Search Results (125)

To mitigate the issue of brittleness and cracking in epoxy resin (EP) anti-skid systems, this study investigates four key aspects tailored to application scenarios: toughening, low shrinkage, strong adhesion, and rapid curing at ambient temperature. 1,4-Butanediol diglycidyl ether (BDDE) was used to extend the chain of triethylenetetramine (TETA), followed by a Mannich reaction with formaldehyde (F) and cardanol to prepare a flexible aliphatic amine Mannich base curing agent containing flexible segments (Curing Agent B). The influence of composition ratios on the mechanical properties of the cured product was studied. The curing performance of the epoxy system under various temperature conditions and its adhesion to asphalt substrates were characterized. The thermal shrinkage behavior of the epoxy system under temperature-variable environments was also investigated. The results indicated that the elongation at break of the epoxy curing system, after chain extension and toughening, increased from 28.7% to 40.4%, representing a 28.9% increase. When n (Cardanol):n (TETA):n (F):n (BDDE) = 1:1.4:0.8:0.7 (molar ratio of reactants), m (EP):m (Curing Agent B) = 1:1 (mass ratio), and epoxy-terminated polyurethane (EPU) prepolymer constituted 10% of the epoxy resin mass; the epoxy curing system exhibited an elongation at break of 44.3%, a tensile strength of 7.0 MPa, a bond strength of 6.9 MPa, and an impact toughness of 1.77 J/cm². Furthermore, it exhibited rapid curing at a low temperature (0~5 °C) and at room temperature (25 °C). Additionally, when bisphenol F epoxy resin was used, the system demonstrated optimal thermal expansion properties. Full article

This study investigates the protective performance of a triazole-based Mannich base corrosion inhibitor, 4-((1,2,4-triazolyl)methyl) dibutylamine (TZMBA), on P110 carbon steel in dissolved oxygen environments. TZMBA was synthesized via a Mannich reaction, and its molecular structure was confirmed by Fourier transform infrared spectroscopy (FT-IR). The corrosion inhibition behavior and underlying mechanisms were systematically explored through weight loss measurements, surface characterization, and multiscale molecular simulations. Weight loss results indicated that TZMBA significantly mitigates the corrosion of P110 steel, with inhibition efficiency reaching 81.5% at 1.67 mmol/L and 82.0% at 2.14 mmol/L. Adsorption thermodynamic analysis revealed that the process follows the Langmuir isotherm model. The calculated standard Gibbs free energy ${∆G}_{ads}^0$ of −38.69 kJ/mol suggests a spontaneous, mixed-type adsorption mechanism involving both physisorption and chemisorption. Scanning electron microscopy (SEM) observations confirmed a marked reduction in surface degradation, characterized by suppressed corrosion products and minimized localized attack. X-ray photoelectron spectroscopy (XPS) further verified that TZMBA anchors to the metal surface through chemical coordination, forming a robust organic-inorganic composite film. From a theoretical perspective, frontier molecular orbital (FMO) analysis showed that TZMBA’s high E_HOMO and narrow energy gap facilitate efficient electron transfer. Combined Fukui function and molecular electrostatic potential (MEP) maps identified the nitrogen atoms in the triazole ring and amine group as the primary active sites. Furthermore, molecular dynamics (MD) simulations demonstrated that TZMBA molecules adopt a nearly parallel configuration on the Fe surface. The high negative interaction energy obtained from MD simulations confirms a strong binding affinity and a potent inherent driving force for the formation of a stable protective layer. Overall, the integration of experimental data and theoretical calculations establishes TZMBA as an effective inhibitor that provides superior protection by forming a stable, compact adsorption film on P110 carbon steel. Full article

A systematic evaluation of meta-substitution and backbone molecular weight in diamine-based benzoxazines was conducted to investigate the impact on melt processability, network development, and the structure–property relationships in polybenzoxazines. Six benzoxazine monomers derived from aryl ether diamines were synthesized, with controlled levels of meta-substitution and varying numbers of ether-bridged phenyl rings in the monomer backbone. Meta-substitution was found to suppress crystallinity in high-purity benzoxazine monomers and lower onsets of polymerization were observed due to meta-positioning of the terminal diamine rings. Terminal diamine meta-substitution also led to higher polymerization enthalpies, attributed to the emergence of an additional polymerization mechanism that increased the glass transition temperature up to 60 °C and delayed the onset of mass loss degradation. Benzoxazines with glass transition temperatures approaching 200 °C are susceptible to Mannich bridge degradation during polymerization, and this additional polymerization pathway both illustrates the nuanced complexities of benzoxazine structure–property relationships as well as provides a potential design strategy for benzoxazines with high glass transition temperatures approaching 250 °C. Full article

