- Phosphorus and nitrogen-doped palladium nanomaterials support on coral-like carbon materials as the catalyst for semi-hydrogenation of phenylacetylene and mechanism study
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In this work, two types of polyporous and coral-like materials (CN) with high specific surface area are prepared using sodium glutamate as a carrier. At the same time, a CN-supported phosphorus-nitrogen-doped palladium nanomaterial CN-P-Pd is synthesized and applied to the preparation of styrene by selective hydrogenation of phenylacetylene under mild conditions. As shown in the TEM images, Pd nanoparticles with a particle size of about 4.4 nm are uniformly dispersed on the surface of the carrier. The results of N2 adsorption–desorption reveal that the surface area of the prepared catalyst (CN-P-Pd) is 1307 m2g?1. In addition, the experimental exploration shows the intervention of P in carbon-nitrogen materials can contribute to improve the selectivity of the reaction, which can be attributed to the fact that P element can change the electron density of Pd. Meanwhile, it is found that the solvent not only affects the activity of catalyst, but also the selectivity of the reaction. Kinetic study shows the activation energy of the reaction is 4.5 kJ/mol. With the increase of the reaction temperature, the dissolution rate of hydrogen in the solvent gradually slows down, which inhibits the progress of the reduction reaction. Mechanistic studies demonstrate that the carbon-nitrogen materials have strong adsorption capacity for substrates, and also provide more adsorption sites for phenylacetylene. Additionally, the optimal catalyst (CN-P-Pd) also has high reaction activity to other alkynes and the conversion can reach at 95%. Moreover, the optimal catalyst can be reused several times without significant reduction in reaction activity.
- Ma, Lei,Jiang, Pengbo,Wang, Kaizhi,Lan, Kai,Huang, Xiaokang,Yang, Ming,Gong, Li,Jia, Qi,Mu, Xiao,Xiong, Yucong,Li, Rong
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- Precursor Nuclearity and Ligand Effects in Atomically-Dispersed Heterogeneous Iron Catalysts for Alkyne Semi-Hydrogenation
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Nanostructuring earth-abundant metals as single atoms or clusters of controlled size on suitable carriers opens new routes to develop high-performing heterogeneous catalysts, but resolving speciation trends remains challenging. Here, we investigate the potential of low-nuclearity iron catalysts in the continuous liquid-phase semi-hydrogenation of various alkynes. The activity depends on multiple factors, including the nuclearity and ligand sphere of the metal precursor and their evolution upon interaction with the mesoporous graphitic carbon nitride scaffold. Density functional theory predicts the favorable adsorption of the metal precursors on the scaffold without altering the nuclearity and preserving some ligands. Contrary to previous observations for palladium catalysts, single atoms of iron exhibit higher activity than larger clusters. Atomistic simulations suggest a central role of residual carbonyl species in permitting low-energy paths over these isolated metal centers.
- Faust Akl, Dario,Ruiz-Ferrando, Andrea,Fako, Edvin,Hauert, Roland,Safonova, Olga,Mitchell, Sharon,López, Núria,Pérez-Ramírez, Javier
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p. 3247 - 3256
(2021/05/31)
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- Chemoselective Electrochemical Hydrogenation of Ketones and Aldehydes with a Well-Defined Base-Metal Catalyst
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Hydrogenation reactions are fundamental functional group transformations in chemical synthesis. Here, we introduce an electrochemical method for the hydrogenation of ketones and aldehydes by in situ formation of a Mn-H species. We utilise protons and electric current as surrogate for H2 and a base-metal complex to form selectively the alcohols. The method is chemoselective for the hydrogenation of C=O bonds over C=C bonds. Mechanistic studies revealed initial 3 e? reduction of the catalyst forming the steady state species [Mn2(H?1L)(CO)6]?. Subsequently, we assume protonation, reduction and internal proton shift forming the hydride species. Finally, the transfer of the hydride and a proton to the ketone yields the alcohol and the steady state species is regenerated via reduction. The interplay of two manganese centres and the internal proton relay represent the key features for ketone and aldehyde reduction as the respective mononuclear complex and the complex without the proton relay are barely active.
- Fokin, Igor,Siewert, Inke
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p. 14137 - 14143
(2020/10/12)
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- An Annelated Mesoionic Carbene (MIC) Based Ru(II) Catalyst for Chemo- And Stereoselective Semihydrogenation of Internal and Terminal Alkynes
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The catalytic utility of [RuL1(CO)2I2] (1), containing an annelated π-conjugated imidazo-naphthyridine-based mesoionic carbene (MIC) ligand (L1), is evaluated for E-selective alkyne semihydrogenation. The precatalyst 1, in combination with 2 equiv of AgBArF, semihydrogenates a broad range of internal alkynes with molecular hydrogen (5 bar) in water. (E)-Alkenes are accessed in high yields, and a number of reducible functional groups are tolerated. A chelate MIC ligand and two cis carbonyls provide a well-defined platform at the Ru center for hydrogenation and isomerization. The loss of two iodides and the presence of two carbonyls render the Ru center electron deficient and thus the formation of metal vinylidenes with terminal alkynes is avoided. This is leveraged for the semihydrogenation of terminal alkynes by the same catalytic system in isopropyl alcohol. Reaction profile, isomerization, kinetic, and DFT studies reveal initial alkyne hydrogenation to a (Z)-alkene, which further isomerizes to an (E)-alkene via metal-catalyzed Z → E isomerization.
