Anion template-directed synthesis of dicationic [14]imidazoliophanes

Organic Letters

Volumn 1, Issue 7, 1999, Pages 1035-1038

  Alcalde, Ermitas ^a   Ramos, Susana ^a   Pérez García, Lluïsa ^a  

^a UNIVERSITY OF BARCELONA   (Spain)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000178804     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol990818t     Document Type: Article

References (38)

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2. For reviews, see: (a) Chapman, R. G.; Sherman, J. C. Tetrahedron 1997, 53, 15911-15945.
3. (b) Busch, D. H.; Vance, A. L.; Kolchinksi, A. G. Comprehensive Supramolecular Chemistry, Atwood, J. L.; Davies, J. E. D.; Macnicol, D. D.; Vögtle, F.; Sauvage, J.-P.; Wais Hosseini, M., Eds.; Pergamon Press: Oxford, 1996; Vol. 9, pp 1-42.
4. (c) Hoss, R.; Vögtle, F. Angew. Chem., Int. Ed. Engl. 1994, 33, 375-384.
5. (d) Anderson, S.; Anderson, H. L.; Sanders, J. K. M. Acc. Chem. Res. 1993, 26, 469-475.
6. (a) As for neutral templates, prime examples are Stoddart's synthesis of tetracationic [2]catenanes, which involved the use of macrocyclic polyether templates (refs 1 and 2). Both competitive self-assembly experiments (ref 3b) and kinetic studies (ref 3c) have shown that the selectivity for catenane formation is under kinetic control,
7. (b) Amabilino, D. B.; Ashton, P. R.; Pérez-García, L.; Stoddart, J. F. Angew. Chem., Int. Ed. Engl. 1995, 34, 2378-2380.
8. (c) Capobianchi, S.; Doddi, G.; Ercolani, G.; Mencarelli, P. J. Org. Chem. 1998, 63, 8088-8089.
9. For some examples of anion templates in the synthesis of organic molecules and supramolecules, see: (a) Fyfe, M. C. T.; Glink, P. T.; Menzer, S.; Stoddart, J. F.; White, A. J. P.; Williams, D. J. Angew. Chem., Int. Ed. Engl. 1997, 56, 2068-2070.
10. (b) Li, F.; Yang, K.; Tyhonas, J. S.; MacCrum, K. A.; Lindsey, J. S. Tetrahedron 1997, 55, 12239-12360.
11. (c) Kim, Y. H.; Calabrese, J.; McEwen, C. J. Am. Chem. Soc. 1996, 118, 1545-1546.
12. (d) Sánchez-Quesada, J.; Seel, C.; Prados, P.; de Mendoza, J.; Dalcol, I.; Giralt, E. J. Am. Chem. Soc. 1996, 118, 277-278.
13. (e) Fujita, M.; Nagao, S.; Ogura, K. J. Am. Chem. Soc. 1995, 117, 1649-1650.
14. (f) Sessler, J. L.; Mody, T. D.; Lynch, V. J. Am. Chem. Soc. 1993, 115, 3346-3347, and references therein.
15. (a) Alcalde, E.; Alemany, M.; Gisbert, M.; Pérez-García, L. Synlett. 1995, 757-760.
16. (b) Alcalde, E.; Alemany, M.; Gisbert, M. Tetrahedron 1996, 52, 15171-15188, and references therein.
17. Alcalde, E.; Gisbert, M. Synlett 1996, 285-288.
18. - hydrogen bonds are the noncovalent forces driving the anion interactions shown by these simple [14]imidazoliophanes (e.g. 3·2Cl) both in the solid state and in solution, where proton NMR studies also revealed the importance of hydrogen bonds in controlling the tendency to anion recognition (ref 8).
19. (b) Alcalde, E.; Alvarez-Rúa, C.; García-Granda, S.; García-Rodriguez, E.; Mesquida, N.; Pérez-García, L. Chem. Commun. 1999, 295-296.
20. For reviews, see: (a) Supramolecular Chemistry of Anions; Bianchi, A.; Bowman-James, K.; García-España, E., Eds.; Wiley-VCH: New York, 1997.
21. (b) Schmidtchen, F. P.; Berger, M. Chem. Rev. 1997, 97, 1609-1646.
22. Protophanes 5 (ref 5) and 6 (ref 7b) were obtained by reaction of imidazole with 3,5-bis(chloromethyl)triazole 7 or 1,3-bis(chloromethyl)-benzene 8.
23. (a) First, we explored the optimal initial concentration of the starting materials for model imidazoliophane 3·2Cl-protophane 6 and bis(chloromethyl)benzene 8. The yield of 3·2Cl increased almost linearly with concentration up to 5 mM; above this concentration, the yield was invariable - ca. 70%. However, the macrocyclization reactions leading to 2·2X-4·2X were performed at lower concentration, 2.3 mM, due to solubility limitations of the s-triazole reactants and to reduce the experimental error in the evaluation of the template effect. (b) Using high dilution conditions no significant changes in the yield of azoliophanes related to 2·2Cl were observed (ref 5b).
24. 2·2X were recovered.
25. We also optimized the amount of tetrabutylammonium salt to be added as the source of anions. We performed the macrocyclization affording 3·2Cl in the presence of different amounts of TBA·Cl, and we found a maximum yield (83%) when 5 equiv was used; this was the quantity used in all the experiments performed to evaluate the effect of the anion template on the synthesis of the title phanes 2·2X-4·2X (Table 1).
26. (a) All yields are averages of more than two experiments.
27. 1H NMR of one aliquot of the reaction solution.
28. (c) Liquid chromatography was used to quantifiy the extension of the anion exchange in 2·2X-4·2X-induced by performing the macrocyclization reaction in the presence of different anions.
29. Tetrabutylammonium salts used in the template experiments are commercially available, and they were used as received, despite the fact that some of them contain an undetermined amount of water.
30. -] hydrogen bonds established between the chloride ions with both aromatic hydrogen atoms on the m-xylyl spacer and the acidic protons on the imidazolium rings.
31. (b) Its macrocyclic cavity is a square of ca. 5 Å side, and the chloride anions occupy an outer position above and below the main plane defined by the methylene spacer groups (ref 15c).
32. (c) In the solid state, some calix[4]pyrroles have been reported to adopt a conelike conformation such that the four NH protons can hydrogen bond to the halide anion - the fluoride complex and the chloride complex (ref 15d,e).
33. (d) Gale, P. A.; Sessler, J. L.; Král, V.; Lynch, V. J. Am. Chem. Soc. 1996, 118, 5140-5141.
34. (e) Gale, P. A.; Sessler, J. L.; Král, V. Chem. Commun. 1998, 1-8.
35. (a) The optimal conformation required for the anion-directed macrocyclization relies on the hydrogen bond interaction between the halide anion and the NH group in the 4H tautomeric form of 1,2,4-triaxole which is the less favored tautomer in solution (ref 16b).
36. (b) Elguero, J., Marzin, C.; Katritzky, A. R.; Linda, P. Adv. Heterocycl. Chem. 1976, 1, 284-287.
37. (a) Nucleophilic substitution reactions are suitable for studying the consequences of the Kauffmann's areno-analogy principle and its application within π-excessive heteroaromatic systems (ref 17b).
38. (b) Kauffmann, T. Angew. Chem. Int. Ed. Engl. 1979, 18, 1-19.