Search Results (90)

Six 9-thienyl-10-aryl-substituted 3,3,6,6-tetramethyl-decahydroacridine-1,8-diones (5a–f) were prepared by two acid-mediated routes that used the same solvent, temperature, and reaction time. In the sequential route, preformed 5,5-dimethyl-3-(arylamino)cyclohex-2-enones were reacted with a heteroaryl aldehyde and dimedone; in the corresponding one-pot route, the arylamine, heteroaryl aldehyde, and two equivalents of dimedone were combined directly. The isolated yields of the product-forming second stage were 71–75%, corresponding to calculated overall two-step yields of 58.2–68.6% after accounting for the isolated enaminone-preparation yields. These overall yields remained higher than those of the one-pot procedure (40–47%), although the sequential protocol required an additional reaction, isolation, catalyst charge, and solvent-intensive operation. Structural assignments were based on the available IR, ¹H NMR, ¹³C NMR, and EI-MS data. Tetrahydroacridinone by-products 6a–c were isolated in 13–15% yields and showed diagnostic spectral changes relative to 5a–f, including loss of the C-9 methine resonance and appearance of a strongly deshielded aromatic proton at 9.17–9.21 ppm. Within the limitations of an operational preparative comparison, the product distribution is consistent with a sequence-control interpretation in which preformation of the β-enaminone favors the 1:1:2 aldehyde/amine/dimedone product, whereas simultaneous component activation permits competing Knoevenagel, xanthene-forming, and aromatization pathways. This study provides a practical synthesis of thienyl-substituted decahydroacridine-1,8-diones and a mechanistically cautious explanation for the reduced selectivity of the one-pot process. Full article

An operationally simple procedure for the synthesis of 2-alkyl-4-quinolone N-oxides, relying on controlled platinum-catalyzed partial hydrogenation of 2-nitrobenzoyl enamines, has been developed. The Pseudomonas aeruginosa metabolite 2-heptyl-4-quinolone-N-oxide (HQNO) and four analogous products have been prepared in good yield and high purity by this method. All products showed ampholytic properties, with a tendency to form isolable organic-soluble hydrochlorides by switching from the N-hydroxy-4-quinolone to 4-hydroxyquinoline-N-oxide tautomeric form upon partitioning between dichloromethane and 1M aqueous HCl. In basic medium, on the other hand, water-soluble salts of the N-hydroxy-4-quinolone tautomers were formed. NMR measurements indicate pH-dependent equilibrium with fast exchange between the 4-quinolone and the protonated 4-quinolinol tautomer. Full article

Herein, a facile and efficient strategy for one-pot synthesis of 3-aminoalkyl chromones from o-hydroxyaryl enaminones and aromatic amines using inexpensive rongalite as a C1 source has been developed. This three-component protocol enables domino aminomethylation and annulation of o-hydroxyphenyl enaminones without the need for transition metals or oxidants, featuring simple operation, a broad substrate scope, and readily available raw materials, providing a series of 3-aminomethyl chromones in moderate-to-good yields. Full article

Bidentate ligands, derived from the 1,3-dicarbonyl framework, play a central role in coordination chemistry, catalysis, and materials science due to their tuneable donor properties and structural versatility. This review examines and compares three closely related ligand classes, β-diketones (O,O′ donors), imino-β-diketones or enaminones (N,O donors), and di-imino-β-diketones or β-diketiminates (N,N′ donors), to elucidate how systematic substitution of oxygen by nitrogen affects structure and properties. The discussion integrates spectroscopic data (NMR and IR), crystallographic findings, electrochemical measurements, and density functional theory (DFT) calculations reported in the literature. Across these systems, tautomerism plays a decisive role, with conjugation-stabilized enol or enamine forms generally preferred in solution and the solid state. Frontier molecular orbital analyses show extensive delocalization over the chelate backbone and, when present, aromatic substituents. Electrochemical studies reveal consistent correlations between experimental reduction potentials and calculated LUMO energies for O,O′-, N,O-, and N,N′-bidentate ligands. Overall, the comparison demonstrates that donor atom substitution within a conserved conjugated scaffold provides a systematic approach to tuning acidity, coordination behaviour, and redox properties, offering a coherent framework for understanding structure–property relationships in 1,3-dicarbonyl-derived chelating ligands. Full article

