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.

Unexpected regio- and stereoselective [4 + 3] cycloaddition reaction of azomethine ylides with benzylidene thiazolidinediones: synthesis of pharmacologically active spiroindoline oxazepine derivatives and theoretical study

An unexpected regio- and stereoselective [4 + 3] cycloaddition reaction of azomethine ylides with 5-benzylidenethiazolidine-2,4-diones has been successfully developed for the synthesis of the novel pharmacologically active 4',5'-dihydro-3'H-spiro[indoline-3,2'-[1, 3] oxazepin]-2-one derivatives in basic condition. Easy purification, high yield, short experimental time and operational simplicity are specific advantages of this protocol. Furthermore, all the synthesized compounds have been evaluated for antioxidant and antibacterial activities. According to the results, most of the synthesized compounds exhibited DPPH radical scavenging activity and nine of them showed antibacterial properties. The reaction mechanism and ¹H NMR spectrum have been evaluated by B3LYP/6311G method.

A One-Pot Synthesis of Oxazepine-Quinazolinone bis-Heterocyclic Scaffolds via Isocyanide-Based Three-Component Reactions

A novel, efficient and environmentally friendly approach has been developed for the synthesis of biologically important bis-heterocyclic oxazepine-quinazolinone derivatives. The structurally interesting compounds of high purity were synthesized by a one-pot three-component reaction of 2-(2-formylphenoxy) acetic acid and 2-aminobenzamide as bifunctional reagents and an isocyanide without using any catalyst, with excellent overall yields.

Organocatalytic Synthesis of Fused Bicyclic 2,3-Dihydro-1,3,4-oxadiazoles through an Intramolecular Cascade Cyclization

Hydrazone-carboxylic acids undergo intramolecular cyclization in the presence of pivaloyl chloride, iPr(2)NEt, and catalytic DABCO to form a range of substituted fused tricyclic 2,3-dihydro-1,3,4-oxadiazoles in high yields.