Synthesis of new arylaminoquinoxalines and their antimalarial activity in mice

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.

Design, synthesis, and molecular docking studies of diphenylquinoxaline-6-carbohydrazide hybrids as potent α-glucosidase inhibitors

A novel series of diphenylquinoxaline-6-carbohydrazide hybrids 7a–o were rationally designed and synthesized as anti-diabetic agents. All synthesized compounds 7a–o were screened as possible α-glucosidase inhibitors and exhibited good inhibitory activity with IC₅₀ values in the range of 110.6 ± 6.0 to 453.0 ± 4.7 µM in comparison with acarbose as the positive control (750.0 ± 10.5 µM). An exception in this trend came back to a compound 7k with IC₅₀ value > 750 µM. Furthermore, the most potent derivative 7e bearing 3-fluorophenyl moiety was further explored by kinetic studies and showed the competitive type of inhibition. Additionally, the molecular docking of all derivatives was performed to get an insight into the binding mode of these derivatives within the active site of the enzyme. In silico assessments exhibited that 7e was well occupied in the binding pocket of the enzyme through favorable interactions with residues, correlating to the experimental results.

Synthesis of cinnamils and quinoxalines and their biological evaluation as anticancer agents

We synthesized multiple cinnamils and quinoxalines to evaluate their anticancer activity. Cinnamils were used as precursors for quinoxalines via condensation with 1,2-diaminobenzene. Among the 26 synthesized compounds reported in this article, we found that cinnamil 3l exhibited its inhibitory effect with an IC50 value of 1.45 ± 0.98 μM, significantly higher than doxorubicin (8.5 ± 0.85 μM) against pancreatic cancer cells (PANC-1). Additionally, cinnamil 3l (IC50 10.98 ± 3.63 μM) showed less cytotoxicity than doxorubicin to Hs68 cells (0.92 ± 1.11 μM). The colony formation assay demonstrated that 3l obviously decreased the PANC-1 cell viability, and Western blot assays confirmed that 3l markedly induced apoptosis of PANC-1 cells through Bax, Bcl-2, and caspase 3 signaling cascades. These results demonstrate that cinnamil 3l has great potential to be further developed as a promising chemotherapeutic agent for pancreatic cancer.

Electrochemical Oxidative C-H Arylation of Quinoxalin(on)es with Arylhydrazine Hydrochlorides under Mild Conditions

A practical and scalable protocol for electrochemical arylation of quinoxalin(on)es with arylhydrazine hydrochlorides under mild conditions has been developed. This method exhibits high efficiency, easy scalability, and broad functional group tolerance. Various quinoxalin(on)es and arylhydrazines underwent this transformation smoothly in an undivided cell, providing the corresponding aryl-substituted quinoxalin(on)es in moderate to good yields. A radical mechanism is involved in this arylation reaction.

Sustainable C–H activation approach for palladium-catalyzed, regioselective functionalization of 1-methyl-3-phenyl quinoxaline-2(1H)-ones in water

An environment-friendly approach for regioselective acylation of 1-methyl-3-phenyl quinoxaline-2(1H)-ones was developed using water as a solvent. The protocol exhibits a wide substrate scope and employs commercially available, non-toxic acyl surrogates.

Recent advances in the transition-metal-free synthesis of quinoxalines

Quinoxalines, also known as benzo[a]pyrazines, constitute an important class of nitrogen-containing heterocyclic compounds as a result of their widespread prevalence in natural products, biologically active synthetic drug candidates, and optoelectronic materials. Owing to their importance and chemists' ever-increasing imagination of new transformations of these products, tremendous efforts have been dedicated to finding more efficient approaches toward the synthesis of quinoxaline rings. The last decades have witnessed a marvellous outburst in modifying organic synthetic methods to create them sustainable for the betterment of our environment. The exploitation of transition-metal-free catalysis in organic synthesis leads to a new frontier to access biologically active heterocycles and provides an alternative method from the perspective of green and sustainable chemistry. Despite notable developments achieved in transition-metal catalyzed synthesis, the high cost involved in the preparation of the catalyst, toxicity, and difficulty in removing it from the final products constitute disadvantageous effects on the atom economy and eco-friendly nature of the transformation. In this review article, we have summarized the recent progress achieved in the synthesis of quinoxalines under transition-metal-free conditions and cover the reports from 2015 to date. This aspect is presented alongside the mechanistic rationalization and limitations of the reaction methodologies. The scopes of future developments are also highlighted.

