Microwave-assisted synthesis of 1,3-dialkyl ethers of calix[4]arenes: application to the synthesis of cesium selective calix[4]crown-6 ionophores

Partial etherification of phenolic-OH groups of calix[4]arenes with various alkyl halides/tosylates and K₂CO₃ under microwave irradiation afforded 1,3-dialkoxycalix[4]arenes in their cone conformation only as predominant/sole product in good yields (71–85%). The protocol was found to be much superior to conventional heating both in terms of yield and reaction time. Some of the 1,3-dialkoxycalix[4]arenes were elaborated further to the syntheses of cesium selective calix[4]crown-6 ionophores.     

Synthesis and anti-integrase evaluation of novel calix[4]arene derivatives containing the triazolyl 1,3-diketo moiety

A series of novel calix[4]arene derivatives incorporating two triazolyl 1 3-diketo subunits in alternate positions at the lower rim were synthesized and screened for HⅣ integrase inhibition activity.The chemical structures of these compounds were confirmed by means of1H NMR 13C NMR,and ESI-MS.Preliminary bioassays indicated that calix[4]arene derivatives proved to be more active than p-tertbutylcalix[4]arene derivatives.In particular,compound 4g presented the most potent integrase strand transfer inhibitory activity with an IC50value of 6.1 mmol/L.     

Cesium-ion selective electrodes based on calix[4]arene dibenzocrown ethers

Four calix[4]arene dibenzocrown ether compounds have been prepared and evaluated as Cs(+)-selective ligands in solvent polymeric membrane electrodes. The ionophores include 25,27-bis(1-propyloxy)calix[4]arene dibenzocrown-6 1, 25,27-bis(1-alkyloxy)calix[4]arene dibenzocrown-7s 2 and 3, and 25,27-bis(1-propyloxy)calix[4]arene dibenzocrown-8 4. For an ion-selective electrode (ISE) based on 1, the linear response concentration range is 1x10(-1) to 1x10(-6) M of Cs(+). Potentiometric selectivities of ISEs based on 1-4 for Cs(+) over other alkali metal cations, alkaline earth metal cations, and NH(4)(+) have been assessed. For 1-ISE, a remarkably high Cs(+)/Na(+) selectivity was observed, the selectivity coefficient (K(Cs,Na)(Pot)) being ca. 10(-5). As the size of crown ether ring is enlarged from crown-6 (1) to crown-7 (2 and 3) to crown-8 (4), the Cs(+) selectivity over other alkali metal cations, such as Na(+) and K(+), is reduced successively. Effects of membrane composition and pH in the aqueous solution upon the electrode properties are also discussed.     

Synthesis and crystal structure of p-acylated calix[4]arene ethers

C-acylation of calix[n]arenes is an important reaction which has been primarily utilized for their further functionalization to provide conformers with varying shapes, cavity dimensions and molecular receptor characteristics that can bind ionic and neutral species in a selective and specific manner. The length of the alkyl chain at the upper or the lower rim of calixarenes can be adjusted as required to give derivatives which can span the channels and membranes and majorly influence transport phenomenon. As a part of our program to obtain calixarene based derivatives that can span and scan artificial membranes, C-acylation of calix[4]arene has been examined to yield peracylated and partially acylated calixarene ethers. 5,11,17,23-Tetraacetyl-25,26,27,28-tetramethoxycalix[4]arene has been obtained in 80 % yield by treatment of tetramethoxycalix[4]arene with acetyl chloride in the presence of aluminum chloride using dichloromethane as the solvent. The structure was established by the conversion to corresponding phenyl hydrazones and oximes. The tetraacetyltetramethoxycalix[4]arene 2a crystallized in a monoclinic lattice, space group P2₁/C with a = 10.320(2) Å, b = 18.928(4) Å, c = 18.421(4) Å, β = 95.44(3)^o, Z = 4. The corresponding methyl substituted O7 directs inwards towards the cavities of calix[4]arene to give an inward flattened partial cone conformation. Molecular packing shows the presence of intermolecular C–H···O, H-bonding interactions between methyl and methylene hydrogens and oxygens of the acetyl groups.     

一种新型杯[4]芳烃的合成

本文通过对特丁基杯[4]芳烃的酚羟基烷基化和苯环特丁基位上的IPSO-硝化制备了一系列对硝基杯[4]芳烃烷基醚,烷基分别是n-C~4H~9(3a)、n-C~8H~1~7(3b)、n-C~1~2H~2~5(3c)和n-C~1~6H~3~3(3d)。^1HNMR表明所有新的杯[4]芳烃都具有锥形(cone)构象。     

Synthesis of novel calix[4]crown telomers and selective extraction of cesium ions

p-tert-Butylcalix[4]diazacrown-4 telomer, which contains hard and soft ion binding sites, was synthesized. It exhibited high selectivity toward cesium ions. The binding sites may complex alkali metal ions selectively.     

