Aromatic Amines Research Articles

In Situ Reversible and Robust Mechano-Responsive Ultralong Phosphorescence of Polyurethane Elastomer.

Though mechano-responsive luminescent materials obtained much attention, most of their responses are non-reversible, let alone in situ reversible. Here, the study presents a new strategy to push through this limitation for their applications, which relies on the reversible mechano-responsive (MR) hydrogen bonding interactions and polymer chain orientation among a doped polyurethane (PU) elastomer. The radiative and nonradiative transitions inside these phosphorescent triphenylene-based aromatic secondary amines (TpNP and TpNPO) doped in the PU matrix can be accordingly modulated by these MR variations, including the PU chains orientation and the interactions between emitters and PU, respectively. Surprisingly, the intensities, quantum yields, and even lifetimes of their ultralong phosphorescence correlate well with the stress of PU, showing triple mechano-enhancement with a small threshold value of 7.9MPa. Importantly, these in situ and rapidly reversible MR phosphorescences possess excellent repeatability, which is still displayed even after >500 cycles of loading/unloading. Based on such a robust and highly sensitive MR afterglow, these PU materials have been demonstrated applications with no interruption of background in several fields, including micro-crack detection, material damage prediction, limb movement monitoring, and information encryption. This work provides new insights for developing innovative ultralong phosphorescence materials with improved luminescence and reversible mechano-responsive behavior.

Michael addition-elimination reaction derived covalent organic polyrotaxane xerogels for ultra-high-efficiency capture of iodine pollutants

Herein, covalent organic polyrotaxane xerogels (COPRs), were developed as comprehensive and recyclable “three birds with one stone” platform effectively handling organic/radioactive iodine pollutants challenges. COPRs were synthesized rapidly from β-ketoenamine and aromatic amines β-cyclodextrin (β-CD) inclusion via Michael addition-elimination reaction in water at room temperature and pressure, avoiding the usage of any organic solvents. The formation of β-CD inclusion significantly increases the solubility and reactivity of monomers in water. The threading of β-CD endows multiple absorption sites within the porous skeleton, improving its iodine capture capacity. The integration of β-CD ring throughout the carbon skeleton not only provides a green and ultra-low-cost approach for preparing COPRs with brand-new structure, but also offers direct and effective methods realizing the carbon neutrality from the source of production. This work could be used as a general method for the specifically modifying COPs, providing opportunities to meet the growing needs of society.

Possibility of identifying 1H-indolylaminium trifluoroacetates with antimicrobial activity by mass spectrometry

The present study proposes a convenient approach to identify a series of novel substituted 1H-indol-5-,6-ylaminium trifluoroacetates with antimicrobial activity based on mass spectral data obtained using direct injection into an ion source at an elevated temperature when the salts decompose with the release of counterions: acids and organic bases – substituted 1H-indolylamines. By the presence of ions with m/z 69, 45, 28, 17 in the spectra, it is judged that the salts are formed by trifluoroacetic acid. Using the available literature data on the mass spectrometry of substituted indoles, aromatic amines, and carboxylic acids, substantiated schemes for the decomposition of molecular ions of organic bases, 1H-indolylamines, are compiled and discussed, in which the mechanism of formation and the structure of fragment ions arising under electron ionization conditions are given. The revealed general, as well as individual for individual representatives with a certain character and place of substitution in the indole bicycle, patterns of behavior of 1H-indolylamine radical ions under conditions of high-temperature mass spectral imaging make it possible to judge their structure and, in general, the structure of 1H-indolylamine trifluoroacetates. The approach used in this work can also be used to prove compounds of a similar group based on the analysis of their mass spectra.

Pd/PVP‐ Catalyzed Formylation of Amines and Nitroarenes to N‐Formamides with CO2 and Dimethylamine Borane: The Influence of CO2 on the Formation of Azoxyarenes

AbstractThe reactivity of dimethylamine borane (DMAB) towards amines and nitroarenes was investigated in the presence of the CO2 and Pd/PVP (PVP=polyvinylpyrrolidone) nanocatalyst. The formation of borane formate, Me2NH.BH2(OCHO), by the insertion of CO2 into the B−H bond was evidenced by NMR. The reaction of DMAB with CO2 also produced a second product, DMF, formed via self‐formylation. In the presence of aromatic or aliphatic amines corresponding N‐formamides were formed efficiently. Under the same conditions nitroarenes were hydrogenated to anilines or to azoxyarenes in the absence of CO2. In both reactions very high TOF values, up to 30 min−1, were obtained. Applying a higher excess of DMAB enabled the transformation of nitroarenes to N‐formamides. The Pd/PVP catalyst was used in 7 consecutive cycles of N‐methylaniline formylation with excellent selectivity and a total TON equal to 4700.