- Bera, Jitendra K.,Choudhury, Joyanta,Das, Shubhajit,Dutta, Indranil,Pati, Swapan K.,Saha, Sayantani,Yadav, Suman
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p. 3212 - 3223
(2020/10/02)
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- Fast and Selective Semihydrogenation of Alkynes by Palladium Nanoparticles Sandwiched in Metal–Organic Frameworks
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The semihydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry. Unfortunately, state-of-the-art heterogeneous catalysts hardly achieve high turnover frequencies (TOFs) simultaneously with almost full conversion, excellent selectivity, and good stability. Here, we used metal–organic frameworks (MOFs) containing Zr metal nodes (“UiO”) with tunable wettability and electron-withdrawing ability as activity accelerators for the semihydrogenation of alkynes catalyzed by sandwiched palladium nanoparticles (Pd NPs). Impressively, the porous hydrophobic UiO support not only leads to an enrichment of phenylacetylene around the Pd NPs but also renders the Pd surfaces more electron-deficient, which leads to a remarkable catalysis performance, including an exceptionally high TOF of 13835 h?1, 100 % phenylacetylene conversion 93.1 % selectivity towards styrene, and no activity decay after successive catalytic cycles. The strategy of using molecularly tailored supports is universal for boosting the selective semihydrogenation of various terminal and internal alkynes.
- Choe, Kwanghak,Li, Guodong,Qiu, Xueying,Ri, Myonghak,Shi, Xinghua,Tang, Zhiyong,Wang, Hui,Wang, Yinglong,Xue, Guangxin,Yuan, Yi,Zhao, Wenshi,Zheng, Fengbin
-
supporting information
p. 3650 - 3657
(2020/02/04)
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- Effect of pretreatment conditions on acidity and dehydration activity of CeO2-MeOx catalysts
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A series of MeOx-modified CeO2 (CeO2-MnOx, CeO2-ZnO, CeO2-MgO, CeO2-CaO, and CeO2-Na2O) catalysts were prepared by the impregnation of CeO2 with corresponding metal nitrates. Acidity and oxidation state of cerium were investigated on both oxidized and reduced catalysts by employing Fourier Transform Infrared spectroscopy (FTIR) on adsorbed pyridine and in situ H2-Temperature Programmed Reduction/X-ray Absorption Spectroscopy (H2-TPR/XAS) techniques, respectively. Metal oxide addition tended to alter both type and number of acid sites on ceria. EXAFS data showed a significant difference in NCe-O between unmodified and CeO2-MeOx, suggesting that added MeOx interferes with vacancy formation on ceria during reduction. In comparison with air-pretreated samples, H2-pretreated ones under similar conversion of 1,5 pentanediol exhibited a higher selectivity towards linear alcohols. Alcohol conversion found to correlate with total acidity (i.e., Br?nsted and Lewis). CeO2 benefited from the addition of alkali (Na) or alkaline earth metals (Mg, Ca) by producing unsaturated alcohols.
- Cronauer, Donald C.,Góra-Marek, Kinga,Garcia, Richard,Gnanamani, Muthu Kumaran,Jacobs, Gary,Kropf, A. Jeremy,Marshall, Christopher L.
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- A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene
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A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.
- Lomelí-Rosales, Diego A.,Delgado, Jorge A.,Díaz de los Bernardos, Miriam,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
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supporting information
p. 8321 - 8331
(2019/06/04)
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- Transfer Hydrogenation of Aldehydes, Allylic Alcohols, Ketones, and Imines Using Molybdenum Cyclopentadienone Complexes
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The molybdenum tetraphenylcyclopentadienone complex (C5Ph4O)Mo(CO)3(CH3CN) 1a is an effective precatalyst for the transfer hydrogenation of aldehydes, allylic alcohols, ketones, and imines under mild conditions with either 2-propanol or formic acid as reducing reagent. Mechanistic studies suggest that these molybdenum cyclopentadienone complexes can be reduced to the corresponding hydroxycyclopentadienyl Mo hydrides. These complexes, by virtue of the hydroxyl group on the cyclopentadienyl ligand, are more reactive and chemoselective than the analogous cyclopentadienyl molybdenum complexes for the reduction of ketones, aldehydes, and imines.
- Wu, Weiwei,Seki, Tomohiro,Walker, Katherine L.,Waymouth, Robert M.
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p. 1428 - 1431
(2018/05/23)
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- Cu-Catalyzed Hydroxymethylation of Unactivated Alkyl Iodides with CO To Provide One-Carbon-Extended Alcohols
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We have developed a reductive carbonylation method by which unactivated alkyl iodides can be hydroxymethylated to provide one-carbon-extended alcohol products under Cu-catalyzed conditions. The method is tolerant of alkyl β-hydrogen atoms, is robust towards a wide variety of functional groups, and was applied to primary, secondary, and tertiary alkyl iodide substrates. Mechanistic experiments indicate that the transformation proceeds by atom-transfer carbonylation (ATC) of the alkyl iodide followed in tandem by two CuH-mediated reductions in rapid succession. This radical mechanism renders the Cu-catalyzed system complementary to precious-metal-catalyzed reductive carbonylation reactions.
- Zhao, Siling,Mankad, Neal P.
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supporting information
p. 5867 - 5870
(2018/04/17)
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- Rhenium-catalyzed deoxydehydration of renewable triols derived from sugars
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An efficient method for the catalytic deoxydehydration of renewable triols, including those obtained from 5-HMF, is described. The corresponding unsaturated alcohols were obtained in good yields using simple rhenium(vii)oxide under neat conditions and ambient atmosphere at 165 °C.
