Abstract: N-oxyl radicals occupy an important place in free-radical oxidative CH-functionalization being one of the most efficient redox-organocatalysts for hydrogen atom abstraction (HAT). Their applications include aerobic radical chain autoxidation, CH-functionalization with the formation of carbon-carbon and carbon-heteroatom bonds. The persistent nature of N-oxyl radicals combined with their high reactivity in HAT results in their unique dual chemistry: the same radical can both propagate radical chain reaction (at low N-oxyl concentrations) and effectively “terminate” carbon-centered radicals (at higher N-oxyl concentrations). The latter case opens a new synthetic application area of N-oxyl radicals, in which they act as both hydrogen abstracting species and O-reagents for cross-coupling with carbon-centered radicals thus produced. Apart from the C−H bond cleavage, reactive N-oxyl radicals have been extensively used recently in C=C double bond functionalization via radical addition reactions. In this review, both free-radical CH-functionalization reactions with the introduction of N-oxyl fragments and alkene difunctionalizations by N-oxyls are covered with emphasis on the relationship between reaction conditions and selectivity.

Cite: Lopat'eva E.R. , Krylov I.B. , Yu B. , Terent'ev A.O.
N‐Oxyl Radicals in Oxidative C–O Coupling: Free‐Radical Hydrogen Substitution and Addition to C=C Bonds
Asian Journal of Organic Chemistry. 2025. V.14. N1. e202400503 . DOI: 10.1002/ajoc.202400503 WOS OpenAlex

Identifiers:

Web of science:	WOS:001356928400001
OpenAlex:	W4403542082

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