Reduction Of Nitro Group Research Articles

Selective C6‐Nitration of Benzothiazolones with Iron Nitrate

AbstractWe report here a selective C6‐nitration of benzothiazolones in the presence of iron nitrate as nitro source. A series of novel 6‐nitrobenzothiazolin‐2‐one derivatives were prepared with moderate to excellent yields at room temperature. The method shows good regioselectivity, broad substrate scope and excellent compatibility with functional groups. Further transformations were performed for the reduction of nitro groups, amination of carbonyl groups and alkylation of amine at the 3‐position in the product.

Fabrication of CdIn2S4/ZnS S-scheme heterojunction via in-situ phase transformation for boosting photocatalytic conversion of organic compounds

Developing efficient photocatalysts is one of green and low cost tactic for addressing the environmental deterioration and energy crisis. Therefore, it remains a fantastic and important strategy to design an efficient junction between different semiconductors for harvesting solar light, boosting the redox capability. Herein, the fabrication of ZnS in situ decorated CdIn2S4 (referred to as CIS-Zx) were prepared by converting ZnS particles on Cd2In4S surface by a facile cation exchange method during solvothermal synthesis. According to a series of PEC measurements and DFT calculations, the bending of band edge as well as the establishing of built-in electric field in the interface of CIS/ZnS heterojunction were concluded, causing the formation of in-situ S-scheme heterojunctions in CdIn2S4/ZnS. The in-situ S-scheme heterojunctions can effectively ameliorate the migration behaviors of photo-generated charges. Compared with pure CdInS4, ZnS and physically mixed CdIn2S4/ZnS, the CIS-Zxin-situ S-scheme heterojunction exhibits efficient photocatalytic activity and stability in the selective reduction of aromatic nitro compounds and oxidation of aromatic alcohols, it is hoped that this work will open up a new avenue for innovative applications of in-situ S-scheme heterojunctions.

Gradual spin crossover behavior encompasing room temperature in an iron(II) complex based on a heteroscorpionate ligand.

In this paper, we report the synthesis of six novel triazole-based heteroscorpionate ligands based on heterocycle metathesis reactions and their iron(II) complexes. Single crystal structure analyses were performed, the spectroscopic and magnetic properties of the obtained complexes were studied and their spin crossover-structural relationships were compared to those obtained for their pyrazole-based analogues reported in the literature. In particular, the amino derivative complex bis[hydrobis(pyrazol-1-yl)(3-amino-1,2,4-triazol-1-yl)]iron(II) obtained by post-synthetic catalytic nitro-group reduction under pressure of hydrogen in an autoclave presents a scarce gradual spin crossover behavior at room temperature. The profile of the SCO curve can be explained by the presence of only relatively weak H bonds, spreading only in one dimension. Among the interesting spin transition behaviors observed for the different complexes, such stable, complete and gradual spin crossover at room temperature makes this neutral complex a good candidate for sublimation and future investigation as an active element notably for thermoreflectance-based surface microthermometry applications.

Selective Reduction of Nitroarenes via Noncontact Hydrogenation.

In traditional hydrogenation, where H2 and substrates with unsaturated bonds are activated on the same catalyst (contact mode), competitive hydrogenation of multiple reducible groups often occurs. We employ an unbiased H-cell for selective hydrogenation of the nitro group when multiple reducible groups are present. The setup spatially separates H2 and nitroarenes into two chambers connected by a proton-exchange membrane, thus adding barriers for a Langmuir-Hinshelwood-type mechanism that is common in thermocatalytic hydrogenation. Through a unique proton/electron transfer pathway that is specific to nitro functional group reduction to hydroxylamine, side reactions like C═C, C═O, and C≡C bond hydrogenation are fully avoided. Using Pd/C for H2 activation, and CNT for selective proton/electron transfer to -NO2 groups while being inert to C≡C, C═C, and C═O hydrogenation, the system effectively eliminates the competitive hydrogenation, achieving 100% nitro-group reduction selectivity in the hydrogenation of various nitroarenes, in sharp contrast to negligible selectivity over the same catalysts in a batch reactor under contact mode. This device enables selectivity control in hydrogenation reactions, moving beyond the traditional focus on catalyst active site engineering.