- Wozniak, Bartosz,Li, Yuehui,Tin, Sergey,De Vries, Johannes G.
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supporting information
p. 4433 - 4437
(2018/10/17)
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- Dehydration of 1,5-Pentanediol over CeO2-MeOx Catalysts
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The dehydration reaction of 1,5-pentanediol was performed over CeO2 and modified CeO2 (CeO2?MnOx, CeO2?ZnO, CeO2?MgO, CeO2?CaO, CeO2?Na2O) catalysts in a fixed-bed tubular reactor at 350 °C and an atmospheric pressure. The undoped CeO2 produced a mixture of the products containing mainly 4-penten-1-ol, 1-pentanol, cyclopentanol, cyclopentanone and tetrahydropyran-2-one from 1,5-pentanediol, while additions of MgO, MnOx, or ZnO to CeO2 was found to enhance the overall production rate of unsaturated alcohol. On the other hand, more basic metals like CaO or Na2O tend to decline the dehydration activity of CeO2. The porous structure of CeO2 did not change appreciably with the addition of metal oxides. Temperature programmed desorption of adsorbed CO2 on an activated catalyst suggest more CO2 remain on the catalyst surface, particularly CeO2?CaO and CeO2?Na2O indicating that fewer defect sites are only available for reaction. The defect sites or oxygen vacancy on CeO2 controls both activity and selectivity for the dehydration of 1,5-pentanediol.
- Gnanamani, Muthu Kumaran,Martinelli, Michela,Badoga, Sandeep,Hopps, Shelley D.,Davis, Burtron H.
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p. 4629 - 4635
(2018/09/21)
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- [...] 4 - alkenyl - N - furfuryl - N - imidazole -1 - yl carbonyl - DL - high third ammonia ester preparation and bactericidal activity
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The invention belongs to the pesticide create, pathogenic bacteria control technology field, in particular to [...] 4 - alkenyl - N - furfuryl - N - imidazole - 1 - yl carbonyl - DL - high third ammonia ester preparation method of compound and bactericidal activity application. The present invention the use of economic and low-cost method for the first time to realize the deuterium labeled e 4 - alkenyl - N - furfuryl - N - imidazole - 1 - yl carbonyl - DL - high third ammonia ester synthesis. [...] marked e 4 - alkenyl - N - furfuryl - N - imidazole - 1 - yl carbonyl - DL - high third ammonia acid ester structure is novel, and have good in vitro bactericidal activity, in particular donor bacteria, rice virulence has significant inhibition effect. In the kinematically, compared with the C - D key C - H bond is more stable. Therefore, compared with the deuterium-labeled compounds are not, [...] 4 - alkenyl - N - furfuryl - N - imidazole - 1 - yl carbonyl - DL - high third ammonia ester is expected to have longer and more environmentally expiry date of the small pressure. [...] 4 - alkenyl - N - furfuryl - N - imidazole - 1 - yl carbonyl - DL - high third ammonia ester can also be used as a probe to study the metabolism of the compound and toxicological properties. And can be used as a pesticide residue in the internal of the analysis.
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Paragraph 0065; 0070-0072
(2018/09/08)
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- Dehydration of 1,5-Pentanediol over Na-Doped CeO2 Catalysts
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The effects of CeO2 doped with Na on the dehydration of 1,5-pentanediol were studied by using a fixed-bed reactor at two different temperatures (350 and 400 °C) and atmospheric pressure. For characterization, BET surface area, hydrogen temperature-programmed reduction, CO2 temperature-programmed desorption, and diffuse reflectance infrared Fourier transform spectroscopy techniques were utilized. The conversion of the diol on CeO2 was found to depend on Na loading. The selectivity to the desired product (i.e., unsaturated alcohol) increased and the selectivity to undesired products (i.e., tetrahydropyran, tetrahydropyran-2-one, cyclopentanol and cylopentanone) decreased with increasing Na content on CeO2. The basicity of hydroxyl groups or surface oxygen on CeO2 was altered with the addition of Na, and controlled the dehydration reaction pathway.
- Gnanamani, Muthu Kumaran,Jacobs, Gary,Martinelli, Michela,Shafer, Wilson D.,Hopps, Shelley D.,Thomas, Gerald A.,Davis, Burtron H.
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p. 1148 - 1154
(2018/02/12)
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- Adsorptive interaction between 1,5-pentanediol and MgO-modified ZrO2 catalyst in the vapor-phase dehydration to produce 4-penten-1-ol
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Vapor-phase catalytic dehydration of 1,5-pentanediol (1,5-PDO) was investigated over monoclinic ZrO2 catalysts modified with basic oxides. An unsaturated alcohol, 4-penten-1-ol (4P1OL), was produced together with the formation of tetrahydropyran, δ-valerolactone, 1,4-pentadiene, pentanal, 1-pentanol, and 5-hydroxypentanal, etc. Among the modified ZrO2 catalysts, only ZrO2 modified with MgO enhanced the selectivity to 4P1OL efficiently. The most active modified catalyst was found to have 20 mol% MgO and a calcination at 800 °C (MgO/ZrO2), and the selectivity of 4P1OL exceeded 83% at 400 °C. A pulse adsorption measurement of several chemicals clarified adsorptive interaction between a reactant and a catalyst at 220 °C: the interaction between 1,5-PDO and MgO/ZrO2 was stronger than the other adsorbates and catalysts. Another strong adsorptive interaction between 1,4-butanediol and CaO/ZrO2, which was effective in the dehydration of 1,4-butanediol to produce 3-buten-1-ol, was also observed.
