proceed efficiently under mild conditions to give the corresponding alkanes in moderate to good yields. This procedure could also be applicable to chemoselective reduction of mesylates having functional groups such as epoxide, olefin, acetal, hydroxy, or cyano groups. Copyright
- Senboku, Hisanori,Takahashi, Megumi,Fukuhara, Tsuyoshi,Hara, Shoji
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- Enhanced Reducing Ability by the Combination of SmI2 and Sm Metal in the Reduction of Alkyl Halides
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Reduction of alkyl bromides and iodides easily takes place under mild conditions by the use of a reaction system combining SmI2 with Sm metal.The reducing ability of this Sm/SmI2 mixed reagent is superior to that of SmI2 or Sm metal used independently.
- Ogawa, Akiya,Nanke, Taizoh,Takami, Noriaki,Sumino, Yukihito,Ryu, Ilhyong,Sonoda, Noboru
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- Efficient electrosynthesis of SmCl2, SmBr2, and Sm(OTf)2 from a "Sacrificial" Samarium anode: Effect of nBu4NPF6 on the reactivity
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Divalent samarium complexes SmX2 (X = Cl, Br, OTf) have been efficiently synthesized in one electrochemical step using a sacrificial samarium anode in the presence of tetrabutylammonium salts nBu4NX (X = Br, Cl, OTf) as samarium ligand sources free of any metal additives. All complexes were analyzed by electrochemical measurements and UV-vis spectroscopy in tetrahydrofuran under an inert atmosphere. The oxidation potentials of SmCl2 and SmBr2 in THF vs SCE are more negative than that of SmI2, while the oxidation potential of Sm(OTf)2 was found to be less negative, confirming that the ligand nature is important in samarium redox chemistry. The electrogenerated SmX2 species were evaluated in the reduction of 1-chlorododecane in order to correlate their redox potentials with their reactivities. We discovered that ammonium salts used for the electrosynthesis of these complexes significantly increase their reactivity regardless of their redox potentials. (Figure Presented)
- Sun, Linhao,Mellah, Mohamed
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- N-Ethylpiperidine Hypophosphite Mediated Intermolecular Radical Carbon-Carbon Bond Forming Reaction in Water
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N-Ethylpiperidine hypophosphite mediated radical addition reactions to electron deficient alkenes in aqueous media have been developed. The reactions afford high isolated yields of addition products without using a large excess of alkenes.
- Jang, Doo Ok,Cho, Dae Hyan
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- Thermoregulated phase-transfer rhodium nanoparticle catalyst for hydrogenation in an aqueous/organic biphasic system
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A simple, effective and reversible aqueous/organic phase-transfer method for rhodium nanoparticles was developed on the basis of the cloud point (Cp) of thermoregulated ligand. The rhodium nanoparticles stabilized by thermoregulated ligand Ph2P(CH2CH2O)nCH3 (n = 16) could transfer from aqueous phase to 1-butanol phase and vice versa by means of changing temperature. This thermoregulated phase-transfer rhodium nanoparticle catalyst evaluated in the hydrogenation of olefins in an aqueous/1-butanol biphasic system exhibited high activity and stability.
- Li, Kaoxue,Wang, Yanhua,Jiang, Jingyang,Jin, Zilin
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- The Reductive Coupling of Organic Halide Using Hydrazine and a Palladium Amalgam Catalyst. I. The Preparation of Biaryls
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Iodoarenes could be converted to the corresponding biaryls in high yields by use of a catalytic amount of a palladium amalgam in place of a palladium-calcium carbonate catalyst in Busch's reaction.The 2,3'-isomer content in the bitolyls obtained by the homo-coupling of o-iodotoluene was 15percent when palladium was used, while it was 1percent when a palladium amalgam was used, and the latter was re-usable.The present method is further applicable to some iodoalkanes.
- Nakajima, Riichiro,Shintani, Yuji,Hara, Tadashi
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- CATALYTIC HYDROGENATION OF ALKYNES TO CIS-ALKENES ON A MODIFIED BORON-NICKEL CATALYST
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Hydrogenation of alkynes from decyne and dodecyne (C10-C12) with the triple bond at C3, C4, C5, and C6 led to the corresponding alkenes on a boron-nickel catalyst modified by a 1-phenyl-2,3-dimethyl-4-amino-5-pyrazolone (4-aminoantipyrene).The stereospecificity for formation of the cis-alkenes was 95-98percent.
- Siimer, E. Kh.,Petrova, S. S.
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- Polar effects in free-radical reactions. The paradox of reduction of alkyl iodides and reductive alkylation of alkenes by strong oxidants (t-BuOOH, Pb(OAc)4)
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Alkanes are directly iodinated by perfluoroalkyl iodides by a free-radical chain process initiated by t-BuOOH in acetic acid solution. The initially formed iodoalkanes are reduced back to alkanes by excess t-BuOOH; the rate constant for hydrogen abstraction from t-BuOOH by a primary alkyl radical has been roughly evaluated to be ~104 M-1 s-1. Two new procedures for the reductive alkylation of alkenes by t-BuOOH and Pb(OAc)4 are reported. The importance of the polar effects and the rate constants of the key elementary steps involved in these processes is discussed.
- Minisci, Francesco,Fontana, Francesca,Recupero, Francesco,Bravo, Anna,Pagano, Elvira,Rinaldi, Cinzia,Di Luca, Marco,Grossi, Flavia,Bjorsvik, Hans-Rene
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- Novel reducing properties of a series of lanthanoid metals in the presence of SmI2
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The reduction of dodecyl iodide, as model compound, with a series of lanthanoid (Ln) metals in the presence of catalytic amounts of samarium diiodide (SmI2) has been investigated in detail. The reducing activity of SmI2/Ln and the kinds of reduced products were found to be dependent on the individual Ln, but not on SmI2.
- Tomisaka, Yuri,Yoshimura, Aya,Nomoto, Akihiro,Sonoda, Motohiro,Ogawa, Akiya
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- Cross-coupling of Grignard reagents with alkyl halides or tosylates by the use of nickel or palladium containing perovskite
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Nickel and palladium-containing perovskites, LaFe0.8Ni 0.2O3 (LFNO) and LaFe0.95Pd 0.05O3 (LFPO), could be employed as effective catalyst sources for the cross-coupling of nonactivated alkyl halides and tosylates with Grignard reagents in the presence of conjugated dienes. The reaction proceeded efficiently at room temperature or below using only ca. 1 mol % of catalysts with respect to Ni or Pd and the perovskites were reused without considerable loss of activity.
- Singh, Surya Prakash,Iwasaki, Takanori,Terao, Jun,Kambe, Nobuaki
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- Synthetic radical reactions using dibutylchlorogermane and dibutylethoxygermane as radical mediators
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In the presence of Et3B as radical initiator, dibutylchlorogermane (1a) and dibutylethoxygermane (1b) reacted with bromo- and iodoalkanes at room temperature to give the corresponding alkanes in high yields. Hydrogermane 1a was more reactive than 1b. However, 1b worked as a better radical mediator in intermolecular radical addition of haloalkanes to electron-deficient alkenes. Georg Thieme Verlag Stuttgart.
- Miura, Katsukiyo,Ootsuka, Kazunori,Hosomi, Akira
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- Expanding the scope of trialkylborane/water-mediated radical reactions
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(Formula Presented) The dehalogenation of alkyl iodides, as well as the chemoselective deoxygenation of a secondary alcohol in the presence of various alkyl and aryl halides, can be accomplished employing a trialkylborane/air/water system.
- Medeiros, Matthew R.,Schacherer, Laura N.,Spiegel, David A.,Wood, John L.
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- From Furfural to Fuel: Synthesis of Furoins by Organocatalysis and their Hydrodeoxygenation by Cascade Catalysis
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The synthesis of furoins from biomass-derived furfural and 2-methylfurfural is demonstrated in high yields in green and renewable solvents using N-heterocyclic carbene organocatalysts. The resulting furoin molecules are used as precursors for fuels using cascade catalysis, first by using Pd/C with acidic co-catalysts under very mild conditions to yield oxygenated C12molecules. Two main products were formed, which we identified as 1,2-bis(5-methyltetrahydrofuran-2-yl)ethane and 1-(5-methyltetrahydrofuran-2-yl)heptanol. The use of a Pd/Zeolite-β catalyst under more extreme conditions resulted in the complete hydrodeoxygenation of 5,5′-dimethylfuroin to dodecanes in high yields (76 %) and exceptional selectivity (94 %) for n-dodecane.
- Wegenhart, Benjamin L.,Yang, Linan,Kwan, Soon Cheong,Harris, Remi,Kentt?maa, Hilkka I.,Abu-Omar, Mahdi M.
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- Thiol-catalysed Radical-chain Reduction of Organic Halides by Hexabutylditin in the Presence of Malonic Acid
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In the presence of a thiol catalyst and a suitable initiator, a mixture of hexabutylditin and malonic acid brings about protodehalogenation of organic bromides and iodides by a radical-chain mechanism.