Enhanced Efficiency of Novel Green and Urea Mediated CuCo2O4 Nanocomposites for Acetaminophen Drug Loading, Accessible Catalytic Reduction of Nitro Compounds and Adsorption of Pesticides

Enhanced Efficiency of Novel Green and Urea Mediated CuCo2O4 Nanocomposites for Acetaminophen Drug Loading, Accessible Catalytic Reduction of Nitro Compounds and Adsorption of Pesticides

Electrochemical generation of H*-•OH redox pair for rapid removal of refractory nitro-organic micropollutants

This study developed an innovative reduction-oxidation coupling process for treatment of refractory organic wastewater. We constructed a series of N5-coordinated transition metals (TMs) (TMs = Mn, Fe, Co, Ni, Cu) single-atom sites supported on nitrogen-rich carbon nitride (SA-TM-C3N5) for electrochemical generation of the surface-adsorbed hydrogen atom (H*) and hydroxyl radical (•OH). The SA-Co-C3N5 exhibited the highest activity for production of the H*-•OH redox pair, which effectively degraded refractory nitro-organic micropollutants via the parallel reduction-oxidation pathways. The SA-Co-C3N5-mediated electro-Fenton-like system showed high removal efficiency (99 %) and mineralization capacity (78 %) toward metronidazole (MNZ) with low energy consumption (0.019 kWh (g TOC)–1). The trifunctional properties of the H* have contributed to the reduction of nitro compounds, the 2e– ORR for H2O2 production and the Fenton-like catalysis for •OH generation. This work sheds lights on the development of advanced reduction-oxidation coupling process for green and sustainable water purification.

Cu(II) complex heterogenized on magnetic mesoporous nanocomposite (SBA-16@Fe3O4) as an efficient catalyst for the reduction of nitro compounds

In the present study, a novel magnetic heterogeneous copper catalyst was developed by the immobilization of a Cu(II) complex on the surface of magnetic mesoporous nanocomposite (SBA-16@Fe3O4) through post-synthetic method. The synthesized catalyst was analyzed by various characterization methods including FT-IR, EDS, XRD, Nitrogen physisorption, TEM, TGA, VSM, and ICP-OES. After complete characterization, its catalytic efficiency was evaluated in the hydrogenation of nitroarenes to amines. Taking the nitrobenzene reduction of as an example of a reaction, the reaction conditions were optimized by changing diverse parameters like solvent, temperature, time, amount of catalyst, as well as the type and amount of hydrogen source. The catalyst revealed highly efficient catalytic activity in the hydrogenation of numerous nitroarenes to the corresponding aminoarenes in pure water as the solvent with sodium borohydride as a H2 source at room temperature. Additionally, the catalyst could be simply recovered from the mixture of reaction via magnetic separation and was able to mediate the reaction for multiple times with undiminished catalytic performance.

Selective hydrogenation of nitro compounds to amines by coupled redox reactions over a heterogeneous biocatalyst

Cleaner synthesis of amines remains a key challenge in organic chemistry because of their prevalence in pharmaceuticals, agrochemicals and synthetic building blocks. Here, we report a different paradigm for chemoselective hydrogenation of nitro compounds to amines, under mild, aqueous conditions. The hydrogenase enzyme releases electrons from H2 to a carbon black support which facilitates nitro-group reduction. For 30 nitroarenes we demonstrate full conversion (isolated yields 78 – 96%), with products including pharmaceuticals benzocaine, procainamide and mesalazine, and 4-aminophenol – precursor to paracetamol (acetaminophen). We also showcase gram-scale synthesis of procainamide with 90% isolated yield. We demonstrate potential for extension to aliphatic substrates. The catalyst is highly selective for reduction of the nitro group over other unsaturated bonds, tolerant to a wide range of functional groups, and exhibits excellent stability in reactions lasting up to 72 hours and full reusability over 5 cycles with a total turnover number over 1 million, indicating scope for direct translation to fine chemical manufacturing.

Synthesis and evaluation of palladium-functionalized biochar-supported magnetic nanoparticles for efficient nitro reduction

This study investigated the catalytic activity of the magnetic Fe3O4@Bio-R-Pd (Bio = biochar, R = epichlorohydrin and guanidine) for the reduction of nitro compounds. The structural and magnetic properties of the synthesized nanocatalyst were characterized using a suite of techniques including inductively coupled plasma spectrometry (ICP), vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier Transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). The recyclability of the synthesized nanocatalyst was confirmed by its complete reversibility upon testing with a vibrating magnetometer, further supporting its paramagnetic nature. Analysis of the SEM images revealed the presence of spherical magnetite particles within the composite. Using these optimized conditions, various aromatic nitro compounds were successfully reduced in the presence of the Fe3O4@Bio-R-Pd catalyst. The results demonstrate the advantageous properties of the synthesized nanocatalyst, including high product yield, stability and resistance at high temperatures, easy separation from the reaction medium, high efficiency with short reaction times, and economic viability. Notably, the synthesized sample exhibited nearly the same initial efficiency after 5 reuses, indicating almost complete recovery and minimal change in its catalytic activity.

