Selective functionalization of a resorcin[6]arene

The Mannich-type condensation of hexaethylresorcin[6]arene with achiral primary amines results in S₆-symmetrical hexadihydro-1,3-oxazine derivatives, which are mesoforms. The reaction with individual enantiomers of α-phenylethylamine leads to C₃-symmetrical enantiomeric hexaoxazines, which crystallize from reaction mixtures in an analytically pure form.     

Rhodium(II) catalyzed highly diastereoselective synthesis of conformationally restricted dispiro[1,3-dioxolane]bisoxindoles

Synthesis of conformationally restricted dispiro- and bis-dispiro-1,3-dioxolanes via three-component reaction of diazoamides, ketoamides/diketones, and aromatic/heteroaromatic aldehydes in the presence of rhodium(II) acetate dimer catalyst at room temperature involving carbonyl ylides is demonstrated with diastereoselectivity. Synthesis of macrocyclic dispiro-1,3-dioxolanes via intramolecular carbonyl ylide is also delineated in high yield. The conformationally restricted symmetrical as well as unsymmetrical dispiro-1,3-dioxolanes were obtained under mild conditions in a highly diastereo- and regioselective manner.     

A new synthesis of p-nitrocalix[6]arene

p-Nitrocalix[6]arene which possibly serves as a potential intermediate to derive functionalized calixarenes was synthesized for the first time.     

Synthesis of molybdenocene(IV) and tungstenocene(IV) tropolonato complexes: Its derivative containing calix[4]arene moiety

The cationic di-μ-hydroxo dinuclear complexes of molybdenocene and tungstenocene [Cp₂M(μ-OH)₂MCp₂]⁺ (Cp = η-C₅H₅; M = Mo or W) react with tropolone to afford corresponding tropolonato complexes [Cp₂M(trop)]⁺ (trop = C₇H₅O₂). The products were investigated by IR, ¹H NMR, and ¹³C NMR spectroscopy as well as by X-ray crystallography (M = W). The structure shows that the central metal is surrounded by a distorted tetrahedral array of the two centers of cyclopentadienyl ligands and the two oxygen atoms of tropolonato ligand. The reaction has been extended to the synthesis of calix[4]arene receptor functionalized at the 1,3-positions of the upper rim with two tropolonato-molybdenocene centers.     

Characterization of precursors of p-tert-butylcalix[6]arene synthesis. Mechanism of formation of p-tert-butylcalix[6]arene

Abstract

Gutsche has proposed the existence of “hemicalixarenes” and “pseudocalixarenes” to explain the formation of calixarenes. The characterization and the quantitative determination of molecules present during the reaction, described in “Organic Synthesis”, have permitted us to determine the immediate precursors of p-tert-butylcalix[6]arene. The calix[6]arene could be due to cyclization of linear species named “pseudocalixarenes” and not due to duplication of molecules named “hemicalixarenes”.     

Titanocene dichloride route to a tetranuclear oxo-bridged monocyclopentadienyl titanium(IV) calix[4]arene complex

Lithiation of p-tBu-calix[4]arene followed by reaction with titanocene dichloride affords a novel tetranuclear titanium(IV) monocyclopentadienyl complex, wherein a single calix[4]arene in a cone conformation provides O-phenoxy coordination to four titanium atoms, with additional mu-oxo bridging between titanium centres in an eight membered ring.     

Synthesis of conformationally diverse tetrathiacalix[4]arene(amido)crowns and tetrathiacalix[4]arene amides with pendant amine functions

A series of conformationally diverse novel tetrathiacalix[4]arene(amido)crowns and amides from tetrakis((ethoxycarbonyl)methoxy)p-tert-butyl tetrathiacalix[4]arene and its debutylated analog have been prepared by their reaction with diamines [H₂N(CH₂)_nNH₂; n=2,3,4, and 6] and polyamines. It has been determined that the length of the alkyl spacer in diamines is pivotal for the formation of either the tetrathiacalix[4]arene bis(amido)crowns or tetrathiacalix[4]arene amides with pendant amine functions. The synthesized compounds represent potential building blocks for achieving sophisticated molecular assemblies for molecular organization and recognition. Single crystal X-ray analysis of tetrathiacalix[4]arene bis(amido)crown 6a revealed that it has a 1,3-alternate conformation, which forms supramolecular complexes with chloroform.     

