Hydrogenation Of Pyridine Research Articles

Electrocatalytic Hydrogenation of Pyridines and Other Nitrogen-Containing Aromatic Compounds.

The production of cyclic amines, which are vital to the pharmaceutical industry, relies on energy-intensive thermochemical hydrogenation. Herein, we demonstrate the electrocatalytic hydrogenation of nitrogen-containing aromatic compounds, specifically pyridine, at ambient temperature and pressure via a membrane electrode assembly with an anion-exchange membrane. We synthesized piperidine using a carbon-supported rhodium catalyst, achieving a current density of 25 mA cm-2 and a current efficiency of 99% under a circular flow until 5 F mol-1. Quantitative conversion of pyridine into piperidine with 98% yield was observed after passing 9 F mol-1, corresponding to 65% of current efficiency. The reduction of Rh oxides on the catalyst surface was crucial for catalysis. The Rh(0) surface interacts moderately with piperidine, decreasing the energy required for the rate-determining desorption step. The proposed process is applicable to other nitrogen-containing aromatic compounds and could be efficiently scaled up. This method presents clear advantages over traditional high-temperature and high-pressure thermochemical catalytic processes.

Synthesis and Investigation of Catalytic Properties of Metal-Polymer Nanocomposites Based on Unsaturated Polyester Resins

This paper focuses on the hydrogenation process in metal-polymer complexes based on copolymers of polypropylene glycol fumarate phthalate and polypropylene glycol maleate phthalate, using acrylic acid and immobilized cobalt metal particles as catalysts. A classical reaction of the electrocatalytic hydrogenation of pyridine to piperidine was applied. SEM and dynamic light scattering were utilized to investigate the average size and dispersity of cobalt metal nanoparticles. The experimental findings show that the efficiency of hydrogenation can be improved by increasing the temperature from 25 to 40 °C and the current to 2 A. More specifically, increasing the temperature to 40 °C promotes swelling of the polymer and its transition from a globular collapsed state to an open one, which leads to an increase in the number of active catalytic centers and, as a consequence, acceleration of the hydrogenation process. Increasing the current strength to 2 A also helps to increase the rate of the hydrogenation process. Further increasing the current to 3 A is undesirable due to an increase in the yield of by-products and a decrease in the yield of the target product, piperidine. Based on a comparative analysis, it was established that the use of a copolymer of polypropylene glycol maleate phthalate with acrylic acid as the polymer matrix base is the most preferable for obtaining polymer-metal complexes with nanosized cobalt.

Electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines under mild conditions with a proton-exchange membrane reactor.

An electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines using a proton-exchange membrane (PEM) reactor was developed. Cyanoarenes were then reduced to the corresponding benzylamines at room temperature in the presence of ethyl phosphate. The reduction of nitroarenes proceeded at room temperature, and a variety of anilines were obtained. The quinoline reduction was efficiently promoted by adding a catalytic amount of p-toluenesulfonic acid (PTSA) or pyridinium p-toluenesulfonate (PPTS). Pyridine was also reduced to piperidine in the presence of PTSA.

Hydrogenation of functionalised pyridines with a rhodium oxide catalyst under mild conditions.

Piperidines are one of the most widely used building blocks in the synthesis of pharmaceutical and agrochemical compounds. The hydrogenation of pyridines is a convenient method to synthesise such compounds as it only requires reactant, catalyst, and a hydrogen source. However, this reaction still remains difficult for the reduction of functionalised and multi-substituted pyridines. Here we report the use of a stable, commercially available rhodium compound, Rh2O3, for the reduction of various unprotected pyridines. The reaction only requires mild conditions, and the substrate scope is broad, making it practically useful.

An Asymmetric Hydrogenation/N-Alkylation Sequence for a Step-Economical Route to Indolizidines and Quinolizidines.

The direct catalytic asymmetric hydrogenation of pyridines for the synthesis of piperidines remains a challenge. Herein, we report a one-pot asymmetric hydrogenation of pyridines with subsequent N-alkylation using a traceless Brønsted acid activation strategy. Catalyzed by the iridium-BINAP complex, the substrates undergo ketone reduction, cyclization and pyridine hydrogenation in sequence to form indolizidines and quinolizidines. The absolute configuration ofthe chiral center of the alcohol is retained and influences the formation of the second chiral center. The experimental and theoretical mechanistic studies reveal that the chloride anion and certain noncovalent interactions govern the stereoselectivity of the cascade reaction throughout the catalytic process.

An Asymmetric Hydrogenation/N‐Alkylation Sequence for a Step‐Economical Route to Indolizidines and Quinolizidines

AbstractThe direct catalytic asymmetric hydrogenation of pyridines for the synthesis of piperidines remains a challenge. Herein, we report a one‐pot asymmetric hydrogenation of pyridines with subsequent N‐alkylation using a traceless Brønsted acid activation strategy. Catalyzed by an iridium‐BINAP complex, the substrates undergo ketone reduction, cyclization and pyridine hydrogenation in sequence to form indolizidines and quinolizidines. The absolute configuration of the stereocenter of the alcohol is retained and influences the formation of the second stereocenter. Experimental and theoretical mechanistic studies reveal that the chloride anion and certain noncovalent interactions govern the stereoselectivity of the cascade reaction throughout the catalytic process.

