Reduction Of Nitroarenes Research Articles

Metal-free cascade reactions for one-pot tetrahydroquinoxaline construction through nitroarene reduction and imine hydrogenation with water

A metal-free one-pot cascade process of imines with B2cat2 and water has been developed to construct dihydroquinoxalinones and tetrahydroquinoxalines directly from readily available 2-nitroanilines or o-dinitrobenzenes with α-ketoesters and α-diketones.

One-pot tandem reduction and site-selective halogenation of nitroarenes.

Halogenated aryl amines are a widely used chemical feedstock in the pharmaceutical and agrochemical industries. Achieving a single regioselective product from the para-selective halogenation of the aryl ring is significantly challenging because of the presence of several C-H bonds with similar reactivities. In this study, single para-halogenated aniline derivatives were prepared by the cascade para-selective halogenation (Cl, Br) and reduction of nitrobenzene derivatives using a mixture of SnCl2/SnCl4 salts. The mechanistic study confirmed that the noncovalent interactions between the chalcogen bond and Sn salt were pivotal for achieving regioselectivity. This synthetic method was applied for the development of potent and highly selective positron emission tomography molecular probes for serotonin transporters.

Nitrate and nitroarene hydrogenations catalyzed by alkaline-earth nickel phosphide clathrates.

The alkaline-earth-containing nickel phosphide clathrates AeNi2P4 (Ae = Ba, Sr) are investigated as catalysts for the reduction of nitrate or nitroarenes in aqueous or ethanolic solution, respectively. While AeNi2P4 clathrates are inactive in their bulk polycrystalline form, they become active in nitrate hydrogenation after size reduction by either grinding or ball milling. However, while the clathrate structure remains intact after manual grinding, ball milling is of limited use as it results in significant clathrate degradation. Ground AeNi2P4 catalysts are also active in nitroarene hydrogenation. Condensation products such as azoxy- and azo-benzenes form early (4 h) but anilines accumulate after long reaction times (24 h). Unexpectedly, BaNi2P4 partially devinylates nitrostyrene to nitrobenzene. Overall, BaNi2P4 is more active than SrNi2P4 in both nitrate and nitroarene hydrogenation. These results showcase the potential utility of clathrates in a growing number of catalytic transformations.

Synergy of redox-activity and hemilability in thioamidato cobalt(III) complexes for the chemoselective reduction of nitroarenes to anilines: catalytic and mechanistic investigation.

Reduction of nitro-compounds to amines is one of the most often employed and challenging catalytic processes in the fine and bulk chemical industry. Herein, we present two series of mononuclear homoleptic and heteroleptic Co(III) complexes, i.e., [Co(LNS)3] and [Co(LNS)2L1L2]x+, respectively (x = 0 or 1, LNS = pyrimidine- or pyridine-thioamidato, L1/L2 = thioamidato, phosphine or pyridine), which successfully catalyze the transformation of nitroarenes to anilines by methylhydrazine. The catalytic reaction can be accomplished for a range of electronically and sterically diverse nitroarenes, using mild experimental conditions and low catalyst loadings, resulting in the corresponding anilines in high yields, with high chemoselectivity, and no side-products. Electronic and steric properties of the ligands play pivotal role in the catalytic efficacy of the respective complexes. In particular, complexes bearing ligands of high hemilability/lability and being capable of stabilizing lower metal oxidation-states exhibit the highest catalytic activity. Mechanistic investigations suggest the participation of the Co(III) complexes in two parallel reaction pathways: (a) coordination-induced activation of methylhydrazine and (b) reduction of nitroarenes to anilines by methylhydrazine, through the formation of Co(I) and Co-hydride intermediates.

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.

Microwave-assisted synthesis of copper-loaded polyamidoxime brushes as an efficient catalytic system for nitroarene reduction

The novel aspect of this research is that sepiolite is utilized for the first time as a substrate for the MAGP of acrylonitrile to develop a catalyst (Cu-AO-PB).