Synthesis and Antimicrobial Activity of Novel 1, 2, 4-Triazolopyrimidofuroquinazolinones from Natural Furochromones (Visnagenone and Khellinone)

BACKGROUND

Previous and recent scientific research has shown that triazolopyrimidine and furochromones have a wide range of pharmacological activities for the treatment of numerous diseases, including anticancer, antiviral, anti-depressant, anti-microbial, anti-inflammatory, and analgesic activities.

OBJECTIVE

Preparation of new drugs derived from a natural furochromones as (1-hydrazinyl or methylthio),-furopyrimidoquinazolinone, 1, 2, 4-triazolopyrimidofuroquinazolin-5-one, and quinazoline- pyrimidofuro- quinazoline-8, 10-dione and the study of their biological activity as antimicrobial agents.

METHODS

A series of novel N'-furopyrimidoquinazoline-hydrazide; 1, 2, 4-triazolopyrimidofuroquinazolin- 5-one; furopyrimidoquinazolin-3-one and quinazoline-pyrimidofuroquinazoline-8, 10- dione derivatives were synthesized from substituted (methylthio)-furopyrimidoquinazolinone (3ab) and 1-hydrazinyl-furopyrimido- quinazolinone (4a-b) as the starting material.

RESULTS

All compounds were synthesized in good yields (71-95%) in a gradually efficient system under mild condition and some of the procedures were used such as microwave oven. The new compounds have been confirmed by means of different spectroscopic methods such as IR, 1D and 2D -NMR techniques and mass spectrum. The in vitro antimicrobial activities were evaluated for the prepared compounds using many types of bacteria (Gram-positive and Gram-negative) and fungi.

CONCLUSION

1, 2, 4-triazolopyrimidofuroquinazolin-5-one derivatives (10a-f, 8a-b, 7a-b and 6a-d) showed the most efficient antimicrobial activities compared with the cefotaxime sodium and nystatin as standard drugs.

Recent Updates on the Synthesis of Bioactive Quinoxaline-Containing Sulfonamides

Quinoxaline is a privileged pharmacophore that has broad-spectrum applications in the fields of medicine, pharmacology and pharmaceutics. Similarly, the sulfonamide moiety is of considerable interest in medicinal chemistry, as it exhibits a wide range of pharmacological activities. Therefore, the therapeutic potential and biomedical applications of quinoxalines have been enhanced by incorporation of the sulfonamide group into their chemical framework. The present review surveyed the literature on the preparation, biological activities and structure-activity relationship (SAR) of quinoxaline sulfonamide derivatives due to their broad range of biomedical activities, such as diuretic, antibacterial, antifungal, neuropharmacological, antileishmanial, anti-inflammatory, anti-tumor and anticancer action. The current biological diagnostic findings in this literature review suggest that quinoxaline-linked sulfonamide hybrids are capable of being established as lead compounds; modifications on quinoxaline sulfonamide derivatives may give rise to advanced therapeutic agents against a wide variety of diseases.

Novel Ionic Liquid-Functionalized Chitosan [DSIM][AlCl3] x -@CS: Synthesis, Characterization, and Catalytic Application for Preparation of Substituted Pyrazine Derivatives

Pyrazines are renowned heterocyclic compounds that have played an important role in drug design and are part of many polycyclic compounds of biological and industrial significance. In this article, a novel chitosan-immobilized ionic liquid, [DSIM][AlCl₃] _x ^-@CS, has been synthesized easily at ambient temperature and used for catalyzing the synthesis of a series of biologically relevant pyrazine derivatives. The catalyst is well characterized by various techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, solid-state ¹³C MAS nuclear magnetic resonance, scanning electron microscopy/energy-dispersive X-ray, elemental mapping, transmission electron microscopy, powder X-ray diffraction, and thermal gravimetric analyses. The advantageous features of the present energy-sustainable methodology include high yield of product (>99%), shorter reaction time periods, and recyclability of the catalyst.

