A method for synthesizing tetrapyridylcyclobutane

Abstract

A method for synthesizing a plurality of tetrapyridylcyclobutanes, the method relating to the synthesis of 1,2,3,4-(4-pyridyl)cyclobutane, 1,2,3,4-(3-pyridyl)cyclobutane and 1,2,3,4-(2-pyridyl)cyclobutane. The synthesis method described in the present application uses dipyridylethylene (such as 1,2-di(4-pyridyl)ethylene, 1,2-di(3-pyridyl)ethylene, 1,2-di(2-pyridyl)ethylene) as a raw material, and irradiates 1,2-di(4-pyridyl)ethylene, 1,2-di(3-pyridyl)ethylene, or a frozen solution of 1,2-di(2-pyridyl)ethylene solution with light, and separates and purifies the corresponding tetrapyridylcyclobutane (such as 1,2,3,4-(4-pyridyl)cyclobutane, 1,2,3,4-(3-pyridyl)cyclobutane, or 1,2,3,4-(2-pyridyl)cyclobutane). The method does not require the use of organic or metal eutectic molecules, does not require subsequent separation, does not require the use of other organic substances other than ethanol, is simple to operate, and is green and pollution-free.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis, and particularly relates to a method for synthesizing tetrapyridylcyclobutane. Background Art

[0002] As a tetradentate ligand, tetrapyridylcyclobutane has attracted extensive attention in the field of supramolecular assembly, such as metal-organic frameworks, coordination polymers, assembled nanoparticles, and metal-organic cages. In addition, due to the presence of conjugated electron-withdrawing pyridine rings, the complexes formed by tetrapyridylcyclobutane and metals can realize electron transfer between metals and ligands, thus exhibiting good electrical, optical, and magnetic properties.

[0003] At present, the synthesis method of tetrapyridine cyclobutane is mainly the eutectic method, that is, to find a suitable eutectic molecule to form a eutectic with dipyridylethylene, shorten the distance between the carbon-carbon double bonds of the dipyridylethylene, and then irradiate the dipyridylethylene with ultraviolet light to cause a [2+2] cycloaddition reaction. Leonard R. MacGillivray's research group reported a method for synthesizing 1,2,3,4-(4-pyridyl)cyclobutane, which forms a eutectic with 1,2-di(4-pyridyl)ethylene by using m-diphenol, and then irradiating the eutectic with ultraviolet light to induce a [2+2] cycloaddition reaction of 1,2-di(4-pyridyl)ethylene. Later, Leonard R. MacGillivray's research group reported the method of synthesizing 1,2,3,4-(3-pyridyl)cyclobutane and 1,2,3,4-(2-pyridyl)cyclobutane, respectively, by forming co-crystals with o-diphenol and 1,2-di(3-pyridyl)ethylene and 1,2-di(2-pyridyl)ethylene, and then ultraviolet light irradiation induced the [2+2] cycloaddition reaction of 1,2-di(3-pyridyl)ethylene and 1,2-di(2-pyridyl)ethylene (see J.Am.Chem.Soc.2000,122,7817-7818; Chem.Commun.2014,50,15960-15962; ChemPhysChem2020,21,154-163). The above co-crystal method has the following defects:

[0004] (1) The eutectic preparation process in the reported method requires the evaporation of a large amount of organic solvent.

[0005] (2) The reported methods do not contain a universal cocrystal molecule that can form cocrystals with a variety of dipyridylethylenes.

[0006] (3) In order to finally obtain tetrapyridylcyclobutane in the reported method, it is necessary to effectively separate the cocrystal molecules. Summary of the invention

[0007] In order to improve the above technical problems, the present invention provides a method for synthesizing tetrapyridylcyclobutane, comprising the following steps:

[0008] Dissolving dipyridylethylene in water and freezing it to form a solid frozen solution is followed by irradiation with light to obtain the tetrapyridylcyclobutane.