Selective Hydrogenation of Pyridine and Derivatives of It on Bimetallic Catalysts Modified with Chitosan

A study is performed of the catalytic properties of bimetallic nanoparticles based on palladium and a base metal (silver or copper) supported on alumina modified with chitosan in the selective hydrogenation of pyridine and derivatives of it with the formation of piperidine and derivatives of it. It is shown that the effect of increasing the activity of bimetallic nanoparticles is due to the small size of particles (2–3 nm), compared to the monometallic palladium catalyst. It is established that the conversion of pyridine reaches 99% with 99% selectivity toward piperidine under mild conditions (60°C; H2 pressure, 70 atm).

Selective Hydrogenation of Pyridine and Derivatives of It on Bimetallic Catalysts Modified with Chitosan

Selective Hydrogenation of Pyridine and Derivatives of It on Bimetallic Catalysts Modified with Chitosan

Diastereoselective Hydrogenation of Arenes and Pyridines Promoted by a Ru-Phenanthroline Catalyst

Key words ruthenium catalysis - nanoparticles - hydrogenation - arenes - diastereoselectivity - pyridines

Selective Hydrogenation of Pyridine and Derivatives of It on Bimetallic Catalysts

A study is performed of the catalytic properties of bimetallic nanoparticles based on palladium and a base metal (silver or copper) in the selective hydrogenation of pyridine and derivatives of it with the formation of piperidine and derivatives of it. It is established that the effect of increasing the activity of bimetallic nanoparticles is associated with the small size of particles (2–3 nm), relative to monometallic palladium catalyst. The conversion of pyridine reaches 99% with a piperidine selectivity of 99% under mild conditions (60°C, pressure H2 = 70 atm).

Hydrogenation of pyridine and hydrogenolysis of piperidine over γ-Mo2N catalyst: a DFT study

Increasing demands on producing environmentally friendly products are becoming a driving force for designing highly active catalysts. Thus, surfaces that efficiently catalyse the nitrogen reduction reactions are greatly sought in moderating air-pollutant emissions. This contribution aims to computationally investigate the hydrodenitrogenation (HDN) networks of pyridine over the γ-Mo2N(111) surface using a density functional theory (DFT) approach. Various adsorption configurations have been considered for the molecularly adsorbed pyridine. Findings indicate that pyridine can be adsorbed via side-on and end-on modes in six geometries in which one adsorption site is revealed to have the lowest adsorption energy (–45.3 kcal/mol). Over a nitrogen hollow site adsorption site, initial HDN steps proceed by the stepwise hydrogenation of pyridine into piperidine followed by the Langmuir–Hinshelwood mechanism. The obtained findings are the first to theoretically model the hydrogenation pathways of pyridine to form piperidine and then the hydrogenolysis of piperidine producing C5H12 and NH3 over metal nitride. These paved the way for further investigations to better understanding such an important nitrogen removal reactions.

Exploration of piperidine 3D fragment chemical space: synthesis and 3D shape analysis of fragments derived from 20 regio- and diastereoisomers of methyl substituted pipecolinates.

Fragment-based drug discovery is now widely adopted for lead generation in the pharmaceutical industry. However, fragment screening collections are often predominantly populated with flat, 2D molecules. Herein, we report the synthesis of piperidine-based 3D fragment building blocks - 20 regio- and diastereoisomers of methyl substituted pipecolinates using simple and general synthetic methods. cis-Piperidines, accessed through a pyridine hydrogenation were transformed into their trans-diastereoisomers using conformational control and unified reaction conditions. Additionally, diastereoselective lithiation/trapping was utilised to access trans-piperidines. Analysis of a virtual library of fragments derived from the 20 cis- and trans-disubstituted piperidines showed that it consisted of 3D molecules with suitable molecular properties to be used in fragment-based drug discovery programs.

Diastereoselective hydrogenation of arenes and pyridines using supported ruthenium nanoparticles under mild conditions.

A convenient and practical diastereoselective cis-hydrogenation of multi-substituted pyridines and arenes is reported. Applying a novel heterogeneous ruthenium catalyst, the corresponding piperidines and cyclohexanes are obtained in high yields (typically >80%) with a good functional group tolerance under mild conditions. The robust ruthenium supported catalyst is smoothly prepared and can be reused multiple times without activity loss.

In situ FTIR spectroscopy to unravel the bifunctional nature of aromatics hydrogenation synergy on zeolite/metal catalysts

The hydrogenation of pyridine adsorbed on zeolite is dependent on the distance between acid and metal sites. Hydrogen species produced in the metal diffuse into pyridine and promote hydrogenation, suggesting a bifunctional mechanism is occurring.