Design, synthesis, in silico docking studies and biological evaluation of novel quinoxaline-hydrazide hydrazone-1,2,3-triazole hybrids as α-glucosidase inhibitors and antioxidants

Novel quinoxaline-hydrazidehydrazone-1,2,3-triazole hybrids were synthesized, characterized and screened for α-glucosidase inhibitory and antioxidant activities.

Visible-light-promoted direct C–H/S–H cross-coupling of quinoxalin-2(1H)-ones with thiols leading to 3-sulfenylated quinoxalin-2(1H)-ones in air

A new and efficient visible-light-mediated strategy has been developed for the synthesis of 3-sulfenylated quinoxalin-2(1H)-ones via rhodamine B catalyzed C–H/S–H cross-coupling of quinoxalin-2(1H)-ones with thiols in air at room temperature.

An efficient and environmentally sustainable domino protocol for the synthesis of structurally diverse spiroannulated pyrimidophenazines using erbium doped TiO2 nanoparticles as a recyclable and reusable heterogeneous acid catalyst

An efficient and environmentally sustainable domino protocol has been presented for the synthesis of structurally diverse spiroannulated pyrimidophenazines involving a four component reaction of 2-hydroxynaphthalene-1,4-dione, benzene-1,2-diamine, cyclic ketones and amino derivatives in the presence of erbium doped TiO2 nanoparticles as a recyclable and reusable heterogeneous acid catalyst. The present synthetic protocol features mild reaction conditions with operational simplicity, excellent yield with high purity, short reaction time and high atom economy with the use of a recoverable and reusable environmentally sustainable heterogeneous catalyst.

Metal-free direct oxidative C–C bond coupling of pyrazolones and quinoxalinones

An efficient oxidative dehydrogenative coupling of quinoxalinones and pyrazolones has been successfully developed using a readily available persulfate oxidant. This protocol provides facile access to a wide array of hydroxy-pyrazolyl quinoxalinones in good to excellent yields.

Persulfate-promoted oxidative C–N bond coupling of quinoxalinones andNH-sulfoximines

A simple approach for a direct sulfoximination of quinoxalinonesviaK₂S₂O₈-mediated oxidative coupling is reported.

Design and synthesis of the BODIPY-BSA complex for biological applications

A quinoxaline-functionalized styryl-BODIPY derivative (S1) was synthesized by microwave-assisted Knoevenagel condensation. It exhibited fluorescence enhancement upon micro-encapsulation into the hydrophobic cavity of bovine serum albumin (BSA). The S1-BSA complex was characterized systematically using ultraviolet (UV)-visible absorption, fluorescence emission, kinetics, circular dichroism and time-resolved lifetime measurements. The binding nature of BSA towards S1 was strong, and was found to be stable over a period of days. The studies showed that the S1-BSA complex could be used as a new biomaterial for fluorescence-based high-throughput assay for kinase enzymes.

Copper-catalysed oxidative amination of quinoxalin-2(1H)-ones with aliphatic amines

A novel, efficient and practical method for copper-catalysed oxidative C-3 amination of quinoxalin-2(1H)-ones with primary or secondary amines as the nitrogen sources has been developed.

Design, synthesis, antifungal, and antioxidant activities of (E)-6-((2-phenylhydrazono)methyl)quinoxaline derivatives

Different substituted phenylhydrazone groups were linked to the quinoxaline scaffold to provide 26 compounds (6a-6z). Their structures were confirmed by (1)H and (13)C NMR, MS, elemental analysis, and X-ray single-crystal diffraction. The antifungal activities of these compounds against Rhizoctonia solani were evaluated in vitro. Compound 6p is the most promising one among all the tested compounds with an EC50 of 0.16 μg·mL(-1), more potent than the coassayed positive control fungicide carbendazim (EC50: 1.42 μg·mL(-1)). In addition, these compounds were subjected to antioxidant assay by employing diphenylpicrylhydrazyl (DPPH) and mice microsome lipid peroxidation (LPO) methods. Most of these compounds are potent antioxidants. The strongest compounds are 6e (EC50: 7.60 μg·mL(-1), DPPH) and 6a (EC50: 0.96 μg·mL(-1), LPO), comparative to or more potent than the positive control Trolox [EC50: 5.90 μg·mL(-1) (DPPH) and 18.23 μg·mL(-1) (LPO)]. The structure and activity relationships were also discussed.

