Macrocyclic Ethers Research Articles

Synthesis and Ring-Opening Polymerization of Single-Sized Aromatic Macrocycles for Poly(arylene ether)s

Single-sized, pure arylene ether macrocycles (11-21) ranging from 30 to 60 atom ring sizes were synthesized in good yields (up to 83%) by the two-component method under high dilution conditions. These macrocycles have unsymmetric structures containing sulfone/ketone or sulfone/phosphine oxide functional groups and have relatively low melting points. The melt ROP of the single-sized macrocycles to form poly(arylene ether)s exhibits two-stage characteristics: the first stage is very fast, presumably driven by the large entropy difference between cyclics and linears; the second stage is very slow and is believed to be diffusion controlled due to the high viscosity created in the first stage reaction. The latter stage leads to incomplete polymerization at the low initiator concentrations (1-3 mol%). At high initiator concentrations (5-7 mol %), 100% conversion is reached due to improved initiator distribution in the macrocycles; however, this reduces the molecular weights of the polymers. The molecular weight is found to build up very rapidly, independent of conversion, reaction time, and type of initiator. The ROP is initiated by CsF and alkali phenoxides. The efficiency of the alkali metal counterion is generally in the order Cs + > K + > Na + , while a phenoxide initiator is more efficient than a fluoride initiator. It is also found that the Cs counterion leads to the highest degree of crosslinking. The ROP of cyclic oligomeric mixtures (22) is also reported for comparison; the study shows that the molecular weight depends on time and conversion and that the conversion is sensitive to the content of linear impurities and the average ring size of the cyclic mixtures.

ChemInform Abstract: Formation of Substituted Macrocyclic Ethers by Radical Cyclization.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Macrocyclic Ethers and Their Inclusion Complexes

AbstractThe synthesis and characterisation of eleven new macrocyclic ethers (up to 96‐membered [6+6] gigantocycle) with well‐defined cavities are described. Syntheses of the macrocycles M1–M7 were performed under high‐dilution conditions. A “supramolecular” purification method was used for the small [2+2] macrocycles M3–M7, which separated selectively from the reaction mixture on recrystallisation from a dichloromethane/diethyl ether solution mixture. This proved to be an excellent method for purifying [2+2] macrocyclic ethers containing 1,1‐diphenylmethane moieties, and the separation was nearly quantitative. Molecular inclusion of dichloromethane in the cavities of noncovalently bonded macrocyclic ethers M2–M5 was studied by X‐ray diffraction in the solid state. Additionally, clathrate formation was found for macrocycles M1 (including diethyl ether), M2 (including water), M6 (including benzene) and M7 (including benzene).

Selective oxidation of ethylbenzene by dioxygen in the presence of complexes of nickel and cobalt with macrocyclic polyethers

The oxidation of alkylarenes by dioxygen in the presence of complexes of nickel and cobalt with macrocyclic ethers 18-crown-6 and 15-crown-5 was studied. The conditions for selective catalytic oxidation of ethylbenzene to α-phenylethyl hydroperoxide were determined. The kinetics of the accumulation of all oxidation products was studied. The order of the formation of the products at different stages of chain oxidation was determined. The activity of the complexes at the elementary stages of the chain oxidation of ethylbenzene is discussed.

Formation of substituted macrocyclic ethers by radical cyclisation

ω-Iodopolyoxaalkyl acrylates and related compoundsundergo radical cyclisation when treated with tributylstannane to afford substituted macrocylic polyethers.

ChemInform Abstract: Ring‐Opening of Crown Ether Macrocycles. Part 2. Template Effect in Ring‐Opening Reaction of Macrocycle of Formylbenzocrown Ethers under the Action of Amines with the Formation of Podands.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Molecular motion in crown ethers. Application of 13C and 2H NMR to the study of 4-carboxybenzo-24-crown-8 ether and its KNCS complex in solution and in the solid phase

Large-amplitude solid phase molecular motion has been detected in the macrocyclic ring of the title crown either via 13C CPMAS NMR. To study the details of the dynamic processes, two selectively deuterated d4 derivatives have been prepared and examined via 2H NMR as a function of temperature. A phase change occurring around 277 K has been verified by differential scanning calorimetry (DSC) and a model for the motional processes has been developed involving equivalent two-site flips of the CD2 groups. The amplitude of the CD2 motions apparently decreases the closer the group is to the aromatic ring. The influence of KNCS complexation on the 13C CPMAS spectrum and on 13C spin lattice relaxation times in solution has been explored. Key words: macrocyclic ethers, solid phase dynamics.

