The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Zoltán Schay - One of the best experts on this subject based on the ideXlab platform.
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Poisoning and Reuse of Supported Precious Metal Catalysts in the Hydrogenation of N-Heterocycles Part I: Ruthenium-Catalysed Hydrogenation of 1-Methylpyrrole
Catalysis Letters, 2018Co-Authors: László Hegedűs, Kristóf Szőke-molnár, István E. Sajó, Dávid Ferenc Srankó, Zoltán SchayAbstract:Poisoning phenomena of heterogeneous, supported precious metal catalysts caused by nitrogen were investigated in the liquid-phase hydrogenation of 1-Methylpyrrole (MP) to 1-methylpyrrolidine (MPD) over ruthenium on carbon, in non-acidic medium (methanol), at 10 bar and 25–60 °C. Reusing a spent, unregenerated 5% Ru/C catalyst, it was found that the activity of catalyst and the conversion of model substrate were strongly dependent on the amount of catalyst and the number of recycling, respectively. During the first reuse of this ruthenium catalyst, surprisingly, it showed high activity already at room temperature contrary to the fresh catalyst which worked at only 60 °C. This unexpected catalytic behaviour was studied by XRD and XPS methods which revealed the existence of a fine RuO_2 layer on the surface of the catalytic metal in the fresh catalyst. Graphical Abstract
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Poisoning and Reuse of Supported Precious Metal Catalysts in the Hydrogenation of N -Heterocycles Part I: Ruthenium-Catalysed Hydrogenation of 1-Methylpyrrole
Catalysis Letters, 2018Co-Authors: László Hegedűs, Kristóf Szőke-molnár, István E. Sajó, Dávid Ferenc Srankó, Zoltán SchayAbstract:Poisoning phenomena of heterogeneous, supported precious metal catalysts caused by nitrogen were investigated in the liquid-phase hydrogenation of 1-Methylpyrrole (MP) to 1-methylpyrrolidine (MPD) over ruthenium on carbon, in non-acidic medium (methanol), at 10 bar and 25–60 °C. Reusing a spent, unregenerated 5% Ru/C catalyst, it was found that the activity of catalyst and the conversion of model substrate were strongly dependent on the amount of catalyst and the number of recycling, respectively. During the first reuse of this ruthenium catalyst, surprisingly, it showed high activity already at room temperature contrary to the fresh catalyst which worked at only 60 °C. This unexpected catalytic behaviour was studied by XRD and XPS methods which revealed the existence of a fine RuO2 layer on the surface of the catalytic metal in the fresh catalyst.
W. Dean Harman - One of the best experts on this subject based on the ideXlab platform.
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Osmium(II)-, Rhenium(I)-, and Tungsten(0)-Promoted Dipolar Cycloaddition Reactions with Pyrroles: Exploiting the Azomethine Ylide Character of This Heterocycle
Organometallics, 2006Co-Authors: Kevin D. Welch, William H. Myers, Andrew P. Keller, Michal Sabat, Philip L. Smith, W. Dean HarmanAbstract:Complexes of the form TpRe(CO)(MeIm)(η2-pyr) and TpW(NO)(PMe3)(η2-pyr) (where pyr = 1-Methylpyrrole, 2-Methylpyrrole, and 2,5-diMethylpyrrole) were prepared and combined with a range of potential dipolarophiles. In several cases a dipolar cycloaddition resulted in the formation of 7-azanorbornene complexes (one crystal structure for each metal is presented), but attempts to develop a general route to the organic bicyclic system were unsuccessful. Using the complex [Os(NH3)5(η2-pyrrole)]2+ an organic cycloadduct was successfully prepared with dimethyl fumarate, and this complex was elaborated into advanced synthons to several naturally occurring pyrrolizidines.
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Tungsten(0) and Rhenium(I) η2-Pyrrole Complexes: Dearomatization of Pyrroles and Their Facile Isomerizations, Protonations, and Reductions
Organometallics, 2005Co-Authors: William H. Myers, Kevin D. Welch, Peter M. Graham, Andrew P. Keller, Michal Sabat, Carl Trindle, W. Dean HarmanAbstract:Complexes of the form TpRe(CO)(MeIm)(η2-L) and TpW(NO)(PMe3)(η2-L) have been synthesized, where L = 1-Methylpyrrole, 2-Methylpyrrole, and 2,5-diMethylpyrrole. Depending on the nature of both the pyrrole and the metal, either a η2-1H- or an η2-3H-pyrrole complex can be isolated. In contrast, for the parent pyrrole, oxidative addition occurs across the N−H bond, generating either a N-pyrrolyl or N-pyrrolyl hydride. The protonation or methylation of the η2-pyrrole complexes and the reduction of the resulting pyrrolium species have also been investigated.