Selective synthesis of functionalized thia- and oxacalix[2]arene[2]pyrimidines

Functionalized oxacalix[m]arene[n]pyrimidines have been synthesized by S(N)Ar on 4,6-dihalopyrimidine building blocks. Depending on the S(N)Ar conditions, either a mixture of oxacalix[n]arenes, ranging from oxacalix[4]- up to oxacalix[12]arene, could be prepared or the oxacalix[4]arene could be synthesized selectively in a high yield. The electrophilic (pyrimidine) and the nucleophilic components could both be varied, allowing the preparation of functionalized oxacalix[4]arenes. Moreover, the procedure also gives access to the analogous thiacalix[4]arenes.     

Spectrophotometric study of the supramolecular complexes of [60]- and [70]Fullerenes with biscalix[6]arene and crown[4]calix[6]arene

[60]- and [70]Fullerenes have been shown to form 1:1 supramolecular complexes with bis[2-(5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41-pentahydroxycalix[6]arenyl-oxy ethyl ether) (1) and 5,11,17,23,29,35-hexa-tert-butyl-37,38,40,41-tetra hydroxyl-39,42-(crown-4)calix[6]arene (2) in CHCl3 medium by electronic absorption spectroscopy. Formation constants (K) of the complexes of [60]- and [70]fullerenes with 1 and 2 have been determined at room temperature from which free energy of formation values of the complexes have been estimated. The very high formation constant value of [60]fullerene/1 complex (5900 dm3 mol-1) in indicative of formation of inclusion complex. Moreover, PM3 calculations reveal that intermolecular interaction between [60]fullerene and 1 proceeds through quite deep energy molecular orbital.     

Phosphoester hydrolysis by cerium(IV)-thiacalix[4]arene complexes and its application to immunoassay

Thiacalix[4]arenetetrasulfonate was treated with Ce(IV) in water at pH 9.5 to give novel phosphoester-hydrolyzing complexes. The dinuclear Ce(IV) complex promoted the hydrolysis of p-nitrophenyl phosphate with a turnover frequency of 6.8 h⁻¹ at 50 °C, showing fourfold higher activity than the mononuclear complex. The dinuclear complex was readily immobilized onto an antibody by simply mixing them in water, hence its phosphatase-like activity was applied to the color-developing reaction in immunoassay. The model assay using an antibody labeled with the dinuclear complex allowed the detection of as little as 10 ng mL⁻¹ of a tumor marker, Bence–Jones protein, in a 96-well microtiter plate format. Analysis of urine for Bence–Jones protein was performed by the proposed method.     

基于C3v对称性的杯[6]芳烃对Hg2+的荧光选择性识别

合成了一系列具有C3v对称性、下缘分别利用Se、Te和S杂原子连接蒽环发光基团的杯[6]芳烃衍生物1-3.通过紫外-可见光谱和荧光光谱研究了它们对各种碱金属离子和过渡态金属离子的化学传感识别行为. 结果表明,含有Se杂原子的主体1在CH2Cl2溶液中对Hg2+表现出良好的选择性. 并且,通过肉眼可以直接观察到溶液颜色由无色变为黄色.通过荧光光谱的连续滴定实验,主体1-Hg2+体系的稳定常数可达（1.12 ? 0.08) ? 105 M-1. 因此,化合物1有望成为一种用于检测Hg2+的新型化学传感器.     

