Design, synthesis, theoretical study, antioxidant, and anticholinesterase activities of new pyrazolo-fused phenanthrolines

Pyrazole-fused phenanthroline compounds were obtained through several synthetic routes. NMR, HRMS, and IR techniques were used to characterize and confirm the chemical structures. Crystal structures were obtained from compounds 3a, 5b, 5j, 5k, and 5n and analyzed using X-ray diffraction. Compounds were evaluated as acetyl (AChE) and butyrylcholinesterase (BChE) inhibitors, and the results showed a moderate activity. Compound 5c presented the best activity against AChE (IC50 = 53.29 μM) and compound 5l against BChE enzyme (IC50 = 119.3 μM). Furthermore, the ability of the synthetic compounds to scavenge cationic radicals DPPH and ABTS was evaluated. Compound 5e (EC50 = 26.71 μg mL-1) presented the best results in the DPPH assay, and compounds 5e, 5f and 5g (EC50 = 11.51, 3.10 and <3 μg mL-1, respectively) showed better ABTS cationic radical scavenging results. Finally, in silico analyses indicated that 71% of the compounds show good oral availability and are within the ranges established by the Lipinski criteria.

Regioselective access to di- and trisubstituted pyridines via a metal-oxidant-solvent-free domino reaction involving 3-chloropropiophenones

A remarkable metal-oxidant-solvent- and base-free domino route for regioselective access to a wide range of 2,4-di- and 2,3,4/6-trisubstituted pyridines including carbo- and heterocyclic fused pyridines is reported. This [3C + 2C + 1N] cyclization reaction occurs between 3-chloropropiophenones (3C units), enolizable acyclic/cyclic ketones (2C sources) and NH₄OAc as a robust N source under neat conditions under an open atmosphere, producing new C=C and C=N-C bonds in highly chemo- and regioselective manners. Interestingly, this eco-friendly method has many positive features: excellent functional group tolerance, broad substrate scope, good to excellent regioselectivities, promising yields, no-unwanted products, neutral reaction conditions and appropriateness for large-scale synthesis. Mechanism studies reveal that the in situ generated β-amino ketone from 3-chloropropiophenone and an ammonium salt undergoes C=N bond formation with a ketone followed by an intramolecular cyclization process (C=C bond), which are the decisive steps for pyridine synthesis.

Molecular docking studies, biological evaluation and synthesis of novel 3-mercapto-1,2,4-triazole derivatives

Synthesis of bioactive heterocyclic compounds having effective biological activity is an essential research area for wide-ranging applications. In this study, a conventional methodology has been developed for the synthesis of a series of new 3-mercapto-1,2,4-triazole derivatives 4a-f. The purity and structure of the synthesized molecules were confirmed by ¹H NMR, ¹³C NMR and elemental analysis. In addition, the prepared compounds were screened for their anti-proliferative activity against three human cancer cell lines including A549 (lung cancer), MCF7 (breast cancer) and SKOV3 (ovarian cancer) using MTT reduction assay. All the tested compounds demonstrated remarkable cytotoxic activity with IC₅₀ values ranging from 3.02 to 15.37 µM. The heterocyclic compound bearing 3,4,5-trimethoxy moiety was found to be the most effective among the series displaying an IC₅₀ of 3.02 µM specifically against the ovarian carcinoma cancer cell line (SKOV3). Moreover, Annexin V-FITC/propidium iodide staining assay indicated that this compound can induce apoptosis in SKOV3 cells. Furthermore, cell cycle assay showed a significant cell cycle arrest at the G2/M phase in a dose-dependent manner for this compound. The molecular docking results was showed binding modes of potent compound 4d perfectly corroborated the suggestion of binding to the colchicine site. The entire results conclude that 3-mercapto-1,2,4-triazole derivatives can be synthesized by a green method for biological and pharmacological applications. New analogs of 3-mercapto-1,2,4-triazole potential derivatives for anti-proliferative activity were synthesized. Cytotoxic activity of all synthesized compounds was evaluated against tree human cancer cell lines: lung (A549), breast (MCF7) and ovarian (SKOV3).