- Kim, Kyoung-Mahn,Roberts, Brian P.
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- Proton-Coupled Electron Transfer in the Reduction of Arenes by SmI2-Water Complexes
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The presence of water has a significant impact on the reduction of substrates by SmI2. The reactivity of the Sm(II)-water reducing system and the relationship between sequential or concerted electron-transfer, proton-transfer is not well understood. In this work, we demonstrate that the reduction of an arene by SmI2-water proceeds through an initial proton-coupled electron transfer. The use of thermochemical data available in the literature shows that upon coordination of water to Sm(II) in THF, significant weakening of the O-H bond occurs. The derived value of nearly 73 kcal/mol for the decrease in the bond dissociation energy of the O-H bond in the Sm(II)-water complex is the largest reported to date for low-valent reductants containing bound water.
- Chciuk, Tesia V.,Flowers, Robert A.
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- Hydrodeoxygenation of fatty acids and triglycerides by Pt-loaded Nb2O5catalysts
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Platinum nanoparticles loaded onto various supports have been studied for the selective hydrogenation of lauric acid to n-dodecane. The activity depends on the support material and pre-reduction temperature. Pt/Nb2O5reduced at 300 °C gives the highest activity. Pt/Nb2O5shows higher activity than various Nb2O5-supported transition metals (Ir, Re, Ru, Pd, Cu, Ni). Under solvent-free conditions Pt/Nb2O5is effective for the hydrodeoxygenation of lauric, capric, palmitic, myristic, oleic, and stearic acids under 8 bar H2at 180-250 °C, which gives high yields (88-100%) of linear alkanes with the same chain length as the starting compound. Tristearin is also converted to give 93% yield of n-octadecane. Pt/Nb2O5shows more than 60 times higher turnover number (TON) than the previously reported catalysts for the hydrogenation of stearic acid to n-octadecane. Mechanistic study shows a consecutive reaction pathway in which lauric acid is hydrogenated to 1-dodecanol, which undergoes esterification with lauric acid as well as hydrogenation to n-dodecane. The ester undergoes hydrogenolysis to give the alcohol, which is hydrogenated to the alkane. Infrared (IR) study of acetic acid adsorption on Nb2O5indicates that Lewis acid-base interaction of Nb cation and carbonyl oxygen, which suggests a possible role of Nb2O5as an activation site of carbonyl groups during hydrodeoxygenation. This journal is
- Kon, Kenichi,Onodera, Wataru,Takakusagi, Satoru,Shimizu, Ken-Ichi
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- Novel aqueous/organic biphasic system for thermoregulated phase-transfer catalysis with rhodium nanoparticles
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An aqueous/1-pentanol biphasic system was developed for thermoregulated phase-transfer catalysis with rhodium nanoparticles in which thermoregulated ligand Ph2P(CH2CH2O)22CH 3-stabilized Rh nanoparticles were used as catalysts for the hydrogenation of olefins. Under the optimized reaction conditions, the conversion of cyclohexene and the yield of cyclohexane were 99. The catalyst can be easily separated from the product by phase separation and it can be recycled eight times without a loss of activity.
- Chen, Zhijun,Wang, Yanhua,Jiang, Jingyang,Jin, Zilin
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- Co-Catalyzed Cross-Coupling Reaction of Alkyl Fluorides with Alkyl Grignard Reagents
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The cross-coupling reaction of unactivated alkyl fluorides with alkyl Grignard reagents by a CoCl2/LiI/1,3-pentadiene catalytic system is described. The present reaction smoothly cleaved C-F bonds under mild conditions and achieved alkyl-alkyl cross-coupling even when sterically hindered tertiary alkyl Grignard reagents were employed. Since alkyl fluorides are inert toward many reagents and catalytic intermediates, the use of the present reaction enables a new multistep synthetic route to construct carbon frameworks by combining conventional transformations.
- Iwasaki, Takanori,Yamashita, Koji,Kuniyasu, Hitoshi,Kambe, Nobuaki
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- Preparation of Supported Palladium Catalysts using Deep Eutectic Solvents
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Deep eutectic solvents (DESs) dissolve metal salts or oxides and are used as solvent and carbon source for the preparation of supported palladium catalysts. After dissolving of the palladium salt in the DES, the pyrolysis of the mixture under nitrogen atmosphere yields catalytically active palladium on supporting material composed of carbon, nitrogen and oxygen (CNO) by a simple single step preparation method without further activation. The catalysts were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and CHNS/O elementary analysis. The amount of functional groups on the surface of the supporting material was determined by Boehm titrations. Moreover, the activity of the prepared catalysts was evaluated in the hydrogenation of linear alkenes and compared with a commercial Pd/C catalyst.
- Iwanow, Melanie,Finkelmeyer, Jasmin,S?ldner, Anika,Kaiser, Manuela,G?rtner, Tobias,Sieber, Volker,K?nig, Burkhard
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- Wilkinson-type hydrogenation catalysts immobilized on zirconium phosphate nanoplatelets
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Immobilized catalysts can be obtained by using a linker to bind a homogeneous catalyst to a solid support. Ideally, immobilized catalysts combine the advantages of homogeneous and heterogeneous catalysts. Porous supports such as silica result in optimal recyclability, however, the catalytic reactions are slowed down by pore diffusion. Here, non-porous zirconium phosphate nanoplatelets (ZrP) are used as support material to bridge the gap between homogeneous and immobilized catalysts. ZrP nanoplatelets provide sufficient outside surface area, while still being easily separable from the reaction mixtures. First, a phosphine linker containing an ethoxysilyl group, (EtO) 3Si(CH2)3PPh2 (1), is reacted with ZrP to give the phosphine-modified 1i. Addition of Wilkinson's catalyst ClRh(PPh3)3 to 1i gives, via ligand exchange, the immobilized catalyst 1i-Rh. In the absence of pore diffusion the catalytic hydrogenation of 1-dodecene using 1i-Rh proceeds with unprecedented speed and the catalyst can be recovered and recycled 15 times. In the course of the catalytic reaction the mononuclear species forms catalytically active Rh nanoparticles on the surface. Finally it is demonstrated that ClRh(PPh 3)3 can be bound to ZrP directly without linker. However, the catalytic activity of the resulting material ZrP-Rh does not quite match the favorable characteristics of 1i-Rh.
- Silbernagel, Rita,Díaz, Agustín,Steffensmeier, Eric,Clearfield, Abraham,Blümel, Janet
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- Synthesis and characterization of tridentate phosphine ligands incorporating long methylene chains and ethoxysilane groups for immobilizing molecular rhodium catalysts
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The new tridentate phosphine ligands EtOSi((CH2)nPPh2)3 and O[Si((CH2)nPPh2)3]2 (n = 4, 7, 11), as well as their precursor ethoxysilanes EtOSi((CH2)mCH = CH2)3 and disiloxanes O[Si((CH2)mCH = CH2)3]2 (m = 2, 5, 9) and EtOSi((CH2)11PPh2RhClCOD)3 (COD = cyclooctadiene) have been synthesized and fully characterized. The ethoxysilane- and disiloxane-containing phosphine ligands have been immobilized on silica via covalent siloxane bonds. The immobilized linkers have been characterized by 31P and 29Si CP/MAS and HRMAS NMR spectroscopy. The covalent siloxane bonds between the linkers and the silica surface prevent translational mobility of the phosphines. Immobilized Wilkinson-type Rh hydrogenation catalysts have been obtained by ligand exchange of ClRh(PPh3)3 and ClRhpyCOD (py = pyridine) with the surface-bound ligands. The single crystal X-ray structure of ClRhpyCOD has been reported. The activities and lifetimes have been studied for the hydrogenation of 1-dodecene. The new catalysts are highly active and they can be recycled up to 15 times without major loss of activity. Within the first hours of the catalytic reaction the initially molecular complexes form Rh nanoparticles with a narrow size distribution on the surface. The nanoparticles do not leach into the supernatant solution and are not air-sensitive.
- Guenther,Reibenspies,Blümel
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- 9,10-Dihydro-9,10-disilaanthracenes as a New Radical-based Reducing Agent: Importance of Transannular Interaction Between Silyl Radical and Silicon Atom
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9,10-Dihydro-9,10-disilaanthracenes containing Si-H moieties at 9,10-positions are effective reducing agents in AIBN-initiated dehalogenation and deoxygenation reactions, in which a transannular interaction between silyl radical and silicon atom is considered important.
- Oba, Makoto,Nishiyama, Kozaburo
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- Rh nanoparticle catalyzed hydrogenation of olefins in thermoregulated ionic liquid and organic biphase system
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Rh nanoparticle catalyzed hydrogenation of olefins in a biphase system composed of [CH3(OCH2CH2)16N +Et3][CH3SO3-] (IL PEG750) ionic liquid and organic solvent allows for not only a highly efficient homogeneous catalytic reaction, but also an easy separation and reuse of catalyst attributed to the thermoregulated phase-transition property of the ILPEG750 and organic biphase system. Under the optimized conditions, various alkenes could be hydrogenated to the corresponding alkanes as the sole product with 100% conversion. The Rh nanoparticles can be recovered by simple phase separation and reused for nine times without evident loss of activity.
