- On the Mechanism of Reductive Cleavage of the Carbon-Nitrogen Bond of Aliphatic Nitro Compounds with Tributyltin Hydride
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Denitrohydrogenation reaction of aliphatic nitro compounds with tributyltin hydride (Bu3SnH) is accelerated in the presence of radical initiators.ESR and electrochemical measurements reveal that the reductive cleavage of the carbon-nitrogen bond proceeds not via anion radicals of nitro compounds such as SRN1 reaction but via β-scission of (tributylstannyloxy)nitroxyl radicals.The relative reactivities of tin radicals toward substituted α-nitrocumenes, α-nitroethylbenzenes, and α-nitropropiophenones exhibits excellent Hammett correlations with positive ρ values.This tendency has also been found in the reaction of benzyl halides with tin radical.These results suggest that the carbon-nitrogen bond breaking from nitroxyl radical intermediates should take place in rate-determining step for the reaction.
- Kamimura, Akio,Ono, Noboru
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- Large bite bisphosphite, 2,6-C5H3N{CH2OP(-OC10H6)(μ-S)(C10H6O-)}2: Synthesis, derivatization, transition metal chemistry and application towards hydrogenation of olefi
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Large bite bisphosphite ligand, 2,6-C5H3N{CH2OP(-OC10H6)(μ-S)(C10H6O-)}2 (2), is obtained by reacting chlorophosphite, {-OC10H6(μ-S)C10/sub
- Punji, Benudhar,Balakrishna, Maravanji S.
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- Gas-liquid and gas-liquid-solid catalysis in a mesh microreactor
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A microstructured mesh contactor that can offer residence time of more than minutes is used for gas-liquid-solid hydrogenations and gas-liquid asymmetric hydrogenations. Applications for catalyst/chiral inductor screening and for kinetic data acquisition
- Abdallah, Radwan,Meille, Valerie,Shaw, John,Wenn, David,De Bellefon, Claude
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- Mechanistic investigations of imine hydrogenation catalyzed by dinuclear iridium complexes
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Treatment of [Ir2(μ-H)(μ-Pz)2H 3(NCMe)(PiPr3)2] (1) with one equivalent of HBF4 or [PhNH= CHPh]BF4 affords efficient catalysts for the homogeneous hydrogenation of N-benzylidenea
- Martin, Marta,Sola, Eduardo,Tejero, Santiago,Lopez, Jose A.,Oro, Luis A.
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- Effect of Surface Fluorination with CClF3 on Catalytic Activity of SiO2-Al2O3 for Alkylation of Benzene with Propene
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For surface modification, the vapor-phase fluorination of SiO2-Al2O3 with CClF3 was carried out at various temperatures ranging from 350 to 550 deg C in a conventional flow recator.It was found that surface fluorination at about 400 deg C was especially e
- Kurosaki, Akito,Okazaki, Susumu
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- One-step conversion of lignin-derived alkylphenols to light arenes by co-breaking of C-O and C-C bonds
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The conversion of lignin-derived alkylphenols to light arenes by a one-step reaction is still a challenge. A 'shortcut' route to transform alkylphenols via the co-breaking of C-O and C-C bonds is presented in this paper. The catalytic transformation of 4-ethylphenol in the presence of H2 was used to test the breaking of C-O and C-C bonds. It was found that the conversion of 4-ethylphenol was nearly 100%, and the main products were light arenes (benzene and toluene) and ethylbenzene under the catalysis of Cr2O3/Al2O3. The conversion of 4-ethylphenol and the selectivity of the products were significantly influenced by the reaction temperature. The selectivity for light arenes reached 55.7% and the selectivity for overall arenes was as high as 84.0% under suitable reaction conditions. Such results confirmed that the co-breaking of the C-O and C-C bonds of 4-ethylphenol on a single catalyst by one step was achieved with high efficiency. The adsorption configuration of the 4-ethylphenol molecule on the catalyst played an important role in the breaking of the C-O and C-C bonds. Two special adsorption configurations of 4-ethylphenol, including a parallel adsorption and a vertical adsorption, might exist in the reaction process, as revealed by DFT calculations. They were related to the breaking of C-O and C-C bonds, respectively. A path for the hydrogenation reaction of 4-ethylphenol on Cr2O3/Al2O3 was proposed. Furthermore, the co-breaking of the C-O and C-C bonds was also achieved in the hydrogenation reactions of several alkylphenols. This journal is
- Di, Yali,Li, Guangyu,Li, Zhiqin,Liu, Weiwei,Qiu, Zegang,Ren, Xiaoxiong,Wang, Ying
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p. 2710 - 2721
(2022/02/21)
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- Protodesilylation of Arylsilanes by Visible-Light Photocatalysis
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The first visible-light-mediated photocatalytic, metal- and base-free protodesilylation of arylsilanes is presented. The C(sp2)-Si bond cleavage process is catalyzed by a 5 mol % loading of a commercially available acridinium salt upon blue-light irradiation. Two simple approaches have been identified employing either aerobic or hydrogen atom transfer cocatalytic conditions, which enable the efficient and selective desilylation of a broad variety of simple and complex arylsilanes under mild conditions.
- García Manche?o, Olga,Kuhlmann, Jan H.,Uygur, Mustafa
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supporting information
p. 1689 - 1694
(2022/03/14)
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- Radical induced disproportionation of alcohols assisted by iodide under acidic conditions
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The disproportionation of alcohols without an additional reductant and oxidant to simultaneously form alkanes and aldehydes/ketones represents an atom-economical transformation. However, only limited methodologies have been reported, and they suffer from a narrow substrate scope or harsh reaction conditions. Herein, we report that alcohol disproportionation can proceed with high efficiency catalyzed by iodide under acidic conditions. This method exhibits high functional group tolerance including aryl alcohol derivatives with both electron-withdrawing and electron-donating groups, furan ring alcohol derivatives, allyl alcohol derivatives, and dihydric alcohols. Under the optimized reaction conditions, a 49% yield of 5-methyl furfural and a 49% yield of 2,5-diformylfuran were obtained simultaneously from 5-hydroxymethylfurfural. An initial mechanistic study suggested that the hydrogen transfer during this redox disproportionation occurred through the inter-transformation of HI and I2. Radical intermediates were involved during this reaction.