[0009] According to an embodiment of the present invention, the dipyridylethylene is selected from 1,2-di(4-pyridyl)ethylene, 1,2-di(3-pyridyl)ethylene and 1,2-di(2-pyridyl)ethylene;

[0010] According to an embodiment of the present invention, the concentration of the solution obtained after the dipyridylethylene is dissolved in water is 0.2mM-8mM, for example, 0.5mM-5mM, and exemplarily 2.5mM;

[0011] According to an embodiment of the present invention, the tetrapyridylcyclobutane is selected from 1,2,3,4-(4-pyridyl)cyclobutane, 1,2,3,4-(3-pyridyl)cyclobutane and 1,2,3,4-(2-pyridyl)cyclobutane;

[0012] According to an embodiment of the present invention, after the reaction of 1,2-di(4-pyridyl)ethylene is completed, 1,2,3,4-(4-pyridyl)cyclobutane is prepared; after the reaction of 1,2-di(3-pyridyl)ethylene is completed, 1,2,3,4-(3-pyridyl)cyclobutane is prepared; after the reaction of 1,2-di(2-pyridyl)ethylene is completed, 1,2,3,4-(2-pyridyl)cyclobutane is prepared.

[0013] According to an embodiment of the present invention, a solution formed by dissolving dipyridylethylene in water is placed at -10°C to -80°C to form a solid state, for example, at -20°C to -60°C, and exemplarily at -30°C to form a solid state;

[0014] According to an embodiment of the present invention, the temperature of the system during illumination is a temperature at which dipyridylethylene dissolves in water to form a solid state, for example, -10°C to -80°C, preferably -20°C to -60°C, and exemplarily -30°C.

[0015] According to an embodiment of the present invention, the wavelength of the light is 300nm to 1000nm, for example 365nm to 871nm;

[0016] According to an embodiment of the present invention, the illumination time is more than 0.5 h, such as 1-10 h, exemplified by 1.5 h, 8 h;

[0017] According to an embodiment of the present invention, the light source is a mercury lamp, such as a high-pressure mercury lamp.

[0018] According to an embodiment of the present invention, the synthesis method further includes: a separation and / or purification step after the illumination is completed; the separation step includes, after the illumination is completed, melting the solid frozen solution to obtain a liquid aqueous solution, removing the solvent water, and obtaining the tetrapyridylcyclobutane; the purification can be performed by recrystallizing the separated tetrapyridylcyclobutane through ethanol and water.

[0019] According to an exemplary embodiment of the present invention, the synthesis method comprises the following steps:

[0020] (1) Take 1,2-di(4-pyridyl)ethylene, or 1,2-di(3-pyridyl)ethylene, or 1,2-di(2-pyridyl)ethylene, add water and dissolve;

[0021] (2) placing the solution obtained in step (1) at a temperature of -10°C to -80°C to freeze it to form a solid frozen solution, and irradiating the solid solution placed at a temperature of -10°C to -80°C with a high-pressure mercury lamp with a wavelength range of 365nm to 871nm;

[0022] (3) placing the frozen solution after irradiation in step (2) at room temperature to melt to obtain a liquid aqueous solution, and removing the solvent water by reduced pressure evaporation to obtain a light yellow powder;

[0023] (4) Recrystallizing and purifying the solid powder obtained in step (3) with a mixed solution of ethanol and water to finally obtain transparent crystalline 1,2,3,4-(4-pyridyl)cyclobutane, 1,2,3,4-(3-pyridyl)cyclobutane, or 1,2,3,4-(2-pyridyl)cyclobutane.

[0024] According to an embodiment of the present invention, since dipyridylethylene has a low solubility in water, ultrasonic treatment for 0.5 h to 2 h, or heating at 60° C. to 80° C. may be used to accelerate dissolution when preparing the aqueous solution.

[0025] According to an embodiment of the present invention, the tetrapyridylcyclobutane is synthesized by a [2+2] cycloaddition reaction of dipyridylethylene molecules under light conditions.

