Crown ether derivative having two ammonium salts and method for synthesizing the same, and slipped rotaxane

Abstract

To provide, for a slipped rotaxane polymer for which diverse applications such as pressure-resistant materials are envisaged, a simple and rigid crown ether derivative having two ammonium salts, a method for synthesizing the same, and a slipped rotaxane.SOLUTION: A crown ether derivative having two ammonium salts represented by the following chemical formula (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a crown ether derivative having two ammonium salts, a method for synthesizing the same, and an intercalated rotaxane. [Background technology]

[0002] A rotaxane is a molecular complex (supramolecular compound) in which an axial molecule (axial molecule) penetrates the interior of a cyclic molecule (ring molecule), with both ends of the axial molecule further attached with compounds (stoppers) larger than the inner diameter of the cyclic molecule. In this state, the cyclic molecule is confined on the axial molecule by the two stoppers, allowing the axial molecule and cyclic molecule to exist in a stable state in which they cannot dissociate. When a large number of cyclic molecules are incorporated, they are called polyrotaxanes. These cyclic molecules are bonded to each other by intermolecular bonding, resulting in a flexible and tough network polymer material in which the cyclic molecules move along the axial molecule. Such materials can distribute external stress uniformly throughout the material, resulting in higher deformation strength and durability compared to conventional chemically crosslinked network polymers, and some have already been commercialized.

[0003] Another unique type of rotaxane is the interdigitated rotaxane ([c2]daisy-chain rotaxane). Interdigitated rotaxanes are host-guest integrated compounds (HG compounds) in which a cyclic molecule (hereinafter also referred to as the "host") and an axial molecule (hereinafter also referred to as the "guest") are fused into a single molecule. The two molecules interdigitate with each other through intermolecular interactions, forming a host-guest structure. By introducing stoppers to the ends of each axial end, interdigitated rotaxanes form stable clathrate structures, forming topological molecules in which the distance between the two cyclic molecules is continuously variable. Because interdigitated rotaxanes reversibly dissociate upon application of external stimuli such as heat or light, research is currently underway aimed at their application to new materials. Patent Document 1 discloses the polymerization (Huisgen cycloaddition) of interdigitated rotaxane monomers using a copper catalyst as a metal catalyst.

[0004] Rotaxane polymers obtained by sequentially linking rotaxanes are classified into interlocked types (interlock compounds) and interdigitated types. Polymeric materials that enable contractile movement are being developed using interdigitated rotaxane polymers. By applying a stimulus to the polymerized interdigitated rotaxane, it is possible to cause the entire molecule to contract like muscle fibers, and applications such as artificial muscles are expected. Patent Document 2 discloses a crosslinked polymer composition obtained by crosslinking a polyrotaxane in which cyclic molecules have hydrosilyl groups with a polymer having double bonds using a platinum catalyst.

[0005] Non-Patent Documents 1 and 2 disclose the synthesis of an interdigitating rotaxane polymer using a 24-membered crown ether as a cyclic molecule and a copper catalyst, but do not describe properties such as compression resistance of the resulting rotaxane polymer. Non-Patent Document 3 discloses the synthesis of an interdigitating rotaxane monomer using a 24-membered crown ether as a cyclic molecule and a copper catalyst, which is synthesized using a ruthenium catalyst, but the resulting rotaxane polymer is not a film, and there is no description of properties such as compression resistance.

[0006] The present inventors synthesized linear or network polymers by reacting a stopper-free intercalating rotaxane ([c2]daisy-chain rotaxane) with a crosslinker having a terminal thiol group. The resulting polymers were able to form stable inclusion structures in which the inclusion units did not collapse without the need for the introduction of bulky stoppers, enabling the one-step synthesis of functional polymers using HG compounds. Additionally, the inventors discovered that introducing a rotaxane structure into a polymer material can impart excellent compression resistance and stress relaxation, and filed a patent application (Japanese Patent Application No. 2022-188248). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-121933 [Patent Document 2] Patent Publication No. 2021-127362 [Non-patent literature]

