Addition Of Amines Research Articles

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.

Rewritable Surface‐Grafted Polymer Brushes with Dynamic Covalent Linkages

AbstractSurface grafting of polymer brushes drastically modifies surface properties, including wettability, compatibility, responsiveness, etc. A broad variety of functionalities can be introduced to the surface via different types of polymers. Bringing together properties of two or more types of polymer brushes to one surface opens up even more possibilities in brush‐modified materials. However, while it is generally feasible to introduce several chemical compositions along the brushes via copolymerization, it is challenging to vary the types of polymer brushes along a surface. Although previous studies have demonstrated binary brushes via orthogonal polymerization techniques or partial deactivation/regrafting, they commonly limit the number of polymer types to two. Here, we propose a strategy to introduce dynamic covalent diketoenamine linkages at the root of polymer brushes. The grafting density could be precisely tuned during surface functionalization. The surface‐anchored polymer brushes were cleaved by the addition of small molecule amines. New polymer brushes can be regrafted from the surface following refunctionalization of exposed sites. The maneuverability allows tuning of the types and densities of the polymer brushes, pointing the way to the preparation of a new generation of well‐defined brush‐modified materials with mixed grafts, with potential applications in the design of smart materials and surfaces.

Gold‐catalyzed Annulation between 1‐[2‐(Dimethoxymethyl)phenyl]prop‐2‐yn‐1‐yl Acetates and α‐Diazoesters or Anilines to Form Substituted Naphthoates and Indeno[1,2‐b]quinoline, Respectively.

This work describes gold‐catalyzed annulations of 1‐(2‐(dimethoxymethyl)phenyl)‐1‐prop‐2‐yn‐1‐yl acetate substrates with α‐diazo esters and anilines, respectively yielding substituted naphthoates and indeno[1,2‐b]quinoline derivatives. Our mechanistic analysis indicates 1‐methoxy‐2‐carbonyl‐1H‐indenes as their common intermediates. In the formation of naphthoates, α‐diazo ester attacks at gold‐bound intermediate via a SN2 pathway to enable a allylic methoxy substitution. For indeno[1,2‐b]quinoline derivatives, there are two main reactions, including (i) a reversible formation between intermediate and a double amine addition product and (ii) an arylation reaction of intermediate. Species N‐(phenyl((2E)‐1‐(phenylimino)‐1,3‐dihydro‐2H‐inden‐2‐ylidene)methyl)aniline was converted to indeno[1,2‐b]quinoline in the presence of gold catalyst.

Cascade Reactions of Alkynyl Ketones and Amides to Generate Unsaturated Oxacycles and Aromatic Carbocycles

We describe novel amine‐mediated transformation of alkynyl ketones and amides to generate 2‐methylene‐2H‐pyrans, substituted 3‐hydroxy‐9H‐fluoren‐9‐ones, and amine‐incorporated arenes. These cascade processes are initiated by conjugate addition of secondary amine followed by hydrolysis of the enamine/vinylogous amide intermediates. The product distribution is highly sensitive to the steric and electronic effects of the substituents on both the alkyne moieties, the tether structure connecting them, and the nature of the amine. Alkynyl amide participates in the Alder‐ene reaction favorably to generate more reactive allene amide that reacts with amine to generate amine‐incorporated arene products. These metal‐free cascade reactions are a useful synthetic method that can be exploited for the construction of various hetero‐ and carbocyclic systems.

Synthesis of Saxitoxin Biosynthetic Intermediates: Reveal the Mechanism for Formation of its Tricyclic Skeleton in Biosynthesis

The synthesis and biosynthesis of the complex saxitoxin (STX) structure have garnered significant interest. Previously, we hypothesized that the tricyclic skeleton of STX originates from the monocyclic precursor 11‐hydroxy‐IntC’2 during biosynthesis, although direct evidence has been lacking. In this study, we identified conditions to synthesize a proposed tricyclic biosynthetic intermediate, 12,12‐dideoxy‐decarbamoyloxySTX (dd‐doSTX), along with its 6‐epimer (6‐epi‐dd‐doSTX) and a bicyclic compound, in a single step from di‐Boc protected 11‐hydroxy‐IntC’2. The reaction mechanism involves successive aza‐Michael addition of a guanidino amine to the conjugated olefin. Notably, both dd‐doSTX and 6‐epi‐dd‐doSTX were detected in a toxin‐producing cyanobacterium, suggesting that the biosynthetic enzymes may generate these compounds via similar mechanisms.