Synthesis, crystal structure and reactivity of uranium(IV) complexes with p-tert-butylcalix[4]arene ligands

Reactions of UCl4 with 25,27-dimethoxy-5,11,17,23-tetra-tert-butylcalix[4]arene (H2Me2calix) in THF or pyridine at 80 degrees C gave [UCl2(Me2calix)L2] [L = THF (1) or pyridine (2)]. Similar treatment of U(acac)(4) (acac = MeCOCHCOMe) with H2Me2calix in THF or pyridine afforded [U(acac)2(Me2calix)] (3). The bis-calixarene compound [U(Me2calix)(H2calix)] (4) was obtained by reaction of U(OTf)4 or U(OTf)3 with H2Me2calix in pyridine at 110 degrees C. Treatment of UCl4 with H2Me2calix in pyridine at 110 degrees C gave [Mepy][UCl2(Hcalix)(py)2] (5) resulting from demethylation and acid cleavage of the methoxy groups of the calixarene ligand of 2. Adventitious traces of air were responsible for the formation of [Hpy][Mepy]4[{UCl(calix)}3(mu3-O)][UCl6] (6) during the reaction of UCl4 and H2Me2calix, and of [{U(Me2calix)(mu3-O)LiCl(THF)}2] (7) during the reaction of 2 with tBuLi. The X-ray crystal structures of 1.2THF, 2.2py, 3.0.25L (L = THF and py), 4.2py, 5, 6.3py and 7.THF have been determined.     

Monocyclopentadienyl titanium(IV) dithiocarbamate complexes

Preparation of titanium(IV) complexes of the type CpTi(dtc)Cl₂, CpTi(dtc)₂Cl and CpTi(dtc)₃ has been carried out by reacting CpTiCl₃ and respective sodium dithiocarbamate viz. N-(ethyl, m-tolyl), N-cyclopentyl and N-cycloheptyl dithiocarbamates in the desired metal to ligand ratio in refluxing dichlomethane. Studies of the physical properties reveal monomeric and nonelectrolytic nature of these complexes, where dithiocarbamate behaves as bidentate ligand. Therefore, 5, 6 and 7 coordinate structure can be assigned to CpTi(dtc)Cl₂, CpTi(dtc)₂Cl and CpTi(dtc)₃, respectively.     

Crystal and molecular structure of two calix[6]arenes:p-Isopropylcalix[6]arene andp-tert-butylcalix[6]arene—benzene(1∶3) complex

The isopropyl derivative crystallizes from a mixture of carbon disulfide and benzene in the orthorhombic system: Space groupP2₁ nb, a=17.420(3),b=17.708(3),c=18.972(3) Å,V=5852(3) Å,Z=4. Thet-butyl derivative crystallizes from benzene, but the crystal is a complex (13), space groupP,a=15,065(5),b=19.103(3),c=13.878(3) Å, =106.95(2), =102.72(2), =80.61(2),V=3703(2) ų,Z=2. Refinement led toR=0.185 for 1512 reflections for the isopropyl derivative, a sufficiently high number to establish the conformation of the molecule; for thet-butyl complexR=0.12 for 7340 reflections. Intramolecular hydrogen bonds are given as well as comparison of the conformation of both compounds. Thet-butyl groups and the benzene molecules are disordered but the isopropyl groups are not. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82071 (57 pages).     

Ethylene polymerization promoted by dinuclear titanium p-tert-butylthiacalix[4]arene complexes

The dinuclear titanium p-tert-butylthiacalix[4]arene complexes 1 and 2 after activation with methylaluminoxane have been tested as homogeneous catalysts for the polymerization of ethylene. The results show that the catalytic activity of 1, although still poor, is higher than those of the related mononuclear titanium complexes bearing calix[4]arene as ligand. The molecular weight of the polyethylene produced are high (M_W up to 1.4 × 10⁶ Dalton) with broad molecular weight distribution. The polyethylenes have high melting point (133-142 °C) indicating a linear polymer microstructure which was confirmed by ¹³C NMR analysis.     

