Partial OH → Me Replacement in the Calixarene Scaffold: Preparation, Conformation, and Stereodynamics of Tetra-terf-butyl-25,27-dihydroxy-26,28-dimethylcalix[4]arene and Its Dimethyl Ether Derivative

Journal of Organic Chemistry

Volumn 62, Issue 11, 1997, Pages 3511-3519

  Van Gelder, Joel M ^a   Brenn, Jörg ^b   Thondorf, Iris ^b   Biali, Silvio E ^a  

^a HEBREW UNIVERSITY OF JERUSALEM   (Israel)

^b MARTIN LUTHER UNIVERSITY HALLE WITTENBERG   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000108358     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo9623797     Document Type: Article

References (56)

1. For reviews on calixarenes see: (a) Gutsche, C, D. Calixarenes; Royal Society of Chemistry: Cambridge, 1989. (b) Calixarenes: A Versatile Class of Macrocyclic Compounds; Vicens, J., Böhmer, V., Eds.; Kluwer: Dordrecht, 1991. (c) Böhmer, V. Angew. Chem., Int. Ed. Engl. 1995, 34, 713. (d) Gutsche, C. D. Aldrichim. Acta 1995, 28, 1.
2. For reviews on calixarenes see: (a) Gutsche, C, D. Calixarenes; Royal Society of Chemistry: Cambridge, 1989. (b) Calixarenes: A Versatile Class of Macrocyclic Compounds; Vicens, J., Böhmer, V., Eds.; Kluwer: Dordrecht, 1991. (c) Böhmer, V. Angew. Chem., Int. Ed. Engl. 1995, 34, 713. (d) Gutsche, C. D. Aldrichim. Acta 1995, 28, 1.
3. For reviews on calixarenes see: (a) Gutsche, C, D. Calixarenes; Royal Society of Chemistry: Cambridge, 1989. (b) Calixarenes: A Versatile Class of Macrocyclic Compounds; Vicens, J., Böhmer, V., Eds.; Kluwer: Dordrecht, 1991. (c) Böhmer, V. Angew. Chem., Int. Ed. Engl. 1995, 34, 713. (d) Gutsche, C. D. Aldrichim. Acta 1995, 28, 1.
4. For reviews on calixarenes see: (a) Gutsche, C, D. Calixarenes; Royal Society of Chemistry: Cambridge, 1989. (b) Calixarenes: A Versatile Class of Macrocyclic Compounds; Vicens, J., Böhmer, V., Eds.; Kluwer: Dordrecht, 1991. (c) Böhmer, V. Angew. Chem., Int. Ed. Engl. 1995, 34, 713. (d) Gutsche, C. D. Aldrichim. Acta 1995, 28, 1.
5. (a) According to the "replacement of the hydroxyl group" section of the recent Rodd's Chemistry of Carbon Compounds (Tyman, J. H. P. In Second Supplements to the 2nd Edition of Rodd's Chemistry of Carbon Compounds; Sainsbury, M., Ed.; Elsevier, Amsterdam, 1996, Volume IIIA, p 247), phenolic hydroxyl groups can be replaced using phosgene in o-xylene. As an example, it is stated that 4-hydroxybenzophenone reacts under these conditions, yielding 4-(chlorocarbonyl)- benzophenone. However, the products obtained in the patent cited (BASF AG, DE 384443; Chem. Abstr. 1991, 114, 6031e) are not the chlorocarbonyls but the corresponding chloroformate derivatives.
6. (a) According to the "replacement of the hydroxyl group" section of the recent Rodd's Chemistry of Carbon Compounds (Tyman, J. H. P. In Second Supplements to the 2nd Edition of Rodd's Chemistry of Carbon Compounds; Sainsbury, M., Ed.; Elsevier, Amsterdam, 1996, Volume IIIA, p 247), phenolic hydroxyl groups can be replaced using phosgene in o-xylene. As an example, it is stated that 4-hydroxybenzophenone reacts under these conditions, yielding 4-(chlorocarbonyl)- benzophenone. However, the products obtained in the patent cited (BASF AG, DE 384443; Chem. Abstr. 1991, 114, 6031e) are not the chlorocarbonyls but the corresponding chloroformate derivatives.
