Aziridine Group Transfer via Transient <i>N</i>-Aziridinyl Radicals

Aziridines are the smallest nitrogen-containing heterocycles. Strain-enhanced electrophilicity renders aziridines useful synthetic intermediates and gives rise to biological activity. Classical aziridine syntheses─based on either [2 + 1] cycloadditions or intramolecular substitution chemistry─assemble aziridines from acyclic precursors. Here, we introduce <i>N-</i>aziridinyl radicals as a reactive intermediate that enables the transfer of intact aziridine fragments in organic synthesis. Transient <i>N-</i>aziridinyl radicals are generated by the reductive activation of <i>N</i>-pyridinium aziridines and are directly characterized by spin-trapped EPR spectroscopy. In the presence of O₂, <i>N</i>-aziridinyl radicals are added to styrenyl olefins to afford 1,2-hydroxyaziridination products. These results establish aziridinyl radicals as new reactive intermediates in synthetic chemistry and demonstrate aziridine group transfer as a viable synthetic disconnection.