Calix arene sulfonates

Some of calix[ ]arene sulfonic acids were also developed as Bronsted acid catalysts for Mannich-type reactions [23]. Because of their water-solubility, the reaction can be performed in water with obvious advantages from an environmentally point of view. As depicted in Fig. 27.8, two water soluble calixarene bearing a sulphonic acid group are suitably employed in the Mannich reaction in water as a catalyst. 

The specific structure of [(H20)5Ni(py)]2+ was observed in the complexes with the second-sphere coordination of calix[4]arene sulfonate.715 There are two different [(H20)5Ni(py)]2+ cations in the complex assembly. In one the hydrophobic pyridine ring is buried in the hydrophobic cavity of the calixarene with the depth of penetration into the calixarene cavity being 4.3 A (Figure 9). The second independent [(H20)5Ni(py)]2+ cation is intercalated into the calixarene bilayer. 

Figure 9 Complex assembly of [(H20)5Ni(py)]2+ and calix[4]arene sulfonate.715...

Calixarene-based M5 [calix[4]arene sulfonates] vH20 (M = Na x= 12) K (v = 8) Rb (x = 5) Cs (x = 4J) have been used to construct supramolecular assemblies. They have been structurally characterized, and exist as bilayers of anionic truncated pyramids in the cone configuration ... 

Na8 calix[6]arene sulfonate which shows no preorganization into a pseudo-planar hexacoordinate structure. 

Organic Clays. Synthesis and Structure of Na5[calix[4]arene sulfonate] 12 H2O, K5[calix[4]arene sulfonate]-8 H2O, Rb5[calix[4]arene sulfonate]-5 H2O, and Cs5[calix[4]arene sulfonate] 4 H2O... 

In a typical synthesis, 10.0 g (0.024 mol) of the [calix[4]arene, R = —H and R = —H, were reacted with an excess of H2SO4 at 60°C for 3 h. This was followed by neutralization with BaC03 and the addition of Na2C03 to pH 9. The solvent is removed and the compound is recrystallized from water. The overall yield is 15.2 g Na5[calix[4]arene sulfonate] T2 H2O, 60%. Large, colorless crystals of the compound may be obtained by slow evaporation. 

X-RAY DATA COLLECTION AND STRUCTURE DETERMINATION FOR Na5[CALIX[4]ARENE SULFONATE] 12 H2O... 

XARENE Table I. SULFONATE ORGANIC Final fractional coordinates CLAYS for Na5[calix[4]arene sulfonate] T2 H2O 205... 

Table II. Final fractional coordinates for K5[calix[4]arene sulfonate]-8 H2O.

The calix[4]arene sulfonates of the alkali metals all exist as 5— anions at neutral pH. The four protons of the sulfonate groups have been removed, as has one from the hydroxyls [21]. The resulting 5— anion exists in the cone configuration which is stabilized by the hydrogen bonding shown in Figure 1. 

A in smectite [23] and 15.0 A in hydrated sodium vermiculite [24]. Second, the hydrated layer in sodium vermiculite is 9.4 A, while the inorganic layer in Na5[calix[4]arene sulfonate] 12 H2O is 8.3 A. A more complete comparison has been presented [19]. 

The chemical behavior of clays is also mimicked by the title complexes in two respects the presence of cation-exhange capabilities and the reduced water content in the ammonium salt [20]. Currently, other similarities between clays and the water-soluble calixarenes are being probed. In particular, the size- and polarity-selective cavity of the calix[4]arene sulfonates is finding utility in the separation of organic substances, cations, anions, and neutral molecules, from aqueous feed streams. 

Atwood, J. L., A. W. Coleman, H. Zhang, and S. G. Bott - Organic clays. Synthesis and stmcture of M [calix[4]arene sulfonate] hydrates 203... 

The Povarov cascade reaction of an aniline, two moles of formaldehyde and two moles of styrene gives tricyclic (51). ° Calix[4]- and calix[6]-arene sulfonic acids have been... 

Fig. 24.31 Left Qiemical structures of calix[6]- and calix[8]-arene sulfonates 78 and 79. Right IC50 values for 78 and 79 acting on the restriction enzyme Nrul. Gel electrophoresis was used to determine the activity of the enzyme in the presence of increasing concentrations of inhibitor [99]. (Reprinted from Ref. [99])...

In an outstanding study, calix[6]arene sulfonic acids (Calix[6]arene 3a-3d) were employed as efficient surfactant-type acid catalysts for Michael reactions of indoles with a,p-unsaturated ketones in water [24]. It was pointed out that calix[6] arene sulfonic acids were efficient inverse phase-transfer catalysts, and performed a significant catalytic activity in water (see Fig. 27.10). This remarkable activity in... 

Fig. 27.10 Michael reaction of indole with chalcone in the presence of calix[6]arene sulfonic acids...

Yosida et al. [41] found that p-t< rr-butylcalix[6]ar-ene can extract Cu from the alkaline-ammonia solution to the organic solvent. Nagasaki and Shinkai [42] described the synthesis of carboxyl, derivatives of calix-[n]arenes ( = 4 and 6) and their selective extraction capacity of transition metal cations from aqueous phase to the organic phase. Gutsche and Nam [43] have synthesized various substituted calix[n]arenes and examined the complexes of the p-bromo benzene sulfonate of p-(2-aminoethyl)calix[4]arene with Ni, Cu , Co-, and Fe. ... 

M. Vazquez, J. Bobacka, M. Luostarinen, K. Rissanen, A. Lewenstam, and A. Ivaska, Potentiometric sensors based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with sulfonated calix[4]arene and calix[4]resorcarenes. J. Solid State Electrochem. 9, 312-319 (2005). 

It had been reported that fullerene Cgo forms a water-soluble complex with y-cyclodextrin by heating with an excess amount of y-cyclodextrin in water [10] or in a mixture of refluxing water and toluene for a long time, such as 30 h [ 11]. The isolated complex is considered to have the Cgo structure bicapped with y-cyclodextrin in a molar ratio of 1 2 [11], and the complex dissolved in water to give a solution of C o with a concentration of nearly 10 mol L 410,11 ]. Fullerene Qo was also solubilized in water by complexation with a sulfocalix[8] arene, i.e., calix-[8]aryloxy-49,50,51,52,53,54,55,56-octakis(propane-3-sulfonate). The concentration of this complex in water is estimated as 5x10 mol L [12]. Complex formation between fullerene and various calixarenes has also been reported [8]. 

The sulfonated calix[8]arene 27 (Structures 8), which can be viewed as a simplified y-CD with the carbohydrate backbone replaced by an aryl moiety, mimicked heparin in the stimulation of heparan sulfate synthesis from cultured endothelial cells [62]. 

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