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Volumn 124, Issue 49, 2002, Pages 14631-14641

Enantioselective formation of a dynamic hydrogen-bonded assembly based on the chiral memory concept

Author keywords

[No Author keywords available]

Indexed keywords

COMPLEXATION; HYDROGEN BONDS; PRECIPITATION (CHEMICAL);

EID: 0037065290     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja0207302     Document Type: Article
Times cited : (82)

References (75)
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    • For reviews of hydrogen-bonded assemblies see: (a) Conn, M. M.; Rebek, J., Jr. Chem. Rev. 1997, 97, 1647-1668.
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    • note
    • 3-isomer tends to increase with increasing solvent polarity.
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    • The one-dimensional aggregates formed in the gel samples may be ascribed to intermolecular pyridine-carboxylic acid interactions. For reviews of low-molecular-weight organogels see: (a) Van Esch. J.; Schoonbeek, F.; De Loose, M.; Veen, E. M.; Kellogg, R. M.; Feringa, B. L. Supramol. Sci. 1999, 6, 233-259. (b) Shinkai, S.; Murata, K. J. Mater. Chem. 1998, 8, 485-495. (c) Terech, P.; Weiss, R. G. Chem. Rev. 1997, 97, 3133-3159.
    • (1999) Supramol. Sci. , vol.6 , pp. 233-259
    • Van Esch, J.1    Schoonbeek, F.2    De Loose, M.3    Veen, E.M.4    Kellogg, R.M.5    Feringa, B.L.6
  • 62
    • 0000862877 scopus 로고    scopus 로고
    • The one-dimensional aggregates formed in the gel samples may be ascribed to intermolecular pyridine-carboxylic acid interactions. For reviews of low-molecular-weight organogels see: (a) Van Esch. J.; Schoonbeek, F.; De Loose, M.; Veen, E. M.; Kellogg, R. M.; Feringa, B. L. Supramol. Sci. 1999, 6, 233-259. (b) Shinkai, S.; Murata, K. J. Mater. Chem. 1998, 8, 485-495. (c) Terech, P.; Weiss, R. G. Chem. Rev. 1997, 97, 3133-3159.
    • (1998) J. Mater. Chem. , vol.8 , pp. 485-495
    • Shinkai, S.1    Murata, K.2
  • 63
    • 0001629673 scopus 로고    scopus 로고
    • The one-dimensional aggregates formed in the gel samples may be ascribed to intermolecular pyridine-carboxylic acid interactions. For reviews of low-molecular-weight organogels see: (a) Van Esch. J.; Schoonbeek, F.; De Loose, M.; Veen, E. M.; Kellogg, R. M.; Feringa, B. L. Supramol. Sci. 1999, 6, 233-259. (b) Shinkai, S.; Murata, K. J. Mater. Chem. 1998, 8, 485-495. (c) Terech, P.; Weiss, R. G. Chem. Rev. 1997, 97, 3133-3159.
    • (1997) Chem. Rev. , vol.97 , pp. 3133-3159
    • Terech, P.1    Weiss, R.G.2
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    • Job, A. Ann. Chim. 1928, 9, 113-134.
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    • 2242424800 scopus 로고    scopus 로고
    • note
    • Reliable results could not be obtained from a Job plot for the complexation with L-3a because of solubility problems.
  • 68
    • 2242479584 scopus 로고    scopus 로고
    • note
    • In the titrations, we could not directly estimate the saturated CD intensity, because upon the addition of >2.4 equiv of L-3a, trace amounts of precipitates were formed making it difficult to obtain reliable CD values. Further, upon addition of >2.7 equiv of L-3b, the CD intensity slightly decreased because of the dissociation of the assembly (Figure 6). Therefore, the CD intensities at 306 nm were corrected on the basis of the linear plots with the de values (correlation coefficients, 0.997 for L-3a and 0.998 for L-3b. see supporting data), from which the saturated CD intensities can be estimated as ∼65.1 mdeg for L-3a and 21.8 mdeg for L-3b (see supporting data). For the linear plots, we assumed that the magnitude of the induced CD for the three CD-active species (1: 1, 1:2, and 1:3 complexes) is roughly the same (for details see ref 17). Thus, the calculated CD intensities include large error. The solubility problem could not be improved using n-octadecyl-CYA bearing a more soluble functionality.
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    • 3OD) of the precipitate indicated the 1:1 ratio of EDA: L-3a. The CHN and CHCOO signals in EDA·L-3a shifted downfield (δ 3.17 ppm, Δδ +0.5 ppm) and upfield (δ 5.77 ppm, Δδ -0.19 ppm), respectively, compared to those of free EDA and L-3a (see: Zingg. S. P.; Arnett, E. M.; McPhail, A. T.; Bothner-By, A. A.; Gilkerson, W. R. J. Am. Chem. Soc. 1988, 110. 1565-1580). Elemental analysis of the precipitate satisfied the 1:1 stoichiometry.
    • (1988) J. Am. Chem. Soc. , vol.110 , pp. 1565-1580
    • Zingg, S.P.1    Arnett, E.M.2    McPhail, A.T.3    Bothner-By, A.A.4    Gilkerson, W.R.5
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    • note
    • 6.
  • 72
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    • note
    • Although under condition A a trace amount of precipitate (diastereomeric assembly) was formed after the addition of L-3a, the precipitate redissolved in toluene after the subsequent addition of EDA. Judging from the similar results under conditions A and B (Figure 9c and 9b), there is no need to consider this precipitate.
  • 73
    • 2242427402 scopus 로고    scopus 로고
    • note
    • Although the previous memory system has the advantage of (i) exchange in a more apolar solvent (benzene) and (ii) stabilization by the nitro groups attached on calixarene-benzene rings (for detail see ref 15), the present system has a higher kinetic stability.
  • 74
    • 2242472366 scopus 로고    scopus 로고
    • note
    • The P- and M-interconversion process is slow on the NMR time scale, as indicated by the separated signals corresponding to the P- and M-isomers. In contrast, the pyridine-carboxylic acid exchange process is quite rapid because we observed only an averaged spectrum of 1:0, 1:1, 1:2, and 1:3 complexes of each P- and M-isomer.
  • 75
    • 2242463391 scopus 로고    scopus 로고
    • note
    • By increasing the temperature, the trend inverted (Table 5). At 60 °C, a slow interconversion was observed under the condition X (2.1 equiv of L-3a), suggesting that at higher temperature the P- and M-interconversion involves both the catalyzed and uncatalyzed pathways.


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