TEMPO-Promoted Pauson-Khand Reaction. Single-Electron Activation of Cobalt-Carbonyl Bonds?

The Pauson-Khand reaction is notably accelerated by TEMPO. According to DFT calculations, TEMPO could trigger a radical, low-energy pathway for the reaction by facilitating the decarbonylation of doublet complexes arising either from a CO/nitroxide exchange or from nitroxide addition to a CO ligand.