7. (b) For a review on hydroxyl replacement in calixarenes see: Biali, S. E. Isr. J. Chem., in press.
8. See for example: (a) Goren, Z.; Biali, S. E. J. Chem. Soc., Perkin Trans. 1 1990, 1484. (b) Grynszpan, F.; Goren, Z.; Biali, S. E. J. Org. Chem. 1991, 56, 532. (c) de Vains, J.-B. R.; Pellet-Rostaing, S.; Lamartine, R. Tetrahedron Lett. 1994, 35, 8147. (d) Harada, T.; Ohseto, F.; Shinkai, S. Tetrahedron 1994, 50, 13377. (e) Matsuda, K.; Nakamura, N.; Takahashi, K.; Inoue, K.; Koga, N.; Iwamura, H. J. Am. Chem. Soc. 1995, 117, 5550. (f) For additional synthesis of dehydroxylated calixarenes see: Fukazawa, Y.; Deyama, K.; Usui, S. Tetrahedron Lett. 1992, 33, 5803. Usui, S.; Deyama, K.; Kinoshita, R.; Odagaki, Y.; Fukazawa, Y. Tetrahedron Lett. 1993, 34, 8127.
9. See for example: (a) Goren, Z.; Biali, S. E. J. Chem. Soc., Perkin Trans. 1 1990, 1484. (b) Grynszpan, F.; Goren, Z.; Biali, S. E. J. Org. Chem. 1991, 56, 532. (c) de Vains, J.-B. R.; Pellet-Rostaing, S.; Lamartine, R. Tetrahedron Lett. 1994, 35, 8147. (d) Harada, T.; Ohseto, F.; Shinkai, S. Tetrahedron 1994, 50, 13377. (e) Matsuda, K.; Nakamura, N.; Takahashi, K.; Inoue, K.; Koga, N.; Iwamura, H. J. Am. Chem. Soc. 1995, 117, 5550. (f) For additional synthesis of dehydroxylated calixarenes see: Fukazawa, Y.; Deyama, K.; Usui, S. Tetrahedron Lett. 1992, 33, 5803. Usui, S.; Deyama, K.; Kinoshita, R.; Odagaki, Y.; Fukazawa, Y. Tetrahedron Lett. 1993, 34, 8127.
10. See for example: (a) Goren, Z.; Biali, S. E. J. Chem. Soc., Perkin Trans. 1 1990, 1484. (b) Grynszpan, F.; Goren, Z.; Biali, S. E. J. Org. Chem. 1991, 56, 532. (c) de Vains, J.-B. R.; Pellet-Rostaing, S.; Lamartine, R. Tetrahedron Lett. 1994, 35, 8147. (d) Harada, T.; Ohseto, F.; Shinkai, S. Tetrahedron 1994, 50, 13377. (e) Matsuda, K.; Nakamura, N.; Takahashi, K.; Inoue, K.; Koga, N.; Iwamura, H. J. Am. Chem. Soc. 1995, 117, 5550. (f) For additional synthesis of dehydroxylated calixarenes see: Fukazawa, Y.; Deyama, K.; Usui, S. Tetrahedron Lett. 1992, 33, 5803. Usui, S.; Deyama, K.; Kinoshita, R.; Odagaki, Y.; Fukazawa, Y. Tetrahedron Lett. 1993, 34, 8127.