- Zeng, Yan,Wang, Yanhua,Jiang, Jingyang,Jin, Zilin
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- Lithium hydride containing complex reducing agent: A new and simple activation of commercial lithium hydride
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Commercially available lithium hydride, an essentially inert metal hydride, can be activated as a hydride source by in situ generated lithium alkoxide in the presence of a nickel salt. The obtained new reagent exhibited reducing properties versus alkyl or aryl halides, ketones, ethylenic or sulfurated compounds as well as coupling properties versus aryl halides when prepared in the presence of a ligand.
- Fort, Yves
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- On the potentially excellent reducing ability of a series of low-valent rare earths induced by photoirradiation
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Mixed systems of a series of rare earth metals such as La, Ce, Pr, Nd, Sm, Eu, and Yb and their low-valent rare earth diiodides exhibit excellent reducing ability toward the reductive deiodation from 1-iodododecane as a model compound compared with their single systems. More importantly, under photoirradiation conditions, the C-I bond reduction using 'Ln/LnI2' takes place efficiently in refluxing THF, even in the cases of heavy rare earths such as Gd, Tb, Dy, Ho, Er, and Tm.
- Tomisaka, Yuri,Nomoto, Akihiro,Ogawa, Akiya
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- Palladium-catalyzed reduction of olefins with triethylsilane
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The versatility of the palladium(II) chloride and triethylsilane system has been tested in the hydrogenation of 1-alkenes. The reduction of 1-alkenes was carried out in the presence of triethylsilane, ethanol and a catalytic amount of palladium(II) chloride, at room temperature. This facile and efficient method affords high yields for hydrogenation of unsaturated alkenes to the corresponding alkanes.
- Mirza-Aghayan, Maryam,Boukherroub, Rabah,Bolourtchian, Mohammad,Hosseini, Maryam
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- p-Bis(diphenylhydrosilyl)benzene. A useful Reagent for the Deoxygenation of Alcohols via Acetates
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Acetates which were derived from primary, secondary, and tertiary alcohols were deoxygenated to the corresponding hydrocarbons in high yield by p-bis(diphenylhydrosilyl)benzene under homolytic conditions.
- Sano, Hiroshi,Takeda, Toshimitsu,Migita, Toshihiko
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- The Retro-Hydroformylation Reaction
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Hydroformylation, a reaction that adds carbon monoxide and dihydrogen across an unsaturated carbon-carbon multiple bond, has been widely employed in the chemical industry since its discovery in 1938. In contrast, the reverse reaction, retro-hydroformylation, has seldom been studied. The retro-hydroformylation reaction of an aldehyde into an alkene and synthesis gas (a mixture of carbon monoxide and dihydrogen) in the presence of a cyclopentadienyl iridium catalyst is now reported. Aliphatic aldehydes were converted into the corresponding alkenes in up to 91 % yield with concomitant release of carbon monoxide and dihydrogen. Mechanistic control experiments indicated that the reaction proceeds by retro-hydroformylation and not by a sequential decarbonylation-dehydrogenation or dehydrogenation-decarbonylation process.
- Kusumoto, Shuhei,Tatsuki, Toshiumi,Nozaki, Kyoko
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- Mechanistic study of the samarium diiodide - N,N-dimethyl-2-aminoethanol reducing system
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The impact of N,N-dimethyl-2-aminoethanol (DMAE) on the reactivity of SmI2 is presented. The SmI2-DMAE reagent system is capable of reducing a range of substrates including alkyl halides, ketones, lactones, and arenes. Mechanistic studies on anthracene reduction are consistent with a system that proceeds through a highly ordered, early transition state requiring 2 equiv of DMAE and 1 equiv of anthracene and Sm(II).
- Chciuk, Tesia V.,Boland, Brian P.,Flowers, Robert A.
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- Acid-tolerant cyclodextrin-based ruthenium nanoparticles for the hydrogenation of unsaturated compounds in water
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A water-soluble β-cyclodextrin polymer synthesized by crosslinking β-cyclodextrin with epichlorohydrin and glycidyltrimethylammonium chloride allowed the stabilization of ruthenium nanoparticles not only in basic aqueous medium but also in acidic medium. The aqueous ruthenium colloidal suspensions obtained with this polymer were active as catalysts for the hydrogenation of a large variety of unsaturated compounds including aromatic or fatty acids. The recycling of this catalytic system was attested through ten consecutive runs without loss of stability and activity, demonstrating its robustness.
- No?l, Sébastien,Bourbiaux, Dolorès,Tabary, Nicolas,Ponchel, Anne,Martel, Bernard,Monflier, Eric,Léger, Bastien
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- Phenylsilane: A convenient reagent for the radical dehalogenation of organic halides
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Phenylsilane has been used for the reduction of alkyl and aryl halides. The method offers mild, neutral reaction conditions, easy work-up process, and high yields of the dehalogenated products.
- Jang, Doo Ok
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- Light-Driven Enzymatic Decarboxylation of Dicarboxylic Acids
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Photodecarboxylase from Chlorella variabillis (CvFAP) is one of the three known light-activated enzymes that catalyzes the decarboxylation of fatty acids into the corresponding C1-shortened alkanes. Although the substrate scope of CvFAP has been altered by protein engineering and decoy molecules, it is still limited to mono-fatty acids. Our studies demonstrate for the first time that long chain dicarboxylic acids can be converted by CvFAP. Notably, the conversion of dicarboxylic acids to alkanes still represents a chemically very challenging reaction. Herein, the light-driven enzymatic decarboxylation of dicarboxylic acids to the corresponding (C2-shortened) alkanes using CvFAP is described. A series of dicarboxylic acids is decarboxylated into alkanes in good yields by means of this approach, even for the preparative scales. Reaction pathway studies show that mono-fatty acids are formed as the intermediate products before the final release of C2-shortened alkanes. In addition, the thermostability, storage stability, and recyclability of CvFAP for decarboxylation of dicarboxylic acids are well evaluated. These results represent an advancement over the current state-of-the-art.
- Chen, Bi-Shuang,Liu, Lan,Zeng, Yong-Yi,Zhang, Wuyuan
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- Selective Alkyne Semi-Hydrogenation by PdCu Nanoparticles Immobilized on Stereocomplexed Poly(lactic acid)
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Polymer-supported PdCu alloy nanoparticles with a palladium to copper atom ratio of 1 have been synthesized upon: (i) Coordination of palladium/copper acetate to 2,2’-bipyridine-end functionalized poly(lactic acid) (PLA); (ii) Stereocomplexation of PLA-based macrocomplexes of opposite stereochemistry, and (iii) metal reduction with hydrogen. The obtained supported PdCu nanoparticles were successfully applied in the semi-hydrogenation of industrially important alkynols, such as 3-hexyn-1-ol and 2-butyne-1,4-diol leading to the corresponding cis-alkenol in high selectivity (98 %) under mild reaction conditions (i. e. ethanol, T (25 °C), p(H2)=3 bar) in the absence of any further additive. From a comparison of the catalytic performance of supported PdCu nanoparticles with those of Pd and Cu, located in the same chemical environment, emerged a clear alloy effect (i. e. high chemoselectivity for the alkene at high alkyne conversion). Recycling experiments conducted with the PdCu-based catalyst proved the stability of the catalyst with time, even by its recovering in air atmosphere.
- Capozzoli, Laura,Evangelisti, Claudio,Frediani, Marco,Mohammadi Dehcheshmeh, Iman,Najafi Moghadam, Peyman,Oberhauser, Werner,Poggini, Lorenzo
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- Hydrodeoxygenation of non-edible bio-lipids to renewable hydrocarbons over mesoporous SiO2-TiO2 supported NiMo bimetallic catalyst
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Ni-catalysts are promising candidate for fatty acid hydrodeoxygenation (HDO), but are limited by their quite poor HDO selectivity. Herein, a mesoporous Ni-Mo/SiO2-TiO2 catalyst was prepared by precipitation and impregnation method and used for methyl laurate HDO, yielding 96.3% n-dodecane yield at full methyl laurate conversion. Non-edible bio-lipids such as jatropha oil and waste cooking oil also converted to n-C14+16+18 hydrocarbons with yields of 94.3% and 92.4%, respectively. Besides, Ni-Mo/SiO2-TiO2 shows strong chemoselectivity towards the HDO of ester groups. Experimental results showed that Mo-addition and Ti/Si molar ratio strongly influenced HDO selectivity. Oxygen vacancies formed on partial reduced TiO2 surface securely bond Ni NPs and activate C[dbnd]O/C–O bonds, improving Ni NPs dispersion and promoting R–COOCH3→R–CHO reduction. Additional, Mo-addition switches reactant adsorption configuration from η1(C)-acyl to η2(C,O)-aldehyde, promoting the formation of R–CH2OH intermediate. Moreover, abundant Br?nsted acidic sites (Mo4+–OH, Mo6+–OH, hydroxy groups) facilitate the HDO of R-CH2OH to R-CH3.