Rare-Earth Dialkyls Supported by Silaimine-Cp Ligand: Synthesis, Reactivity, and Catalytic Addition of Alkynes and Amines to Carbodiimides

Rare-Earth Dialkyls Supported by Silaimine-Cp Ligand: Synthesis, Reactivity, and Catalytic Addition of Alkynes and Amines to Carbodiimides

Amine-impregnated cellulose aerogels prepared from old corrugated containers: Microstructure characterization and CO2 capture performance

Here, five different amines (MEA, DETA, TEPA, PEI, and PEPA) were immobilized onto a mesoporous cellulose aerogels (CAs) support prepared from old corrugated containers (OCCs) using the impregnation method, and the thermal stabilities, pore structures, and CO2 adsorption capacities of the resulting amine loaded materials were investigated. The results showed that the thermal stabilities and pore textures of the materials decreased relative to the unmodified CAs support. Additionally, the addition of high molecular weight amines improved the thermal stability of the resulting materials, in the order of PEI>PEPA>TEPA>DETA>MEA. The adsorption capacities of the five Amine40@CAs materials tested ranged from 111.76 to 62.48 mg.g−1 and were in the order of DETA>PEI>MEA>TEPA>PEPA. Considering both thermal stability and CO2 adsorption capacity, PEI is the most suitable for physical immobilization in the CAs support. Consequently, the sample loaded with 30 % PEI exhibits a maximum CO2 capture capacity of 136.84 mg.g−1 material. However, a loading above 30 % results in pore blockage due to amine infiltration into the pore structure, leading to a decrease in the specific surface area and hence the CO2 adsorption capacity. This indicates that there is a balance to be struck between amine loading and CO2 uptake in the solid amine adsorbents using the physical impregnation method, and it is necessary to choose an appropriate method for improving the pore structure in order to maximize the amine loading and thus enhance the CO2 capture capacity.

Sustainable and versatile Aza-Michael additions promoted by acidic ionic liquids

Acidic ionic liquids are a subset of ionic liquids where the cation or anion possess acidic properties with huge applications in various fields. Here we describe environmentally safe and highly efficient conjugate addition of aromatic and aliphatic amines to α, β-unsaturated compounds in the presence of novel acidic ionic liquids. The acidic ionic liquid catalyst was prepared by combining benzyl chloride with 2-(dimethylamino) ethanol and SnCl2 in a simpler manner. The resulting acidic ionic liquid was characterized using SEM, EDS and FTIR spectroscopy. In the presence of ionic liquids, a wide variety of amines undergo facile conjugate addition to α, β-unsaturated compounds affording the corresponding β-amino compounds in good to excellent yields (72–97 %), shorter reaction times (1–4 h) and mild reaction conditions (60 °C). Furthermore, the study demonstrated the sustainability of the process by showcasing that the acidic ionic liquids could be reclaimed and reused for up to five cycles without compromising their catalytic effectiveness.

Study of the possibility of using Cardura E10P thinner in epoxy compositions

Rheological, physical-mechanical and thermomechanical properties of binders based on ED-20 epoxy resin with Ethal-45M amine hardener and additives of Cardura E10P glycidyl ether from 5 to 50 wt.% as a diluent have been studied. As the Cardura E10P content increases, the dynamic viscosity of the binder decreases significantly and the gel time increases. The tensile strength of cured samples decreases from 49 MPa to 12 MPa with an increase in the Cardura E10P content from 5 to 30 weight parts, the deformability increases from 14 to 38%, and the glass transition temperature decreases from 67°C to 49°C.

Rewritable Surface-Grafted Polymer Brushes with Dynamic Covalent Linkages.

Surface grafting of polymer brushes drastically modifies surface properties, including wettability, compatibility, responsiveness, etc. A broad variety of functionalities can be introduced to the surface via different types of polymers. Bringing together properties of two or more types of polymer brushes to one surface opens up even more possibilities in brush-modified materials. However, while it is generally feasible to introduce several chemical compositions along the brushes via copolymerization, it is challenging to vary the types of polymer brushes along a surface. Although previous studies have demonstrated binary brushes via orthogonal polymerization techniques or partial deactivation/regrafting, they commonly limit the number of polymer types to two. Here, we propose a strategy to introduce dynamic covalent diketoenamine linkages at the root of polymer brushes. The grafting density could be precisely tuned during surface functionalization. The surface-anchored polymer brushes were cleaved by the addition of small molecule amines. New polymer brushes can be regrafted from the surface following refunctionalization of exposed sites. The maneuverability allows tuning of the types and densities of the polymer brushes, pointing the way to the preparation of a new generation of well-defined brush-modified materials with mixed grafts, with potential applications in the design of smart materials and surfaces.