11. See for example: (a) Goren, Z.; Biali, S. E. J. Chem. Soc., Perkin Trans. 1 1990, 1484. (b) Grynszpan, F.; Goren, Z.; Biali, S. E. J. Org. Chem. 1991, 56, 532. (c) de Vains, J.-B. R.; Pellet-Rostaing, S.; Lamartine, R. Tetrahedron Lett. 1994, 35, 8147. (d) Harada, T.; Ohseto, F.; Shinkai, S. Tetrahedron 1994, 50, 13377. (e) Matsuda, K.; Nakamura, N.; Takahashi, K.; Inoue, K.; Koga, N.; Iwamura, H. J. Am. Chem. Soc. 1995, 117, 5550. (f) For additional synthesis of dehydroxylated calixarenes see: Fukazawa, Y.; Deyama, K.; Usui, S. Tetrahedron Lett. 1992, 33, 5803. Usui, S.; Deyama, K.; Kinoshita, R.; Odagaki, Y.; Fukazawa, Y. Tetrahedron Lett. 1993, 34, 8127.
12. See for example: (a) Goren, Z.; Biali, S. E. J. Chem. Soc., Perkin Trans. 1 1990, 1484. (b) Grynszpan, F.; Goren, Z.; Biali, S. E. J. Org. Chem. 1991, 56, 532. (c) de Vains, J.-B. R.; Pellet-Rostaing, S.; Lamartine, R. Tetrahedron Lett. 1994, 35, 8147. (d) Harada, T.; Ohseto, F.; Shinkai, S. Tetrahedron 1994, 50, 13377. (e) Matsuda, K.; Nakamura, N.; Takahashi, K.; Inoue, K.; Koga, N.; Iwamura, H. J. Am. Chem. Soc. 1995, 117, 5550. (f) For additional synthesis of dehydroxylated calixarenes see: Fukazawa, Y.; Deyama, K.; Usui, S. Tetrahedron Lett. 1992, 33, 5803. Usui, S.; Deyama, K.; Kinoshita, R.; Odagaki, Y.; Fukazawa, Y. Tetrahedron Lett. 1993, 34, 8127.
13. See for example: (a) Goren, Z.; Biali, S. E. J. Chem. Soc., Perkin Trans. 1 1990, 1484. (b) Grynszpan, F.; Goren, Z.; Biali, S. E. J. Org. Chem. 1991, 56, 532. (c) de Vains, J.-B. R.; Pellet-Rostaing, S.; Lamartine, R. Tetrahedron Lett. 1994, 35, 8147. (d) Harada, T.; Ohseto, F.; Shinkai, S. Tetrahedron 1994, 50, 13377. (e) Matsuda, K.; Nakamura, N.; Takahashi, K.; Inoue, K.; Koga, N.; Iwamura, H. J. Am. Chem. Soc. 1995, 117, 5550. (f) For additional synthesis of dehydroxylated calixarenes see: Fukazawa, Y.; Deyama, K.; Usui, S. Tetrahedron Lett. 1992, 33, 5803. Usui, S.; Deyama, K.; Kinoshita, R.; Odagaki, Y.; Fukazawa, Y. Tetrahedron Lett. 1993, 34, 8127.
14. See for example: (a) Goren, Z.; Biali, S. E. J. Chem. Soc., Perkin Trans. 1 1990, 1484. (b) Grynszpan, F.; Goren, Z.; Biali, S. E. J. Org. Chem. 1991, 56, 532. (c) de Vains, J.-B. R.; Pellet-Rostaing, S.; Lamartine, R. Tetrahedron Lett. 1994, 35, 8147. (d) Harada, T.; Ohseto, F.; Shinkai, S. Tetrahedron 1994, 50, 13377. (e) Matsuda, K.; Nakamura, N.; Takahashi, K.; Inoue, K.; Koga, N.; Iwamura, H. J. Am. Chem. Soc. 1995, 117, 5550. (f) For additional synthesis of dehydroxylated calixarenes see: Fukazawa, Y.; Deyama, K.; Usui, S. Tetrahedron Lett. 1992, 33, 5803. Usui, S.; Deyama, K.; Kinoshita, R.; Odagaki, Y.; Fukazawa, Y. Tetrahedron Lett. 1993, 34, 8127.