- Duan, Hailing,Unno, Masaki,Yamada, Yasuhiro,Sato, Satoshi
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- A Simple and Versatile Approach for the Fabrication of Paper-Based Nanocatalysts: Low Cost, Easy Handling, and Catalyst Recovery
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A versatile method for the preparation of efficient and reusable nanocatalysts involving the painting of a commercial filter paper with a Pd@CNT (CNT=carbon nanotubes) ink was herein explored. The resulting paper-based material provided excellent results in the semihydrogenation of alkynes and alkynols and could be recycled at least five times without loss of activity or selectivity.
- Montiel, Laura,Delgado, Jorge A.,Novell, Marta,Andrade, Francisco J.,Claver, Carmen,Blondeau, Pascal,Godard, Cyril
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p. 3041 - 3044
(2016/10/11)
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- Design of Core-Pd/Shell-Ag Nanocomposite Catalyst for Selective Semihydrogenation of Alkynes
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We designed core-Pd/shell-Ag nanocomposite catalyst (Pd@Ag) for highly selective semihydrogenation of alkynes. The construction of the core-shell nanocomposite enables a significant improvement in the low activity of Ag NPs for the selective semihydrogenation of alkynes because hydrogen is supplied from the core-Pd NPs to the shell-Ag NPs in a synergistic manner. Simultaneously, coating the core-Pd NPs with shell-Ag NPs results in efficient suppression of overhydrogenation of alkenes by the Pd NPs. This complementary action of core-Pd and shell-Ag provides high chemoselectivity toward a wide range of alkenes with high Z-selectivity under mild reaction conditions (room temperature and 1 atm H2). Moreover, Pd@Ag can be easily separated from the reaction mixture and is reusable without loss of catalytic activity or selectivity.
- Mitsudome, Takato,Urayama, Teppei,Yamazaki, Kenji,Maehara, Yosuke,Yamasaki, Jun,Gohara, Kazutoshi,Maeno, Zen,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 666 - 670
(2016/02/18)
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- Palladium Nanoparticles Immobilized on Magnetic Porous Carbon Derived from ZIF-67 as Efficient Catalysts for the Semihydrogenation of Phenylacetylene under Extremely Mild Conditions
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A new magnetic porous carbon (MDPC) derived from metal-organic frameworks (MOFs) was synthesized successfully through the direct carbonization of ZIF-67 crystals and utilized as a support for Pd nanocatalysts. The prepared MDPC not only retains the original morphology of ZIF-67 crystals but also provides a high surface area and excellent magnetic properties. The designed catalysts (Pd-MDPC) were tested in the semihydrogenation of phenylacetylene under extremely mild conditions. The Pd nanoparticles are highly dispersed on the MDPC matrix without aggregation and exhibited an excellent catalytic activity and high selectivity toward olefins under mild conditions (25 °C, H2 1 atm). The Pd-MDPC catalysts were further investigated in the semihydrogenation of several other terminal alkynes. Compared with most traditional carbon materials, such as activated carbon and carbon nanotubes, the MDPC possesses an admirable magnetism so that it could be separated magnetically from the reaction system. Our study indicates that MOF-derived porous carbon is a suitable support for noble-metal nanocatalysts and has promise in the field of nanocatalysis.
- Li, Xinlin,Zhang, Wei,Liu, Yansheng,Li, Rong
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p. 1111 - 1118
(2016/04/05)
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- Chemo-, regio-, and stereoselective hydroboration of conjugated enyne alcohol/amine: Facile synthesis of Z,Z-/Z,E-1,3-dien-1/2-ylboronic ester bearing hydroxyl/amino group
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Hydroboration of conjugated enyne alcohol/amine is studied by using copper salts and bis(pinacolato)diboron as pre-catalysts and boron source respectively. It is suggested that the chemo-selectivity is derived from a combined electronic influence of the heteroatoms on the substrate and the ligand on the transition metal. The regioselectivity is probably dominated mainly by electronic effect of the alkyne substituent. This study resulted in a highly selective protocol to access Z,Z-/Z,E-1,3-dien-1/2-ylboronic ester bearing hydroxyl/amino group.
- Xu, Hua-Dong,Wu, Hao,Jiang, Chun,Chen, Peng,Shen, Mei-Hua
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supporting information
p. 2915 - 2918
(2016/06/14)
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- SELECTIVE OLEFIN METATHESIS WITH CYCLOMETALATED RUTHENIUM COMPLEXES
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This invention relates generally to C—H activated ruthenium olefin metathesis catalyst compounds which are stereogenic at the ruthenium center, to their preparation, and the use of such catalysts in the metathesis of olefins and olefin compounds. In particular, the invention relates to the use of C—H activated ruthenium olefin metathesis catalyst compounds in Z-selective olefin metathesis reactions, enantio-selective olefin metathesis reactions, and enantio-Z-selective olefin metathesis reactions. The invention has utility in the fields of catalysis, organic synthesis, polymer chemistry, and industrial and fine chemicals chemistry.
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- Copper-catalyzed Z-selective semihydrogenation of alkynes with hydrosilane: A convenient approach to cis-alkenes
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A copper catalyst generated in situ from widely available copper salt and imidazolium salt in the presence of t-BuOK showed high efficiency for the semihydrogenation of a wide range of internal and terminal alkynes to their corresponding alkenes without obvious over-reduction. Functional groups, such as hydroxyl, nitro, halides, and amino, etc. were tolerated. The Z/E ratios of the obtained alkenes were generally >99%. Finally, semireduction of bulky alkynes also went smoothly.
