Functionalized quinoxalinones as privileged structures with broad-ranging pharmacological activities

Lewis Acid-Mediated Isothiocyanation and Chlorination of Quinoxalin-2(1H)-ones under Visible Light Conditions

Lewis acid-mediated selective C3-isothiocyanation of quinoxalin-2(1H)-ones using N-thiocyanatosaccharin as an isothiocyanate source under visible light conditions at room temperature is described. Under similar conditions with N-chlorosaccharin, the C3-chlorination of quinoxalin-2(1H)-ones achieved a 2 h time frame. Good to an excellent yield of products was obtained in both cases with broad functional group tolerance. Control experiments suggest that the reaction proceeds through a radical mechanism. The present procedure demonstrates the applicability at gram-scale reactions and highlights the subsequent conversion of isothiocyanates into representative thiourea derivatives, and one of the chloro derivatives transformed to glycogen phosphorylase inhibitors.

Convergent Paired Electrolysis for [3+2] Cycloaddition of Azidotrimethylsilane with N-Heterocycles

A widely used method to obtain tetrazoles is through the azide and nitrile [3+2] cycloaddition. However, this process often involves using non-recyclable transition metals or Lewis acid catalysts and stoichiometric amounts of oxidants and additives, which reduces atom efficiency. We have discovered a convergent paired electrochemical reaction to perform this cycloaddition reaction, without the need for metal catalysts or oxidants. This tetrazolation strategy uses azidotrimethylsilane (TMSN3) and N-heterocycles in an undivided cell at a constant current. We use a mixture of CH3CN and equivalent amounts of H2O as co-solvent at room temperature. It is crucial to produce a stoichiometric amount of active hydroxyl ions through the cathodic reduction of water. Cyclic voltammetry (CV) studies and control experiments confirm that the cycloaddition reaction is specific to the electrode electron transfer process, eliminating the need for a mediator to shuttle electrons. This metal- and oxidant-free strategy is highly compatible with different functional groups and produces products with moderate to good yields. We have successfully tetrazolated bioactive compounds at a late stage, scaled up batches efficiently, and synthesized free amino-containing N-heterocycles via denitrogenation of tetrazoles.

Paired Electrolysis-Enabled Arylation of Quinoxalin-2(1H)-ones

The first paired electrolysis-enabled arylation of quinoxalin-2(1H)-ones was achieved using cyanoarenes as the arylation reagents. A variety of 3-arylquinoxalin-2(1H)-ones with various important functional groups were obtained in moderate to good yields under metal- and chemical oxidant-free conditions. With a pair of reductive and oxidative processes occurring among the substrates and reaction intermediates, the power consumption can be dramatically reduced.

Regio- and Stereoselective Intermolecular 1,2-Difunctionalization of Terminal Alkynes: An Approach to Access (Z)-β-Amidovinylsulfones

We have developed the first I2/base-catalyzed regio- and stereoselective intermolecular β-amidosulfonylation of terminal alkynes using sodium sulfinates and quinoxalinone derivatives. The present methodology is compatible with a broad spectrum of various heterocyclic amides, terminal alkynes, and sodium sulfinates. It provides rapid access to valuable (Z)-β-amidovinyl sulfones at mild conditions. Moreover, the synthetic application of this methodology was demonstrated by the late-stage functionalization of numerous bioactive molecules.

Selectfluor Mediated Direct C-H Fluorination of 3-Heteroaryl-Oxindoles

An efficient transition-metal-free fluorination synthesis of N-H-free 3-heteroaryl-oxindoles with Selectfluor was depicted. Under mild reaction conditions, a series of 3-heteroaryl-fluorooxindoles were produced in yield of 62-88% using Selectfluor as a fluorine source.

