| Autor: |
English LE; Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. d.j.liptrot@bath.ac.uk.; Centre for Sustainable and Circular Technologies, Bath, BA2 7AY, UK., Horsley Downie TM; Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. d.j.liptrot@bath.ac.uk., Lyall CL; Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. d.j.liptrot@bath.ac.uk., Mahon MF; Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. d.j.liptrot@bath.ac.uk., McMullin CL; Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. d.j.liptrot@bath.ac.uk., Neale SE; Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. d.j.liptrot@bath.ac.uk., Saunders CM; Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. d.j.liptrot@bath.ac.uk., Liptrot DJ; Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. d.j.liptrot@bath.ac.uk. |
| Abstrakt: |
The (IPr)CuO t Bu 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-C 6 H 4 NCO, 4-F 3 C-C 6 H 4 NCO, 3-O 2 N-C 6 H 4 NCO). 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-C 6 H 4 NCO, however, the barrier height for the first step of over-reduction is much lower, even relative to [(IPr)CuH]2, resulting in unselective reduction. |