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A Promising New Dearomatization Agent: Crystal Structure, Synthesis, and Exchange Reactions of the Versatile Complex TpRe(CO)(1-methylimidazole)(η2-benzene) (Tp = Hydridotris(pyrazolyl)borate)
Organometallics, 2001Co-Authors: Scott H. Meiere, Benjamin C. Brooks, T. Brent Gunnoe, And Michal Sabat, W. Dean HarmanAbstract:The π-basic metal fragment {TpRe(CO)(MeIm)} (MeIm = 1-methylimidazole; Tp = hydridotris(pyrazolyl)borate) binds a variety of aromatic molecules, including benzene, 2,6-lutidine, and 1-Methylpyrrole, in an η2 fashion. Although TpRe(CO)(MeIm)(η2-benzene) as a solid shows no decomposition over several months at 25 °C under a nitrogen atmosphere, the complex has proven to be a valuable precursor to a variety of other aromatic complexes through ligand exchange reactions in solution.
László Hegedűs - One of the best experts on this subject based on the ideXlab platform.
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Poisoning and Reuse of Supported Precious Metal Catalysts in the Hydrogenation of N-Heterocycles Part I: Ruthenium-Catalysed Hydrogenation of 1-Methylpyrrole
Catalysis Letters, 2018Co-Authors: László Hegedűs, Kristóf Szőke-molnár, István E. Sajó, Dávid Ferenc Srankó, Zoltán SchayAbstract:Poisoning phenomena of heterogeneous, supported precious metal catalysts caused by nitrogen were investigated in the liquid-phase hydrogenation of 1-Methylpyrrole (MP) to 1-methylpyrrolidine (MPD) over ruthenium on carbon, in non-acidic medium (methanol), at 10 bar and 25–60 °C. Reusing a spent, unregenerated 5% Ru/C catalyst, it was found that the activity of catalyst and the conversion of model substrate were strongly dependent on the amount of catalyst and the number of recycling, respectively. During the first reuse of this ruthenium catalyst, surprisingly, it showed high activity already at room temperature contrary to the fresh catalyst which worked at only 60 °C. This unexpected catalytic behaviour was studied by XRD and XPS methods which revealed the existence of a fine RuO_2 layer on the surface of the catalytic metal in the fresh catalyst. Graphical Abstract
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Poisoning and Reuse of Supported Precious Metal Catalysts in the Hydrogenation of N -Heterocycles Part I: Ruthenium-Catalysed Hydrogenation of 1-Methylpyrrole
Catalysis Letters, 2018Co-Authors: László Hegedűs, Kristóf Szőke-molnár, István E. Sajó, Dávid Ferenc Srankó, Zoltán SchayAbstract:Poisoning phenomena of heterogeneous, supported precious metal catalysts caused by nitrogen were investigated in the liquid-phase hydrogenation of 1-Methylpyrrole (MP) to 1-methylpyrrolidine (MPD) over ruthenium on carbon, in non-acidic medium (methanol), at 10 bar and 25–60 °C. Reusing a spent, unregenerated 5% Ru/C catalyst, it was found that the activity of catalyst and the conversion of model substrate were strongly dependent on the amount of catalyst and the number of recycling, respectively. During the first reuse of this ruthenium catalyst, surprisingly, it showed high activity already at room temperature contrary to the fresh catalyst which worked at only 60 °C. This unexpected catalytic behaviour was studied by XRD and XPS methods which revealed the existence of a fine RuO2 layer on the surface of the catalytic metal in the fresh catalyst.
Axel Marchal - One of the best experts on this subject based on the ideXlab platform.
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Toward a Molecular Understanding of the Typicality of Chardonnay Wines: Identification of Powerful Aromatic Compounds Reminiscent of Hazelnut.
Journal of Agricultural and Food Chemistry, 2017Co-Authors: Jacques Gros, Valérie Lavigne, Fannie Thibaud, Marine Gammacurta, Virginie Moine, Denis Dubourdieu, Philippe Darriet, Axel MarchalAbstract:Chardonnay wines impart a unique complex aroma characterized by its buttery, yellow stone fruit, melon, bready, and woody notes. Among the terms used in the sensory analysis of these wines, this study investigated hazelnut-like attributes. Multidimensional gas chromatography coupled to olfactometry identified five pyrroles reminiscent of hazelnut: 1-ethylpyrrole-2-carboxaldehyde, 1H-pyrrole, 2-acetyl-1H-pyrrole (first identification in wine), 1-Methylpyrrole-2-carboxaldehyde, and 1H-pyrrole-2-carboxaldehyde. Quantitative analyses demonstrated their significantly higher abundance in Chardonnay wines. However, they proved irrelevant in sensory terms, given the low amounts measured in wine compared to their olfactory detection threshold. Nevertheless, the presence of methanethiol derivatives from these pyrroles was investigated in wine. 1-Methylpyrrole-2-methanethiol and 1-ethylpyrrole-2-methanethiol were identified and exhibited hazelnut-like aroma. These compounds, which have not been observed in natural p...