Direct Substitution of 2‐Aminotropones with Potassium Allyltrifluoroborates through Transition‐Metal‐Free C−N Bond Cleavage

AbstractThe poor nucleofugality of the amino group renders the C−N bond functionalization of primary aromatic amines highly challenging. Herein, we report a direct substitution reaction of 2‐aminotropones, bearing a unique non‐benzenoid seven‐membered aromatic ring that exists in some natural products and bioactive molecules, with potassium allyltrifluoroborates through C−N bond cleavage under transition‐metal‐free conditions. The amino group of 2‐aminotropones were directly substituted with potassium allyltrifluoroborates in the presence of sodium bicarbonate, delivering structurally diverse 2‐allyltropones in moderate to good yields. The reaction is free of directing groups, activating groups and transition metals, providing a convenient method to access substituted tropones.

Chiroptical Sensing of Amines With Isatins.

Isatins are extensively researched compounds with diverse applications, particularly as synthetic precursors in pharmaceutical developments. However, their use as optical probes for enantioselective sensing of chiral amines has not been explored to date. Herein, we present a novel chiroptical assay with an optimized isatin that generates strong, red-shifted circular dichroism (CD) signals at approximately 380 nm upon ketimine formation with chiral amines. The intensity of the induced CD signal increases linearly with the enantiomeric excess of the analyte and thus allows quantitative chirality analysis. The general usefulness of this approach is demonstrated with a broad range of aliphatic and aromatic chiral amines, and by accurate determination of the enantiomeric composition of 10 samples.

Plasma-activated water pretreatment as a promising technique to reduce the formation of heterocyclic aromatic amines and advanced glycation end products in roasted fish patties

This study investigated the efficacy of using plasma-activated water (PAW) as a novel and additive-free pretreatment in reducing the formation of free and bound heterocyclic aromatic amines (HAAs) and advanced glycation end products (AGEs) in roasted fish patties. PAW activated for different durations (50 s, 100 s, and 150 s), significantly decreased the levels of HAAs and AGEs. The highest inhibition rates were observed at 35.44% and 19.82% for free and bound HAAs, respectively, and 42.76% and 23.23% for free and bound AGEs, respectively. PAW pretreatment reduced the formation of HAAs and AGEs and mitigated their increase during storage. Analysis using electron paramagnetic resonance and UPLC-MS/MS showed a decrease in free radicals and reactive carbonyls (phenylglyoxal, glyoxal, and methylglyoxal), which can serve as intermediates for HAAs and AGEs. Correlation analysis indicated a significant positive correlation between HAAs/AGEs and phenylacetaldehyde, glyoxal, methylglyoxal, and the total spin number (P < 0.05). This suggests that PAW suppresses the production of reactive carbonyls by quenching free radicals, thereby inhibiting the formation of HAAs and AGEs. In conclusion, with its additive-free approach, PAW pretreatment holds promise for reducing HAAs and AGEs and improving the safety of roasted fish products.

A green deep eutectic solvent-based aqueous two-phase system for the extraction of heterocyclic aromatic amines from marinating juice

A green deep eutectic solvent-based aqueous two-phase system for the extraction of heterocyclic aromatic amines from marinating juice

Constructing Sulfur‐Heterocyclic Aromatic Amine Polymer with Multiple‐Redox Active Sites for Long‐Lifespan and All‐Organic Aqueous Magnesium Ion Batteries