Herein, we disclose a highly efficient pathway toward 3-selenylated chromone derivatives via electrosynthesis domino C(sp²)-H bond selenylation/cyclization/deamination of 2-hydroxyaryl enaminones with diselenides. This method showed mild conditions, easy operation, a wide substrate scope, and good functional group tolerance. Furthermore, this electrosynthesis strategy was amenable to scaling up the reaction. Additionally, the preliminary experiments revealed that this reaction probably proceeded via a cation pathway instead of a radical pathway. Full article

Density functional theory (DFT) calculations at the M06-2X-D3/6-311++G(2df,2pd) level elucidate the mechanism and selectivity origins in the NHC-catalyzed divergent synthesis of spirocyclopentane oxindoles from isatin-derived enals and N-sulfonyl ketimines. The Michael addition constitutes the regio- and stereoselectivity-determining step, where Parr function analysis demonstrates that nucleophile/electrophile electrophilicity governs regioselectivity, while distortion/interaction and non-covalent interaction analyses reveal stereoselectivity is controlled by distortion and weak interactions. K₃PO₄ facilitates Breslow intermediate formation and proton transfer toward the β-lactam-fused spirocyclopentane oxindole, whereas N,N-diisopropylethylamine (DIPEA) promotes these processes for the spirocyclopentane oxindole bearing an enaminone moiety. Catalyst roles are also further delineated. Full article

Two pyrene derivatives, substituted at position 1 with isoxazole or NH-pyrazole, were synthesized in 85–87% yield starting from 1-acetylpyrene and via the cyclocondensation reaction of a β-enaminone intermediate with hydroxylamine or hydrazine. The photophysics of the two 5-(1-pyrenyl)-1,2-azoles were explored, revealing that only the isoxazole derivative exhibits good emission properties (ϕ_F ≥ 74%) but without solvatofluorochromism behavior. However, both probes exhibited noticeable photophysics in the aggregated state (in the presence of H₂O and/or in the solid state) and through acid–base interactions (using TFA and TBACN), leveraging the basic and acidic character of the analyzed 1,2-azoles, which was also investigated by ¹H NMR spectroscopy. Therefore, the selective incorporation of N-heteroaromatic units into the pyrene scaffold effectively modulates the photophysics and environmental sensitivity of the corresponding probes. Full article

A novel, eco-friendly, and efficient method for constructing 2,3-disubstituted chromone skeletons from readily available water, o-hydroxyaryl enaminones (o-HPEs), and aryldiazonium salts has been developed under mild reaction conditions. This α,β-C(sp²)–H bond difunctionalization/chromone annulation reaction strategy is achieved by building two C(sp³)–O bonds and a C(sp²)-N bond, which provides a practical pathway for the preparation of 2-hydroxy-3-hydrazono-chromones in moderate to excellent yields, enabling broad substrate scope and good functional group tolerance, as well as gram-scale synthesis. This protocol offers a valuable tool for synthesizing diverse functionalized chromones with potential applications in drug discovery and industrial synthesis. Full article

A series of differently substituted β-enaminones 2a,b, 4a–i, 8a–d, and 9–13, their BF₂-β-ketoiminate complexes 5a–d, and BF₂-β-diketonate complexes 6a–d were prepared as model substrates for photochemical transformations. The attempted photochemical transformations of enaminones 2, 4, 8 and BF₂-β-ketoiminate complexes 5 failed. On the other hand, irradiation of mixtures of BF₂-β-diketonate complexes 6a–d and cycloalkanes with UV-A light (365 nm) gave the corresponding De Mayo reaction products 7a–f in 9–30% yields. The photochemical ring-expansion of acetyl tetralone-derived BF₂-complex 6d gave novel diannulated cyclooctane derivatives 7e and 7f, which would be difficult to obtain using conventional cyclization methods. Full article