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Toward a molecular inderstanding of the typicality of chardonnay wines: identification of powerful aromatic compounds reminiscent of hazelnut
Journal of Agricultural and Food Chemistry, 2017Co-Authors: Jacques Gros, Valérie Lavigne, Fannie Thibaud, Marine Gammacurta, Virginie Moine, Denis Dubourdieu, Philippe Darriet, Axel MarchalAbstract:Chardonnay wines impart a unique complex aroma characterized by its buttery, yellow stone fruit, melon, bready, and woody notes. Among the terms used in the sensory analysis of these wines, this study investigated hazelnut-like attributes. Multidimensional gas chromatography coupled to olfactometry identified five pyrroles reminiscent of hazelnut: 1-ethylpyrrole-2-carboxaldehyde, 1H-pyrrole, 2-acetyl-1H-pyrrole (first identification in wine), 1-Methylpyrrole-2-carboxaldehyde, and 1H-pyrrole-2-carboxaldehyde. Quantitative analyses demonstrated their significantly higher abundance in Chardonnay wines. However, they proved irrelevant in sensory terms, given the low amounts measured in wine compared to their olfactory detection threshold. Nevertheless, the presence of methanethiol derivatives from these pyrroles was investigated in wine. 1-Methylpyrrole-2-methanethiol and 1-ethylpyrrole-2-methanethiol were identified and exhibited hazelnut-like aroma. These compounds, which have not been observed in natural products to date, are potent volatile compounds with detection thresholds of 0.7 and 1.4 ng/L, respectively, in model wine. These findings open up promising perspectives concerning the interpretation of the typical aromatic nuances of some Chardonnay wines.
Kristóf Szőke-molnár - One of the best experts on this subject based on the ideXlab platform.
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Poisoning and Reuse of Supported Precious Metal Catalysts in the Hydrogenation of N-Heterocycles Part I: Ruthenium-Catalysed Hydrogenation of 1-Methylpyrrole
Catalysis Letters, 2018Co-Authors: László Hegedűs, Kristóf Szőke-molnár, István E. Sajó, Dávid Ferenc Srankó, Zoltán SchayAbstract:Poisoning phenomena of heterogeneous, supported precious metal catalysts caused by nitrogen were investigated in the liquid-phase hydrogenation of 1-Methylpyrrole (MP) to 1-methylpyrrolidine (MPD) over ruthenium on carbon, in non-acidic medium (methanol), at 10 bar and 25–60 °C. Reusing a spent, unregenerated 5% Ru/C catalyst, it was found that the activity of catalyst and the conversion of model substrate were strongly dependent on the amount of catalyst and the number of recycling, respectively. During the first reuse of this ruthenium catalyst, surprisingly, it showed high activity already at room temperature contrary to the fresh catalyst which worked at only 60 °C. This unexpected catalytic behaviour was studied by XRD and XPS methods which revealed the existence of a fine RuO_2 layer on the surface of the catalytic metal in the fresh catalyst. Graphical Abstract
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Poisoning and Reuse of Supported Precious Metal Catalysts in the Hydrogenation of N -Heterocycles Part I: Ruthenium-Catalysed Hydrogenation of 1-Methylpyrrole
Catalysis Letters, 2018Co-Authors: László Hegedűs, Kristóf Szőke-molnár, István E. Sajó, Dávid Ferenc Srankó, Zoltán SchayAbstract:Poisoning phenomena of heterogeneous, supported precious metal catalysts caused by nitrogen were investigated in the liquid-phase hydrogenation of 1-Methylpyrrole (MP) to 1-methylpyrrolidine (MPD) over ruthenium on carbon, in non-acidic medium (methanol), at 10 bar and 25–60 °C. Reusing a spent, unregenerated 5% Ru/C catalyst, it was found that the activity of catalyst and the conversion of model substrate were strongly dependent on the amount of catalyst and the number of recycling, respectively. During the first reuse of this ruthenium catalyst, surprisingly, it showed high activity already at room temperature contrary to the fresh catalyst which worked at only 60 °C. This unexpected catalytic behaviour was studied by XRD and XPS methods which revealed the existence of a fine RuO2 layer on the surface of the catalytic metal in the fresh catalyst.