Easy recycling of nanoscale Fe2O3-based catalysts for nitroarene reduction to anilines by the pyrolysis of a metallogel

The pyrolysis product L of metallogel Fe-2B-N3 has highly efficient reductive catalytic property for the conversion of nitroaromatic compounds to amine compounds under mild condition and easy recycling.

Light-fuelled nitro-reduction via cascaded electron donor–acceptor complexes in aqueous media

Developed herein is a metal-free method for nitro reduction via cascade electron donor acceptor complex photoexcitation in aqueous media.

(Invited) High Yield and Selective Electrocatalytic Reduction of Nitroarenes via Polyoxometalate Redox-Mediated Chronoamperometry

Anilines are major commodity chemicals used extensively in the production of pharmaceuticals, dyes, and polymers. However, the typical methods for synthesizing anilines suffer from poor environmental sustainability. Here, we report an electrocatalytic route for the production of anilines that works in aqueous solution at room temperature and pressure, where the electrons and protons required to reduce the nitrobenzene precursors are obtained from water. Excellent selectivities are obtained for a range of anilines, including species with ortho-iodides that are very challenging to obtain by other methods. Our approach relies on the use of a polyoxometalate redox mediator that shuts off the direct electro-reduction of the nitrobenzene at the electrode surface and thus prevents unproductive side reactions. Given the scale and current environmental impact of global aniline production, this electrochemical route holds promise for the development of more sustainable processes for the production of these vital chemical feedstocks. Figure 1

Sequential Deposition of Polyaminothiophenols and Gold Nanoparticle on Wool Fabrics: Fabric Composites as Efficient Catalysts in the Reduction of Nitroarenes

AbstractMerino wool, a highly abundant natural fabric, was successfully transformed into a valuable substrate for preparing easily recoverable catalyst materials by depositing gold nanoparticles (AuNPs) through a series of modification steps. The functionality of wool was enhanced by cleaving‐SH groups using NaHS chemical reduction. Subsequently, the reduced wool keratin (WSH) was covalently attached to 3‐amino thiophenol (3‐ATP) or 4‐amino thiophenol (4‐ATP) monomers via S−S linkages. The surface was further modified by grafting P3ATP or P4ATP through oxidative polymerization of 3‐ATP or 4‐ATP using ammonium persulfate as an oxidant. Finally, AuNPs were deposited onto the P3ATP or P4ATP‐grafted wool (P3ATP‐g‐WSH or P4ATP‐g‐WSH) by immersing the samples in an aqueous HAuCl4 solution. Additionally, P3ATP or P4ATP‐coated composites (P3ATP/WSH or P4ATP/WSH) were prepared to assess the AuNP formation ability of the grafting. The structural and morphological changes occurred in the wool, and the presence of AuNPs was revealed by ATR‐FTIR, XPS, SEM, and contact angle. The catalytic performance of the AuNP‐containing composites in reducing various nitroarenes to aminoarenes using an excess of electron‐donor (NaBH4) was monitored by UV‐vis spectroscopy. The developed composites demonstrated high efficiency, reusability, and rapid catalytic activity, achieving the highest apparent rate constant of 3.79 min−1, even within 1 min.

Pd nanoparticles decorated N-doped holey graphene assembled on aluminum silicate fibers agglomerate for catalytic continuous-flow reduction of nitroarenes

Rational design and preparation of efficient fixed-bed catalysts for continuous-flow system are highly desired but remain daunting challenges. Herein, we report the synthesis of an assembly catalyst consisted of aluminium silicate fibers (ASFs) agglomerate and Pd nanoparticles (PdNP) decorated N-doped holey graphene (NHG) through a facile hydrothermal co-assembling strategy. Due to the interconnect network and porous structure, the as-obtained PdNP/NHG-ASFs assembly is suitable to be utilized as a fixed-bed catalyst for organic reactions in continuous-flow mode. The processing rate is much higher than that of the previously reported fixed-bed systems based on metal-based catalysts. In addition, the catalytic continuous-flow system displays a remarkable durability and good substrate generality to other substituted nitrobenzenes. This work provides rational design concept for efficient fixed-bed catalyst with dual active components and paves a way for the industrial application in organic synthesis.