15. (a) Gibbs, C. G.; Gutsche, C. D. J. Am. Chem. Soc. 1993, 115, 5338.
16. (b) Ting, Y.; Verboom, W.; Groenen, L. C.; van Loon, J. D.; Reinhoudt, D. N. J. Chem. Soc., Chem. Commun. 1990, 1432.
17. (c) Delaigue, X.; Harrowfield, J. McB.; Hosseini, M. W.; de Cian, A.; Fischer, J.; Kyritsakas, N. J. Chem. Soc., Chem. Commun. 1994, 1579.
18. (d) Delaigue, X.; Hosseini, M. W.; Kyritsakas, N.; de Cian, A.; Fischer, J. J. Chem. Soc., Chem. Commun. 1995, 609.
19. (e) Gibbs, C. G.; Sujeeth, P. K.; Rogers, J. S.; Stanley, G. G.; Krawiec, M.; Watson, W. H.; Gutsche, C. D. J. Org. Chem. 1995, 60, 8394.
20. (a) Ohseto, F.; Murakami, H.; Araki, K.; Shinkai, S. Tetrahedron Lett. 1992, 33, 1217.
21. (b) Aleksiuk, O.; Grynszpan, F.; Biali, S. E. J. Org. Chem. 1993, 58, 1994.
22. (c) Grynszpan, F.; Aleksiuk, O.; Biali, S. E. J. Org. Chem. 1994, 59, 2070.
23. (d) Aleksiuk, O.; Cohen, S.; Biali, S. E. J. Am. Chem. Soc. 1995, 117, 9645.
24. Diazonium chemistry allowed the preparation of halo- and xanthenocalix[5]arenes: Van Gelder, J. M.; Aleksiuk, O.; Biali, S. E. J. Org. Chem. 1996, 61, 8419.
25. Pappalardo, S.; Bottino, F.; Ronsisvalle, G. Phosphorus Sulfur 1984, 19, 327.
26. Delaigue, X.; Hosseini, M. W. Tetrahedron Lett. 1993, 34, 8111.
27. Pappalardo, S.; Ferguson, G.; Gallagher, J. F. J. Org. Chem. 1992, 57, 7102.
28. Schätz, R.; Weber, C.; Schilling, G.; Oeser, T.; Huber-Patz, U.; Irngartinger, H.; von der Lieth, C.-W.; Pipkorn, R. Liebigs Ann. 1995, 1401.
29. Thondorf, I.; Brenn, J. J. Mol. Struct. (THEOCHEM), in press.
30. Litwak, A. M.; Grynszpan, F.; Aleksiuk, O.; Cohen, S.; Biali, S. E. J. Org. Chem. 1993, 58, 393.
31. For a review on spirodienone calixarene derivatives see: Aleksiuk, O.; Grynszpan, F.; Litwak, M. A.; Biali, S. E. New J. Chem. 1996, 20, 473.
32. This product was not detected in the reaction mixture when the reaction was carried out using 2.2 equiv of MeLi in THF.
33. Carey, F. A.; Tremper, H. S. J. Org. Chem. 1971, 36, 758.
34. For an example of an acid-catalyzed fragmentation of the macrocyclic ring of the monospirodienone derivative of calix[5]arene, see reference 5d.
35. For identification purposes, the aryl rings of 6 and 7 possessing intraannular methyl or methoxy groups will be dubbed "tolyl" and "anisyl", respectively.
36. Grynszpan, F.; Biali, S. E. Tetrahedron Lett. 1991, 32, 5155.
37. c) at the coalescence temperatures were calculated according to: Kurland, R. J.; Rubin, M. B.; Wise, W. B. J. Chem. Phys. 1964, 40, 2426.
38. Gutsche, C. D.; Bauer, L. J. J. Am. Chem. Soc. 1985, 107, 6052.
39. 1H NMR spectrum taken with a 400 MHz instrument). Indeed, using the 1 ppm = 60 Hz equivalence we were able to obtain all the (incorrect) lifetimes reported by Araki et al.