- Ba, Wenxia,Fu, Lin,Li, Xin,Li, Yongfei,Liu, Yuejin,Zhang, Simiao,Zhao, Jingxuan
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- A New Protocol for Catalytic Reduction of Alkyl Chlorides Using an Iridium/Bis(benzimidazol-2′-yl)pyridine Catalyst and Triethylsilane
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The reduction of alkyl chlorides using triethylsilane is investigated. Primary, secondary, tertiary, and benzylic C-Cl bonds are effectively converted into C-H bonds using an [IrCl(cod)] 2/2,6-bis(benzimidazol-2′-yl)pyridine catalyst system. This catalyst system is quite simple since the tridentate N-ligand can be easily prepared in one step from commercially available reagents.
- Fukuyama, Takahide,Hamada, Yuki,Ryu, Ilhyong
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p. 3404 - 3408
(2021/07/14)
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- Microwave-Assisted Nickel-Catalyzed Rapid Reductive Coupling of Ethyl 3-iodopropionate to Adipic Acid
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Abstract: 3-iodopropionic acid (3-IPA) can be efficiently synthesized from the glycerol derivative glyceric acid (GA), which is a potential biomaterial-based platform molecule. In this report, ethyl 3-iodopropionate was rapidly dimerized to diethyl adipate in a microwave reactor using NiCl2·6H2O as a catalyst, co-catalyzed by Mn and the 1, 10-Phenanthroline monohydrate ligand. Under the optimum reaction conditions, diethyl adipate can be obtained with 84% yield at 90?°C in just 5?min. Diethyl adipate was hydrolyzed to obtain the adipic acid (AA) in 89% yield with an acid catalyst. AA is an important chemical and a monomer for producing a wide range of high-performance polymeric substances. This rapid coupling method is also applicable to other alkyl halides. Graphic Abstract: [Figure not available: see fulltext.]
- Zhang, Linfeng,Zheng, Jing,Zou, Wenya,Shu, Yongqi,Yang, Weiran
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p. 2339 - 2345
(2021/01/04)
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- Remarkable catalytic activity of polymeric membranes containing gel-trapped palladium nanoparticles for hydrogenation reactions
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Polymeric flat-sheet membranes and hollow fibers were prepared via UV photo-initiated polymerization of acrylic acid at the surface of commercial polyether sulfones (PES) membranes. These polymeric materials permitted to immobilize efficiently palladium nanoparticles (PdNP), which exhibited a mean diameter in the range of 4?6 nm. These materials were synthesized by chemical reduction of Pd(II) precursors in the presence of the corresponding support. We successfully applied the as-prepared catalytic materials in hydrogenation reactions under continuous flow conditions. Flat sheet membranes were more active than hollow fibers due to the flow configuration and defavorable operating conditions. Actually, various functional groups (i.e. C[dbnd]C, C[tbnd]C and NO2) were reduced in flow-through configuration, under mild conditions (between 1.4 and 2.2 bar H2 at 60 °C, using 3.2 mol% of Pd loading), archiving high conversions in short reaction times (12?24 s).
- López-Viveros, Melissa,Favier, Isabelle,Gómez, Montserrat,Lahitte, Jean-Fran?ois,Remigy, Jean-Christophe
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p. 263 - 269
(2020/05/13)
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- Boosting homogeneous chemoselective hydrogenation of olefins mediated by a bis(silylenyl)terphenyl-nickel(0) pre-catalyst
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The isolable chelating bis(N-heterocyclic silylenyl)-substituted terphenyl ligand [SiII(Terp)SiII] as well as its bis(phosphine) analogue [PIII(Terp)PIII] have been synthesised and fully characterised. Their reaction with Ni(cod)2(cod = cycloocta-1,5-diene) affords the corresponding 16 VE nickel(0) complexes with an intramolecularη2-arene coordination of Ni, [E(Terp)E]Ni(η2-arene) (E = PIII, SiII; arene = phenylene spacer). Due to a strong cooperativity of the Si and Ni sites in H2activation and H atom transfer, [SiII(Terp)SiII]Ni(η2-arene) mediates very effectively and chemoselectively the homogeneously catalysed hydrogenation of olefins bearing functional groups at 1 bar H2pressure and room temperature; in contrast, the bis(phosphine) analogous complex shows only poor activity. Catalytic and stoichiometric experiments revealed the important role of the η2-coordination of the Ni(0) site by the intramolecular phenylene with respect to the hydrogenation activity of [SiII(Terp)SiII]Ni(η2-arene). The mechanism has been established by kinetic measurements, including kinetic isotope effect (KIE) and Hammet-plot correlation. With this system, the currently highest performance of a homogeneous nickel-based hydrogenation catalyst of olefins (TON = 9800, TOF = 6800 h?1) could be realised.
- Lücke, Marcel-Philip,Yao, Shenglai,Driess, Matthias
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p. 2909 - 2915
(2021/03/14)
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- Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core–Shell Catalyst
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A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments.
- Beller, Matthias,Feng, Lu,Gao, Jie,Jackstell, Ralf,Jagadeesh, Rajenahally V.,Liu, Yuefeng,Ma, Rui
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supporting information
p. 18591 - 18598
(2021/06/28)
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- Synthesis and Reactivity of (N2P2)Ni Complexes Stabilized by a Diphosphonite Pyridinophane Ligand
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A series of (N2P2)NiIIcomplexes (N2P2 =P,P′-ditertbutyl-2,11-diphosphonito[3.3](2,6)pyridinophane) stabilized by a modified tetradentate pyridinophane ligand containing two phosphonite groups were synthesized and characterized. Cyclic voltammetry (CV) studies revealed the accessibility of the NiIoxidation state at moderate redox potentials for these NiIIcomplexes.In situEPR, low-temperature UV-vis, and electrochemical studies were employed to detect the formation of NiIspecies during the reduction of NiIIprecursors. Furthermore, the [(N2P2)NiI(CNt-Bu)](SbF6) complex was isolated upon reduction of the NiIIprecursor with 1 equiv of CoCp2and was characterized by EPR and X-ray photoelectron spectroscopy (XPS). Finally, the (N2P2)NiIIBr2complex acts as an efficient catalyst for the Kumada cross-coupling of an aryl halide with an aryl or alkyl Grignard, suggesting that the N2P2 ligand can support the various Ni species involved in the catalytic C-C bond formation reactivity.
- Fuchigami, Kei,Watson, Michael B.,Tran, Giang N.,Rath, Nigam P.,Mirica, Liviu M.
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supporting information
p. 2283 - 2289
(2021/05/06)
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- Visible light-driven Giese reaction with alkyl tosylates catalysed by nucleophilic cobalt
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The scope of the Giese reaction is expanded using readily available alkyl tosylates as substrates and nucleophilic cobalt(i) catalysts under visible-light irradiation. The reaction proceeds preferentially with less bulky primary alkyl tosylates. This unique reactivity enables the regio-selective Giese reaction of polyol derivatives.
- Komeyama, Kimihiro,Michiyuki, Takuya,Teshima, Yoshikazu,Osaka, Itaru
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p. 3539 - 3546
(2021/02/03)
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- Heterogeneously Catalyzed Selective Decarbonylation of Aldehydes by CeO2-Supported Highly Dispersed Non-Electron-Rich Ni(0) Nanospecies
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Aldehyde decarbonylation has been extensively investigated, primarily using noble-metal catalysts; however, nonprecious-base-metal-catalyzed aldehyde decarbonylation has been hardly reported. We have established an efficient selective aldehyde decarbonylation reaction with a broad substrate scope and functional group tolerance utilizing a heterogeneous Ni(0) nanospecies catalyst supported on CeO2. The high catalytic performance is attributable to the highly dispersed and non-electron-rich Ni(0) nanospecies, which possibly suppress a side reaction producing esters and adsorbed CO-derived inhibition of the catalytic turnover, according to detailed catalyst characterization and kinetic evaluation.
- Matsuyama, Takehiro,Yatabe, Takafumi,Yabe, Tomohiro,Yamaguchi, Kazuya
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p. 13745 - 13751
(2021/11/17)
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- 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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- Palladium nanoparticles stabilized by novel choline-based ionic liquids in glycerol applied in hydrogenation reactions
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Palladium nanoparticles stabilized by choline-based ionic liquids in glycerol were prepared from Pd(II) precursors by simply heating at 80 °C under argon; in this process, the water present in the ionic liquid was found to be responsible for the reduction of Pd(II) into zero-valent palladium species. Palladium nanoparticles were fully characterized in both liquid phase and solid state. The as-prepared metal nanoparticles exhibited remarkable catalytic activity in hydrogenation processes for a significant variety of functional groups (alkenes, alkynes, nitro derivatives, benzaldehydes, aromatic ketones).