[0026] The principle of the above-mentioned synthesis method of the present invention is that low-temperature freezing can make 1,2-di(4-pyridyl)ethylene, 1,2-di(3-pyridyl)ethylene, or 1,2-di(2-pyridyl)ethylene enriched between ice grain domains, promote the orderly arrangement of 1,2-di(4-pyridyl)ethylene, 1,2-di(3-pyridyl)ethylene, or 1,2-di(2-pyridyl)ethylene on the surface of ice crystals, and ensure the orderly arrangement of 1,2-di(4-pyridyl)ethylene, 1,2-di(3-pyridyl)ethylene, or 1,2-di(2-pyridyl)ethylene. , or the distance between the carbon-carbon double bonds of 1,2-di(2-pyridyl)ethylene molecules is in a suitable range, so as to achieve a [2+2] cycloaddition reaction of 1,2-di(4-pyridyl)ethylene, 1,2-di(3-pyridyl)ethylene, or 1,2-di(2-pyridyl)ethylene under light such as a high-pressure mercury lamp to obtain 1,2,3,4-(4-pyridyl)cyclobutane, 1,2,3,4-(3-pyridyl)cyclobutane, or 1,2,3,4-(2-pyridyl)cyclobutane.

[0027] Beneficial Effects

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The present invention does not involve the preparation of co-crystals, does not require the use of co-crystal molecules, does not require a large amount of organic solvents, and does not involve the separation of co-crystal molecules at a later stage.

[0030] 2. The solvent used in the present invention is water, which is green and environmentally friendly. The whole process does not require high temperature and high pressure treatment, and the operation is simple and safe.

[0031] 3. The present invention can be used to prepare a variety of tetrapyridylcyclobutanes, such as 1,2,3,4-(4-pyridyl)cyclobutane, 1,2,3,4-(3-pyridyl)cyclobutane and 1,2,3,4-(2-pyridyl)cyclobutane. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the NMR image of 1,2,3,4-(4-pyridyl)cyclobutane synthesized in Example 1;

[0033] Figure 2 is the NMR image of 1,2,3,4-(3-pyridyl)cyclobutane synthesized in Example 2;

[0034] Figure 3 is the NMR image of 1,2,3,4-(2-pyridyl)cyclobutane synthesized in Example 3;

[0035] Figure 4 This is a single crystal structure diagram of 1,2,3,4-(2-pyridyl)cyclobutane synthesized in Example 3. DETAILED DESCRIPTION

[0036] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0037] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0038] The following is combined with Figures 1 to 4 The present invention is further described with examples:

[0039] Example 1

[0040] A simple and green method for synthesizing 1,2,3,4-(4-pyridyl)cyclobutane comprises the following steps:

[0041] (1) Weigh 36.4 mg (0.2 mmol) of 1,2-di(4-pyridyl)ethylene and add it to a 200 mL round-bottom flask. Add 80 mL of water to the round-bottom flask, heat and stir at 80°C to dissolve, and then leave to cool at room temperature.

[0042] (2) Take 10 mL of the solution prepared in step (1) and add it to a culture dish with a diameter of 10 mm. Place the culture dish at -30°C for 1 hour to allow the solution to freeze to form a solid frozen solution.

[0043] (3) The frozen solution in step (2) is placed in a -30°C reactor and irradiated with a high-pressure mercury lamp with a wavelength in the range of 365 nm to 871 nm for 8 h.

[0044] (4) Repeat steps (2) and (3) until the prepared 80 mL solution is used up.

[0045] (5) The frozen solution after illumination was placed at room temperature to melt, and the solution was collected in a 150 mL round-bottom flask. The solvent water was removed using a rotary evaporator to obtain a light yellow powder.

[0046] (6) The light yellow powder was dissolved by heating a mixed solution of 2 mL of ethanol and water (volume ratio 1:1), and the mixture was allowed to stand at room temperature for 12 h. Transparent 1,2,3,4-(4-pyridyl)cyclobutane crystals were precipitated by recrystallization (yield 87%, purity characterized by NMR>90%).