Vitex Negundo-Fe3O4-CuO green nanocatalyst (VN-Fe3O4-CuO): synthesis of pyrazolo[3,4-c]pyrazole derivatives via the cyclization of isoniazid with pyrazole and their antimicrobial activity, cytotoxicity, and molecular docking studies

In this study, we developed a novel pyrazolo[3,4-c]pyrazole derivative with antibacterial and antifungal activities that shows great potential for treating infectious diseases. To evaluate the binding affinity of 1AJ0 and 1AI9 proteins for developing potent antibacterial and antifungal compounds, we used the Vitex negundo (VN) leaf extract as the capping and reducing agent and reacted it with Fe2O3 and Cu(OAc)2 solutions to synthesize the VN-Fe3O4-CuO nanocatalyst. The newly synthesized compounds were confirmed using Fourier transform infrared spectroscopy, transmission electron microscopy, UV-visible spectroscopy, and X-ray diffraction analyses. Antibacterial screening revealed that compound 1g was highly active against Escherichia coli (MIC: 1 μg mL-1) and was much more effective than the standard ciprofloxacin. Compound 1b showed a higher antifungal activity than clotrimazole against Candida albicans (MIC: 0.25 μg mL-1) and cytotoxic activity against MCF-7 cancer cell lines. Compounds 1a-1l were exhibited low cytotoxicity activity compared to the standard doxorubicin (LC50: 21.05 ± 0.82 μg mL-1). To further support the discovery of new active antibacterial agents, compounds 1g and 1b and proteins 1AJ0 and 1AI9 were examined using the AutoDock Vina program and were compared with the standards ciprofloxacin and clotrimazole. With the 1AJ0 protein, compound 1g had a higher docking score (-3.7 kcal mol-1) than ciprofloxacin (-5.6 kcal mol-1), and with the 1AI9 protein, compound 1b had a higher docking score (-4.8 kcal mol-1) than clotrimazole (-4.4 kcal mol-1). Additionally, molecular dynamics simulation was used to investigate the most probable binding mode of compounds 1b and 1g with 1AI9 and 1AJ0, respectively. The VN-Fe3O4-CuO catalyst was used to prepare pyrazolo[3,4-c]pyrazole derivatives, which were successfully characterized and screened for antimicrobial and cytotoxic activities, molecular docking, and molecular dynamics simulation studies.

Hybrids Diazine: Recent Advancements in Modern Antimicrobial Therapy

Nowadays, antimicrobial therapies have become a very challenging issue because of a large diversity of reasons such as antimicrobial resistance, over consumption and misuse of antimicrobial agents, etc. A modern, actual and very useful approach in antimicrobial therapy is represented by the use of hybrid drugs, especially combined five and six-membered ring azaheterocycles. In this review, we present an overview of the recent advanced data from the last five years in the field of hybrid diazine compounds with antimicrobial activity. In this respect, we highlight here essential data concerning the synthesis and antimicrobial activity of the main classes of diazine hybrids: pyridazine, pyrimidine, pyrazine, and their fused derivatives.

Divergent Synthesis of 3-(Indol-2-yl)quinoxalin-2-ones and 4-(Benzimidazol-2-yl)-3-methyl(aryl)cinnolines via Polyphosphoric Acid (PPA)-Mediated Intramolecular Rearrangements of 3-(Methyl/aryl(2-phenylhydrazono)methyl)quinoxalin-2-ones

Herein, we report a polyphosphoric acid (PPA)-mediated divergent metal-free operation to access a diverse collection of 3-(indol-2-yl)quinoxalin-2-ones and 4-(benzimidazol-2-yl)-3-methylcinnolines in moderate to excellent overall yields. The described process involves two distinct, and competing rearrangements of 3-(methyl(2-phenylhydrazono)methyl)quinoxalin-2-ones, namely [3,3]-sigmatropic Fischer rearrangement with the formation of an indole ring to produce 3-(indol-2-yl)-quinoxalin-2-ones, and Mamedov rearrangement with simultaneous construction of benzimidazole and cinnoline rings to form the new biheterocyclic system─4-(benzimidazol-2-yl)-3-methylcinnolines. The reaction mechanism of both rearrangement channels is explored by extensive dispersion-corrected DFT calculations. It is partcularly remarkable that when 3-(aryl(2-phenylhydrazono)methyl)quinoxalin-2-ones is used, instead of 3-(methyl(2-phenylhydrazono)methyl)quinoxalin-2-ones, reactions proceed regioselectively with the formation of only rearrangement products─4-(benzimidazol-2-yl)-3-arylcinnolines with high yields. This operationally simple protocol enables a rapid access to these scaffolds and is compatible with a wide scope of starting materials. In addition, the new rearrangement found features a promising approach for the design of unique compound libraries for drug design and discovery programs.

