Macrocyclic Oligomers Research Articles

Synthesis of Macrocyclic Oligomers of Pivalolactone. Crystal Structure and Properties of Tetrolide

Synthesis of Macrocyclic Oligomers of Pivalolactone. Crystal Structure and Properties of Tetrolide

Oenotheins D, F and G, hydrolysable tannin dimers from Oenothera laciniata

Three new dimeric hydrolysable tannins, oenotheins D, F and G, together with known tannins including the macrocyclic oligomers, oenotheins A and B, have been isolated from roots and stems of Oenothera laciniata. Their structures were elucidated on the basis of chemical and spectral evidence. Oenotheins D and F were macrocyclic dimers isomeric with oenothein B in relation to the orientation of the valoneoyl groups linking the monomers.

Synthesis and Novel Free-Radical Ring-Opening Polymerization of Macrocyclic Oligomers Containing an Aromatic Sulfide Linkage

Synthesis and Novel Free-Radical Ring-Opening Polymerization of Macrocyclic Oligomers Containing an Aromatic Sulfide Linkage

Novel Polyaromatic Quinone Imines

A novel synthetic route to poly(quinone imines) has been developed. Reaction of anthraquinone (AQ) with aromatic diamines in the presence of TiCl 4 and DABCO as base in refluxing chloro- or o-dichlorobenzene led to high molecular weight polymers with the poly(quinone diimine) structure. Polymerization of AQ with methylene-4,4'-dianiline resulted in a mixture of high molecular weight polymer (M w 15 000) and oligomeric macrocycles. The polymerization of AQ was also accomplished with 4,4'-oxy- and 4,4'-thiodianiline, as well as with p-phenylenediamine. The latter polymer is the dibenzo analog of the pernigraniline base form of polyaniline. tert-Butylanthraquinone was also successfuly used as a comonomer with the various aromatic diamines. All these polymers are red in color, soluble in organic solvents, and film-forming. Polymerizations of the aromatic diamines with heterocyclic-substituted benzoquinones, such has benzo[1,2-b:4,5-b']dithiophene-4,8-dione, 2,2'-dialkylbenzo[1,2-d:5,4-d']dioxazole-4,8-dione, and N,N',2,2'-tetraalkylbenzo[1,2-d:5,4-d']imidazole-4,8-dione, were also investigated

Use of calixarenes to modify selectivities in capillary electrophoresis

Calixarenes are macrocyclic oligomers having the shape of a conical vase. Its inner cavity can accomodate various guest molecules, in similarity to other macrocyclic molecules such as crown ethers and cyclodextrins. Thus, calixarenes can be used to manipulate selectivities in chromatography and in capillary electrophoresis. We report here initial results that demonstrate the value of calixarenes as selectivity modifiers in capillary electrophoresis. Retention behaviors of chlorinated phenols, benzenediols, and toluidines in the presence of p-sulfonate calix[6]arene was investigated

Stereospecific polymerization of methylthiirane in homogeneous phase, 3. Study of the enantioasymmetric process

AbstractEnantioasymmetry was studied for polymerizations of methylthiirane initiated by bis(isopropyl‐S‐cysteinato)cadmium and run in bulk. The ratio of rates of consumption of the two antipodes is independent of their concentrations. The enantioasymmetric constant kR, measuring the preferential choice of the R‐antipode, is depending on both the relative number of the two types of active sites and on their reactivities. An effect on enantioasymmetry of the molecular weight of the growing chains bearing the active sites, is occurring with two distinct stages: The first one is observed, with an enantioasymmetric constant kR = 1,5, from the appearance of stereospecificity up to molecular weights of 35000 (for the main chain) and the second one with kR = 1,07 for molecular weights higher than 35000. In the first stage, the cysteinato end group of the oligomer chain remains linked to cadmium (by cadmium‐nitrogen complexation) and the two active sites are diastereoisomers having different reactivities. In the second stage, the macrocyclic oligomer becomes too large and cadmium‐nitrogen interaction is suppressed. The active sites are now enantiomers having the same reactivity. In this case, enantioasymmetry depends only on the unbalance between the amounts of the two types of active sites. The maximum size the macrocyclic oligomer can reach depends on the initiator concentration.

