Bambusurils Bearing Nitro Groups and Their Further Modifications

Abstract

Bambusurils are recently developed neutral anion receptors that show a high affinity towards many inorganic anions, not only in organic solvents but also in water. However, the number of water-soluble bambusurils and also those bearing functional groups is very limited. In this paper we report the synthesis of four-and six-membered bambusurils containing eight and twelve nitro groups. All the nitro groups on the bambusuril portals could be transformed into amino functions,

Intramolecular van der Waals Interactions Challenge Anion Binding in perthio‐Bambusurils

“…Thus, under these conditions cyclooligomerization of 9 a afforded 11 a (47 %) and 10 a (10 %) whereas the reaction with 9 b afforded 11 b (11 %) and 10 b (4 %) along with two byproducts, diether 12 (4 %) and dimer 13 (8 %) (see Supporting Information). Similar byproducts were reported earlier in the preparation of nitrobenzyl‐BUs …”

Functionalization of Bambusurils by a Thiol–Ene Click Reaction and a Facile Method for the Preparation of Anion‐Free Bambus[6]urils

“…Bambus[6]urils bearing benzoate or carboxylate substituents on their portal are known to be water‐soluble . Nitrobenzyl bambus[4]urils and bambus[6]urils were recently prepared in the group of Sindelar . Nitrobenzyl BU[4] derivatives have been successfully reduced into water‐soluble aminobenzyl BU[4] that were further transformed into the corresponding urea bambus[4]urils .…”

“…Nitrobenzyl bambus[4]urils and bambus[6]urils were recently prepared in the group of Sindelar . Nitrobenzyl BU[4] derivatives have been successfully reduced into water‐soluble aminobenzyl BU[4] that were further transformed into the corresponding urea bambus[4]urils . Bambus[6]urils containing 12 (ethylene glycol) functions were recently reported to be as soluble in water as in nonpolar solvents .…”

“…We have previously improved this synthesis with the use of microwave irradiation that significantly shortens the reaction times and increases the yields of bambusurils . These microwave conditions have also been successfully used by the groups of Keinan and Sindelar A templating anion is always required either using reflux or microwaves to promote the formation of the hexameric BU[6], in preference to the tetrameric BU[4]. Although this methodology has been well established, BU[6] derivatives are generally isolated with an anion present inside their cavity and time‐consuming steps are necessary to obtain anion‐free BU[6] …”

“…Interestingly the first nonsymmetrical BU[4] was very recently prepared by Sindelar . Apart from these few examples, the functionalization and reactivity of BUs are still poorly developed.…”