- Garg, Garima,Foltran, Stéphanie,Favier, Isabelle,Pla, Daniel,Medina-González, Yaocihuatl,Gómez, Montserrat
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- Catalytic Activity of a Zr MOF Containing POCOP-Pd Pincer Complexes
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A metal-organic framework assembled from POCOP-Pd pincer complex metallolinkers (1-PdBF4, Zr6O4(OH)4(L-PdMeCN)3(BF4)3, L = (2,6-(OPAr2)2C6H3, Ar = p-C6H4CO2-) has been generated via postsynthetic oxidative I-/BF4- ligand exchange with NOBF4. 1-PdBF4 catalyzes a range of organic transformations, including transfer hydrogenation of unsaturated organic substrates, terminal alkyne hydration, and intramolecular hydroarylation of alkynes. The homogeneous analogue, tBu4POCOP-PdBF4, shows poor catalytic activity for transfer hydrogenation and alkyne hydration and decomposes under the catalytic reaction conditions. Solubility limitations and catalyst deactivation pathways observed for the homogeneous pincer complex propound the advantages of using porous solid supports to immobilize organometallic species.
- Kassie, Abebu A.,Wade, Casey R.
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p. 2214 - 2221
(2020/07/06)
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- Transition metal complexes of a bis(carbene) ligand featuring 1,2,4-triazolin-5-ylidene donors: structural diversity and catalytic applications
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Dialkylation of the 1,3-bis(1,2,4-triazol-1-yl)benzene with ethyl bromide results in the formation of [L-H2]Br2which, upon salt metathesis with NH4PF6, readily yields the bis(triazolium) salt [L-H2](PF6)2with non-coordinating counterions. [L-H2](PF6)2and Ag2O react in a 1?:?1 ratio to yield a binuclear AgI-tetracarbene complex of the composition [(L)2Ag2](PF6)2which undergoes a facile transmetalation reaction with [Cu(SMe2)Br] to deliver the corresponding CuI-NHC complex [(L)2Cu2](PF6)2. In contrast, the [L-H2]Br2reacts with [Ir(Cp*)Cl2]2to generate a doubly C-H activated IrIII-NHC complex5. Similarly, the triazolinylidene donor supported diorthometalated RuII-complex6is also obtained. Complexes5and6represent the first examples of a stable diorthometalated binuclear IrIII/RuII-complex supported by 1,2,4-triazolin-5-ylidene donors. The synthesized IrIII-NHC complex5is found to be more effective than its RuII-analogue (6) for the reduction of a range of alkenes/alkynesviathe transfer hydrogenation strategy. Conversely, RuII-complex6is identified as an efficient catalyst (0.01 mol% loading) for the β-alkylation of a wide range of secondary alcohols using primary alcohols as alkylating partnersviaa borrowing hydrogen strategy.
- Donthireddy, S. N. R.,Illam, Praseetha Mathoor,Rit, Arnab,Singh, Vivek Kumar
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p. 11958 - 11970
(2020/09/21)
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- CuPd Nanoparticles as a Robust Catalyst for Electrochemical Allylic Alkylation
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An efficient CuPd nanoparticle (NP) catalyst (3 nm CuPd NPs deposited on carbon support) is designed for catalyzing electrochemical allylic alkylation in water/isopropanol (1:1 v/v) and 0.2 m KHCO3 solution at room temperature. The Pd catalysis was Pd/Cu composition-dependent, and CuPd NPs with a Pd/Cu ratio close to one are the most efficient catalyst for the selective cross-coupling of alkyl halides and allylic halides to form C?C hydrocarbons with product yields reaching up to 99 %. This NP-catalyzed electrochemical allylic alkylation expands the synthetic scope of cross-coupling reactions and can be further extended to other organic reaction systems for developing green chemistry electrosynthesis methods.
- Guo, Xuefeng,Lin, Honghong,Muzzio, Michelle,Pang, Huan,Shen, Mengqi,Sun, Shouheng,Wei, Kecheng,Williard, Paul,Yin, Zhouyang,Yu, Chao
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supporting information
p. 15933 - 15936
(2020/07/04)
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- One-pot synthesis of aldoximes from alkenes: Via Rh-catalysed hydroformylation in an aqueous solvent system
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Aldoxime synthesis directly starting from alkenes was successfully achieved through the combination of hydroformylation and subsequent condensation of the aldehyde intermediate with aqueous hydroxylamine in a one-pot process. The metal complex Rh(acac)(CO)2 and the water-soluble ligand sulfoxantphos were used as the catalyst system, providing high regioselectivities in the initial hydroformylation. A mixture of water and 1-butanol was used as an environmentally benign solvent system, ensuring sufficient contact of the aqueous catalyst phase and the organic substrate phase. The reaction conditions were systematically optimised by Design of Experiments (DoE) using 1-octene as a model substrate. A yield of 85% of the desired linear, terminal aldoxime ((E/Z)-nonanal oxime) at 95% regioselectivity was achieved. Other terminal alkenes were also converted successfully under the optimised conditions to the corresponding linear aldoximes, including renewable substrates. Differences of the reaction rate have been investigated by recording the gas consumption, whereby turnover frequencies (TOFs) >2000 h-1 were observed for 4-vinylcyclohexene and styrene, respectively. The high potential of aldoximes as platform intermediates was shown by their subsequent transformation into the corresponding linear nitriles using aldoxime dehydratases as biocatalysts. The overall reaction sequence thus allows for a straightforward synthesis of linear nitriles from alkenes with water being the only by-product, which formally represents an anti-Markovnikov hydrocyanation of readily available 1-alkenes.
- Gr?ger, H.,Guntermann, A.,Hinzmann, A.,Jolmes, T.,Panke, D.,Plass, C.,R?sler, J.,Seidensticker, T.,Terhorst, M.,Vogt, D.,Vorholt, A. J.
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supporting information
p. 7974 - 7982
(2020/11/30)
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- Iron-catalyzed protodehalogenation of alkyl and aryl halides using hydrosilanes
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A simple and efficient iron-catalyzed protodehalogenation of alkyl and aryl halides using phenylhydrosilane is disclosed. The reaction utilizes FeCl3 without the requirement of ligands. Unactivated alkyl and aryl halides were successfully reduced in good yields; sterically hindered tertiary halides were also reduced including the less reactive chlorides. The scalability of this methodology was demonstrated by a gram-scale synthesis with a catalyst loading as low as 0.5 mol%. Notably, disproportionation of phenylsilane leads to diphenylsilane that further reduces the halides. Preliminary mechanistic studies revealed a non-radical pathway and the source of hydrogen is PhSiH3via deuterium labeling studies. Our methodology represents simplicity and provides a good alternative to typical tin, aluminum and boron hydride reagents.
- Pilli, Ramadevi,Balakrishnan, Venkadesh,Chandrasekaran, Revathi,Rasappan, Ramesh
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supporting information
p. 1749 - 1753
(2019/02/20)
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- Iron-catalyzed regioselective cyclotrimerization of alkynes to benzenes
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We report the synthesis and characterization of simple di(aminomethyl)pyridine ligated iron-pincer complexes, which catalyzed the regioselective [2+2+2] cyclotrimerization of terminal aryl and alkyl alkynes to provide the 1,2,4-trisubstituted benzene molecules. Interestingly, internal alkynes also exhibited similar cyclization and resulted in hexa-substituted benzene compounds. Increased steric bulk on pincer ligands diminished the selectivity for cycloaddition. Cyclotrimerization reactions proceeded at room temperature upon activation of catalyst by a Grignard reagent. EPR studies indicated thermally induced spin crossover effect in catalyst.
- Gawali, Suhas Shahaji,Gunanathan, Chidambaram
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p. 139 - 149
(2019/01/03)
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- Amine-Borane Dehydrogenation and Transfer Hydrogenation Catalyzed by α-Diimine Cobaltates
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Anionic α-diimine cobalt complexes, such as [K(thf)1.5{(DippBIAN)Co(η4-cod)}] (1; Dipp=2,6-diisopropylphenyl, cod=1,5-cyclooctadiene), catalyze the dehydrogenation of several amine-boranes. Based on the excellent catalytic properties, an especially effective transfer hydrogenation protocol for challenging olefins, imines, and N-heteroarenes was developed. NH3BH3 was used as a dihydrogen surrogate, which transferred up to two equivalents of H2 per NH3BH3. Detailed spectroscopic and mechanistic studies are presented, which document the rate determination by acidic protons in the amine-borane.
