Facile one-pot synthesis of aliphatic bridged diaryloxy compounds,cyclic and crown ethers under mild conditions

We report here the facile, room temperature, catalyst free, one pot synthesis of aliphatic bridged diaryloxy compounds, cyclic and crown ethers. Anhydrous potassium carbonate (K₂CO₃) as a mild base along with dimethyl sulfoxide generates the phenoxide ion which facilitates the nucleophilic substitution of bromoalkanes to yield the corresponding crown ethers.     

Supramolecular control over LCST behavior of hybrid macrocyclic system based on pillar[5]arene and crown ether

A hybrid system containing a pillar[5]arene unit and ten crown ether moieties was developed. The LCST behavior and thermo-responsiveness were successfully introduced into this pillar[5]arene-crown ether system. Both host–guest interactions and salting-out effect displayed great effects in realizing the supramolecular control over LCST properties and thermo-responsiveness. Compared with the individual macrocycles, this hybrid macrocycle system dramatically amplified the supramolecular control effect over LCST behavior.     

One-pot synthesis of well-organized heteropolyrotaxane via self-sorting strategy

Two novel [3]pseudorotaxanes can be selectively synthesized from four components through self-sorting processes, which provides a new strategy for the construction of a well-organized heteropolyrotaxane.     

Supramolecular control over LCST behavior of hybrid macrocyclic system based on pillar[5]arene and crown ether

A hybrid system containing a pillar[5]arene unit and ten crown ether moieties was developed. The LCST behavior and thermo-responsiveness were successfully introduced into this pillar[5]arene-crown ether system. Both host-guest interactions and salting-out effect displayed great effects in realizing the supramolecular control over LCST properties and thermo-responsiveness. Compared with the individual macrocycles, this hybrid macrocycle system dramatically amplified the supramolecular control effect over LCST behavior.     

Tetraphenylporphyrins monosubstituted with a crown ether in one phenyl ring. Synthesis and characterization

Summary The synthesis and spectroscopic characterization of seven new tetraphenyl-porphyrins (1–7) derivatized with 12-crown-4, 14-crown-4, 15-crown-5, or 18-crown-6 ether units inortho orpara position of one of the phenyl rings is described.

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In einem Phenylring mit Kronenethern monosubstituierte Tetraphenylporphyrine. Synthese und Charakterisierung

Zusammenfassung Die Synthese und die spektroskopische Charakterisierung sieben neuer Tetraphenylporphyrine (1–7), die mit 12-Krone-4, 14-Krone-4, 15-Krone-5 oder 18-Krone-6 in derortho-oderpara-Position eines Phenylrings substituiert sind, werden beschrieben.

     

A New Motif for the Self-Assembly of [2]Pseudorotaxanes; 1,2-Bis(pyridinium)ethane Axles and [24]Crown-8 Ether Wheels

Multiple intramolecular interactions help to stabilize the novel [2]pseudorotaxanes formed from 1,2-bis(pyridinium)ethane dications (which act as axles) and 24-membered crown ethers (which act as wheels; see structure). This is the first successful sythesis of [2]pseudorotaxanes with [24]crown-8 as the macrocycle.     

Complexes of benzo-15-crown-5 with protonated primary amines and diamines

Three complexes of benzo-15-crown-5 (B15C5) with protonated primary amines [PhCH₂NH₃(B15C5)](ClO₄), [p-C₆H₄(CH₂NH₃)₂(B15C5)₂](ClO₄)₂, and [(CH₂)₄(NH₃)₂(B15C5)₂](SCN)₂ were isolated and studied in acetonitrile solutions by NMR, and in the solid state by X-ray crystallography. In all complexes, one B15C5 molecule was bound with each R-NH₃⁺ moiety with characteristic small separation of 1.84-1.86 Å between the nitrogen of the R-NH₃⁺ group and the O₅ mean plane of the crown residue. No sandwich-type complexes with a 1:2 R-NH₃⁺/B15C5 stoichiometry were observed. Binding affinities of B15C5 in acetonitrile were similar for all ammonium cations studied: K₁=550±10 M⁻¹ for [PhCH₂NH₃]⁺; K₁=1100±100 and K₂=400±30 M⁻¹ for [p-C₆H₄(CH₂NH₃)₂]²⁺; and K₁=1100±100 and K₂=300±30 M⁻¹ for [H₃N(CH₂)₄NH₃]²⁺. The complexation is primarily enthalpy-driven (ΔH°=−4.9±0.5 kcal/mol, ΔS°=−3.8±1.0 eu for PhCH₂NH₃⁺-B15C5), as determined by variable temperature ¹H NMR titrations.     