- Wang, Guang-Hui,Bin, Huai-Yu,Sun, Miao,Chen, Shu-Wei,Liu, Ji-Hong,Zhong, Chong-Min
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supporting information
p. 2175 - 2179
(2014/03/21)
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- Metal-ligand core-shell nanocomposite catalysts for the selective semihydrogenation of alkynes
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Catalysts with a sheltered upbringing: Novel core-shell nanocomposite catalysts consisting of active metal nanoparticles encapsulated by macroligands have been prepared. They have Pd nanoparticles (PdNPs) as an active core and shell ligands having sulfoxide moieties coordinated to the PdNPs. The shell protects the catalyst from coordination by alkenes and allows the lead-free selective semihydrogenation of a wide range of alkynes without any additives (see scheme). Copyright
- Mitsudome, Takato,Takahashi, Yusuke,Ichikawa, Satoshi,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 1481 - 1485
(2013/04/10)
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- A biocatalytic hydrogenation of carboxylic acids
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The hyperthermophile Pyrococcus furiosus catalyses the hydrogenation of a broad range of carboxylic acids selectively to the corresponding primary alcohols. Other functional groups such as isolated CC-double bonds are not touched. The chemoselectivity of the carboxylate reduction may be directed towards aldehydes by simple medium engineering.
- Ni, Yan,Hagedoorn, Peter-Leon,Xu, Jian-He,Arends, Isabel W. C. E.,Hollmann, Frank
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supporting information
p. 12056 - 12058
(2013/01/16)
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- Iron(III) catalyzed direct synthesis of cis -2,7-disubstituted oxepanes. the shortest total synthesis of (+)-isolaurepan
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Prins cyclization of bis-homoallylic alcohols with aldehydes catalyzed by iron(III) salts shows excellent cis selectivity and yields to form 2,7-disubstituted oxepanes. The iron(III) is able to catalyze this process with unactivated olefins. This cyclization was used as the key step in the shortest total synthesis of (+)-isolaurepan.
- Purino, Martín A.,Ramírez, Miguel A.,Daranas, Antonio H.,Martín, Víctor S.,Padrón, Juan I.
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supporting information
p. 5904 - 5907
(2013/02/25)
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- Dehydration of 1,5-pentanediol over bixbyite Sc2-xYb xO3 catalysts
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Vapor-phase dehydration of 1,4- and 1,5-alkanediols was investigated over three scandium ytterbium mixed oxides, Sc2-xYbxO 3 (x = 0.5, 1.0, and 1.5), to produce the corresponding unsaturated alcohols. In the dehydration of
- Sato, Fumiya,Sato, Satoshi
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p. 129 - 133
(2013/01/13)
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- O-alkyl-N-acyl-N-phenylhydroxylamines as photochemical alkoxy radical precursors
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A simple and efficient technique for the photolysis of alkoxy radical precursors is developed. Irradiation of O-alkyl-N-acyl-N-phenylhydroxylamines, as representative alkoxy radical precursors, with ultraviolet light (254 nm) results in homolytic N-O bond cleavage to generate singlet alkoxy and acylaminyl caged radical pairs. These radicals, depending on the solvent employed, either escape from the cage to form fragmentation products, or undergo in-cage reactions to produce photorearrangement products. The homolytic cleavage of the N-O bond is analyzed using time-dependent density functional theory calculations. The nature of the N-acyl substituent on the O-alkyl-N-acyl-N- phenylhydroxylamines is shown to influence their ability to generate radicals. Furthermore, identification and trapping of the alkoxy radicals is demonstrated. Georg Thieme Verlag Stuttgart · New York.
- Chowdhury, Nilanjana,Anoop, Anakuthil,Singh, N.D. Pradeep
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experimental part
p. 1745 - 1754
(2012/07/27)
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- An eco-sustainable erbium(iii)-catalyzed method for formation/cleavage of O-tert-butoxy carbonates
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A new simple and effective method for the formation/cleavage of O-tert-butoxy carbonates of alcohols and phenols is proposed. Mesoporous silica-supported Er(iii) (ErIII-MCM-41) was used as an efficient and reusable solid catalyst in the solvent-free ultrasound-assisted synthesis of Boc-carbonate derivatives of a wide range of alcohols and phenols. The fast, selective deprotection of Boc-derivatives is achieved with a very low amount of Er(OTf)3 in ethanol under microwave irradiation. Therefore, the entire protection/de-protection process is very attractive, from the point of view of sustainability.
- Procopio, Antonio,Cravotto, Giancarlo,Oliverio, Manuela,Costanzo, Paola,Nardi, Monica,Paonessa, Rosina
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experimental part
p. 436 - 443
(2011/04/17)
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- Mild, selective deprotection of PMB ethers with triflic acid/1,3-dimethoxybenzene
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An efficient method for the cleavage of the p-methoxybenzyl protecting group of several alcohols in the presence of 0.5 equiv of trifluoromethanesulfonic acid and 1,3-dimethoxybenzene in dichloromethane at room temperature is described.
- Jung, Michael E.,Koch, Pierre
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supporting information; experimental part
p. 6051 - 6054
(2011/11/28)
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- An eco-sustainable erbium(III) triflate catalyzed formation and cleavage of tert -butyl ethers
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An eco-compatible method, which permits the formation or cleavage of tert-butyl ethers of alcohols and phenols, is proposed. The protection step is performed in solvent-free conditions at room temperature using catalytic amount of Er(OTf)3. The catalyst is easily- recovered from the aqueous phase and reused several times without significant loss of activity. The deprotection step developed is also highly eco-friendly since the tert-butyl group is removed very quickly from alcohols and phenols in methanol using MW irradiation-. Georg Thieme Verlag Stuttgart · New York.
