Edwin Van Der Eide - Mechanistic insights into the ruthenium-catalysed diene ring-closing metathesis reaction

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      Publication Details (including relevant citation   information):

      Edwin F. van der Eide and Warren E. Piers

      Nature   Chemistry   2010, 2, 571-576

      doi:  10.1038/nchem.653

      Abstract:

      Ruthenium-catalysed ring-closing metathesis (RCM) is a powerful   technique for the preparation of medium-to-large rings in organic   synthesis, but the details of the intimate mechanism are obscure.   The dynamic behaviour of an RCM-relevant ruthenacyclobutane   complex and its reactivity with ethene were   studied using low-temperature NMR spectroscopy to illuminate the   mechanism of this widely used reaction. These kinetic and   thermodynamic experiments allowed for mapping the energy surface   of the key steps in the RCM reaction as mediated by Grubbs-type   catalysts for alkene metathesis. The highest barrier along the   RCM path is only 65 kJ mol−1, which shows that this   catalyst has extremely high inherent activity. Furthermore, this   transition state corresponds to that connecting the intermediates   in this reaction leading to ring opening of the cyclopentene   product. This shows that ring closing is kinetically slightly   favoured over ring opening, in addition to being driven by the   loss of ethene.

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