- Huang, Yang,Jiang, Haiwei,Li, Teng,Peng, Yang,Rong, Nianxin,Shi, Hexian,Yang, Weiran
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supporting information
p. 8108 - 8115
(2021/10/29)
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- Ligand-enabled and magnesium-activated hydrogenation with earth-abundant cobalt catalysts
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Replacing expensive noble metals like Pt, Pd, Ir, Ru, and Rh with inexpensive earth-abundant metals like cobalt (Co) is attracting wider research interest in catalysis. Cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. Herein, we describe a hydrogenation method for polycyclic aromatic hydrocarbons (PAHs) and olefins with a magnesium-activated earth-abundant Co catalyst. When diketimine was used as a ligand, simple and inexpensive metal salts of CoBr2in combination with magnesium showed high catalytic activity in the site-selective hydrogenation of challenging PAHs under mild conditions. Co-catalyzed hydrogenation enabled the reduction of two side aromatics of PAHs. A wide range of PAHs can be hydrogenated in a site-selective manner, which provides a cost-effective, clean, and selective strategy to prepare partially reduced polycyclic hydrocarbon motifs that are otherwise difficult to prepare by common methods. The use of well-defined diketimine-ligated Co complexes as precatalysts for selective hydrogenation of PAHs and olefins is also demonstrated.
- Han, Bo,Jiao, Hongmei,Ma, Haojie,Wang, Jijiang,Zhang, Miaomiao,Zhang, Yuqi
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p. 39934 - 39939
(2021/12/31)
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- Reductive activation and hydrofunctionalization of olefins by multiphoton tandem photoredox catalysis
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The conversion of olefin feedstocks to architecturally complex alkanes represents an important strategy in the expedient generation of valuable molecules for the chemical and life sciences. Synthetic approaches are reliant on the electrophilic activation of unactivated olefins, necessitating functionalization with nucleophiles. However, the reductive functionalization of unactivated and less activated olefins with electrophiles remains an ongoing challenge in synthetic chemistry. Here, we report the nucleophilic activation of inert styrenes through a photoinduced direct single electron reduction to the corresponding nucleophilic radical anion. Central to this approach is the multiphoton tandem photoredox cycle of the iridium photocatalyst [Ir(ppy)2(dtbbpy)] PF6, which triggers in situ formation of a high-energy photoreductant that selectively reduces styrene olefinic π bonds to radical anions without stoichiometric reductants or dissolving metals. This mild strategy enables the chemoselective reduction and hydrofunctionalization of styrenes to furnish valuable alkane and tertiary alcohol derivatives. Mechanistic studies support the formation of a styrene olefinic radical anion intermediate and a Birch-type reduction involving two sequential single electron transfers. Overall, this complementary mode of olefin activation achieves the hydrofunctionalization of less activated alkenes with electrophiles, adding value to abundant olefins as valuable building blocks in modern synthetic protocols.
- Czyz, Milena L.,Taylor, Mitchell S.,Horngren, Tyra H.,Polyzos, Anastasios
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p. 5472 - 5480
(2021/06/01)
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- Controlling product selectivity with nanoparticle composition in tandem chemo-biocatalytic styrene oxidation
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The combination of heterogeneous catalysis and biocatalysis into one-pot reaction cascades is a potential approach to integrate enzymatic transformations into existing chemical infrastructure. Peroxygenases, which can achieve clean C-H activation, are ideal candidates for incorporation into such tandem systems, however a constant supply of low-level hydrogen peroxide (H2O2) is required. The use of such enzymes at industrial scale will likely necessitate thein situgeneration of the oxidant from cheap and widely available reactants. We show that combing heterogeneous catalysts (AuxPdy/TiO2) to produce H2O2in situfrom H2and air, in the presence of an evolved unspecific peroxygenase fromAgrocybe aegerita(PaDa-I variant) yields a highly active cascade process capable of oxidizing alkyl and alkenyl substrates. In addition, the tandem process operates under mild reaction conditions and utilizes water as the only solvent. When alkenes such as styrene are subjected to this tandem oxidation process, divergent reaction pathways are observed due to the competing hydrogenation of the alkene by palladium rich nanoparticles in the presence of H2. Each pathway presents opportunities for value added products. Product selectivity was highly sensitive to the rate of reduction compared to hydrogen peroxide delivery. Here we show that some control over product selectivity may be exerted by careful selection of nanoparticle composition.
- Alcalde, Miguel,Brehm, Joseph,Davies, Thomas E.,Freakley, Simon J.,Harrison, Susan T. L.,Hutchings, Graham J.,Kotsiopoulos, Athanasios,Lewis, Richard J.,Morgan, David J.,Opperman, Diederik J.,Smit, Martha S.,Wilbers, Derik,van Marwijk, Jacqueline
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supporting information
p. 4170 - 4180
(2021/06/17)
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- Effect of Binder Content on the Properties of Nanocrystalline Zeolite BEA-based Catalysts for Benzene Alkylation with Propylene
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Abstract: The effect of binder content (aluminum hydroxide) on the textural, acidic, and catalytic properties of nanocrystalline zeolite BEA-based catalysts for the alkylation of benzene with propylene has been studied. It has been shown that increasing binder content increases the volume of mesopores in the sample and decreases the volume of micro- and macropores. Increased binder content in the catalyst primarily results in a decrease in the concentration of weak acid sites, whereas the concentration of strong acid sites changes only slightly. The observed regularity is associated with the reaction of the binder and the zeolite during the preparation of the catalyst, as well as with the formation of new acid sites. It has been found that increasing binder content increases the mechanical strength of the granulated catalyst, but this is accompanied with a decrease of its catalytic activity and stability in the gas-phase alkylation of benzene with propylene. It has been shown that the optimal content of the Al2O3 binder in the catalyst is about 30 wt %. The sample with the optimal binder content has demonstrated a stable on-stream behavior in the liquid-phase reaction that occurred with 99.4 wt % alkylation selectivity, 91.1 wt % cumene selectivity at 100% propylene conversion. [Figure not available: see fulltext.]
- Andriako, E. P.,Bok, T. O.,Ivanova, I. I.
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p. 901 - 907
(2021/08/06)
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- Halogen-Bridged Methylnaphthyl Palladium Dimers as Versatile Catalyst Precursors in Coupling Reactions
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Halogen-bridged methylnaphthyl (MeNAP) palladium dimers are presented as multipurpose Pd-precursors, ideally suited for catalytic method development and preparative organic synthesis. By simply mixing with phosphine or carbene ligands, they are in situ converted into well-defined monoligated complexes. Their catalytic performance was benchmarked against state-of-the-art systems in challenging Buchwald–Hartwig, Heck, Suzuki and Negishi couplings, and ketone arylations. Their use enabled record-setting activities, beyond those achievable by optimization of the ligand alone. The MeNAP catalysts permit syntheses of tetra-ortho-substituted arenes and bulky anilines in near-quantitative yields at room temperature, allow mono-arylations of small ketones, and enable so far elusive cross-couplings of secondary alkyl boronic acids with aryl chlorides.