[0047] Figure 1 This is the NMR spectrum of 1,2,3,4-(4-pyridyl)cyclobutane synthesized in this example.

[0048] 1H NMR (400MHz, CDCl3, TMS) δ = 4.47 (s, 4H), 6.68-6.69 (d, 8H), 8.42-8.44 (d, 8H).

[0049] Example 2

[0050] A simple and green method for synthesizing 1,2,3,4-(3-pyridyl)cyclobutane comprises the following steps:

[0051] (1) Weigh 36.4 mg (0.2 mmol) of 1,2-di(3-pyridyl)ethylene and add it to a 200 mL round-bottom flask. Add 80 mL of water to the round-bottom flask, heat and stir at 80°C to dissolve, and then leave to cool at room temperature.

[0052] (2) Take 10 mL of the solution prepared in step (1) and add it to a culture dish with a diameter of 10 mm. Place the culture dish at -30°C for 1 hour to allow the solution to freeze to form a solid frozen solution.

[0053] (3) The frozen solution in step (2) was placed in a -30°C reactor and irradiated with a high-pressure mercury lamp with a wavelength in the range of 365 nm to 871 nm for 1.5 h.

[0054] (4) Repeat steps (2) and (3) until the prepared 80 mL solution is used up.

[0055] (5) The frozen solution after illumination was placed at room temperature to melt, and the solution was collected in a 150 mL round-bottom flask. The solvent water was removed using a rotary evaporator to obtain a light yellow powder.

[0056] (6) The light yellow powder was dissolved by heating a mixed solution of 2 mL of ethanol and water (volume ratio 1:1), and the mixture was allowed to stand at room temperature for 12 h. Transparent 1,2,3,4-(3-pyridyl)cyclobutane crystals were precipitated by recrystallization (yield 90%, purity characterized by NMR>90%).

[0057] Figure 2 This is the NMR spectrum of 1,2,3,4-(3-pyridyl)cyclobutane synthesized in this example.

[0058] 1 H NMR (400MHz, CDCl3, TMS) δ = 4.55 (s, 4H), 7.1-7.13 (m, 4H), 7.37-7.4 (m, 4H), 8.37-8.42 (m, 8H).

[0059] Example 3

[0060] A simple and green method for synthesizing 1,2,3,4-(2-pyridyl)cyclobutane comprises the following steps:

[0061] (1) Weigh 36.4 mg (0.2 mmol) of 1,2-di(2-pyridyl)ethylene and add it to a 200 mL round-bottom flask. Add 80 mL of water to the round-bottom flask, heat and stir at 80°C to dissolve, and then leave to cool at room temperature.

[0062] (2) Take 10 mL of the solution prepared in step (1) and add it to a culture dish with a diameter of 10 mm. Place the culture dish at -30°C for 1 hour to allow the solution to freeze to form a solid frozen solution.

[0063] (3) The frozen solution in step (2) was placed in a -30°C reactor and irradiated with a high-pressure mercury lamp with a wavelength in the range of 365 nm to 871 nm for 1.5 h.

[0064] (4) Repeat steps (2) and (3) until the prepared 80 mL solution is used up.

[0065] (5) The frozen solution after illumination was placed at room temperature to melt, and the solution was collected in a 150 mL round-bottom flask. The solvent water was removed using a rotary evaporator to obtain a light yellow powder.

[0066] (6) The light yellow powder was dissolved by heating a mixed solution of 2 mL of ethanol and water (volume ratio 1:1), and the mixture was allowed to stand at room temperature for 12 h. Transparent 1,2,3,4-(4-pyridyl)cyclobutane crystals were precipitated by recrystallization (yield 85%, purity characterized by NMR>90%).

[0067] Figure 3 This is the NMR spectrum of 1,2,3,4-(2-pyridyl)cyclobutane synthesized in this example.

[0068] 1 H NMR (400MHz, CDCl3, TMS) δ = 5.06 (s, 4H), 6.89-6.93 (m, 4H), 7.05-7.07 (d, 4H), 7.34-7.38 (m, 4H), 8.39-8.4 (d, 4H).

