Oxygen- and Nitrogen-Embedded Zigzag Hydrocarbon Belts

Despite the aesthetically appealing structures and tantalizing physical and chemical properties, zigzag hydrocarbon belts and their heteroatom-embedded analogues remain challenging synthetic targets. We report herein the synthesis of diverse O/N-doped zigzag hydrocarbon belts based on selective bridging of the fjords of resorcin[4]arene derivatives through intramolecular S_NAr and palladium-catalyzed intermolecular C−N bond formation reactions. Preorganized conformations of mono-macrocyclic, half-belt and quasi-belt compounds were revealed to facilitate cyclization reactions to construct heteroatom-linked octahydrobelt[8]arenes. The acquired products had strained square-prism-shaped belt structures in which all six-membered heterocyclic rings adopted an unusual boat conformation with equatorially configured alkyl groups. The unprecedented heteroatom-bearing belts also exhibited different photophysical and redox properties to those of octahydrobelt[8]arene analogues.     

Functionalized Hydrocarbon Belts: Synthesis,Structure and Properties

Hydrocarbon belts have drawn great attention because of their unique structures and tantalizing properties. Although a few belts and heteroatom-doped analogs have been synthesized, belt molecules containing non-hexagonal rings remain rare. Herein we report the construction and application of unprecedented zigzag-type hydrocarbon belts which contain functionalized eight-membered rings. The synthesis features fourfold intramolecular acylation reactions of resorcin[4]arene-derived intermediates, which affords C₄-symmetric tetrabenzobelt[4]arene[4]cyclooctatrienones. Stereoselective ketone reduction with LiAlH₄ and nucleophilic addition with alkynyllithiums provide the corresponding tetrahydroxylated belts. The tetraol and its methyl ether are powerful and selective hosts to form 2 : 1 and 1 : 1 complexes with cesium ion, respectively, with binding constants up to (1.71±0.33)×10¹¹ M⁻² and (1.50±0.16)×10⁶ M⁻¹. In addition, enantiopure C₄-symmetric belts can emit CPL with |g_lum| being around 0.01.     

A Fullerene‐Substituted Pillar[5]arene for the Construction of a Photoactive Rotaxane

Transformation of a methylene group of the pillar[5]arene scaffold into a ketone has been achieved by treatment with N‐bromosuccinimide followed by hydrolysis of the bromide intermediate and oxidation of the resulting secondary benzylic alcohol with BaMnO₄. Condensation of the resulting macrocycle including a ketone function with p‐toluenesulfonyl hydrazide followed by reaction of the corresponding tosylhydrazone with C₆₀ under modified Bamford–Stevens conditions gave a fulleropillar[5]arene derivative. This building block has been used to prepare a rotaxane. The resulting molecule combining the fullerene‐functionalized macrocycle with an axle bearing a porphyrin stopper is a photoactive molecular device in which the porphyrin emission is efficiently quenched by the fullerene moiety.     

Design of Organoiron Macromolecules Based on Upper Rim Functionalized Calix[4]arenes

The versatility of cationic cyclopentadienyliron complexes is demonstrated for the generation of calix[4]arene‐based dendrimers and polymers. Dendrimers were prepared from a branched organoiron calix[4]arene through subsequent reactions of azo dyes and organoiron complexes. The resulting azo dye‐containing metallocalix[4]arenes were soluble in polar organic solvents and displayed λ_max ranging between 430 and 456 nm. Upon addition of various acids, the λ_max shifted to higher wavelengths (513–535 nm). In the solid state and in solution, the azo dye‐containing metallocalix[4]arenes reversibly changed colour in the presence of acid and base, indicating their potential use as acid sensors. Cyclic voltammetric studies showed that the iron centres of the metallocalix[4]arenes were reversibly reduced at E_1/2 = −1.49 V. When non‐branching organoiron‐based calix[4]arene were reacted with dithiols, polymers containing calix[4]arenes either in their side chains or main chains were obtained. The polymers possessed weight average molecular weights between 35 000 and 53 000. The polymers were determined to be thermally stable with backbone decomposition occurring above 500 °C.

