Differential characterization using readily accessible NMR experiments of novel N- and O-alkylated quinolin-4-ol, 1,5-naphthyridin-4-ol and quinazolin-4-ol derivatives with antimycobacterial activity

Base-Catalyzed Chemo-, Regio- and Stereoselective Addition of Quinazolinones to Trifluoromethylated Internal Alkynes for Access to N3-Vinylquinazolinones

A base-catalyzed addition of quinazolinones to unsymmetrical trifluoromethylated internal alkynes was accomplished for straightforward access to various N3-vinylquinazolinones. Excellent chemo-, regio-, and stereoselectivity were achieved along with moderate to good efficacy for broad substrate scope under environmentally benign conditions. Moreover, N3-vinylquinazolinone adducts could be readily transformed into a useful fused tetracyclic scaffold via one-step intramolecular oxidative cross-coupling. On the basis of preliminary control experiment results, a catalytic cycle was proposed to clarify a plausible reaction mechanism.

Modular and divergent synthesis of 2,N3-disubstituted 4-quinazolinones facilitated by regioselective N-alkylation

The synthesis of a biologically relevant 2-amino-N3-alkylamido 4-quinazolinone has been accomplished in four steps from commercially available materials using design principles from both modular and divergent synthesis. N3-Alkylation of 2-chloro-4(3H)-quinazolinone using methyl bromoacetate, followed by C2-amination produced a suitable scaffold for introducing molecular diversity. Optimization of alkylation conditions afforded full regioselectivity, enabling exclusive access to the N-alkylated isomer. Subsequent C2-amination using piperidine, pyrrolidine, or diethylamine, followed by amide bond formation using variously substituted phenethylamines, generated fifteen unique 4-quinazolinones bearing C2-amino and N3-alkylamido substituents. These efforts highlight the reciprocal influence of C2 and N3 substitution on functionalization at either position, establish an effective synthetic pathway toward 2,N3-disubstituted 4-quinazolinones, and enable preliminary bioactivity studies while providing an experiential learning opportunity for undergraduate student researchers.

Novel quinazolines bearing 1,3,4-thiadiazole-aryl urea derivative as anticancer agents: design, synthesis, molecular docking, DFT and bioactivity evaluations

A novel series of 1-(5-((6-nitroquinazoline-4-yl)thio)-1,3,4-thiadiazol-2-yl)-3-phenylurea derivatives 8 were designed and synthesized to evaluate their cytotoxic potencies. The structures of these obtained compounds were thoroughly characterized by IR, 1H, and 13C NMR, MASS spectroscopy and elemental analysis methods. Additionally, their in vitro anticancer activities were investigated using the MTT assay against A549 (human lung cancer), MDA-MB231 (human triple-negative breast cancer), and MCF7 (human hormone-dependent breast cancer). Etoposide was used as a reference marketed drug for comparison. Among the compounds tested, compounds 8b and 8c demonstrated acceptable antiproliferative activity, particularly against MCF7 cells. Considering the potential VEGFR-2 inhibitor potency of these compounds, a molecular docking study was performed for the most potent compound, 8c, to determine its probable interactions. Furthermore, computational investigations, including molecular dynamics, frontier molecular orbital analysis, Fukui reactivity descriptor, electrostatic potential surface, and in silico ADME evaluation for all compounds were performed to illustrate the structure-activity relationship (SAR).

Design, Synthesis, and Structure-Activity Relationship of Quinazolinone Derivatives as Potential Fungicides

Plant diseases caused by phytopathogenic fungi reduce the yield and quality of crops. To develop novel antifungal agents, we designed and synthesized eight series of quinazolinone derivatives and evaluated their anti-phytopathogenic fungal activity. The bioassay results revealed that compounds KZL-15, KZL-22, 5b, 6b, 6c, 8e, and 8f exhibited remarkable antifungal activity in vitro. Especially, compound 6c displayed the highest bioactivity against Sclerotinia sclerotiorum, Pellicularia sasakii, Fusarium graminearum, and Fusarium oxysporum, displaying appreciable IC₅₀ values (50% inhibitory concentration) of 2.46, 2.94, 6.03, and 11.9 μg/mL, respectively. A further mechanism interrogation revealed abnormal mycelia, damaged organelles, and changed permeability of cell membranes in S. sclerotiorum treated with compound 6c. In addition, the in vivo bioassay indicated that compound 6c possessed comparable curative and protective effects (87.3 and 90.7%, respectively) to the positive control azoxystrobin (89.5 and 91.2%, respectively) at 100 μg/mL concentration against S. sclerotiorum. This work validated the potential of compound 6c as a new and promising fungicide candidate, contributing to the exploration of potent antifungal agents.

Metal-free synthesis of 1,4-benzodiazepines and quinazolinones from hexafluoroisopropyl 2-aminobenzoates at room temperature

Herein, we describe the novel reactivity of hexafluoroisopropyl 2-aminobenzoates. The metal-free synthesis of 1,4-benzodiazepines and quinazolinones from hexafluoroisopropyl 2-aminobenzoates has been developed at room temperature. These procedures feature good functional group tolerance, mild reaction conditions, and excellent yields. The newly formed products can readily be converted to other useful N-heterocycles. Moreover, the products and their derivatives showed potent anticancer activities in vitro by MTT assay.

A metal-free synthesis of 1,4-benzodiazepines and quinazolinones from hexafluoroisopropyl 2-aminobenzoates has been developed at room temperature.

Competition between N and O: use of diazine N-oxides as a test case for the Marcus theory rationale for ambident reactivity

The preferred site of alkylation of diazine N-oxides by representative hard and soft alkylating agents was established conclusively using the 1H-15N HMBC NMR technique in combination with other NMR spectroscopic methods. Alkylation of pyrazine N-oxides (1 and 2) occurs preferentially on nitrogen regardless of the alkylating agent employed, while O-methylation of pyrimidine N-oxide (3) is favoured in its reaction with MeOTf. As these outcomes cannot be explained in the context of the hard/soft acid/base (HSAB) principle, we have instead turned to Marcus theory to rationalise these results. Marcus intrinsic barriers (ΔG ‡ 0) and Δr G° values were calculated at the DLPNO-CCSD(T)/def2-TZVPPD/SMD//M06-2X-D3/6-311+G(d,p)/SMD level of theory for methylation reactions of 1 and 3 by MeI and MeOTf, and used to derive Gibbs energies of activation (ΔG ‡) for the processes of N- and O-methylation, respectively. These values, as well as those derived directly from the DFT calculations, closely reproduce the observed experimental N- vs. O-alkylation selectivities for methylation reactions of 1 and 3, indicating that Marcus theory can be used in a semi-quantitative manner to understand how the activation barriers for these reactions are constructed. It was found that N-alkylation of 1 is favoured due to the dominant contribution of Δr G° to the activation barrier in this case, while O-alkylation of 3 is favoured due to the dominant contribution of the intrinsic barrier (ΔG ‡ 0) for this process. These results are of profound significance in understanding the outcomes of reactions of ambident reactants in general.