Synthesis of novel redox calix[4]arene derivative with 1,3-substituted large conjugated ferrocene bridge

A novel redox calix[4]arene derivative with 1,3-substituted large conjugated ferrocene bridge was designed and synthesized in high yield.Its structure was characterized by element analysis,IR,ESI-MS,NMR spectrum,etc.The primary study of cyclic voltammetry showed it possessed excellent reversible electrochemistry response property.     

Synthesis and self-assembly of novel calix[4]arenocrowns: formation of calix[4]areno[2]catenanes

A series of novel calix[4]arenocrowns 1a-c were efficiently synthesized by a one-pot reaction of calix[4]monohydroquinone diacetate 5 with ditosylate 6 and its analogues in the presence of sodium hydroxide. It was found that the calix[4]arenocrowns could form stable pseudorotaxane-type complexes 2a-c with paraquat, and further self-assemble into calix[4]areno[2]catenanes 3a-c with dicationic salt 8 and p-bis(bromomethyl)benzene.     

Shape recognition of alkylammonium ions by 1,3-bridged calix[5]arene crown-6 ethers: endo- vs exo-cavity complexation

A series of tri-O-substituted 1,3-bridged calix[5]arene crown-6 ethers bearing alkyl, arylalkyl, alkoxyalkyl, and alkoxycarbonylmethyl residues at the lower rim and either (t)()Bu or H substituents at the upper rim have been synthesized. (1)H NMR studies have shown that p-tert-butylcalix[5]crowns, irrespective of the size and nature of their lower rim pendant groups, adopt preorganized conelike conformations, whereas p-H-calix[5]crowns with bulky substituents preferentially exist in solution as partial cone conformers (C(1) symmetry). Calix[5]crown derivatives behave as mono- or ditopic receptors for isomeric butylammonium ions, forming endo-cavity (inside the calixarene cup) and/or exo-cavity (at the crown ether moiety) 1:1 complexes according to the shape of the guest. These two binding modes can be clearly distinguished and monitored by (1)H NMR titration experiments.     

Synthesis and crystal structures of novel calix[4]azacrowns

A series of novel 1,3‐altemate calix[4]arene azacrowns having mono and bis crown ethers on the lower rim of the calix[4]arene framework were synthesized. Solid‐state structures confirmed the three dimensional conformation of compounds 1–3.     

Stilbene-bridged 1,3-alternate calix[4]arene crown ether for selective alkali ion extraction

A series of stilbene-bridged calix[4]arenes was synthesized through an intramolecular reductive McMurry coupling of bisbenzaldehyde calix[4]arene in high yields. Tetra- and pentaethylene glycol chains were tethered to the phenolic groups of calix[4]arene to form stilbene-bridged calix[4]arene crown-5 and crown-6, respectively. The presence of stilbene bridge over the calix[4]arene rim effectively prevented the connection of the polyether chains in the cone conformation resulting in the exclusive formation of 1,3-alternate stilbene-bridged calix[4]arene crown product. Compared to the cone analogues, the 1,3-alternate calix[4]arene crown ethers showed a greater extraction ability and selectivity toward Cs⁺.     

Synthesis of novel calix[4]arenes containing organosilicon groups

Metalation of (RSiMe₂)₃CH (1a R = H, 1b R = Me, 1c R = Ph) with lithium diisopropylamide (LDA) or methyllithium in THF gave organolithium reagents (RSiMe₂)₃CLi, which reacted with the formylated calixarene (2), to give the corresponding 5,17-bis[2,2-bis(organosilyl)-1-ethenyl]-25,26,27,28-tetrapropoxycalix[4]arenes (3a, 3b and 3c) via the Peterson olefination. The compounds (RSiMe₂)₃CLi were treated with 25,26,27,28-tetrakis(4-bromobutoxy)calix[4]arene (4) to give 25,26,27,28-tetrakis[4-(tris(dimethylsilyl)methyl)butoxy] calix[4]arene (5a) and 25,26,27,28-tetrakis[4-(tris(trimethylsilyl)methyl)butoxy] calix[4]arene (5b) via nucleophilic substitution reactions. However the compound 25,26,27,28-tetrakis[4-(tris(dimethylphenylsilyl)methyl)butoxy] calix[4]arene (5c) was not obtained, presumably because (PhSiMe₂)₃C- is highly sterically hindered and the reactivity of its derivatives is low. The compound 5a has potential as a core for dendrimers.     

