Figure - uploaded by László Hegedűs
Content may be subject to copyright.
Source publication
Aims
This mini-review provides an overview of the recent achievements in the selective reduction of nitriles using both homogeneous and heterogeneous transition metal catalysts.
Background
Amines are important and valuable intermediates in the pharmaceutical, plastic and agrochemical industry.
Objective
There is an increasing interest in developi...
Contexts in source publication
Context 1
... recycling the studied catalyst was opposed by the deactivation. However, this process proved to be suitable for the selective formation of other aminonitriles from the corresponding aromatic dinitriles, such as terephthalonitrile, isophthalonitrile and phthalonitrile ( Table 5). The lowest catalytic activity was observed in the hydrogenation of the ortho-compound ( Table 5, entry 3) which was attributed to a steric effect. ...Context 2
... this process proved to be suitable for the selective formation of other aminonitriles from the corresponding aromatic dinitriles, such as terephthalonitrile, isophthalonitrile and phthalonitrile ( Table 5). The lowest catalytic activity was observed in the hydrogenation of the ortho-compound ( Table 5, entry 3) which was attributed to a steric effect. ...Similar publications
Primary 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 contin...
Silica supported ultrasmall Ni-nanoparticles allow for general and selective hydrogenation of all kinds of nitriles to primary amines under mild conditions. By calcination of a template material generated from Ni(ii)nitrate and colloidal silica under air and subsequent reduction in the presence of molecular hydrogen the optimal catalyst is prepared...
![The Ir(I) catalyst [IrClH{κP,P,Si−Si(Me)(C6H4‐2‐PⁱPr2)2}] (1) and the...](publication/370140238/figure/fig2/AS:11431281246403278@1716356040624/The-IrI-catalyst-IrClHkP-P-Si-SiMeC6H4-2-PPr22-1-and-the-ILs-BMMImBF4-and_Q320.jpg)
In 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 spe...
Despite its unique physicochemical properties, the catalytic application of nickel carbide (Ni3C) in organic synthesis is rare. In this study, we report well‐defined nanocrystalline Ni3C (nano‐Ni3C) as a highly active catalyst for the selective hydrogenation of nitriles to primary amines. The activity of the aluminum‐oxide‐supported nano‐Ni3C (nano...
A mixed oxide supported bimetallic catalyst Ni25.38Co18.21/MgO–0.75Al2O3 was readily prepared and found to be efficient in the hydrogenation of valeronitrile (VN) to amylamine (AA) under atmospheric pressure. Under the optimal conditions: H2 to VN molar ratio of 4:1, NH3 to VN molar ratio of 3:1, reaction temperature of 130 °C and residence time of...
Citations
... Although Ni-and Co-based sponge metals (Raney catalysts) are used for the hydrogenation of nitriles in industry, these catalysts are prone to significant deactivation during storage and require harsh reaction conditions due to their low activities. Thus far, various metal NP catalysts based on noble metals (i.e., Pt, Pd, Ru, Rh, Re, and Ir) and non-precious metals (i.e., Co and Ni) have been developed as alternatives to Raney catalysts [43][44][45][46][47] . In contrast, Fe NP catalysts are extremely rare, with only one recent report discussing the use of Fe/FeO x core-shell NPs supported on SiO 2 in the hydrogenation of nitriles 25 . ...
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.
... Primary amines obtained from nitriles by hydrogenation are valuable intermediates in the pharmaceutical, herbicide and plastic industries [2]. As well-known [3][4][5], conversion of the nitrile group to a primary amine takes place relatively easily over precious metal catalysts, but typically a mixture of primary, secondary and tertiary amines is formed in various consecutive and parallel reactions, due to the high reactivity of the imine intermediate (Scheme 1). A new process was developed by us for the selective liquid-phase heterogeneous catalytic hydrogenation of nitriles to primary amines [6], in which complete conversion of benzonitrile (1a), excellent selectivity (95%) and isolated yield (85-90%) of benzylamine (2a) could be achieved under mild reaction conditions (30 °C, 6 bar), over a 10% Pd/C catalyst (Selcat [7]), in a mixture of two immiscible solvents (e.g., water/dichloromethane) and in the presence of a medium acidic additive ( NaH 2 PO 4 ) (Scheme 2). ...
In this review the most important results achieved in the recent 12–15 years are summarized focusing on the heterogenous catalytic hydrogenations over transition metals (Pd, Pt, Ru, Rh, La), as well as the application of palladium, copper and other metals on a molecular sieve (4A) support in several organic chemical syntheses in liquid phase.
... As the Rh-Al/H 2 O system appears to work efficiently in C-C and C-O multiple bond hydrogenations, it was decided to further explore the hydrogenation of C-N multiple bond using nitriles as substrates [38], as well as the reduction of N-O bonds in nitro compounds [39,40]. As test reaction substrates, nitrobenzene (28), 2-nitrotoluene (32), and benzonitrile (35) were selected. ...
... Thus, it was explored how supported Rh catalysts perform in substrates which have multiple functional groups. Thus, an α,β-unsaturated carbonyl compound, isophorone (38) [43,44], was examined using 5% Rh/Al 2 O 3 catalyst at 50 • C. Isophorone can be hydrogenated to the corresponding saturated ketone (39) at 25 • C after 15 h with 100% selectivity at low conversion values (Scheme 9). After allowing a longer reaction time (22 h), the conversion increased; however, the product of the complete hydrogenation, the saturated alcohol (40), also appeared in the product mixture. ...
... Thus, it was explored how supported Rh catalysts perform in substrates which have multiple functional groups. Thus, an α,β-unsaturated carbonyl compound, isophorone (38) [43,44], was examined using 5% Rh/Al2O3 catalyst at 50 °C. Isophorone can be hydrogenated to the corresponding saturated ketone (39) at 25 ˚C after 15 h with 100% selectivity at low conversion values (Scheme 9). ...
Supported rhodium catalysts were screened to catalyze the one-step hydrogenation of a broad variety of functional groups. The results show that 5% Rh/Al2O3 and 5% Rh/C performed well in controlling selective hydrogenation under the desired amount of time and temperature. In this regard, partial and full hydrogenation were achieved by controlling reaction time or temperature. In addition to aliphatic C–C, C–N, C–O, and N–O multiple bonds, the applicability of this method was demonstrated by the hydrogenation of C=C double bonds of arenes, which is considered challenging. Importantly, the Al-H2O system producing hydrogen in situ and the high, controllable selectivity make this protocol environmentally benign and highly efficient.
... Among these methods, the reduction of N=X (X = C, O, H) bonds plays a key role. Generally, nitriles, nitro compounds and amides can be reduced to primary amines using borane [21,23,24], silane [25], hydrides [26], formats [20,27], alcohols [28], or molecular hydrogen [29]. Since Raney Ni was first prepared in 1905, it has become one of the most important catalysts for reduction. ...
Amines play an important role in synthesizing drugs, pesticides, dyes, etc. Herein, we report on an efficient catalyst for the general construction of amine mediated by nickel boride nanoclusters supported by a TS-1 molecular sieve. Efficient production of amines was achieved via catalytic hydrogenation of N=X (X = C, O, H) bonds. In addition, the catalyst maintains excellent performance upon recycling. Compared with the previous reports, the high activity, simple preparation and reusability of the Ni-B catalyst in this work make it promising for industrial application in the production of amines.
... 12 Some recent reviews have provided comprehensive reports on novelties for the development of heterogeneous or homogeneous catalytic hydrogenation of nitriles catalysed by transition metals. [13][14][15][16][17][18][19][20] In addition, general methods for the reduction of nitriles to primary amines and the selectivity problems have also been reported in detail. [3][4][5][6] Herein, we focus on the hydrogenation of pyridinecarbonitriles. ...
... Since both (aminomethyl)pyridines and -piperidines are highly volatile in their free base form, they were just released from their salts, when the analytical samples were prepared. Their spectroscopic data are the following: (38), 125 (19), 97 (21), 84(100), 56 (13). These analytical results are in accordance with the literature data. ...
An effective method for the chemoselective, liquid-phase heterogeneous catalytic hydrogenation of some pyridinecarbo-nitriles [4-, 3-or 2-pyridinecarbonitrile (4PN, 3PN, 2PN)] to the corresponding pyridyl- or piperidylmethylamines over a Pd/C catalyst was...
... 23 ), many catalysts were developed for this and related reactions ( Fig. 1) 24-42 . These achievements were mainly possible due to the design of precious metal systems, which allow reactions to be performed at low temperature and pressure 24,30,31,[33][34][35][36][37][38] . However, despite their tremendous success, their limited availability and higher price constitute major drawbacks. ...
... Thus, state-of-the-art catalysts for nitrile hydrogenation in industry continue to be Raney nickel 26,27,31,33 and copper chromite 29 , which demand harsh conditions and suffer from toxicity issues. To solve these problems, alternative nickel-and cobalt-based heterogeneous catalysts have been reported in recent years 35,[39][40][41] . ...
The hydrogenation of nitriles to amines represents an important and frequently used industrial process due to the broad applicability of the resulting products in chemistry and life sciences. Despite the existing portfolio of catalysts reported for the hydrogenation of nitriles, the development of iron-based heterogeneous catalysts for this process is still a challenge. Here, we show that the impregnation and pyrolysis of iron(II) acetate on commercial silica produces a reusable Fe/Fe–O@SiO 2 catalyst with a well-defined structure comprising the fayalite phase at the Si–Fe interface and α-Fe nanoparticles, covered by an ultrathin amorphous iron(III) oxide layer, growing from the silica matrix. These Fe/Fe–O core–shell nanoparticles, in the presence of catalytic amounts of aluminium additives, promote the hydrogenation of all kinds of nitriles, including structurally challenging and functionally diverse aromatic, heterocyclic, aliphatic and fatty nitriles, to produce primary amines under scalable and industrially viable conditions.
... It is well-known, that during the conversion of nitriles into primary amines secondary and tertiary amines can be formed in side reactions decreasing the selectivity of the reaction [6][7][8][9][10]. The amount of the secondary and tertiary amines in the reaction mixture can be minimized by the removal of the primary amine [11][12][13][14][15][16] or by the addition of excess ammonia [17][18][19][20]. ...
Nickel and lanthanum on MgO or MgO-Al 2 O 3 catalysts were prepared and characterized. The applicability of the catalysts was studied in the liquid-phase hydro-genation of benzonitrile. A La/MgO catalyst showed surprisingly high activity and selectivity. The scope of the reaction was extended to other nitriles (benzyl cyanide, cinnamonitrile, adiponitrile) over this La/MgO catalyst.
... For example, the hydroboration of nitriles provides synthetically useful borylamines [13] and offers a mild and alternative reduction strategy to the otherwise harsh conditions that are generally required for catalytic nitrile hydrogenation. [14] The hydroboration of carbonates or esters on the other hand, is important for developing method-ologies that utilize CO 2 as an eco-friendly C 1 feedstock. [15] Because of the stability of the C�N and C=O bond, both nitriles and carbonate/esters are difficult substrates in the hydroboration reaction. ...
During the past decade earth‐abundant metals have become increasingly important in homogeneous catalysis. One of the reactions in which earth‐abundant metals have found important applications is the hydroboration of unsaturated C−C and C−X bonds (X=O or N). Within these set of transformations, the hydroboration of challenging substrates such as nitriles, carbonates and esters still remain difficult and often relies on elaborate ligand designs and highly reactive catalysts (e. g., metal alkyls/hydrides). Here we report an effective methodology for the hydroboration of challenging C≡N and C=O bonds that is simple and applicable to a wide set of substrates. The methodology is based on using a manganese(II) triflate salt that, in combination with commercially available potassium tert‐butoxide and pinacolborane, catalyzes the hydroboration of nitriles, carbonates, and esters at room temperature and with near quantitative yields in less than three hours. Additional studies demonstrated that other earth‐abundant metal triflate salts can facilitate this reaction as well, which is further discussed in this report.
... Accordingly, the selective synthesis of primary amines is of significant importance. Several protocols have been developed to synthesize primary amines, such as reductive amination of carbonyl compounds [4,5], nucleophilic substitution of ammonia on haloalkanes [6], direct amination of alcohols with ammonia [7][8][9], and hydrogenation of nitro compounds [10][11][12], nitriles [13], and amides [14]. Among all the methods, the direct amination of alcohols with ammonia over heterogeneous catalysts is the most recommended protocol for commercial production of amines because of ready availability and low cost of alcohols compared to carbonyl compounds as raw materials in general. ...
... However, most of the developed heterogeneous processes were not compatible to the direct amination of primary aliphatic alcohols to the terminal primary amines [15]. Therefore, the selective hydrogenation of aliphatic nitriles to terminal primary amines might be a good alternative, because aliphatic nitriles can be obtained from primary alcohols and ammonia via dehydrogenation-amination over heterogeneous catalysts, being a green chemical process [16][17][18][19][20]. Nevertheless, the selective hydrogenation of aliphatic nitriles to the terminal primary amines is a complicated process due to the inevitable side reactions [13]. As shown in Scheme 1, the hydrogenation of nitrile 1 generates an imine intermediate 2. Due to the high reactivity of 2, a set of consecutive and parallel reactions takes place and leads to a mixture of primary 3, secondary 5 and tertiary amines 7 via imine intermediates 4 and 6. ...
... The key issue in the hydrogenation of nitriles to primary amines is to prevent the formation of secondary and tertiary amines. Generally, the introduction of ammonia is often used to increase the selectivity of the primary amine [13]. ...
A mixed oxide supported bimetallic catalyst Ni25.38Co18.21/MgO–0.75Al2O3 was readily prepared and found to be efficient in the hydrogenation of valeronitrile (VN) to amylamine (AA) under atmospheric pressure. Under the optimal conditions: H2 to VN molar ratio of 4:1, NH3 to VN molar ratio of 3:1, reaction temperature of 130 °C and residence time of 5 s, the conversion of VN reached 100% with a AA yield of 70.8%, and a diamylamine (DAA) yield of 25.9%. This catalyst was also active in the hydrogenation of other low carbon aliphatic nitriles to their corresponding primary amines. The characterization results revealed that the catalyst had the properties of large surface area, uniform and fine dispersion of metal particles in the form of Ni/Co alloy with synergy effect between the two metals, which endowed the catalyst with good catalytic performances in the hydrogenation reaction of aliphatic nitriles.
Graphic Abstract
... Direct hydrogenation of nitro compounds, amides and nitriles, being the most environmentally benign option, usually requires harsh conditions, elevated temperatures and pressure, Lewis acid additives and precious metal catalysts. [7][8][9][10] In addition, one of the main challenges of amide and nitrile hydrogenation is the lack of selectivity, resulting in formation of complex mixtures of primary, secondary and tertiary amines and imines. [11,12] Recently, catalytic hydroboration and hydrosilylation of nitriles earned the focus of many research groups due to the improved control of the course of the reaction accomplished by fine tuning of the metal catalysts and mild reaction conditions, allowing for improved functional group selectivity. ...
... The conventional catalytic systems developed for reduction of nitriles [8,16] have employed precious metals, those of the 2 nd and 3 rd transition metal rows of groups 8-10. Since among these metals ruthenium has showed the most prominent results in selective hydrogenation [10] and hydrosilylation of nitriles, [16] such systems have attracted attention in hydroboration reactions as well. Thus, in 2015, shortly after the first report on Mo-catalyzed addition of HBCat to RCN (R=Me, Ph), [19] Szymczak et al. disclosed catalytic dihydroboration of nitriles using a protonswitchable Ru complex 6 (Scheme 5A). ...
Catalytic reduction of nitriles is considered as an attractive and atom‐economical route to a diversity of synthetically valuable primary amines. Compared to other methods, dihydroboration approach has been developed relatively recently but has already attracted the attention of many research groups due to reasonably mild reaction conditions, selectivity control and the access to N,N‐diborylamines, which emerged as powerful reagents for C−N bond forming reactions. Early developments in catalytic dihydroboration of nitriles implied precious metal catalysts along with harsh conditions and prolonged reaction times, whereas recent advances mostly rely on base and main group metal catalytic systems with significantly improved profiles. This minireview aims to provide an overview of advances and challenges of dihydroboration of nitriles with d‐, f‐ and main group metal catalysts. Mechanistic features of different catalytic systems, functional group tolerance and scope of the methods are also presented. The synthetic utility of N,N‐diborylamies, beyond simple protodeborylation, is discussed in the aspect of N‐arylation, imine and amide synthesis.