- Maier, Thomas M.,Sandl, Sebastian,Shenderovich, Ilya G.,Jacobi von Wangelin, Axel,Weigand, Jan J.,Wolf, Robert
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supporting information
p. 238 - 245
(2019/01/04)
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- Aggregation-induced Substrate Specificity in Aerobic Reduction of Olefins with Ultrasound Gel Catalyst of Synthetic Flavin
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A riboflavin derivative bearing octadecanoyl functionalities 1 a gelatinizes a variety of organic solvents upon brief ultrasonication in an organic fluid. The rate of gelation with 1 a can be externally and precisely controlled by tuning the sonication time and type of solvent. The present ultrasound gel exhibits unprecedented substrate specificity for the catalytic aerobic reduction of olefins, which can be performed with hydrazine at ambient temperature and atmospheric pressure in air. The reaction rates of 1-dodecene (2), allylbenzene (3), and o-allylphenol (4) with the ultrasound gel 1 a catalyst is in the order of 2?3>4, the substrate specificity of which is in contrast to the almost non-specificity with the non-gelled catalyst 1 b bearing butanoyl functionalities, and entirely inverse specificity with a flavin-dendrimer association catalyst (234). Based on kinetic studies, the aggregation effects on the substrate specificity have been ascribed to the specific inclusion of aliphatic olefins into the enzyme-like artificial cavities of the gel catalysts.
- Kawamorita, Soichiro,Fujiki, Misa,Li, Zimeng,Kitagawa, Takahiro,Imada, Yasushi,Naota, Takeshi
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p. 878 - 884
(2019/01/14)
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- Hydrogenation of hydrophobic substrates catalyzed by gold nanoparticles embedded in Tetronic/cyclodextrin-based hydrogels
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Hydrogenation of alkenes, alkynes and aldehydes was investigated under biphasic conditions using Au nanoparticles (AuNP) embedded into combinations of α-cyclodextrin (α-CD) and a poloxamine (Tetronic90R4). Thermo-responsive AuNP-containing α-CD/Tetronic90R4 hydrogels are formed under well-defined conditions of concentration. The AuNP displayed an average size of ca. 7 nm and a narrow distribution, as determined by TEM. The AuNP/α-CD/Tetronic90R4 system proved to be stable over time. Upon heating above the gel-to-sol transition temperature, the studied catalytic system allowed hydrogenation of a wide range of substrates such as alkenes, alkynes and aldehydes under biphasic conditions. Upon repeated heating/cooling cycles, the Au NP/α-CD/Tetronic90R4 catalytic system could be recycled several times without a significant decline in catalytic activity.
- Chevry,Menuel,Léger,No?l,Monflier,Hapiot
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p. 9865 - 9872
(2019/07/04)
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- Integration of phosphine ligands and ionic liquids both in structure and properties-a new strategy for separation, recovery, and recycling of homogeneous catalyst
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The major limitation of classic biphasic ionic liquid (IL) catalysis is the heavy use of solvent ILs, which not only violates green chemistry principles but also even worsens catalytic efficiency. So it has always been a challenge finding ways to use ILs more efficiently, economically, and greenly to construct highly effective and long term stable IL catalytic systems. In this work, we synthesized a class of room temperature phosphine-functionalized polyether guanidinium ionic liquids (RTP-PolyGILs) by a convenient ion exchange reaction of polyether guanidinium ionic liquids (PolyGILs) with phosphine-sulfonate ligands based on the concept of the integration of both the phosphine ligand and IL. The resulting RTP-PolyGILs existed as liquids at room temperature and possessed dual functions of both the phosphine ligand and solvent IL; therefore they could both form catalysts by complexing with transition metals and act as catalyst carriers, thus achieving the integration of phosphine ligands with ILs both in structure and properties. Based on the unique properties of these multi-functional integrated RTP-PolyGILs, we constructed a highly effective homogeneous catalysis-biphasic separation (HCBS) system for Rh-catalyzed hydroformylation of higher olefins using only a catalytic amount of RTP-PolyGILs (equivalent to 0.025-0.4 mol% of 1-alkenes). Our HCBS system could be flexibly regulated with regard to catalytic performance (activity and linear selectivity) by changing the structure or type of the sulfonated ligand anion on RTP-PolyGILs. Specifically, it presented a TOF value of 3000-26000 h-1 and a linear selectivity of 68%-98% (corresponding to the l/b ratio of 2.2-37.5) with a total turnover number (TTON) of 11000-45000 and an extremely low Rh leaching of only 0.02-0.4 ppm. Therefore, the HCBS system can effectively combine the advantages of both homogeneous (high activity and good selectivity) and biphasic catalysis (easy catalyst separation). We additionally extended the application of the HCBS system to the hydrogenation of olefins to demonstrate the universality of the RTP-PolyGILs in catalytic reactions.
- Jin, Xin,Feng, Jianying,Song, Hongbing,Yao, Jiajun,Ma, Qingqing,Zhang, Mei,Yu, Cong,Li, Shumei,Yu, Shitao
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p. 3583 - 3596
(2019/07/10)
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- Iron-catalysed allylation-hydrogenation sequences as masked alkyl-alkyl cross-couplings
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An iron-catalysed allylation of organomagnesium reagents (alkyl, aryl) with simple allyl acetates proceeds under mild conditions (Fe(OAc)2 or Fe(acac)2, Et2O, r.t.) to furnish various alkene and styrene derivatives. Mechanistic studies indicate the operation of a homotopic catalyst. The sequential combination of such iron-catalysed allylation with an iron-catalysed hydrogenation results in overall C(sp3)-C(sp3)-bond formation that constitutes an attractive alternative to challenging direct cross-coupling protocols with alkyl halides.
- Bernauer, Josef,Wu, Guojiao,Von Wangelin, Axel
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p. 31217 - 31223
(2019/10/19)
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- Rethinking Basic Concepts-Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexes
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An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is atom economic, implementing an inexpensive, earth-abundant nonprecious metal catalyst. The most efficient precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)2(H)]. A range of mono- A nd disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 °C, while 1,2-disubstituted alkenes require a reaction temperature of 60 °C. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar were applied. A mechanism based on DFT calculations is presented, which is supported by preliminary experimental studies.
- Weber, Stefan,St?ger, Berthold,Veiros, Luis F.,Kirchner, Karl
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p. 9715 - 9720
(2019/10/14)
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- Axial Donor Effects on Oxidatively Induced Ethane Formation from Nickel-Dimethyl Complexes
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Tetradentate pyridinophane ligands have been shown to stabilize uncommon high-valent palladium and nickel organometallic complexes. Described herein are the synthesis and detailed characterization of a series of NiII- and NiIII-dimethyl complexes supported by modified tetradentate pyridinophane ligands in which one or both of the N-methyl substituents were replaced with electron-withdrawing p-toluenesulfonyl groups, thus reducing the amine N atom donicity and favoring the formation of Ni complexes with lower coordination numbers. The corresponding NiII-dimethyl complexes exhibit accessible oxidation potentials, and their oxidation generates NiIII species that were characterized by EPR and X-ray crystallography. Moreover, the NiII-dimethyl complexes exhibit selective ethane formation upon oxidatively induced reductive elimination using various oxidants - including O2 and H2O2, without the generation of any C-heteroatom products. Overall, these results suggest that the (RN4)NiIIMe2 complexes with more weakly donating axial ligands are more reactive toward ethane formation, likely due to destabilization of the corresponding high-valent Ni intermediates and formation of 5- and 4-coordinate conformations for these Ni species.
- Smith, Sofia M.,Rath, Nigam P.,Mirica, Liviu M.
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supporting information
p. 3602 - 3609
(2019/10/11)
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- Photocatalytic halohydrocarbon dehalogenation conversion method
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The invention provides a photocatalytic halohydrocarbon dehalogenation conversion method which comprises the following steps: adding a photocatalyst quantum dot/rod into a solvent to obtain a solutionA; adding halohydrocarbon and an electronic sacrificial body into the solution A to obtain a solution B; utilizing a light source to irradiate the solution B and catalyzing the solution B to performhalohydrocarbon dehalogenation conversion. According to the photocatalytic halohydrocarbon dehalogenation conversion method disclosed by the invention, a nano quantum dot and a nano quantum rod are applied to dehalogenation conversion reaction of alkyl halide, alkenyl halide and alkyne halide for the first time; the reaction conditions are moderate, visible light is utilized as driving energy, a product is hydrocarbon compound, and the whole process has the advantages of environmental protection, conciseness and high efficiency. In addition, higher hydrocarbon of carbon chain growth can be generated after dehalogenation reaction, so that the method has potential application in preparation of higher hydrocarbon. According to the method disclosed by the invention, halohydrocarbon dehalogenation conversion and deuteration marking processes are jointly performed; hydrocarbon deuteration marking can be finished when a halohydrocarbon dehalogenation process is finished. The invention furtherprovides a method for performing deuteration marking on hydrocarbon.
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Paragraph 0063; 0064
(2019/04/02)
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- The catalytic activity of alkali metal alkoxides and titanium alkoxides in the hydrosilylation of unfunctionalized olefins
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The catalytic activities of titanium alkoxides and alkali metal alkoxides for hydrosilylation of unfunctionalized olefins have been studied. Titanium(IV) alkoxides showed excellent catalytic activity, while alkali metal alkoxides have low catalytic activity for the hydrosilylation of olefins. However, by using titanocene dichloride as an additive, alkali metal alkoxides showed also excellent catalytic property for hydrosilylation. In comparison with titanium alkoxides, no α-adduct was obtained by using alkali metal alkoxides/Cp2TiCl2 as catalysts.