- Doppiu, Angelino,Goo?en, Lukas J.,Hu, Zhiyong,Pirkl, Nico,Sivendran, Nardana
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supporting information
p. 25151 - 25160
(2021/10/19)
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- Hydrogenation reaction method
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The invention relates to a hydrogenation reaction method, and belongs to the technical field of organic synthesis. The hydrogenation reaction method provided by the invention comprises the following steps: carrying out a hydrogen transfer reaction on a hydrogen acceptor compound, pinacol borane and a catalyst in a solvent in the presence of proton hydrogen, so that the hydrogen acceptor compound is subjected to a hydrogenation reaction; the catalyst is one or more than two of a palladium catalyst, an iridium catalyst and a rhodium catalyst; the hydrogen acceptor compound comprises one or morethan two functional groups of carbon-carbon double bonds, carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogentriple bonds and epoxy. The method is mild in reaction condition, easy to operate, high in yield, short in reaction time, wide in substrate application range, suitable for carbon-carbon double bonds,carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogen triple bonds and epoxy functional groups, good in selectivity and high in reaction specificity.
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Paragraph 0034; 0169-0172
(2020/05/14)
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- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
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A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
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supporting information
p. 4119 - 4129
(2020/08/10)
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- Bidentate NHC-Cobalt Catalysts for the Hydrogenation of Hindered Alkenes
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Herein, we report a series of easily accessible bidentate N-heterocyclic carbene (NHC) cobalt catalysts, which enable the hydrogenation of hindered alkenes under mild conditions. The four-coordinated bidentate NHC-Co(II) complexes were characterized by X-ray diffraction, elemental analysis, ESI-HRMS, and magnetic moment measurements, revealing a distorted-tetrahedral geometry and a high-spin configuration of the metal center. The activity of the in situ formed catalytic system, which was obtained from easily available NHC precursors, CoCl2, and NaHBEt3, was identical with those of well-defined NHC-cobalt catalysts. This highlights the potential utility of this reaction system.
- Wei, Zeyuan,Wang, Yujie,Li, Yibiao,Ferraccioli, Raffaella,Liu, Qiang
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p. 3082 - 3087
(2020/10/02)
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- Understanding the roles of variable Pd(II)/Pd(0) ratio supported on conjugated poly-azobenzene network: From characteristic alteration in properties to their cooperation towards visible-light-induced selective hydrogenation
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Selective hydrogenation of organic functionalities at environmentally benign conditions using visible light is of great industrial and economic significance. Herein we report visible-light-induced rapid, almost quantitative and selective hydrogenation of olefins to respective mono-reduced products using cooperative performance of Pd(0) nanoparticles (NPs) and Pd(II) ions evenly distributed on a newly synthesized conjugated mesoporous poly-azobenzene network. Role of variable Pd(0)/Pd(II) ratio on the properties of polymeric networks and their overall catalytic abilities is critically investigated. This is the first proposed example of cooperative hydrogenation by simultaneous activation of H2 and unsaturated substrates using Mott-Schottky heterojunction between Pd NPs and the semiconducting polymer, with the help of Pd(II)-site-mediated η-coordination. A control over selective mono-reduction of diene with identical double bonds was also obtained. The catalytic activity retained for other non-olefinic functionalities as well.
- Nath, Ipsita,Chakraborty, Jeet,Zhang, Gaoke,Chen, Cheng,Chaemchuen, Somboon,Park, Jihae,Zhuiykov, Serge,Han, Taejun,Verpoort, Francis
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p. 120 - 128
(2020/04/15)
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- Efficient Conversion of Pine Wood Lignin to Phenol
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Obtaining chemical building blocks from biomass is attractive for meeting sustainability targets. Herein, an effective approach was developed to convert the lignin part of woody biomass into phenol, which is a valuable base chemical. Monomeric alkylmethoxyphenols were obtained from pinewood, rich in guaiacol-type lignin, through Pt/C-catalyzed reductive depolymerization. In a second step, an optimized MoP/SiO2 catalyst was used to selectively remove methoxy groups in these lignin monomers to generate 4-alkylphenols, which were then dealkylated by zeolite-catalyzed transalkylation to a benzene stream. The overall yield of phenol based on the initial lignin content in pinewood was 9.6 mol %.
- Boot, Michael D.,Hensen, Emiel J. M.,Huang, Xiaoming,Ouyang, Xianhong
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- Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction
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A number of amines with three bulky alkyl groups at the nitrogen, which surpass the steric crowding of triisopropylamine considerably, were prepared by using different synthetic methods. It turned out that treatment of N-chlorodialkylamines with organometallic compounds, for example, Grignard reagents, in the presence of a major excess of tetramethylenediamine offered the most effective access to the target compounds. The limits of this method were also tested. The trialkylamines underwent a dealkylation reaction, depending on the degree of steric stress, even at ambient temperature. Because olefins were formed in this transformation, it showed some similarity with the Hofmann elimination. However, the thermal decay of sterically overcrowded tertiary amines was not promoted by bases. Instead, this reaction was strongly accelerated by protic conditions and even by trace amounts of water. Reaction mechanisms, which were analyzed with the help of quantum chemical calculations, are suggested to explain the experimental results.
- Banert, Klaus,Hagedorn, Manfred,Heck, Manuel,Hertel, Raphael,Ihle, Andreas,Müller, Ioana,Pester, Tom,Shoker, Tharallah,Rablen, Paul R.
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p. 13630 - 13643
(2020/11/13)
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- Reductive Deamination with Hydrosilanes Catalyzed by B(C6F5)3
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The strong boron Lewis acid tris(pentafluorophenyl)borane B(C6F5)3 is known to catalyze the dehydrogenative coupling of certain amines and hydrosilanes at elevated temperatures. At higher temperature, the dehydrogenation pathway competes with cleavage of the C?N bond and defunctionalization is obtained. This can be turned into a useful methodology for the transition-metal-free reductive deamination of a broad range of amines as well as heterocumulenes such as an isocyanate and an isothiocyanate.
- Fang, Huaquan,Oestreich, Martin
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supporting information
p. 11394 - 11398
(2020/05/25)
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- σ-Bond Hydroboration of Cyclopropanes
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Hydroboration of alkenes is a classical reaction in organic synthesis in which alkenes react with boranes to give alkylboranes with subsequent oxidation resulting in alcohols. The double bond (π-bond) of alkenes can be readily reacted with boranes owing to its high reactivity. However, the single bond (σ-bond) of alkanes has never been reacted. To pursue the development of σ-bond cleavage, we selected cyclopropanes as model substrates since they present a relatively weak σ-bond. Herein, we describe an iridium-catalyzed hydroboration of cyclopropanes, resulting in β-methyl alkylboronates. These unusually branched boronates can be derivatized by oxidation or cross-coupling chemistry, accessing "designer"products that are desired by practitioners of natural product synthesis and medicinal chemistry. Furthermore, mechanistic investigations and theoretical studies revealed the enabling role of the catalyst.