On the Utility of 13C (CPMAS) NMR in Conformational Studies of Simple Hydroxy‐, Alkoxy‐ and Acetoxycalixarenes in the Solid State

AbstractThe potentiality of 13C (CPMAS) NMR as a conformational probe for the oligomeric macrocycles p‐(tert‐butyl)calix‐[n]arenes (n = 4, 6, 8) and their alkoxy/acetoxy derivatives in the solid state is explored.

A model of the kinetics of macrocyclic BPA carbonate formation

AbstractCyclic oligocarbonates are synthesized by two‐phase interfacial reactions of aryl bischloroformates in the presence of an amine phase transfer catalyst and an alkali: nClOCOArOCOCl + 4nNaOH → (OArOCO)n + 2nNaCl + nNa2CO3 + 2nH2O. The organocarbonate product may be a macrocyclic oligomer or a linear chain polymer. A qualitative mechanism for this behavior has been proposed by Brunelle, Boden, and co‐workers. Four steps are identifiable: activation of the aryl bischloroformate by the amine catalyst, hydrolysis of a portion of this intermediate at the aqueous/organic phase interface, oligomerization between activated and hydrolyzed moieties also at the interface, and chain terminating carbamate formation that leads to polymer. An important modification is made within the framework of the Brunelle and Boden mechanism. While the intramolecular cyclization reaction is formally second‐order overall, it behaves as a first‐order process. The kinetic constants for both this pseudo‐first‐order cyclization step and the corresponding second‐order linearization step are simply related. It is speculated that the above relationship can be generalized for a whole class of pseudo‐first‐ and second‐order rate constants for similar macrocyclic reactions.

Gel electrophoretic analysis of DNA branched junctions

Gel electrophoresis has provided much of the detailed information we have about the properties of DNA junctions, stable branched molecules formed from oligonucleotide or polynucleotide strands. Here we review these applications, and present the results of an electrophoretic investigation of conformationally restricted junctions formed by covalently connecting two different pairs of strands in a junction with four arms. Native gel electrophoresis is employed to establish the formation and stoichiometry of the multistrand complexes. Ferguson analysis of native gel mobility shows that junctions have retardation coefficients that are distinct from those of linear DNA duplexes. Denaturing gel electrophoresis is the primary tool for characterizing junctions that have been covalently linked together to form both linear and macrocyclic oligomers of junctions (oligojunctions). Radioactively labelled strands enable one to monitor the progress of the ligation reaction: both linear and closed cyclic molecules result, and these can be distinguished by applying Ferguson analysis to denaturing gels. Combinations of exonuclease III, restriction enzymes and sequencing reactions have been applied to oligojunction molecules, and the results are all analyzed on denaturing gels. Junctions containing intramolecular "tethers" that restrict the conformation freedom of the complex comprise a new system for analyzing the conformations of branched molecules. In these tethered junctions, the ability of arms to move relative to each other is restricted substantially by covalently connecting pairs of arms in the original complex with short, flexible loops. The two tethers used here constrain the helical domains of the structure to be roughly parallel or anti-parallel. In this article, we use Ferguson analysis to compare two tethered junctions with an untethered junction. At high gel concentrations, the mobility of the untethered complex is found to be closer to that of the molecule tethered anti-parallel than to the one tethered parallel. Curvature in the Ferguson plots for all three of these junctions is detected over a range of compositions. At low gel concentrations, differences in electrophoretic mobility persist, suggesting that the untethered junction differs in charge as well as conformational freedom from the tethered analogs. We expect that studies of this kind will be able to define the conformational repertoire of junctions of different kinds, and to explore the effects of electrophoresis on these states.

Solid state studies on p.t-butyl-calix[6]arene derivatives

Calix[n]arenes1 (1) are a class of phenol-formaldehyde macrocyclic oligomers which exhibit different sizes and shapes depending on the number of phenolic units in the cyclic array and on the nature of substituents on the aromatic nucleus (R1) and on the phenolic oxygen (R2).