Background: 8-Hydroxyquinoline and phthalimide are two significant heterocyclic scaffolds in medicinal chemistry due to their pharmacological profiles. Hybridizing these pharmacophores and further modifying them via modified Mannich reactions provides a strategy to improve their physicochemical parameters and selectivity toward multidrug-resistant (MDR) cancer cells. Objectives: To synthesize a series of 8-hydroxyquinoline–phthalimide hybrids and their Mannich base derivatives and evaluate their cytotoxic activity and resistance-selective properties against sensitive Colo205 and resistant Colo320 cancer cell lines. Methods: Four hybrid compounds were synthesized by reacting 5-amino-8-hydroxyquinoline with different phthalic anhydride derivatives. Twelve fine-tuned derivatives were prepared by using the modified Mannich reaction. Cytotoxic activity was measured using the MTT assay, and relative resistance (RR) was calculated to determine selectivity toward the resistant cell line. P-glycoprotein (Pgp) ATPase activity was evaluated for the most active compounds. Results: All derivatives displayed cytotoxic activity, with higher potency toward the resistant Colo320 cell line. Compounds 2 and 4 showed the strongest activity against both cell lines (IC₅₀ down to 4.88 µM). Compounds 5, 8a, 9a, and 9c retained potent activity against Colo320 (IC₅₀ = 9.89–22.79 µM). Incorporating a CH₂–N group at position C7 substantially enhanced the selectivity for MDR cells. Compounds 9c, 9a, and 8a exhibited the highest selectivity, with RR values of 0.29, 0.33, and 0.35, respectively. Compounds 2, 4, 5, 8a, and 9a showed inhibitory effects on Pgp ATPase activity. Conclusions: The newly synthesized HQ–phthalimide hybrids represent promising candidates for targeting MDR in colorectal cancer, with Mannich modification enhancing the selectivity toward resistant cells. Full article

Corrosion in complex acid environments, such as high temperatures and acidic downhole conditions, remains a critical threat to well integrity during oil and gas acidizing. This review firstly examines the influence of downhole variables, including temperature, acidity, and steel, on the performance of organic inhibitors. It analyzes molecular design strategies that enhance the stability and adsorption of traditional inhibitor classes, including Mannich Bases, quaternary ammonium salts, and benzimidazoles, through structural modifications such as rigid heterocycles, extended alkyl chains, and multi-dentate architectures. The discussion extends to synergistic formulations, sustainable alternatives derived from biopolymers or green chemistry, and intelligent responsive systems. Furthermore, the growing role of computational methods, from molecular dynamics simulations to AI-driven molecular design, in accelerating the discovery of high-performance inhibitors is highlighted. Together, these advances offer a comprehensive and forward-looking perspective on developing adaptive, efficient, and environmentally compatible corrosion protection strategies for next-generation hydrocarbon extraction. Full article

The reaction of a 2-naphthol-derived Mannich base with the push-pull 5-morpholinopenta-2,4-dienal under acidic conditions unexpectedly afforded (7aR*,7bR*)-7a,7b-dihydro-15H-dibenzo[f,f′]cyclopenta[1,2-b:5,4-b′]dichromene. The structure of this product was unambiguously confirmed by NMR spectroscopy and X-ray diffraction analysis. A plausible mechanism involves the in situ generation of 1,2-naphthoquinone-1-methide, followed by a [4 + 2] cycloaddition and a subsequent interrupted iso-Nazarov cyclization. In this process, the enol tautomer of the resulting fused cyclopentenone is trapped by a second equivalent of the 1,2-naphthoquinone-1-methide, leading to the observed polycyclic framework. Full article

Nineteen previously and newly synthesized amphoteric 8-[(dialkylamino)methyl]-7-hydroxy-4-(2-oxo-2H-chromen-3-yl)-2H-chromen-2-ones were assayed as inhibitors of monoamine oxidases (MAO-A and B) and cholinesterases (AChE and BChE). Five of the tested compounds (2b, 2c, 3c, 5b, and 5c), namely those bearing the less bulky alkyls in the Mannich base 8-CH₂NR₂ (R = Me, Et) and the halogens (Cl, Br) at C6 of the 4-coumarin-3-yl moiety, showed moderate inhibitory potencies toward human MAO-A in the single-digit micromolar range (IC₅₀s from 1.49 to 3.04 µM). In particular, the 6′-Cl derivatives 2b and 5b proved to be reversible competitive inhibitors of human MAO-A with K_i values of 0.272 and 0.326 µM. Among the tested compounds, 3c proved to also be a moderate inhibitor of human AChE (IC₅₀ 4.27 µM). Molecular docking calculations suggested binding modes of the most active compounds to MAO-A and AChE binding sites consistent enough with the experimental data. Chemoinformatic tools suggest for the most active compounds, including the dual MAO-A/AChE inhibitor 3c, full compliance with Lipinski’s rule of five, high probability of gastrointestinal absorption, but low blood–brain barrier (BBB) permeability. While further efforts are required to improve their CNS distribution, herein new phenolic Mannich bases have been identified that may have potential for treating neurodegenerative syndromes. Full article