Enhanced mechanical and interfacial performances of carbon fiber reinforced composites with low percentage of amine functionalized graphene

AbstractThis paper reports improvement in the tensile, flexural and interlaminar shear strength (ILSS) properties of ADG‐NH2/Epoxy/CFRP composites at low filler content. Five symmetrical CFRP composite laminates were prepared through wet layup process assisted by vacuum bagging technique with varying wt% proportions (0.25, 0.5, 0.75 and 1) of ADG‐NH2/Epoxy. Tensile tests, short beam shear test and flexural tests were carried out as per ASTM D3039, ASTM D2344 and ASTM 790‐10 respectively to assess the effect of the ADG‐NH2 functionalized nano additives on their mechanical properties. The variation in ILSS were studied for varying temperatures (room temperature, 35, 50, 75, 85, & 100°C for each type of ADG‐NH2/Epoxy wt% (neat, 0.25, 0.5, 0.75 & 1)) of ADG‐NH2/Epoxy/CFRP composites. The ILSS was enhanced up to ∼27% for 0.5 wt% of ADG‐NH2 reinforced CFRP at room temperature but reduced with the higher concentrations (0.75 wt% & 1 wt%). It was observed that ILSS reduced with gradual temperature variations up to 100°C w.r.t room temperature. But an increment was observed up to 0.5 wt% for ADG‐NH2 for all temperature. Form the test results, it has been recorded an improvement in mechanical properties that is, the elastic modulus by ∼18%, ultimate tensile strength by ∼21%, % elongation at break by∼19% and toughness by∼28% for the 0.5 wt% of ADG‐NH2 graphene nano additive reinforced CFRP composite laminates as compared to neat epoxy CFRP laminates. Results also show the augmentation in the Max load by ∼24%, flexural strength by ∼33%, flexural modulus by ∼43%, and flexural strain by ∼26% were observed for the 0.5 wt% of ADG‐NH2 graphene nano additive reinforced CFRP composite laminates as compared to neat epoxy CFRP composite laminates. Fractographic studies of fractured surface using SEM analyses shows better adhesion mechanisms which supports the augmentation in mechanical properties with addition of amine functionalized graphene to CFRP laminate.Highlights Reinforcement of amine functionalized (ADG‐NH2) graphene in the epoxy matrix and incorporation with carbon fibers to enhance the interfacial and flexural properties. Evaluation of temperature effects on interlaminar shear strength properties of amine functionalized CFRP composites Improvements in tensile, ILSS and flexural properties observed for a low percentage (0.5 wt%) of ADG‐NH2 graphene reinforced CFRP composite laminates. Use of aerospace grade epoxy and resin with amine functionalized graphene for further use in aerospace industry applications.

Synergy between Brønsted Acid Sites and Carbonaceous Deposits during Skeletal 1-Butene Isomerization over Ferrierite.

During skeletal 1-butene isomerization over ferrierite carbonaceous deposits block 98% of the micropores within 24 h, rendering them effectively inaccessible to reactants, while the catalytic activity improves continuously for 100 h on stream. Ex-situ pyridine adsorption shows that the concentration of conventional Brønsted acid sites in the 10-R channels decreases below the detection threshold of infrared spectroscopy within 2 h. However, the operando addition of the base triethyl amine to the feed quenches the reaction, showing that mediated acidity is necessary. The larger base 2,2,6,6-tetramethyl piperidine only deactivates catalytic activity after several hours because it cannot directly bind to active sites at the sterically restricted pore mouths. The communication of internal Brønsted acid sites to the external reactants via a concerted mechanism involving protonated monoaromatic deposits trapped in the pore mouths explains the promoting effects of coke species in zeolite-catalyzed skeletal butene isomerization. This work presents a consolidated explanation of the synergy of solid acidity, structural confinement, and carbonaceous deposits in zeolites.

A Cobalt(II) based coordination architecture for efficient colorimetric sensing of ammonia and amine vapors