Studies on the synthesis and properties of open-chain and macrocyclic crown compounds

Eight new open-chain crown compounds (1–8) and two new macrocyclic crown ethers (9 and10) were synthesized from 1,5-bis(2-aminophenoxy)-3-oxapentane (15) and 1,8-bis(2-aminophenoxy)-3,6-dioxaoctane (16) which were prepared by the catalytic hydrogenation of the corresponding bis(2-nitrophenoxy) derivatives13 and14. The fluorescent property investigation of two open-chain crown ethers (7 and8) indicated that they exhibit complexing effects on Ag⁺ and Mn²⁺ cations and can be used as fluorescent reagents for the microanalysis of the metal cations. The pyrolysis kinetics measurement for compounds5 and6 in nitrogen and air was carried out, and their reaction orders and activation energy were obtained. They are one-step and two-step pyrolysis reactions in nitrogen and air, respectively.     

Deltaarenes; novel macrocyclic molecules that are readily available from 1,4-benzoquinone and benzene dithiols

New types of macrocyclic compounds, deltaarenes, are prepared. The compounds were readily synthesized in three steps from an arenedithiol and benzoquinone, and the yields of the macrocyclization reaction reached up to 40% under high dilution conditions. X-ray crystallographic analysis revealed that the macrocycle has a relatively rigid trimeric structure with a unique triangular hole, the size of which was approximately 11?Å along each side. NMR data suggests that the ring has a C3-symmetric structure. The X-ray analysis showed that the hole is large enough to capture one molecule of chlorobenzene. Use of a variety of dithiols allowed the synthesis of different types of deltaarene derivatives. MO calculations showed that the hole size depends on the dithiol unit. Deprotection of the twelve methoxyl groups was easily achieved by treatment with BBr₃ and yielded the free-OH deltaarene derivative.     

A structural study of calcium,strontium and barium crown ether complexes

Complexes involving the perchlorate, chloride, bromide or iodide salts of the heavy group 2 elements, calcium, strontium or barium, and either 15-crown-5 or 18-crown-6 have been synthesized and their X-ray crystal structures determined. A variety of coordination modes are presented between the crown ether and metal ions.     

Synthesis and characterization of some organo-all-tin dendrimers with different peripheral substituents

The synthesis of the first all-tin-dendrimer Sn[(CH₂)₄SnPh₃]₄ (2) results from complete hydrostannation of tetra(but-3-enyl)stannane (1) with triphenyltin hydride. Selective cleavage of one phenyl group from each dendron of 2 with anhydrous HCl results in Sn[(CH₂)₄Sn(Cl)Ph₂]₄ (3), which on treatment with LiAlH₄ yields the corresponding hydride derivative Sn[(CH₂)₄Sn(H)Ph₂]₄ (4) containing four reactive Sn-H bonds. The cyclopentadienyl derivative Sn[(CH₂)₄Sn(C₅H₅)Ph₂]₄ (5) as well as the transition metal substituted derivatives Sn[(CH₂)₄Sn{Co(CO)₄}Ph₂]₄ (6), Sn[(CH₂)₄Sn{Fe(CO)₂C₅H₅}Ph₂]₄ (7), and Sn[(CH₂)₄Sn{Mn(CO)₅}Ph₂]₄ (8) have been prepared by coupling of 3 with the appropriate Grignard or sodium derivatives of the transition metal moieties. The new compounds were characterized by elemental analyses, IR, ¹H-, ¹³C- and ¹¹⁹Sn NMR spectroscopy and MALDI-TOF mass spectrometry.     

Non-covalent synthesis of ionic and molecular complexes of benzoic acid and substituted 2-aminopyrimidines by varying aryl/alkyl substituents and their supramolecular chemistry

The non-covalent synthesis of ionic and molecular complexes of substituted 2-aminopyrimidines with benzoic acid in crystalline solid phase is reported. The nature of supramolecular architecture varied with the substituents in the 2-aminopyrimidine ring. Two complexes have been synthesised from two differently substituted 2-aminopyrimidines and benzoic acid. In one case, proton transfer takes place and an ionic organic salt is formed, whereas in the other, there is no proton transfer and a hydrogen-bonded molecular complex is formed.     

