Halogen-Bonding Complexes of Iodonium Ylides for Halogen Atom Transfer: C-H Alkylation of Heterocycles.

Halogen atom transfer (XAT) represents a mild and selective strategy for generating alkyl radicals from alkyl halides, yet it typically relies on photocatalysts or metal complexes as reductants. Accordingly, the development of greener and more efficient strategies for an XAT platform is highly desirable. Herein, a photoactive halogen-bonding (HB) complex has been developed, formed in situ from iodonium ylides and an organic base, to selectively generate aryl radicals as an XAT agent under visible-light or sunlight irradiation. Direct C-H alkylation of heterocycles with a broad range of alkyl iodides was achieved under metal- and photocatalyst-free conditions. Meanwhile, the generated aryl radicals also mediate hydrogen atom transfer (HAT) from simple alkanes as substrates, demonstrating the versatility of this protocol for the generation of diverse alkyl radicals. Remarkably, its practicality and potential application are highlighted by gram-scale synthesis, late-stage modification of drugs, and synthesis of bioactive compounds.