Selective hydroboration of electron-rich isocyanates by an NHC-copper(i) alkoxide

Laura E. English, Thomas M. Horsley Downie, Catherine L. Lyall, Mary F. Mahon, Claire L. McMullin, Samuel E. Neale, Carla M. Saunders, David J. Liptrot

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8 Citations (Scopus)
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The (IPr)CuOtBu catalysed reduction of 11 aryl and alkyl isocyanates with pinacolborane gave only the boraformamides, pinBN(R)C(O)H, in most cases. Overreduction, which hampers almost all isocyanate hydroborations, was restricted to electron poor aryl isocyanates (4-NC-C6H4NCO, 4-F3C-C6H4NCO, 3-O2N-C6H4NCO). Computational analysis showed stability of [(IPr)CuH]2, which was proposed to be the catalyst resting state, drives selectivity, suggesting an approach to prevent overreduction in future work. In the case of iPrNCO, formation of this species renders overreduction kinetically inaccessible. For 4-NC-C6H4NCO, however, the barrier height for the first step of over-reduction is much lower, even relative to [(IPr)CuH]2, resulting in unselective reduction.
Original languageEnglish
Pages (from-to)1074-1077
Number of pages4
JournalChemical Communications
Issue number8
Early online date26 Dec 2022
Publication statusPublished - 31 Jan 2023


  • catalytic reduction
  • formamide derivatives
  • chemoselective transformations


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