Terpolymerization of Cyclic Ethers with Cyclic Anhydride

Abstract

A unique solution polymerization and polymer family have been discovered in the ring-opening terpolymerization of three heterocyclic monomers initiated by organometallic compounds, particularly trialkylaluminum. The products have repeating ether-ester-ester linkages along the chain and are alternating terpolymers, … ABCABCABC…, of three different monomers A, B, and C. Monomer A is a four- or five-membered cyclic oxide, such as tetrahydro-furan or oxocylobutane (oxetane). Monomer B is an epox-ide, and Monomer C is a cyclic acid anhydride. Many epoxides and anhydrides participate in the polymerization which enables the preparation of alternating terpolymers containing various substituents and unsaturatlons at regu-lar intervals along the chain. The alternating sequence can be near-perfect or less so depending on the initial monomer charge ratio. Evidence of the alternating struc-ture was obtained by chemical and NMR analyses of polymer sampled at intermediate and final conversions, and by glass transition temperatures.     

Cyclic polysiloxanes

The preparation, fractionation and characterisation of synthetic cyclic polysiloxanes (R(CH₃)SiO)_x are reviewed. Particular emphasis is given to the cyclic poly(dimethylsiloxanes) (PDMS) (R is CH₃) cyclic poly(phenylmethylsiloxanes)(PPMS) (R is C₆H₅) and cyclic poly(vinylmethylsiloxanes) (PVMS) (R is CH₂=CH). The application of high performance liquid chromatography (HPLC) and analytical and preparative gel permeation chromatography (GPC) to the preparation and characterisation of cyclic polysiloxanes is discussed. The methods include preparation of sharp fractions of relatively high molar mass cyclic polymers (with heterogeneity indices typically ca. 1.05) and comparison of the GPC and retention volumes of cyclics with the corresponding linear polymers. Investigations of the cyclic polymers prepared have been made using a number of experimental methods and techniques. These include dilute solution viscometry and low angle neutron scattering. Comparisons are drawn between cyclic PDMS and other cyclic polysiloxanes and also between cyclic polysiloxanes and the corresponding commercially-important linear polymers.     

Cyclic Sulfinamides

The literature on cyclic sulfinamides (put simply, sultims) published from 1989 to 2022 has been summarized and reviewed. The information is divided into two sections: the analysis of synthetic methods on the preparation of cyclic sulfinamides and the discussion of the chemical properties of cyclic sulfinamides focusing on their reactions and applications. The survey of the reaction conditions, provided in the most detailed way, and a critical view of the reaction mechanisms add an extra dimension to the text. The data presented will be useful to specialists in different areas, especially those who work in the field of synthetic organic and pharmaceutical chemistry.     

Cyclic hydrazides

A series of dimethyl esters and cyclic hydrazides of quinoline-2,3-dicarboxylic acid has been synthesized with different substituents in the benzene ring.Latvian Institute of Organic Synthesis, Riga LV-1006, Merz and Co., 111353, 60048 Frankfurt am Main, Germany. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 86–100, January, 1998.     

Cyclic beta-peptoids

The first synthesis of functionalized beta-peptoid macrocycles is reported. X-ray crystallographic structure of tetramer 9 reveals a C2-symmetrical derivative with unexpected all-cis-amide bonds and spatial disposition of the appendages toward the two opposite faces of the ring. Quantum calculations suggest that 9 is locked in this layout. These macrocycles constitute novel promising templates for multimeric ligation of biologically active ligands. The concept was exemplified by chemical decoration of tetramer 9 via "click" reactions.     

Cyclic peptoids

Foldamers are an intriguing family of biomimetic oligomers that exhibit a propensity to adopt stable secondary structures. N-Substituted glycine oligomers, or "peptoids", are a prototypical example of these foldamer systems and are known to form a helix resembling that of polyproline type I. Ongoing studies seek to improve the stability of peptoid folding and to discover new secondary structure motifs. Here, we report that peptoids undergo highly efficient head-to-tail macrocyclization reactions. A diverse array of peptoid sequences from pentamers to 20mers were converted to macrocyclic products within 5 min at room temperature. The introduction of the covalent constraint enhances conformational ordering, allowing for the crystallization of a cyclic peptoid hexamer and octamer. We present the first X-ray crystallographic structures of peptoid hetero-oligomers, revealing that peptoid macrocycles can form a reverse-turn conformation.     