Enthalpic and volume effects in the interaction of d-glucose with crown ethers in water

The enthalpies of solution of 12-crown-4, 15-crown-5, 18-crown-6 and 1,10-diaza-18-crown-6 in aqueous d-glucose, were determined experimentally. The cross coefficients of the virial expansion of the excess enthalpies were calculated. On the basis of experimental density data, the limiting partial molar volumes of transfer of crown ethers from water to 1 m aqueous d-glucose solution were also evaluated. It is shown that the interactions between crown ethers and d-glucose are weak, but that the endothermic effect of these interactions decreases with an increase in the size of the crown ether macrocycle.

Ether lipids based on the glyceryl ether skeleton: Present state, future potential

AbstractLipids from natural sources consist mainly of saponifiable substances, such as glycerides, along with some unsaponifiable lipids, some of which are ether lipids. Typical ether lipids are monoalkyl ethers of glycerin, also called alkyl/alkenyl glyceryl ethers. Alkyl/alkenyl glyceryl ethers have also been reported in marine organisms and in human feces. Several chemical syntheses of such ether lipids have been reported. Typical examples are alkyl glyceryl ether formation by the addition reaction of alkyl glycidyl ether and the telomerization reaction of butadiene with glycerin and a transition metal catalyst. Characteristic chemical structures, such as terpene alkyl glyceryl ethers, archaebacterial macrocyclic ether lipids, and glyceryl ethers of condensed cyclic planar molecules, have been obtained as well. Over the past few decades, industry has shown much interest in the chemistry and application of highly branched fatty acids. For example, isostearyl glyceryl ether (GE‐IS) with methyl branching in the middle chain was already known, but it is now prepared at an industrial scale by proprietary alkyl glycidyl ether methods. The characteristic behavior of GE‐IS toward water, such as formation of water‐in‐oil emulsions containing large amounts of water and of liquid crystals, has made it applicable for use in hair and skin‐care cosmetics. Based on these studies and considerations, glyceryl ether lipids, which are rarely investigated, may become one of the most important and useful lipids in the industry.

Ion-dipole interactions of macrocyclic ethers using13C dipole-dipole relaxation time measurements. Part XI: The complexation of 1,4,7,10,13,16-hexaoxa-2,6-dioxocyclooctadecane with Ca2+ in CD3OH

The association constants,K a, of Ca2+ complexes with the nonequivalent binding site macrocycle,1,4,7,10,13,16-hexaoxa-2,6-dioxocyclooctadecane, were determined in CD3OH solution using13C dipole-dipole relaxation time,T 1 DD , studies. The measurements ofT 1 DD of the macrocyclic backbone for different stoichiometries (n:m) of complex formation were conducted under extreme narrowing experimental NMR conditions. The general equilibria given with 1/K a[L 0] n+m−1 = (1-nP′) n (1-mP′) m /P′ was used for identical cation and macrocyclic ether-ester concentrations in CD3OH and the association constants found were comparatively small depending on the cyclic ether-ester segments. The logK a values varied from 1.09 to 0.231 for 1 :1 and from 2.43 to 3.61 for 1 : 2 and from 2.29 to 4.24 for 2 : 1 ligand to cation complex stoichiometries.

Synthesis of novel crown ethers. Part 1. Coumestan and coumestan analog derivatives of crown ethers

The presented ethylenedioxy compounds5a,5d,6a and6c are examples of novel cyclic ethers, while macrocyclic polyethers represent new crown ether analogues. New coumestan-crowns5a-f, derivatives of 6,7-dihydroxy-3,4-dihydro-2H-dibenzofuran-1-one and 6,7-dihydroxy-3,3-dimethyl-3,4-dihydro-2H-dibenzofuran-1-one6a-e were synthesized from the correspondingo-dihydroxy compounds3a-b,4a-b and ditosylates or dichlorides of di- or triethylene glycol in the presence of K2CO3, in DMF/H2O (15/1) solutions at 65–75 °C for 35 hours. The structure of the macrocyclic ethers obtained were confirmed by1H-NMR,13C-NMR, IR spectra and elemental analyses.