- Arifin,Itami, Kenichiro,Kato, Hiroki,Kobayashi, Chisa,Kondo, Hiroki,Matsushita, Kaoru,Miyamura, Shin,Yamaguchi, Junichiro,Yokogawa, Daisuke
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supporting information
p. 11306 - 11313
(2020/07/13)
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- Transition-Metal-Free Cross-Coupling by Using Tertiary Benzylic Organoboronates
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The transition-metal-free cross-coupling of alkyl or aryl electrophiles by using tertiary benzylic organoboronates is reported. This reaction involves the generation of tertiary alkyl anions from organoboronates in the presence of an alkoxide base and then their substitution reactions. This protocol allows the simple and efficient construction of quaternary carbon centers.
- Takeda, Mitsutaka,Nagao, Kazunori,Ohmiya, Hirohisa
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supporting information
p. 22460 - 22464
(2020/10/12)
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- Method for constructing carbon-hydrogen bond by catalyzing alcohol dehydroxylation with palladium/platinum
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The invention discloses a method for constructing a carbon-hydrogen (deuterium) bond. The method comprises the following step: in the presence of a palladium/platinum catalyst and aryl halide, an alcohol hydroxyl group of an alcohol and hydrogen (deuterium) gas is replaced by hydrogen (deuterium) to construct the carbon-hydrogen (deuterium) bond. According to the method, the palladium/platinum catalyst is used as a catalyst, the green hydrogen (deuterium) gas is used as a hydrogen (deuterium) source, efficient alcohol dehydroxylation is performed at room temperature to construct the carbon-hydrogen (deuterium) bond, and the method is particularly suitable for constructing the carbon-deuterium bond and can be widely applied to synthesis of deuterated drugs.
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Paragraph 0104-0110; 0112
(2019/12/25)
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- Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation
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The dehalogenation-arylation and the hydrodehalogenation of various types of organic halides are selectively realized using AgF and visible light without any organic additives under mild conditions. Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h-1. This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.
- Wu, Wenli,Cui, Enxin,Zhang, Yun,Zhang, Chen,Zhu, Feng,Tung, Chen-Ho,Wang, Yifeng
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p. 6335 - 6341
(2019/07/04)
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- Alkene Transfer Hydrogenation with Alkaline-Earth Metal Catalysts
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The alkene transfer hydrogenation (TH) of a variety of alkenes has been achieved with simple AeN′′2 catalysts [Ae=Ca, Sr, Ba; N′′=N(SiMe3)2] using 1,4-cyclohexadiene (1,4-CHD) as a H source. Reaction of 1,4-CHD with AeN′′2 gave benzene, N′′H, and the metal hydride species N′′AeH (or aggregates thereof), which is a catalyst for alkene hydrogenation. BaN′′2 is by far the most active catalyst. Hydrogenation of activated C=C bonds (e.g. styrene) proceeded at room temperature without polymer formation. Unactivated (isolated) C=C bonds (e.g. 1-hexene) needed a higher temperature (120 °C) but proceeded without double-bond isomerization. The ligands fully control the course of the catalytic reaction, which can be: 1) alkene TH, 2) 1,4-CHD dehydrogenation, or 3) alkene polymerization. DFT calculations support formation of a metal hydride species by deprotonation of 1,4-CHD followed by H transfer. Convenient access to larger quantities of BaN′′2, its high activity and selectivity, and the many advantages of TH make this a simple but attractive procedure for alkene hydrogenation.
- Bauer, Heiko,Thum, Katharina,Alonso, Mercedes,Fischer, Christian,Harder, Sjoerd
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supporting information
p. 4248 - 4253
(2019/03/07)
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- Visible-Light-Driven Photocatalytic Hydrogenation of Olefins Using Water as the H Source
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In this work, a highly efficient PCN-KCl (KCl-modified polymeric carbon nitride) nanosheet photocatalyst was synthesized with the assistance of KCl. The as-prepared PCN-KCl catalyst shows a more than 30-fold enhancement in the photocatalytic activity for H2 evolution from water compared to the pristine PCN. More importantly, when PCN-KCl was composited with a second catalyst (Pd nanoparticles), the simultaneous production and utilization of active H species for alkenes hydrogenation was achieved by visible light irradiation under ambient conditions.
- Fan, Xin,Yao, Yanling,Xu, Yangsen,Yu, Lei,Qiu, Chuntian
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p. 2596 - 2599
(2019/05/10)
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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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- Room Temperature Iron-Catalyzed Transfer Hydrogenation and Regioselective Deuteration of Carbon-Carbon Double Bonds
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An iron catalyst has been developed for the transfer hydrogenation of carbon-carbon multiple bonds. Using a well-defined β-diketiminate iron(II) precatalyst, a sacrificial amine and a borane, even simple, unactivated alkenes such as 1-hexene undergo hydrogenation within 1 h at room temperature. Tuning the reagent stoichiometry allows for semi- and complete hydrogenation of terminal alkynes. It is also possible to hydrogenate aminoalkenes and aminoalkynes without poisoning the catalyst through competitive amine ligation. Furthermore, by exploiting the separate protic and hydridic nature of the reagents, it is possible to regioselectively prepare monoisotopically labeled products. DFT calculations define a mechanism for the transfer hydrogenation of propene with nBuNH2 and HBpin that involves the initial formation of an iron(II)-hydride active species, 1,2-insertion of propene, and rate-limiting protonolysis of the resultant alkyl by the amine N-H bond. This mechanism is fully consistent with the selective deuteration studies, although the calculations also highlight alkene hydroboration and amine-borane dehydrocoupling as competitive processes. This was resolved by reassessing the nature of the active transfer hydrogenation agent: experimentally, a gel is observed in catalysis, and calculations suggest this can be formulated as an oligomeric species comprising H-bonded amine-borane adducts. Gel formation serves to reduce the effective concentrations of free HBpin and nBuNH2 and so disfavors both hydroboration and dehydrocoupling while allowing alkene migratory insertion (and hence transfer hydrogenation) to dominate.
- Espinal-Viguri, Maialen,Neale, Samuel E.,Coles, Nathan T.,MacGregor, Stuart A.,Webster, Ruth L.