Visible-Light-Driven C,N-Selective Heteroarylation of N-Fluoroalkyl Hydroxylamine Reagents with Quinoxalin-2(1H)-ones

Herein, we disclose a direct and powerful strategy for the synthesis of highly valuable α-trifluoromethylamine and N-trifluoroethylamine derivatives from a visible-light-promoted C,N-selective heteroarylation of N-trifluoroethyl hydroxylamine reagents with quinoxalin-2(1H)-ones under ambient conditions. The chemoselectivity of the process (trifluoroalkylation or N-trifluoroethylamination) can easily be dictated and modulated by a selection of N-trifluoroethyl hydroxylamine substrates. The key to success is the protecting group on the N atom of hydroxylamine reagents, which can control the process of 1,2-H shift of the in situ-generated N-trifluoroethyl radical. Remarkable features of this method include mild conditions, easy operation, high selectivity, and excellent functional group tolerability. More importantly, the trifluoroalkylated products can be readily derivatized into other interesting imidazo-fused heterocycles that would be of great potential for the exploitation of pharmaceutically relevant molecules.

Iodine-Mediated C2,3-H Aminoheteroarylation of Indoles

A metal-free one-pot oxidative cross-dehydrogenation coupling reaction for the formation of C-N/C-C bonds at the C2,3-positions of indoles with azoles and quinoxalinones has been developed. The proposed method has several notable features, including metal-free catalysis, the use of N-H free indoles as substrates, ease of operation, mild reaction conditions, and compatibility with a wide range of substrates.

Paraformaldehyde as C1 Synthon: Electrochemical Three-Component Synthesis of Tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones in Aqueous Ethanol

A green and practical method for the electrochemical synthesis of tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones through the three-component reaction of quinoxalin-2(1H)-ones, N-arylglycines and paraformaldehyde was reported. In this strategy, EtOH played dual roles (eco-friendly solvent and waste-free pre-catalyst) and the in situ generated ethoxide promoted triple sequential deprotonations.

Metal-Free Addition of Alkyl Bromides to Access 3,3-Disubstituted Quinoxalinones Enabled by Visible-Light Photoredox Catalysis

A metal-free addition of unactivated alkyl bromides to quinoxalin-2(1H)-ones is described. This method enables the construction of valuable 3,3-disubstituted dihydroquinoxalin-2(1H)-ones bearing quaternary carbon centers under mild, visible-light photoredox catalysis. High functional group tolerance is observed in both the quinoxalinone and alkyl bromide partners. The ability to scale up this method was demonstrated under photo-flow conditions to enable gram-scale synthesis.

A new class of anti-proliferative activity and apoptotic inducer with molecular docking studies for a novel of 1,3-dithiolo[4,5-b]quinoxaline derivatives hybrid with a sulfonamide moiety

