Application of [Co(Corrole)]- Complexes in Ring-Closing C-H Amination of Aliphatic Azides via Nitrene Radical Intermediates: 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 ringclosing C-H amination of an aliphatic azide in the presence of Boc(2)O (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.