40. 1H NMR spectrum taken with a 400 MHz instrument). Indeed, using the 1 ppm = 60 Hz equivalence we were able to obtain all the (incorrect) lifetimes reported by Araki et al.
41. Dhawan, B.; Levine, J. A.; NO, K H.; Bauer, L. J.; Gutsche, C. D. Tetrahedron 1983, 39, 409. Grootenhuis, P. D. J.; Kollman, P. A.; Groenen, L. C.; Reinhoudt, D.; van Hummel, G. J.; Ugozzoli, F.; Andreetti, G. D. J. Am. Chem. Soc. 1990, 112, 4165. For calculations on the conformational preferences of 12, see: Groenen, L. C.; van Loon, J.-D.; Verboom, W.; Harkema, S.; Casnati, A.; Ungaro, R.; Pochini, A.; Ugozzoli, F.; Reinhoudt, D. N. J. Am. Chem. Soc. 1991, 113, 2385. Harada, T.; Rudzinski, J. M.; Shinkai, S. J. Chem. Soc., Perkin Trans. 2 1992, 2109. Nagasaki, T.; Sisido, K.; Arimura, T.; Shinkai, S. Tetrahedron 1992, 48, 797. Iwamoto, K.; Ikeda, A.; Araki, K.; Harada, T.; Shinkai, S. Tetrahedron 1993, 49, 9937.
42. Dhawan, B.; Levine, J. A.; NO, K H.; Bauer, L. J.; Gutsche, C. D. Tetrahedron 1983, 39, 409. Grootenhuis, P. D. J.; Kollman, P. A.; Groenen, L. C.; Reinhoudt, D.; van Hummel, G. J.; Ugozzoli, F.; Andreetti, G. D. J. Am. Chem. Soc. 1990, 112, 4165. For calculations on the conformational preferences of 12, see: Groenen, L. C.; van Loon, J.-D.; Verboom, W.; Harkema, S.; Casnati, A.; Ungaro, R.; Pochini, A.; Ugozzoli, F.; Reinhoudt, D. N. J. Am. Chem. Soc. 1991, 113, 2385. Harada, T.; Rudzinski, J. M.; Shinkai, S. J. Chem. Soc., Perkin Trans. 2 1992, 2109. Nagasaki, T.; Sisido, K.; Arimura, T.; Shinkai, S. Tetrahedron 1992, 48, 797. Iwamoto, K.; Ikeda, A.; Araki, K.; Harada, T.; Shinkai, S. Tetrahedron 1993, 49, 9937.
43. Dhawan, B.; Levine, J. A.; NO, K H.; Bauer, L. J.; Gutsche, C. D. Tetrahedron 1983, 39, 409. Grootenhuis, P. D. J.; Kollman, P. A.; Groenen, L. C.; Reinhoudt, D.; van Hummel, G. J.; Ugozzoli, F.; Andreetti, G. D. J. Am. Chem. Soc. 1990, 112, 4165. For calculations on the conformational preferences of 12, see: Groenen, L. C.; van Loon, J.-D.; Verboom, W.; Harkema, S.; Casnati, A.; Ungaro, R.; Pochini, A.; Ugozzoli, F.; Reinhoudt, D. N. J. Am. Chem. Soc. 1991, 113, 2385. Harada, T.; Rudzinski, J. M.; Shinkai, S. J. Chem. Soc., Perkin Trans. 2 1992, 2109. Nagasaki, T.; Sisido, K.; Arimura, T.; Shinkai, S. Tetrahedron 1992, 48, 797. Iwamoto, K.; Ikeda, A.; Araki, K.; Harada, T.; Shinkai, S. Tetrahedron 1993, 49, 9937.
