Brönsted acid hydrotrope combined catalyst for environmentally benign synthesis of quinoxalines and pyrido[2,3-b]pyrazines in aqueous medium

An overview of quinoxaline synthesis by green methods: recent reports

Quinoxalines and their derivatives belong to an important class of bicyclic aromatic heterocyclic system, also known as benzopyrazines, containing a benzene ring and a pyrazine ring. They have attracted considerable attention over the years due to their potential biological and pharmaceutical properties. A wide range of synthetic strategies is reported in this significant area of research. The present review showcases recent research advances in the synthesis of quinoxaline derivatives following environmentally benign approaches.

Effective Singlet Oxygen Sensitizers Based on the Phenazine Skeleton as Efficient Light Absorbers in Dye Photoinitiating Systems for Radical Polymerization of Acrylates

A series of dyes based on the phenazine skeleton were synthesized. They differed in the number of conjugated double bonds, the arrangement of aromatic rings (linear and/or angular system), as well as the number and position of nitrogen atoms in the molecule. These compounds were investigated as potential singlet oxygen sensitizers and visible light absorbers in dye photoinitiating systems for radical polymerization. The quantum yield of the singlet oxygen formation was determined by the comparative method based on the 1H NMR spectra recorded for the tested dyes in the presence of 2,3-diphenyl-p-dioxene before and after irradiation. The quantum yield of the triplet state formation was estimated based on the transient absorption spectra recorded using the nanosecond flash photolysis technique. The effectiveness of the dye photoinitiating system was characterized by the initial rate of trimethylolpropane triacrylate (TMPTA) polymerization. In the investigated photoinitiating systems, the sensitizer was an electron acceptor, whereas the co-initiator was an electron donor. The effectiveness of TMPTA photoinitiated polymerization clearly depended on the arrangement of aromatic rings and the number of nitrogen atoms in the modified phenazine structure as well as the quantum yield of the triplet state formation of the photosensitizer in the visible light region.

Recent advancement in the synthesis of diverse spiro-indeno[1,2-b]quinoxalines: a review

The nitrogen-containing indeno[1,2-b]quinoxaline ring is a privileged structurally fused active system and has notable applications in various fields of chemistry.

Concentrated Aqueous Sodium Tosylate as Green Medium for Alkene Oxidation and Nucleophilic Substitution Reactions

A hydrotropic solution of highly concentrated sodium tosylate (NaOTs) can be used as a recyclable medium for the environmentally benign oxidation of conjugated alkenes with H₂O₂. Both uncatalyzed and metal-catalyzed reactions provided the corresponding oxidation products in higher yields than in pure water or many common organic solvents.

One-step approach for the synthesis of functionalized quinoxalines mediated by T3P®–DMSO or T3P® via a tandem oxidation–condensation or condensation reaction

An easy and efficient (T3P®)–DMSO or T3P® mediated oxidation–condensation or condensation reaction for the synthesis of quinoxalines from the different arrays of condensing partners and ortho-phenylene diamines (o-PDs) in one step has been reported.

Aqueous extract of Balanites roxburghii fruit: a green dispersant for C–C bond formation

A natural dispersant exhibiting recyclable buffer property is obtained from aqueous extract ofBalanites roxburghiifruit and used as a highly efficient catalytic medium for C–C bond constructionviaKnoevenagel condensation and tandem Knoevenagel–Michael reaction.