Ring‐opening polymerization with kinetically controlled enhancement of macrocyclic oligomers or linear macromolecules

AbstractThe equilibrium and the kinetics of the ring‐opening polymerization accompanied with backbiting and end‐to‐end ring closure are analyzed using computer simulation. The influence of monomer ring strain and competition between back‐biting and end‐biting on the overall kinetic process is evaluated. The results of calculations are compared with examples from the ionic ring opening polymerization of heterocyclic monomers. It is established that in the polymerization of nonstrained monomers fast end‐biting manifests itself by an induction period. In the absence of end‐biting the polymerization of strained monomers yields a system in which the polymer concentration is temporarily higher than at equilibrium (kinetic enhancement in polymer). On the other hand, very fast end‐biting, hindered only in the case of the monomeric species by the ring strain, results in concentrations of the macrocyclics which are transitorily higher than the corresponding equilibrium concentrations (kinetic enhancement of macrocycles). The polymer synthesis with kinetically controlled concentration of cyclics is indicated.

Cavitands containing cleft- and collar-shaped voids

Macrocyclic oligomers (cavitands) composed of four or six ethyl-substituted dibenzofuran units are reported which contain enforced concave inner surfaces large enough to embrace a variety of organic compounds.

Kinetically controlled formation of macrocyclic oligomers in the ring‐opening polymerization

AbstractKinetic schemes are solved for polymerization systems involving competition between linear growth and cyclisation by back‐biting to an optional chain unit and/or to the last unit (end‐to‐end ring closure). A fast reaction of a growing centre with an end group may lead to a situation, called here “kinetic enhancement in macrorings”, in which the transient concentration of cyclics formed in polymerization system exceeds their equilibrium concentration. Sometimes, a peculiar kinetics may be observed in which propagation proceeds on linear active macromolecules, but the polymerization leads almost exclusively to the cyclic products. On the other hand, fast propagation due to a high reactivity of monomer may lead to kinetic reduction of macrorings. Several situations are considered with examples taken from cationic polymerization of cyclic acetals and siloxanes (kinetic enhancement) or anionic polymerization of ϵ‐caprolactone (kinetic reduction). Kinetic schemes are numerically solved by computer for some arbitrarily assumed rate constants. This is the first paper of a series aiming to relate the kinetically controlled concentration of macrorings to the polymerization mechanism and the numerical values of the rate constants.

ChemInform Abstract: PREPARATION OF DERIVATIVES AND ANALOGS OF THE MACROCYCLIC OLIGOMERS OF ETHYLENE OXIDE (CROWN COMPOUNDS)

Chemischer InformationsdienstVolume 11, Issue 23 Reviews ChemInform Abstract: PREPARATION OF DERIVATIVES AND ANALOGS OF THE MACROCYCLIC OLIGOMERS OF ETHYLENE OXIDE (CROWN COMPOUNDS) J. S. BRADSHAW, J. S. BRADSHAWSearch for more papers by this authorP. E. STOTT, P. E. STOTTSearch for more papers by this author J. S. BRADSHAW, J. S. BRADSHAWSearch for more papers by this authorP. E. STOTT, P. E. STOTTSearch for more papers by this author First published: June 10, 1980 https://doi.org/10.1002/chin.198023342Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue23June 10, 1980 RelatedInformation

Preparation of derivatives and analogs of the macrocyclic oligomers of ethylene oxide (crown compounds)

Preparation of derivatives and analogs of the macrocyclic oligomers of ethylene oxide (crown compounds)

The mechanism of co-oligomerization of tetrahydrofuran with propylene oxide in the presence of methacrylic anhydride

A study was made of the effect of the order of adding propylene oxide (PO) and a catalyst on process mechanism, molecular weight and functionality of oligomers formed by co-oligomerization of tetrahydrofuran with PO by the action of SbCl5 in the presence of methacrylic ahnydride (MA). It was shown that MA takes no part in practice in initiation of oligomerization. Chain extension is effected on active centres of the type of cyclic zwitterions and ionic pairs of different properties of counterions. The ratio of these active centres depends on the order or adding PO and the catalyst. A possible mechanism of adding methacrylate groups into oligomer molecules is described. The overall functionality in relation to methacrylate groups and chlorine of oligomers obtained on adding PO after SbCl5 is higher than for oligomers synthesized on adding the catalyst into a monomer-MA mixture, but is less than 2 in both cases. The lack of functional groups may be due to the presence of macrocyclic oligomers.