     

New Efficient Synthetic Pathways to Tetrakis{p‐[(diethylphosphono)methyl]}calix[4]arene

Various operating conditions have been applied on tetrakis[p‐(halogenomethyl)]‐ and tetrakis[p‐(aminomethyl)]calix[4]arene derivatives to improve the synthesis of the 5,11,17,23‐tetrakis[(diethylphosphono)methyl]‐25,26,27,28‐tetrahydroxycalix[4]arene. Two new, high yield, synthetic pathways have been selected, involving, for the first one, the 25,26,27,28‐tetrahydroxy‐5,11,17,23‐tetrakis[(trimethylamino)methyl]calix[4]arene, tetraiodide, DMF, and 10 equiv. of triethyl phosphite ((EtO)₃P), and, for the other one, the 5,11,17,23‐tetra(bromomethyl)‐25,26,27,28‐tetrahydroxycalix[4]arene, CH₂Cl₂, and only 4 equiv. of (EtO)₂P.     

Polymorphic crystals of oxacalix[4]arene with 1,3‐alternate conformations of S4 and C2 symmetry

Calix[4]arene and oxacalix[4]arene derivatives have eight possible conformations in the up and down directions of their four aromatic rings from the mean plane of a bridged central ring, the conformations of which determine the functionality of the host frameworks. Despite being a known compound for five decades, oxacalix[4]arene, C₂₄H₁₆O₄, has not been characterized previously by crystallographic methods. It crystallizes from hexane/CH₂Cl₂ solution to give two polymorphs, i.e. prismatic and block‐shaped crystals as twisted 1,3‐alternate structures with S₄ and C₂ symmetry, respectively. These were previously suggested as the prefered stable conformations by density functional theory (DFT) calculations.     

Construction of Hydrocarbon Nanobelts

Linearly fused hydrocarbon nanobelts are a unique type of double‐stranded macrocycles that would serve as not only the powerful hosts in supramolecular science but also the templates to grow zig‐zag carbon nanotubes with defined diameters. Fully conjugated hydrocarbon nanobelts such as belt[n]arenes would also possess unique physical and chemical properties. Despite the importance, both fully conjugated and (partially) saturated hydrocarbon nanobelts remain largely unexplored because of the lack of cyclization methods. Reported here is the construction of nanometer sized H₁₂‐belt[12]arenes based on the strategy to close up all fjords of resorcin[6]arene by means of six‐fold intramolecular alkylation reactions of resorcin[6]arene derivatives. All resulting H₁₂‐belt[12]arenes produce a very similar nanobelt core structure with six benzene rings and six boat 1,4‐cyclohexadiene rings being alternately linear‐fused to give a nearly equilateral hexagonal cylinder. The average long diagonal is around 1 nm and the height of the cylinder is about 0.3 nm. The acquired H₁₂‐belt[12]arenes would be the potential precursors to various hydrocarbon nanobelts including fully conjugated belt[12]arenes.     

Liquid chromatographic behavior of two alanine‐substituted calix[4]arene‐bonded silica gel stationary phases

Two new kinds of alanine‐substituted calix[4]arene stationary phases of 5,11,17,23‐p‐tert‐butyl‐25,27‐bis(l ‐alanine‐methylester‐N‐carbonyl‐methoxy)‐26,28‐dihyroxycalix[4]arene‐bonded silica gel stationary phase (BABS4) and 5, 11, 17, 23‐p‐tert‐butyl‐25,26,27,28‐tetra(l ‐alanine‐methylester‐N‐carbonyl‐methoxy)‐calix[4]arene‐bonded silica gel stationary phase (TABS4) were prepared and characterized in the present study. They were compared with each other and investigated in terms of their chromatographic performance by using polycyclic aromatic hydrocarbons, disubstituted benzene isomers, and mono‐substituted benzenes as solute probes. The results indicated that both BABS4 and TABS4 exhibited multiple interactions with analytes. In addition, the commonly used Tanaka characterization protocol for the evaluation of commercially available stationary phases was applied to evaluate the properties of these two new functionalized calixarene stationary phases. The Tanaka test results were compared with Zorbax Eclipse XDB C₁₈ and Kromasil phenyl columns, respectively. BABS4 has stronger hydrogen‐bonding capacity and ion‐exchange capacity than TABS4, and features weaker hydrophobicity and hydrophobic selectivity. Both of them behave similarly in stereoselectivity. Both BABS4 and TABS4 are weaker than C₁₈ and phenyl stationary phases in hydrophobicity and hydrophobic selectivity.     