AbstractOrganic polymer materials have attracted much attention in rechargeable aqueous magnesium ion batteries (AMIBs) due to their sustainability and structural designability. However, the ionic storage capability is hindered by their insufficient redox‐active sites, dissolvability in aqueous electrolytes, and short‐range conjugated structures, resulting in low energy density and poor cycling stability. Herein, a sulfur‐heterocyclic aromatic polyimide‐based organic polymer (PTDBS) is constructed with multiple redox‐active sites and long‐range conjugate, which is employed as active material for AMIB anode, achieving an outstanding Mg2+ storage capability. Benefitting from the introduced thioether bonds, PTDBS possesses an enhanced electronic conductivity and additional redox‐active sites for reversible Mg2+ coordination, thus ensuring high redox activity and superior electron affinity. As a result, the PTDBS electrode delivers ultrafast and stable Mg2+ storage in an MgCl2 aqueous electrolyte with a superior rate capacity of 98.6 mA h g−1 at 10.0 A g−1, and remarkable cycling stability over 7500 cycles with a capacity retention rate of 90.0%. Notably, the all‐organic aqueous full cell, realized by coupling the PTDBS anode and the polyindole cathode, achieves a high energy density and long lifespan. This work lays the foundation for the development of highly stable all‐organic electrode materials for large‐scale aqueous energy storage.

Effects of Ultrasound on Reactive Crystallization and Particle Properties of an Aromatic Amine in Batch and Continuous modes

Ultrasound has shown its benefits in the manufacturing processes of many pharmaceuticals and fine chemicals. This study focused on the reactive crystallization system of an aromatic amine and explored the potential uses of ultrasound in both batch and continuous modes. In batch experiments, we studied the effects of different sonication conditions including power, duration, and starting point on final particle properties. Under ultrasound, the crystal form and crystal morphology remained well maintained. The results of particle size and size distribution suggested that ultrasound reduced the mean sizes by improving the nucleation process and breaking up large particles. Additionally, the presence of ultrasound in continuous experiments was capable of inducing nucleation and the crystal products collected had a suitable distribution. Integrating ultrasound into the beginning of the continuous crystallization process can be an alternative to the seeding technique. The increasing sonication power did not reduce the induction time substantially. This indicated that a rational sonication condition should balance the overall process efficiency and energy consumption. The findings from batch and continuous experiments indicate that ultrasound could intensify industrial crystallization of the aromatic amine. Incorporating energy-efficient ultrasound with the continuous process will potentially lead to increased production efficiency and a well-controlled product quality.

Molecular-Level Pore Tuning in 2D Conductive Metal-Organic Frameworks for Advanced Supercapacitor Performance.

Two-dimensional (2D) electrically conductive metal-organic frameworks (MOFs) have emerged as viable candidates for active electrode materials in supercapacitors due to their high electrical conductivity, high specific surface area, and intrinsic redox-active sites. Despite their promising electrochemical performance, their pseudocapacitive behavior via fast and reversible charge transfer reactions remains yet to be fully exploited. Here, we investigate the electrochemical energy storage mechanism of Cu3(HHTATP)2 (HHTATP = 2,3,6,7,10,11-hexahydroxy-1,5,9-triaminotriphenylene), a 2D conductive MOF featuring characteristic redox-active pendant aromatic amines. Cu3(HHTATP)2 exhibited pseudocapacitive charge storage with an average gravimetric capacitance of 340 ± 15 F g-1 at a discharge rate of 0.2 A g-1 and maintained a capacitance retention over 90% after 7000 galvanostatic cycles at 5 A g-1. The polar pendant amines not only enhanced capacitance via additional amine/imine redox activity but also reduced interfacial charge transfer resistance through modified electrode-electrolyte interactions. These results highlight the potential of molecular-level pore environment tuning as a strategic approach in materials design for energy storage applications.

Cobalt(II) catalyzed Michael-type hydroamination of activated olefins

The aza-Michael addition reaction of primary and secondary amines to α,β-unsaturated olefins viz; acrylonitrile, phenyl vinyl sulfone and dimethyl maleate has been carried out using 5–10 mol% Co(NO3)2.6H2O as a catalyst in t-BuOMe at 80–100 °C, giving rise to the desired β-aminocarbonyl compounds or sulfones in moderate to good yields. A wide range of aromatic amines, even those bearing electron withdrawing groups could be added to activated olefins via this strategy. Addition of (hetero)aromatic amines were also feasible, while in case of 2-aminopyridine the reaction was found to be effective only when AgOTf was added along with the catalyst. The aliphatic amines; benzylamine, dibenzylamine, di-n-butylamine were also smoothly added to acrylonitrile and phenyl vinyl sulfone. The methodology describes cobalt(II) nitrate as an eco-friendly, cheap and shelf available catalyst suitable for performing the Michael-type hydroamination reactions.

Catalytic Fe2+ Cation Pair Site for Base-free N-Alkylation of Aromatic Amines with Alcohols.

