Hydrogenation Of Nitriles Research Articles

Unraveling the Metal–Ligand Cooperativity in a Phosphine-Free Mn(II)-Catalyzed Transfer Hydrogenation of Nitriles to Primary Amines and Dehydrogenation of Dimethylamine Borane

Unraveling the Metal–Ligand Cooperativity in a Phosphine-Free Mn(II)-Catalyzed Transfer Hydrogenation of Nitriles to Primary Amines and Dehydrogenation of Dimethylamine Borane

Practical electrochemical hydrogenation of nitriles at the nickel foam cathode.

We report a scalable hydrogenation method for nitriles based on cost-effective materials in a very simple two-electrode setup under galvanostatic conditions. All components are commercially and readily available. The method is very easy to conduct and applicable to a variety of nitrile substrates, leading exclusively to primary amine products in yields of up to 89% using an easy work-up protocol. Importantly, this method is readily transferable from the milligram scale in batch-type screening cells to the multi-gram scale in a flow-type electrolyser. The transfer to flow electrolysis enabled us to achieve a notable 20 g day-1 productivity of phenylethylamine at a geometric current density of 50 mA cm-2 in a flow-type electrolyser with 48 cm2 electrodes. It is noteworthy that this method is sustainable in terms of process safety and reusability of components.

Structural Ni0-Niδ+ Pair Sites for Highly Active Hydrogenation of Nitriles to Primary Amines.

Supported metal pair sites have sparked interest due to their tremendous potential as bifunctional catalysts. Here, we report the structural Ni0-Niδ+ pair sites constructed in a well-defined nanocrystal phase of Ni3P. These Ni0-Niδ+ pair sites exhibited a remarkable product formation rate of 123 molBA/molmetal/h for the hydrogenation of benzonitrile (BN) to benzylamine (BA). The heterogeneity of surface Ni atoms over the Ni3P crystal created two types of metal centers, Ni0 and Niδ+, with a specific spatial distance of 4-5 Å. The Ni0 site acted as the center for H2 activation, while the Niδ+ site served as the adsorption and activation center for the C ≡ N group. The highly efficient cooperation effect of Ni0-Niδ+ pair sites resulted in a TOF of 2915 h-1 in BN hydrogenation, which is 2.4 and 9.7 times higher than that over the mono-Ni0 and -Niδ+ sites, respectively.

Tuning the Selectivity of Catalytic Nitrile Hydrogenation with Phase-Controlled Co Nanoparticles Prepared by Hydrosilane-Assisted Method.

Cobalt (Co) is a promising candidate to replace noble metals in the hydrogenation process, which is widely employed in the chemical industry. Although the catalytic performance for this reaction has been considered to be significantly dependent on the Co crystal phase, no satisfactory systematic studies have been conducted, because it is difficult to synthesize metal nanoparticles that have different crystalline structures with similar sizes. Here we report a new method for the synthesis of cobalt nanoparticles using hydrosilane as a reducing agent (hydrosilane-assisted method). This new method uses 1,3-butanediol and propylene glycol to successfully prepare fcc and hcp cobalt nanoparticles, respectively. These two types of Co nanoparticles have similar sizes and surface areas. The hcp Co nanoparticles exhibit higher catalytic performance than fcc nanoparticles for the hydrogenation of benzonitrile under mild conditions. The present hcp Co catalyst is also effective for highly selective benzyl amine production from benzonitrile without ammonia addition, whereas many catalytic systems require ammonia addition for selective benzyl amine production. Mechanistic studies revealed that the fast formation of the primary amine and the prevention of condensation and secondary amine hydrogenation promote selective benzonitrile hydrogenation for benzylamine over hcp Co nanoparticles.

Insight into the MOtBu (M=Na, K)-Mediated Dehydrogenation of Dimethylamine-Borane and Transfer Hydrogenation of Nitriles to Primary Amines.