- Procopio, Antonio,Costanzo, Paola,Curini, Massimo,Nardi, Monica,Oliverio, Manuela,Paonessa, Rosina
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experimental part
p. 73 - 78
(2011/03/19)
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- Total synthesis of the anti-apoptotic agents Iso- And bongkrekic acids
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(Figure presented) The first convergent total synthesis of isobongkrekic acid is reported involving three different stereospecific palladium cross-couplings for the formation of the diene units. Access to bongkrekic acid by this route is also demonstrated. These syntheses involve the formation of several potentially general building blocks.
- Francais, Antoine,Leyva, Antonio,Etxebarria-Jardi, Gorka,Ley, Steven V.
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supporting information; experimental part
p. 340 - 343
(2010/03/25)
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- α-Selective Ni-catalyzed hydroalumination of aryl- and alkyl-substituted terminal alkynes: Practical syntheses of internal vinyl aluminums, halides, or boronates
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A method for Ni-catalyzed hydroalumination of terminal alkynes, leading to the formation of α-vinylaluminum isomers efficiently (>98% conv in 2-12 h) and with high selectivity (95% to >98% α), is described. Catalytic α-selective hydroalumination reactions proceed in the presence of a reagent (diisobutylaluminum hydride; dibal-H) and 3.0 mol % metal complex (Ni(dppp)Cl2) that are commercially available and inexpensive. Under the same conditions, but with Ni(PPh3)2Cl2, hydroalumination becomes highly β-selective, and, unlike uncatalyzed transformations with dibal-H, generates little or no alkynylaluminum byproducts. All hydrometalation reactions are reliable, operationally simple, and practical and afford an assortment of vinylaluminums that are otherwise not easily accessible. The derived α-vinyl halides and boronates can be synthesized through direct treatment with the appropriate electrophiles [e.g., Br 2 and methoxy(pinacolato)boron, respectively]. Ni-catalyzed hydroaluminations can be performed with as little as 0.1 mol % catalyst and on gram scale with equally high efficiency and selectivity.
- Gao, Fang,Hoveyda, Amir H.
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supporting information; experimental part
p. 10961 - 10963
(2010/09/17)
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- Soluble iron nanoparticles as cheap and environmentally benign alkene and alkyne hydrogenation catalysts
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Iron nanoparticles prepared by reducing FeCl3 with three equivalents of EtMgCl in THF are effective catalysts for the hydrogenation of alkenes and alkynes under moderate conditions.
- Phua, Pim-Huat,Lefort, Laurent,Boogers,Tristany, Mar,De Vries, Johannes G.
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supporting information; experimental part
p. 3747 - 3749
(2009/12/01)
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- Method of removing allyl series protecting group using novel ruthenium complex and method of synthesizing allyl ethers
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A cyclopentadienyl ruthenium (II) complex or (iv) complex having an α-imino acid type ligand or an α-amino acid type ligand.
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Page/Page column 4
(2010/02/14)
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- Picolinyl group as an efficient alcohol protecting group: Cleavage with Zn(OAc)2·2H2O under a neutral condition
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As an efficient alcohol protecting group, picolinates (Pic), prepared from the corresponding alcohols using commercial picolinoyl chloride, are readily cleaved by Zn(OAc)2 or Cu(OAc)2, even in the presence of other common alcohol protecting groups. Moreover, the picolinyl group at C-2 position in carbohydrates can be selectively cleaved to give methyl 4,6-O-benzylidene-3-O-picolinyl-α-d-glucopyranoside and 3-O-picolinyl methyl-4,6-O-benzylidene-α-d-galactopyranoside in good yields.
- Ju, Yuel Baek,Shin, Yong-Joo,Heung, Bae Jeon,Kwan, Soo Kim
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p. 5143 - 5147
(2007/10/03)
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- Facile and selective deallylation of allyl ethers using diphosphinidenecyclobutene-coordinated palladium catalysts
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(π-Allyl)palladium triflate bearing a 1,2-bis(4-methoxyphenyl)-3,4- bis(2,4,6-tri-tert-butylphenylphosphinidene)cyclobutene ligand (DPCB-OMe), [Pd(η3-C3H5)(DPCB-OMe)]OTf, efficiently catalyzes deallylation of a variety of allyl ethers in aniline to give corresponding alcohols in high yields under mild conditions. The reactions can be performed in air without loss of a variety of functionalities including vinyl, alkynyl, hydroxy, acetoxy, silyloxy, and acetal groups. Allyl 2-allyloxybenzoate selectively undergoes deallylation of the allyloxy group to give allyl salicylate in quantitative yield.
- Murakami, Hiromi,Minami, Tatsuya,Ozawa, Fumiyuki
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p. 4482 - 4486
(2007/10/03)
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- CpRuIIPF6/quinaldic acid-catalyzed chemoselective allyl ether cleavage. A simple and practical method for hydroxyl deprotection
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Matrix presented. A cationic CpRuII complex in combination with quinaldic acid shows high reactivity and chemoselectivity for the catalytic deprotection of hydroxyl groups protected as allyl ethers. The catalyst operates in alcoholic solvents without the need for any additional nucleophiles, satisfying the practical requirements of operational simplicity, safety, and environmental friendliness. The wide applicability of this deprotection strategy to a variety of multifunctional molecules, including peptides and nucleosides, may provide new opportunities in protective group chemistry.
