Reduction Of Aromatic Nitro Groups Research Articles

Dual Electrode Detection in LC‐EC Analysis of Sanger‐tagged Amino Acids: Electrochemical Reduction of Aromatic Nitro Groups

AbstractAnalysis of amino acids is crucial to protein structure elucidation. Amino acids, amenable to separation by liquid chromatography (LC), can be detected by sensitive detectors used in liquid chromatograph including absorbance, fluorescence or electrochemical detector when derivatized. Derivatization of amino acids using suitable reagents enhances the separation and detection of amino acids using liquid chromatography. Sanger's reagent (1‐fluoro‐2,4‐dinitrobenzene, DNFB) makes amino acids suitable for absorbance detection. However, little has been done in terms of liquid chromatography with electrochemical detection (LC‐EC) of the DNFB derivatized amino acids. Furthermore, sensor development based on electrochemistry of nitroaromatics has increased dramatically for explosive detection. Since nitroaromatics are electrochemically active, it is essential to determine the reduction pathway. Cyclic voltammetry (CV), rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) experiments have been performed on nitrobenzene (NB) and N‐methyl‐2,4‐dinitroaniline (NMDNA). The results showed that the nitro group was reduced to hydroxylamine in aqueous solutions by addition of four electrons and four protons per nitro group and the hydroxylamine can be reversibly oxidized into a nitroso by removal of two electrons and two protons. Electrochemical detection of the nitro groups is appropriate for dual electrode detection of DNFB labeled amino acids in which reduction can occur on an upstream electrode and corresponding oxidation of the reduction product occurs on the downstream electrode.

Catalytic Static Mixer-Enabled Hydrogenation of a Key Fenebrutinib Intermediate: Real-Time Analysis for a Stable and Scalable Process

Catalytic static mixer (CSM) technology is presented as an industrially viable solution for aromatic nitro group reduction in the synthesis of fenebrutinib. Factors affecting catalyst inhibition could be rapidly understood and mitigated by the use of real-time analytics (FT-IR and UHPLC). This facilitated the development of stable and optimal conditions in a system with four CSMs positioned inside a thermostated shell-and-tube reactor. Additional care was taken to ensure the control of three key impurities to low levels (<0.10 area% by offline UHPLC analysis). The optimal conditions (0.4 M concentration, 20 bar, 120 °C, 3.3 equiv H2) were then scaled up to a reactor with eight CSMs, whereby an improvement in the space–time yield was achieved. Over 16 h of processing, a stable impurity profile was observed, without metal leaching. Finally, the reaction was performed in a system with 16 CSMs, which also provided an increase in the space–time yield (to 26.2 mol L–1 h–1 or 6.5 kg L–1 h–1), resulting in 174 g h–1 throughput, while maintaining an excellent impurity profile.

Metabolism of a sea lamprey pesticide by fish liver enzymes part A: identification and synthesis of TFM metabolites.

The sea lamprey (Petromyzon marinus) is a destructive invasive species in the Great Lakes that contributed to the collapse of native fish populations in the mid-1900s. 3-Trifluoromethyl-4-nitrophenol (TFM) is a selective pesticide that has been applied to sea lamprey infested tributaries of the Great Lakes to kill larvae since the 1960s and has reduced the populations by as much as 90%. However, the metabolism of TFM by sea lamprey and non-target species is not fully illuminated. Elucidation of TFM metabolism is critical for understanding its mode of action and possible environmental impact. Here, we describe the screening, identification, synthesis and structural characterization of TFM metabolites in livers from sea lamprey and three non-target species that differ in their ability to survive TFM exposure. We identified glucuronidation, sulfation, N-acetylation, glutathione conjugation, and aromatic nitro group reduction as potential detoxification mechanisms. Seven metabolites were synthesized for use as markers of TFM metabolism in fish. Quantitative 1H NMR was used to assay synthesized metabolite stock solutions that were then used as standard material to develop a quantitative LC-MS/MS method for TFM metabolites.

Synthesis of [13C6]3,4-diaminobenzoic acid as a precursor for stable isotope labeled benzimidazoles

The synthesis of [13C6]3,4-diaminobenzoic acid from commercially available [13C6]aniline is described in six steps. Salient features of this route include the preparation of a differentially protected 3,4-diaminobenzonitrile, hydrogen gas free aromatic nitro group reduction with ammonium formate and facile benzimidazole ring closure of the ortho-arylenediamine with triethylorthoformate. This stable-labeled 3,4-diaminobenzoic acid is an ideal [M+6]isotopomer to synthesize complex benzimidazole fragments for mass spectrometry internal assays.