44. Dhawan, B.; Levine, J. A.; NO, K H.; Bauer, L. J.; Gutsche, C. D. Tetrahedron 1983, 39, 409. Grootenhuis, P. D. J.; Kollman, P. A.; Groenen, L. C.; Reinhoudt, D.; van Hummel, G. J.; Ugozzoli, F.; Andreetti, G. D. J. Am. Chem. Soc. 1990, 112, 4165. For calculations on the conformational preferences of 12, see: Groenen, L. C.; van Loon, J.-D.; Verboom, W.; Harkema, S.; Casnati, A.; Ungaro, R.; Pochini, A.; Ugozzoli, F.; Reinhoudt, D. N. J. Am. Chem. Soc. 1991, 113, 2385. Harada, T.; Rudzinski, J. M.; Shinkai, S. J. Chem. Soc., Perkin Trans. 2 1992, 2109. Nagasaki, T.; Sisido, K.; Arimura, T.; Shinkai, S. Tetrahedron 1992, 48, 797. Iwamoto, K.; Ikeda, A.; Araki, K.; Harada, T.; Shinkai, S. Tetrahedron 1993, 49, 9937.
45. Dhawan, B.; Levine, J. A.; NO, K H.; Bauer, L. J.; Gutsche, C. D. Tetrahedron 1983, 39, 409. Grootenhuis, P. D. J.; Kollman, P. A.; Groenen, L. C.; Reinhoudt, D.; van Hummel, G. J.; Ugozzoli, F.; Andreetti, G. D. J. Am. Chem. Soc. 1990, 112, 4165. For calculations on the conformational preferences of 12, see: Groenen, L. C.; van Loon, J.-D.; Verboom, W.; Harkema, S.; Casnati, A.; Ungaro, R.; Pochini, A.; Ugozzoli, F.; Reinhoudt, D. N. J. Am. Chem. Soc. 1991, 113, 2385. Harada, T.; Rudzinski, J. M.; Shinkai, S. J. Chem. Soc., Perkin Trans. 2 1992, 2109. Nagasaki, T.; Sisido, K.; Arimura, T.; Shinkai, S. Tetrahedron 1992, 48, 797. Iwamoto, K.; Ikeda, A.; Araki, K.; Harada, T.; Shinkai, S. Tetrahedron 1993, 49, 9937.
46. Dhawan, B.; Levine, J. A.; NO, K H.; Bauer, L. J.; Gutsche, C. D. Tetrahedron 1983, 39, 409. Grootenhuis, P. D. J.; Kollman, P. A.; Groenen, L. C.; Reinhoudt, D.; van Hummel, G. J.; Ugozzoli, F.; Andreetti, G. D. J. Am. Chem. Soc. 1990, 112, 4165. For calculations on the conformational preferences of 12, see: Groenen, L. C.; van Loon, J.-D.; Verboom, W.; Harkema, S.; Casnati, A.; Ungaro, R.; Pochini, A.; Ugozzoli, F.; Reinhoudt, D. N. J. Am. Chem. Soc. 1991, 113, 2385. Harada, T.; Rudzinski, J. M.; Shinkai, S. J. Chem. Soc., Perkin Trans. 2 1992, 2109. Nagasaki, T.; Sisido, K.; Arimura, T.; Shinkai, S. Tetrahedron 1992, 48, 797. Iwamoto, K.; Ikeda, A.; Araki, K.; Harada, T.; Shinkai, S. Tetrahedron 1993, 49, 9937.
47. The exchange rates at the coalescence temperature were calculated by the Gutowsky-Holm equation. Gutowsky, H. S.; Holm, C. H. J. Chem. Phys. 1956, 25, 1228.
48. Anet, F. A. L.; Basus, V. J. J. Mag. Reson. 1978, 32, 339. For papers using this method see for example: Adams, S. P.; Whitlock, H. W. J. Am. Chem. Soc. 1982, 104, 1602. Casarini, D.; Lunazzi, L.; Macciantelli, D. J. Chem. Soc., Perkin Trans. 2, 1985, 1839. For a recent example of the use of this technique for extracting conformational equilibria and rotational barriers of conformational biased calixarene systems, see: Biali, S. E.; Böhmer, V.; Cohen, S.; Ferguson, G.; Grüttner, C.; Grynszpan, F.; Paulus, E. F.; Thondorf, I.; Vogt, W. J. Am. Chem. Soc. 1996, 118, 12938.