Corona[5]arenes Accessed by a Macrocycle‐to‐Macrocycle Transformation Route and a One‐Pot Three‐Component Reaction

Corona[5]arenes, a novel type of macrocyclic compound that is composed of alternating heteroatoms and para ‐arylenes, were synthesized efficiently by two distinct methods. In a macrocycle‐to‐macrocycle transformation approach, S₆‐corona[3]arene[3]tetrazine underwent sequential S_NAr reactions with HS‐C₆H₄‐X‐C₆H₄‐SH (X=S, CH₂, CMe₂, SO₂, and O) to produce the corresponding corona[3]arene[2]tetrazines. Different corona[3]arene[2]tetrazine compounds were also constructed in a straightforward manner by a one‐pot three‐component reaction of HS‐C₆H₄‐X‐C₆H₄‐SH (X=S, CH₂, CMe₂, SO₂, and O) with diethyl 2,5‐dimercaptoterephthalate and 2 equiv of 3,6‐dichlorotetrazine under very mild conditions. All corona[5]arenes adopted 1,2,4‐alternate conformational structures in the crystalline state yielding similar nearly regular pentagonal cavities. Both the cavity size and the electronic property of the acquired macrocycles were fine‐tuned by the nature of the bridging element X.     

Synthesis and Structure of Novel Double Flexible Spacer Bridged Biscalix[4]arenes

25, 25′, 27, 27′‐Bis(1,3‐dioxypropane)‐bis(5, 11, 17, 23‐tetra‐tert‐butylcalix[4]arene‐26,28‐diol) (4) and 25, 25′, 27, 27′‐bis(1, 4‐dioxybutane)‐bis (5, 11, 17, 23‐tetra‐tert‐butylcalix‐[4]arene‐26, 28‐diol) (5) were synthesized by the reaction of p‐tert‐butylcalix[4]arene (1) with preorganized 25, 27‐bis(3‐bromoproxyl)calix[4]arene‐26, 27‐diol (2) and 25, 27‐bis(3‐bromobutoxyl)calix[4]arene‐26, 27‐diol (3) in the presence of K₂CO₃ and KI. Compounds 4 and 5 were characterized with X‐ray analysis and the selectivity of 4 and 5 toward K⁺ over other alkali metal ions, alkaline metal ions as well as NH₄⁺ were investigated with an ion‐selective electrode.     

Aminolysis of p-tert-butyltetrathiacalix[4]arene tetraethylacetates in cone, partial cone and 1,3-alternate conformation: synthesis of amide based receptors for oxyanions

Cone, partial cone and 1,3-alternate conformers of tetrathiacalix[4]arene tetraethylacetate were synthesized and subjected to aminolysis with alkyl amines [CH₃(CH₂)_nNH₂; n=2, 3, 5] to yield mono-, di-, tri- or tetrasubstituted p-tert-butyltetrathiacalix[4]arene amides which were characterized by detailed analysis of their NMR spectral and single crystal X-ray crystallography. It has been observed that while the 1,3-alternate and cone conformers of the tetrathiacalix[4]arene tetraethylacetate gave corresponding tetrathiacalix[4]arene tetraamides under different experimental conditions, the corresponding partial cone conformer undergoes a cascade of regioselective reactions with the same amines. Variable temperature ¹H NMR experiments allowed the determination of relative stability of different conformers within the temperature range of 298-333 K. The synthesized derivatives were evaluated as molecular extractants for cations and anions and were determined to facilitate extraction of oxyanions (CrO₄²⁻ and Cr₂O₇²⁻) from aqueous to the organic phase. The studies have a significance in the design of tetrathiacalix[n]arene based molecular receptors for innovative applications.     

