Iron-Catalyzed Direct Olefin Diazidation via Peroxyester Activation Promoted by Nitrogen-Based Ligands

We herein report an iron-catalyzed
direct diazidation method via activation of bench-stable peroxyesters
promoted by nitrogen-based ligands. This method is effective for a
broad range of olefins and N-heterocycles, including
those that are difficult substrates for the existing olefin diamination
and diazidation methods. Notably, nearly a stoichiometric amount of
oxidant and TMSN3 are sufficient for high-yielding diazidation
for most substrates. Preliminary mechanistic studies elucidated the
similarities and differences between this method and the benziodoxole-based
olefin diazidation method previously developed by us. This method
effectively addresses the limitations of the existing olefin diazidation
methods. Most notably, previously problematic nonproductive oxidant
decomposition can be minimized. Furthermore, X-ray crystallographic
studies suggest that an iron–azide–ligand complex can
be generated in situ from an iron acetate precatalyst and that it
may facilitate peroxyester activation and the rate-determining C–N3 bond formation during diazidation of unstrained olefins.