Selective synthesis of primary amines from nitriles is challenging in synthetic chemistry due to the possible en-route generation of various amines and imines. Herein, we report a practical and operationally simple MOtBu-mediated (M=Na, K) transfer hydrogenation of nitriles to the corresponding primary amines with a relatively unexplored sacrificial hydrogen source (dimethylamine borane). The strategy encompasses a broad substrate scope under transition metal-free conditions and does not require any solvent. The mechanistic investigation was performed with the aid of control experiments and spectroscopic studies. The GC analysis of the reaction mixture exhibited the evolution of the H2 gas. Additionally, detailed computational calculations were undertaken to shed light on the possible intermediates and transition states involved during the present protocol.

Continuous Hydrogenation of Nitriles to Primary Amines with High Selectivity in Flow by Using Raney Cobalt

AbstractPrimary amines produced by selective catalytic hydrogenation of cyano compounds are widely used as basic chemicals, but due to the complexity of the hydrogenation mechanism and the inefficient mass transfer of the intermittent reaction, the process tends to produce secondary and tertiary amines as undesirable by‐products. In this research, a continuous hydrogenation system employing a micropacked‐bed reactor (μPBR) was established for the catalytic hydrogenation of 3‐ethylaminopropionitrile (3‐EAPN) to synthesize N‐ethyl‐1,3‐propanediamine (3‐EAPA). Under optimal experimental conditions using Raney cobalt as a catalyst, complete conversion of 3‐EAPN was achieved, and a high selectivity of 99.6 % for the primary amine (3‐EAPA) was obtained. On this basis, the system was extended with other cyano compounds of different structures as hydrogenation substrates, demonstrating the general applicability of this continuous hydrogenation system by using Raney cobalt as a catalyst in a μPBR for the hydrogenation of various nitriles.

Recent Advances in Catalytic Systems for the Reduction of Aromatic and Aliphatic Nitrile Compounds to Amines.

Amines are important and valuable compounds widely used in the chemical industry to produce various products such as dyes, detergents, solvents, additives, pharmaceutical products, and anti-foam agents. A property that distinguishes primary amines from other compounds is their straightforward functionalization. Therefore, the synthesis of different amine compounds has been considered by many researchers in recent years. Usually, primary amines are produced via amination of alcohols, reductive amination, and reduction of nitro and amide compounds. Furthermore, a useful and atom-economical method for producing primary amines is reducing nitrile compounds using catalytic systems. Traditionally, nitriles are reduced using metal hydrides such as LiAlH4 or NaBH4. These methods have important restrictions in terms of selectivity and waste generation. Hence, the heterogeneous and homogeneous catalysts were investigated for the hydrogenation of nitriles to diverse amines. This review describes the performance of different catalytic systems for reducing nitrile compounds to their corresponding amines.

Air-Stable and Highly Active Transition Metal Phosphide Catalysts for Reductive Molecular Transformations

This review introduces transition metal phosphide nanoparticle catalysts as highly efficient and reusable heterogeneous catalysts for various reductive molecular transformations. These transformations include the hydrogenation of nitriles to primary amines, reductive amination of carbonyl compounds, and biomass conversion, specifically, the aqueous hydrogenation reaction of mono- and disaccharides to sugar alcohols. Unlike traditional air-unstable non-precious metal catalysts, these are stable in air, eliminating the need for strict anaerobic conditions or pre-reduction. Moreover, when combined with supports, metal phosphides exhibit significantly enhanced activity, demonstrating high activity, selectivity, and durability in these hydrogenation reactions.

An efficient and stable LDH-derived Ni catalyst for highly selective hydrogenation of nitriles to primary amines

Transformation of nitriles into amines is highly desired, yet stable non-noble metal heterogeneous catalysts for efficiently selective production of primary amine are still lacking.Herein, for the first time we reported a Zr-doped yolk-shell structured Ni-based catalyst derived from layered double hydroxides (LDH) in the selective hydrogenation of nitriles to primary amines. The prepared catalyst exhibited higher primary amine yield (benzylamine yield >99.9 %) and significantly higher stability (>200 h) than highly efficient Ni catalysts that are reported previously in the selective hydrogenation of benzonitrile. Other nitriles are transformed into primary amines with good yields (90–100 %). The strong interaction between Ni0yolk and shell investsNiAl catalysts with robust stability. Importantly, Zr promotes the migration of Ni2+in the shell, resulting in appropriate acidity and better hydrogen activation capability, which drives the reaction aggressively to the BA formation pathway, and thussuccessfully enhances the yield of primary amine above 99.9 %.

