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Calix pyrroles synthesis

F.H. Kohnke and co-workers prepared novel heterocyclophanes from cyclic poly-1,4-diketones, which were obtained by the oxidation of calix[6]furan and calix[4]furan. " One of the heterocyclophanes, calix[6]pyrrole, was prepared by the Paal-Knorr pyrrole synthesis from the corresponding dodecaketone. The substrate was heated with excess ammonium acetate in absolute ethanol. Interestingly, the analogous synthesis of calix[4]pyrrole under identical conditions failed, while calix[5]pyrrole is obtained only in 1% yield. [Pg.329]

A more recent development has been the synthesis of bisamidopyrrolylmethane based anion receptor systems (Figure 19).15 These receptors might be regarded as containing half a calix[4]pyrrole combined with die 2-amido appendages in common with the pyrrolic amide cleft. Compounds 19 and 20 were synthesized by reaction of diethyl-5,5 -methylenebis(4-ethyl-3-methyl-2-pyrrole) carboxylate with aniline or n-butylamine in the presence of trimethylaluminium in dry dichloromethane at 35°C in 40 and 43% respective yields. [Pg.162]

Undoubtedly, the future will bring further progress in this area and more developments on the synthesis of calix[4]pyrrole anion receptors. However, the design of anion receptors is still a challenging task. [Pg.117]

Other interesting new developments in pyrrole chemistry encompass the synthesis of calix[6]pyrrole and calix[ ]furan[m]pyrroles, where m + n = 6 <02CEJ3148>, and the formation of cyclo[8]pyrroles from 2,2 -bipyrrole fragments <02AGE1422>. [Pg.148]

As with the multi-species components, it is not necessary for hydrogen bonding to be used in order to form dimeric capsules. This is highlighted by the recent synthesis of a molecule which assembles into dimers that are held together by n-interactions [137]. The meso-hexaphenyl calix[6]pyrrole 59 assembles into a dimeric capsule via the interactions between six phenyl groups arranged in a central belt around the capsule. The capsule is capable of holding two molecules of chloroform simultaneously, as seen in the solid state structure (Fig. 51). Similar phenyl interactions have been observed in ap-phenylcalix[5]arene which has been shown to dimerise and include C60 within its cavity (Fig. 52) [138]. [Pg.146]

A highly reactive uranium complex supported by the Et8-calix-[4]-tetrapyrrole tetraanion ligand has been reported. The compound was found to effect dinitrogen cleavage, solvent desoxygenation, and polysilanol depolymerization. These compounds are mentioned here because they involve 7r-bonding interactions between the pyrrole units and the uranium centers.142,142a The synthesis of a series of mono- and bis(tmp)uranium (tmp = tetramethylphospholyl) complexes has been reported. The synthetic procedures are illustrated in Scheme 72.132... [Pg.224]

In 2000 Kohnke and co-workers described the synthesis of meso-octame-thylcalix(6]pyrrole via the conversion of calix[6]furan into dodecaketone, which was then treated with ammonium acetate to obtain calix[6]pyrrole 50 [67]. [Pg.28]

Anzenbacher, P. Jursikova, K. Lynch. V.M. Gale. P.A. Sessler. J.L. Calix[4]pyrroles containing deep cavities and fixed walls. Synthesis structural studies, and anion binding properties of the isomeric products derived from the condensation of p-hydroxyacetophenone and pyrrole. J. Am. Chern. Soc. 1999, 121. 11020. [Pg.160]

In 1999, Sessler and coworkers and, independently, Floriani and coworkers, reported the synthesis of deep-cavity calixpyn oles (e.g., 13) formed from the condensation of 4-hydroxyacetophenone and pyrrole.The aococa-isomer of this species may be isolated by column chromatography or by fractional crystallization. Gale and coworkers recently reported the synthesis of super-extended cavity calix[4]pyrroles 14 and 15 in which the selectivity for fluoride is considerably increased in DMSO solution. No other anion is bound in this solvent, even in high concentrations (i.e., substoichiometric quantities of fluoride are bound in the presence of 100 equivalents of chloride that do not interact with the receptor). [Pg.1179]