Facile one-pot strategy to prepare Ag/Fe2O3 decorated reduced graphene oxide nanocomposite and its catalytic application in chemoselective reduction of nitroarenes

The present work reports about one-pot hydrothermal synthesis of a composite of Ag/Fe2O3 anchored on reduced graphene oxide (rGO) via homogeneous chemical precipitation of Fe(OH)3 and simultaneous reduction of Ag(I). The pristine aqueous suspension of graphene oxide (GO) synthesized by Hummers method is mixed with Fe(NO3)3·9H2O, AgNO3, urea and polyethylene glycol (PEG 4000). The mixture under hydrothermal conditions transforms into Ag/α-Fe2O3-rGO nanohybrid. Here PEG 4000plays dual role of surfactant as well as reducing agent for Ag(I). The synthesized Ag/Fe2O3-rGO nanocomposite was used as magnetically recoverable catalyst for room-temperature chemoselective reduction of aromatic nitro groups to the corresponding amines.

Synthesis of 10-Ethyl Flavin: A Multistep Synthesis Organic Chemistry Laboratory Experiment for Upper-Division Undergraduate Students

A multistep synthesis of 10-ethyl flavin was developed as an organic chemistry laboratory experiment for upper-division undergraduate students. Students synthesize 10-ethyl flavin as a bright yellow solid via a five-step sequence. The experiment introduces students to various hands-on experimental organic synthetic techniques, such as column chromatography, thin layer chromatography (TLC), extraction techniques, and characterizing intermediates and final products by IR and NMR spectroscopy. It also provides an opportunity for students to review important topics such as nucleophilic substitution reactions, hydrolysis of amides, condensation reactions, and reduction of aromatic nitro groups to amines.

In situ production of silver nanoparticles on an aldehyde-equipped conjugated porous polymer and subsequent heterogeneous reduction of aromatic nitro groups at room temperature.

In a metal-free procedure, chelating thiol groups and an electrophile react to assemble a robust, conjugated porous polymer with pendant aldehyde functionalities. These groups are able to reduce Ag(i) ions to generate, in situ, Ag(0) nanoparticles evenly dispersed in the polymer matrix. The Ag(0)-polymer composite enables selective reduction of aromatic nitro compounds as a heterogeneous catalyst, and can be conveniently recycled multiple times.

Magnetically separable core–shell iron oxide@nickel nanoparticles as high-performance recyclable catalysts for chemoselective reduction of nitroaromatics

A magnetically separable core–shell iron oxide@nickel nanocatalyst was synthesized, characterized and applied for the aromatic nitro group reduction.

Utilization of ReactIR in Fit for Purpose Process Enablement

An efficient four-step synthesis of 1 is described in which utilization of ReactIR was key to efficient processing and reaction monitoring. Key chemical steps included (i) nucleophilic aromatic substitution, iron reduction of aromatic nitro group to aniline, (ii) decarboxylation, and (iii) ester formation.

In situ Raman spectroscopic studies on potential-induced structural changes in polyaniline thin films synthesized via surface-initiated electropolymerization on covalently modified gold surface

The work describes the in situ Raman spectroelectrochemical studies on polyaniline (PANi) thin films covalently bound to the modified gold surface. The PANi thin films were synthesized via surface-initiated electrochemical polymerization on gold substrates initially modified by the formation of self-assembled monolayer of 4-aminothiophenol, or comparatively by the electrografting of 4-nitrobenzenediazonium salt followed by the electrochemical reduction of aromatic nitro-groups to form aniline-containing monolayer. Due to the defined surface-chain bonding and the ordered polymer structure, the obtained thin PANi films exhibit a narrow peak separation of the polymer redox transitions and negatively shifted potential of its full oxidation, as revealed by the PANi Raman spectra recorded at controlled potentials and cyclic voltammetry measurements.

Formation of a gold–carbon dot nanocomposite with superior catalytic ability for the reduction of aromatic nitro groups in water

Probing on the synthesis of gold-carbon dot nanocomposite for catalytic reduction of aromatic nitrogroup.

Fast and effective reduction of nitroarenes by sodium dithionite under PTC conditions: application in solid-phase synthesis

Herein, conditions for the fast and effective reduction of aromatic nitro groups bound to hydrophobic polystyrene-based Wang and Ring resins utilizing sodium dithionite in dichloromethane–water under PTC conditions are reported. Tetrabutylammonium hydrogen sulfate (TBAHS) was found to be an effective phase-transfer catalyst for this reaction. This method allows for the reduction of nitro groups to amino groups under mild conditions with complete conversion and is tolerant of other functional groups. This method is a superior alternative to tin(II) chloride-based reduction, which is known for its shortcomings.

