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Volumn 130, Issue 26, 2008, Pages 8446-8454

Cucurbit[n]uril formation proceeds by step-growth cyclo-oligomerization

Author keywords

[No Author keywords available]

Indexed keywords

ARSENIC COMPOUNDS; CHLORINE COMPOUNDS; CONDENSATION REACTIONS; EXPERIMENTS; FORMALDEHYDE; OLIGOMERIZATION; OLIGOMERS; POLYMERS;

EID: 46049105314     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja8013693     Document Type: Article
Times cited : (96)

References (75)
  • 50
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    • (b) Flory, P. J. Chem. Rev. 1946, 39, 137-197.
    • (1946) Chem. Rev , vol.39 , pp. 137-197
    • Flory, P.J.1
  • 52
    • 46049083175 scopus 로고    scopus 로고
    • Previous reports have referred to the product of the initial stage of Behrend's synthesis of CB[n, aq. HCl, 100°C, 3 equiv of formaldehyde as Behrend's polymer. The results reported in this paper suggest that this substance may, in fact, consist of a mixture of glycoluril oligomers, nor-seco-CB[n, and other kinetically controlled intermediates in the mechanism of CB[n] formation
    • Previous reports have referred to the product of the initial stage of Behrend's synthesis of CB[n] (aq. HCl, 100°C, 3 equiv of formaldehyde) as "Behrend's polymer". The results reported in this paper suggest that this substance may, in fact, consist of a mixture of glycoluril oligomers, nor-seco-CB[n], and other kinetically controlled intermediates in the mechanism of CB[n] formation.
  • 54
    • 46049104654 scopus 로고    scopus 로고
    • The influence of glycoluril concentration, acid identity and concentration and temperature have also been studied by Day and co-workers. The point in the mechanistic pathway where these variable exert their influence remains unclear
    • The influence of glycoluril concentration, acid identity and concentration and temperature have also been studied by Day and co-workers. The point in the mechanistic pathway where these variable exert their influence remains unclear.
  • 56
    • 15944379998 scopus 로고    scopus 로고
    • Zhao, Y.; Xue, S.; Zhu, Q.; Tao, Z.; Zhang, J.; Wei, Z.; L., L.; Hu, M.; Xiao, H.; Day, A. I. Chin. Sci. Bull. 2004, 49, 1111-1116.
    • (b) Zhao, Y.; Xue, S.; Zhu, Q.; Tao, Z.; Zhang, J.; Wei, Z.; L., L.; Hu, M.; Xiao, H.; Day, A. I. Chin. Sci. Bull. 2004, 49, 1111-1116.
  • 57
    • 46049100738 scopus 로고    scopus 로고
    • In addition to oligomers 2-6, bis-ns-CB[10, ±-bis-ns-CB[6, and ns-CB[6] the crude reaction mixtures typically contain some CB[6] and CB[7, We have been unsuccessful in developing an HPLC method to more precisely quantify the components of the reaction mixture for several reasons including (1) incompatibility of silica gel with the aq acid required for solubility, 2) irreversible adsorption during Dowex ion-exchange chromatography, and (3) lack of a convenient chromophore for detection
    • In addition to oligomers 2-6, bis-ns-CB[10], (±)-bis-ns-CB[6], and ns-CB[6] the crude reaction mixtures typically contain some CB[6] and CB[7]. We have been unsuccessful in developing an HPLC method to more precisely quantify the components of the reaction mixture for several reasons including (1) incompatibility of silica gel with the aq acid required for solubility, (2) irreversible adsorption during Dowex ion-exchange chromatography, and (3) lack of a convenient chromophore for detection.
  • 62
    • 46049111384 scopus 로고    scopus 로고
    • The formation of CB[10]·CB[5] and the gelation of purified CB[7] provide evidence for the (self)-association of CB[n] in aqueous solution. Although the presented x-ray structure is a solid state structure we find it highly likely that glycoluril oligomers will also undergo (self)-association in aqueous solution.
    • The formation of CB[10]·CB[5] and the gelation of purified CB[7] provide evidence for the (self)-association of CB[n] in aqueous solution. Although the presented x-ray structure is a solid state structure we find it highly likely that glycoluril oligomers will also undergo (self)-association in aqueous solution.
  • 65
    • 46049113458 scopus 로고    scopus 로고
    • The isolation of 2-6, bis-ns-CB[10], (±)-bis-ns- CB[6], and ns-CB[6] from reaction mixtures containing a deficiency of formaldehyde was possible because this stoichiometric imbalance slows down their transformation to the thermodynamically more stable CB[n]. In particular, the precipitation of certain compounds (e.g. bis-ns-CB[10]) from the reaction mixture can result in significant kinetic stability.
    • The isolation of 2-6, bis-ns-CB[10], (±)-bis-ns- CB[6], and ns-CB[6] from reaction mixtures containing a deficiency of formaldehyde was possible because this stoichiometric imbalance slows down their transformation to the thermodynamically more stable CB[n]. In particular, the precipitation of certain compounds (e.g. bis-ns-CB[10]) from the reaction mixture can result in significant kinetic stability.
  • 66
    • 46049094344 scopus 로고    scopus 로고
    • Compounds 13(m,n) and 17(m,n) are chiral when m ≠ n.
    • Compounds 13(m,n) and 17(m,n) are chiral when m ≠ n.
  • 67
    • 46049119584 scopus 로고    scopus 로고
    • 1H NMR spectroscopy is challenging.
    • 1H NMR spectroscopy is challenging.
  • 68
    • 46049088079 scopus 로고    scopus 로고
    • This analysis is theoretically based and ignores the potential influence of strain and intramolecular NH⋯O H-bonds that are known to impact the stability and geometry of CB[n] and (±)-bis-ns-CB[6
    • This analysis is theoretically based and ignores the potential influence of strain and intramolecular NH⋯O H-bonds that are known to impact the stability and geometry of CB[n] and (±)-bis-ns-CB[6].
  • 70
    • 46049114028 scopus 로고    scopus 로고
    • In none of these reactions did we observe the formation of CB[10]·CB[5] which suggests that the formation of this aggregate is probably more complex than the reaction of two molecules of 5 to give CB[10] followed by stabilization with CB[5].
    • In none of these reactions did we observe the formation of CB[10]·CB[5] which suggests that the formation of this aggregate is probably more complex than the reaction of two molecules of 5 to give CB[10] followed by stabilization with CB[5].
  • 71
    • 46049112642 scopus 로고    scopus 로고
    • Day has previously shown that CB[n] forming reactions when conducted at high dilution lead mainly to CB[5]. At high dilution intermolecular reactions are slowed and chain-growth rather than step-growth processes tend to dominate.
    • Day has previously shown that CB[n] forming reactions when conducted at high dilution lead mainly to CB[5]. At high dilution intermolecular reactions are slowed and chain-growth rather than step-growth processes tend to dominate.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.