Structural Criteria for the Rational Design of Selective Ligands. 2. Effect of Alkyl Substitution on Metal Ion Complex Stability with Ligands Bearing Ethylene-Bridged Ether Donors.

A novel approach is presented for the application and interpretation of molecular mechanics calculations in ligand structural design. The methodology yields strain energies that (i) provide a yardstick for the measurement of ligand binding site organization for metal ion complexation and (ii) allow the comparison of any two ligands independent of either the number and type of donor atoms or the identity of the metal ion. Application of this methodology is demonstrated in a detailed examination of the influence of alkyl substitution on the structural organization of ethylene-bridged, bidentate, ether donor ligands for the alkali and alkaline earth cations. Nine cases are examined, including the unsubstituted ethylene bridge (dimethoxyethane), all possible arrangements of individual alkyl groups (monoalkylation, gem-dialkylation, meso-dialkylation,d,l-dialkylation, trialkylation, and tetraalkylation), and both cis and trans attachments of the cyclohexyl group. The calculated degree of binding site organization for metal ion complexation afforded by these connecting structures is shown to correlate with known changes in complex stability caused by alkyl substitution of crown ether macrocycles.

Selective recognition of metal complexes by macrocyclic ethers: further observations on the macrocycle size dependence and the first-sphere ligand composition dependence of recognition thermodynamics

Additional studies of solution phase recognition of Ru(NH 3) x (pyridine) y 2+, Ru(NH 3) x (2,2′-bipyridine) y 2+ and Ru(NH 3) 4(1,10-phenantroline) 2+ species by dibenzo crown ethers are reported. The factors most closely examined were crown size, ammine ligand content and ancillary ligand composition. The overall study confirms that recognition or association derives primarily from H-bond formation (ammine hydrogen/ether oxygen. Evidently opposing these interactions, however, are crown conformational rearrangements. Consequently, straight-forward correlatins between association strength and potential number of H-bond interactions are found only in selected cases. Based on comparisons of association constants for (bis) pyridine, bipyridine and phenanthroline ligand-containing species with dibenzo crowns, evidence is also found for favorable polypyridine/benzene interactions. NMR (NOE) measurements indicate that the preferred association geometrics in solution are those that make each of the benzenes of the crown coplanar (or nearly coplanar) with the ligated polypyridine.

Langmuir-Blodgett Films of Triazolehemiporphyrazines: Evidence for Molecular Organization

Triazolehemiporphyrazine derivatives bearing crown ether macrocycles have been investigated in Langmuir and Langmuir-Blodgett films. Using infrared dichroism and ESR experiments and after careful assignments of infrared bands, the organization of these molecules within the LB multilayer has been characterized. These compounds form stacks of macrocycles and are tilted with respect to the normal of the substrate. These aggregates of about 50 molecules are partially oriented in the plane of the layers, showing that some ordering occurs during the transfer of the monolayer onto a solid substrate. This so-called stack-of-cards configuration is a first step to organize the crown ether groups in order to form ionic channels in LB films.

Structurally‐selective gas‐phase ion‐molecule reactions of dibenzo‐16‐crown‐5 compounds

AbstractSteric and substituent effects can play large roles in influencing the outcomes of organic reactions. In this work, the use of ion‐molecule reactions of dibenzo‐16‐crown‐5 compounds (lariat ethers) by tandem mass spectrometry to probe the influence of the pendant groups on the selectivity of their gas‐phase reactions was evaluated. Lariat ethers are macrocyclic ethers with pendant substituents that have been developed as new types of hosts for molecular recognition. Dimethyl ether (DME) was the reactant chosen because of its well characterized reactivity with various organic substrates possessing different functional groups. Only those dibenzo‐16‐crown‐5 compounds with no or at most one substituent at the center carbon of the three‐carbon bridge form the diagnostic [M + 13]+ product ion through a methylene substitution process. Dibenzo‐16‐crown‐5 compounds with geminal substituents on the center carbon of the three‐carbon bridge form the [M + 45]+ ion, but not the characteristic [M + 13]+ ion. Causative factors may be steric blocking of the reaction pathway by the geminal groups or a requirement for the presence of at least one hydrogen on the center carbon of the three‐center bridge for formation of the [M + 13]+ ion. CAD, deuterium labelling, molecular orbital calculations and comparisons with model compounds provide additional information about the reaction pathways.

