C(sp2)–H/O–H cross-dehydrogenative coupling of quinoxalin-2(1H)-ones with alcohols under visible-light photoredox catalysis

Late-stage C-H trifluoroacetylation of quinoxaline-2(1H)-ones using masked trifluoroacyl reagents

A strategy for trifluoroacetylation of quinoxaline-2(1H)-ones has been investigated. This strategy employs masked trifluoroacyl reagents to obtain trifluoroacetylated quinoxaline-2(1H)-ones under metal-, catalyst-, and light-free conditions. This approach is distinguished by its functional group compatibility and tolerance, as well as the simplicity of the experimental process, making it suitable for gram-scale synthesis.

Acid-Promoted Self-Photocatalyzed Regioselective Oxidation: A Novel Strategy for Accessing Quinoxaline-2,3-diones

Disclosed here is an efficient approach for the preparation of quinoxaline-2,3-diones using air (O2) as a green oxidant via acid-promoted self-photocatalyzed regioselective oxidation of quinoxalin-2(1H)-ones at C-3 position. This protocol presents a novel synthetic route for the preparation of quinoxaline-2,3-dione derivatives, featuring mild reaction conditions, simple operation, and a wide range of substrates, without the need for external photocatalysts, metal reagents, and strong oxidants.

Visible light-promoted C3-H alkoxycarbonylation of quinoxalin-2(1H)-ones or coumarins with alkyloxalyl chlorides

Herein, we describe a green and efficient photoredox catalytic C3-H alkoxycarbonylation between quinoxalin-2(1H)-ones or coumarins and readily available alkyloxalyl chlorides under ambient conditions. A series of quinoxaline-3-carbonyl and coumarin-3-carbonyl compounds are prepared through the radical addition of in situ-generated alkoxycarbonyl radicals. Notably, this protocol features mild conditions, operational simplicity, and excellent functional group tolerance. More importantly, the carboxylated products can be readily derivatized into other important compounds that would be of great potential for the exploitation of pharmaceutically active compounds.

Visible-Light-Induced Singlet Oxygen-Promoted Arylation and Alkylation of Quinoxalin-2(1H)-ones and Quinolines

We report a green and efficient visible-light-driven method for the arylation and alkylation of quinoxalin-2(1H)-ones and quinolines. This catalyst-free process utilizes air as the oxidant, offering mild reaction conditions, environmental sustainability, and broad functional group compatibility. The approach enables the synthesis of aryl and alkyl derivatives of quinoxalin-2(1H)-ones and quinolines with high to excellent yields.

Base-Mediated Visible-Light-Driven C-H Arylation of Quinoxalin-2(1H)-Ones in Ethanol

Prior methods for visible-light-driven C-H arylation of quinoxalin-2(1H)-ones relied on external photocatalysts. Herein, we report a photocatalyst-free approach for this arylation. In this approach, β-dicarbonyl iodonium ylides, combined with t-BuOK in ethanol, act as aryl precursors, forming electron donor-acceptor (EDA) complexes. These complexes enhance light absorption, facilitating efficient single electron transfer and aryl radical formation. Consequently, various quinoxalin-2(1H)-ones undergo precise and efficient arylation without external photocatalysts. This protocol exhibits excellent tolerance toward diverse functional groups, with mild reaction conditions and eco-friendly solvents, revealing a high Ecoscale value.

Visible-light-induced tandem reaction of quinoxalin-2(1H)-ones, alkenes, and sulfonyl chlorides

A visible-light-induced tandem reaction involving quinoxalin-2(1H)-ones, alkenes, and sulfonyl chlorides, catalyzed by 4CzIPN, was developed. The utilization of easily accessible sulfonyl chlorides, metal-free conditions, and a wide substrate scope established this protocol as an efficient and alternative method for obtaining sulfonated quinoxalin-2(1H)-ones.

Visible-light-induced three-component reactions of α-diazoesters, quinazolinones and cyclic ethers toward quinazoline-based hybrids

An effective approach for the construction of 4-short-chain ether attached carbonyl group-substituted quinazolines was developed. Visible-light-induced three-component reactions of α-diazoesters, quinazolinones, and cyclic ethers, with a broad substrate scope and excellent functional group tolerance, under extremely mild conditions without the need for any additional additives and catalysts, selectively led to quinazoline-based hybrids in good to excellent yields. The synthesized hybrids, which are a conglomeration of a quinazoline, a short-chain ether, and a carbonyl group in one molecular skeleton, have potential for application in the development of new drugs or drug candidates.

Copper-Catalyzed Difluoroalkylation Reaction

This review describes recent advances in copper-catalyzed difluoroalkylation reactions. The RCF₂ radical is generally proposed in the mechanism of these reactions. At present, various types of copper-catalyzed difluoroalkylation reactions have been realized. According to their characteristics, we classify these difluoroalkylation reactions into three types.

Visible-Light-Initiated Multicomponent Reactions of α-Diazoesters to Access Organophosphorus Compounds

A simple visible-light-initiated strategy has been established for the construction of organophosphorus compounds via aerobic multicomponent reaction of α-diazoesters, cyclic ethers, and P(O)H compounds under air. A number of phosphonates and phosphinates could be efficiently isolated in moderate to good yields without the use of photosensitizers and metal reagents. This multicomponent reaction has advantages of mild condition, simple operation, eco-friendly energy, good functional-group tolerance, and gram-scale synthesis.