对叔丁基杯[10]冠醚的合成

首次合成一系列杯[10]冠醚。通过将对叔丁基杯[10]芳烃和乙二醇双对甲苯磺酸酯或多甘醇双对甲苯磺酸酯在K2CO3/甲苯或Cs2CO3/丙酮体系中反应,得到一系列杯[10]冠醚:1,2-杯[10]冠-4、1,3-杯[10]冠-2、1,2-,1,3-杯[10]冠-3、1,4-杯[10]冠-4、和1,6-杯[10]冠-4。     

Influences of Hard Donor on Cation Selectivities Closing to Soft Selenium Donor in Tweezer-like Calix[4]arene Receptors

Three novel 25,27-dihydroxy-26,28-bis(3-benzylselenopropoxy)-5,11,17,23-tetra-tert-butylcalix[4]-arene (2),25,27-dihydroxy-26,28-bis[3-(2-hydroxyethylseleno)propoxy]-5,11,17,23-tetra-tert-butyl-calix[4]arene (3) and 25,27-dihydroxy-26,28-bis(3-propylselenoproppxy)-5,11,17,23-tetra-tert-butyl-calix[4]arene (4) were synthesized for the comparison of their ion-selectivity in ion-selective electrodes (ISE). X-ray structure of the CH/π complex of 4.CH2Cl2 was elucidated. ISEs based on 2-4 as neutral ionophores were prepared, and their selectivity coefficients for Ag (logKAg,M^pot) were investigated against some main group metal ions and transition metal ones using the fixed interference method (FIM). These ISEs showed excellent Ag^ selectivity over most of the interfering cations examined. It is evident that the stronger Hg^2 interference may not be produced while hard donors (hydroxy) are close to the soft selenium donors.     

Zweifach und dreifach intramolekular verbrückte p‐tert‐Butylcalix[8]aren‐triphosphate – Synthese,Struktur und Stereochemie

Two‐ and Threefold Intramolecular Brigdging p‐tert‐Butylcalix[8]arene Triphosphates – Synthesis, Structure and Stereochemistry [1] The phosphorylation of p‐tert‐butylcalix[8]arene ( 1 ) with phosphorus pentachloride and hydrolysis gives intramolecular bridging tert‐butylcalix[8]arene triphosphates. The reactivity (esterification, dehydratisation, complexation), the structure (nmr and x‐ray), and the stereochemical behaviour of the phosphates will be discussed.     

Inclusion of p‐sulfonatothiacalix[4]arene and its metal complexes

As a new member of the water‐soluble calixarene family, p‐sulfonatothiacalix[4]arene possesses unique properties resulting from its inherent structural characteristics. In our recent research, we have investigated the self‐assembly of bowl‐like p‐sulfonatothiacalix[4]arenes with or without transition‐metal ions in the presence of suitable guests. We have obtained a series of compounds with different structural motifs, such as capsules, tetranuclear clusters, and molecular clefts. In addition, p‐sulfonatothiacalix[4]arenes show good inclusion abilities and can capture different guests by utilizing their hydrophobic cavities through supramolecular interactions. Even when a cone‐like conformation is fixed, the p‐sulfonatothiacalix[4]arene can also splay its opposite aromatic rings apart to adjust its cone‐like conformations from C_4v to C_2v and even lower symmetries. All of these show that it is a good candidate for the research of inclusion phenomena. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 155–168; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.200800033     

