A compound based on a bisfuranobenzothiadiazole skeleton and a preparation method thereof

Abstract

The present application relates to a kind of based on double furan benzothiadiazole skeleton compound and its preparation method, on the basis of double thiophene benzothiadiazole structural unit, by introducing two furan ring (containing oxygen five-membered heterocyclic ring) form based on double furan benzothiadiazole skeleton compound, introduce double furan ring, the electronic properties of the electronic properties of originally benzothiadiazole unit is adjusted, effectively reduce the overall band gap of molecule, cause its optical absorption and emission spectrum to occur significant blue shift, make it become the ideal candidate of the design specific wavelength luminescent material or narrow band gap semiconductor.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, and in particular relates to a compound based on the bisfuranobenzothiadiazole skeleton and its preparation method. Background Technology

[0002] Difuranobenzothiadiazole (BDFTD) structural units, as strongly electron-deficient large conjugated systems, have shown great application potential in the field of organic optoelectronic materials. Due to their high planarity, good crystallinity, and low molecular orbital energy levels, this type of framework is often used to construct high-performance organic solar cell donor or acceptor materials. Previous studies have faced challenges in synthesizing such large fused-ring frameworks, including cumbersome procedures, harsh reaction conditions, and low overall yields. In particular, effective ring fusion between the furan ring and the benzothiadiazole central core often relies on highly toxic reagents or difficult-to-control catalytic processes, which not only increases synthesis costs but also limits the functionalization modification of molecular side chains and the regulation of solubility.

[0003] Therefore, developing a bisfuranobenzothiadiazole compound that is easy to synthesize, has mild conditions, and is easy to prepare on a large scale is of great scientific value and application significance for promoting the research of next-generation high-efficiency organic optoelectronic materials. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a compound based on a bisfuranobenzothiadiazole skeleton and its preparation method.

[0005] The technical solution adopted in this invention is: a compound based on the bisfuranobenzothiadiazole skeleton, the structure of which is shown in Formula 7;

[0006] Formula 7;

[0007] R1 is hydrogen or halogen.

[0008] Preferably, R1 is F, Cl, Br or I.

[0009] A method for preparing compounds based on the bisfuranobenzothiadiazole skeleton is described below:

[0010]

[0011] Among them, the compounds of formula 6 or formula 7 are compounds based on the bisfuranobenzothiadiazole skeleton.

[0012] Preferably, the specific steps are as follows:

[0013] Step 1: Add the compound shown in Formula 1 to a first anhydrous organic solvent containing organolithium, react at -70~-78℃, then add lithium bromide and cuprous bromide, stir and react; then add oxalyl chloride and stir and react; to prepare the compound of Formula 2;

[0014] Step 2: Add the compound of formula 2, the oxidant and the activating substance to the second anhydrous organic solvent, and stir the reaction at 0°C to obtain the compound of formula 3;

[0015] Step 3: Add a reducing agent and a third anhydrous solvent to a container containing compound of formula 3, heat the mixture at 70-85°C to obtain compound of formula 4, then add a catalyst and a reducing agent, and react at 65-85°C to obtain compound of formula 5; add compound of formula 5 and a halogen-containing inorganic compound to a fourth solvent to react and obtain compound of formula 6.

[0016] Preferably, it also includes,

[0017] Step 4: Add the fifth solvent and halogen source to the container containing compound 6, and stir the reaction at 60~80℃ to obtain compound 7.

[0018] Preferably, in step one, the first anhydrous organic solvent is ultra-dry tetrahydrofuran, the organolithium is n-butyllithium, the molar ratio of the compound of formula 1 to lithium bromide is 1.0:1.0~1.2, the molar ratio of lithium bromide to cuprous bromide is 1.0:1.0~1.2, and the molar ratio of organolithium to 3-bromofuran is 1-1.05.

[0019] Preferably, the oxidant and activator are ferric chloride and nitromethane, or molybdenum pentachloride and nitromethane, or vanadium trifluoride and boron trifluoride ether solution, or (bis(trifluoroacetoxy)iodo)benzene and boron trifluoride ether solution, or DDQ and trifluoromethanesulfonic acid; the second anhydrous organic solvent is ultra-dry dichloromethane; the molar ratio of 1,2-bis(furan-3-yl)ethane-1,2-dione to the oxidant and activator is 1.0:1~1.2:6~6.5.

[0020] Preferably, when preparing compound 4, the reducing agent is hydroxylamine hydrochloride, the third anhydrous organic solvent is anhydrous ethanol, and the molar ratio of compound 3 to the reducing agent is 1.0:2.5~3.0;

[0021] When preparing compound of formula 5, the catalyst is palladium on carbon, the reducing agent is hydrazine hydrate, and the molar ratio of compound of formula 4, catalyst and reducing agent is 1.0:0.8~1.2:30.0~50.0;

[0022] When preparing compound 6, the fourth solvent is dichloromethane / triethylamine or N,N-dimethylformamide, the halogenated inorganic compound is sulfoxide or disulfur dichloride, and the molar ratio of diamine compound to halogenated inorganic compound is 1:2.5~4.0.