Reconstructive Approach to the Regiospecific Synthesis of N9‐Alkylated Purines

AbstractA regiospecific synthesis of N9‐alkylated purines as novel acyclic nucleosides was developed. This approach is based on reconstructive methodology involving the construction of a target heterocyclic scaffold on a readily available 5‐aminotetrazole moiety, which is subsequently cleaved under reductive conditions due to azido‐tetrazole tautomerism. It appeared that the rate of reduction for the azide fragment in 6‐nitro‐7‐alkylaminotetrazolo[1,5‐a]pyrimidines is much greater than the rate of nitro group reduction. Treatment of these heterocycles with hydrogen over a palladium catalyst resulted in the formation of triaminopyrimidines in excellent yields through the reduction of both the azide and nitro group. Triaminopyrimidines were transformed into the desired N9‐alkylated purines, and an analog of the marketed drug penciclovir was synthesized by the developed method.

Highly active iron oxide@NC catalyst derived from the iron acetate/polyacrylonitrile threads: Driving nitroarene conversion to value‐added amines

AbstractChemoselective reduction of nitroarenes to corresponding arylamines is a significant reaction in the chemical industry. However, in the presence of other reducible groups, including halogenated nitrobenzene, nitrobiphenyl, and nitroquinoline in the same molecule of nitroaromatics, the control of chemoselectivity remains challenging. Here, a facile fabrication of a heterogeneous iron‐based catalyst is reported as a potential alternative to precious metal catalysts for the chemoselective reduction of nitroarenes. The pyrolysis of iron acetate/polyacrylonitrile (PAN) template under an inert atmosphere furnishes active Fe3O4 nanoparticles (NPs) encapsulated in nitrogen‐doped (N‐doped) carbon layers, which can provide more catalytic active sites (Fe3O4/PAN@800). Notably, non‐precious iron oxide NPs supported on N‐doped carbon support prevent aggregation, thereby enhancing the catalytic activity. The sustainable and reusable Fe3O4/PAN@800 catalyst, having only 0.8% metal content as demonstrated by x‐ray photoelectron spectroscopy, delivers excellent yields of corresponding amines from differently functionalized nitroarenes. Hydrogenation of a series of structurally functionalized nitroarenes produced excellent yields of anilines, which serve as building blocks and intermediates for fine and bulk chemicals. Hydrogenation of 2‐chloro‐3‐nitropyridine, 2‐nitro‐1,1′‐biphenyl, ortho‐nitroaniline, and 4‐aminophenyl acrylonitrile yielded respective anilines up to 99%. The active sites of Fe3O4 have magnetic performance, hence, the catalyst can be easily recovered using a magnet and reused for at least five cycles without significant loss of catalytic activity. Therefore, the easily prepared, cost‐effective, and reusable Fe3O4/PAN@800 catalyst presented in this study shows potential for applications in the selective reduction of aromatic nitro compounds. Consequently, this study potentially establishes a guideline for the facile preparation of abundant transition‐non‐noble metal‐based reusable supported catalysts for various applications in the chemical industry.

Stable Sub‐2‐nm Fe3O4 Particles Confined in P, N Co‐Doped Carbon Derived from the Assembly of DPPF with PCN‐222: A Promising Transfer Hydrogenation Catalyst

AbstractThe nanoconfinement approach for constructing ultra‐small nanoparticles has been effectively utilized in the development of non‐precious metal catalysts. Herein, the catalyst precursor was prepared by host‐guest assembly method, using PCN‐222 as the host and 1,1′‐bis(diphenylphosphino) ferrocene (DPPF) as the guest. After calcination, the sub‐2 nm iron oxide nanoparticles within a phosphorus‐nitrogen co‐doped carbon matrix (Fe3O4@P/N‐CDCM) was obtained. Benefiting from the nanoconfinement effect, the sub‐2 nm Fe3O4 nanoparticles were uniformly dispersed on the P/N‐CDCM matrix. As a representative application, Fe3O4@P/N‐CDCM‐600 showed remarkable catalytic activity in the reduction of various nitroaromatic compounds. Under ambient conditions, the efficient reduction of nitro compounds in aqueous solution led to excellent conversion rates (96–99 %) and selectivity (99 %) within 45 minutes. Additionally, the catalyst maintained high efficiency over 5 cycles without experiencing a noticeable decrease in activity. This work provides an innovative and cost‐effective strategy for fabricating highly dispersed non‐precious metal nanoparticles.