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supporting information
p. 572 - 582
(2019/01/08)
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- Regiodivergent hydrosilylation, hydrogenation, [2π + 2π]-cycloaddition and C-H borylation using counterion activated earth-abundant metal catalysis
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The widespread adoption of earth-abundant metal catalysis lags behind that of the second- and third-row transition metals due to the often challenging practical requirements needed to generate the active low oxidation-state catalysts. Here we report the development of a single endogenous activation protocol across five reaction classes using both iron- and cobalt pre-catalysts. This simple catalytic manifold uses commercially available, bench-stable iron- or cobalt tetrafluoroborate salts to perform regiodivergent alkene and alkyne hydrosilylation, 1,3-diene hydrosilylation, hydrogenation, [2π + 2π]-cycloaddition and C-H borylation. The activation protocol proceeds by fluoride dissociation from the counterion, in situ formation of a hydridic activator and generation of a low oxidation-state catalyst.
- Agahi, Riaz,Challinor, Amy J.,Dunne, Joanne,Docherty, Jamie H.,Carter, Neil B.,Thomas, Stephen P.
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p. 5079 - 5084
(2019/05/24)
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- Cobalt-Catalyzed Hydrogenations via Olefin Cobaltate and Hydride Intermediates
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Redox noninnocent ligands are a promising tool to moderate electron transfer processes within base-metal catalysts. This report introduces bis(imino)acenaphthene (BIAN) cobaltate complexes as hydrogenation catalysts. Sterically hindered trisubstituted alkenes, imines, and quinolines underwent clean hydrogenation under mild conditions (2-10 bar, 20-80 °C) by use of the stable catalyst precursor [(DippBIAN)CoBr2] and the cocatalyst LiEt3BH. Mechanistic studies support a homogeneous catalysis pathway involving alkene and hydrido cobaltates as active catalyst species. Furthermore, considerable reaction acceleration by alkali cations and Lewis acids was observed. The dinuclear hydridocobaltate anion with bridging hydride ligands was isolated and fully characterized.
- Sandl, Sebastian,Maier, Thomas M.,Van Leest, Nicolaas P.,Kr?ncke, Susanne,Chakraborty, Uttam,Demeshko, Serhiy,Koszinowski, Konrad,De Bruin, Bas,Meyer, Franc,Bodensteiner, Michael,Herrmann, Carmen,Wolf, Robert,Von Jacobi Wangelin, Axel
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p. 7596 - 7606
(2019/08/20)
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- Manganese-Catalyzed Acceptorless Dehydrogenative Coupling of Alcohols with Sulfones: A Tool to Access Highly Substituted Vinyl Sulfones
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The development of first-row-transition-metal catalysts that can match with the reactivities of the noble metals is considered to be challenging yet very much a desirable goal in homogeneous catalysis. It has become even more fascinating to develop processes where these metals show a unique reactivity and selectivity than their higher congeners. Herein, we report on the catalytic activity of a pincer complex of the abundant earth metal manganese for an unprecedented acceptorless dehydrogenative coupling of alkyl sulfones with alcohols. Thus, highly functionalized vinyl sulfones were obtained in moderate to good yields. Both benzylic and aliphatic alcohols could be utilized, and several functional groups including bromides and iodides are tolerated under the reaction conditions. The reaction is environmentally benign, producing dihydrogen and water as byproducts. Preliminary mechanistic experiments involving kinetic, deuterium-labeling, and NMR experiments were performed.
- Barman, Milan K.,Maji, Biplab,Waiba, Satyadeep
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p. 973 - 982
(2021/08/24)
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- Electrochemical Hydrogenation with Gaseous Ammonia
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As a carbon-free and sustainable fuel, ammonia serves as high-energy-density hydrogen-storage material. It is important to develop new reactions able to utilize ammonia as a hydrogen source directly. Herein, we report an electrochemical hydrogenation of alkenes, alkynes, and ketones using ammonia as the hydrogen source and carbon electrodes. A variety of heterocycles and functional groups, including for example sulfide, benzyl, benzyl carbamate, and allyl carbamate were well tolerated. Fast stepwise electron transfer and proton transfer processes were proposed to account for the transformation.
- Li, Jin,He, Lingfeng,Liu, Xu,Cheng, Xu,Li, Guigen
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supporting information
p. 1759 - 1763
(2019/01/16)
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- The synthesis of hierarchical high-silica beta zeolites in NaF media
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An aerosol-assisted hydrothermal method has been applied to synthesizing hierarchical beta zeolites with SiO2/Al2O3 ratios ranging from 44 to 392 in NaF media. Two different morphologies, including nano-aggregates with interparticle mesopores and plate-like zeolites with intracrystalline mesopores, can be formed depending on the SiO2/Al2O3 ratios of the synthesis gels. A possible mechanism for the formation of the beta zeolites has been proposed. The obtained beta zeolites show hierarchical pores, good Al species distribution and less internal defect sites. Evaluation, by the cracking of 1,3,5-triisopropylbenzene (1,3,5-TIPB), is consistent with the acidic properties and the pore structure of beta zeolites with different ratios of SiO2/Al2O3.
- Xiong, Guang,Feng, Miaomiao,Liu, Jiaxu,Meng, Qingrun,Liu, Liping,Guo, Hongchen
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p. 3653 - 3660
(2019/02/10)
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- Hindered dialkyl ether synthesis with electrogenerated carbocations
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Hindered ethers are of high value for various applications; however, they remain an underexplored area of chemical space because they are difficult to synthesize via conventional reactions1,2. Such motifs are highly coveted in medicinal chemistry, because extensive substitution about the ether bond prevents unwanted metabolic processes that can lead to rapid degradation in vivo. Here we report a simple route towards the synthesis of hindered ethers, in which electrochemical oxidation is used to liberate high-energy carbocations from simple carboxylic acids. These reactive carbocation intermediates, which are generated with low electrochemical potentials, capture an alcohol donor under non-acidic conditions; this enables the formation of a range of ethers (more than 80 have been prepared here) that would otherwise be difficult to access. The carbocations can also be intercepted by simple nucleophiles, leading to the formation of hindered alcohols and even alkyl fluorides. This method was evaluated for its ability to circumvent the synthetic bottlenecks encountered in the preparation of 12 chemical scaffolds, leading to higher yields of the required products, in addition to substantial reductions in the number of steps and the amount of labour required to prepare them. The use of molecular probes and the results of kinetic studies support the proposed mechanism and the role of additives under the conditions examined. The reaction manifold that we report here demonstrates the power of electrochemistry to access highly reactive intermediates under mild conditions and, in turn, the substantial improvements in efficiency that can be achieved with these otherwise-inaccessible intermediates.
