Metal-free generation of halogen radicals using NXS/TBHP: Application in site-selective halogenation of quinoxalin-2(1H)-ones and synthesis of gem-dihaloketones

Abstract

Here we report an efficient and practical protocol for the generation of halo radicals (Br and Cl) using inexpensive and readily available NXS/TBHP reagent system at rt. The halo radicals were further utilized for the site-selective C-H bromination and chlorination of the unexplored benzo-core of quinoxalinones. This protocol offers excellent regioselectivity towards C7 position of benzo-core over readily functionalized C3 position in hetero-core of quinoxalinones under mild reaction conditions. Notably, this transformation showed good functional group compatibility and a wide substrate scope. Further, selective synthesis of gem-dihaloketones from alkynes has been accomplished using the same reagent system.