This work presents the design, synthesis, and characterization of a new cobalt (II) based coordination architecture, {[Co(toua)(4,4′-bpy)].2H2O}n (1); where toua is 3,6,9-trioxaundecanaote and 4,4′-bpy is 4,4′-bipyridine tailored for efficient sensing of ammonia and amines. The formation and identity of 1 was confirmed by elemental analysis, spectroscopic study (FTIR and UV–visible spectroscopy), PXRD, XPS, FESEM, and BET analysis. The colorimetric sensing capability of 1 towards ammonia and various smaller-sized amines in the vapor phase through observable color changes is explored in this study. Their interaction with 1 is elucidated through FTIR, UV–Visible and Fluorescence spectroscopy, FESEM, and TCSPC analysis. The fluorescence sensing experiments demonstrate a remarkable quenching/enhancement effect with the addition of ammonia and various amines, showcasing the compound’s sensitivity and selectivity. The quenching/enhancement efficiency follows the order: NH3>Ethylenediamine (EDA)>1,3-diaminopropane (DAP)>n-propylethylenediamine (n-PEDA), following the molecular dimensions and steric hindrance surrounding nitrogen atoms. Hydrogen bonds and host-guest interactions, including (C–H)pyridinium⋅⋅⋅N interactions, are identified as the driving forces for the sensing process. Additionally, the paper reveals a rare occurrence of both “turn-off” and “turn-on” sensing behavior for the same compound, showcasing its versatility. The calculated RSD for the fluorometric sensor was found to be 1.03 % calculated from its triplicate readings at 240 nm. Limits of detection (LODs) and Limit of Quantification (LOQs) for NH3 (0.52 μM, and 1.74 μM) EDA (1.2 μM, and 4.2 μM), DAP (3.1 μM, and 10.5 μM), and n-PEDA (3.3 μM, and 11.2 μM) respectively) underscore the effective sensing capabilities of 1. The robustness of 1 upon exposure to amines was confirmed by PXRD. These findings justify that 1 is a promising vaporchromic probe for the fast and selective detection of ammonia and amines.

Novel naphthoquinones as potent aromatase inhibitors: Synthesis, anticancer, and in silico studies

A set of 26 naphthoquinone derivatives (3-28) were synthesized by nucleophilic substitution or Michael addition of various amines with 1,4-naphthoquinones and were investigated for their aromatase inhibitory and anticancer activities. The 1,4-naphthoquinone derivatives with amino substituents (14-16 and 24) and the N-alkylated products (25-28) showed promising aromatase inhibitory activity (IC50 = 0.006–2.6 µM). Interestingly, 2-((4-aminophenyl)amino)-3-chloronaphthalene-1,4-dione 14 was noted as a highly potent aromatase inhibitor (IC50 = 6 nM) possessing preferable selective anticancer effect against the breast cancer T47D cell line (IC50: cytotoxic T47D = 24.3 µM, non-cytotoxic to MRC-5 normal cell line, selective index > 6.9). Findings from molecular docking study also suggested that the hydrogen bond formation with Asp309 as well as the pi-sulfur interaction with Met374 residues may be essential for a striking inhibitory effect of the most potent compound 14. Moreover, the in silico drug-likeness prediction indicated that all active naphthoquinone-based compounds are drug-like molecules with potential to be further developed as dual-action anticancer agents for breast cancer management.

Microwave‐Assisted Catalyst‐Free Conjugate Addition of Amines to Maleimide

AbstractA catalyst‐free approach has been introduced for the conjugate addition of aromatic amine nucleophiles to α, β‐unsaturated N‐methyl maleimide under microwave irradiation by utilizing water as a promoter. Catalyst‐free, environmentally friendly, short‐reaction time, green solvent, and mild reaction conditions are the advantages of this protocol. This reaction provided good to excellent yields with aromatic anilines as nucleophiles. The benefits of this reaction align with the principles of green and sustainable synthetic chemistry, making it widely applicable in organic synthesis and pharmaceutical chemistry.

Origin of the Increase in the Selectivity of Ru Catalysts with the Addition of Amines in the Presence of ZnSO4 for the Selective Hydrogenation of Benzene to Cyclohexene

The synthesis of nylon 6 and nylon 66 can be performed, starting with the selective hydrogenation of benzene to cyclohexene, which is deemed to be environmentally friendly and cost-saving and to have higher atom efficiency. Nano-Ru catalyst was synthesized via a precipitation method. The prepared catalyst was evaluated in the selective hydrogenation of benzene toward cyclohexene generation in the presence of ZnSO4 in a liquid batch reactor. The promotion effect of the addition of amines, i.e., ethylenediamine, ethanolamine, diethanolamine, and triethanolamine, was investigated. The fresh and spent catalysts were thoroughly characterized by XRD, TEM, AES, N2-sorption, FT-IR, and TPR. It was found that the addition of amines could significantly improve the catalytic selectivity toward cyclohexene formation in the presence of ZnSO4. This was attributed to the formation of (Zn(OH)2)5(ZnSO4)(H2O)x (x = 0.5, 3 or 4) through the reaction between ZnSO4 and the amines, which could be chemisorbed on the Ru surface. This led to retarding the formation of cyclohexane from the complete hydrogenation of benzene and, thus, increased the catalytic selectivity toward cyclohexene synthesis. Therefore, with the presence of ZnSO4, the amount of chemisorbed (Zn(OH)2)5(ZnSO4)(H2O)x increased with increasing amounts of added amines, leading to a decline in the catalytic activity toward benzene conversion and selectivity toward cyclohexene generation. When 7.6 mmol of diethanolamine and 10 g of ZrO2 were applied, the highest cyclohexene yields of 61.6% and 77.0% of benzene conversion were achieved over the Ru catalyst. Promising stability was demonstrated after six runs of catalytic experiments without regeneration. These achievements are not only promising for industrial application but also beneficial for designing other catalytic systems for selective hydrogenation.