- Yang, Xiaoling,Bai, Ying,Li, Jiayun,Liu, Yu,Peng, Jiajian,Li, Tianbo,Lang, Rui,Qiao, Botao
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- Ethylene and Cyclohexene Oxidation by p-Benzoquinone, Hydrogen Peroxide, and Oxygen in the Solutions of Cationic Pd(II) Complexes in Acetonitrile–Water and Ionic Liquid–Water Binary Solvents
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Abstract: Optimal conditions are selected for ethylene and cyclohexene oxidation reactions in the acetonitrile (AN)–water system in the presence of Pd(AN)x(H2O)4 - x2+ complexes. It is shown that hydrogen peroxide oxidizes hydroquinone (QН2) in acetonitrile solutions and in ionic liquids (BMIM+BF4-,BMIM+PF6-, and the rates of ethylene oxidation in the BMIM+PF6- ionic liquid in the presence of p-benzoquinone (Q) and hydroquinone are the same. It is shown that solid and soluble phthalocyanine iron complexes catalyze oxidation of olefins by oxygen in acidic acetonitrile media by converting p-benzoquinone to the third catalyst of the process. The apparent first-order rate constants of hydroquinone oxidation by oxygen are determined. The use of the IL–Н2О–Н2SO4 system is found to be inappropriate for cyclohexanone synthesis because of the formation of byproducts of cyclohexene conversion.
- Efremov,Bovyrina,Podtyagina,Oshanina,Temkin
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- Mechanistic Insight into Synergistic Catalysis of Olefin Hydrogenation by a Hetero-Dinuclear RuII-CoII Complex with Adjacent Reaction Sites
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We have designed and synthesized a hetero-dinuclear RuII-CoII complex with a dinucleating ligand inspired by hetero-dinuclear active sites of metalloenzymes. A synergistic effect between the adjacent RuII and CoII sites has been confirmed in catalytic olefin hydrogenation by the complex, exhibiting a much higher turnover number than those of mononuclear RuII or CoII complexes as the components. A RuII-hydrido species was detected by 1H NMR and electrospray ionization (ESI)-time-of-flight (TOF)-MS measurements as an intermediate to react with olefins, and CoII-bound methanol was suggested to act as a proton source.
- Hong, Dachao,Ohgomori, Yuji,Shimoyama, Yoshihiro,Kotani, Hiroaki,Ishizuka, Tomoya,Kon, Yoshihiro,Kojima, Takahiko
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supporting information
p. 11284 - 11288
(2019/09/03)
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- Titanium-catalyzed hydrosilylation of olefins: A comparison study on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4 catalyst system
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Hydrosilylation of olefins catalyzed by Cp2TiCl2/Sm (Cp = cyclopentadienyl) under solvent free conditions have been investigated. By using Cp2TiCl2/Sm as catalyst system, β-adducts and hydrogenation products were detected. Hydrosilylation of olefins catalyzed by Cp2TiCl2/LiAlH4 under room temperature has also been studied. The influence of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4, respectively, indicated that hydrosilylation of olefins catalyzed with Cp2TiCl2/Sm went through a free radical reaction pathway while a coordination mechanism was applied for Cp2TiCl2/LiAlH4 catalyst system.
- Yang, Xiaoling,Bai, Ying,Li, Jiayun,Liu, Yu,Peng, Jiajian,Li, Tianbo,Lang, Rui,Qiao, Botao
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- Iron-catalyzed AlkylAlkyl negishi coupling of organoaluminum reagents
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The first iron-catalyzed cross-coupling reaction of alkyl halides with alkylaluminum reagents (alkylalkyl Negishi coupling) is developed using an iron/bisphosphine catalyst system. The reaction shows high functional group tolerance: various primary alkyl halides possessing a non-protected indole, carboxyl, or hydroxy group are coupled with primary alkylaluminum reagents in good yields. Potassium fluoride plays a key role to promote the reaction by generating an aluminate species, which facilitates the transmetalation between the organoaluminum and the iron catalyst.
- Agata, Ryosuke,Kawamura, Shintaro,Isozaki, Katsuhiro,Nakamura, Masaharu
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supporting information
p. 238 - 241
(2019/03/13)
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- Hexadecane Conversion on an Alumina–Nickel Catalyst
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Abstract: The conversion of hexadecane on a 4% Ni/Al2O3 catalyst in a temperature range of 20–300°C was studied using IR spectroscopy and catalytic methods. It was found that the dehydrogenation of hexadecane occurred at 20–100°C with the subsequent formation of aromatic products, but the rates of these processes were very low. As the reaction temperature was increased to 200°C, the 4% Ni/Al2O3 catalyst exhibited a maximum activity and high selectivity for the formation of 1-hexadecene, and aromatic compounds and cracking products were present in the reaction products. As the reaction temperature was further increased, the catalytic activity significantly decreased. This was due to the fact that polyaromatic deposits gradually accumulated on the catalyst surface in a temperature range of 200–300°C.
- Chesnokov,Chichkan,Paukshtis,Chesalov, Yu. A.,Krasnov
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p. 439 - 445
(2019/09/04)
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- Structure-Function Relationship in Ester Hydrogenation Catalyzed by Ruthenium CNN-Pincer Complexes
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A series of six pincer-ruthenium complexes has been synthesized and applied in the catalytic hydrogenation of esters. The ruthenium complexes have the formula Ru(pincer)HCl(CO), where the CNN-pincer ligands feature N-heterocyclic carbene (NHC), pyridine, and dialkylamino donor groups. Through systematic variation of the steric bulk of the NHC substituent and the amine substituents, a clear structure-function relationship emerges. The most active catalysts in this series feature the bulkiest NHC substituent employed, 2,6-diisopropylphenyl. For the dialkylamino group, catalysts substituted with isopropyl or ethyl groups were the most active, while catalysts substituted with methyl groups were significantly less active. The most active catalyst discovered catalyzes the complete hydrogenation of a range of esters at loadings of 0.05-0.2 mol %.
- Le, Linh,Liu, Jiachen,He, Tianyi,Kim, Daniel,Lindley, Eric J.,Cervarich, Tia N.,Malek, Jack C.,Pham, John,Buck, Matthew R.,Chianese, Anthony R.
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p. 3286 - 3297
(2018/09/27)
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- Sodium borohydride-nickel chloride hexahydrate in EtOH/PEG-400 as an efficient and recyclable catalytic system for the reduction of alkenes
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An efficient, safe and one-pot convenient catalytic system has been developed for the reduction of alkenes using NaBH4-NiCl2·6H2O in EtOH/PEG-400 under mild conditions. In this catalytic system, a variety of alkenes (including trisubstituted alkene α-pinene) were well reduced and the Ni catalyst could be recycled.
- Li, Kaoxue,Liu, Chuanchao,Wang, Kang,Ren, Yang,Li, Fahui
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p. 7761 - 7764
(2018/03/01)
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- Recyclable cobalt(0) nanoparticle catalysts for hydrogenations
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The search for new hydrogenation catalysts that replace noble metals is largely driven by sustainability concerns and the distinct mechanistic features of 3d transition metals. Several combinations of cobalt precursors and specific ligands in the presence of reductants or under high-thermal conditions were reported to provide active hydrogenation catalysts. This study reports a new method of preparation of small, monodisperse Co(0) nanoparticles (3-4 nm) from the reduction of commercial CoCl2 in the absence of ligands or surfactants. High catalytic activity was observed in hydrogenations of alkenes, alkynes, imines, and heteroarenes (2-20 bar H2). The magnetic properties enabled catalyst separation and multiple recyclings.
- Büschelberger, Philipp,Reyes-Rodriguez, Efrain,Sch?ttle, Christian,Treptow, Jens,Feldmann, Claus,Jacobi Von Wangelin, Axel,Wolf, Robert
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p. 2648 - 2653
(2018/05/30)
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- Preparation of MOF Confined Ag Nanoparticles for the Highly Active, Size Selective Hydrogenation of Olefins
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Catalysts with both high activity and good selectivity for hydrogenation of olefins to alkanes are of interest. Herein, MOF confined ultrafine Ag NPs (Ag@HKUST-1) were synthesized by double-solvent approach using HKUST-1 as the template and support. HKUST-1 with narrow cage size distribution (0.5 to 0.9 nm) confined the growth of Ag NPs, while the uniform pores prohibited the entrance of olefins with the molecular size lager than 5.0 ?, which endow the Ag@HKUST-1 with high catalytic activity and size selectivity for hydrogenation reaction. The hydrogenation of eight kinds of olefins with different molecular size (1-hexene, cyclohexene, 1-octene, cyclooctene, styrene, 1-decene, 1, 1-diphenylethylene, and 1-dodecene) catalyzed by Ag@HKUST-1 confirmed this hypothesis. The olefins with molecular smaller than 5.0 ? were efficiently converted to the corresponding alkanes, whereas those greater than 5.0 ? exhibited extremely low conversation. The catalyst also exhibited high recycle stability in the hydrogenation of styrene.