Nickel Carbide Nanoparticle Catalyst for Selective Hydrogenation of Nitriles to Primary Amines.

Despite its unique physicochemical properties, the catalytic application of nickel carbide (Ni3 C) in organic synthesis is rare. In this study, we report well-defined nanocrystalline Ni3 C (nano-Ni3 C) as a highly active catalyst for the selective hydrogenation of nitriles to primary amines. The activity of the aluminum-oxide-supported nano-Ni3 C (nano-Ni3 C/Al2 O3 ) catalyst surpasses that of Ni nanoparticles. Various aromatic and aliphatic nitriles and dinitriles were successfully converted to the corresponding primary amines under mild conditions (1 bar H2 pressure). Furthermore, the nano-Ni3 C/Al2 O3 catalyst was reusable and applicable to gram-scale experiments. Density functional theory calculations suggest the formation of polar hydrogen species on the nano-Ni3 C surface, which were attributed to the high activity of nano-Ni3 C towards nitrile hydrogenation. This study demonstrates the utility of metal carbides as a new class of catalysts for liquid-phase organic reactions.

Electrohydrogenation of Nitriles with Amines by Cobalt Catalysis.

Catalytic hydrogenation of nitriles represents an efficient and sustainable one-step synthesis of valuable bulk and fine chemicals. We report herein a molecular cobalt electrocatalyst for selective hydrogenative coupling of nitriles with amines using protons as the hydrogen source. The key to success for this reductive reaction is the use of an electrocatalytic approach for efficient cobalt-hydride generation through a sequence of cathodic reduction and protonation. As only electrons (e- ) and protons (H+ ) as the redox equivalent and hydrogen source, this general electrohydrogenation protocol is showcased by highly selective and straightforward synthesis of various functionalized and structurally diverse amines, as well as deuterium isotope labeling applications. Mechanistic studies reveal that the electrogenerated cobalt-hydride transfer to nitrile process is the rate-determining step.

Electrohydrogenation of Nitriles with Amines by Cobalt Catalysis

AbstractCatalytic hydrogenation of nitriles represents an efficient and sustainable one‐step synthesis of valuable bulk and fine chemicals. We report herein a molecular cobalt electrocatalyst for selective hydrogenative coupling of nitriles with amines using protons as the hydrogen source. The key to success for this reductive reaction is the use of an electrocatalytic approach for efficient cobalt‐hydride generation through a sequence of cathodic reduction and protonation. As only electrons (e−) and protons (H+) as the redox equivalent and hydrogen source, this general electrohydrogenation protocol is showcased by highly selective and straightforward synthesis of various functionalized and structurally diverse amines, as well as deuterium isotope labeling applications. Mechanistic studies reveal that the electrogenerated cobalt‐hydride transfer to nitrile process is the rate‐determining step.

Hydrogenation of nitriles to primary amines over a highly dispersed Ni/SiC catalyst without ammonia addition

Ni/SiC showed high performance for the hydrogenation of nitriles to primary amines without ammonia addition, which may originate from the natural properties of SiC and highly dispersed Ni species.

Aminophosphine PNH complexes of Mn(I), Fe(II), and Co(II) and evaluation of their activities in the transfer hydrogenation of nitriles.

A series of Mn(I), Fe(II), and Co(II) complexes with PNH ligands bearing secondary amine functionality were prepared and tested in the catalytic transfer hydrogenation of nitriles using ammonia borane as a hydrogen source. Among all tested complexes, a tetracoordinate Fe(II) bromide, (PNH)FeBr2, proved the most effective, representing a rare example of a highly active iron-based catalytic system for transfer hydrogenation reactions beyond carbonyl compounds and the first example of the iron catalyst for the transfer hydrogenation of nitriles to the corresponding primary amines. Mechanistic studies point out a metal-ligand cooperative mechanism enabled by the secondary amine moiety of the PNH ligand.

