Pentazole chemistry: the mechanism of the reaction of aryldiazonium chlorides with azide ion at –80 °C: concerted versus stepwise formation of arylpentazoles, detection of a pentazene intermediate, a combined ¹H and ¹⁵N NMR experimental and ab initio theoretical study

Abstract

The reaction of p-chlorophenyldiazonium chloride with azide ion at –80 °C has been examined by ¹H and ¹⁵N NMR spectra. The main product, p -azidochlorobenzene, was present in the earliest spectra. Spectra were obtained before the appearance of the second product, p-chlorophenylpentazole and an intermediate was observed. Correlated ab initio calculations at the MP2/6-31G* level on 1H-pentazole and 1-phenylpentazole agree with the NMR spectra. An (E,Z )-arylpentazene 3 is the key intermediate leading to the 1-arylpentazole products. A (Z,E )-arylpentazene 2 leads directly to the aryl azide and is not convertible to the E-isomer. Three isomeric arylpentazenes, Z,E, E,E and E,Z are formed from initial azide ion attack at the diazonium β-atom.

References

1. (a) For reviews see, I. Ugi, Comprehensive Heterocyclic Chemistry, Series eds. A. R. Katritzky, C. W. Rees, Pergamon Press, Oxford, 1984, vol. 5, p. 839; (b) R. N. Butler, Comprehensive Heterocyclic Chemistry 11, Series eds., A. R. Katritzky, C. W. Rees, E. F. V. Scriven, Pergamon Press, Oxford, 1996, vol. 4, (ed., R. C. Storr), p. 897.
2. R. Huisgen and I. Ugi, Angew. Chem., 1956, 68, 705.
3. R. Huisgen and I. Ugi, Chem. Ber., 1957, 90, 2914.
4. R. Huisgen and I. Ugi, Chem. Ber., 1958, 91, 531.
5. R. Huisgen, The Adventure Playground of Mechanisms and Novel Reactions, American Chemical Society, Washington DC, 1994, pp. 79–82.
6. R. N. Butler, S. Collier and A. F. M. Fleming, J. Chem. Soc., Perkin Trans. 2, 1996, 801.
7. For a review see A. F. Hegarty, Acc. Chem. Res., 1980, 13, 448 and references therein.
8. A. F. Hegarty and M. T. McCormack, J. Chem. Soc., Perkin Trans. 2, 1976, 1701; J. Chem. Soc., Chem. Commun., 1975, 168.
9. P. Deslongchamps, in Stereoelectronic Effects in Organic Chemistry, Pergamon Press, Oxford, 1983, pp. 291–300.
10. R. N. Butler and D. P. Shelly, J. Chem. Soc., Perkin Trans. 1, 1986, 1101.
11. R. J. W. Le Fevre and H. Vine, J. Chem. Soc., 1938, 431; R. J. W. Le Fevre and I. R. Wilson, J. Chem. Soc., 1949, 1106.
12. M. F. Ahearn, A. Leopold, J. R. Bradle and G. W. Gokel, J. Am. Chem. Soc., 1982, 104, 548; R. M. Elofson, N. Cry, J. K. Laidler and K. F. Schulz, Tetrahedron Lett., 1984, 3039; E. S. Lewis and H. Suhr, Chem. Ber., 1959, 92, 3043.
13. For a review see A. F. Hegarty, in Chemistry of the Diazonium and Diazo Group, ed. S. Patai, Wiley, New York, 1978, pp. 511–591.
14. E. L. Eliel and S. H. Wilen, Stereochemistry of Organic Compounds, Wiley, New York, 1994, 1978, pp. 550–555 and references therein.
15. M. Sana, G. Leroy, M.-T. Nguyen and J. Elguero, Nouv. J. Chim., 1979, 3, 607.
16. A. Schulz, I. C. Tornieporth-Oetting and T. M. Klapotke, Angew. Chem., Int. Ed. Engl., 1993, 32, 1610.
17. B. S. Furniss, A. J. Hannaford, P. W. G. Smith and A. R. Tatchell, Vogel's Textbook of Organic Chemistry, 5th edn., Longman ScientiWc & Technical, Essex, 1989, pp. 856–857 and 892.
18. K. M. Ferris and R. J. Bartlett, J. Am. Chem. Soc., 1992, 114, 3802.
19. GAUSSIAN94 (Revision E.2), M. J. Frisch, G. W. Trucks, H. B. Schegel, P. M. W. Gill, B. G. Johnson, M. A. Robb, J. R. Cheeseman, T. A. Keith, G. A. Petersson, J. A. Montgomery, K. Ragavachari, M. A. Al-Laham, V. G. Kakrzewski, J. V. Ortiz, J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Nanayakkara, M. Challacombe, C. Y. Peng, P. Y. Ayala, W. Chen, M. W. Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez and J. A. Pople, Gaussian, Inc., Pittsburgh, PA, 1997.