Guest-enhanced kinetic stability of hydrogen-bonded dimeric capsules of tetraurea calix[4]arenes

Organic Letters

Volumn 2, Issue 23, 2000, Pages 3571-3574

  Vysotsky, Myroslav O ^a   Böhmer, Volker ^a  

^a JOHANNES GUTENBERG UNIVERSITY   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000949511     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol0064967     Document Type: Article

References (23)

1. Rebek, J., Jr. Chem. Commun. 2000, 637-643.
2. Mogck, O.; Paulus, E. F.; Böhmer, V.; Thondorf, I.; Vogt, W. Chem. Commun. 1996, 2533-2534.
3. (a) Hamman, B. C.; Shimizu, K. D.; Rebek, J., Jr. Angew. Chem. Int. Ed. Engl. 1996, 35, 1326-1329.
4. (b) Mogck, O.; Pons, M.; Böhmer, V.; Vogt, W. J. Am. Chem. Soc. 1997, 119, 5706-5712.
5. Schalley, C. A.; Castellano, R. K.; Brody, M. S.; Rudkevich, D. M. Siuzdak G.; Rebek, J., Jr. J. Am. Chem. Soc. 1999, 121, 4568-4579.
6. Vysotsky, M. O.; Thondorf, I.; Böhmer, V. Angew. Chem., Int. Ed. 2000, 39, 1264-1267.
7. Rudkevich, D. M.; Böhmer, V.; Rebek, J., Jr.; et al., unpublished results.
8. (a) Chapman, R. G.; Sherman, J. C. J. Am. Chem. Soc. 1995, 117, 9081-9082.
9. (b) Chapman, R. G.; Olovsson, G.; Trotter, J.; Sherman, J. C. J. Am. Chem. Soc. 1998, 120, 6252-6260.
10. Recently, kinetic studies on a "tennis ball" and "soft ball" self-assembling molecular capsules were reported in the following: (a) Santamaria, J.; Martín, T.; Hilmersson, G.; Craig, S. L.; Rebek, J., Jr. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 8344-8347.
11. (b) Rivera, J. M.; Craig, S. L.; Martín, T.; Rebek, J., Jr. Angew. Chem., Int. Ed. 2000, 39, 2130-2132.
12. (c) For theoretical calculations concerning this guest exchange, see: Wang, X.; Houk, K. N. Org. Lett. 1999, 1, 591-594.
13. Rheichart, C. Solvents and Solvent Effects in Organic Chemistry; VCH: Weinheim, 1990.
14. It is noteworthy that the solubility of the complexes listed in Table 1 depends drastically on the included guest. For example, the chloroform and toluene complexes are much less soluble (< 1 mg in 0.8 mL) than the kinetically more stable ones; compare the different chromatographic properties observed for hemicarceplexes which differ only by the guest molecules: Park, B. S.; Knobler, C. B.; Eid, C. N., Jr.; Warmuth, R.; Cram, D. J. Chem. Commun. 1998, 55-56. Yoon, J.; Cram, D. J. J. Am. Chem. Soc. 1997, 119, 11796-11806.
15. It is noteworthy that the solubility of the complexes listed in Table 1 depends drastically on the included guest. For example, the chloroform and toluene complexes are much less soluble (< 1 mg in 0.8 mL) than the kinetically more stable ones; compare the different chromatographic properties observed for hemicarceplexes which differ only by the guest molecules: Park, B. S.; Knobler, C. B.; Eid, C. N., Jr.; Warmuth, R.; Cram, D. J. Chem. Commun. 1998, 55-56. Yoon, J.; Cram, D. J. J. Am. Chem. Soc. 1997, 119, 11796-11806.
16. For this comparison we assume that the ether residues have no significant influence on the rate of guest exchange.
17. This observation does not fit well to the 55% occupancy of the capsule interior proposed by Mecozzi, S.; Rebek, J., Jr. Chem. Eur. J. 1998, 4, 1016-1022.
18. 3, see ref 3a.
19. 3 and toluene as guest). All spectra were recorded on a Bruker DRX 400 instrument using a proton-sensitive probehead.
20. For the ability of chloroform to form hydrogen bonds, see, for instance: Wiley, G. R.; Miller, S. I. J. Am. Chem. Soc. 1972, 94, 3287-3293.
21. 12.
22. The CIS values for the para-proton change from -1.95 to -1.63 ppm from fluoro- to bromobenzene, while a value of -3.17 ppm for toluene suggests a rather different orientation of the included guest, compare 3a.
23. Recently fluorescence resonance energy transfer has been used to characterize the kinetic stability: Castellano, R. K.; Craig, S. L.; Nuckolls, C.; Rebek, J., Jr. J. Am. Chem. Soc. 2000, 122, 7876-7882.