Search

In this study, we explored the use of Mes‐Acr‐MeClO4 as a visible light photocatalyst for multicomponent reactions involving quinoxalin‐2(1H)‐ones with CBrCl3 and styrene. The method showcases regioselective functionalization of quinoxalin‐2(1H)‐ones in a three‐component system, forming two C─C bonds in one pot. Mechanistic investigations suggest a radical‐mediated pathway, initiated by the photoexcitation of Mes‐Acr‐MeClO4, followed by halogen atom abstraction from CBrCl3. This approach provides a versatile and sustainable route for quinoxalin‐2(1H)‐one functionalization, with Mes‐Acr‐MeClO4 effectively facilitating the photocatalyzed multicomponent reaction under mild conditions and visible light irradiation, yielding high selectivity and efficiency. [ABSTRACT FROM AUTHOR]

We herein disclose a direct and practical photocatalytic three‐component α‐trifluoroalkyl‐β‐heteroarylation of various unactivated alkenes with trifluoroacetates and quinoxalin‐2(1H)‐ones. The reaction takes place via a photoinduced LMCT process, allowing efficient synthesis of a variety of 3‐fluoroalkylated quinoxalin‐2(1H)‐one derivatives in moderate to excellent yields under mild reaction conditions. [ABSTRACT FROM AUTHOR]

A catalyst free oxone mediated synthesizing N-alkyl 1, 4-dihydroquinoxaline-2,3-dione has been developed by oxidation of the N-alkyl quinoxalin-2(1H)-one. The developed method is a novel, safest, cost-effective, industrially viable method and applicable for N-substituted and without substitution of 1,4-dihydroquinoxaline-2,3-dione. Consequently, the process is applicable to a broad spectrum of functionality. The reaction can be performed in all organic solvents without any further heating with an extended time and without generating side products. This novel synthetic methodology using Oxone is believed to be the shortest and most efficient to prepare various key intermediates which can be used for further derivatization to make the different biologically active molecules, the key feature of this methodology is not solvent specific, all organic solvents giving the optimum purity and quality using the same reaction condition. [ABSTRACT FROM AUTHOR]

We demonstrate a photocatalyst and transition metal catalyst free photo‐activation of quinoxalin‐2(1H)‐ones in visible light in the presence of an acid catalyst. The photoactivated quinoxalin‐2(1H)‐one species transfers its energy to oxygen which promotes C−N cross dehydrogenative coupling with nucleophilic partners such as carbazoles, azoles and amides giving the products in 42–75% yields. Preliminary studies reveal quinoxalin‐2(1H)‐one‐carbazole adducts to display fluorescent properties including Intramolecular Charge Transfer (ICT) and Aggregate Induced Emission (AIE). [ABSTRACT FROM AUTHOR]

Quinoxalin-2(1H)-one, Katritzky salt, deaminative alkylation, electron catalysis, radical cascade R. Torviso, D. Mansilla, S. Garcia, B. Lantanõ, S. Barata-Vallejo, A. Postigo, J. Fluorine Chem. 2017, 197, 42 - 48. 54 Y. Cheng, C. Mück-Lichtenfeld, A. Studer, J. Am. Chem. Soc. 2018, 140, 6221 - 6225; 55 J. Wu, L. He, A. Noble, V. K. Aggarwal, J. Am. Chem. Soc. 2018, 140, 10700 - 10704; 56 L. Zhang, L. Jiao, Chem. Sci. 2018, 9, 2711 - 2722. Very recently, Adiyala and co-workers reported a C3 alkylation reaction of quinoxalin-2(1 I H i )-ones with Katritzky salts, however a photocatalyst was still required.[68] Herein, we disclose a simple and efficient deaminative C3 alkylation of quinoxalin-2(1 I H i )-ones with Katritzky salts, which enables the metal- and photocatalyst-free synthesis of 3-alkylated quinoxalin-2(1 I H i )-ones (Scheme 1c). Keywords: deaminative alkylation; quinoxalin-2(1H)-one; Katritzky salt; electron catalysis; radical cascade EN deaminative alkylation quinoxalin-2(1H)-one Katritzky salt electron catalysis radical cascade 865 870 6 03/27/23 20230321 NES 230321 A visible-light initiated deaminative C3 alkylation of quinoxalin-2(1 I H i )-ones with Katritzky salts is reported. [Extracted from the article]