[0008] [Non-Patent Document 1] Bistable [c2]Daisy Chain Rotaxanes as Reversible Muscle-like Actuators in Mechanically Active Gels, J. AM. Chem. Soc., 139, 14825-14828 (2017) [Non-patent document 2] Muscle-like Supramolecular Polymer: Integrated motion from Thousands of Molecular Machines, Angew. Chem. Int. Ed., 51, 12504-12508 (2012) [Non-patent document 3] Switching and Extension of a [c2]daisy-chain Dimer Polymer, J. AM. Chem. Soc., 131, 13631-13633 (2009) Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, linear and network polymers of interdigitated rotaxane ([c2]daisy-chain rotaxane) polymers have been produced, and they have been shown to have excellent compression resistance and stress relaxation. To synthesize interdigitated rotaxanes without stoppers, it was necessary to design and synthesize a host-guest integrated compound (HG compound) consisting of a cyclic molecule (host) and an axial molecule (guest) linked in a 1:1 ratio as the smallest unit compound. However, as shown in the example synthesis scheme of an HG compound below, selectively introducing an axial molecule (guest) into only one of the cyclic molecules (host) requires the synthesis of the crown ether ring that serves as the cyclic molecule (host) from the starting compound. This process requires many steps, making it difficult to obtain a variety of interdigitated rotaxanes by simply synthesizing a variety of HG compounds. Therefore, there was a need to improve the reaction steps and yields in the synthetic route of the compound that serves as the smallest unit of interdigitated rotaxanes and easily obtain a variety of interdigitated rotaxanes. [ka] The object of the present invention is to provide a crown ether derivative having two ammonium salts that can be easily synthesized, a synthesis method thereof, and an interdigitated rotaxane ([c2]daisy-chain rotaxane), which can be used for interdigitated rotaxane polymers that can be used for a variety of purposes such as compression-resistant materials. [Means for solving the problem]

[0010] As a result of extensive research aimed at solving the above problems, the present inventors discovered that GHG compounds in which axial molecules (guests) are introduced on both sides of a cyclic molecule (host) can be easily synthesized and that the GHG compounds form GHG-type interdigitated rotaxanes, leading to the present invention.

[0011] That is, the present invention relates to a crown ether derivative having two ammonium salts, a method for synthesizing the same, and an interdigitated rotaxane, which are specified by the following features: [1] A crown ether derivative having two ammonium salts represented by the following chemical formula (1). [ka] [2] A method for synthesizing a crown ether derivative having two ammonium salts according to [1], characterized in that a dibenzocrown ether compound is formylated, the formylated dibenzocrown ether compound is reacted with an alkylamine, and then hydrogenated by reacting with a reducing agent, and then acidified and treated with a hexafluorophosphate solution. [3] An interdigitating rotaxane represented by the following chemical formula (2), which contains a crown ether derivative having two ammonium salts as described in [1]. [ka] [Effects of the Invention]

[0012] According to the present invention, a crown ether derivative having two ammonium salts as a GHG compound can be easily synthesized, and therefore, various GHG-type interdigitated rotaxanes containing a crown ether derivative having two ammonium salts can be easily formed, and the interdigitated rotaxane polymers can be applied to a variety of potential applications, such as compression-resistant materials. [Brief explanation of the drawings]

[0013] [Figure 1]shows the chemical structure of the compound DFB24C8 and its 1H NMR spectrum. [Figure 2] shows the chemical structure of compound BIB24C8 and its 1H NMR spectrum. [Figure 3] shows the chemical structure of compound BAB24C8 and its 1H NMR spectrum. [Figure 4] shows the chemical structure of the compound GHG_2PF6 and its 1H NMR spectrum. [Figure 5] shows the chemical structure of an interdigitated rotaxane containing the compound GHG_2PF6 and its 1H NMR spectrum. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention provides a crown ether derivative having two ammonium salts as a GHG compound, a symmetrical molecule that is easy to synthesize, instead of the HG compound, an asymmetrical molecule that has been commonly used as the minimum unit of an interdigitated rotaxane ([c2]daisy-chain rotaxane), and a method for synthesizing the same. Furthermore, the present invention provides a GHG-type interdigitated rotaxane containing a crown ether derivative having two ammonium salts.

[0015] [Crown ether derivatives with two ammonium salts] The HG compound, which is an asymmetric molecule that has been generally used as the minimum unit of an intercalating rotaxane, is, for example, a compound represented by the following chemical formula (3). [ka] Since such HG compounds are asymmetric molecules, it is necessary to introduce an axial molecule (guest) to only one side of a cyclic molecule (host). However, there is no simple molecular design method for introducing an axial molecule (guest) to only one side of a cyclic molecule (host). As shown in the synthesis method of [Chemical Formula 1] above, it is necessary to synthesize crown ethers from raw materials, which requires complicated reaction steps and results in low yields.

