Sec-ammonium Salt Research Articles

Synthesis and kinetic resolution of directional isomers of [2]rotaxanes bearing a lariat crown ether wheel

ABSTRACT Rotaxanes can have topological isomers because of their mechanically interlocked axle and wheel components. Directional isomers are formed when the rotaxanes are constructed using an asymmetric axle and a three-dimensional non-symmetrical wheel. In this work, directional isomers of [2]rotaxanes were synthesised using lariat dibenzo-24-crown-8 ether as a non-symmetrical wheel component and a sec-ammonium salt axle. Control over the directional isomer ratio of [2]rotaxanes was achieved, as demonstrated by kinetic resolution via N-acetylation of the [2]rotaxanes.

Acylative Uni-directional Transport on Level Periodic Potential Surface Using a Rotaxane Platform with a Isopropylidene Separator

A rotaxane consisting of DB24C8 and sec-ammonium salt that has a Troc-protected ammonium group beyond an isopropylidene separator was prepared. After rapid acylation of the ammonium moiety to trans...

Directed one-pot syntheses of crown ether wheel-containing main chain-type polyrotaxanes with controlled rotaxanation ratios.

The directed synthesis of main chain-type polyrotaxanes possessing crown ether wheels was successfully achieved through two methods, A and B. Method A involved the direct wheel threading of poly(sec-ammonium salt) followed by end-capping with a bulky group, while method B utilized polyaddition of a pseudo[2]rotaxane monomer to facilitate the control of the structure, i.e. the rotaxanation ratio.

An efficient synthetic entry to rotaxanes utilising reversible cleavage of aromatic disulphide bonds

Reversible cleavage of an aromatic disulphide bond of a dumbbell-shaped molecule having two sec-ammonium salt moieties enabled the insertion of the disulphide linkage through a crown ether to give the corresponding [2]- and [3]rotaxanes. The formation of the rotaxanes proceeded much more rapidly than the case of an aliphatic disulphide system.

Synthesis of Main-Chain-Type Polyrotaxanes by New Click Polymerization Using Homoditopic Nitrile N-Oxides via Rotaxanation−Polymerization Protocol

Main-chain-type poly[2]rotaxanes (9 and 12) and poly[3]rotaxanes (10 and 13) were synthesized by a new click polymerization using unstable and stable homoditopic nitrile N-oxides according to rotaxanation and polymerization protocol. Rotaxane monomers were prepared from ethynyl-functionalized crown ether and sec-ammonium salt via the typical urethane end-capping protocol. The homoditopic nitrile N-oxide 8′ was generated in situ through the reaction of the corresponding hydroxamoyl chloride 8 with molecular sieves 4 Å. The click polymerization of diethynyl-functionalized [2]rotaxane 5 and [3]rotaxane monomer 7 with 8′ efficiently proceeded in the absence of a catalyst to afford well-defined polyrotaxanes 9 and 10 containing a polyisoxazole backbone in high yields. The polymerization of a newly developed kinetically stabilized homoditopic nitrile N-oxide 11 with rotaxane monomers yielded well-defined polyrotaxanes 12 and 13 in high yields under similar conditions. The structures of poly[2]rotaxanes (9 and 12) and poly[3]rotaxanes (10 and 13) were confirmed by 1H NMR, SEC, and IR analyses. The properties of polyrotaxanes such as solubility and thermal stability were evaluated. These polyrotaxanes showed relatively high thermal stability and good film-forming property based on their good solubility toward ordinary organic solvents.

Synthesis of acetylene-functionalized [2]rotaxane monomers directed toward side chain-type polyrotaxanes

