Concave reagents. Part 27.¹ Steric requirements of intraannular substituents in A,D-bridged calix[6]arenes

Abstract

A series of A,D-m-xylylene bridged calix[6]arenes 5 carrying substituents of different size in 2-position of the bridge have been investigated by dynamic NMR spectroscopy and by force field methods. Molecular mechanics calculations indicate a bean shaped conformation as the global energy minimum in which the calixarene scaffold adopts a half-pinched/half-winged arrangement.

References

1. Presented at the 4th International Conference on Calixarenes in Parma, Italy, 31.8–4.9, 1997. Concave Reagents. Part 26: V. Lüning, S. Petersen, W. Schyja, W. Hacker, T. Marquardt, K. Wagner and M. Bolte, Eur. J. Org. Chem., 1998, in the press.
2. For a survey see: M. Oki, Applications of Dynamic NMR Spectroscopy to Organic Chemistry, VCH, Deerfield Beach, Weinheim, 1985.
3. E. L. Eliel, Stereochemistry of Carbon Compounds, McGraw-Hill, New York, 1962.
4. G. Bott, L. D. Field and S. Sternhell, J. Am. Chem. Soc., 1980, 102, 5618.
5. (a) B. L. Hawkins, W. Bremser, S. Borcic and J. D. Roberts, J. Am. Chem. Soc., 1971, 93, 4472; (b) A. Mannschreck and L. Ernst, Chem. Ber., 1971, 104, 228; (c) R. W. Taft, Jr., in Steric Effects in Organic Chemistry, ed. M. S. Newman, Wiley, New York, London, 2nd ed., 1963, ch. 13 [E_s(Cl)=+0.18, E_s(Br)= 0, E_s(CH₃)≡ 0].
6. B. Nilsson, P. Martinson, K. Olsson and R. E. Carter, J. Am. Chem. Soc., 1974, 96, 3190.
7. H. Förster and F. Vögtle, Angew. Chem., 1977, 89, 443; Angew. Chem., Int. Ed. Engl., 1977, 16, 429.
8. H. Otsuka, K. Araki and S. Shinkai, J. Org. Chem., 1994, 59, 1542.
9. (a) N. Tokitoh, T. Saiki and R. Okazaki, J. Chem. Soc., Chem. Commun., 1995, 1899; (b) T. Saiki, K. Goto, N. Tokitoh, M. Goto and R. Okazaki, Tetrahedron Lett., 1996, 37, 4039; (c) T. Saiki, K. Goto, N. Tokitoh and R. Okazaki, J. Org. Chem., 1996, 61, 2924; (d) T. Saiki, K. Goto and R. Okazaki, Chem. Lett., 1996, 993.
10. H. Ross and U. Lüning, Tetrahedron, 1996, 52, 10 879.
11. (a) U. Lüning, Liebigs Ann. Chem., 1987, 949; (b) U. Lüning, Top. Curr. Chem., 1995, 175, 57; (c) U. Lüning, J. Mater. Chem., 1997, 7, 175.
12. (a) H. Ross and U. Lüning, Angew. Chem., 1995, 107, 2723; Angew. Chem., Int. Ed. Engl., 1995, 34, 2555; (b) H. Ross and U. Lüning, Liebigs Ann., 1996, 1367.
13. S. Kanamathareddy and C. D. Gutsche, J. Am. Chem. Soc., 1993, 115, 6572.
14. (a) The all-u conformation is also referred to as the cone conformation: C. D. Gutsche, Calixarenes, The Royal Society of Chemistry, Cambridge, 1989; (b) Calixarenes, a Versatile Class of Macrocyclic Compounds, eds. J. Vicens and V. Böhmer, Kluwer Academic, Dordrecht, 1991; (c) V. Böhmer, Angew. Chem., 1995, 107, 785; Angew. Chem., Int. Ed. Engl., 1995, 34, 713.
15. (a) M. A. Molins, P. M. Nieto, C. Sanchez, P. Prados, J. de Mendoza and M. Pons, J. Org. Chem., 1992, 57, 6924; (b) R. G. Janssen, J. P. M. van Duynhoven, W. Verboom, G. J. van Hummel, S. Harkema and D. N. Reinhoudt, J. Am. Chem. Soc., 1996, 118, 3666.
16. W. P. van Hoorn, F. C. J. M. van Veggel and D. N. Reinhoudt, J. Org. Chem., 1996, 61, 7180.
17. M. Saunders, J. Am. Chem. Soc., 1987, 109, 3150.
18. (a) N. L. Allinger, Y. H. Yuh and J.-H. Lii, J. Am. Chem. Soc., 1989, 111, 8551; (b) J.-H. Lii and N. L. Allinger, ibid, 8566; (c) J.-H. Lii and N. L. Allinger, ibid, 8576.
19. From AMBER* calculations Okazaki et al.^9b have obtained the pinched cone conformation as most stable for 5c.
20. Such a structure has been reported by Reinhoudt et al.¹⁶ as a calculated intermediate of the ring inversion process of the winged cone structure.
21. C. D. Gutsche, B. Dhawan, M. Leonis and D. Stewart, Org. Synth., 1989, 68, 238.
22. F. Vögtle, Chem. Ber., 1969, 102, 1784.
23. W. Wieder, R. Nätscher and F. Vögtle, Justus Liebigs Ann. Chem., 1976, 924.
24. F. Vögtle, P. Neumann and M. Zuber, Chem. Ber., 1972, 105, 2955.
25. F. Vögtle, J. Grütze, R. Nätscher, W. Wieder, E. Weber and R. Grün, Chem. Ber., 1975, 108, 1694.