Application of [Co(Corrole)]^- Complexes in Ring-Closing C-H Amination of Aliphatic Azides via Nitrene Radical Intermediates

The synthesis, characterisation and application of anionic [Co^II(Cor)]^– (Cor = corrole) metalloradicals in the ring‐closing C–H amination of an aliphatic azide in the presence of Boc₂O (Boc = tert‐butyloxycarbonyl) to give the corresponding Boc‐protected N‐heterocyclic product tert‐butyl 2‐phenylpyrrolidine‐1‐carboxylate are reported. This is the first example of the use of metalloradical cobalt(II) corrole complexes in nitrene‐transfer reactions. On the basis of DFT calculations, the reaction is proposed to proceed via discrete open‐shell nitrene radical intermediates bearing most of their spin density at the nitrene nitrogen atom. The [Co^II(Cor)]^– complexes are substantially faster catalysts than the corresponding neutral [Co^II(porphyrin)] complexes when applied in the same ring‐closing C–H amination reaction under identical reaction conditions. Increasing the electron density at cobalt(II) therefore has a positive influence on the reaction rate.