Convenient synthesis of 2-chloro-3-substituted quinoxalines by visible-light-induced radical cascade cyclization of ortho-diisocyanoarenes with sulfinic acids

Abstract

2-Chloro-3-substituted quinoxalines (3) are significant precursors in the synthesis of 2,3-di-unsymmetrically substituted quinoxalines, including quinacillin, which has been shown to be effective against a number of transplantable diseases and cancer cells. Despite the fact that there are two ways to produce 2-chloro-3-substituted quinoxalines (3), both procedures are hampered by high temperatures, metal contamination, and toxic reagents. A visible-light-induced radical cascade cyclization of ortho-diisocyanoarenes (1) with alkyl(aryl)sulfinic acids (2) and trichloroisocyanuric acid has been developed. Also, a plausible reaction mechanism and synthetic uses of 2-chloro-3-substituted quinoxalines (3) towards a few 2,3-di-unsymmetrically-substituted quinoxalines have been described. This novel approach easily accesses 2-chloro-3-substituted quinoxalines (3) in good yields, without using elevated temperatures, or metal- or toxic reagents.