In contrast to what is true in the case of the non-fluorinated calix[/2]pyrroles v/here it has proven difficult to isolate species with n> A. the synthesis of Compound 12 led to the two isolable and kinetically stable higher-order... [Pg.1179]

Other approaches to the synthesis of higher-order calixpyrroles were pursued. For instance, the synthesis of m. yo-dodecamethylcalix[6]pyrrole 18 from the previously known furan-based analogue was reported by Kohnke and coworkers. "" This higher-order calixpyrrole was found to be a better receptor for chloride than the corresponding m yo-octamethylcalix[4]pyrrole 11, probably due to the larger core size of the macrocycle. Transport experiments from an aqueous solution to a DCM solution also revealed Compound 18 to be ca. 10 times more selective for chloride anion than Compound 11. Meanwhile, Eichen used a step-wise procedure to prepare the calix [6]pyrrole 19 and demonstrated that it shows a selectivity for larger anions. Specifically, H-NMR titration experiments carried out in acetonitrile-chloroform (1 9) revealed that this system shows a preference for iodide anion over the other halides. [Pg.1180]

Gale, P.A. Bleasdale. E.R. Chen, G.Z. Synthesis and electrochemical polymerisation of calix[4]pyrroles con- 30. taining TV-substituted pyiTole moieties. Supramol. Chem. [Pg.1185]

Sessler. J.L. Anzenbacher, P., Jr. Shrives. J.A. Jursikova, 38. K. Lynch, V. Marquez, M. Direct synthesis of expanded fluorinated calix[/r]pyrroles Decafluorocalix[5]pyrrole... [Pg.1185]

Today it is possible to synthesize calix[ ]arenes with 4 < n < 11However, this is not the case for calixpyrroles. Indeed, before recent work in this area by Sessler et al caIix[n]pyrroles with n>4 were (apparently) unknown. It was quickly found that such species were often byproducts of condensations leading to the generation of calix[4)pyrroles, and that they were difficult to isolate cleanly. Therefore a template-type. strategy was explored that might allow the synthesis and isolation of a higher-order calixpyrrole. To test this strategy, p-fcrf-butylcalix[4]arene tetramethyl ketone was condensed with pyrrole in the presence of methanesulfonic acid. This afforded the cylindrical calix[4]arene-calix[4]pyrrole pseudo dimer 18 in 32% yield. [Pg.271]

Figure 24. h NMR spectrum of compound 18 recorded in dichloromethane-d2. The pyrrole-NH protons are deshielded and resonate at 11.22 ppm, a finding that is consistent with the formation of hydrogen bonds. (Reprinted from Tetrahedron Letters, Gale, P. A. Sessler,). L. Lynch, V. Sansom, P. I., "Synthesis of a New Cylindrical Calix(4]arene-Calix(4]pyrrole Pseudo Dimer," 1996, 37, 7881 -7884. Copyright 1996, with permission from Elsevier Science.)... [Pg.272]

A very versatile and easy entry into the chemistry of calixpyridines, recently reported, is predicated on the use of calixpyrroles as starting materials. This route, illustrated in Scheme 2, involves reaction of a calix[4]pyrrole with dichlorocarbene and provides a ready access into the previously unknown calix[3)pyridino[l]pyrrole and calix-[4]pyridine families. It also allows for the facile synthesis of calix[ I ]pyridino[3)pyrroles and calix(2Jpyridino[2Jpyr-roles, species that Floriani and coworkers have also produced from calix(4]pyrroles using alternative organo-metallic-based procedures. ... [Pg.272]

Scheme 2. Synthesis of chloro-derivatives of calixpyridinopyrroles 21, 22, and 23 and calix[4]pyridine 20 from meso-octamethylcalix[4]pyrrole using a carbene insertion strategy. The chlorine atoms may be attached to each pyridine ring either in position a or b. Scheme 2. Synthesis of chloro-derivatives of calixpyridinopyrroles 21, 22, and 23 and calix[4]pyridine 20 from meso-octamethylcalix[4]pyrrole using a carbene insertion strategy. The chlorine atoms may be attached to each pyridine ring either in position a or b.
The discovery of new calixpyrrole chemistry continues apace. Since this chapter was written, Eichen and coworkers have reported the synthesis of a calix[6]pyrrole and Aida... [Pg.276]

