View PDF Version
 
DOI: 10.1039/A805695A (Paper) Reference Section for: J. Chem. Soc., Perkin Trans. 2, 1998, 2381-2384

Aminolysis of sulfamate esters in non-aqueous solvents. Use of Brønsted coefficients (βnuc) to assign E2 and E1cB mechanisms

(Note: The full text of this document is currently only available in the PDF Version )

William J. Spillane and Chris Brack

Abstract

A series of Hammett ρacyl values for the aminolysis in chloroform and acetonitrile at 37 °C of the sulfamate esters RNHSO2OC6H4NO2-4 (R = XC6H4-, X = 4-MeO, 4-Me, 3-Me, H, 4-Br and 3-Cl) have been measured using piperidine and a set of five pyridines. Hammett ρpyr values have also been measured for various esters using a set of pyridines with varying substituents in the pyridine ring. A series of Brønsted βnuc values have been measured for the sulfamate esters. All the available βnuc values for sulfamate ester aminolysis have been compared and from this it has been possible to make mechanistic assignments to E1cB (βnucca. 0.7 and ca. 0) and E2 (βnuc 0.17 to 0.54) pathways. In the case of the E2 mechanism those reactions with lower βnuc values are thought to have little Nβ–H bond-breaking but this process is well advanced giving carbanionic E1cB-like characteristics to the E2 mechanism for reactions with larger βnuc values. Thermodynamic data (ΔH[hair space] ‡ and ΔS[hair space] ‡) support these interpretations.

References

  1. W. J. Spillane, G. Hogan, P. McGrath, J. King and C. Brack, J. Chem. Soc., Perkin Trans. 2, 1996, 2099 RSC .
  2. W. J. Spillane, G. Hogan, P. McGrath and J. King, J. Chem. Soc., Perkin Trans. 2, 1998, 309 RSC .
  3. W. J. Spillane, P. McGrath, C. Brack and K. Barry, J. Chem. Soc., Chem. Commun., 1998, 1017 RSC .
  4. A. Williams and K. T. Douglas, J. Chem. Soc., Perkin Trans. 2, 1974, 1727 RSC ; S. Thea, G. Cevasco, G. Gianti and A. Williams, J. Chem. Soc., Chem. Commun., 1986, 1582 RSC .
  5. W. J. Spillane, G. Hogan and P. McGrath, J. Phys. Org. Chem., 1995, 8, 610 CrossRef CAS .
  6. W. J. Spillane, F. A. McHugh and P. O. Burke, J. Chem. Soc., Perkin Trans. 2, 1998, 13 RSC .
  7. J. R. Gandler, in The Chemistry of Double-bonded Functional Groups, ed. S. Patai, vol. 2, Pt. 1, Supplement A, ch. 12, Wiley, London, 1989 Search PubMed .
  8. T. H. Lowry and K. S. Richardson, Mechanism and Theory in Organic Chemistry, 3rd edn., Harper Collins, 1987, pp. 588et seq. Search PubMed .
  9. A. I. Biggs and R. A. Robinson, J. Chem. Soc., 1961, 388 RSC .
  10. R. F. Hudson and G. Klopman, J. Chem. Soc., 1964, 5 RSC .
  11. (a) B. D. England and D. J. McLennan, J. Chem. Soc. B, 1966, 616 Search PubMed ; (b) D. J. McLennan, ibid., 1966, 705 Search PubMed ; (c) D. J. McLennan, ibid., 1966, 709 Search PubMed .
  12. J. R. Gandler and T. Yokoyama, J. Am. Chem. Soc., 1984, 106, 130 CrossRef CAS .
  13. B. J. Mayer, T. A. Spencer and K. D. Oman, J. Am. Chem. Soc., 1984, 106, 6347 .
  14. J. R. Gandler and W. P. Jencks, J. Am. Chem. Soc., 1982, 104, 1937 CrossRef CAS .
  15. Chris Brack, PhD Thesis, National University of Ireland, 1998 .
Click here to see how this site uses Cookies. View our privacy policy here.