A crown ether–ammonium salt-type rotaxane monomer was synthesized in a high yield using dibenzo-24-crown-8-ether and sec-ammonium salt having a hydroxy terminal by means of an end-capping reaction with an ethynyl benzoic acid. Its N-acetylated derivative was also synthesized in a quantitative yield using excess acetic anhydride and triethylamine. Novel side chain-type polyrotaxanes, that is, ammonium-type and neutral polyphenylacetylenes tethering rotaxane moieties in side chains with high molecular weights, were obtained in high yields by polymerizations with an Rh catalyst. The structures of the polymers were characterized by infrared, ultraviolet-visible (UV-vis) spectra and size exclusion chromatography. N-acetylation of the rotaxane moieties of the ammonium salt-type polymer resulted in the formation of a reddish-colored neutral polymer showing red-shifted UV-vis absorptions around 500 nm based on the conjugated main chain, according to the structural change of rotaxane side chains, that is, the change of the distance of the wheel component to the polyacetylene main chain. The solubility of the polymers was evaluated. A crown ether–ammonium salt-type rotaxane monomer was synthesized in a high yield using dibenzo-24-crown-8-ether and sec-ammonium salt having a hydroxy terminal by means of an end-capping reaction with an ethynyl benzoic acid. Its N-acetylated derivative was also synthesized as a neutral monomer. Novel side chain-type polyrotaxanes, that is, ammonium-type and neutral polyphenylacetylenes tethering rotaxane moieties in side chains with high molecular weights were obtained in high yields by polymerizations with an Rh catalyst. N-acetylation of the rotaxane moieties of the ammonium salt-type polymer afforded a red-colored neutral polymer showing red-shifted UV-vis absorption due to the conjugated main chain, according to the change in distance between the wheel component and the polyacetylene main chain.

Synthesis and Characterization of Poly[3]rotaxane through the Mizoroki-Heck Coupling Polymerization of Divinyl-functionalized [3]Rotaxane

Main chain-type poly[3]rotaxanes were synthesized according to the rotaxanation-polymerization protocol by the polymerization of a divinyl [3]rotaxane monomer through the Mizoroki-Heck coupling with a diiodoarene. [3]Rotaxane 5 consisting of two monovinyl dibenzo-24-crown-8-ether wheels (2) and sec-ammonium salt (3) as an axle component was synthesized in 86% yield by a typical urethane end-capping reaction of the axle terminal hydroxyl group with bis(4-isocyanophenyl)methane in the presence of a catalytic amount of di-n-butyltin dilaurate. Quantitative N-acetylation of 5 yielded mono(vinylphenyl)-functionalized wheel-containing [3]rotaxane monomers 6. The mobility of the wheel components in [3]rotaxanes was evaluated by the two-dimention NOESY spectra of 5 and 6. The main-chain type poly[3]rotaxanes 8 were obtained in high yields by the Mizoroki-Heck-type polycondensation of 6 and diiodoarenes 7 in the presence of a palladium catalyst (Pd(OAc)2). The structures of the polyrotaxanes were determined mainly by NMR and GPC, while the IR spectra showed that vinylene groups formed mainly took the trans configuration. Properties of the polyrotaxanes such as solubility and thermal stability were evaluated.

Synthesis of A Main Chain-Type Polyrotaxane Consisting of Poly(crown ether) and sec-Ammonium Salt Axle and Its Application to Polyrotaxane Network

According to the molecular design, a main chain-type polyrotaxane (B) was synthesized by the initial threading of sec-ammonium axle 5 into poly(crown ether) 3 to polypseudorotaxane 7 followed by end-capping of the axle terminal with a bulky aromatic isocyanate. The pseudorotaxane formation using poly(crown ether) 3 was studied in detail from viewpoints of effects of solvent, temperature, concentration, feed ratio, and so on. The complete pseudorotaxanation (>99%) was achieved, while the incorporation ratio of the axle moiety was finely controllable, by changing the feed ratio of 3 and 5. The corresponding polyrotaxane 8 was obtained in a high yield and in a high rotaxanated ratio by the end-capping of 7 with 3,5-dimethylphenyl isocyanate. N-Acetylation of 8 with acetic anhydride afforded neutral polyrotaxane 9 of which molecular weights could be estimated by GPC. Polypseudorotaxane 7 was utilized for the preparation of a new type of polyrotaxane network: the reaction of 7 with 4,4′-methylenebis(phenyl isocyanate) (MDI) which combined terminal OH group of the axle of 7 yielded a gelled materials 10. The gel was swollen in polar solvents such as dimethyl sulfoxide (DMSO, 9800%) to give transparent material. 1H NMR spectrum of 10 indicated the formation of the rotaxane structure as crosslinking point, although the degree of crosslink was low.