- Tanaka, Shinji,Saburi, Hajime,Ishibashi, Yoshitaka,Kitamura, Masato
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p. 1873 - 1875
(2007/10/03)
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- The facile preparation of alkenyl metathesis synthons
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We report synthetic methodology allowing the preparation of any length alkenyl halide from inexpensive starting reagents. Standard organic transformations were used to prepare straight chain α-olefin halides in excellent overall yields with no detectable olefin isomerization and full recovery of any unreacted starting material. Reported transformations can be used for the selective incorporation of pure α-olefin metathesis sites in highly functionalized molecules.
- Baughman, Travis W.,Sworen, John C.,Wagener, Kenneth B.
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p. 10943 - 10948
(2007/10/03)
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- Ultrasound-accelerated synthesis of chiral allylic alcohols promoted by indium metal
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The 2-iodomethyl-O-isopropylidine acetals undergo smoothly β-elimination by indium metal in methanol under sonication to afford the corresponding allylic alcohols in excellent yields with high selectivity. This method tolerates both acid and base labile functional and protecting groups and also free hydroxyl groups present in the molecule. Improved yields and enhanced rates are the remarkable features obtained by ultrasound.
- Yadav,Reddy,Srinivasa Reddy
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p. 5333 - 5336
(2007/10/03)
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- Processes for producing unsaturated alcohols
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This invention relates in part to processes for producing one or more substituted or unsubstituted unsaturated alcohols which comprise reacting one or more substituted or unsubstituted alkadienes with carbon monoxide and hydrogen in the presence of a metal-ligand complex catalyst and a promoter and optionally free ligand to produce said one or more substituted or unsubstituted unsaturated alcohols. The substituted and unsubstituted unsaturated alcohols produced by the processes of this invention can undergo further reaction(s) to afford desired derivatives thereof. This invention also relates in part to reaction mixtures containing one or more substituted or unsubstituted unsaturated alcohols as principal product(s) of reaction.
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- Synthesis of C3-C9-alkenyl 2,3-unsaturated glucosides from glucose and some alkenols
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C3-C9-Alkenyl 2,3-unsaturated glucosides have been synthesized from glucose and C3-C9-alkenols by using Ferrier reaction with boron trifluoride etherate (BF3·Et2O) as Lewis acid catalyst in key step.
- Konstantinovic,Predojevic,Gojkovic,Ratkovic,Dimitrijevic,Mojsilovic
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p. 802 - 805
(2007/10/03)
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- Acid-catalyzed cyclization of vinylsilanes bearing a hydroxy group: A new method for stereoselective synthesis of disubstituted tetrahydrofurans
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In the presence of a catalytic amount of TsOH or TiCl4, (Z)-5-silyl-4-penten-1-ols ((Z)-1) are smoothly cyclized to 2-silylmethyl-substituted tetrahydrofurans. This cyclization is applicable to the construction of a tetrahydropyran ring. The silyl group and the geometry of the C-C double bond strongly influence the cychzation rate. TBDMS and benzyldimethylsilyl groups considerably accelerate the cyclization in comparison with a dimethylphenylsilyl group, and (E)-vinylsilanes show much lower reactivity than the corresponding (Z)-isomers. The cyclization proceeds by stereospecific syn addition of the hydroxy group. Vinylsilanes 17, 19, and 21, (Z)-5-silyl-4-penten-1-ols bearing a substituent on the methylene tether, smoothly undergo the acid-catalyzed cyclization to give trans-2,5-, cis-2,4-, and trans-2,3-disubstituted tetrahydrofurans, respectively, with moderate to high stereoselectivity. The silyl group of some cychzed products can be easily converted into a hydroxy group with stereochemical retention.
- Miura,Okajima,Hondo,Nakagawa,Takahashi,Hosomi
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p. 11348 - 11357
(2007/10/03)
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- Synthese d'acides ω perfluoroalkylalcanoiques et d'ω perfluoroalkylalcanols
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The simple and effective syntheses of acids and alcohols of general formula CnF2n+1(CH2)mY (Y=CO2H, CH2OH; n=6,8 and m=4,5) have been described.
- Tra Anh,Blancou,Commeyras
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p. 167 - 174
(2007/10/03)
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- Tetrahydrofuran, tetrahydropyran and oxepane formation by cobaloxime π-cation cyclizations
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Studies are reported on the cyclization of (ω-hydroxy-β-hydroxyalkyl)cobaloximes (1, 2 and 3) to form 5,6 and 7-membered ring cyclic ethers (4, 5 and 6). Reversible cyclization and eventual irreversible alkene decomplexation (to form 7, 8 and 9) varied as a function of ring size. The practical consequence is that cyclizations to form 5 and 6 membered rings are feasible whereas formation of a 7 membered ring is not.
- Grubb, Lana M.,Brown, Katherine A.,Branchaud, Bruce P.
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p. 3447 - 3448
(2007/10/03)
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- One-pot reduction of carboxylic acids via O-acylisoureas
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A simple one-pot reduction of aliphatic carboxylic acids to primary alcohols, by treatment with dicyclohexylcarbodiimide followed by lithium borohydride, is reported. The same methodology applied to aromatic carboxylic acids is shown to give a mixture of the alcohols with N- cyclohexylcarboxamides.
- Herbert, John M.,Hewson, Alan T.,Peace, James E.
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p. 823 - 832
(2007/10/03)
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- Thermal and induced decompositions of N′-alkoxycarbonyldihydropyridines: End product analysis and EPR spectra of azacyclohexadienyl radicals
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Hydrogen abstraction from N-alkoxycarbonyldihydropyridines generated azacyclohexadienyl radicals (pyridinyl radicals) which are characterised by EPR spectroscopy. In the presence of peroxide initiators, N-alkoxycarbonyl-1,2-dihydropyridines decomposed with production of pyridine, the corresponding alkyl formate, alkyl benzoate and alkanol being formed as the major products. Absence of cyclised products in experiments with substrates containing hex-5-enyl, pent-4-enyloxy etc. units demonstrates that radical production must be minor and that N-alkoxycarbonylazacyclohexadienyl radicals do not readily undergo ss-scission of the exocyclic N-C bond. The most probable mechanism is a direct 1,2-elimination of formate. The alcohols which accompanied the other products are probably formed by hydrolysis of the formates and benzoates. Analogous chemistry is displayed by N-alkoxycarbonyl-1,4-dihydropyridines at higher temperatures where 1,4-elimination of formate is too rapid for homolytic radical production to compete.
- Baguley, Paul A.,Walton, John C.
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p. 1423 - 1429
(2007/10/03)
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- Silicon-Directed Cyclization of Vinylsilanes Bearing Hydroxy Group Catalyzed by an Acid
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Silicon-directed stereoselective syn addition of hydroxy group to olefinic double bond occurs intramolecularly in an acid-catalyzed cyclization of vinylsilanes bearing hydroxy group.Thus 5-dimethylphenylsilyl-4-penten-1-ol is smoothly cyclized to 2-(dimethylphenylsilyl)methyltetrahydrofuran upon the treatment of a catalytic amount of p-toluenesulfonic acid (TsOH) or TiCl4.
- Miura, Katsukiyo,Okajima, Shigeo,Hondo, Takeshi,Hosomi, Akira
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p. 1483 - 1486
(2007/10/02)
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- Stereoselective Synthesis of Alcohols containing (Z)- and (E)-Olefins, Dienes, Enynes and Styrenes: Cyclic β-Halogeno Scissions using Samarium Diiodide as the Electron-transfer Agent
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In contrast to the sodium-mediated ring scission of 2-substituted 3-chloro ethers of the tetrahydrofuran series, samarium diiodide gives olefins of high (E)-stereoselectivity and provides (E)-conjugated and unconjugated dienes, styrenes and enynes in good yield without appreciable over-reduction.Whilst the SmI2 scission of 3-chloro-2-alkyltetrahydropyrans gives (Z)-rich (Z)/(E) olefin mixtures, the 2-(alk-1'-ynyl) members give (Z)-enyne alkohols with high stereoselectivity, providing a valuable complement to the (E)-enyne synthesis employing the tetrahydrofuran series.In electron-transfer scissions using sodium, the stereochemistry of the product alcohols is related to the ground-state conformation of the cis- and trans-pyrans and -furans.The slow SmI2-mediated reactions appear to involve samarium-complexed intermediates having structures independent of the original conformation, or of the cis- or trans-geometry of the furan or pyran, and it is the transition states from these intermediates that determine the stereochemical outcome.Scissions in the tetrahydrofuran series can be accelerated by addition of HMPA or DMPU with only a little deterioration in stereoselectivity, but in the tetrahydropyran series there are drastic changes in product stereochemistry when DMPU is added.Brief comment is made on the synthesis of tetrahydro-furan and pyran precursors.
- Crombie, Leslie,Rainbow, Linda J.
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p. 673 - 688
(2007/10/02)
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- Tube bundle reactor, use thereof in exothermic organic reactions, and preparation of ketones and aldehydes using same
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In a tube bundle reactor for carrying out catalytic organic reactions in the gas phase, comprising reaction tubes (A) arranged between tubesheets (B), the reaction tubes have an inside diameter ranging from 0.5 to 3 cm, the ratio of reaction tube length to inside diameter ranges from 2 to 10, and the reaction tubes (A) are surrounded by a fluid heat transport medium flowing in the crosswise direction; said tube bundle reactor is useful in particular in exothermic organic reactions.
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- Preparation of six membered carocycles by aryl-tellurium mediated free-radical cyclisation
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Radical cyclisation of various telluro-compounds was examined. Olefins conjugated to an electron withdrawing group, (7, 8, 9, 10, and 11) gave high yields of the corresponding six membered products. Non-activating olefin 23 gave the corresponding thiopyridyl derivative 24 as the only product. The photolysis, using oxime 18 as radicophile for the cyclisation, proceeded slowly at room temperature, and gave only a low yield of products 19 and 20.
- Barton,Dalko,Gero
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p. 4713 - 4716
(2007/10/02)
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- The conversion of 4-oxa-5-hexenyllithiums to 4-alken-1-ols: A novel [1,4]-wittig rearrangement
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4-Oxa-5-hexenyllithiums (2), which may be prepared from the corresponding 3-iodoalkyl vinyl ethers (1) by low-temperature lithium - iodine exchange, rearrange in high yield to 4-alken-1-ols (4) when warmed to room temperature. This transformation, which constitutes a [1,4]-Wittig rearrangement, is mediated by 5-exo-trig closure of 2 to a (2-tetrahydrofuranyl)methyllithium (3) followed by spontaneous ring opening to give 4.
- Bailey, William F.,Zarcone, Lyn M. J.
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p. 4425 - 4426
(2007/10/02)
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