The selective successive addition
of azide (•N3) and N-oxyl radicals
to alkenes is demonstrated,
despite each of the two radicals being known to attack CC
bonds and the mixture of radical adducts possibly being expected.
The proposed radical mechanism was supported by density functional
theory calculations, electron paramagnetic resonance, and radical
trapping experiments. The reaction proceeds at room temperature with
the available reagents: NaN3, N-hydroxy
compounds, and PhI(OAc)2 as the oxidant. The method can
be applied for N-hydroxyimides, N-hydroxyamides, N-hydroxybenzotriazole, and oximes
as N-oxyl radical precursors. Vinylarenes, aliphatic
alkenes, and even electron-deficient methyl methacrylate were successfully
functionalized.