Polymerization of Cyclic Ethers

Abstract

In the present series of studies on the cationic polymerization of cyclic ethers, the reactivities of cyclic ethers were quantified and the effect of the catalyst upon the polymerization kinetics was revealed. These kinetic analyses were successfully performed by means of our “phenoxyl end-capping method”. The change of the reactivity by the ring size of the monomer was interestingly demonstrated. In addition, it is emphasized that the frequency factor as well as the activation energy influence the rate constant of propagation. As to the effect of catalyst upon the polymerization kinetics, the most important conclusion is that the rate constant of propagation changes very little according to the changes of the catalyst components. Variation of the conversion rate by a change of catalyst is due to differences in the rates of the initiation and the termination reactions.     

Cyclic dimers of tetrafluorobutatriene

1,1,4,4-Tetrafluorobutatriene polymerizes even at ?78?°C within a short time yielding a red insoluble polymer. Possible closed-shell cyclic dimers and oligomers resulting from several reaction paths were analyzed by computational methods??with CCSDT/cc-pVTZ as the highest order calculation and several other calculations of lower level. For a better understanding of fluorination effects, the perhydrogen triene dimers were included in this study. The destabilization of the central cumulenic double bond of tetrafluorobutatriene relative to ethylene and the further destabilizing fluorine substitution makes the formation of most of the dimers exothermic with only one exception for the perfluoro derivatives. Astonishingly, the geometry of some of the discussed molecules is highly affected by fluorine substitution, while for others there is nearly no effect on the geometry of the carbon backbone. ¹⁹F-NMR shifts of the potential dimers were calculated using the GIAO method.     

Synthesis of Cyclic Hydroxyureas

N-Benzyloxyureas can be alkylated with 1, 2 and 1, 3-dibromoalkanes and subsequently deprotected to provide 1-hydroxy-3-alkyl or 3-aryl imidazolidinones and tetrahydropyrimidinones.     

Cyclic voltammetry of phenol

The possibility of phenol determination by cyclic voltammetry (CVA) on electrochemically modified glassy-carbon electrodes (GCE) was studied. The effect of the rate of linear potential sweep on the sensitivity of phenol determination was investigated. The adsorption nature of the analytical signal of phenol was revealed. The formation of the hydroquinone-quinone couple by the electrochemical oxidation of phenol was proved by CVA.     

Reactive Polymers and Oligomers from Cyclic Ethers and Cyclic Sulfides

(2-Bromoethyl)oxirane is converted in 39% yield to poly-[(2-bromoethyl)oxirane] of inherent viscosity 1.99 dL/g. The AlEt₃/H₂O/AcAc system is a very effective initiator for the polymerization of (2-bromoethyl)oxirane. Poly[(2-bromoethyl)-oxirane] is a white elastomer, soluble in CHCl₃ and insoluble in CH₃OH. Polyether-urethane hydrogels are prepared by the room temperature crosslinking of poly[(3-hydroxypropyl)oxirane] with aliphatic or aromatic diisocyanates. These networks absorb 100–200% of their weights in water, and can be prepared in transparent form with potential application as biomaterials or contact lenses.     

Cyclic staircase voltammetry

The use of cyclic staircase voltammetry was investigated in order to study kinetic mechanisms at low concentration levels. The reversible case for c.s.c.v. was studied along with two common kinetic cases: e.c. and catalytic mechanism. For both the e.c. and catalytic case, it was possible to correlate the peak current ratio with the rate constant with one working curve regardless of the step size, the step time or the time in the step in which the current was measured. For the catalytic mechanism, the increase in the peak current of the forward peak can also be correlated with the rate constant, once again regardless of the experimental parameters. Using this technique, high sensitivity can be obtained at low concentrations and fast scan rates as was shown by comparing c.s.c.v. with cyclic voltammetry for micromolar cadmium solutions. The use of staircase voltammetry for the study of the catalytic reaction between iron (III)-triethanolamine and hydroxylamine was demonstrated and a rate constant of 180 M^?1 s^?1 was obtained, which is consistent with previous work.     