4,4′-substituted-2,2′-((hexahydro-1H-benzo[d]imidazole-1,3(2H)-diyl)bis(methylene))bisphenols (1a–d) and 2,6-bis{[3-(2-hydroxy-5-substitutedbenzyl)octahydro-1H-benzimidazol-1-yl]methyl}-4-substitutedphenols (2a–b) were synthesized via microwave (MW) irradiation of aminal (2R,7R,11S,16S)-1,8,10,17-tetraazapentacyclo[8.8.1.1.^8,170.^2,70.^11,16]icosane 2 with p-substituted phenols. Microwave (MW) irradiation improved reaction rates and yields at 80 °C. Compounds 1a–d were racemic, and 2a–b were diastereomeric. NMR spectra revealed key signals for the perhydrobenzimidazole fragment, aromatic rings, and aminal carbons. Differences in the ¹³C NMR spectra highlighted structural variations, such as distinct carbonyl and methoxyl signals in 2d. MW irradiation at higher temperatures (100–120 °C) reduced yields of 1, especially for phenols with methyl (Me) and methoxy (OMe) groups, suggesting a shift toward the formation of compound 2. Additionally, higher temperatures led to polymerization byproducts, emphasizing the impact of MW energy on reaction pathways. These results provide valuable insights for designing molecules with potential applications in materials science and medicinal chemistry. Full article

Benzoxazine resins are gaining attention for their impressive thermal stability, low water uptake, and strong mechanical properties. In this work, two new bio-based benzoxazine monomers were developed using renewable arbutin: one combined with 3-(2-aminoethylamino) propyltrimethoxysilane (AB), and the other with furfurylamine (AF). Both were synthesized using a simple Mannich-type reaction and verified through FT-IR and ¹H-NMR spectroscopy. By blending these monomers in different ratios, copolymers with adjustable thermal, dielectric, and surface characteristics were produced. Thermal analysis showed that the materials had broad processing windows and cured effectively, while thermogravimetric testing confirmed excellent heat resistance—especially in AF-rich blends, which left behind more char. The structural changes obtained during curing process were monitored using FT-IR, and XPS verified the presence of key elements like carbon, oxygen, nitrogen, and silicon. SEM imaging revealed that AB-based materials had smoother surfaces, while AF-based ones were rougher; the copolymers fell in between. Dielectric testing showed that increasing AF content raised both permittivity and loss, and contact angle measurements confirmed that surfaces ranged from water-repellent (AB) to water-attracting (AF). Overall, these biopolymers (AB/AF copolymers) synthesized from arbutin combine environmental sustainability with customizability, making them strong candidates for use in electronics, protective coatings, and flame-resistant composite materials. Full article

The efficient employment of chiral porous organic cages (POCs) for asymmetric catalysis is of great significance. In this work, we have synthesized a chiral N-rich organic cage constructed through chiral (S, S)-1,2-cyclohexanediamine and benzene-1,3,5-tricarbaldehyde utilizing dynamic imine chemistry according to the literature. Following reduction with NaBH₄, the resulting amine-based POCs (RCC3) feature appended chiral diamine moieties capable of coordinating Cu²⁺ cations. This Cu²⁺ coordination provides RCC3 with excellent enantioselectivity as a supramolecular nanoreactor in asymmetric decarboxylative Mannich reactions, providing up to 94% ee of the product. We found that the spatial distribution of chiral amine sites and the coordination of Cu²⁺ in the RCC3 have a significant impact on catalytic activity, especially enantioselectivity. This work provides insights into the structure–function relationship within supramolecular catalytic systems Full article

