Remote C(sp3)-H heteroarylation of N-fluoroarylsulfonamides via a silyl radical process under visible light irradiation

An efficient method for heteroarylation of unactivated, aliphatic C(sp(3))-H bonds has been developed using a novel, visible light-promoted radical-relay sequence. The overall process likely occurs via hydrogen atom transfer between an in situ generated methoxy radical and a silane Si-H bond. The ensuing silicon-centered radical then abstracts the fluorine from N-fluorosulfonamides to produce N-centered radicals that themselves undergo 1,5-hydrogen atom transfer to furnish carbon-centered radicals. The radical-chain process involves the formation of electron donor-acceptor complexes between electron-deficient N-methoxyheteroarenium salts and the fluoride ion that leads to remote delta-C(sp(3))-H heteroarylation. Certain product structures were confirmed by X-ray analysis using a single, pre-crystalline coating method. Such outcomes provide new insights into radical relay processes as well as access to a range of new molecular scaffolds.