A new series of 6-(pyrrolidin-1-ylsulfonyl)-[1,3]dithiolo[4,5-b]quinoxaline-2-ylidines 10a-f, 12, 14, 16, and 18 were designed, synthesized, and evaluated for their in vitro anticancer activity. The structures of the novel compounds were systematically characterized by ¹H NMR, ¹³C NMR, and elemental analysis. The synthesized derivatives were evaluated for their in vitro antiproliferative activity against three human cancer cell lines (HepG-2, HCT-116, and MCF-7) with more sensitivity to MCF-7. Moreover, three derivatives 10c, 10f, and 12 were the most promising candidates with sub-micromole values. These derivatives were further evaluated against MDA-MB-231, and the results displayed significant IC₅₀ values ranging from 2.26 ± 0.1 to 10.46 ± 0.8 μM and showed low cellular cytotoxicity against WI-38. Surprisingly, the most active derivative 12 revealed sensitivity towards the breast cell lines MCF-7 (IC₅₀ = 3.82 ± 0.2 μM) and MDA-MB-231 (IC₅₀ = 2.26 ± 0.1 μM) compared with doxorubicin (IC₅₀ = 4.17 ± 0.2 and 3.18 ± 0.1 M). Cell cycle analysis showed that compound 12 arrests and inhibits the growth of MCF-7 cells in the S phase with values of 48.16% compared with the untreated control 29.79% and exhibited a significantly higher apoptotic effect in MCF-7 with a value of 42.08% compared to control cell at 1.84%. Furthermore, compound 12 decreased Bcl-2 protein 0.368-fold and activation on pro-apoptotic genes Bax and P53 by 3.97 and 4.97 folds, respectively, in MCF-7 cells. Compound 12 exhibited higher inhibitory activity to EGFR^Wt, EGFR^L858R, and VEGFR-2 with IC₅₀ values (0.19 ± 0.009, 0.026 ± 0.001, and 0.42 ± 0.021 μM) compared with erlotinib (IC₅₀ = 0.037 ± 0.002 and 0.026 ± 0.001 μM) and sorafenib (IC₅₀ = 0.035 ± 0.002 μM). Finally, in silico ADMET prediction presented that 1,3-dithiolo[4,5-b]quinoxaline derivative 12 obeys the Lipinski rule of five and the Veber rule with no PAINs alarms and moderately soluble properties. Additionally, toxicity prediction revealed that compound 12 demonstrated inactivity to hepatotoxic carcinogenicity, immunotoxicity, mutagenicity, and cytotoxicity. Moreover, molecular docking studies showed good binding affinity with lower binding energy inside the active site of Bcl-2 (PDB: 4AQ3), EGFR (PDB: 1M17), and VEGFR (PDB: 4ASD).

Acid-Promoted Direct C-H Carbamoylation at the C-3 Position of Quinoxalin-2(1H)-ones with Isocyanide in Water

Described herein is a concise and practical direct amidation at the C-3 position of quinoxalin-2(1H)-ones through an acid-promoted carbamoylation with isocyanide in water. In this conversion, environmentally friendly water and commercial inexpensive isocyanide were used as a solvent and carbamoylation reagent, respectively. This study not only provides a green and efficient strategy for the construction of 3-carbamoylquinoxalin-2(1H)-one derivatives that can be applied to the synthesis of druglike structures but also expands the application of isocyanide in organic chemistry.

Highly efficient synthesis of C3-heteroaryl 3-fluorooxindoles via a one-pot stepwise Ce(iii)/photoassisted cross-dehydrogenative coupling/fluorooxidation process

A one-pot stepwise strategy has been developed to afford C3-heteroaryl 3-fluorooxindoles via a Ce(iii)/photoassisted cross-dehydrogenative coupling/fluorooxidation process in moderate-to-good yields with excellent functional group compatibility.

Quinoxalinones as A Novel Inhibitor Scaffold for EGFR (L858R/T790M/C797S) Tyrosine Kinase: Molecular Docking, Biological Evaluations, and Computational Insights

Combating acquired drug resistance of EGFR tyrosine kinase (TK) is a great challenge and an urgent necessity in the management of non-small cell lung cancers. The advanced EGFR (L858R/T790M/C797S) triple mutation has been recently reported, and there have been no specific drugs approved for this strain. Therefore, our research aimed to search for effective agents that could impede the function of EGFR (L858R/T790M/C797S) TK by the integration of in silico and in vitro approaches. Our in-house quinoxalinone-containing compounds were screened through molecular docking and their biological activity was then verified by enzyme- and cell-based assay. We found that the four quinoxalinone-containing compounds including CPD4, CPD15, CPD16, and CPD21 were promising to be novel EGFR (L858R/T790M/C797S) TK inhibitors. The IC₅₀ values measured by the enzyme-based assay were 3.04 ± 1.24 nM; 6.50 ± 3.02 nM,10.50 ± 1.10 nM; and 3.81 ± 1.80 nM, respectively, which are at a similar level to a reference drug; osimertinib (8.93 ± 3.01 nM). Besides that, they displayed cytotoxic effects on a lung cancer cell line (H1975) with IC₅₀ values in the range of 3.47 to 79.43 μM. In this proposed study, we found that all screened compounds could interact with M793 at the hinge regions and two mutated residues including M790 and S797; which may be the main reason supporting the inhibitory activity in vitro. The structural dynamics revealed that the screened compounds have sufficient non-native contacts with surrounding amino acids and could be well-buried in the binding site's cleft. In addition, all predicted physicochemical parameters were favorable to be drug-like based on Lipinski's rule of five, and no extreme violation of toxicity features was found. Altogether, this study proposes a novel EGFR (L858R/T790M/C797S) TK inhibitor scaffold and provides a detailed understanding of compounds' recognition and susceptibility at the molecular level.