- Xiang, Jinbao,Shang, Ming,Kawamata, Yu,Lundberg, Helena,Reisberg, Solomon H.,Chen, Miao,Mykhailiuk, Pavel,Beutner, Gregory,Collins, Michael R.,Davies, Alyn,Del Bel, Matthew,Gallego, Gary M.,Spangler, Jillian E.,Starr, Jeremy,Yang, Shouliang,Blackmond, Donna G.,Baran, Phil S.
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p. 398 - 402
(2019/11/05)
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- Surface Modification of a Supported Pt Catalyst Using Ionic Liquids for Selective Hydrodeoxygenation of Phenols into Arenes under Mild Conditions
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The selective and efficient removal of oxygenated groups from lignin-derived phenols is a critical challenge to utilize lignin as a source for renewable aromatic chemicals. This report describes how surface modification of a zeolite-supported Pt catalyst using ionic liquids (ILs) remarkably increases selectivity for the hydrodeoxygenation (HDO) of phenols into arenes under mild reaction conditions using atmospheric pressure H2. Unmodified Pt/H-ZSM-5 converts phenols into aliphatic species as the major products along with a slight amount of arenes (10 % selectivity). In contrast, the catalyst modified with an IL, 1-butyl-3-methylimidazolium triflate, keeps up to 76 % selectivity for arenes even at a nearly complete conversion of phenols. The IL on the surface of Pt catalyst may offer the adsorption of phenols in an edge-to-face manner onto the surface, thus accelerating the HDO without the ring hydrogenation.
- Ohta, Hidetoshi,Tobayashi, Kanako,Kuroo, Akihiro,Nakatsuka, Mao,Kobayashi, Hirokazu,Fukuoka, Atsushi,Hamasaka, Go,Uozumi, Yasuhiro,Murayama, Haruno,Tokunaga, Makoto,Hayashi, Minoru
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supporting information
p. 14762 - 14766
(2019/11/13)
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- Ru/hydroxyapatite as a dual-functional catalyst for efficient transfer hydrogenolytic cleavage of aromatic ether bonds without additional bases
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Cleavage of aromatic ether bonds is a key step for lignin valorization, and the development of novel heterogeneous catalysts with high activity is crucial. Herein, bifunctional Ru/hydroxyapatite has been prepared via ion exchange and subsequent reduction. The obtained Ru/hydroxyapatite could efficiently catalyze the cleavage of various compounds containing aromatic ether bonds via transfer hydrogenolysis without additional bases. Systematic studies indicated that the basic nature of hydroxyapatite and electron-enriched Ru sites resulted in the high activity of the catalyst. A mechanism study revealed that the direct cleavage of aromatic ether bonds was the main reaction pathway.
- Hua, Manli,Song, Jinliang,Xie, Chao,Wu, Haoran,Hu, Yue,Huang, Xin,Han, Buxing
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p. 5073 - 5079
(2019/09/30)
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- COBALT COMPLEXES, PROCESS FOR PREPARATION AND USE THEREOF
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The present invention discloses a cobalt compound of formula (I), a process for the preparation and use thereof. The present invention further relates to a pharmaceutical composition and a method inhibition of Tau Aggregation in a subject in need thereof using compound of formula (I).
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-
Page/Page column 17; 18
(2019/01/06)
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- Selective Hydrogenations and Dechlorinations in Water Mediated by Anionic Surfactant-Stabilized Pd Nanoparticles
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We report a facile, inexpensive, and green method for the preparation of Pd nanoparticles in aqueous medium stabilized by anionic sulfonated surfactants sodium 1-dodecanesulfonate 1a, sodium dodecylbenzenesulfonate 1b, dioctyl sulfosuccinate sodium salt 1c, and poly(ethylene glycol) 4-nonylphenyl-3-sulfopropyl ether potassium salt 1d simply obtained by stirring aqueous solutions of Pd(OAc)2 with the commercial anionic surfactants further treated under hydrogen atmosphere for variable amounts of time. The aqueous Pd nanoparticle solutions were tested in the selective hydrogenation reactions of aryl-alcohols, -aldehydes, and -ketones, leading to complete conversion to the deoxygenated products even in the absence of strong Br?nsted acids in the reduction of aromatic aldehydes and ketones, in the controlled semihydrogenation of alkynes leading to alkenes, and in the efficient hydrodechlorination of aromatic substrates. In all cases, the micellar media were crucial for stabilizing the metal nanoparticles, dissolving substrates, steering product selectivity, and enabling recycling. What is interesting is also that a benchmark catalyst like Pd/C can often be surpassed in activity and/or selectivity in the reactions tested by simply switching to the appropriate commercially available surfactant, thereby providing an easy to use, flexible, and practical catalytic system capable of efficiently addressing a variety of synthetically significant hydrogenation reactions.
- La Sorella, Giorgio,Sperni, Laura,Canton, Patrizia,Coletti, Lisa,Fabris, Fabrizio,Strukul, Giorgio,Scarso, Alessandro
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supporting information
p. 7438 - 7446
(2018/05/29)
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- Hydrogenolysis of C?O Chemical Bonds of Broad Scope Mediated by a New Spherical Sol–Gel Catalyst
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The new spherical sol–gel hybrid material SiliaCat Pd0 selectively mediates the hydrogenolysis of aromatic alcohols, aldehydes, and ketones by using an ultralow catalytic amount (0.1 mol % Pd) under mild reaction conditions. The broad reaction scope as well as the catalyst's superior activity and pronounced stability open the route to green and convenient reductive deoxygenation processes of primary synthetic relevance in chemical research as well as in the fine chemical and petrochemical industries.
- Pandarus, Valerica,Ciriminna, Rosaria,Gingras, Geneviève,Béland, Fran?ois,Pagliaro, Mario,Kaliaguine, Serge
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- Homogeneous Palladium-Catalyzed Transfer Hydrogenolysis of Benzylic Alcohols Using Formic Acid as Reductant
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We report the first homogeneous palladium-based transfer hydrogenolysis of benzylic alcohols using an in situ formed palladium-phosphine complex and formic acid as reducing agent. The reaction requires a catalyst loading as low as only 1 mol % of palladium and just a slight excess of reductant to obtain the deoxygenated alkylarenes in good to excellent yields. Besides demonstrating the broad applicability for primary, secondary and tertiary benzylic alcohols, a reaction intermediate could be identified. Additionally, it could be shown that partial oxidation of the applied phosphine ligand was beneficial for the course of the reaction, presumably by stabilizing the active catalyst. Reaction profiles and catalyst poisoning experiments were used to characterize the catalyst, the results of which indicate a homogeneous metal complex as the active species.