Iron phosphide nanocrystals as an air-stable heterogeneous catalyst for liquid-phase nitrile hydrogenation

Iron-based heterogeneous catalysts are ideal metal catalysts owing to their abundance and low-toxicity. However, conventional iron nanoparticle catalysts exhibit extremely low activity in liquid-phase reactions and lack air stability. Previous attempts to encapsulate iron nanoparticles in shell materials toward air stability improvement were offset by the low activity of the iron nanoparticles. To overcome the trade-off between activity and stability in conventional iron nanoparticle catalysts, we developed air-stable iron phosphide nanocrystal catalysts. The iron phosphide nanocrystal exhibits high activity for liquid-phase nitrile hydrogenation, whereas the conventional iron nanoparticles demonstrate no activity. Furthermore, the air stability of the iron phosphide nanocrystal allows facile immobilization on appropriate supports, wherein TiO2 enhances the activity. The resulting TiO2-supported iron phosphide nanocrystal successfully converts various nitriles to primary amines and demonstrates high reusability. The development of air-stable and active iron phosphide nanocrystal catalysts significantly expands the application scope of iron catalysts.

Promising Catalytic Application by Pincer Metal Complexes: Recent Advances in Hydrogenation of Carbon‐Based Molecules

AbstractIn the last two decades, pincer metal complexes have been highly utilized as catalysts for a variety of organic transformations in both industrial and social applications. Owing to the extraordinary chemical characteristics, such as extra thermal stability and easy functionalization, they were extensively utilized for generating novel catalytic species. Besides, the catalytic activity of these pincer metal complexes was achieved with high atom economy and eco‐friendly routes. Recently, the catalysts exhibited excellent behaviour towards various immerging systems, such as the hydrogenation of CO2, nitriles, amides, esters, olefins and alkynes, which are valuable for industrial production, academic research, and green environment. The main goal of this reviewwas to highlight how pincer metal complexes function in these catalytic hydrogenation reactions, as well as their mechanistic studies. Specifically, we focus on the most updated advancements in hydrogenation in the last few years. Some outlooks and future suggestions for further related work conclude the paper.

Designed Nanomaterials for Electrocatalytic Organic Hydrogenation Using Water as the Hydrogen Source.

ConspectusThe hydrogenation reaction is one of the most frequently used transformations in organic synthesis. Electrocatalytic hydrogenation by using water (H2O) as the hydrogen source offers an efficient and sustainable approach to synthesize hydrogenated products under ambient conditions. Such a technique can avoid the use of high-pressure and flammable hydrogen gas or other toxic/expensive hydrogen donors, which usually cause environmental, safety, and cost concerns. Interestingly, utilizing easily available heavy water (D2O) for deuterated syntheses is also attractive due to the widespread applications of deuterated molecules in organic synthesis and the pharmaceutical industry. Despite impressive achievements, electrode selection mainly relies on trial-and-error modes, and how electrodes dictate reaction outcomes remains elusive. Therefore, the rational design of nanostructured electrodes for driving the electrocatalytic hydrogenation of a series of organics via H2O electrolysis is developed.In this Account, we review recent advances in the electrocatalytic hydrogenation of different types of organic functional groups, including C≡C, C≡N, C═C, C═O, and C-Br/I bonds, -NO2, and N-heterocycles, with H2O over nanostructured cathodes. First, the general reaction steps (reactant/intermediate adsorption, active atomic hydrogen (H*) formation, surface hydrogenation reaction, product desorption) are analyzed, and key factors are proposed to optimize hydrogenation performance (e.g., selectivity, activity, Faradaic efficiency (FE), reaction rate, and productivity) and inhibit side reactions. Then, ex situ and in situ spectroscopic tools to study key intermediates and interpret mechanisms are introduced. Third, based on the knowledge of key reaction steps and mechanisms, we introduce catalyst design principles in detail on how to optimize the adoption of reactants and key intermediates, promote the formation of H* from water electrolysis, inhibit hydrogen evolution and side reactions, and improve the selectivity, reaction rate, FEs, and space-time productivity of products. We then introduce some typical examples. (i) P- and S-modified Pd can decrease C═C adsorption and promote H* formation, enabling semihydrogenation of alkynes with high selectivity and FEs at lower potentials. Then, creating high-curvature nanotips to concentrate the substrates further speeds up the hydrogenation process. (ii) By introducing low-coordination sites into Fe and combining low-coordination sites and surface fluorine to modify Co to optimize the adsorption of intermediates and facilitate H* formation, hydrogenation of nitriles and N-heterocycles with high activity and selectivity is obtained. (iii) By forming isolated Pd sites to induce a specific σ-alkynyl adsorption of alkynes and steering S vacancies of Co3S4-x to preferentially adsorb -NO2, hydrogenation of easily reduced group-decorated alkynes and nitroarenes with high chemoselectivity is realized. (iv) For gas reactant participated reactions, by designing hydrophobic gas diffusion layer-supported ultrasmall Cu nanoparticles to enhance mass transfer, improve H2O activation, inhibit H2 formation, and decrease ethylene adsorption, ampere-level ethylene production with a 97.7% FE is accomplished. Finally, we provide an outlook on the current challenges and promising opportunities in this area. We believe that the electrode selection principles summarized here provide a paradigm for designing highly active and selective nanomaterials to achieve electrocatalytic hydrogenation and other organic transformations with fascinating performances.

