- Cucurbit[n]uril formation proceeds by step-growth cyclo-oligomerization
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In contrast to the high yield formation of cucurbit[n]uril (CB[n]) from a 1:2 ratio of glycoluril to formaldehyde, the condensation of glycoluril with less than 2 equiv of formaldehyde delivers a reaction mixture that contains glycoluril oligomers (2-6) and CB[n] compounds that lack one or more methylene bridges known as nor-seco-cucurbit[n]urils (ns-CB[n]). In this paper we report the chromatographic purification of C-shaped glycoluril oligomers (dimer-hexamer), their characterization in solution, and their X-ray crystal structures. Quite interestingly, despite being acyclic glycoluril pentamer 5 and hexamer 6 retain the ability to bind to guests typical of CB[6] but are also able to expand their cavity to accommodate larger guests like cationic adamantane derivatives. We performed product resubmission experiments with glycoluril oligomers 2-6 and found preferences for the formation of specific ring sizes during CB[n] formation. A comprehensive mechanistic scheme is proposed that accounts for the observed formation of 2-6 and ns-CB[n]. Overall, the experiments establish that a step-growth cyclo-oligomerization process operates during CB[n] formation.
- Huang, Wei-Hao,Zavalij, Peter Y.,Isaacs, Lyle
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- Supramolecular assembly of poly(ionic liquid) nanogel driven by host-stabilized charge transfer interaction
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Poly(ionic liquid) (PIL)-based nanogels, functionalized by naphthyl (Np), are fabricated via a facile one-step ternary crosslinking copolymerization in selective solvent. The size of PIL nanogels can be conveniently regulated through the feed ratio of IL monomer to crosslinker. The presence of Np groups in PIL nanogel is confirmed by using ultraviolet–visible (UV–vis), Fourier transform infrared, and X-ray photoelectron spectroscopy measurements. Through introducing cucurbit[8]uril (CB[8]) and bisviologen compound (DEDV) as the host molecule and electron acceptor, respectively, host-stabilized charge transfer (HSCT) interaction is achieved through utilizing Np containing PIL nanogel as the building block. The studies reveal that PIL nanogels can form schistose aggregates in the scale of micrometer via HSCT interaction. The aggregates will be broken in the presence a competitive guest molecule (amantadine) and can recover by adding another host molecule (CB[7]). HSCT interaction among CB[8], DEDV and PIL nanogel is investigated by dynamic light scattering, UV–vis, and Proton nuclear magnetic resonance. Our studies thus provided an applicable strategy for constructing dynamic polymer nanoparticles through noncovalent interaction.
- Tang, Yuntao,Wang, Ke,Zuo, Yong,Chen, Xi,Xiong, Yubing,Yuan, Yumin
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- Mechanism of the conversion of inverted CB[6] to CB[6]
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(Figure Presented) Inverted cucurbit[n]urils (iCB[n]) form as intermediates during the synthesis of cucurbit[n]urils from glycoluril and formaldehyde in HCl (85°C). Product resubmission experiments establish that the diastereomeric iCB[6] and iCB[7] are kinetic products that are less stable thermodynamically than CB[6] or CB[7] (>2.8 kcal mol-1). When iCB[6] or iCB[7] is heated under aqueous acidic conditions, a preference for ring contraction is noted in the formation of CB[5] and CB[6], respectively. Interestingly, under anhydrous acidic conditions ring size is preserved with iCB[6] delivering CB[6] cleanly. To establish the intramolecular nature of the iCB[6] to CB[6] conversion under anhydrous, but not aqueous, acidic conditions we performed crossover experiments involving mixtures of iCB[6] and its 13C=O labeled isotopomer 13C12-iCB[6]. An unusual diastereomeric CB[6] with a Moebius geometry (13) is proposed as a mechanistic intermediate in the conversion of iCB[6] to CB[6] under anhydrous acidic conditions. The improved mechanistic understanding provided by this study suggests improved routes to CB[n]-type compounds.
- Liu, Simin,Kim, Kimoon,Isaacs, Lyle
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- Controlling factors in the synthesis of cucurbituril and its homologues
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The acid-catalyzed synthesis of cucurbit[n]urils from formaldehyde and glycoluril is poorly understood. In this paper, we examine a wide range of reaction conditions that include the effects of acid type, acid concentration, reactant concentrations, and temperature to both probe the mechanism and optimize the yields of isolated cucurbit[n]urils, where n = 5-10. A mechanism for the formation of these cucurbit[n]urils is presented. Individual cucurbit[n]urils were unambiguously identified in reaction mixtures using ESMS and 13C NMR.
- Day, Anthony,Arnold, Alan P.,Blanch, Rodney J.,Snushall, Barry
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- PROCESS FOR THE PREPARATION OF CUCURBITURIL DERIVATIVES
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This invention relates to cucurbituril and/or one or more derivatives thereof with low formaldehyde content, to a process of manufacturing said cucurbituril and/or one or more derivatives thereof and to the use of said cucurbituril and/or one or more derivatives thereof, in particular in consumer and industrial products, and in industrial processes.
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Page/Page column 14; 15
(2018/07/22)
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- Cucurbituril derivatives, their preparation methods and uses
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Cucurbituril derivatives, their preparation methods and uses. The cucurbituril derivatives have the formula (1) where X is O, S or NH; R1and R2are independently selected from the group consisting of hydrogen, alkyl groups of 1 to 30 carbon atoms, alkenyl groups of 1 to 30 carbon atoms, alkynyl groups of 1 to 30 carbon atoms, alkylthio groups of 1 to 30 carbon atoms, alkylcarboxyl groups of 1 to 30 carbon atoms, hydroxyalkyl groups of 1 to 30 carbon atoms, alkylsilyl groups of 1 to 30 carbon atoms, alkoxy groups of 1 to 30 carbon atoms, haloalkyl groups of 1 to 30 carbon atoms, nitro group, alkylamine groups of 1 to 30 carbon atoms, amine group, aminoalkyl groups of 1 to 30 carbon atoms, unsubstituted cycloalkyl groups of 5 to 30 carbon atoms, cycloalkyl groups of 4 to 30 carbon atoms with hetero atoms, unsubstituted aryl groups of 6 to 30 carbon atoms, and aryl groups of 6 to 30 carbon atoms with hetero atoms; and n is an integer from 4 to 20, wherein the cucurbituril derivatives having the formula (1), where n=6, R1=H, R2=H and X=O, and n=5, R1=CH3, R2=H and X=O, are excluded. The cucurbituril derivatives are easily prepared as a mixture by one of the three new methods, and each cucurbituril derivative can be separated from the mixture by fractional crystallization. The cucurbituril derivatives having the formula (1) or their mixtures are very useful in removing dyes and heavy metal ions dissolved in water or waste water.
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