Biological assay of a novel quinoxalinone with antimalarial efficacy on Plasmodium yoelii yoelii

Compound 1-methyl-7-nitro-4-(5-(piperidin-1-yl)pentyl)-3,4-dihydroquinoxalin-2(1H)-one (VAM2-6) was evaluated against a blood-induced infection with chloroquine-sensitive Plasmodium yoelii yoelii lethal strain in CD1 mice in a 4-day test scheme. LD50 of the compound was 56.51 mg/kg and LD10 was 20.58 mg/kg (taken as the highest dose). Animals were treated by oral gavage of 20, 10, and 5 mg/kg. Mice in the untreated control group showed a progressively increasing parasitemia leading to mouse death on 6 days post-infection; in this group, all mice showed parasites in the blood on the fifth day of sampling; the mean parasitemia on that day was 19.4%. A 4-day dosage of 20 mg/kg of VAM2-6 showed a 97% chemosuppression of total parasitemia on the fifth day, a 28 days survival time, and 20% of cured animals. A 4-day dosage of 10 and 5 mg/kg showed 85 and 37%, respectively, chemosuppression of total parasitemia on the fifth day; but all mice died from days 6 to 9 post-infection with increasing parasitemia. Mice treated with chloroquine at 5 mg/kg survived during the experiment. The results obtained in this study showed that the infection outcome of P. yoelii yoelii-infected mice is affected by VAM2-6 compound by slowing down the parasite replication, retarding the patency time, and increasing their survival time. Although compound VAM2-6 was active at higher doses than chloroquine, these results leaves a door open to the study of its structure in order to improve its antimalarial activity.

Large-scale solvent-free chlorination of hydroxy-pyrimidines, -pyridines, -pyrazines and -amides using equimolar POCl₃

Chlorination with equimolar POCl₃ can be efficiently achieved not only for hydroxypyrimidines, but also for many other substrates such as 2-hydroxy-pyridines, -quinoxalines, or even -amides. The procedure is solvent-free and involves heating in a sealed reactor at high temperatures using one equivalent of pyridine as base. It is suitable for large scale (multigram) batch preparations.

A novel route to synthesize libraries of quinoxalines via Petasis methodology in two synthetic operations

This communication reveals an innovative and facile procedure to prepare quinoxalines in two synthetic steps. The microwave assisted Petasis reaction is followed by the acid mediated unmasking of an internal amino nucleophile, cyclodehydration and oxidation to give collections of quinoxalines in good to excellent yields.

Structure and vibrational frequencies of 6,7-dimethoxy-1,4-dihydro-1,3-quinoxalinedione based on density functional theory calculations: The role of pi-electron conjugation and back-donation

This work deals with the vibrational spectroscopy of 6,7-dimethoxy-1,4-dihydro-1,3-quinoxalinedione by means of quantum chemical calculations. The mid and far FT-IR and FT-Raman spectra are recorded in the condensed State. The fundamental vibrational frequencies and intensity of vibrational bands are evaluated using density functional theory (DFT) with the standard B3LYP/6-31G* method and basis set combination and is scaled using various scale factors which yields a good agreement between observed and calculated frequencies. The vibrational spectrum is interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results of the calculations are applied to simulate infrared and Raman spectra of the title compounds, which showed excellent agreement with the observed spectra. The infrared unscaled frequencies and intensities are used to disentangle the role played by back-donation in the title compound. For this purpose five other molecules are considered as references: ethane, dimethyl ether, anisole, p-nitro-anisole, and p-hydroxyanisole, in which back-donation has already been ascertained also experimentally. From the study of infrared intensities it is shown that no back-donation of electrons from the oxygen lone pairs takes place, independently of the conformation of the methoxy-group.