[0016] On the other hand, the crown ether derivative having two ammonium salts of the present invention is a symmetrical molecule, and the crown ether derivative represented by the following chemical formula (1) uses a 24-membered crown ether as the cyclic molecular (host) component and hexylamine as the axial molecular (guest) component. The crown ether, which is the cyclic molecular (host) component used in the crown ether derivative of the present invention, is a crown ether having 24 ring members, but the number of ring members of the crown ether is not limited to 24; crown ethers having 21 to 31 ring members can be used, with 21-, 24-, or 30-membered crown ethers being preferred, and 24-membered crown ethers being more preferred. Furthermore, the alkylamine, which is the axial molecular (guest) component, is hexylamine, but is not limited to hexylamine. The length of the alkylamine's carbon chain is not limited; it can be a carbon chain having 5 to 30 carbon atoms, and the carbon chain may contain a group containing atoms other than carbon atoms, such as ether, ester, amide, or thioether. [ka]

[0017] [Synthesis of crown ether derivatives having two ammonium salts] The crown ether derivative having two ammonium salts of the present invention is a symmetric molecule, so there is no need to synthesize a (dibenzo)crown ether as a cyclic molecule (host) from a raw material compound. The (dibenzo)crown ether can be used directly as a starting material, and can be easily synthesized as shown in the following synthesis method. [ka]

[0018] As described above, the method for synthesizing the crown ether derivative having two ammonium salts of the present invention is as follows: the dibenzocrown ether compound is reacted with hexamethylenetetramine (HMT) in trifluoroacetic acid (TFA) to formylate the dibenzocrown ether compound; the formylated dibenzocrown ether compound is reacted with an alkylamine in a 1:2 ratio; the resulting intermediate (referred to as BIB24C8 in the above synthesis method) is hydrogenated by reacting it with a reducing agent (sodium borohydride was used in the above synthesis method); the resulting mixture is then acidified and treated with a hexafluorophosphate solution (saturated potassium hexafluorophosphate solution was used in the above synthesis method).

[0019] The number of ring members of the crown ether used in the crown ether derivative having two ammonium salts of the present invention is not limited to 24, and the length of the carbon chain of the alkylamine axial molecule is not limited. Furthermore, as described above, the carbon chain may contain a group containing atoms other than carbon atoms, such as ether, ester, amide, or thioether. Therefore, the synthesis method represented by [Chemical Formula 6] can be appropriately modified depending on the form of the cyclic molecule and the axial molecule.

[0020] The reducing agent used in the method for synthesizing a crown ether derivative having two ammonium salts of the present invention is not limited to sodium borohydride used in [Chemical Formula 6], but may also be lithium aluminum hydride, diisobutylaluminum hydride, sodium cyanoborohydride, lithium borohydride, lithium triethylborohydride, borane complexes (borane-dimethylsulfide, borane-tetrahydrofuran, etc.), triethylsilane, sodium bis(2-methoxyethoxy)aluminum hydride, nickel borohydride, sodium triacetoxyborohydride, zinc borohydride, lithium tri(sec-butyl)borohydride, potassium tri(sec-butyl)borohydride, tributyltin hydride, etc.

[0021] In the method for synthesizing a crown ether derivative having two ammonium salts of the present invention, hydrochloric acid is used in [Chemical Formula 6] as a means for acidifying after hydrogenation. However, there are no particular limitations as long as it is capable of acidifying, and examples thereof include hydrogen halides such as hydrogen bromide (hydrobromic acid) and hydrogen iodide (hydriodic acid); halogen oxoacids such as hypochlorous acid, chlorous acid, chloric acid, perchloric acid, hypobromous acid, bromous acid, bromic acid, perbromic acid, hypoiodous acid, iodic acid, and periodic acid; sulfuric acid; nitric acid; phosphoric acid; boric acid; sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, polystyrenesulfonic acid, and vinylsulfonic acid; and carboxylic acids such as acetic acid, citric acid, formic acid, oxalic acid, lactic acid, tartaric acid, maleic acid, succinic acid, and malonic acid.