[0069] Figure 4 This is a single crystal structure diagram of 1,2,3,4-(2-pyridyl)cyclobutane synthesized in this example.

[0070] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for synthesizing tetrapyridylcyclobutane, characterized in that: The following steps are involved: Dissolving dipyridylethylene in water, freezing it to form a solid frozen solution, and irradiating it with light to obtain the tetrapyridylcyclobutane; The dipyridylethylene is selected from 1,2-di(4-pyridyl)ethylene, 1,2-di(3-pyridyl)ethylene and 1,2-di(2-pyridyl)ethylene; The wavelength of the light is 365nm~871nm.

2. The synthesis method according to claim 1, characterized in that The concentration of the solution obtained after the dipyridylethylene is dissolved in water is 0.2mM-8mM.

3. The synthesis method according to claim 1, characterized in that The concentration of the solution obtained after the dipyridylethylene is dissolved in water is 0.5mM-5mM.

4. The synthesis method according to claim 1, characterized in that The tetrapyridylcyclobutane is selected from 1,2,3,4-(4-pyridyl)cyclobutane, 1,2,3,4-(3-pyridyl)cyclobutane and 1,2,3,4-(2-pyridyl)cyclobutane; After the reaction of 1,2-di(4-pyridyl)ethylene is completed, 1,2,3,4-(4-pyridyl)cyclobutane is prepared; after the reaction of 1,2-di(3-pyridyl)ethylene is completed, 1,2,3,4-(3-pyridyl)cyclobutane is prepared; after the reaction of 1,2-di(2-pyridyl)ethylene is completed, 1,2,3,4-(2-pyridyl)cyclobutane is prepared.

5. The synthesis method according to claim 1, characterized in that The solution formed by dissolving dipyridylethylene in water is placed at -10°C to -80°C to form a solid state.

6. The synthesis method according to claim 1, characterized in that The temperature of the system during the irradiation with light is a temperature at which dipyridylethylene dissolves in water and forms a solid state.

7. The synthesis method according to claim 6, characterized in that The temperature is -10°C to -80°C.

8. The synthesis method according to claim 6, characterized in that The temperature is -20°C to -60°C.

9. The synthesis method according to claim 1, characterized in that The light source is a mercury lamp.

10. The synthesis method according to claim 1, characterized in that The light source is a high pressure mercury lamp.

11. The synthesis method according to claim 1, characterized in that The illumination time is more than 0.5 h.

12. The synthesis method according to claim 1, characterized in that: The illumination time is 1-10h.

13. The synthesis method according to claim 1, characterized in that: The synthesis method also includes: a separation and / or purification step after the illumination ends; the separation step includes, after the illumination ends, melting the solid frozen solution to obtain a liquid aqueous solution, removing the solvent water, and obtaining the tetrapyridylcyclobutane; the purification step is to recrystallize the separated tetrapyridylcyclobutane through ethanol and water.

14. The synthesis method according to claim 1, characterized in that The synthesis method comprises the following steps: (1) Take 1,2-di(4-pyridyl)ethylene, or 1,2-di(3-pyridyl)ethylene, or 1,2-di(2-pyridyl)ethylene, add water and dissolve; (2) placing the solution obtained in step (1) at a temperature of -10°C to -80°C to freeze it to form a solid frozen solution, and irradiating the solid solution placed at a temperature of -10°C to -80°C with a high-pressure mercury lamp with a wavelength range of 365nm to 871nm; (3) leaving the frozen solution after irradiation in step (2) at room temperature to melt to obtain a liquid aqueous solution, and removing the solvent water by reduced pressure evaporation to obtain a light yellow powder; (4) Recrystallizing and purifying the solid powder obtained in step (3) with a mixed solution of ethanol and water to finally obtain transparent crystalline 1,2,3,4-(4-pyridyl)cyclobutane, 1,2,3,4-(3-pyridyl)cyclobutane, or 1,2,3,4-(2-pyridyl)cyclobutane.

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