Abstract: The unexpected fundamental influence of an iodine substituent on radical addition to C═C bonds was discovered. The iodine atom demonstrates a strong deactivating effect on the adjacent C═C bond, which is confirmed by DFT calculations and experimental data for reactions between C-, N-, S-, P-, and O-centered radicals and vinyl iodides. When the radical addition does occur, two outcomes are possible: (i) formal iodine substitution, observed when radical addition introduces an electron-withdrawing group (e.g., nitro and sulfonyl) that deactivates the alkene and prevents further addition, or (ii) a second radical addition, when the introduced group does not deactivate the C═C bond. The latter reactivity mode has been demonstrated for azide and imide-N-oxyl radicals. Although imide-N-oxyl radicals are among the least reactive in the tested radical set, as judged by the free energy barriers for addition to C═C bonds, they demonstrate outstanding efficiency in a cascade of addition, iodine elimination, second addition, and iodine re-addition, furnishing gem-bishydroxylamines, compounds that are difficult to access by other methods. Presumably, the persistent nature of imide-N-oxyl radicals is responsible for the unexpected success of this transformation. The cost-effective ωB97X-3c DFT method was shown to correctly predict relative reactivities of styrene derivatives in addition reactions with imide-N-oxyl radicals and to explain the observed selectivity.

Cite: Lopat'eva E.R. , Krylov I.B. , Lapshin D.A. , Novikov R.A. , Terent'ev A.O.
Unexpected dramatic impact of an iodine atom on CC bond radical functionalization: strong deactivating effect, superior efficiency of imide- N -oxyl radicals, iodine elimination and re-addition
Organic Chemistry Frontiers. 2026. DOI: 10.1039/d6qo01062h WOS OpenAlex

Dates:

Submitted:	Jul 28, 2026
Published print:	Sep 1, 2026

Identifiers:

≡ Web of science:	WOS:001869224200001
≡ OpenAlex:	W7204997009

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