- Ciszek, Benjamin,Fleischer, Ivana
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supporting information
p. 12259 - 12263
(2018/08/28)
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- Method for preparing isopropylbenzene through catalytic hydrogenolysis of alpha,alpha-dimethyl-benzyl carbinol
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The invention discloses a method for preparing isopropylbenzene through catalytic hydrogenolysis of alpha,alpha-dimethyl-benzyl carbinol. According to the method, an NiB-Zn/ZIF-8 catalyst is adopted,alpha,alpha-dimethyl-benzyl carbinol and hydrogen are taken as the raw materials, the molar ratio of raw material gas/nitrogen is 1 to 15, the molar ratio of hydrogen/alpha,alpha-dimethyl-benzyl carbinol is 5 to 1, and under the condition that the reaction temperature is 120 DEG C, the reaction pressure is 0.5MPa and the volume velocity of inert carrier gas is 3.0h, the conversion rate of alpha,alpha-dimethyl-benzyl carbinol is 100%, and the selectivity of isopropylbenzene is over 96.8%, so that a relatively technical effect is achieved, the product is easy to separate, the after-treatmentis simple, and the catalyst can be recycled for repeated use.
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Paragraph 0028; 0033; 0034; 0035; 0040; 0041; 0042; 0048
(2019/01/05)
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- Olefin-Stabilized Cobalt Nanoparticles for C=C, C=O, and C=N Hydrogenations
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The development of cobalt catalysts that combine easy accessibility and high selectivity constitutes a promising approach to the replacement of noble-metal catalysts in hydrogenation reactions. This report introduces a user-friendly protocol that avoids complex ligands, hazardous reductants, special reaction conditions, and the formation of highly unstable pre-catalysts. Reduction of CoBr2 with LiEt3BH in the presence of alkenes led to the formation of hydrogenation catalysts that effected clean conversions of alkenes, carbonyls, imines, and heteroarenes at mild conditions (3 mol % cat., 2–10 bar H2, 20–80 °C). Poisoning studies and nanoparticle characterization by TEM, EDX, and DLS supported the notion of a heterotopic catalysis mechanism.
- Sandl, Sebastian,Schwarzhuber, Felix,P?llath, Simon,Zweck, Josef,Jacobi von Wangelin, Axel
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supporting information
p. 3403 - 3407
(2018/02/13)
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- Hierarchical MFI Zeolites with a Single-Crystalline Sponge-Like Mesostructure
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Single-crystalline sponge-like MFI mesoporous zeolites (SSMZs) have been synthesized by using bolaform surfactants with an axial chiral binaphthyl core in the hydrophobic tail and triquaternary ammonium head groups, as bifunctional organic structure-directing agents (OSDAs). By changing the length of alkyl chain between a triquaternary ammonium head group and a binaphthyl group from 4 to 10 carbons, SSMZs with high specific surface area (382–434 m2 g?1), abundant micropore-mesopore connectivity, and uniform mesopore diameter (4–10 nm) were obtained. OSDAs with an alkyl chain length of 11 and 12 carbons led to the formation of nanorod-constructed mesoporous MFI zeolites. A geometrical matching between the cylindrical arrangement of the binaphthyl groups and the zeolitic framework is speculated to be the key factor for the formation of mesoporous zeolites. The SSMZ zeolites, with abundant mesopores beneficial for the diffusion of reactants, exhibited significantly higher catalytic efficiencies than those of the conventional ZSM-5 with a microcrystal morphology (≈1.5 μm).
- Zhang, Yunjuan,Luo, Peng,Xu, Hao,Han, Lu,Wu, Peng,Sun, Huai,Che, Shunai
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supporting information
p. 19300 - 19308
(2018/11/27)
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- Hydrogenolysis of lignin model compounds into aromatics with bimetallic Ru-Ni supported onto nitrogen-doped activated carbon catalyst
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Lignin is the most abundant and renewable resources for production of natural aromatics. In this paper, new bimetallic catalytic system of Ru and Ni supported onto nitrogen-doped activated carbon (Ru-Ni-AC/N) was developed and its performances on hydrogenolysis of lignin model compounds under mild reaction conditions (1.0 MPa, 230 °C, in aqueous) were investigated. The results indicate that Ru-Ni-AC/N was a highly active, selective and stable catalyst for the conversion of lignin model compounds into aromatics, e.g. phenol, benzene and their derivatives. As verified by BET, XRD, HRTEM, XPS, H2-TPR and ICP-MS, the strong synergistic effects between i) Ru and Ni and ii) metals and N-groups were contributed to its excellent aromatics selectivity. What's more, the introduction of electron rich N atoms on AC was beneficial to the stabilization of metal particles, which greatly enhanced the durability of the catalyst.
- Hu, Yinghui,Jiang, Guangce,Xu, Guoqiang,Mu, Xindong
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p. 316 - 326
(2018/01/05)
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- Rapid Access to Ortho-Alkylated Vinylarenes from Aromatic Acids by Dearomatization and Tandem Decarboxylative C-H Olefination/Rearomatization
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A two-step straightforward method for the preparation of ortho-alkylated vinylarenes from readily available benzoic acids is described. The synthetic route involves the dearomatization of benzoic acids by Birch reduction providing alkylated cyclohexa-2,5-dienyl-1-carboxylic acids. The diene subsequently undergoes a decarboxylative C-H olefination followed by rearomatization to deliver ortho-alkylated vinylarene. Mechanistic studies suggest that a Pd/Ag bimetallic catalytic system is important in the tandem decarboxylative C-H olefination/rearomatization step.
- Tsai, Hung-Chang,Huang, Yen-Hsiang,Chou, Chih-Ming
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p. 1328 - 1332
(2018/03/09)
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- Design and application of hybrid phosphorus ligands for enantioselective Rh-Catalyzed anti-markovnikov hydroformylation of unfunctionalized 1,1-disubstituted Alkenes
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A series of novel hybrid phosphorus ligands were designed and applied to the Rh-catalyzed enantioselective anti-Markovnikov hydroformylation of unfunctionalized 1,1-disubstituted alkenes. By employing the new catalyst, linear aldehydes with β-chirality can be prepared with high yields and enantioselectivities under mild conditions. Furthermore, catalyst loading as low as 0.05 mol % furnished the desired product in good yield and undiminished selectivity, demonstrating the efficiency of this transformation in large-scale synthesis.