[0023] Preferably, the halogen source is at least one of xenon difluoride, elemental bromine, elemental chlorine, and elemental iodine, and the fifth solvent is at least one of dichloromethane, chloroform, and tetrahydrofuran; the molar ratio of the compound of Formula 6 to the halogen source is 1:2.0~2.2.

[0024] Preferably, the synthesis process is carried out under a protective gas condition, wherein the protective gas is nitrogen.

[0025] The advantages and positive effects of this invention are: based on the bisfuranophenthiadiazole skeleton, furan is introduced into it, which modulates its electronic properties and solubility, making it an ideal choice for high-performance organic semiconductor materials and an ideal electron-deficient π building block for developing high-performance D–A conjugated polymer semiconductors;

[0026] Compounds based on the bisfuranophenthiadiazole skeleton were prepared using 3-bromofuran as the starting material. Through oxidation, reduction, nucleophilic substitution, and bromination reactions, compounds of formula 6 or 7 were synthesized for the first time. These compounds can be continuously modified through coupling reactions and free radical polymerization reactions, and their conjugated system can be expanded by connecting other conjugated structural units. Based on the spectral characteristics of the bisfuranophenthiadiazole skeleton, organic semiconductor materials can be designed and synthesized, showing potential applications in organic photovoltaics, detectors, and near-infrared dyes. These compounds have a wide range of applicable substrates and high skeleton scalability. Detailed Implementation

[0027] The embodiments of the present invention will be described below.

[0028] This invention relates to a compound based on a bis-furanobenzothiadiazole skeleton and its preparation method. Based on the "benzothiadiazole" structural unit, two furan rings (oxygen-containing five-membered heterocycles) are introduced to form a compound based on a bis-furanobenzothiadiazole skeleton. The introduction of the bis-furan rings modulates the electronic properties of the original benzothiadiazole unit, effectively reducing the overall band gap of the molecule, resulting in a significant blue shift in its optical absorption and emission spectra. This characteristic makes it an ideal candidate for designing specific wavelength luminescent materials or narrow bandgap semiconductors.

[0029] The structures of compounds based on the bisfuranobenzothiadiazole skeleton are shown in Formula 7;

[0030] Formula 7;

[0031] R1 is hydrogen or a halogen; specifically, it can be hydrogen, F, Cl, Br, or I.

[0032] In compounds based on the bisfuran-benzothiadiazole skeleton, furan, as an electron-rich aromatic ring, allows for precise modulation of the entire molecule's electronic structure within a conjugated system. When furan is connected to an electron-deficient benzothiadiazole unit through a conjugated system, a donor-acceptor (DA) structure is formed. This DA structure effectively reduces the overall band gap of the molecule, resulting in a blue shift in the absorption and emission spectra. This means the material can absorb and emit light at shorter wavelengths, which is crucial for designing luminescent materials of specific colors or narrow-bandgap semiconductors.

[0033] The reaction process of the compound shown in Formula 7 is as follows:

[0034]

[0035] Starting with 3-bromofuran, compounds based on the bisfuranobenzothiadiazole skeleton were prepared through oxidation, reduction, nucleophilic substitution, and bromination reactions. The specific preparation process is as follows:

[0036] Step (1): Under a protective atmosphere, in a low-temperature reaction vessel, after adding the first anhydrous organic solvent and organolithium, 3-bromofuran (compound of formula 1) is slowly added and the reaction is stirred; wherein the first anhydrous organic solvent is ultra-dry tetrahydrofuran, the organolithium is n-butyllithium (n-BuLi), the molar volume ratio of 3-bromofuran to the first anhydrous organic solvent is 1 mmol: 1~1.5 mL, and the molar ratio of organolithium reagent to 3-bromofuran is 1-1.05:1.0; the reaction is carried out in an environment of -70~-78℃ for 2~3 hours;

[0037] Under a protective atmosphere, lithium bromide and cuprous bromide were added to a low-temperature reaction vessel, followed by the slow addition of the reaction solution from the previous step, and the reaction was stirred for 30 to 90 minutes. The molar ratio of 3-bromofuran to lithium bromide was 1.0:1.0 to 1.2, the molar ratio of lithium bromide to cuprous bromide was 1.0:1.0 to 1.2, and the molar volume ratio of lithium bromide to the first anhydrous organic solvent was 1 mmol: 2 to 5 mL.

[0038] Oxaloyl chloride dissolved in a first anhydrous organic solvent under low temperature conditions was slowly added. The molar ratio of 3-bromofuran to oxaloyl chloride was 1.0:0.5~0.55. The reaction was carried out at -70~-78℃ for 2~3 hours. After returning to room temperature, the reaction was stirred for 6~12 hours. The post-treatment yielded 1,2-bis(furan-3-yl)ethane-1,2-dione as shown in Formula 2.

