Aziridination of styrenes is examined via anionic MII catalysts (M = Mn, Fe, Co, Ni), supported by trisamido-amine moieties, through a nitrene transfer reaction. We concluded – from experiments and computations – that carboradical intermediates are generated by initial nitrene-addition to one of the olefinic carbons and play a key role in the stepwise C−N bond formation. In the current work, we explore mono-anionic metal sites and demonstrate that attenuated levels of electrophilicity are more suitable for discriminating aromatic from aliphatic olefins for aziridination purposes. In addition, we make use of divalent, first-row transition-metal sites. The high-spin nature of the compounds encountered in the present work gives rise to putative metal-nitrene intermediates possessing more complex electronic structures than the common singlet/triplet manifolds explored with Cu, Ag or Ru nitrenes. In this combined experimental and computational study, we present a family of anionic Mn(II) reagents that offer guidance with regards to ligand selection for effecting olefin aziridination, and subsequently extend to the corresponding Fe(II), Co(II), and Ni(II) reagents to gain insights in their comparative reactivity/selectivity patterns that enable aromatic over aliphatic alkene aziridinations.

Comparative nitrene-transfer chemistry to olefinic substrates mediated by a library of anionic Mn(II) triphenylamido-amine reagents and M(II) congeners (M = Fe, Co, Ni): An experimental and computational study

256th National Meeting (2018)

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