The development of heterogeneous Fe catalysts is very attractive due to the ubiquitous, abundant, and inexpensive nature of Fe as a resource. However, Fe oxides are commonly inert as catalysts and hence, the design and fabrication of active Fe sites are essential. Herein, the fabrication of an active Fe cation pair site by simple reduction treatment of SiO2-supported FeOx (FeOx/SiO2) is presented. The active Fe cation pair site was formed by the removal of the oxygen atom between Fe cations of the FeOx on SiO2, namely oxygen vacancy formation, which is induced by temperature-controlled reduction treatment. 773 K reduction maximized the Fe cation pair sites without the decomposition of FeOx species, which was an effective catalytic one for the N-alkylation of amines mainly proceeded through Meerwein-Ponndorf-Verley (MPV) type reduction, which is achieved by the stabilization of six-membered ring transition state derived from imines and alcohols over the open active site of the Fe cation pair site.

NaIO4/NH2OH-mediated Efficient Synthesis of Phosphoroamidates from Anilines and Triethyl Phosphite

AbstractA simple, efficient, and metal-free method was developed for the synthesis of phosphoroamidates. In essence, a mixture of sodium periodate (NaIO4) and hydroxylamine (NH2OH⸱HCl) was used in stoichiometric amounts to execute the phosphoramidation reaction of aromatic amines and triethyl phosphites at room temperature, in open air. This method offers a practical synthesis route to afford a diverse range of phosphoroamidates via the construction of P − N bonds, with excellent functional group compatibility and good yields under mild conditions.

Magnetic Graphene Oxide Modified with MOF-199 for Efficient Extraction of Aromatic Amines from Water Samples for Their Determination with Gas Chromatography

A metal–organic framework (MOF-199) nanocomposite was coated on magnetic graphene oxide (MGO) as a sorbent (MGO/MOF-199) and used for the isolation of aromatic amines by magnetic solid-phase extraction (MSPE). The analytes subsequently determined using gas chromatography with a flame ionization detector (GC-FID). The sorbent mass, desorption solvent, extraction time, desorption time, and pH were optimized. The calibration plots demonstrate linear ranges from 0.1 to 500 ng mL−1 with correlation coefficients from 0.9908 to 0.9939. The limits of detection (LOD) were between 0.03 and 0.1 ng mL−1. To evaluate the repeatability, relative standard deviations (RSD) were evaluated for 0.1, 10, and 100 ng mL−1 of the aromatic amines, yielding values from 3.2% to 4.5%. The developed method was employed to extract aromatic amines from tap water, seawater, and spring water. The relative recoveries were from 97.2% to 99.9%.

Catalytic N-Alkylation of (Hetero)Aromatic Amines and Tandem Annulation Reactions.

A general and practical approach for N-alkylation of heteroaromatic amines with heteroaromatic alcohols is always challenging and rarely reported. Here, we designed and synthesized phosphine-free, robust, and efficient N,N-bidentate-Co(II) complexes for a universal N-alkylation of amines strategy. This present catalytic methodology can be applied to a wide range of substrates by varying alcohols, including aryl, aliphatic, acyclic, and cyclic groups, with heteroaromatic amines such as aminopyridine, 2-aminopyrimidine, and aminoquinoline to provide diverse monoalkylated organonitrogen compounds in good to excellent yields (108 examples). In addition, the utility of the developed catalytic protocol was also extended successfully for the dehydrogenative synthesis of biologically important quinoline derivatives (11 examples). Particularly, 8-aminoquinoline reacted differently with tandem N-alkylated-transfer hydrogenative byproduct (N-benzyl-1,2,3,4-tetrahydroquinolin-8-amine) was obtained, revealing the catalytic activity of the complex I. The reaction proceeded under environmentally benign conditions, which liberates water as the sole byproduct. Notably, a concise synthesis of acetylcholinesterase inhibitors (AChEIs) scaffolds as potential cognition enhancers illustrated the utility of the present protocol. Interestingly, various control and deuterium-labeled experiments were performed, suggesting that the reaction proceeds via the borrowing hydrogen pathway.