A facile solvent-free three-component domino synthesis of novel 2,4-diaryl-5,6-dihydrobenzo[j][1,7]phenanthrolines

A simple, efficient and green procedure for the synthesis of novel 2,4-diaryl-5,6-dihydrobenzo[j][1,7]phenanthrolines has been developed via a Krohnke-type one-pot three-component reaction of 2-[arylmethylidene]-3,4-dihydro-1(2H)-acridinones and (2-aryl-2-oxoethyl)pyridinium bromides in the presence of excess ammonium acetate in good yields under solvent-free conditions. Good functional group tolerance, high substrate scope and no column purification are the practical advantages of this methodology.

A Metal-Free Regioselective Multicomponent Approach for the Synthesis of Free Radical Scavenging Pyrimido-Fused Indazoles and Their Fluorescence Studies

This study deals with a new and efficient metal-free regioselective synthesis of pyrimido-fused indazoles with nitrogen ring junction motifs. We have developed a metal-free domino type reaction between 3-aminoindazole, aryl aldehydes and aceotophenones in the presence of KOH/DMF that leads to pyrimido[1,2-b]indazole analogues. Response Surface Methodology (RSM) coupled with a Box-Behnken design (BBD) were utilized for exploring the effect of base used (A), temperature of reaction (B) and (C), reaction time. This approach can allow access to a variety of pyrimidoindazole fluorophores and related compounds. The compound N,N-dimethyl-4-(2-phenylpyrimido[1,2-b]indazol-4-yl)aniline (4e) displays the maximum fluorescence intensity at 518 nm and shows a fluorescence quantum yield of 0.068. The synthesized pyramido-fused indazoles have been evaluated for their free radical scavenging activity and compound 4f showed good antioxidant activity.

1,2,4-Triazolo-quinazoline-thiones: Non-conventional synthetic approach, study of solvatochromism and antioxidant assessment

A non-conventional methodology has been utilized for the synthesis of a series of 1,2,4-triazolo-quinazoline-thiones (2a-l). Here the reaction was carried out between 1,2,4-triazolo-quinazolinones (1a-l), in the presence of 1,4-dioxane. The mixture was irradiated under microwave (100W) for 7min to obtain targeted molecules (2a-l). All the synthesized molecules were confirmed by (1)H, (13)C NMR and HRMS. The solvatochromic property (absorption spectra) of compounds (2a-l) in solvents of different polarities was studied. The compounds (2a-l) were further subjected for their in vitro free radical screening using 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and also screened for their in vitro anti-fungal property against Aspergillus flavus (A. flavus) and Aspergillus niger (A. niger). The results from free radical scavenging assay showed promising activity for compounds 2a, e-i, whereas compound 2d showed significant antioxidant activity when compared to ascorbic acid. In vitro anti-fungal study showed that the 1,2,4-triazolo-quinazoline-thiones (2a-l) had significant activity against A. flavus and A. niger compared with widely used antifungal agent Fluconazole.

Binding mode of dihydroquinazolinones with lysozyme and its antifungal activity against Aspergillus species

Aspergillosis is one of the infectious fungal diseases affecting mainly the immunocompromised patients. The scarcity of the antifungal targets has identified the importance of N-myristoyl transferase (NMT) in the regulation of fungal pathway. The dihydroquinazolinone molecules were designed on the basis of fragments responsible for binding with the target enzyme. The aryl halide, 1(a-g), aryl boronic acid and potassium carbonate were heated together in water and dioxane mixture to yield new CC bond formation in dihydroquinazolinone. The bis(triphenylphosphine)palladium(II) dichloride was used as catalyst for the CC bond formation. The synthesized series were screened for their in vitro antifungal activity against Aspergillus niger and Aspergillus fumigatus. The binding interactions of the active compound with lysozyme were explored using multiple spectroscopic studies. Molecular docking study of dihydroquinazolinones with the enzyme revealed the information regarding various binding forces involved in the interaction.

Catalytic application of non-toxic Persia americana metabolite entrapped SnO2nanoparticles towards the synthesis of 3,4-dihydroacridin-1(2H)-ones

Synthesized green SnO₂NPs were utilized in organic synthesis. Catalytic application was explored to synthesize 3,4-dihydroacridin-1(2H)-ones.

One-pot synthesis of highly functionalized pyrimido[1,2-b]indazoles via 6-endo-dig cyclization

An efficient synthesis of nitrogen ring junction pyrimido-indazoles has been developed.