Cu-MOF-derived carbon nanomaterials as efficient catalysts for the reduction of nitro compounds

In this paper, we have synthesized a new light blue crystal Cu-MOF-1 with Cu(II) as the central metal ion by using two mixed ligands, where N,N’-bis(3-pyridyl)adipamide (3-bpaa) and fumaric acid (H2FA). Taking this material as the precursor of the study, it is found that Cu-MOF-1 possesses a single-crystal-to-single-crystal (SCSC) transition phenomenon, using its structure in the free state of water molecules in the heating process will be dehydrated and thus transformed into dark blue crystal Cu-MOF-2. This color distinctive change can be intuitively identify the temperature conversion, and thus be applied to the direction of the temperature sensing. Moreover, using Cu-MOF-1 as a precursor, the carbon-based nanostructured materials (Cu@X) of Cu and CuxO were derived from Cu-MOF-1 as a precursor in a straightforward and effective a single-step pyrolysis under different temperatures (400 °C, 600 °C, 800 °C and 1000 °C). As a result, Cu@1000 shown good activity (100 % conversion within 5 min) in the reduction of 4-nitrophenol (4-NP) by the presence of sodium borohydride (NaBH4) at mild circumstances, yielding a rate constant (Kapp) of 1.699 min−1. This remarkable performance is due to the utilization of both the uniform distribution of Cu-based nanoparticals (CuNPs) in the carbon matrix and the abundance of defect sites in the surface. This paper describes innovative MOF-derived catalysts that can be employed in a range of useful applications.

High turnover and selective Bin-Pd-NCs catalyst for nitro group non-hydrogen reductions in H2O under air conditions: A sustainable and recyclable route to aromatic amines

A green synthesis of anilines by the non-hydrogen reduction of nitro compounds is described. The reaction and post-treatment purification processes can produce high-purity target products without the use of organic solvents. The key to success lies in the synergistic action of two reaction mechanisms. The hydrogen transfer system is significantly accelerated by the presence of binaphthyl-palladium nanoclusters, which permits the catalyzed selective transfer hydrogenation under air conditions, providing a general preparation of aromatic amines in good-to-high yields with excellent chemoselectivities. Benefitting from the heterogeneous manner in water, successful recycling of the catalysts was further achieved with high reaction efficiency maintained. Meanwhile, the ICP analysis results show that the residual palladium content in the target product was below 5 ppm.

Synthetic and Mechanistic Studies into the Reductive Functionalization of Nitro Compounds Catalyzed by an Iron(salen) Complex.

We report on the use of a simple, bench-stable [Fe(salen)2]-μ-oxo precatalyst in the reduction of nitro compounds. The reaction proceeds at room temperature across a range of substrates, including nitro aromatics and aliphatics. By changing the reducing agent from pinacol borane (HBpin) to phenyl silane (H3SiPh), we can chemoselectively reduce nitro compounds while retaining carbonyl functionality. Our mechanistic studies, which include kinetics, electron paramagnetic resonance (EPR), mass spectrometry, and quantum chemistry, indicate the presence of a nitroso intermediate and the generation of an on-cycle iron hydride as a key catalytic intermediate. Based on this mechanistic insight, we were able to extend the chemistry to hydroamination and identified a simple substrate feature (alkene lowest unoccupied molecular orbital (LUMO) energy) that could be used to predict which alkenes would result in productive catalysis.

Rapid metal-free reduction of aromatic nitro compounds to aromatic amines in MeOH/H2O with B2pin2

The efficient reduction of nitro compounds to their corresponding amino compounds has been a challenging task. In this study, we developed a method for the rapid reduction of aromatic nitro compounds to aromatic amines. The method uses B2pin2 as the reducing agent and NaOH as the base, and the reaction can be completed in 15 min at 50 °C. A range of nitro compounds containing a variety of sensitive functional groups, such as halogen, thioether, cyano, vinyl, and heteroaryl were chemoselectively reduced to the corresponding anilines in good yields.