Sunlight Induced and Recyclable g-C3N4 Catalyzed C-H Sulfenylation of Quinoxalin-2(1H)-Ones

A sunlight-promoted sulfenylation of quinoxalin-2(1H)-ones using recyclable graphitic carbon nitride (g-C₃N₄) as a heterogeneous photocatalyst was developed. Using the method, various 3-sulfenylated quinoxalin-2(1H)-ones were obtained in good to excellent yields under an ambient air atmosphere. Moreover, the heterogeneous catalyst can be recycled at least six times without significant loss of activity.

A HCl-Mediated, Metal- and Oxidant-Free Photocatalytic Strategy for C3 Arylation of Quinoxalin(on)es with Arylhydrazine

A novel and simple HCl-mediated, photocatalytic method for quinoxaline(on)es C3-H arylation with arylhydrazine under transition metal catalyst- and oxidant-free conditions is presented. Various quinoxaline(on)es underwent this transformation smoothly, demonstrating a broad substrate tolerance and providing the corresponding aryl products in moderate to excellent yields. Mechanistic studies indicated that a radical pathway may be involved in this transformation.

Visible Light Mediated, Catalyst Free, One-Pot Convenient Synthesis of Dihydropyridines

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A simple, efficient and green protocol has been developed for the synthesis of polysubstituted dihydropyridines via one-pot, four-component reaction of aldehydes, arylamines, dialkyl acetylenedicarboxylate, and malononitrile. The reaction was proceeded at room temperature in the absence of catalyst in aqueous ethyl lactate under visible light irradiation. The main advantages of the present approach are mild reaction condition, high yield, no column chromatography, clean reaction profile, environmentally friendly and sustainable from the economic point of view

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.

Visible-Light Photosynthesis of CHF2 /CClF2 /CBrF2 -Substituted Ring-fused Quinazolinones in Dimethyl Carbonate

With eco-friendly and sustainable CO₂ -derived dimethyl carbonate as the sole solvent, the visible-light-induced cascade radical reactions have been established as a green and efficient tool for constructing various CHF₂ /CClF₂ /CBrF₂ -substituted ring-fused quinazolinones.

Metal-free visible-light-induced multi-component reactions of α-diazoesters leading to S-alkyl dithiocarbamates

A metal-free and visible-light-promoted strategy has been developed for the synthesis of S-alkyl dithiocarbamates through multicomponent reactions of α-diazoesters, amines and CS2.

Alkylsulfonium salts for the photochemical desulphurizative functionalization of heteroarenes

A metal-free organic photoredox-catalyzed alkylation of heteroarenes using alkylsulfonium salts as alkylation reagents has been developed.

C–H benzylation of quinoxalin-2(1H)-ones via visible-light riboflavin photocatalysis

An efficient visible light promoted riboflavin-catalyzed direct benzylation of substituted quinoxalin-2(1H)-ones for the synthesis of various C3-benzylated quinoxalin-2(1H)-one derivatives has been developed under mild conditions.

Visible-light-mediated multi-component carbene transfer reactions of α-diazoesters to construct multisubstituted pyrazoles and 1,3-dicarbonyl derivatives

A visible-light-promoted strategy has been developed for the assembly of multisubstituted pyrazoles and 1,3-dicarbonyl derivatives via a multi-component carbene transfer reaction of α-diazoesters.

Metal-free regioselective nitration of quinoxalin-2(1H)-ones with tert-butyl nitrite

A metal-free coupling of quinoxalin-2(1H)-ones with tert-butyl nitrite has been developed. Distinctly from the previous functionalization of quinoxalin-2(1H)-ones, this nitration reaction took place selectively at the C7 or C5 position of the phenyl ring, affording a series of 7-nitro and 5-nitro quinoxalin-2(1H)-ones in moderate to good yields. Preliminary mechanistic studies revealed that the reaction may involve a radical process.

Alkylation of quinoxalin-2(1H)-ones using phosphonium ylides as alkylating reagents

A practical and efficient methodology for the construction of 3-alkylquinoxalinones through base promoted direct alkylation of quinoxalin-2(1H)-ones with phosphonium ylides as alkylating reagents under metal- and oxidant-free conditions was developed. Various 3-alkylquinoxalin-2(1H)-ones were easily obtained in good to excellent yields. Tentative mechanistic studies suggest that this reaction is likely to involve a nucleophilic addition-elimination process.

On-DNA Derivatization of Quinoxalin-2-ones by Visible-Light-Triggered Alkylation with Carboxylic Acids

An efficient visible-light-induced alkylation of DNA-tagged quinoxaline-2-ones was described. The methodology demonstrated moderate-to-excellent conversions under mild conditions. The reaction was found to be tolerant with both N-protected α-amino acids and aliphatic carboxylic acids and could be applied to the synthesis of focused DNA-encoded quinoxalin-2-one libraries.

Metal-Free Direct C-H Functionalization of Quinoxalin-2(1H)-Ones to Produce 3-Vinylated Quinoxalin-2(1H)-Ones in the Presence of Alkenes

A novel and efficient C 3-H vinylation reaction with quinoxalin-2(1H)-one as the substrate, in the presence of alkenes, under metal-free conditions, is reported herein. The reaction leads to the formation of new carbon-carbon bonds that exhibit moderate to good reactivities. The vinylation of quinoxalin-2(1H)-ones, in the presence of alkenes, is an attractive process that can be potentially utilized to produce biologically active 3-vinylated quinoxalin-2(1H)-ones.

Site-specific C–H chalcogenation of quinoxalin-2(1H)-ones enabled by Selectfluor reagent

A site-specific C6–H chalcogenation of quinoxalin-2(1H)-ones with various diselenides and dithiols is presented by employing Selectfluor reagent as an oxidant.