Studies on Properties of p—Nitrophenylazo Calix[4]arene Derivatives

The p-nitrophenylazo calix[4] arene derivatives la-ld with nonlinear optical(NLO)properties were prepared by the diazo-coupling reaction of calix[4]arene with p-nitrophenyl diazonium.The diazotization reaction of p-nltroaniline was caried out with isoamyl nitrite as a source of nitrous acid in EtONa/EtOH under refluxing conditon.X-Ray crystallographic analysis and ^1H NMR sptectra reveal that they exist as cone conformation in crystal state or in soution.HRS measurements at 1064 nm in THF indicate that p-nitrophenylazo calix[4]arenes have higher hyperpolarizability βz values than the corresponding reference compound 4-(4-nitrophenylazo)-2,6-dimethyl-phenol,without red shift of the charge transfer band.The tetrakis p-nitropheylazo calix[4]arene(2)with longer alkyl chains can form monolayer aht the air/water interface.     

Synthesis and Molecular Structures of Tetrasilyl Ethers of Calix[4]arenes

The tetrasilyl ethers calix[4]areneOSiMe₂R (R = Me, H, vinyl, allyl) were prepared by salt elimination; the calix[4]arene was deprotonated with sodium hydride and subsequently reacted with chlorosilanes ClSiMe₂R. In general, DMF was chosen as solvent in order to steer the reactions in terms of a preference for the cone‐conformation of the products. In the case of calix[4]areneOSiMe₃ both, partial‐cone‐ and cone‐conformers, were synthesised. All products were characterised by NMR (¹H, ¹³C, ²⁹Si) spectroscopy, mass spectrometry and single‐crystal X‐ray diffraction.     

Fluorescence Spectral Studies on the Coordination of Calix[4]‐arenes Bearing Boronic Acid Moieties with Monosaccharides

Coordination of ten calix[4]arenes bearing boronic acid moieties with five monosaccharides was studied by fluorescence spectrometry. The stability constants (K₂) of the complexes and Gibbs free energy change ( ‐ ΔG⁰) of the coordination reactions were calculated according to the modified Hilderbrand‐Benesi equation. The results obtained indicated that the coordination ability of D‐( ‐ )‐fructose with calix[4] arenes bearing boronic acid moieties was stronger than that of the other monosaccharides. And these calix[4]arene derivatives might be used for identification of L‐( ‐ )‐sorbose.     

Enantioselective Recognition of Calix[4]arene Derivative Bearing Bicyclic Guanidinium for D/L Amino Acid Zwitterions

The p‐tetra‐tert‐butyl calix[4] arene derivatives (3 and 4) with (5,5) chiral bicyclic guanidinium, as the receptors of amino acid zwitterions, have been synthesized via a O‐alkylation reaction of p‐tetra‐tert‐butyl calix [4] arene with cbJoromethyl chiral bicyclic guanidinium 2 in the presence of anhydrous K₂CO₃ in acetonitrile. The results obtained from liquid‐liquid competitive extraction experiments indicate that the two receptors may selectively recognize L‐aromatic amino acids, and that the enantioselective recognizability of the receptor 4 with two chiral bicyclic guanidinium units reachs up to about 90% for L‐Phe.     

A Convenient Synthesis and Pharmacological Activity of Novel Annelated Pyrimidine Derivatives

Simple and convenient synthesis for a series of 2,3‐diglycosylpyrimidine 4 , pyrazolo[3,4‐d]pyrimidine 8 , ditetrazolo[1,5‐a;1′,5′‐c]pyrimidine 9 , 2,9a,10‐triazaanthracene 12 , thieno[2,3‐d]pyrimidine 14 , 1,3,5,7‐tetraazafluorene‐8‐one 15 , 1,3,5‐triazafluorene‐8‐one 16 , 1,3‐diazafluorene 21a,b derivatives have been synthesized via a sequence of heterocyclization reactions of suitably functionalized 6‐[5‐(4‐bromophenyl)ox‐azol‐4‐yl]‐4‐oxo‐2‐thioxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carbonitrile ( 2 ) with different electrophiles and nucleophiles. The new compounds were prepared with the objective to study their pharmacological properties.