Single Metal Atoms Anchored on N‐Doped Holey Graphene as Efficient Dual‐Active‐Component Catalysts for Nitroarene Reduction

AbstractDeveloping efficient catalysts for facilitating organic synthesis processes is a popular but challenging topic in modern chemical industries. A combination of active metals and an active support structure is, in theory, an effective strategy for boosting catalytic activity but such combinations have been rarely explored. Herein, a strategy for fabricating highly efficient dual‐active‐component catalysts (DACCs) is presented by anchoring single‐atom metals (M1; e.g., Pd1, Ni1, Co1, and Zn1) or double‐atomic metals (e.g., Pd1‐Co1, Pd1‐Ru1, and Pd1‐Ni1) on nitrogen‐doped holey graphene (NHG). Among the resultant DACCs, Pd1/NHG, which combines atomically dispersed metal species and an active NHG carbocatalyst, has been shown to display enhanced catalytic performance toward nitroarene reduction . In particular, its catalytic efficiency in reducing 4‐nitrophenol corresponds to a turnover frequency of 2.0 min−1, which is 97 times higher than the benchmark set by commercial Pd/C catalysts (5.0 wt.%), and vastly superior to those of its counterparts (e.g., NHG carbocatalyst and NHG supported Pd clusters. Notably, four intermediates and two active components (i.e., NHG and single‐atom Pd) in the nitroarene reduction process have been identified. This study presents an effective and versatile synthetic strategy to prepare DACCs through the combination of metallic catalysts and a carbocatalyst substrate.

Silver-catalyzed reduction of nitro to amines in water

Silver-catalyzed reduction of nitro to amines in water

Impact of nanoplastics on the biodegradation, ecotoxicity, and key genes involved in imidacloprid metabolic pathways in papyrus (Cyperus papyrus L.)

Both nanoplastics (NPs) and imidacloprid (IMI) are widely distributed in the environment and have attracted significant attention due to their adverse effects on ecosystems. Constructed wetlands have the potential to remove IMI, but there is still limited understanding of how wetland plants interact with IMI, especially when influenced by different charged NPs. This study assessed their ecotoxicological effects, as well as the fate and transformation of IMI in papyrus (Cyperus papyrus L.) under the influence of different charged NPs and identified key driving genes in the plant. Results show that simultaneous exposure to positively charged PS-NH2 and IMI inhibited plant growth. The combined action of NPs and IMI intensified their toxicity, enhancing lipid peroxidation and altering antioxidant enzyme activities. The IMI removal efficiency, which was primarily driven by biodegradation, was 80.61%, 88.91%, and 74.71% in the IMI-alone, co-IMI/PS_COOH, and co-IMI/PS_NH2 systems, respectively. PS-NH2 restricted the roots-to-shoots translocation ability of IMI. PS-COOH enhanced IMI oxidation and nitro reduction, while PS-NH2 inhibited 2-OH-IMI dehydrogenation to IMI-olefin in papyrus. Transcriptomics and gene network analysis identified the genes encoding CYP450 enzymes, reductases, hydrolases, dehydrogenases, and peroxidases as those influencing IMI biodegradation. These enzymes play a crucial role in the hydroxylation, dehydrogenation, reduction, and oxidation processes during biodegradation of IMI in the presence of NPs. This study expands the understanding of the impact of differently charged NPs on the IMI remediation efficacy of papyrus, thus providing new insights into the phytoremediation of organic contaminants in constructed wetlands.

Boron Triiodide-Mediated Reduction of Nitroarenes Using Borohydride Reagents.

The reduction of nitroarenes using KBH4 and I2 is described. BI3 is generated in situ and was shown to be the active reductant. Conditions were optimized for BI3 generation and then applied to a wide range of nitroarenes, including traditionally challenging substrates. The method constitutes a practical reduction option which produces low-toxicity boric acid and potassium iodide upon workup.

Photoinduced Reduction of Nitroarenes and Tandem C-N Cross-Coupling with Haloarenes.