One-pot synthesis of conformationally restricted spirooxindoles

Diastereomeric three-, five- and six-membered spirocycloalkyloxindoles were successfully synthesized in a rapid and convenient manner from readily accessible starting materials in moderate to high yields using 1-methyl-3-acetonitriloxindole after a one-pot base-mediated double-alkylation strategy. It was found that the diastereoselection is dependent on the reaction conditions and the spirocycloalkyl ring size, with the 3R^∗,8R^∗ diastereomers being thermodynamically favored under the basic reaction conditions for three- and five-membered rings, and the 3R^∗,8S^∗ diastereomer in the case of six-membered rings, as predicted by DFT calculations. The relative stereochemistry was supported by 2D NMR spectra and X-ray crystal structural analysis. The conformational rigidity of the spirocycloalkyloxindoles in solution was established based on NMR experimental and theoretical DFT approaches.     

[6+2]Cycloadditions catalyzed by titanium complexes

The Ziegler catalyst TiCl₄-Et₂AlCl and the arenetitanium(II) complex (η6-C₆H₆)Ti(II)(AlCl₄)₂ induce [6 + 2]cycloaddition reactions of cycloheptatriene with dienes and acetylenes. Addition to 1,3-butadiene affords 7 - endo - vinyl - bicyclo[4.2.1]nona - 2,4 - diene (main product) and bicyclo[4.4.1]- undeca - 2,4,8 - triene, a product of [6+4]cycloaddition. Isoprene reacts similarly, yielding mainly 7- endo - isopropenyl - bicyclo[4.2.1]nona - 2,4 - diene. 2,3 - Dimethyl - 1,3 - butadiene gives 8,9dimethylbicyclo [4.4.1]undeca - 2,4,8 - triene, a product of [6 + 4]cycloaddition, while [6 + 2]cross-adducts are minor products. The reaction of cycloheptatriene with norbornadiene gives mainly hexacyclo[6.5.1.0^2,7.0^3,12.^6,10.0^9,13]tetradec - 4 - ene via [6+2]cycloaddition followed by intramolecular Diels-Alder reaction. As a by-product, pentacyclo[7.5.0.0^2,7.0^3,5.0⁴⁸]tetradeca - 10,12 - diene is formed by a [2+2+2]mechanism. Addition of cycloheptatriene to diphenylacetylene and bis - (tri- methylsilyl)acetylene furnishes sustituted bicyclo[4.2.1]nona - 2,4,7 - trienes. Alkenes, E,E-2,4 - hexadiene and 1,3 - cyclooctadiene are unreactive. The [6+2]cycloaddition is made possible by coordination of cycloheptatriene to titanium, which changes the symmetry of the frontier orbitals in the triene. The reactivity of the trienophile is also enhanced by coordination to the catalyst.     

Calix[4]arene rhenium(V) complexes as potential radiopharmaceuticals

The calix[4]arene platform was used for the syntheses of novel rhenium(V) complexes, that may have potential applications as radiopharmaceuticals. The reaction of ReO(PPh3)2Cl3 with tetradentate N2O2-calix[4]arene ligand 8 in ethanol gave the novel mixed-ligand rhenium complex 9 with the structure ReO(N2O2-calix)OEt. The configuration was elucidated by using a number of 1H NMR techniques. In 9, the ethoxy ligand could be easily and quantitatively exchanged for another monodentate ligand to give complex 12. Tetradentate N2S2-calix[4]arene ligand 15 formed the rhenium complex 16 either via reaction with ReO(PPh3)2Cl3 in an organic solvent or by reaction with rhenium gluconate in an aqueous solution. Complex 16 showed good stability in phosphate-buffered saline solution (37 degrees C, 5 d). The crystal structures of a mono- and a bimetallic complex were determined. The bimetallic N2O2-calixarene complex dimer 11 crystallized in the monoclinic space group C2/c, with a = 38.963(5) A, b = 23.140(6) A, c = 27.382(6) A, beta = 128.456(10) degrees, V = 19,333(7) A3, Z = 8, and final R = 0.0519. The monometallic N2S2 model complex 17 crystallized in the monoclinic space group Cc, with a = 15.715(2) A, b = 12.045(2) A, c = 20.022(3) A, beta = 94.863(12) degrees, V = 3776.3(10) A3, Z = 4, and final R = 0.0342.