- You, Cai,Li, Shuailong,Li, Xiuxiu,Lan, Jialing,Yang, Yuhong,Chung, Lung Wa,Lv, Hui,Zhang, Xumu
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supporting information
p. 4977 - 4981
(2018/04/24)
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- Cathodic reductive couplings and hydrogenations of alkenes and alkynes catalyzed by the B12 model complex
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The reductive coupling and hydrogenation of alkenes were catalyzed by the B12 model complex, heptamethyl cobyrinate perchlorate (1), in the presence of acid during electrolysis at??0.7?V vs. Ag/AgCl in acetonitrile. Conjugated alkenes showed a good reactivity during electrolysis to form reduced products. The product distributions were dependent on the substituents at the C[dbnd]C bond of the alkenes. ESR spin-trapping experiments using 5,5-dimethylpyrroline N-oxide (DMPO) revealed that the cobalt-hydrogen complex (Co–H complex) should be formed during the electrolysis and it functioned as an intermediate for the alkene reduction. The electrolysis was also applied to an alkyne, such as phenylacetylene, to form 2,3-diphenylbutane (racemic and meso) and ethylbenzene via styrene as reductive coupling and hydrogenated products, respectively.
- Shimakoshi, Hisashi,Luo, Zhongli,Tomita, Kazuya,Hisaeda, Yoshio
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- Catalytic Synthesis of “Super” Linear Alkenyl Arenes Using an Easily Prepared Rh(I) Catalyst
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Linear alkyl benzenes (LAB) are global chemicals that are produced by acid-catalyzed reactions that involve the formation of carbocationic intermediates. One outcome of the acid-based catalysis is that 1-phenylalkanes cannot be produced. Herein, it is reported that [Rh(μ-OAc)(η2-C2H4)2]2 catalyzes production of 1-phenyl substituted alkene products via oxidative arene vinylation. Since C C bonds can be used for many chemical transformations, the formation of unsaturated products provides a potential advantage over current processes that produce saturated alkyl arenes. Conditions that provide up to a 10:1 linear:branched ratio have been achieved, and catalytic turnovers >1470 have been demonstrated. In addition, electron-deficient and electron-rich substituted benzenes are successfully alkylated. The Rh catalysis provides ortho:meta:para selectivity that is opposite to traditional acid-based catalysis.
- Webster-Gardiner, Michael S.,Chen, Junqi,Vaughan, Benjamin A.,McKeown, Bradley A.,Schinski, William,Gunnoe, T. Brent
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p. 5474 - 5480
(2017/04/27)
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- Nickel-Catalyzed Decarbonylation of Aromatic Aldehydes
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We report here the first systematic study of nickel-catalyzed decarbonylation of aromatic aldehydes under relatively mild conditions. Aldehydes with electron donating groups at para and ortho positions are generally successful with our method. For aldehydes with electron-withdrawing groups, significantly higher yields were achieved for ortho-substituted substrates than para ones, probably due to the effects of steric hindrance or electron donors at the ortho position to suppress the Tishchenko reaction, an undesirable side reaction toward homocoupled esters.
- Ding, Keying,Xu, Shi,Alotaibi, Rajeh,Paudel, Keshav,Reinheimer, Eric W.,Weatherly, Jessie
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p. 4924 - 4929
(2017/05/12)
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- Three Different Reactions, One Catalyst: A Cu(I) PNP Pincer Complex as Catalyst for C-C and C-N Cross-Couplings
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An air-stable, thermally robust, and well-defined Cu(I) PNP pincer complex based on the 2,6-diaminopyridine scaffold is described. This complex is an active catalyst for the cross-couplings of a range of aryl and heteroaryl (including benzoxazole, thiazole, pyridine, and thiophene) halides with different organomagnesium reagents, alkynes, and aryl-amines giving excellent to good isolated yields.
- Mastalir, Matthias,Pittenauer, Ernst,St?ger, Berthold,Allmaier, Günter,Kirchner, Karl
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supporting information
p. 2178 - 2181
(2017/04/28)
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- A triazine-based Ni(II) PNP pincer complex as catalyst for Kumada–Corriu and Negishi cross-coupling reactions
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Abstract: Kumada–Corriu and Negishi cross-coupling reactions, catalyzed efficiently by a Ni(II) PNP pincer complex containing a triazine backbone, are described. The catalyst is able to react with both activated and inactivated aryl halides including chlorides as well as phenol derivatives such as tosylates and mesylates to give the corresponding cross-coupling products in good to excellent isolated yields. A high diversity of substrates was tested under moderate conditions for both types of reactions. Graphical Abstract: [Figure not available: see fulltext.]
- Mastalir, Mathias,Kirchner, Karl
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p. 105 - 109
(2017/01/17)
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- Hydrodehalogenation of Haloarenes by a Sodium Hydride–Iodide Composite
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A simple protocol for hydrodebromination and -deiodination of halo(hetero)arenes was enabled by sodium hydride (NaH) in the presence of lithium iodide (LiI). Mechanistic studies showed that an unusual concerted nucleophilic aromatic substitution operates in the present process.
- Ong, Derek Yiren,Tejo, Ciputra,Xu, Kai,Hirao, Hajime,Chiba, Shunsuke
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supporting information
p. 1840 - 1844
(2017/02/05)
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- Construction of Acid–Base Synergetic Sites on Mg-bearing BEA Zeolites Triggers the Unexpected Low-Temperature Alkylation of Phenol
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Novel Mg-bearing BEA zeolites are synthesized to simultaneously endow significantly enhanced basicity without compromising acidity over the zeolite framework. Serving as efficient solid acid–base bifunctional catalysts, they achieve the liquid-phase selective methylation of phenol with methanol to produce o- and p-cresol (o/p=2) under mild conditions. The method is readily extendable to the alkylation of phenols with various alcohols. Stereo- and regioselectivity (>95 % for p-product) was attained on the alkylation of phenol with bulky tert-butyl alcohol, rendering the first acid–base cooperative shape-selective catalysis relying on the basicity of zeolites. A preliminary mechanistic analysis reveals that the remarkable activity and shape-selectivity come from the superior special acidic–basic synergetic catalytic sites on the uniform microporous channels of the BEA zeolite.
- Xie, Jingyan,Zhuang, Wenxia,Zhang, Wei,Yan, Ning,Zhou, Yu,Wang, Jun
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p. 1076 - 1083
(2017/03/27)
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- PROCESS FOR MAKING CUMENE BY ALKYLATION OF BENZENE USING AN ORGANOTEMPLATE-FREE ZEOLITE BETA
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A process for making cumene by the alkylation of benzene with propylene using a benzene alkylation catalyst that comprises an organotemplate-free zeolite beta having a silica-to-alumina molar ratio of less than 20 and synthesized without an organic structure directing agent (SDA).
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Paragraph 0079
(2017/04/23)
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