Quinoxalines, also called as 1,4-Benzodiazine, are a class of important aromatic benzopyrazines heterocyclic compounds. Lots of quinoxaline derivatives have anticancer and antibacterial activities. There are many other quinoxaline-based derivatives that have been shown to be effective in clinical trials. Some functional quinoxaline-based derivatives are expected to be used as organic semiconductors, chemical switches and supramolecular receptors. Quinoxaline can be aggregated into polymer, aromatic heterocyclic polymer with high heat resistance, plastic, high strength and corrosion resistance and other excellent features. For quinoxaline with phenyl, the introduction of phenyl can significantly improve the thermal stability of the polymer. Quinoxaline derivatives can also be used for synthetic dyes. Due to the wide application of quinoxalin derivatives in medicine, pesticide and dye, the synthesis of quinoxalin derivatives has attracted much attention.
Several synthesis methods of quinoxaline derivatives have been reported in recent decades:
Quinoxalines are widely used in medicine because of their biological activities such as antiviral, antibacterial and anti-inflammatory, anticancer and insect repellent. Among them, XK469 is the topoisomerase (Topo)Ⅱβ inhibitor anti-tumor drug that developed by Dupont, which can positively regulate the level of TopoⅡα and enhance the cytotoxicity mediated by TopoⅡα. XK469 is less toxic than other anticancer drugs.
Quinoxalines are also widely used in pesticides because of their antifungal, weeding, insecticidal and other biological activities. Qulzalofog-P-ethyl is a post-shoot selective herbicide developed by Japanese chemical industry, showing strong dieback efficacy against one-year and perennial gramineous weeds and safe for broad-leaved crops. It can be widely used in the control of grass weeds in soybean, rape, peanut, cotton and other broad-leaved crops.
Quinoxalines, as fluorescent probes, are mainly used in the detection of metal cations, anions, biological proteins, acidity and viscosity. In the detection of zinc ions, the structure quinoxaline is regarded as fluorescent chromophore, but quinoxaline ring does not participate in coordination. Therefore, taking nitrogen atom of quinoxaline-ring as the ligand site of the recognition group is a development direction of quinoxaline-ring probe design. The simple synthesis method and good modifiability of quinoxalines also provide convenience for the design and synthesis of such probes.