An efficient photocatalytic C-N cross-coupling of nitroarenes with haloarenes has been developed using simple and cheap Ni(acac)2 as a cocatalyst. The reaction is confirmed as a stepwise process: (1) metal free photoinduced reduction of nitroarenes into aniline derivatives and (2) photo- and Ni-catalyzed C-N cross-coupling of anilines with haloarenes. The reaction conditions are simple and mild, giving high-value diarylamines with good to excellent yields and good functional group tolerance.

CS2/KOH System-Promoted Stereoselective Synthesis of (E)-Alkenes from Diarylalkynes and a "Hidden" Zinin-Type Reduction of Nitroarenes into Arylamines.

In this work, we present the CS2/KOH system as a practical and efficient reductive medium for obtaining (E)-alkenes from alkynes through a highly stereoselective semireduction reaction. This cost-effective system enabled successful semireduction reactions of diverse alkynes using water as a hydrogen source, yielding moderate to excellent yields. The versatility of this protocol is further demonstrated through the synthesis of relevant compounds such as pinosylvin and resveratrol precursors, along with the notable anticancer agent DMU-212. Furthermore, during the reaction scope investigation, we serendipitously disclosed that this reductive system was also able to promote a Zinin-type reaction to reduce nitroarenes into arylamines.

Selective Reduction of Nitro Compounds by Organosilanes Catalyzed by a Zirconium Metal-Organic Framework Supported Salicylaldimine-Cobalt(II) Complex.

Reducing nitro compounds to amines is a fundamental reaction in producing valuable chemicals in industry. Herein, the synthesis and characterization of a zirconium metal-organic framework-supported salicylaldimine-cobalt(II) chloride (salim-UiO-CoCl) and its application in catalytic reduction of nitro compounds are reported. Salim-UiO-Co displayed excellent catalytic activity in chemoselective reduction of aromatic and aliphatic nitro compounds to the corresponding amines in the presence of phenylsilane as a reducing agent under mild reaction conditions. Salim-UiO-Co catalyzed nitro reduction had a broad substrate scope with excellent tolerance to diverse functional groups, including easily reducible ones such as aldehyde, keto, nitrile, and alkene. Salim-UiO-Co MOF catalyst could be recycled and reused at least 14 times without noticeable losing activity and selectivity. Density functional theory (DFT) studies along with spectroscopic analysis were employed to get into a comprehensive investigation of the reaction mechanism. This work underscores the significance of MOF-supported single-site base-metal catalysts for the sustainable and cost-effective synthesis of chemical feedstocks and fine chemicals.

Nitro reduction involving PEG200(4)@C@MoSe2@MWCNT driven by UV light

A mild and green nitro-reduction method was developed using PEG200(4)@C@MoSe2@MWCNT driven by UV light. The photocatalytic performance of MoSe2 was enhanced by MWCNTs and polyethylene glycol, and the catalyst was characterized by SEM, TEM, XRD, and TGA. Eleven reduction applications had been accomplished, in which the conversion of 3-nitrobenzonitrile reached up to >99% and the selectivity of 3-aminobenzonitrile reached up to 74%. Although the selectivity of the target products was low, it provided a new approach for the photocatalytic reduction of nitroaromatics and also brought new insights into the photocatalytic application of MoSe2.

Hydrogenation Catalysis by Hydrogen Spillover on Platinum‐Functionalized Heterogeneous Boronic Acid‐Polyoxometalates

AbstractThe activation of molecular hydrogen is a key process in catalysis. Here, we demonstrate how polyoxometalate (POM)‐based heterogeneous compounds functionalized with Platinum particles activate H2 by synergism between a hydrogen spillover mechanism and electron‐proton transfer by the POM. This interplay facilitates the selective catalytic reduction of olefins and nitroarenes with high functional group tolerance. A family of polyoxotungstates covalently functionalized with boronic acids is reported. In the solid‐state, the compounds are held together by non‐covalent interactions (π–π stacking and hydrogen bonding). The resulting heterogeneous nanoscale particles form stable colloidal dispersions in acetonitrile and can be surface‐functionalized with platinum nanoparticles by in situ photoreduction. The resulting materials show excellent catalytic activity in hydrogenation of olefins and nitrobenzene derivatives under mild conditions (1 bar H2 and room temperature).