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

Abstract

Sulfide-functionalized bambus[4]urils ((RS) BU[4]) and bambus[6]urils ((RS) BU[6]) were synthesized through thiol-ene click coupling reactions (TEC) of allylbambus[n]urils. Thiosugars were grafted to BU[4] and BU[6]. Synthesis of BU[6] derivatives always requires the use of a template anion (iodide, chloride, or bromide), which is enclosed in the cavity of BU[6]. We show that this anion influences the reactivity of bambus[6]urils. An encapsulated iodide makes allyl functions of allyl BU[6] less reactive towards TEC and hydrogenation reactions in comparison to the corresponding chloride or bromide inclusion complexes. This is critical for the chemical reactivity of BU[6] and even more to determine their anion-binding properties. We report a new, facile and fast method using AgSbF to prepare anion-free BU[6]. NMR spectroscopic methods were used to estimate association constants of these new empty BU[6] with different anions. Quantum chemical calculations were employed to rationalize the observed results. These new functionalized bambusuril scaffolds in alternate conformations could find applications as multivalent binders.

Formation and trapping of the thermodynamically unfavoured inverted-hemicucurbit[6]uril

“…The parent compounds, double-bridged cucurbiturils (CBs), 7,[19][20][21][22] are also synthesized in a single step, but the product distribution is not as efficiently influenced by the addition of templates 23 . Currently, four- [24][25][26][27][28][29] , six-, eight- 30 and twelve 16 -membered HCs are known, with the largest variation in substituents achieved for the six-membered 16,[24][25][26][27][28][29][31][32][33][34][35] HCs. The cavity shape and electronic structure of HCs vary, leading to distinct applications in host-guest systems [36][37][38][39][40][41][42][43][44][45][46][47][48] .…”

Formation and Trapping of the Thermodynamically Unfavoured Inverted-Hemicucurbit[6]uril

“…The parent compounds, double-bridged cucurbiturils (CBs), 7,[19][20][21][22] are also synthesized in a single step, but the product distribution is not as efficiently influenced by the addition of templates 23 . Currently, four- [24][25][26][27][28][29] , six-, eight-30 and twelve 16 -membered HCs are known, with the largest variation in substituents achieved for the six-membered 16,[24][25][26][27][28][29][31][32][33][34][35] HCs. The cavity shape and electronic structure of HCs vary, leading to distinct applications in host-guest systems [36][37][38][39][40][41][42][43][44][45][46][47][48] .…”

Cucurbit[5]uril derivatives as oxygen carriers

“…These optimized cucurbiturils may complement another molecule able to bind bicarbonate, produced from the waste product CO2. Bambusurils, made of glycoluril units as cucurbiturils, are known to efficiently bind anions in water (47), and it has been shown that they can be functionalized (48,49). Together, a cucurbituril and a bambusuril may therefore be the major constituents of a haemoglobin substitute solution.…”