In this study, we present the HOAc-catalyzed selective cleavage of the C=C double bond of enaminones, enabling the formation of a new C–N bond and a new C=N bond for the one-pot synthesis of 2-substituted 3,4-dihydroquinazolines directly from ynones and 2-(aminomethyl)anilines. This method operates in ethanol under transition-metal-free and oxidant-free conditions, offering a sustainable and efficient approach for the synthesis of 3,4-dihydroquinazolines with broad functional group tolerance. Full article

Organic compounds with 1,3-diketone or 3-amino enone functional groups are extremely important as they can be converted into a plethora of carbo- or heterocyclic derivatives or can be used as ligands in the formation of metal complexes. Here, we have achieved the preparation of a series of non-symmetrical β-ketoenamines (O,N,N proligand) of the type (4-MeOC₆H₄)C(=O)CH=C(R)NH(Q) obtained through the Schiff base condensation of 1,3-diketones (1-anisoylacetone, 1-anisyl-3-(4-cyanophenyl)-1,3-propanedione, and 1-anisyl-3-(4,4,4-trifluorotolyl)-1,3-propanedione) functionalized with electron donor and electron-withdrawing substituents and 8-aminoquinoline (R = CH₃, 4-C₆H₄CN, 4-C₆H₄CF₃; Q = C₉H₇N). Schiff base ketoimines with a pendant quinolyl moiety were isolated as single regioisomers in yields of 22–56% and characterized with FT-IR, ¹H NMR, and UV-visible spectroscopy, as well as single-crystal X-ray crystallography, which allowed for the elucidation of the nature of the isolated regioisomers. The regioselectivity of the condensation of electronically unsymmetrical 1,3-diaryl-1,3-diketones with 8-aminoquinoline was studied by ¹H NMR, providing regioisomer ratios of ~3:1 and ~2:1 in the case of CN and CF₃ substituents, respectively. The electronic effects correlate well with the difference between the Hammett σ⁺ coefficients of the two para substituents on the aryl rings. Full article

Carbonic anhydrases (CAs) are a group of zinc-containing enzymes involved in many physiological processes through their role in the maintenance of the equilibrium between bicarbonate and CO₂ levels. Human carbonic anhydrases (hCAs) are recognized as important drug targets due to their major implication in the development of diseases including cancer. Sulfanilamide derivatives have been widely studied and have shown remarkable efficiency in inhibiting carbonic anhydrases, with the presence of SO₂NH₂ in their structure. Therefore, the sulfonamide moiety is considered as the leading scaffold in the search for new hCA inhibitors. Moreover, the introduction of an enaminone to sulfonamide-based CA inhibitors showed an enhancement of inhibitory activity. In this context, we were interested in the in silico investigation of benzenesulfonamide derivatives containing β-enaminone that were synthesized from dicarbonyl compounds and sulfanilamide under microwave irradiation. The in silico assessment includes a molecular docking simulation against hCA II (PDB: 2AW1). The docked ligands showed good docking score values (−8.099 and −7.053 kcal.mol⁻¹), which indicates a good stability of the studied compounds within the active site. Further, significant interactions with the residues of the active site were observed, including metal coordination with Zn 262, an H-bond with Thr 199, and pi–pi stacking with the side chain of His94, which are considered as the key interactions for CA inhibition. A complementary in silico study that involved ADMET prediction was performed to learn more about the pharmacokinetic properties and the toxicity of the products in order to comprehend their ability to become drug-candidates. Full article

Commercial DCE is excavated as both a “Cl” source and a solvent for the vinyl C(sp²)-H chlorination. The strategy involves a metal-free NBS-mediated C(sp²)-H chlorination of enaminones, and affords diverse, functionalized α-chlorinated enaminones with a Z-configuration. This mild and effective approach not only advances the vinyl C(sp²)-H chlorination, employing DCE as the “Cl” source, but also provides a new strategy for accessing chlorinated enaminone derivatives. Full article