Barium chloride embedded polyaniline (Ba/PANI) nanocomposite has been utilized as a heterogeneous nanaocatalyst towards synthesis of biologically active styrylquinoxalin-2(1H)-ones in excellent yields. The results showed that Ba/PANI nanocatalyst offered notably higher catalytic activity compared to both BaCl2 and PANI and was easily recoverable and reusable. The synthesized barium containing nanocomposite has been characterized by XRD, FTIR, SEM, HR-TEM, EDX, ICP-MS, UV–Vis, TGA, N2 adsorption–desorption isotherms (BET), and XPS techniques. TEM analysis confirmed the average grain size of BaCl2 nanoparticles in the composite to be 13–14 nm. BET analysis affirmed mesoporous structure of Ba/PANI nanocomposite which played an important role in its catalytic efficiency. Both XRD and HRTEM findings disclosed polycrystalline nature of the nanocomposite. ICP-MS analysis confirmed 22.51 wt% of Ba loaded on PANI. [ABSTRACT FROM AUTHOR]

Photophysical properties of quinoxalin‐2(1H)‐ones have long been neglected, in particular compared with those of coumarins, their oxygenated counterparts, despite their complementarity in terms of absorbance and fluorescence windows. This review provides first an overview of the synthesis of quinoxalin‐2(1H)‐ones, focusing on the most recent contributions. Fluorescence properties of quinoxalin‐2(1H)‐ones and of their π‐extended derivatives are tackled through the description of a series of examples and applications, including chemosensing and biosensing. [ABSTRACT FROM AUTHOR]

Auto‐oxidation of aliphatic aldehydes generates alkyl radicals and alkanoyl radicals, which can be intercepted to generate carbon‐carbon bonds. However, the highly reactive and unstable radical intermediates make the controlling selectivity alkylation and alkanoacylation especially challenging. Herein, we report a sustainable and controllable protocol for the auto‐oxidative alkylation and alkanoacylation of quinoxalin‐2(1H)‐ones with good reactivity and selectivity. This protocol was presented in a green and sustainable manner, using oxygen as the only oxidant, avoiding the use of catalysts and explosive oxidants. It offers a new paradigm for a convenient, green synthesis of alkyl and alkanoyl compounds from abundant aliphatic aldehydes. [ABSTRACT FROM AUTHOR]

A simple method has been developed for the synthesis of ­3-(2-oxo-2-phenylethylidene)-3,4-dihydroquinoxalin-2(1H)-one and ­3-aryl-quinoxalin-2(1H)-one derivatives through C–H activation of quinoxalin-2(1H)-ones by peroxides and iodide. In this protocol, the per­oxide (TBPB) serves as both the radical initiator and aryl source, realizing arylation of quinoxalin-2(1H)-one in a one-step reaction. The methodology has the advantages of being a metal-free strategy and having broad functional group tolerance.

Abstract A metal-catalyst-free synthesis of substituted quinoxalin-2-ones from 2,2-dibromo-1-arylethanone by employing an oxidative amidation–heterocycloannulation protocol is reported. The substrate scope of the reaction has been demonstrated and a possible mechanism for this reaction has also been proposed.

The cross-dehydrogenative coupling (CDC) reaction of ß-ketoesters with quinoxalin-2(1H)-one derivatives has been successfully performed by using a readily available Cu salt as the catalyst in moderate to excellent yields under mild conditions. Owing to the characteristic of handy operation and good functional group tolerance, this protocol affords a convenient access to α-quinoxalinone-substituted ß-ketoesters. Preliminary mechanistic investigations show this transformation possibly underwent an unusual ionic pathway. [ABSTRACT FROM AUTHOR]

The modification of quinoxalin-2(1H)-ones via direct C-H bond functionalization has begun to receive widespread attention, due to quinoxalin-2(1H)-one derivatives' various biological activities and pharmaceutical properties. This mini review concentrates on the accomplishments of arylation, trifluoromethylation, alkylation, and alkoxylation of quinoxalin-2(1H)-ones with hypervalent iodine(III) reagents as reaction partners or oxidants. The reaction conditions and mechanisms are compared and discussed in detail.