メタセシス反応を用いた側鎖型ポリロタキサンの合成

A new methacrylate monomer having a sec-amine, a triphenylmethyl group, and an internal olefin was synthesized. The polymer obtained by radical polymerization of the monomer was deprotected with trifluoroacetic acid, followed by washing with a saturated solution of NH4PF6 to afford the corresponding polymer having a sec-ammonium salt unit. The synthesis of side-chain-type polyrotaxane was carried out with the polymer and dibenzo-24-crown-8 ether in the presence of ruthenium carbene complex (Grubbs 1st catalyst). The resulting polymer was insoluble. The IR spectra suggested that the obtained polyrotaxane contained crosslinking structures.

Polyrotaxane and Polyrotaxane Network: Supramolecular Architectures Based on the Concept of Dynamic Covalent Bond Chemistry

This review article concerns with the syntheses of polyrotaxanes and polyrotaxane networks that can be constructed mainly on the basis of the concept of dynamic covalent bond chemistry. At the beginning of the review, synthetic methods of rotaxanes are briefly summarized along with several high yielding preparations. Synthesis of poly[3]rotaxane by the reaction of homoditopic monomers utilizing the thiol-disulfide interchange reaction was discussed in detail, among polyrotaxanes possessing topological bonds for the monomer linking in the main chain. Polyrotaxane network was prepared by a similar protocol from a polyfunctional crown ether and a dumbbell-shaped homoditopic axle containing two sec-ammonium salt moieties and centrally located disulfide bond. Some characteristics of the polyrotaxane network were demonstrated, including the recyclable property as the crosslinked polymer. The meaning and applicability of the reversible crosslinking/decrosslinking system developed in the polyrotaxane network are specially emphasized for unique and potential application.

Synthesis and Shuttling Behavior of Rotaxanes Consisting of Crown Ether Wheel and Disulfide Dumbbell with Two Ammonium Centers.

Several [2]- and [3]rotaxanes bearing some functional groups on their wheel components and spacers with different lengths between two ammonium centers on their dumbbell components were prepared in good yields from dibenzo-24-crown-8-ether derivatives and dumbbell-shaped bis(sec-ammonium salt)s having a centrally located disulfide linkage, by utilizing the reversible thiol-disulfide interchange reaction. The shuttling behaviors of the [2]rotaxanes were investigated by 1 H NMR by use of the spin polarization transfer-selective inversion recovery technique. It was found that the change in spacer length in the axle resulted in a drastic change in shuttling rate of the [2]rotaxanes, although the introduction of the functional groups to the wheels did not affect the shuttling behavior at all.

Synthesis and Shuttling Behavior of Rotaxanes Consisting of Crown Ether Wheel and Disulfide Dumbbell with Two Ammonium Centers

Several [2]- and [3]rotaxanes bearing some functional groups on their wheel components and spacers with different lengths between two ammonium centers on their dumbbell components were prepared in good yields from dibenzo-24-crown-8-ether derivatives and dumbbell-shaped bis(sec-ammonium salt)s having a centrally located disulfide linkage, by utilizing the reversible thiol-disulfide interchange reaction. The shuttling behaviors of the [2]rotaxanes were investigated by 1 H NMR by use of the spin polarization transfer-selective inversion recovery technique. It was found that the change in spacer length in the axle resulted in a drastic change in shuttling rate of the [2]rotaxanes, although the introduction of the functional groups to the wheels did not affect the shuttling behavior at all.

Dynamic Covalent Chemistry in Rotaxane Synthesis. Slipping Approach to [2]Rotaxane Utilizing Reversible Cleavage–Rebondage of Trityl Thioether Linkage

Abstract A [2]rotaxane was synthesized in a high yield from a dumbbell-shaped sec-ammonium salt having trityl thioether and 3,5-di-t-butylphenyl groups at the both ends and dibenzo-24-crown-8-ether, through the slipping, utilizing the reversible cleavage–rebondage of the trityl thioether linkage.

Highly efficient synthesis of [3]- and [5]-rotaxanes consisting of crown ether and a sec-ammonium salt.

[3]- and [5]-rotaxanes consisting of crown ether and ammonium salts were synthesized in high yields by a tributylphosphine-catalyzed end-capping method which provides a simple and practical means of obtaining higher-order rotaxanes.