Synthesis and Catalytic Properties of New Polymeric Monometallic Composites Based on Copolymers of Polypropylene Glycol Maleate Phthalate with Acrylic Acid.

Metal-polymer composites based on copolymers of polypropylene glycol maleate phthalate with acrylic acid and metallic nickel and silver were synthesized for the first time. The objects obtained were characterized by infrared (IR) and Raman spectroscopies, thermogravimetry, a scanning electron microscope with energy dispersive spectroscopy, and atomic emission spectrometry. The catalytic activity of new metal-polymer composites that exhibited a rather high efficiency in the reactions of electrocatalytic hydrogenation of pyridine was studied. It is shown that nanoparticles of metals are evenly distributed in the volume of the polymer matrix; more than 80% of nanoparticles are in the range from 25 to 40 nm and have spherical and rhombic shapes. The reusability of the obtained composites is shown.

Interrupted Pyridine Hydrogenation: Asymmetric Synthesis of δ-Lactams.

Metal‐catalyzed hydrogenation is an effective method to transform readily available arenes into saturated motifs, however, current hydrogenation strategies are limited to the formation of C−H and N−H bonds. The stepwise addition of hydrogen yields reactive unsaturated intermediates that are rapidly reduced. In contrast, the interruption of complete hydrogenation by further functionalization of unsaturated intermediates offers great potential for increasing chemical complexity in a single reaction step. Overcoming the tenet of full reduction in arene hydrogenation has been seldom demonstrated. In this work we report the synthesis of sought‐after, enantioenriched δ‐lactams from oxazolidinone‐substituted pyridines and water by an interrupted hydrogenation mechanism.

Catalytic Effects of Chemisorbed Sulfur on Pyridine and Cyclohexene Hydrogenation on Pd and Pt Clusters

Kinetic assessments of cyclohexene and pyridine hydrogenation on metallic Pd and Pt surfaces covered with chemisorbed sulfur species (H2S*, HS*, and S*) at controlled sulfur chemical potentials pro...

Electronic Effect in a Ruthenium Catalyst Designed in Nanoporous N-Functionalized Carbon for Efficient Hydrogenation of Heteroarenes.

Active metal catalysts are the key in chemical industry for sustainable production of multitude of chemical resources. Here, we report a new ruthenium (Ru) composite with a synergistically controlled nanostructure and electronic properties as a highly efficient hydrogenation catalyst which comprises stable small Ru nanoparticles (mean particle size, ca. 0.9 nm) in situ generated into a nanoporous N-functionalized carbon with high surface area (ca. 650 m2 g-1) and has strong electron-donating power of Ru sites of nanoparticles. The scalable and highly reusable catalyst, prepared from a self-assembled Ru complex, performs actively with low per metal usage under mild conditions (60-80 °C and 0.5-1.0 MPa H2) for selective hydrogenation of various quinolines and pyridines. The role of electron-donating properties of the new Ru nanohybrid for highly efficient catalysis was characterized by both experiments and computational studies. Density functional theory calculations reveal that weak adsorption energies of quinoline at the electron-rich Ru surface prevents poisoning caused by its strong coordination and provides excellent reusability of the catalyst, while low activation barriers for the hydrogenation steps of the N-heterocyclic ring correlate with high catalytic activity. Our catalyst exhibits 5-24-fold higher turnover frequency up to ca. 167 h-1 among the efficient noble metal catalysts reported for selective hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline.

A General Catalyst Based on Cobalt Core–Shell Nanoparticles for the Hydrogenation of N‐Heteroarenes Including Pyridines

AbstractHerein, we report the synthesis of specific silica‐supported Co/Co3O4 core–shell based nanoparticles prepared by template synthesis of cobalt‐pyromellitic acid on silica and subsequent pyrolysis. The optimal catalyst material allows for general and selective hydrogenation of pyridines, quinolines, and other heteroarenes including acridine, phenanthroline, naphthyridine, quinoxaline, imidazo[1,2‐a]pyridine, and indole under comparably mild reaction conditions. In addition, recycling of these Co nanoparticles and their ability for dehydrogenation catalysis are showcased.

A General Catalyst Based on Cobalt Core-Shell Nanoparticles for the Hydrogenation of N-Heteroarenes Including Pyridines.

Herein, we report the synthesis of specific silica‐supported Co/Co3O4 core–shell based nanoparticles prepared by template synthesis of cobalt‐pyromellitic acid on silica and subsequent pyrolysis. The optimal catalyst material allows for general and selective hydrogenation of pyridines, quinolines, and other heteroarenes including acridine, phenanthroline, naphthyridine, quinoxaline, imidazo[1,2‐a]pyridine, and indole under comparably mild reaction conditions. In addition, recycling of these Co nanoparticles and their ability for dehydrogenation catalysis are showcased.