Atomic-Dispersed Rh Enables Efficient Catalytic Nitrile Hydrogenation: Size Effect and Metal-Dependent Effect

The hydrogenation of nitriles to amines, as an atom-economical synthetic route, has attracted wide attention in industrial production. Despite that some catalysts for nitrile hydrogenation have been investigated in recent years, achieving high activity and selectivity in this process remains a major challenge. Here, we fabricated an atomically dispersed Rh catalyst anchored on defect-rich nanodiamond-graphene (ND@G) via a deposition–precipitation strategy (Rh1/ND@G), which showed the highest activity (TOF = 2592 h–1) in the hydrogenation of benzonitrile reaction among all the known catalysts under mild reaction conditions (333 K, 0.6 MPa H2), and delivered high selectivity (>99%) toward secondary amines. Significantly, we prepared the Rh-cluster catalyst (Rhn/ND@G) and a series of atomically dispersed M1 catalysts (M = Rh, Ru, Pd, Ir, and Pt) to understand the size effect and metal-dependent effect in the hydrogenation of benzonitrile. Experimental and theoretical investigations revealed that the Rh1/ND@G catalyst has higher selectivity toward dibenzylamine than Rhn/ND@G, as it is less likely to form benzylamine on the Rh1 active sites. Meanwhile, the difference of adsorption energies (as a catalyst descriptor) between benzylideneimine and benzonitrile was used to understand the activity of benzonitrile hydrogenation influenced by the metal-dependent effect of M1 catalysts. Modulating the size and metal-dependent effects could lead to high catalytic performance, paving the way to design efficient nitrile hydrogenation catalysts.

Green and efficient synthesis of primary amine from nitrile catalyzed by Pd-Ni oxide nanocluster

The selective hydrogenation of nitrile represents an atom-economical and reliable method to synthesize primary amine, a privileged compound in chemistry, biology, and medicine. However, this approach often displays severe selectivity issues, and additives or reducing agents are generally required to solve this problem. In this work, we aim to synthesize primary amine on a green catalytic system and probe into the catalytic mechanism of Pd-Ni interaction using benzonitrile (BN) as a model compound. The nitrile hydrogenation reaction was catalyzed by bimetallic Pd-Ni oxide nanospecies confined in Silicalite‑1 (S-1) zeolite using H2 as hydrogen donor without any additive which was environmentally friendly and economic. A 92% yield of benzylamine (BA) was achieved on the Pd0.6Ni@S-1 catalyst with a turnover number (TON) of 1667, and such BA yield was still maintained in upscaling experiment. Detailed characterizations shed light on the mechanism of the extraordinary performance of Pd-Ni oxide nanospecies on base-free nitrile hydrogenation.

Highly efficient and stable rhenium modified nickel catalyst for hydrogenation of nitriles to primary amines

Hydrogenation of nitriles confronts the challenge between hydrogenation and self-coupling of the intermediates. Here, a high selectivity of more than 96% at a conversion of 100% was achieved on the Ni-Re/SiO2 catalyst in the 3-hydroxypropionitrile hydrogenation to 3-aminopropan-1-ol, moreover, with an outstanding long-term stability, which were ascribed to the contributive role of Re in facilitating the hydrogen dissociation and intermediates adsorption.