杯[4]芳烃单取代1,3-二酮衍生物的合成及生物活性研究

以杯[4]芳烃为原料经醚化和克莱森缩合两步反应首次合成杯[4]芳烃单取代1,3-二酮衍生物,其结构经1H NMR、13C NMR及MS表征。初步的HIV-1整合酶链转移反应活性测试结果表明,该杯[4]芳烃单取代1,3-二酮衍生物在测试浓度为25μM时其抑制率为12.67%。     

Synthesis of new calix[4]pyrrole derivatives via 1,3-dipolar cycloadditions

Octamethylcalix[4]pyrrole-2-carbaldehyde 1 and 3-(octamethylcalix[4]pyrrol-2-yl)propenal 5 were used as precursors of azomethine ylides, which were trapped in situ with a range of dipolarophiles, such as 1,4-benzoquinone, 1,4-naphthoquinone, and fumaronitrile. Aldehyde 1 showed very low reactivity but the azomethine ylide generated from the reaction of aldehyde 5 with N-methylglycine could be trapped with those dipolarophiles to afford new β-substituted octamethylcalix[4]pyrrole derivatives in moderate yields. The resulting cycloadducts show high affinity constants for fluoride and acetate anions; compounds 7 and 8 display sharp changes in color in the presence of these anions.     

Synthesis and evaluation of multitopic bisbenzothiazolyl calix[4]arenes for ionic toxicants

Abstract

Two new benzothiazolyl calix[4]arene-based multitopic molecular receptors L-1 and L-2 have been synthesised and evaluated for recognition of ionic toxicants. The receptors selectively interact with copper, silver and fluoride ion toxicants as assessed through UV-visible, NMR and colorimetric techniques. The stability of L-1:Cu⁺² and L-2:Cu⁺² complexes was found to be higher than that of complexes formed with Ag⁺ and F^– complexes in the presence of trifluoroacetic acid. Superiority of L-1 over L-2 for analysis of identified toxicants has been determined by measurement of binding constants.     

Synthesis of mono- and 1,3-diaminocalix[4]arenes via Ullmann-type amination and amidation of 1,3-bistriflate esters of calix[4]arenes

Practical methods are described for the preparation of monoamines 4 and 1,3-diamines 5, bearing one or two amino group(s) instead of the hydroxy group(s) at the 28-position or at both the 26- and 28-positions of p-tert-butylcalix[4]arene (1a) and p-tert-butylthiacalix[4]arene (1b), via the Ullmann-type amination or amidation. Thus, the copper-catalyzed or mediated amination of the 1,3-bistriflate ester (2a) of 1a with benzylamine affords either mono(benzylamino) triflate 7a or 1,3-bis(benzylamine) 8 in a high yield, depending on the reaction conditions. On the other hand, the 1,3-bistriflate ester (2b) of 1b resists disubstitution and produces, under stoichiometric conditions, mono(benzylamino) triflate 7b. The disubstitution of 2b is achieved by amidation with tosylamide, giving 1,3-bis(tosylamide) 17b. The hydrogenolysis of the benzylamino moiety of 7a, followed by the hydrolysis of the Tf moiety, affords monoamine 4a, while the hydrogenolysis of 8 affords 1,3-diamine 5a. The amino moiety of 7b can be deprotected under acidic conditions to give, after hydrolysis, monoamine 4b. The hydrolysis of 17b affords 1,3-diamine 5b. The overall yields of compounds 4a, 4b, 5a, and 5b are 72%, 45%, 78%, and 24%, respectively, based on commercially available compounds 1 and are much higher than the ones previously reported in the literature.     

A novel calix[4]arene fluorescent receptor for selective recognition of acetate anion

A novel bridged fluorescent calix[4]arene with 1,8-diaminoanthracene and glycine at the upper rim has been prepared, which exhibited selective recognition towards AcO⁻ over other anions such as F⁻, Cl⁻, Br⁻, , , I⁻ and by fluorescence spectroscopy and ¹H NMR method.     

Synthesis and topology of [2+2] calix[4]resorcarene-based chiral cavitand-salen macrocycles

Chiral diastereomeric cavitand-salen macrocycles have been synthesized by the high-dilution condensation of a tris-(quinoxaline-bridged)-diformyl-calix[4]resorcarene with (1R,2R)-diphenylethylenediamine. The reaction produced a couple of diastereoisomers, consisting of two cavitand cavities bis-bridged by two chiral diimino moieties, which differ in a convergent (C-shaped) or divergent (S-shaped) orientation of the two cavities.     

The selective preparation of partial cone O-aryl calix[4]arene ethers from 1,3-dimethoxycalix[4]arene: a new platform for the preparation of non-aggregated dyes

We report a new direct route for the selective preparation of novel partial cone O-aryl ether calix[4]arenes to be used as new platforms for the preparation of non-aggregated dyes. These partial cone conformers have the aromatic substituents lying within the calix[4]arene annulus via the upper rim.