発癌抑制作用を有するセンブラノイドＳａｒｃｏｐｈｙｔｏｌ Ａの全合成

The first total synthesis of sarcophytol A, an anticarcinogenic marine cembranoid, was achieved in a highly stereo- and enantioselective manner starting with (E, E)-farnesol ; it includes : 1) a newly developed Z-selective (Z : E=>35 : 1) Horner-Emmons reaction using a phosphonate nitrile, 2) a modified cyanohydrin macrocyclization, and 3) an enantioselective (93% ee) reduction of macrocyclic ketone as its key steps. Enantiomerically pure sarcophytol A was obtained by a single recrystallization. An improved synthetic process appropriate for a large-scale preparation using geraniol as the starting material was also developed. It included a new ketal Claisen rearrangement using 2, 2-dimethoxy-2, 3-dimethylbutan-2-ol for α-ketol isoprene elongation, which was applied to sequences for highly stereoselective (E>99%) synthesis of trisubstituted γ, δ-unsaturated aldehydes and acids. Enantiomers of macrocyclic ethers, (2Z, 4E) and (2E, 4Z), were obtained from a product of the ketal Claisen rearrangement via baker's yeast reduction. [2, 3]-Wittig rearrangement of these compounds afforded enantiomers of both sarcophytol A and T with high enantioselectivity (91-98% ee) in high yields. Surprisingly, almost perfect reverse chirality transfer was observed between these geometrical isomers, i.e. (R)-ether gave (S)-alcohol in (2Z, 4E) isomer, while (R)-alcohol in (2E, 4Z) isomer.

Solvents Effects on the Efficacy of Recognition of Amminemetal Complexes by Macrocyclic Ethers: In situ Probes of Extent of Encapsulation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSolvents Effects on the Efficacy of Recognition of Amminemetal Complexes by Macrocyclic Ethers: In situ Probes of Extent of EncapsulationXiao Lian Zhang, Christopher R. Kankel, and Joseph T. HuppCite this: Inorg. Chem. 1994, 33, 21, 4738–4743Publication Date (Print):October 1, 1994Publication History Published online1 May 2002Published inissue 1 October 1994https://doi.org/10.1021/ic00099a026RIGHTS & PERMISSIONSArticle Views58Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (731 KB) Get e-Alerts Get e-Alerts

Perturbation of the electronic structure of the Creutz-Taube ion via asymmetric encapsulation with macrocyclic ether species

Ligand-bridged mixed-valence ions can exist in either valence-localized double-minimum ground potential energy surface or valence-delocalized (single-minimum ground PE surface) form. The determining factor is the balance between twice the initial-state/final-state electroniccoupling energy (H[sub if]) and the sum of the zeroth-order reorganization or trapping energy ([chi]) and any redox asymmetry [delta]E. For the Creutz-Taube ion (NH[sub 3])[sub 5[minus]] Ru[sup 11][sup 1/2](NH[sub 3])[sub 5][sup 5+], (1), redox asymmetry is absent, the valencies are completely delocalized, and 2H[sub if] evidently exceeds [epsilon]. We reasoned, however, that [open quotes]electronic isomerization[close quotes] to a valence-localized form might be possible if significant redox asymmetry could be introduced. We report here the introduction of the desired asymmetry in an unusual way: via binding of a macrocyclic ether to just one of the two available ruthenium ammine sites. We also report optical evidence for the onset of valence localization in both 1 and a trans pyridine (py) substituted analog (2), in the presence of either dibenzo-36-crown-12(DB-36-C-12) or dibenzo-30-crown-10 (DB-30-C-10) species. 17 refs., 3 figs.

ChemInform Abstract: Synthesis and Crystal Structure of New Tetrathiafulvalene Derivatives Incorporated into Thiacrown Ether Macrocycles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Polycyclic trans-fused crown ethers from D-mannitol

New macrocyclic ethers, all bearing a common trans-fused chiral dioxepan moiety, were easily synthesized from 1,3:4,6-di- O-benzylidene- d-mannitol in 5 or 6 steps (3 examples). The influence of the substituent at C-1/C-6 positions upon conformation is discussed.