• Photoinduced Rapid Chloropropylation of Quinoxalin-2(1H)-Ones with Cyclopropane and HCl. • SAS was used as the photocatalyst, HCl was used as the chlorine source. • This synthetic method provides a green and efficient way to realize the chloropropylation of quinoxalin-2(1H)-ones and afford a series of chlorinated quinoxalin-2(1H)-one derivatives in good to excellent yields with a high functional group tolerance and a broad substrate scope. Herein, a photoinduced three-component reaction of aryl cyclopropane, quinoxalin-2(1H)-ones and HCl has been developed to introduce chloroalkyl motifs into N -heteroarenes. This synthetic method provides a green and efficient way to realize the chloropropylation of quinoxalin-2(1H)-ones and afford a series of chlorinated quinoxalin-2(1H)-one derivatives in moderate to good yields with the broad functional-group tolerance. [Display omitted] [ABSTRACT FROM AUTHOR]

A metal‐free domino multicomponent reaction for the direct C−H benzylation and alkylation of quinoxalin‐2(1H)‐ones using alkenes is described. Triggered by the sulfonyl radical generated from sulfinic acid, the alkenes are transformed to alkyl radicals that react exclusively at the C‐3 position of quinoxalin‐2(1H)‐ones. Importantly, the method not only functionalizes medicinally important quinoxalin‐2(1H)‐one scaffold, but also furnishes diverse medicinally relevant sulfones in good to excellent yields under mild conditions. [ABSTRACT FROM AUTHOR]

A practical protocol for the preparation of quinoxaline‐2,3(1H,4H)‐diones through direct C(sp2)−H hydroxylation of quinoxalin‐2(1H)‐ones in recyclable DL‐α‐Tocopherol methoxypolyethylene glycol succinate solution (2 wt% in water) (TPGS‐750‐M/H2O) was developed. The target products were exclusively generated and could be collected through extraction and recrystallization. [ABSTRACT FROM AUTHOR]

An efficient and simple protocol for Selectfluor‐mediated phosphonation of quinoxalin‐2(1H)‐ones with dialkyl H‐phosphonates has been developed under base and transition‐metal free conditions, affording the desired 3‐phosphorylated quinoxalin‐2(1H)‐ones in good to excellent yields. This method has the advatages of broad substrate scope, general functional groups compatibility, and mild reaction conditions. [ABSTRACT FROM AUTHOR]

A convenient and efficient protocol for the synthesis of thetetrazolo[1,5‐a]quinoxalin‐4(5H)‐ones via copper‐catalyzed [3+2] cyclization of azidotrimethylsilane with quinoxalin‐2(1H)‐ones under mild conditions has been disclosed. This practical protocol is compatible with a variety of functional groups and provides an access to functionalized tetrazolo[1,5‐a]quinoxalin‐4(5H)‐ones from readily available and safe starting materials. [ABSTRACT FROM AUTHOR]

Quinoxalin-2(1H)-one and its derived 3-Benzylquinoxalin-2(1H)-one were synthesized and characterized by UV-visible spectroscopy. The changes displayed by the photophysical properties of these molecules in different solvents can be explained in terms of a sum of dielectric polarity and hydrogen bonding effects taking part in the stabilisation of the structure. 3-Benzylquinoxalin-2(1H)-one exhibits two fluorescence emission bands ( F and F ) in very polar solvents and one band ( F ) in low polar solvents. These bands are assigned on the basis of the absorption and emission solvent effect. The abnormal fluorescence ( F ) observed in very polar solvents is attributed to an intermolecular interaction between solute and solvent molecules in the excited state (exciplex formation). [ABSTRACT FROM AUTHOR]

With the increasing antibiotic resistance of bacterial strains, alternative methods for infection control are in high demand. Quorum sensing (QS) is the bacterial communication system based on small molecules. QS is enables bacterial biofilm formation and pathogenic development. The interruption of QS has become a target for drug discovery, but remains in the early experimental phase. In this study, we synthesized a set of six compounds based on a scaffold (alkyl-quinoxalin-2(1H)-one), new in the anti-QS of Gram-negative bacteria Aeromonas caviae Sch3. By quantifying biofilm formation, we were able to monitor the effect of these compounds from concentrations of 1 to 100 µM. Significant reduction in biofilm formation was achieved by 3-hexylylquinoxalin-2(1H)-one (11), 3-hexylylquinoxalin-2(1H)-one-6-carboxylic acid (12), and 3-heptylylquinoxalin-2(1H)-one-6-carboxylic acid (14), ranging from 11% to 59% inhibition of the biofilm. This pilot study contributes to the development of anti-QS compounds to overcome the clinical challenge of resistant bacteria strains.