Cyclic β-aminovinylimines

2-Substituted 1-phenylamino-3-phenyliminoindenes have been found to be readily oxidized by atmospheric oxygen. The structure of the resulting 3-aryl-3-hydroxy-2-phenyl-4-phenyliminodihydroisoquinol-1-ones has been shown by chemical and spectroscopic methods. The comparative oxidizability of enamines of several types is discussed on the basis of quantum-mechanical calculations by the LCAO MOH method.For part V, see [1].     

Cyclic unsaturated compounds

Conclusions Reversible structural isomerization of 1,3- and 1,2-dimethylsubstituted cyclopentadienes, proceeding according to a mechanism of 1,2-shift of the methyl group from the 5-position of the cyclopentadiene ring, accompanied by the migration of the system of intracyclic double bonds, is carried out at the temperatures 400–500°. In conjunction with the 1,2-shift of hydrogen, the indicated conversion leads to the formation of an equilibrium mixture of structural isomers, containing 38% 1,3-dimethylcyclopentadienes and 62% 1,2-and 2,3-dimethylcyclopentadienes (total).For communication 36 of this series, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1978–1983, September, 1971.     

Cyclic capillary electrophoresis

A strategy is described here for increasing both the resolution and the flexibility of capillary electrophoresis performed in a sieving medium of ungelled polymer. This strategy is based on analysis and, sometimes, re-analysis that is done in several stages of constant-field electrophoresis. Enhancement-stages are between the analysis-stages. An enhancement-stage (i) increases the separation between peaks, while (ii) moving DNA molecules in the reverse direction. An enhancement-stage is based on an electrophoretic ratchet generated by a pulsed electrical field that can be zero-integrated. The ratchet-generating pulses are longer than the field pulses that have previously been used to improve the resolution of DNA molecules. No limit has been found to the resolution enhancement achievable. Apparently, diffusion-induced peak broadening is inhibited and, in some cases, may be reversed by the ratchet. The enhancement-stages are critically dependent on the electrical field-dependence of a plot of electrophoretic mobility as a function of DNA length. To generate the pulsed electrical field, a computer-controlled system with a time resolution of 30 microseconds has been developed. Programming is flexible enough to embed other pulses within ratchet-generating pulses. These other pulses can be either the previously used, shorter field-inversion pulses or high-frequency periodic oscillations previously found to sharpen peaks.     

Cyclic modular beta-sheets

The development of peptide beta-hairpins is problematic, because folding depends on the amino acid sequence and changes to the sequence can significantly decrease folding. Robust beta-hairpins that can tolerate such changes are attractive tools for studying interactions involving protein beta-sheets and developing inhibitors of these interactions. This paper introduces a new class of peptide models of protein beta-sheets that addresses the problem of separating folding from the sequence. These model beta-sheets are macrocyclic peptides that fold in water to present a pentapeptide beta-strand along one edge; the other edge contains the tripeptide beta-strand mimic Hao [JACS 2000, 122, 7654] and two additional amino acids. The pentapeptide and Hao-containing peptide strands are connected by two delta-linked ornithine (deltaOrn) turns [JACS 2003, 125, 876]. Each deltaOrn turn contains a free alpha-amino group that permits the linking of individual modules to form divalent beta-sheets. These "cyclic modular beta-sheets" are synthesized by standard solid-phase peptide synthesis of a linear precursor followed by solution-phase cyclization. Eight cyclic modular beta-sheets 1a-1h containing sequences based on beta-amyloid and macrophage inflammatory protein 2 were synthesized and characterized by 1H NMR. Linked cyclic modular beta-sheet 2, which contains two modules of 1b, was also synthesized and characterized. 1H NMR studies show downfield alpha-proton chemical shifts, deltaOrn delta-proton magnetic anisotropy, and NOE cross-peaks that establish all compounds but 1c and 1g to be moderately or well folded into a conformation that resembles a beta-sheet. Pulsed-field gradient NMR diffusion experiments show little or no self-association at low (相似文献