Novel Catalytic Method in Synthesis of Calix[4]pyrroles Using Preyssler and... [Pg.69]

A catalytic synthesis of calix[4]pyrroles and A-confused calix[4]pyrroles by reaction of dialkyl or cycloalkyl ketones with pyrrole was performed using Preyssler, sodium 30-tungsto pentaphosphate, [NaPjWjQOjjJ ", and Wells-Dawson HPAs as acidic catalysts. The process occurred under mild, eco-friendly, and environmentally friendly eonditions and as a reusable, green catalyst at room temperature for 6 h. The results showed that the yield for this synthesis is exeellent with the... [Pg.79]

Gharib A, Jahangir M, Roshani M (2012) A facile synthesis of calix[4]pyrroles using heteropolyacids as green, eco-fiiendly, reusable and reeyclable eatalyst. Bulg Chem Commun 44 (2) 113-117... [Pg.102]

Functionalization of the wso-positions has been achieved most conunonly via an acid-catalyzed condensation of a dipyrromethane, containing the group or moiety that is designed to assist in ion binding, with an excess of acetcme [1, 7]. One elegant embodiment of this approach involves so-called strapped calix[4]pyrroles here, a tethered bispyrromethane, the precursor to the strap , is used in the synthesis [8]. [Pg.286]

The synthesis of functionalized calix[4]pyrroles able to accommodate ion pairs within their cavities was first approached by using crown ether-like polyether straps to link two of the four meso-csxhon atoms of the calix[4]pyrrole framework. The first of such ditopic systems, receptor 7, reported by Kim, Sessler, and coworkers, was designed to contain a the calix[4]arene crown-6-moiety for cesium cation recognition, while retaining a calix[4]pyrrole subunit for anion recognition (cf. Fig. 12.6) [22]. In the solid state, the individual ions within the CsF ion pair complex, which are bound to 7, are separated from one another by a single methanol molecule that was presumably captured during crystallization. Proton NMR spectroscopic analyses, carried out in deuterated methanol/chloroform (1 9 vA ),... [Pg.290]

The flexible structure of calix[4]pyrrole possess coupled with their relative ease of synthesis and inherent affinities for anions have made this core structure a key building block in the creation of containers and capsules [76,78]. Examples of calix [4]pyrroles capsules and self-assembled systems are presented in a separate chapter in this book that is authored by the Tarragona group. Thus, only a brief description will be provided here to avoid redundancy. [Pg.312]

Limitations on the application of hydrogen bonded capsular assemblies come from the poor stability of these assemblies in polar media compared to those held by covalent bonds. In an attempt to overcome these Umitations, Bohmer described the synthesis of a mechanically locked chiral bis-catenane based on calixarene capsules [55]. Inspired by this pioneering work, our group produced a mechanically locked hybrid tetraurea calix[4]arene-calix[4]pyrrole capsule 30 (Fig. 32.14) [56]. This catenated capsule displayed reversible encapsulation (i.e. reversible assembly of the urea belt). The two hemispheres of the capsule never dissociate completely due to the bis-catenated topology. [Pg.862]


See other pages where Calix pyrroles synthesis is mentioned: [Pg.109]    [Pg.475]    [Pg.85]    [Pg.475]    [Pg.192]    [Pg.436]    [Pg.170]    [Pg.86]    [Pg.119]    [Pg.66]    [Pg.74]    [Pg.77]    [Pg.78]    [Pg.82]    [Pg.85]    [Pg.27]    [Pg.1180]    [Pg.1097]    [Pg.194]    [Pg.116]    [Pg.287]    [Pg.858]   
See also in sourсe #XX -- [ Pg.9 ]




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