Self-Assembly of Novel Polyrotaxanes: Main-Chain Pseudopolyrotaxanes with Poly(ester crown ether) Backbones

Not threading rings on chains, but chains through rings results in a new class of main-chain polyrotaxanes. The cations of bipyridinium salts thread through the crown ether units of a poly(ester crown ether) chain (shown below). The threading efficiency m/n of the polyrotaxane is controlled by stoichiometry and temperature.     

Expedient synthesis of benzene tricarboxamide macrocycles derived from p-aminobenzoic acid

The synthesis of macrocycles functionalized at the periphery in a regiospecific fashion is considered challenging. This Letter describes a six-step synthesis of N-alkylated benzene tricarboxamide macrocycles derived from p-aminobenzoic acid via the iterative coupling of Fmoc-protected monomers and cyclization of the resultant linear foldamers.     

The complexation of alkali metal ions by crown ethers,aza crown ethers,and cryptands in propylene carbonate

The reactions between alkali metal ions and crown ethers, aza crown ethers, and cryptands in propylene carbonate were studied by potentiometric and calorimetric titrations. The most stable complexes formed by macrocyclic and macrobicyclic ligands are when the ligand and cation dimensions are comparable. On comparing the complex stabilities of crown ethers and aza crown ethers of the same size, crown ethers were, on the whole, found to form the most stable complexes, with the exception of the lithium cation. Enthalpic factors are responsible. Substitution of the amino group protons of the aza crown ethers by benzyl groups leads to a high increase in values of the reaction enthalpy. This effect is partly compensated by entropic contributions. The bulky benzyl groups reduce the ligand solvent interactions and induce a ligand conformation with the lone pair of electrons from the nitrogen donor atoms which are more or less directed inside the cavity. The thermodynamic data for the transfer from methanol to propylene carbonate indicate that the ligands containing nitrogen show specific interactions with methanol.This paper is dedicated to Professor H. Strehlow on the occasion of his 70th birthday.     

A new crown ether as vesicular carrier for 5-fluoruracil: synthesis, characterization and drug delivery evaluation

Niosomes have shown promise as cheap and chemically stable drug delivery systems. In this paper a novel crown ether amphiphile, 1,16-hexadecanoyl-bis-(2-aminomethyl)-18-crown-6 (Bola A-16), has been synthesized with the aim of developing a long time stable controlled release system. Niosomes have been prepared with different molar ratios of amphiphile and cholesterol and their morphological properties have been determined by quasi-elastic light scattering and transmission electron microscopy. The composition of niosomes affects the entrapment efficiency and the release rate of 5-fluorouracil, a well-known antineoplastic molecule. In addition, other two known azacrown ether amphiphiles (4,7,10,13-pentaoxa-16-aza-cyclooctadecane)-hexadecanedioc acid diamide (Bola D-16) and ,ω-(4,7,10,13-pentaoxa-16-aza-cyclooctadecane)-hexadecane (Bola C-16), have been synthesized and the obtained vesicles have been characterized for comparison. Furthermore, the release profile of 5-fluorouracil in vitro, from these niosomes, has been studied over a period of 6 h in order to simulate a hematic adsorption.     

Self-Assembly of Quinodimethanes through Covalent Bonds: A Novel Principle for the Synthesis of Functional Macrocycles

A multiplication of functional units was accomplished in a simple fashion by the tetramerization of a quinodimethane. This principle is demonstrated by the convergent construction of a macrocyclic molecule with 16 ferrocenes and a macrocyclic molecule with 16 dendritic units at the periphery of the molecule (see scheme). FG=functional group     

Globular carbosilane dendrimers with mannose groups at the periphery: synthesis, characterization and toxicity in dendritic cells

A synthetic strategy has been developed for the preparation of new globular carbosilane dendrimers with mannose groups at the periphery. It consists of hydrosilylation reaction of allyl tetraacetylmannose with carbosilane dendrimers containing monohydrosilane end groups and the subsequent deacetylation reaction. Evaluation of dendrimer toxicities in dendritic cells by MTT assay were carried out, and evidence a good biocompatibility.