[Display omitted] A F reagent-mediated direct C-H carbamoylation of quinoxalin-2(1 H)-ones has been developed. Under room temperature, a variety of isocyanides are employed to couple well with quinoxalin-2(1 H)-ones affording 42 examples including 30 new compounds. This metal-free mild strategy tolerates a wide range of functional groups and shows environmental friendliness and practicality. [ABSTRACT FROM AUTHOR]

The first C3 α -aminoalkylation of quinoxalin-2(1H)-ones with amines under mild conditions. [Display omitted] An efficient method was developed for the synthesis of various C3 α -aminoalkylated quinoxalin-2(1 H)-ones via Cross-Dehydrogenative Coupling under transition-metal-free conditions, affording the target products with a broad substrate scope in moderate to good yields. [ABSTRACT FROM AUTHOR]

[Display omitted] • Visible light promoted eosin Y catalyzed selective C3-H acylation of quinoxalin-2(1H)-ones. • Neutral eosin Y as the actual hydrogen-atom transfer catalyst in a green and sustainable manner. • Readily available aldehyde as the radical precursor for the generation of acyl radical. Visible light promoted eosin Y catalyzed selective C3-H acylation of quinoxalin-2(1H)-ones has been developed in a green and sustainable manner. In contrast to the conventional anionic eosin Y-based photoredox process, neutral eosin Y acts as the actual catalyst, which was responsible for the hydrogen-atom transfer (HAT) process to generate the acyl radical with readily available aldehydes as the radical precursor. [ABSTRACT FROM AUTHOR]

The modification of quinoxalin-2(1 H )-ones via direct C-H bond functionalization has begun to receive widespread attention, due to quinoxalin-2(1 H )-one derivatives' various biological activities and pharmaceutical properties. This mini review concentrates on the accomplishments of arylation, trifluoromethylation, alkylation, and alkoxylation of quinoxalin-2(1 H )-ones with hypervalent iodine(III) reagents as reaction partners or oxidants. The reaction conditions and mechanisms are compared and discussed in detail., (Copyright © 2020 Tan, Wang, Zhang, Zhang and Zhao.)

With the increasing antibiotic resistance of bacterial strains, alternative methods for infection control are in high demand. Quorum sensing (QS) is the bacterial communication system based on small molecules. QS is enables bacterial biofilm formation and pathogenic development. The interruption of QS has become a target for drug discovery, but remains in the early experimental phase. In this study, we synthesized a set of six compounds based on a scaffold (alkyl-quinoxalin-2(1 H )-one), new in the anti-QS of Gram-negative bacteria Aeromonas caviae Sch3. By quantifying biofilm formation, we were able to monitor the effect of these compounds from concentrations of 1 to 100 µM. Significant reduction in biofilm formation was achieved by 3-hexylylquinoxalin-2(1 H )-one ( 11 ), 3-hexylylquinoxalin-2(1 H )-one-6-carboxylic acid ( 12 ), and 3-heptylylquinoxalin-2(1 H )-one-6-carboxylic acid ( 14 ), ranging from 11% to 59% inhibition of the biofilm. This pilot study contributes to the development of anti-QS compounds to overcome the clinical challenge of resistant bacteria strains.

In this investigation, we searched for novel MAO-A inhibitors using a 3-benzylquinoxaline scaffold based on our earlier findings. Series of N'-(3-benzylquinoxalin-2-yl)acetohydrazide, 4a, N'-(3-benzylquinoxalin-2-yl)benzohydrazide derivatives 4b-f, N'-[2-(3-benzyl-2-oxoquinoxalin-1(2H)-yl)acetyl]benzohydrazide derivatives 7a-d, (9H-fluoren-9-yl)methyl 1-[2-(2-(3-benzyl-2-oxoquinoxalin-1(2H)-yl)acetyl)-hydrazinyl]-2-ylcarbamate derivatives 8a-c, 2-(3-benzyl-2-oxoquinoxalin-1(2H)-yl)-N'-benzylidene acetohydrazide derivatives 9a-h, and ethyl 2-(3-benzyl-2-oxoquinoxalin-1(2H)-yl)acetate derivatives 10a-e were synthesized and evaluated in vitro as inhibitors of the two monoamine oxidase isoforms, MAO-A and MAO-B. Most of the compounds showed a selective MAO-A inhibitory activity in the nanomolar or low micromolar range. Compounds 4e and 9g were the most potent derivatives with high MAO-A selectivity and their molecular docking studies were performed in order to rationalize the obtained biological result., (Copyright © 2015 Elsevier Masson SAS. All rights reserved.)