View PDF Version
 
DOI: 10.1039/A607063I (Paper) Reference Section for: J. Chem. Soc., Perkin Trans. 2, 1997, 721-728

Studies in nitrosopyrazoles. Part 2.1 Solution and solid-state NMR studies of 3,5-disubstituted and 1,3,5-trisubstituted-4-nitrosopyrazoles. Crystal structures of 1,3,5-trimethyl-4-nitrosopyrazole and 3,5-di-tert-butyl-4-nitrosopyrazole

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

Daniel A. Fletcher, Brian G. Gowenlock, Keith G. Orrell, Vladimir Šik, David E. Hibbs, Michael B. Hursthouse and K. M. Abdul Malik

Abstract

Variable temperature NMR studies of a range of 3,5-disubstituted (R = R′ = Me, But) and 1,3,5-trisubstituted (R, R′, R″ = Me, CF3, Ph or Bui)-4-nitrosopyrazoles have led to the identification of individual rotational isomers at low solution temperatures arising from the slowing down of the rotation of the nitroso function with respect to the pyrazole ring. Rotational energy barriers [ΔG[hair space]‡ (298.15 K)], calculated by total NMR bandshape analysis, were in the range 38–65 kJ mol-1. The –N[double bond, length as m-dash]O rotation process also occurs in the solid state and leads to disorder in the crystal structures of 1,3,5-trimethyl-4-nitrosopyrazole and 3,5-di-tert-butyl-4-nitrosopyrazole. The 1-H-3,5-disubstituted-4-nitrosopyrazoles exhibit rapid annular tautomerism in solution.

References

  1. Part 1, M. Cameron, B. G. Gowenlock and A. S. F. Boyd, J. Chem. Soc., Perkin Trans. 2, 1996, 2271 Search PubMed.
  2. L. Wolff, P. Bock, G. Lorentz and P. Trappe, Liebigs Ann. Chem., 1902, 325, 129 Search PubMed.
  3. J. Sandstrom, Dynamic NMR Spectroscopy, Academic, London, 1982 Search PubMed.
  4. D. A. Fletcher, B. G. Gowenlock, K. G. Orrell and V. Šik, Magn. Reson. Chem., 1995, 33, 561 CAS and references therein.
  5. M. D. Lumsden, G. Wu, R. E. Wasylishen and R. D. Curtis, J. Am. Chem. Soc., 1993, 115, 2825 CrossRef CAS.
  6. D. A. Fletcher, Ph.D. Thesis, University of Exeter, 1996.
  7. G. L. McNew and N. K. Sundholm, Phytopathology, 1949, 39, 721 Search PubMed.
  8. S. E. Torf, N. I. Kudryashova, N. V. Khromov-Bonner and T. A. Mikhailova, J. Gen. Chem. (USSR), 1962, 32, 1726.
  9. G. V. Boyd and T. Norris, J. Chem. Soc., Perkin Trans. 1, 1974, 1028 RSC.
  10. R. Hüttel, F. Büchele and P. Jochum, Chem. Ber., 1955, 88, 1577 CAS.
  11. C. L. Habraken, C. I. M. Beenakker and J. Brusee, J. Heterocycl. Chem., 1972, 9, 939 CAS.
  12. G. A. Lanovaya, V. P. Micheeva and S. V. Orlova, Khim. Geterotskii. Soed., 1989, 25, 337 Search PubMed.
  13. F. Aguilar-Parilla, C. Cativiela, M. D. D. de Villegas, J. Elguero, C. Foces-Foces, J. I. G. Laureiro, F. H. Cano, H.-H. Limbach, J. A. S. Smith and C. Toiron, J. Chem. Soc., Perkin Trans. 2, 1992, 1737 RSC and references therein.
  14. G. Binsch and D. A. Kleier, Program 165, Quantum Chemistry Program Exchange, Indiana University, IN, 1970.
  15. V. Šik, Ph.D. Thesis, University of Exeter, 1979.
  16. E. W. Abel, T. P. J. Coston, K. G. Orrell, V. Šik and D. Stephenson, J. Magn. Reson., 1986, 70, 34 CAS.
  17. S. J. Opella and M. H. Frey, J. Am. Chem. Soc., 1979, 101, 5854 CrossRef CAS.
  18. W. T. Dixon, J. Chem. Phys., 1982, 77, 1800 CrossRef CAS.
  19. J. A. Darr, S. R. Drake, M. B. Hursthouse and K. M. A. Malik, Inorg. Chem., 1993, 32, 5104.
  20. G. M. Sheldrick, Acta Crystallogr. Sect. A, 1990, 46, 467 CrossRef.
  21. G. M. Sheldrick, SHELXL-93, Program for Crystal Structure Refinement, University of Göttingen, 1993.
  22. B. Knieriem, Doctoral thesis, University of Göttingen, 1972.
  23. H. J. Talberg, Acta Chem. Scand., Ser. A, 1977, 31, 743.
  24. R. Dunlop, A. D. U. Hardy, H. H. Mills, R. K. Mackenzie, D. D. MacNicol and D. A. R. Williams, J. Chem. Res., (S), 1979, 152 Search PubMed; J. Chem. Res. (M), 1979, 1848 Search PubMed.
  25. H. J. Talberg, Acta Chem. Scand., Ser. A, 1979, 33, 289.
  26. H. J. Talberg, Acta Chem. Scand., Ser. A, 1977, 31, 485.
  27. H. J. Talberg, Acta Chem. Scand., Ser. A, 1976, 30, 829.
  28. H. J. Talberg, Acta Chem. Scand., Ser. A, 1977, 31, 37.
  29. H. J. Talberg, Acta Chem. Scand., Ser. A, 1975, 29, 919.
  30. D. A. Fletcher, B. G. Gowenlock, K. G. Orrell, V. Šik, D. E. Hibbs, M. B. Hursthouse and K. M. A. Malik, J. Chem. Soc., Perkin Trans. 2, 1996, 191 RSC.
  31. R. Glaser, R. K. Murmann and C. L. Barnes, J. Org. Chem., 1996, 61, 1047 CrossRef CAS.
Click here to see how this site uses Cookies. View our privacy policy here.