Elimination and addition reactions. Part 41. Nucleophilic eliminative fission of cyclopropanes: the coiled spring effect of ring strain on nucleofugality and its evaluation

Rates have been measured of sulphonyl-activated eliminative ring fissions of a series of six cyclopropanes in which the leaving group is stabilised by alkoxycarbonyl, cyano, or sulphonyl groups

Simon Hughes; Gwerydd Griffiths; Charles J. M. Stirling

2004

Scholarcy highlights

  • Rates have been measured of sulphonyl-activated eliminative ring fissions of a series of six cyclopropanes in which the leaving group is stabilised by alkoxycarbonyl, cyano, or sulphonyl groups
  • Rank enhancements of about 9 units are obtained; these enhancements suggest that free energies of activation for leaving-group expulsion are reduced by about 53 kJ mol–1, or about 46% of the excess of enthalpy of the strained ring, notwithstanding the small degree of ring fission in the transition structure
  • The effect of phenyl substitution at the leaving group suggests that cleavage of the ring is very little advanced in the transition structure, this is variable with the nature of the leaving-group stabilisation
  • Nucleophilic eliminative fission of cyclopropanes: the coiled spring effect of ring strain on nucleofugality and its evaluation

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