Dual Inhibitors of AChE and BACE-1 for Reducing Aβ in Alzheimer's Disease: From In Silico to In Vivo

Alzheimer's disease (AD) is a complex and widespread condition, still not fully understood and with no cure yet. Amyloid beta (Aβ) peptide is suspected to be a major cause of AD, and therefore, simultaneously blocking its formation and aggregation by inhibition of the enzymes BACE-1 (β-secretase) and AChE (acetylcholinesterase) by a single inhibitor may be an effective therapeutic approach, as compared to blocking one of these targets or by combining two drugs, one for each of these targets. We used our ISE algorithm to model each of the AChE peripheral site inhibitors and BACE-1 inhibitors, on the basis of published data, and constructed classification models for each. Subsequently, we screened large molecular databases with both models. Top scored molecules were docked into AChE and BACE-1 crystal structures, and 36 Molecules with the best weighted scores (based on ISE indexes and docking results) were sent for inhibition studies on the two enzymes. Two of them inhibited both AChE (IC₅₀ between 4-7 μM) and BACE-1 (IC₅₀ between 50-65 μM). Two additional molecules inhibited only AChE, and another two molecules inhibited only BACE-1. Preliminary testing of inhibition by F681-0222 (molecule 2) on APPswe/PS1dE9 transgenic mice shows a reduction in brain tissue of soluble Aβ42.

Design and synthesis of new bis(1,2,4-triazolo[3,4-b][1,3,4]thiadiazines) and bis((quinoxalin-2-yl)phenoxy)alkanes as anti-breast cancer agents through dual PARP-1 and EGFR targets inhibition

A number of new 1,ω-bis((acetylphenoxy)acetamide)alkanes 5a–f were prepared then their bromination using NBS furnished the novel bis(2-bromoacetyl)phenoxy)acetamides 6a–f. Reaction of 6a–f with 4-amino-5-substituted-4H-1,2,4-triazole-3-thiol 7a–d and with o-phenylenediamine derivatives 9a and b afforded the corresponding bis(1,2,4-triazolo[3,4-b][1,3,4]thiadiazine) derivatives 8a–l and bis(quinoxaline) derivatives 10a–e in good yields. The cytotoxicity of the synthesized compounds as well as apoptosis induction through PARP-1 and EGFR as molecular targets was evaluated. Three compounds, 8d, 8i and 8l, exhibited much better cytotoxic activities against MDA-MB-231 than the drug Erlotinib. Interestingly, compound 8i induced apoptosis in MDA-MB-231 cells by 38-fold compared to the control arresting the cell cycle at the G2/M phase, and its treatment upregulated P53, Bax, caspase-3, caspase-8, and caspase-9 gene levels, while it downregulated the Bcl2 level. Compound 8i exhibited promising dual enzyme inhibition of PARP-1 (IC₅₀ = 1.37 nM) compared to Olaparib (IC₅₀ = 1.49 nM), and EGFR (IC₅₀ = 64.65 nM) compared to Erlotinib (IC₅₀ = 80 nM). These results agreed with the molecular docking studies that highlighted the binding disposition of compound 8i inside the PARP-1 and EGFR protein active sites. Hence, compound 8i may serve as a potential anti-breast cancer agent.

A series of bis(triazolothiadiazines) and bis(quinoxalines) were synthesized and tested for their cytotoxicity and apoptosis-induction through PARP-1 and EGFR as molecular targets. Compound 8i exhibited high cytotoxic activity and promising dual enzyme inhibition.