[0022] The hexafluorophosphate solution used in the method for synthesizing the crown ether derivative having two ammonium salts of the present invention is not limited to the saturated potassium hexafluorophosphate used in [Chemical Formula 6], but may also be tetraethylphosphonium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, bromotripyrrolidinophosphonium hexafluorophosphate, O-(benzotriazol-1-yl)-N,N,N',N'-bis(pentamethylene)uronium hexafluorophosphate, O-(benzotriazol-1-yl)-N,N,N',N'-bis(tetramethylene)uronium hexafluorophosphate, bromotris(dimethylamino)phosphate, phosphonium hexafluorophosphate, 1-benzyl-3-methylimidazolium hexafluorophosphate, 1-butyl-1-methylpyrrolidinium hexafluorophosphate, 2-chloro-1,3-dimethylimidazolinium hexafluorophosphate, chloro-N,N,N',N'-tetramethylformamidinium hexafluorophosphate, O-(6-chlorobenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, chlorotripyrrolidinophosphonium hexafluorophosphate, 1-ethyl-3-methylimidazolium hexafluorophosphate, O-[(ethoxycarbonyl)cyanomethyleneamino]-N,N,N',N'-Tetramethyluronium hexafluorophosphate, hexadecyltrimethylammonium hexafluorophosphate, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-hexylpyridinium hexafluorophosphate, 1-methyl-3-n-octylimidazolium hexafluorophosphate, methylammonium hexafluorophosphate, 1-methylpyridinium hexafluorophosphate, 1-methyl-1H-imidazol-3-ium hexafluorophosphate, sodium hexafluorophosphate, ammonium hexafluorophosphate, hexafluorophosphate Examples of the hexafluorophosphate include lithium phosphate, silver hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetrabutylphosphonium hexafluorophosphate, tetraethylammonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, 1-butyl-4-methylpyridinium hexafluorophosphate, diphenyliodonium hexafluorophosphate, tetrakis(acetonitrile)copper(I) hexafluorophosphate, 5-azoniaspiro[4.4]nonane hexafluorophosphate, and tetramethylammonium hexafluorophosphate.

[0023] [Intercalated rotaxane ([c2]daisy-chain rotaxane)] The interdigitated rotaxane of the present invention containing a crown ether derivative having two ammonium salts can be obtained by dissolving the crown ether derivative having two ammonium salts, which is a GHG compound represented by the above chemical formula (1), in an organic solvent. Synthesis of the interdigitated rotaxane of the present invention (chemical formula (2) below) and a GHG compound (chemical formula (1) below) in an organic solvent (acetonitrile was used in the synthesis method below) is shown in [Chemical Formula 7]. In the interdigitated rotaxane of the present invention, the number of ring members of each crown ether derivative constituting the interdigitated rotaxane and the number of carbon atoms of the axial molecule may differ. However, for reasons of synthetic efficiency and the like, it is preferable that the number of ring members of the crown ethers is the same, and it is also preferable that the number of carbon atoms of the axial molecule is the same. [ka]

[0024] The interdigitated rotaxane containing the crown ether derivative having two ammonium salts of the present invention was synthesized in acetonitrile in [Chemical Formula 7], but the organic solvent is not limited to acetonitrile, and examples thereof include dioxane, benzene, toluene, chloroform, chlorobenzene, dichloromethane, 1,2-dichloroethane, acetone, nitromethane, sulfolane, 3-methylsulfolane, etc. From the viewpoint of synthesis, solvents that are difficult to volatilize are preferred, and solvents with a boiling point of 60°C or higher are particularly preferred. [Example]

[0025] EXAMPLES Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

[0026] [Synthesis of crown ether derivatives bearing two ammonium salts] The crown ether derivative having two ammonium salts of the present invention was synthesized by the following method. The reaction steps are explained below in order. [ka]

[0027] Dibenzo-24-crown-8 (2.53 g, 5.64 mmol), trifluoroacetic acid (50 mL), and hexamethylenetetramine (4.69 g, 33.5 mmol) were placed in a 500 mL recovery flask and refluxed at 60°C for 20 hours. The mixture was then added to water (30 mL) and stirred for 1.5 hours. The reaction mixture was extracted with dichloromethane (CHCl) and washed three times with water. The organic layer was dried over anhydrous magnesium sulfate (MgSO), and the filtrate was concentrated. After concentration, the mixture was purified by filtration to obtain the desired compound DFB24C8 as a brown solid (yield: 2.63 g, 92.4%). The synthesis of compound DFB24C8 was confirmed as follows. 1 H NMR (CDCl3) δ (ppm from TMS): 9.82-9.80 (s, 2H, Ph-OC H ), 7.43-7.40 (d, 2H, Ph ), 7.38-7.36 (s, 2H, Ph), 6.93-6.90 (d, 2H, Ph), 4.23-3.84 (m, 24H, -C H 2C H 2 - O-). The chemical structure of compound DFB24C8 and its 1 The H NMR spectrum is shown in Figure 1.

