918-85-4Relevant academic research and scientific papers
Precursor Nuclearity and Ligand Effects in Atomically-Dispersed Heterogeneous Iron Catalysts for Alkyne Semi-Hydrogenation
Faust Akl, Dario,Ruiz-Ferrando, Andrea,Fako, Edvin,Hauert, Roland,Safonova, Olga,Mitchell, Sharon,López, Núria,Pérez-Ramírez, Javier
, p. 3247 - 3256 (2021/05/31)
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.
Method for preparing allyl alcohol compound by reduction of propargyl alcohol compound
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Paragraph 0057-0058, (2021/11/10)
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.
Palladium-Phosphorus Nanoparticles as Effective Catalysts of the Chemoselective Hydrogenation of Alkynols
Belykh, L. B.,Dashabylova, T. M.,Gvozdovskaya, K. L.,Schmidt, F. K.,Skripov, N. I.,Sterenchuk, T. P.,Zherdev, V. V.
, p. 575 - 588 (2020/08/05)
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.
SUBSTITUTED CYCLOPENTYL- AND CYCLOHEXYL-DERIVATIVES USEFUL FOR PERFUMERY
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Page/Page column 22, (2017/07/06)
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.
Gold-Ligand-Catalyzed Selective Hydrogenation of Alkynes into cis-Alkenes via H2 Heterolytic Activation by Frustrated Lewis Pairs
Fiorio, Jhonatan L.,López, Núria,Rossi, Liane M.
, p. 2973 - 2980 (2017/05/31)
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).
The application of palladium and zeolite incorporated chip-based microreactors
Truter,Ordomsky,Schouten,Nijhuis
, p. 72 - 82 (2016/02/19)
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.
Stereoselective Rh-Catalyzed Hydrogenative Desymmetrization of Achiral Substituted 1,4-Dienes
Fernández-Pérez, Héctor,Lao, Joan R.,Vidal-Ferran, Anton
supporting information, p. 2836 - 2839 (2016/07/06)
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).
Congested C-C bonds by Pd-catalyzed enantioselective allyl-allyl cross-coupling, a mechanism-guided solution
Ardolino, Michael J.,Morken, James P.
supporting information, p. 7092 - 7100 (2014/06/09)
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.
Stereo- and chemoselective character of supported CEO2 catalysts for continuous-flow three-phase alkyne hydrogenation
Vile, Gianvito,Wrabetz, Sabine,Floryan, Leonard,Schuster, Manfred Erwin,Girgsdies, Frank,Teschner, Detre,Perez-Ramirez, Javier
, p. 1928 - 1934 (2014/08/05)
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.
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
Vile, Gianvito,Almora-Barrios, Neyvis,Mitchell, Sharon,Lopez, Nuria,Perez-Ramirez, Javier
, p. 5926 - 5937 (2014/05/20)
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.