ChemInform Abstract: Formation of 4‐N‐Arylamino‐1‐butanol Derivatives from Aromatic Nitro Compounds via a Novel Palladium‐Catalyzed Tetrahydrofuran Ring‐Opening Reaction.

Abstract 4-N-Arylamino-1-butanol derivatives are produced via a palladium-catalyzed tetrahydrofuran ring-opening reaction. This reaction occurs during the reduction of aromatic nitro groups with polymethylhydrosiloxane (PMHS) and potassium fluoride in the presence of hydrogen peroxide. This represents a novel route for the synthesis of 4-N-arylamino-1-butanols.

Formation of 4-N-Arylamino-1-butanol Derivatives from Aromatic Nitro Compounds via a Novel Palladium-Catalyzed Tetrahydrofuran Ring-Opening Reaction

4-N-Arylamino-1-butanol derivatives are produced via a palladium-catalyzed tetrahydrofuran ring-opening reaction. This reaction occurs during the reduction of aromatic nitro groups with polymethylhydrosiloxane (PMHS) and potassium fluoride in the presence of hydrogen peroxide. This represents a novel route for the synthesis of 4-N-arylamino-1-butanols.

Reduction of aromatic nitro compounds to amines using zinc and aqueous chelating ethers: Mild and efficient method for zinc activation

AbstractA mild, environmentally friendly method for reduction of aromatic nitro group to amine is reported, using zinc powder in aqueous solutions of chelating ethers. The donor ether acts as a ligand and also serves as a co-solvent. Water is the proton source. This procedure is also a new method for the activation of zinc for electron transfer reduction of aromatic nitro compounds. The reduction is accomplished in a neutral medium and other reducing groups remained unaffected. The ethers used are dioxolane, 1,4-dioxane, ethoxymethoxyethane, dimethoxymethane, 1,2-dimethoxyethane, and diglyme.

One-step double reduction of aryl nitro and carbonyl groups using hydrazine

Single-step reduction of aryl nitro and carbonyl groups to the corresponding synthetically useful alkyl-anilines occurs with excellent yields by treatment with hydrazine and a base in a solvent-free reaction. The method has been applied to a broad range of compounds with different properties. Investigations into the mechanism of the reduction reveal that each group is reduced independently. A mechanism is proposed for this novel reduction of aromatic nitro groups.

Selective Reduction of Aromatic Nitro Groups in the Presence of Amide Functionality.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Selective Reduction of Aromatic Nitro Groups in the Presence of Amide Functionality

Pressure mediated selective reduction of aromatic nitro groups in the presence of amide functionality has been achieved by use of hydrazine hydrate.

Pd-Catalyzed Silicon Hydride Reductions of Aromatic and Aliphatic Nitro Groups

[reaction: see text] Room-temperature reduction of aromatic nitro groups to amines can be accomplished in high yield, with wide functional group tolerance and short reaction times (30 min) using a combination of palladium(II) acetate, aqueous potassium fluoride, and polymethylhydrosiloxane (PMHS). Replacing PMHS/KF with triethylsilane allows aliphatic nitro groups to be reduced to their hydroxylamines.

From Knowledge Generation to Knowledge Archive. A General Strategy Using TOPS‐MODE with DEREK to Formulate New Alerts for Skin Sensitization.

A general strategy for knowledge flow concerning skin sensitization based on the combined use of TOPS-MODE and DEREK expert system is proposed. TOPS-MODE is used as a knowledge generator, while DEREK represents the knowledge archive. A TOPS-MODE classification model allows the identification of structural fragments and groups responsible for strong/moderate skin sensitization. These structural contributions are sorted, analyzed, and graphically displayed in an appropriate way allowing the identification of several structural alerts for skin sensitization. Nine structural alerts already implemented in DEREK are identified using this strategy. They comprise, among others, alkyl halides, aldehydes, alpha,beta-unsaturated compounds, aromatic amines, phenols, hydroquinone, isothiazolinone, and alkyl sulfonates. Four new hypotheses are generated using TOPS-MODE structural contributions to skin sensitization, which are not recognized as structural alerts by DEREK. They include the reduction of aromatic nitro groups and epoxidation reaction of double bonds as metabolic activation steps that can lead to reactive haptens which can trigger the skin sensitization mechanism. Another new alert is based on 1,2,5-thiadiazole-1,1-dioxide for which we have identified a possible mechanism explaining its strong skin sensitization profile. It is based on the existence of a tautomeric equilibrium and further reaction with nucleophiles, which are both supported by experimental evidence. Finally, we have identified a possible new mechanism for the skin sensitization of nonreactive compounds, which involves the formation of noncovalent complexes with proteins in a processing- and metabolism-independent way.