[0028] DFB24C8 (2.63 g, 5.21 mmol) and hexylamine (1.33 g, 13.1 mmol) were dissolved in methanol (220 mL) and heated at 60 °C for 4 hours to obtain the desired compound BIB24C8 as a brown solid (yield 3.22 g, 92.0%). The synthesis of compound BIB24C8 was confirmed as follows. 1 H NMR (CDCl3) δ (ppm from TMS): 8.11-8.09 (s, 2H, Ph-C H=N), 7.36-7.32 (s, 2H, Ph), 7.12-7.08 (s, 2H, Ph), 6.84-6.80 (d, 2H, Ph), 4.28-3.71 (m, 24H, -C H 2C H 2 - O-), 3.59-3.50 (m, 4H, CH=NC H 2-), 1.70-1.17 (m, 20H, CH3-(C H 2)4-), 0.93-0.81 (t, 6H, C H 3-(CH2)4-). The chemical structure of compound BIB24C8 and its 1 The H NMR spectrum is shown in Figure 2.

[0029] BIB24C8 (3.22 g, 4.80 mmol) and sodium borohydride (NaBH4 (0.380 g, 10.0 mmol)) were dissolved in methanol (70 mL) and stirred in an ice bath. The mixture was then heated in an oil bath at 60°C for 4 hours, extracted with dichloromethane (CHCl2), washed with H2O, and filtered. The target compound BAB24C8 was obtained as a brown viscous liquid (yield 2.98 g, 92.0%). The synthesis of compound BAB24C8 was confirmed as follows. 1 H NMR (CDCl3) δ (ppm from TMS): 6.87-6.77 (m, 6H, Ph), 4.20-4.76 (m, 24H, -C H 2C H 2 - O-), 3.71-3.66 (s, 4H, Ph-C H 2-NH-), 2.62-2.55 (t, 4H, -NH-C H 2-), 1.54-1.21 (m, 20H, CH3-(C H 2)4-), 0.94-0.82 (t, 6H, C H 3-(CH2)4-). The chemical structure of compound BAB24C8 and its 1The H NMR spectrum is shown in Figure 3.

[0030] BAB24C8 (2.89 g, 4.28 mmol) was dissolved in methanol (80 mL), and 1N hydrochloric acid (HCl) was added until the pH became ≦2, followed by stirring at room temperature for 1 hour. Next, potassium hexafluorophosphate (KPF 6- (1.99 g, 10.7 mmol)) was added and stirred at room temperature for 1 hour. The mixture was extracted with dichloromethane (CHCl), washed with H0, and filtered. The mixture was then purified by recrystallization from acetonitrile (CHCN) and a larger amount of diethyl ether, yielding the desired GHG_2PF6 as a brown solid (yield 3.30 g, 79.7%). The synthesis of compound GHG_2PF6 was confirmed as follows. 1 H NMR (DMSO-d6) δ (ppm from TMS): 7.12-6.96 (m, 6H, Ph), 4.16-3.60 (m, 24H, -C H 2C H 2 - O-), 4.08-4.03 (s, 4H, -Ph-C H 2-NH2 + -), 2.91-2.84 (t, -Ph-CH2-NH2 + -C H 2-), 1.63-1.53 ​​(t, 4H, CH3-(CH2)3-C H 2-), 1.35-1.22 (m, 12H, CH3-(C H 2)3-), 0.94-0.86 (t, 6H, C H 3-). The chemical structure of the compound GHG_2PF6 and its properties in DMSO-d6 1 The H NMR spectrum is shown in Figure 4.

[0031] [Synthesis of Interdigitated Rotaxanes Containing Crown Ether Derivatives with Two Ammonium Salts] The obtained compound GHG_2PF6 was dissolved in acetonitrile as a GHG compound to obtain the interdigitated rotaxane ([c2]daisy chain rotaxane) shown in the above chemical formula (2). The chemical structure of the interdigitated rotaxane containing the obtained compound GHG_2PF6 and its structure in CD3CN are shown below. 1 The H NMR spectrum is shown in Figure 5. [Industrial Applicability]

[0032] The simple synthesis of an interdigitated rotaxane containing a crown ether derivative with two ammonium salts may enable the easy synthesis of a variety of interdigitated rotaxanes, and the use of the two ammonium salts in the crown ether derivative is expected to lead to applications in a variety of polymers.

Claims

1. A crown ether derivative having two ammonium salts represented by the following chemical formula (1). 【Chemistry 1】

2. 2. The method for synthesizing the crown ether derivative having two ammonium salts according to claim 1, characterized in that the dibenzocrown ether compound is formylated, the formylated dibenzocrown ether compound is reacted with an alkylamine, and then hydrogenated by reacting with a reducing agent, and then acidified and treated with a hexafluorophosphate solution.

3. 2. An interdigitating rotaxane represented by the following chemical formula (2), which comprises the crown ether derivative having two ammonium salts according to claim 1. 【Chemistry 2】

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