Synthesis and Antimicrobial Activity of Some New Quinoxaline Derivatives

2-Chloro-3-methylquinoxaline was selected as a nucleus around which various molecular transformations were performed to obtain new compounds expected to possess optimized antimicrobial activity. As very little work regarding attachment of ether linkages replacing chlorine at C-2 has been reported, it was thought worthwhile to synthesize various quinoxaline derivatives by replacing the C₂ chlorine with an ether linkage attached to a benzene ring possessing an aldehyde or a free amino group which can be further reacted with aromatic amines and aromatic aldehydes, respectively, to yield new Schiff bases containing quinoxaline moieties. Thus the compounds 4-(2-methylquinoxalinyloxy) benzaldehyde (4), 2-[4-(substituted-benziminomethyl)-phenoxy]-3-methyl quinoxalines 5a-e, 4-(2-methyl-quinoxaline-3-yloxy)benzamine (6) and 4-(2-methylquinoxalin-3-yloxy)-N-substituted benzylidine benzamines 7a-e were synthesized and tested for their antimicrobial activity. The structures of the compounds were confirmed on the basis of their elemental and spectral data.

Synthesis and Antimicrobial Activity of Some New Quinoxaline Derivatives

2-Chloro-3-methylquinoxaline was selected as a nucleus around which various molecular transformations were performed to obtain new compounds expected to possess optimized antimicrobial activity. As very little work regarding attachment of ether linkages replacing chlorine at C-2 has been reported, it was thought worthwhile to synthesize various quinoxaline derivatives by replacing the C₂ chlorine with an ether linkage attached to a benzene ring possessing an aldehyde or a free amino group which can be further reacted with aromatic amines and aromatic aldehydes, respectively, to yield new Schiff bases containing quinoxaline moieties. Thus the compounds 4-(2-methylquinoxalinyloxy) benzaldehyde (4), 2-[4-(substituted-benziminomethyl)-phenoxy]-3-methyl quinoxalines 5a–e, 4-(2-methyl-quinoxaline-3-yloxy)benzamine (6) and 4-(2-methylquinoxalin-3-yloxy)-N-substituted benzylidine benzamines 7a–e were synthesized and tested for their antimicrobial activity. The structures of the compounds were confirmed on the basis of their elemental and spectral data.

Anti-leishmanial and structure-activity relationship of ring substituted 3-phenyl-1-(1,4-di-N-oxide quinoxalin-2-yl)-2-propen-1-one derivatives

A series of ring substituted 3-phenyl-1-(1,4-di-N-oxide quinoxalin-2-yl)-2-propen-1-one derivatives were synthesized and tested for in vitro leishmanicidal activity against amastigotes of Leishmania amazonensis in axenical cultures and murine infected macrophages. Structure-activity relationships demonstrated the importance of a radical methoxy at position R3', R4' and R5'. (2E)-3-(3,4,5-trimethoxy-phenyl)-1-(3,6,7-trimethyl-1,4-dioxy-quinoxalin-2-yl)-propenone was the most active. Cytotoxicity on macrophages revealed that this product was almost six times more active than toxic.

2-Chloroquinoxaline

In the title compound, C₈H₅ClN₂, the planar mol­ecules are arranged with their Cl atoms in close contact [Cl⋯Cl = 3.808 (1) and 3.881 (1) Å], indicating weak Cl⋯Cl inter­actions, which give rise to a supra­molecular chain.

Antiplasmodial structure–activity relationship of 3-trifluoromethyl-2-arylcarbonylquinoxaline 1,4-di-N-oxide derivatives

Derivatives of 3-trifluoromethyl-2-arylcarbonylquinoxaline 1,4-di-N-oxide (4b-g, 5b-g, 6a-g) were synthesized and evaluated for their capacity to inhibit the growth of chloroquine-resistant Plasmodium falciparum FCB1 strain in culture. Compound 7-chloro-2-(2-furylcarbonyl)-3-trifluoromethyl-1,4-quinoxaline di-N-oxide (5g) was the most active being almost 5 times more active than chloroquine. It was also 50 times more active against P. falciparum than toxic toward MCF7 cells. Structural characteristics for a quinoxaline to be active were defined: bioisosteric modification of phenyl group by 2-thienyl or 2-furyl subunits, R2 position must be free or occupied by a methyl group and R1 position must be free or occupied by Cl, CH3, OCH3 or CF3.