49. Anet, F. A. L.; Basus, V. J. J. Mag. Reson. 1978, 32, 339. For papers using this method see for example: Adams, S. P.; Whitlock, H. W. J. Am. Chem. Soc. 1982, 104, 1602. Casarini, D.; Lunazzi, L.; Macciantelli, D. J. Chem. Soc., Perkin Trans. 2, 1985, 1839. For a recent example of the use of this technique for extracting conformational equilibria and rotational barriers of conformational biased calixarene systems, see: Biali, S. E.; Böhmer, V.; Cohen, S.; Ferguson, G.; Grüttner, C.; Grynszpan, F.; Paulus, E. F.; Thondorf, I.; Vogt, W. J. Am. Chem. Soc. 1996, 118, 12938.
50. Anet, F. A. L.; Basus, V. J. J. Mag. Reson. 1978, 32, 339. For papers using this method see for example: Adams, S. P.; Whitlock, H. W. J. Am. Chem. Soc. 1982, 104, 1602. Casarini, D.; Lunazzi, L.; Macciantelli, D. J. Chem. Soc., Perkin Trans. 2, 1985, 1839. For a recent example of the use of this technique for extracting conformational equilibria and rotational barriers of conformational biased calixarene systems, see: Biali, S. E.; Böhmer, V.; Cohen, S.; Ferguson, G.; Grüttner, C.; Grynszpan, F.; Paulus, E. F.; Thondorf, I.; Vogt, W. J. Am. Chem. Soc. 1996, 118, 12938.
51. Anet, F. A. L.; Basus, V. J. J. Mag. Reson. 1978, 32, 339. For papers using this method see for example: Adams, S. P.; Whitlock, H. W. J. Am. Chem. Soc. 1982, 104, 1602. Casarini, D.; Lunazzi, L.; Macciantelli, D. J. Chem. Soc., Perkin Trans. 2, 1985, 1839. For a recent example of the use of this technique for extracting conformational equilibria and rotational barriers of conformational biased calixarene systems, see: Biali, S. E.; Böhmer, V.; Cohen, S.; Ferguson, G.; Grüttner, C.; Grynszpan, F.; Paulus, E. F.; Thondorf, I.; Vogt, W. J. Am. Chem. Soc. 1996, 118, 12938.
52. m), the rate constant for the conversion of the more stable to the less stable conformer is given by k = 2πpΔv (ref 24).
53. MM3(92) is available from the Quantum Chemistry Program Exchange, University of Indiana, Bloomington, IN 47405.
54. Fischer, S.; Grootenhuis, P. D. J.; Groenen, L. C.; van Hoorn, W. P.; van Veggel, F. C. J. M.; Reinhoudt, D. N.; Karplus, M, J. Am. Chem. Soc. 1995, 117, 1611.
55. -1 between the barriers extracted from the broadening of the Me signal (exchange with a hidden partner) and the topomerization of the methylene protons (coalescence). This is due to the uncertainty in the chemical shift of the signal of the "hidden" conformer. Moreover, in order to properly compare the rate constants (and barriers) extracted from the two methods a statistical correction factor must be introduced since the first method measures directly the 1,3-alt → paco interconversion, while the second method only follows the molecules in which the two diastereotopic methylene had exchanged magnetic sites. Since the ring inversion process involves a symmetrical intermediate (1,2-alt) which may revert either to "reactant" or "product", half of the molecules which reach that conformation revert to the original 1,3-alt form without topomerization of the methylene protons. The actual rate of the 1,3-alt → paco interconversion (the rate-determining step in the process) is therefore twice the rate derived by the coalescence approximation.
56. The authors have deposited atomic coordinates for the structures with the Cambridge Crystallographic Data Centre. The coordinates can be obtained, on request, from the Director, Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK.