- 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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- Method for preparing allyl alcohol compound by reduction of propargyl alcohol compound
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A hydrazide compound is used as a reducing agent, an organic amine is used as an auxiliary, and the propargyl alcohol compound is selectively reduced to obtain an allyl alcohol compound under the presence of a solvent and a certain temperature. The method does not need Pd catalyst which is expensive, and the reducing agent and auxiliary agent are cheap and easily available, easy to separate, free of residue in the product, simple in reaction operation process, mild in reaction condition, high in target product selectivity and the like.
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Paragraph 0057-0058
(2021/11/10)
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- Palladium-Phosphorus Nanoparticles as Effective Catalysts of the Chemoselective Hydrogenation of Alkynols
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Abstract: The effect of the composition of the catalytic system and reaction conditions on the properties of phosphorus-modified palladium catalysts in hydrogenations of alkynols was studied. Modification with phosphorus increased the activity and turnover number of palladium catalysts in the hydrogenation of the model compound 2-methyl-3-butyn-2-ol (MBY) without any reduction in the selectivity to 2-methyl-3-butene-2-ol at 95–98percent MBY conversion. The promoting effect of phosphorus on the properties of the palladium catalyst is caused not only by an increase in the particle size, but also, probably, by a change in the energy of interaction of reagents with the active sites. Hypotheses on the nature of the carriers of catalytic activity in Pd–P particles were discriminated using kinetic methods with the differential selectivity of catalytic systems as the main measured parameter under the conditions of competition between two alkynols. The hydrogenation of acetylenic alcohols involves only one of the two potentially active forms in Pd–P nanoparticles—Pd(0) clusters, whereas the hydrogenation of the resulting allyl alcohols involves both Pd(0) clusters and palladium phosphides.
- Belykh, L. B.,Dashabylova, T. M.,Gvozdovskaya, K. L.,Schmidt, F. K.,Skripov, N. I.,Sterenchuk, T. P.,Zherdev, V. V.
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p. 575 - 588
(2020/08/05)
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- SUBSTITUTED CYCLOPENTYL- AND CYCLOHEXYL-DERIVATIVES USEFUL FOR PERFUMERY
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The present invention refers to substituted cyclopentyl- and cyclohexyl-derivatives of formula (I) wherein n, R1, R2, R3, R4 and X have the same meaning as given in the description. The invention further refers to fragrance compositions and fragranced articles comprising them.
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Page/Page column 22
(2017/07/06)
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- Gold-Ligand-Catalyzed Selective Hydrogenation of Alkynes into cis-Alkenes via H2 Heterolytic Activation by Frustrated Lewis Pairs
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The selective hydrogenation of alkynes to alkenes is an important synthetic process in the chemical industry. It is commonly accomplished using palladium catalysts that contain surface modifiers, such as lead and silver. Here we report that the adsorption of nitrogen-containing bases on gold nanoparticles results in a frustrated Lewis pair interface that activates H2 heterolytically, allowing an unexpectedly high hydrogenation activity. The so-formed tight-ion pair can be selectively transferred to an alkyne, leading to a cis isomer; this behavior is controlled by electrostatic interactions. Activity correlates with H2 dissociation energy, which depends on the basicity of the ligand and its reorganization on activation of hydrogen. High surface occupation and strong Au atom-ligand interactions might affect the accessibility and stability of the active site, making the activity prediction a multiparameter function. The promotional effect found for nitrogen-containing bases with two heteroatoms was mechanistically described as a strategy to boost gold activity. (Graph Presented).
- Fiorio, Jhonatan L.,López, Núria,Rossi, Liane M.
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p. 2973 - 2980
(2017/05/31)
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- Stereoselective Rh-Catalyzed Hydrogenative Desymmetrization of Achiral Substituted 1,4-Dienes
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Highly efficient catalytic stereoselective hydrogenative desymmetrization reactions mediated by rhodium complexes derived from enantiopure phosphine-phosphite (P-OP) ligands are described. The highest performing ligand, which contains a TADDOL-derived phosphite fragment [TADDOL = (2,2-dimethyl-1,3-dioxolane-4,5-diyl)bis(diphenylmethanol)], presented excellent catalytic properties for the desymmetrization of a set of achiral 1,4-dienes, providing access to the selective formation of a variety of enantioenriched secondary and tertiary alcohols (six examples, up to 92% ee).
- Fernández-Pérez, Héctor,Lao, Joan R.,Vidal-Ferran, Anton
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supporting information
p. 2836 - 2839
(2016/07/06)
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- The application of palladium and zeolite incorporated chip-based microreactors
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The ability to successfully incorporate heterogeneous catalysts into chip-microreactors is demonstrated in the application of a Pd/ZSM-5 and Pd/silicalite chip-based microreactor for the synthesis of methyl-iso-ketone (MIBK) and the hydrogenation of 3-methyl-1-pentyn-3-ol. The bifunctional Pd/ZSM-5 chip-microreactor provides a high selectivity (>90%) to MIBK due to the incorporation of palladium and high Br?nsted acidity while demonstrating the ability to regenerate and reuse the Pd/ZSM-5 chip-microreactor. The Pd/silicalite chip-microreactor illustrated the advantage of improved control of residence time in the microreactor to obtain high alkene yields. In addition, the design of chip-holders which are operable at high temperature, pressure and have a high chemical resistance further extend the operability of chip-based microreactors for use in the special chemical industry.
- Truter,Ordomsky,Schouten,Nijhuis
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- Congested C-C bonds by Pd-catalyzed enantioselective allyl-allyl cross-coupling, a mechanism-guided solution
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Under the influence of a chiral bidentate diphosphine ligand, the Pd-catalyzed asymmetric cross-coupling of allylboron reagents and allylic electrophiles establishes 1,5-dienes with adjacent stereocenters in high regio-and stereoselectivity. A mechanistic study of the coupling utilizing reaction calorimetry and density functional theory analysis suggests that the reaction operates through an inner-sphere 3,3′-reductive elimination pathway, which is both rate-defining and stereodefining. Coupled with optimized reaction conditions, this mechanistic detail is used to expand the scope of allyl-allyl couplings to allow the generation of 1,5-dienes with tertiary centers adjacent to quaternary centers as well as a unique set of cyclic structures.
- Ardolino, Michael J.,Morken, James P.
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supporting information
p. 7092 - 7100
(2014/06/09)
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- Stereo- and chemoselective character of supported CEO2 catalysts for continuous-flow three-phase alkyne hydrogenation
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TiO2-, Al2O3-, and ZrO2- supported CeO2 catalysts with different Ce loadings were prepared by wet impregnation of the carriers with an acidified solution of cerium ammonium nitrate. The calcined catalysts were characterized by bulk and surface-sensitive techniques, which included microcalorimetry, and evaluated in the three-phase hydrogenation of alkynes under continuous-flow conditions at variable temperature (293-413 K) and pressure (1-90 bar). A number of acetylenic compounds, which contain terminal or internal triple bonds, conjugated unsaturations, and additional functionalities, were systematically assessed. The results revealed the full stereo- and chemoselective character of the ceria catalysts, which outperform the well-known Lindlar catalyst, and open promising perspectives for the revolutionary use of a cost-effective oxide for the production of olefinic compounds in the vitamin and fine chemical industries.
- Vile, Gianvito,Wrabetz, Sabine,Floryan, Leonard,Schuster, Manfred Erwin,Girgsdies, Frank,Teschner, Detre,Perez-Ramirez, Javier
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p. 1928 - 1934
(2014/08/05)
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- From the lindlar catalyst to supported ligand-modified palladium nanoparticles: Selectivity patterns and accessibility constraints in the continuous-flow three-phase hydrogenation of acetylenic compounds
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Site modification and isolation through selective poisoning comprise an effective strategy to enhance the selectivity of palladium catalysts in the partial hydrogenation of triple bonds in acetylenic compounds. The recent emergence of supported hybrid materials matching the stereo- and chemoselectivity of the classical Lindlar catalyst holds promise to revolutionize palladium-catalyzed hydrogenations, and will benefit from an in-depth understanding of these new materials. In this work, we compare the performance of bare, lead-poisoned, and ligand-modified palladium catalysts in the hydrogenation of diverse alkynes. Catalytic tests, conducted in a continuous-flow three-phase reactor, coupled with theoretical calculations and characterization methods, enable elucidation of the structural origins of the observed selectivity patterns. Distinctions in the catalytic performance are correlated with the relative accessibility of the active site to the organic substrate, and with the adsorption configuration and strength, depending on the ensemble size and surface potentials. This explains the role of the ligand in the colloidally prepared catalysts in promoting superior performance in the hydrogenation of terminal and internal alkynes, and short-chain alkynols. In contrast, the greater accessibility of the active surface of the Pd-Pb alloy and the absence of polar groups are shown to be favorable in the conversion of alkynes containing long aliphatic chains and/or ketone groups. These findings provide detailed insights for the advanced design of supported nanostructured catalysts. Hybrid nanocatalysts: The classical Lindlar and the newly developed NanoSelectTM catalysts are confronted in the semi-hydrogenation of alkynes (see figure). Systematic testing under continuous-flow three-phase conditions, coupled with detailed characterization analyses and molecular simulations, enable the understanding of the structure of the catalysts and the associated activity and selectivity patterns for a wide range of acetylenic compounds.
- Vile, Gianvito,Almora-Barrios, Neyvis,Mitchell, Sharon,Lopez, Nuria,Perez-Ramirez, Javier
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p. 5926 - 5937
(2014/05/20)
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- Method for producing alkane or alkene compound
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[PROBLEM TO BE SOLVED]: To provide a method for producing alkane or alkene compounds by reduction of carbon-carbon multiple bond. [SOLUTION]: The method for producing alkane or alkene compounds shown by the general formula (5)-(7) [wherein, R1, R2, R3, R4, R5, and R6 are optionally different and hydrogen etc. independently respectively] characterized by reacting either kind or these mixtures among alkene or alkyne compounds shown by general formula (1) or (2) [wherein, R1-R6 are the same as formula (5)-(7)] in the presence of at least one kind selected from groups of bromic acid and hydrogen peroxide shown by general formula (3) (wherein, M is hydrogen or metal atom; m is integer of 1-3), hydrazine compoun shown by general formula (4) [wherein, n is integer of equal to or more than 0], and acid. [EFFECT]: Alkane or alkene compounds can be produced handily without hydrogenation equipment.
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Page/Page column 16
(2008/06/13)
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- Confined space-controlled hydroperoxidation of trisubstituted alkenes adsorbed on pentasil zeolites
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Photosensitized oxidation of trialkylalkenes 2-methyl-2-pentene (1), 1-methylcyclohexene (2), trans-3-methyl-2-pentene (3), cis-3-methyl-2-pentene (4), and 2-methyl-2-butene (5) included in the internal framework of Na-ZSM-5 zeolites was investigated. The zeolite samples having adsorbed the alkenes were suspended in isooctane, and the sensitizer, tetraphenylporphyrin (TPP), was dissolved in the solution. Singlet oxygen produced in the solution diffused into the internal framework of the zeolites and reacted with alkenes. For all the substrates studied, the ene-type allylic hydroperoxides were obtained in a highly regioselective manner. The regiochemistry for 1-4 in favor of the allylic hydrogen abstraction from the largest substituents is in contrast to their photooxidation within the dye-supported zeolite Na-Y, where the secondary hydroperoxides are preferentially produced. The tight confinement of the alkenes within the narrow channels of the ZSM-5 zeolites is likely to be responsible for this selectivity.
- Chen, Yu-Zhe,Wu, Li-Zhu,Zhang, Li-Ping,Tung, Chen-Ho
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p. 4676 - 4681
(2007/10/03)
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- Selective liquid-phase semihydrogenation of functionalized acetylenes and propargylic alcohols with silica-supported bimetallic palladium-copper catalysts
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Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated. Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated.
- Spee,Boersma,Meijer,Slagt,Van Koten,Geus
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p. 1647 - 1656
(2007/10/03)
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- Intramolecular trapping of an ylide intermediate in the reaction of1:CH2 with an allylic alcohol
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The reaction of 1:CH2, generated by the photolysis of CH2N2, with 2-methyl-3-buten-2-ol leads to the formation of several products including 4-methyl-3-penten-1-ol. This product is best explained as the result of rearrangement of an ylide intermediate.
- Sobery, Warunee,DeLuca, Joann P.
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p. 3315 - 3316
(2007/10/02)
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- Expedient synthesis of quadrilure antipodes, the pheromone of square-necked grain beetle
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Both the enantiomers of the title pheromone, (E)-3-methyl-7-acetoxynon-3-ene (I) have been synthesized in high enantiomeric excess via a stereoselective route. Thus, easily accessible, 3-methylpent-1-en-3-ol (2) was converted via a Claisen orthoester rearrangement to the ester (3) with exclusive (E)-geometry. Its derivatization to the aldehyde (5) followed by reaction with ethylmagnesium bromide gave the racemic pheromone alcohol (6) in 27.7% overall yield. Its enantioselective lipase catalyzed trans-esterification directly afforded (R)-I, while its antipode was obtained from the resolved alcohol by chemical acetylation.
- Pawar,Chattopadhyay
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p. 463 - 468
(2007/10/02)
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- Pheromones of Coleoptera. 12. Synthesis of (+/-)-2,6-dimethyloctyl formate, the biologically active analog of the smaller flour beetle aggregation pheromone
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Racemic 2,6-dimethyloctyl formate (1), a synthetic analog of the aggregation pheromone of two species of Tribolium beetles, has been obtained in six steps and in 28 percent overall yield starting from methyl ethyl ketone, vinyl bromide, and 2-methylpropenal.The key step of the synthesis is the sigmatropic -rearrangement of 4-ethyl-2,4-dimethyl-1,5-hexadien-3-ol (5) to 2,6-dimethyl-5-octenal (6).
- Gamalevich, G. D.,Serebryakov, E. P.
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p. 741 - 743
(2007/10/02)
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- Effect of the metal catalyst on the mechanism of hydrogenation of C6 acetylenic carbinols
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The most probable mechanism of the hydrogenation of tertiary and of primary C6 acetylenic carbinols on group VIII metals are discussed.By using mathematical modelling and deuterium exchange methods we have shown that in the presence of Pd, Rh, and Pt the reaction takes place by a series mechanism, whereas on Ru black the acetylenic C6 alcohols are hydrogenated by a series-parallel scheme.
- Sokolo'skii, D. V.,Zhubanova, L. K.,Omarkulov, T. O.,Sadykov, U. A.,Korolev, A. V.
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- EFFECT OF THE STRUCTURE OF SUBSTITUTED PROPARGYL AND ALLYL ALCOHOLS ON THE RATE OF THEIR LIQUID PHASE HYDROGENATION ON A Pd-Ru ALLOY MEMBRANE CATALYST
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The rates of hydrogenation of substituted propargyl and allyl alcohols in the liquid phase on a Pd-Ru alloy membrane catalyst are described by a two-parameter Taft equation which takes into account the inductive and steric effects of the substituents.The values of the parameters at 363 K with H2 at atmospheric pressure are: ρ* = -0.20, δ = 0.10 and ρ+ = -1.1, δ = 1.3 respectively.
- Karavanov, A. N.,Gryaznov, V. M.
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p. 1593 - 1596
(2007/10/02)
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- The synthesis and characterization of 3,3-disubstituted pent-4-enals and their 2,2-(trimethylendithio)pent-4-enal precursors, including the X-ray crystal structure of (R)-3-ethyl-3-phenyl-2,2-(trimethylenedithio)pent-4-enal
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A variety of 3,3-disubstituted pent-4-enals (5a, R=Me, R'=Et; 5b, R=Me, R'=Ph; 5c, R=Et, R'=Ph) has been prepared by the Raney nickel desulfurization of the corresponding 3,3-disubstituted 2,2-(trimethylenedithio)pent-4-enal precursors 4a-4c.The precursor compounds were prepared by the alkylation of 2-formyl-1,3-dithiane with the appropriate 3,3-disubstituted allylic bromide.The new compounds have been characterized by elemental analysis, infrared and nmr spectroscopy, and mass spectrometry.The crystal and molecular structure of (R)-4c has also been determined by X-ray crystallography.At temperatures of ca. 130 deg C, compounds 4a-4c undergo intramolecular rearrangement to form the trisubstituted alkenes 6a-6c, which have also been characterized by the present study.
- Young, Charles G.,James, Brian R.,Rettig, Steven J.
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p. 1035 - 1040
(2007/10/02)
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- Improved Synthesis of Bowers'Juvenile Hormone Mimic
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An improved synthesis of 6,7-epoxy-3, 7-dimethyl-1-(3,4-methylenedioxyphenoxy)-2-nonene, the Bowers' juvenile hormone mimic is described.The proposed synthesis is espected to facilitate easy introduction of radioisotope labels at variety of sites for metabolic studies.The overall yield of the six-step route is 4,7percent.
- Vaidya, Niteen A.,Broger, Emil A.
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p. 241 - 243
(2007/10/02)
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- Hydrocyanation and Hydrogenation of Acetylenes catalysed by Cyanocobaltates
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Acetylenes are regioselectively hydrocyanated by cyanocobaltate prepared at CN:Co -.The preliminary formation of a 3- complex is assumed to explain the fact that the complex is active only at CN:Co 3- which is formed by the reaction of the ?-acetylene complex, rather than acetylene itself, with 3-.
- Funabiki, Takuzo,Yamazaki, Yasuyuki,Sato, Yoshihiro,Yoshida, Satohiro
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p. 1915 - 1918
(2007/10/02)
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- PREPARATION DE CETONES ET D'ALCOOLS INSATURES A PARTIR DE LA METHYLVINYLCETONE. UNE SYNTHESE SIMPLE ET EFFICACE D'ALCOOLS ISOPRENIQUES
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The preparation of olefinic ketones and alcohols by means of a retro Diels-Alder reaction is described.This process has been applied to high yield syntheses of linalool 6e, nerolidol 6f and the sesquiterpene alcohol 10 recently isolated from the alga Laurencia nidifica.
- Bloch, R.
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p. 639 - 644
(2007/10/02)
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- A NOVEL STEREOSPECIFIC REDUCTION OF ALKYNES TO ALKENES
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Zinc-copper couple in boiling methanol reduces alkynes to olefins in nearly quantitative yields.Terminal acetylenes are converted to terminal ethylenes, whereas disubstitued acetylenes are transformed to (Z)-olefins.
- Sondengam, B. L.,Charles, G.,Akam, T. M.
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p. 1069 - 1070
(2007/10/02)
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- Activation of Reducing Agents. Sodium Hydride Containing Complex Reducing Agents. 13. Selective Heterogeneous Hydrogenation of Polyfunctional Substrates over Nic
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Preparative-scale heterogeneous hydrogenation over Nic at room temperature and 1 atm are described.It is shown that these catalysts allow the selective hydrogenation of carbon-carbon double bonds in the presence of oxo groups without side reactions.Alkynes and functional alkynes are selectively hydrogenated to the corresponding cis alkenes in high yields.Carbonyl group hydrogenations were also performed in high yields.Selective hydrogenation properties of Nic were exemplified in the steroid series.Finally, it was demonstrated that this new catalyst-preparation concept is not limited to nickel and also applies to the preparation of cobalt and palladium catalysts.
- Gallois, Philippe,Brunet, Jean-Jaques,Caubere, Paul
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p. 1946 - 1950
(2007/10/02)
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- Process for producing ethynylating agents
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An ethynylating agent formed from mixing an anhydrous magnesium compound with sodium acetylide and its use in preparing ethynyl carbinols.
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