A novel fluorescence probe for ultrafast detection of SO2 derivatives/biogenic amines and its multi-application: Detecting food and fish freshness, fluorescent dye and bioimaging

In this study, we have effectively prepared a novel fluorescent probe named HDXM based on benzopyran derivatives for the ultrafast detection (within 3 s) of SO2 derivatives or biogenic amines. HDXM showed a noticeable color change after the addition of SO2 derivatives (from purple to colorless) or biogenic amines (from purple to blue), indicating that HDXM can identify two analytes with the naked eye. It is worth noting that HDXM can be used to detect SO2 derivatives in actual sugar samples, and to image HSO3−/SO32− in living cells. More importantly, sensing labels (HDXM-loaded filter paper or agarose hydrogel) enable real-time visual monitoring of salmon freshness through colorimetric and fluorescence dual channels. Compared with the Chinese national standard method, the sensing label is an effective tool for evaluating the freshness of fish. Benefiting from its excellent solubility and fluorescence performance, HDXM can be used as a versatile fluorescent material in various applications, including flexible films, glass coatings, impregnating dyes, printing, and fingerprint ink. HDXM is expected to be a promising and valuable multifunctional tool for food safety and fluorescent materials.

Understanding selectivity of nucleophilic addition to β-formyl-α-haloenoates: A synthetic and theoretical investigation

The reactions of β-formyl-α-haloenoates with nitrogen-centered nucleophiles are described. DFT calculations have been used to better understand what factors influence and determine the chemo- and regioselectivity of the nucleophilic addition of amines to such systems. The easy synthetic approaches to the functionally substituted enoate derivatives including tertiary dehydroamino acid esters and furan-2(5H)-ones provides highlight of this work.

Synthesis and Antitubercular Evaluation of Diverse Glycosylated Ureas from D-Glucose

N, N-disubstituted glycosylated ureas have been synthesized in good-to-excellent yields by 1,4-conjugate addition of amines to glycosylated olefinic esters followed by reaction of resulting glycosyl β-amino esters with diisocyanates. The developed sugar-based molecules were well characterized by extensive standard spectroscopic analysis including NMR (1H, 13C, and DEPT), IR, MS, and elemental analysis and were screened for their biological activity against Mycobacterium tuberculosis (M. Tb.), where some of them displayed potent antitubercular activity. The molecules have been designed keeping in view the well-known inhibitors of the enzymes involved in the biosynthesis of mycobacterial cell wall polymers and may be further explored as lead molecules for the successful development of a potential antitubercular drug candidate.Dedicated to Dr. Rama P. Tripathi, Former Chief Scientist at CSIR-Central Drug Research Institute, Lucknow, India, for his extraordinary contribution to “Drug development against Tuberculosis”

Direct Esterification of Alkylcarbamic Acids with Alcohols over CeO2 Catalyst.

Alkylcarbamic acids, which are easily produced via chemical absorption of CO2 into amines, have a great potential to be substrates for producing value-added chemicals. In this research, the esterification of various alkylcarbamic acids with alcohols into alkyl N-alkylcarbamates was demonstrated by using a heterogeneous catalyst as well as the corresponding amine additives. In the model reaction, the esterification of benzylcarbamic acid (BZA-CA) and methanol (MeOH), the target product of methyl N-benzylcarbamate was obtained in 64 % CO2 -based yield at 413 K in 12 h over a CeO2 catalyst, which also exhibited good reusability. In this catalytic system, the corresponding amine additive (i. e., benzylamine for BZA-CA) had the important role in the improvement of CO2 -moiety-based balance, allowing the precise kinetic study, in contrast to the cases without such additive. The detailed kinetic study on the target catalytic system and control systems suggested that BZA-CA underwent the esterification by MeOH directly. The current catalytic system using the combination of CeO2 catalyst and corresponding amine additive was also demonstrated to be applicable to the synthesis of alkyl N-alkylcarbamates from alkylcarbamic acids and alcohols with short, linear alkyl chains (≤C3 ).