259886-49-2Relevant articles and documents
Cucurbit[n]uril formation proceeds by step-growth cyclo-oligomerization
Huang, Wei-Hao,Zavalij, Peter Y.,Isaacs, Lyle
, p. 8446 - 8454 (2008)
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.
Mechanism of the conversion of inverted CB[6] to CB[6]
Liu, Simin,Kim, Kimoon,Isaacs, Lyle
, p. 6840 - 6847 (2007)
(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.
PROCESS FOR THE PREPARATION OF CUCURBITURIL DERIVATIVES
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Page/Page column 14; 15, (2018/07/22)
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.