Mild and selective synthesis of imines and N-Heterocyclic compounds via formic acid-mediated reductive coupling strategy over Nitrogen-Coordinated cobalt Single-Atom catalysts

The selective formation of C = N bonds through the formic acid-mediated reductive coupling of nitro groups with carbonyl groups over heterogeneous catalysts poses challenges due to the corrosion of metal catalysts by formic acid and the rapid further hydrogenation of C = N into C-N bonds. In this study, we demonstrate that nitrogen-coordinated cobalt single-atom catalysts exhibit robust activity in this transformation. Various imines and N-heterocyclic compounds, including benzimidazoles, quinazolines, and pyrroles, can be synthesized at a modest temperature of only 70 °C. The high catalytic activity is attributed to the synergistic roles of nitrogen and cobalt atoms, serving as basic and active sites, respectively. Experimental data, complemented by density functional theory (DFT) calculations, clearly indicate that the transfer hydrogenation of nitrobenzene preferentially proceeds via the “direct” pathway rather than the “condensation” pathway. Moreover, the reduction of C = N bonds into C-N bonds demands much higher energy than the reduction of nitro groups, thereby enabling high selectivity towards C = N bonds. The findings of this study are expected to provide a novel approach for selective C = N bond formation and contribute to a deeper understanding of the mechanism underlying the reductive amination process.

Copper-Catalyzed Chemoselective Nitro Reduction

AbstractThe reduction of nitro compounds into the highly valuable anilines is reported using a Cu catalyst and B2Pin2. The reactions proceed under very mild conditions and showcase excellent functional group tolerance. This method is applied to a large panel of nitro derivatives, including biorelevant molecules and important synthetic intermediates, toward the synthesis of active pharmaceutical ingredients (APIs). This novel reaction manifold intends to provide a complementary approach to the existing portfolio of nitro-reduction methods.

Bisgermylene-Stabilized Stannylone: Catalytic Reduction of Nitrous Oxide and Nitro Compounds via Element-Ligand Cooperativity.

This study describes the synthesis, structural characterization, and catalytic application of a bis(germylene)-stabilized stannylone (2). The reduction of digermylated stannylene (1) with 2.2 equiv of potassium graphite (KC8) leads to the formation of stannylone 2 as a green solid in 78% yield. Computational studies showed that stannylone 2 possesses a formal Sn(0) center and a delocalized 3-c-2-e π-bond in the Ge2Sn core, which arises from back-donation of the p-type lone pair electrons on the Sn atom to the vacant orbitals of the Ge atoms. Stannylone 2 can serve as an efficient precatalyst for the selective reduction of nitrous oxide (N2O) and nitroarenes (ArNO2) with the formation of dinitrogen (N2) and hydrazines (ArNH-NHAr), respectively. Exposure of 2 with N2O (1 atm) resulted in the insertion of two oxygen atoms into the Ge-Ge and Ge-Sn bonds, yielding the germyl(oxyl)stannylene (3). Moreover, the stoichiometric reaction of 2 with 1-chloro-4-nitrobenzene afforded an amido(oxyl)stannylene (4) through the complete scission of the N-O bonds of the nitroarene. Stannylenes 3 and 4 serve as catalytically active species for the catalytic reduction of nitrous oxide and nitroarenes, respectively. Mechanistic studies reveal that the cooperation of the low-valent Ge and Sn centers allows for multiple electron transfers to cleave the N-O bonds of N2O and ArNO2. This approach presents a new strategy for catalyzing the deoxygenation of N2O and ArNO2 using a zerovalent tin compound.

Iodine-Catalyzed Cyclization of o-Nitrothiophenols with Cyclohexanones to Phenothiazines.

Here, a novel iodine-catalyzed direct cyclization of o-nitrothiophenols with cyclohexanones to phenothiazines has been described without external oxidants and hydrogen acceptors. The nitro of o-nitrothiophenol works as both a hydrogen acceptor and a coupling group, and water is the only byproduct. The reaction involves the reduction of nitro groups, C-H bond thioetherification, and C-H bond dehydroaromatization. This scheme offers broad synthetic value for further elaborations, as exemplified by a 3-step total synthesis of antipsychotic chlorpromazine.