- Chen, Wen-Jing,Cheng, Bin-Hai,Sun, Qing-Ting,Jiang, Hong
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p. 3659 - 3665
(2018/08/07)
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- Palladium/Graphitic Carbon Nitride (g-C3N4) Stabilized Emulsion Microreactor as a Store for Hydrogen from Ammonia Borane for Use in Alkene Hydrogenation
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Direct hydrogenation of C=C double bonds is a basic transformation in organic chemistry which is vanishing from simple practice because of the need for pressurized hydrogen. Ammonia borane (AB) has emerged as a hydrogen source through its safety and high hydrogen content. However, in conventional systems the hydrogen liberated from the high-cost AB cannot be fully utilized. Herein, we develop a novel Pd/g-C3N4 stabilized Pickering emulsion microreactor, in which alkenes are hydrogenated in the oil phase with hydrogen originating from AB in the water phase, catalysed by the Pd nanoparticles at the interfaces. This approach is advantageous for more economical hydrogen utilization over conventional systems. The emulsion microreactor can be applied to a range of alkene substrates, with the conversion rates achieving >95 % by a simple modification.
- Han, Chenhui,Meng, Peng,Waclawik, Eric R.,Zhang, Chao,Li, Xin-Hao,Yang, Hengquan,Antonietti, Markus,Xu, Jingsan
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supporting information
p. 14857 - 14861
(2018/10/24)
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- Electron transfer-induced reduction of organic halides with amines
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Reduction of a variety of organo halides was examined by using amines as a sacrificial hydrogen source. UV light-induced reduction of vinyl and aryl halides with triethylamine proceeded smoothly to give the corresponding reduced products. High temperature heating also caused the reduction and DABCO (1,4-diazabicyclo[2.2.2]octane) also served as a good reducing reagent.
- Fukuyama, Takahide,Fujita, Yuki,Miyoshi, Hayato,Ryu, Ilhyong,Kao, Shih-Chieh,Wu, Yen-Ku
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supporting information
p. 5582 - 5585
(2018/06/04)
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- Selective Hydrogenation of Carboxylic Acids to Alcohols or Alkanes Employing a Heterogeneous Catalyst
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The chemoselective hydrogenation of carboxylic acids to either alcohols or alkanes is reported, employing a heterogeneous bimetallic catalyst consisting of rhenium and palladium supported on graphite. α-Chiral carboxylic acids were hydrogenated without loss of optical purity. The catalyst displays a reverse order of reactivity upon hydrogenation of different carboxylic functions with esters being less reactive than amides and carboxylic acids. This allows for chemoselective hydrogenation of an acid in the presence of an ester or an amide function.
- Ullrich, Johannes,Breit, Bernhard
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p. 785 - 789
(2018/02/14)
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- Stainless Steel-Mediated Hydrogen Generation from Alkanes and Diethyl Ether and Its Application for Arene Reduction
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Hydrogen gas can be generated from simple alkanes (e.g., n-pentane, n-hexane, etc.) and diethyl ether (Et2O) by mechanochemical energy using a planetary ball mill (SUS304, Fritsch Pulverisette 7), and the use of stainless steel balls and vessel is an important factor to generate the hydrogen. The reduction of organic compounds was also accomplished using the in-situ-generated hydrogen. While the use of pentane as the hydrogen source facilitated the reduction of the olefin moieties, the arene reduction could proceed using Et2O. Within the components (Fe, Cr, Ni, etc.) of the stainless steel, Cr was the metal factor for the hydrogen generation from the alkanes and Et2O, and Ni metal played the role of the hydrogenation catalyst.
- Sawama, Yoshinari,Yasukawa, Naoki,Ban, Kazuho,Goto, Ryota,Niikawa, Miki,Monguchi, Yasunari,Itoh, Miki,Sajiki, Hironao
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supporting information
p. 2892 - 2896
(2018/05/29)
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- Hydrodeoxygenation of Sorbitol into Bio-Alkanes and -Alcohols Over Phosphated Ruthenium Molybdenum Catalysts
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Biofuels such as renewable alkanes and higher alcohols have drawn considerable interests for the use in internal combustion engines. Especially, higher alcohols could be used as a blending agent for diesel fuels. Herein, carbon supported phosphated ruthenium-molybdenum (RuMoP) catalysts were employed in continuous trickle-bed reactor for converting sorbitol into renewable alkanes and higher alcohols. The results showed that RuMoP on an active carbon (AC) support presented a complete sorbitol conversion and high yields of alkanes and alcohols in gasoline and diesel range. Subsequently, carbon nanotube (CNT) supported RuMoP was prepared and studied in detail for comparison. RuMoP/CNT presented a low C?C bond cracking property in sorbitol conversion and high selectivity of C6 products in gas-phase (C6 alkane, 74.7 %) and oil-phase (C6 alkane and alcohols, 87.8 %). Finally, detailed characterizations (N2-adsorption, XRD, HRTEM, XPS, NH3-TPD, Py-IR spectrums, etc.) were performed over relevant catalysts (RuMoP/C and RuMoP/CNT) for correlating their catalytic and physicochemical properties.
- Weng, Yujing,Wang, Tiejun,Wang, Chenguang,Liu, Qiying,Zhang, Yulong,Duan, Peigao,Wang, Longlong,Yin, Hongxing,Liu, Shijun,Ma, Longlong
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p. 5046 - 5052
(2018/10/26)
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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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- A Manganese Nanosheet: New Cluster Topology and Catalysis
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While the coordination chemistry of monometallic complexes and the surface characteristics of larger metal particles are well understood, preparations of molecular metallic nanoclusters remain a great challenge. Discrete planar metal clusters constitute nanoscale snapshots of cluster growth but are especially rare owing to the strong preference for three-dimensional structures and rapid aggregation or decomposition. A simple ligand-exchange procedure has led to the formation of a novel heteroleptic Mn6 nanocluster that crystallized in an unprecedented flat-chair topology and exhibited unique magnetic and catalytic properties. Magnetic susceptibility studies documented strong electronic communication between the manganese ions. Reductive activation of the molecular Mn6 cluster enabled catalytic hydrogenations of alkenes, alkynes, and imines.
- Chakraborty, Uttam,Reyes-Rodriguez, Efrain,Demeshko, Serhiy,Meyer, Franc,Jacobi von Wangelin, Axel
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supporting information
p. 4970 - 4975
(2018/03/28)
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- Catalytic cleavage and reformation of ethereal σ-bonds
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Ether-exchange reaction of alkyl aryl ethers with alcohols and thiols via the cleavage of the C(sp2)-O bond is described. Bi(OTf)3 was found to be a most effective catalyst, and etherification of fused-aromatic ethers proceeded efficiently. Monitoring of reactions revealed conceptually new transether-ification between two different ethers, which can be regarded as single-bond metathesis under the same reaction conditions.
- Murai, Masahito,Origuchi, Kazuki,Takai, Kazuhiko
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supporting information
p. 927 - 930
(2018/07/15)
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- Posttreatment technique for SN2 alkylation of aromatics with alkyl halides: Aiming toward large-scale synthesis of building blocks for soft π-molecular materials
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Unreacted alkyl halide and byproduct olefin contaminants in products of SN2 alkylation reactions of aromatic compounds can be efficiently removed by sequential posttreatments with a base and a boron compound (sodium borohydride or 9- borabicyclo[3.3.1]nonane), followed by column chromatography on silica gel. These treatments permit large-scale purification of various alkylated aromatics, thereby assisting in the development of soft π-conjugated materials, such as monomers for semiconducting polymers or alkylated π-functional liquids.
- Okamoto, Ken,Lu, Fengniu,Nakanishi, Takashi
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p. 1258 - 1263
(2018/08/24)
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- Aminopyridine-Borane Complexes as Hydrogen Atom Donor Reagents: Reaction Mechanism and Substrate Selectivity
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Lewis base-borane complexes are shown to be potent hydrogen atom donors in radical chain reduction reactions. Results obtained in 1H, 11B, and 13C NMR measurements and kinetic experiments support a complex reaction mechanism involving the parent borane as well as its initial reaction products as active hydrogen atom donors. Efficient reduction reactions of iodides, bromides, and xanthates in apolar solvents rely on initiator systems generating oxygen-centered radicals under thermal conditions and pyridine-borane complexes carrying solubilizing substituents. In contrast to tin hydride reagents, the pyridine-boranes reduce xanthates faster than the corresponding iodides.
- Barth, Florian,Achrainer, Florian,Pütz, Alexander M.,Zipse, Hendrik
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supporting information
p. 13455 - 13464
(2017/10/05)
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