A series of novel N-Mannich bases derived from a dimethylpyridine–1,2,4-triazole hybrid was synthesized and evaluated in vitro for cytotoxic activity on several human gastrointestinal cancer cells (EPG, Caco-2, LoVo, LoVo/Dx, and HT-29). Compound 6 bearing a phenyl group at the N-4 position and a 4-methylphenyl piperazine moiety at the N-2 position of the 1,2,4-triazole-3-thione scaffold exerted good cytotoxic activities on EPG and Caco-2 cell lines, along with pronounced selectivity, showing lower cytotoxicity against normal colonic epithelial cells (CCD 841 CoTr). Further evaluation revealed the good ability of compound 6 to inhibit the efflux function of P-glycoprotein in P-gp-expressing cell lines (HT-29, LoVo, and LoVo/Dx). Moreover, compound 6 induced apoptotic cell death through a significant increase in the caspase-3 and p53 protein levels in HT-29 cells. Finally, the molecular docking method was applied to explain our experimental findings. The molecular modeling study based on Density Functional Theory (DFT) and the Quantum Theory of Atoms in Molecules (QTAIM) analysis provided insight into the geometric and electronic structure properties of the compounds. Full article

Kynurenic acid (KYNA) derivatives condensed with an aromatic ring (tricyclic KYNA derivatives) have been successfully synthesized, and the reactivity of these analogues has been investigated in the modified Mannich reaction resulting in new Mannich bases. The N,N-dimethyl-ethylenediamine analogues of the tricyclic KYNA derivatives have also been successfully synthesized, and their reactivity in the modified Mannich reaction was investigated. The synthesized ring systems bear resemblance to molecules previously investigated as G-quadruplex binding agents. Based on this similarity, the synthesized tricyclic KYNA derivatives could be investigated as potential antiviral and anticancer molecules. Full article

Nitrogen-containing substitutes, such as 1,2,3-triazoles and Mannich bases, are major pharmacophore systems, among others. The presented review summarizes the recent advances (2019–2024) in the synthesis of 1,2,3-triazoles and Mannich bases conjugated with a triterpenic core. These structural modifications have proven to be effective strategies for modulating the biological activity of triterpenes, with particular emphasis on antitumor and antiviral properties. Recent efforts in expanding the structural diversity of triazoles through A-ring modifications and C28 (or C30) substitutions are discussed. Notably, the first examples of N-alkylation of indole triterpenoids by propargyl bromide are presented, along with the application of propargylamine in the synthesis of rare triterpenic aldimines. The review also covers an application of triterpene alkynes in Mannich base synthesis, focusing on functionalization at various positions, including C28 and C19 of the lupane platform, and incorporating of amino acid spacers. While significant progress has been made both in synthetic strategies and pharmacological applications, further research is needed to fully explore the antibacterial, anti-inflammatory, and antidiabetic potential. The review will be useful to researchers in the fields of organic synthesis, natural product and medicinal chemistry, and pharmacology. Full article

Calix[4]resorcinarenes are polyhydroxylated macrocyclic compounds with four units of resorcinol. These compounds can be derivatized through modifications at the upper rim, allowing reactivity with secondary amines to produce Mannich base derivatives via Mannich-type aminomethylation reactions. In this paper, we report the reaction of C-tetra(propyl)calix[4]resorcinarene with piperidine in acetonitrile. The aminomethylated compound C-2,8,14,20-tetra(propyl)-5,11,17,23-tetrakis(N–(piperidine)methyl)calix[4]resorcinarene was obtained with a 52% yield, with an exact mass of 1044.6994 u and a mass error of 7.6 ppm. The reaction progress and product formation were monitored by RP-HPLC, and the compound was characterized using LC ESI-TOF/MS, one- and two-dimensional ¹H and ¹³C NMR, and FTIR spectroscopy. Chromatographic and spectroscopy data are presented and discussed. Full article

There is a strong demand for new and efficient antiviral compounds. A series of 2-hydroxy-1,4-naphthoquinone Mannich bases were screened for their HIV-1-RNase H inhibitory activity. An HIV-1-RNase H assay was used to study the RNase H inhibition by the test compounds. Docking of active derivatives into the active site of the enzyme was carried out. Compounds 1e and 2k showed distinctly higher HIV-1-RNase H inhibitory activity (IC₅₀ = 2.8–3.1 µM) than the known inhibitors RDS1759 and compound 13. The binding mode and possible interactions of 1e and 2k with the HIV-1-RNase H active site were determined using molecular docking, which led to the identification of salient and concealed pharmacophoric features of these molecules. The docking analysis revealed that there are significant differences in the binding mode of these compounds within the active site of the target enzyme. A selection of HIV-1-RNase H-inhibitory Mannich bases was tested for antiviral activity against HIV-1, and compound 2k showed the highest activity at low toxicity to host cells. The lawsone Mannich bases 1e and 2k also underwent a preliminary screening for activity against SARS-CoV-2, and compound 1e was found to inhibit SARS-CoV-2 replication (IC₅₀ = 11.2 µM). Full article