Reactions of Tetracyanoethylene with Aliphatic and Aromatic Amines and Hydrazines and Chemical Transformations of Tetracyanoethylene Derivatives

The significant synthetic potential and reactivity of tetracyanoethylene (TCNE) have captured the interest of numerous chemical communities. One of the most promising, readily achievable, yet least explored pathways for the reactivity of TCNE involves its interaction with arylamines. Typically, the reaction proceeds via tricyanovinylation (TCV); however, deviations from the standard chemical process have been observed in some instances. These include the formation of heterocyclic structures through tricyanovinyl intermediates, aliphatic dicarbonitriles through the cleavage of the C–C bond of a tetracyanoethyl substituent, complexation, and various pericyclic reactions. Therefore, the objective of this study is to review the diverse modes of interaction of TCNE with aromatic nitrogen-containing compounds and to focus the attention of the chemical community on the synthetic capabilities of this reagent, as well as the various biological and optical activities of the structures synthesized based on TCNE.

Enhanced photocatalytic degradation activity of titanium dioxide by adsorbing aromatic amines through N-bonding

Narrowing the wide band gap of TiO2 (∼3.2 eV) to enhance its visible light efficiency is crucial for advancing photocatalytic degradation of organic pollutants in industrial wastewater. In this study, we achieved band gap reduction and slowed recombination rates by adsorbing some aromatic amines, like aniline and its electron-donating derivatives, onto TiO2. The predominantly present N-bonded amine species reduced the band gap and decelerated charge carriers’ recombination, enhancing photocatalytic degradation under visible light. In contrast, the amine with electron-withdrawing group is adsorbed as only H-bonded species, which showed no improvement in photocatalytic activity, performing similarly to pristine TiO2. This surface modification strategy offers potential for creating visible light-driven photocatalysts for effective degradation of organic pollutants in water.

Reduction of Trinitrobenzene to Amines with Molecular Hydrogen over Chrysocolla-like Catalysts

The cheap non-noble Cu–SiO2-based nanocatalysts are under intensive study in different reactions resulting in useful chemicals, yet their application in environment protection is poorly studied. In the present work, the influence of the Cu loading (3–15 wt%) on the catalytic behavior of Cu/SiO2 materials was first precisely studied in the hydrogenation of hazardous trinitrobenzene to valuable aromatic amines with molecular hydrogen. The catalysts have been synthesized by the method of deposition–precipitation using urea. The catalyst characterization by XRD, TPR-H2, SEM, TEM, and N2 adsorption methods confirmed that they include nanoparticles of the micro-mesoporous chrysocolla-like phase supported in the mesopores of a commercial SiO2 carrier, as well as revealed formation of the highly dispersed CuO phase in the sample with the highest Cu loading. Variation in reaction conditions showed the optimal ones (170 °C, 1.3 MPa H2) resulting in complete trinitrobenzene conversion with a triaminobenzene yield of 65% for the catalyst with a 15% Cu loading, and the best yield of 82% was obtained over the catalyst with 10% Cu calcined at 600 °C. The results show the potential of Cu phyllosilicate-based catalysts for the utilization of trinitroaromatic compounds via catalytic hydrogenation to amines and their possible applications in a remediation treatment system.

Probabilistic Health Risk Assessment of Primary Aromatic Amines in Polyamide Cooking Utensils in China by Monte Carlo simulation

The migration of primary aromatic amines (PAAs) from food contact materials raises significant public health concerns. In this study, the migration levels of 26 PAAs were analyzed in 242 nylon cooking utensils using ultra-performance liquid chromatography-tandem mass spectrometry. A total of 18 PAAs were detected, of which 14 were quantified, with 4,4′-diaminodiphenylmethane (4,4′-MDA) and aniline being the most prevalent ones. The compliance rates for nylon kitchenware were similar under both legislation of European Commission (76.9%) and Chinese legislation (77.9%). Probabilistic non-carcinogenic and carcinogenic risk assessment were conducted using Monte Carlo simulation, with read-across approach applied to fill the gap of toxicity data. The hazard quotients for 18 PAAs were calculated, revealing that 17 PAAs (excluding 4,4′-MDA) had acceptable hazard quotients (<1). Lifetime cancer risks for 17 PAAs were determined, with 15 PAAs (excluding benzidine and 4,4′-MDA) showing acceptable cancer risks (<10−4). The study suggests that the non-carcinogenic and carcinogenic health risks posed by PAAs migrating from FCMs can be effectively mitigated by promptly identifying non-compliant products and reducing exposure to high-risk PAAs such as 4,4′-MDA and benzidine. Enhancing the understanding of PAA hazard characterization and implementing measures to minimize health risks associated with PAA migration from FCMs is hence recommended.