[0039] Step (2): Under a protective atmosphere, in a low-temperature reaction vessel, add 1,2-bis(furan-3-yl)ethane-1,2-dione (as shown in Formula 2), a second anhydrous organic solvent, an oxidant, and an activating agent; cool the resulting mixture to 0°C, stir for 3-5 minutes, and after the reaction is complete, obtain bisfuranophenylenedione (as shown in Formula 3); wherein the oxidant and activating agent are ferric chloride and nitromethane, or molybdenum pentachloride and nitromethane, or vanadium trifluoride and boron trifluoride. The ether solution is either (bis(trifluoroacetoxy)iodide)benzene and boron trifluoride diethyl ether solution, or DDQ and trifluoromethanesulfonic acid; the second anhydrous organic solvent is ultra-dry dichloromethane; the molar ratio of 1,2-bis(furan-3-yl)ethane-1,2-dione to oxidant and activator is 1.0:1~1.2:6~6.5; the molar volume ratio of 1,2-bis(furan-3-yl)ethane-1,2-dione to the second anhydrous organic solvent is 1 mmol:55~60 mL.

[0040] Step (3): Under a protective atmosphere, a reducing agent is added to a reaction flask containing bis(furanophenyl)dione as shown in Formula 3, followed by the addition of a third anhydrous solvent to dissolve it. The mixture is heated and stirred at 70-85°C for 20-48 hours to obtain compound of Formula 4. The reducing agent is hydroxylamine hydrochloride, the third anhydrous organic solvent is anhydrous ethanol, the molar ratio of bis(furanophenyl)dione as shown in Formula 3 to the reducing agent is 1.0:2.5-3.0, and the molar volume ratio of bis(furanophenyl)dione to the third anhydrous organic solvent is 1 mmol:8-15 mL.

[0041] The catalyst was directly added to the reactor in the next step under purging conditions. After heating to 65°C, the reducing agent diluted with alcohol was slowly added over a period of 1-2 hours. After the addition was completed, the temperature was raised to 85°C and refluxed. After reacting for 16-48 hours, the mixture was moved to room temperature and post-treated to obtain the diamine compound shown in Formula 5. The catalyst was palladium on carbon added at a mass percentage of 10%, and the reducing agent was hydrazine hydrate. The molar ratio of the compound in Formula 4, the catalyst, and the reducing agent was 1.0:0.8-1.2:30.0-50.0.

[0042] A fourth solvent and a halogen-containing inorganic compound are added to a container containing a diamine compound of Formula 5, and the mixture is stirred and reacted. After post-treatment, a compound of bisfuranobenzothiadiazole of Formula 6 is obtained. The fourth solvent is a mixture of dichloromethane and triethylamine (triethylamine is four equivalents of the diamine compound, and the molar volume ratio of the diamine compound to the dichloromethane solvent is 1 mmol: 15-20 mL), or N,N-dimethylformamide. The halogen-containing inorganic compound is sulfoxide or disulfur dichloride, and the molar ratio of the diamine compound to the halogen-containing inorganic compound is 1:2.5-4.0. The molar volume ratio of the diamine compound of Formula 5 to the fourth solvent is 1 mmol: 5-10 mL. When the compound of Formula 5 reacts with sulfoxide and dichloromethane / triethylamine, the reaction temperature is 35-40 °C. When the compound of Formula 5 reacts with disulfur dichloride and N,N-dimethylformamide, the reaction temperature is 15-25 °C.

[0043] Nitrogen is used as the protective gas in the above reaction process.

[0044] The compound of formula 6 prepared by the above steps is a compound based on the bisfuranobenzothiadiazole skeleton. Further reaction of compound 6 with a halogen source yields compound 7, where R1 is a halogen. The specific steps are as follows:

[0045] Step (4): Add the fifth solvent and halogen source to the container containing the bisfuranobenzothiadiazole compound shown in Formula 6, stir and react at 60~80℃ for 4~8 hours, and then process to obtain the compound based on the bisfuranobenzothiadiazole skeleton shown in Formula 7; wherein, the halogen source is at least one of xenon difluoride, bromine, chlorine or iodine, and the fifth solvent is at least one of dichloromethane, chloroform or tetrahydrofuran; the molar ratio of the compound of Formula 6 to the halogen source is 1:2.0~2.2, and the molar volume ratio of the compound of Formula 6 to the fourth solvent is 1 mmol:5~10 mL.

[0046] Compounds of Formula 7 can serve as a skeletal structure and can be continuously modified through coupling reactions and / or free radical polymerization reactions. For example, their conjugated system can be expanded by connecting other conjugated structural units, such as by extending or modifying the R1 group position, to construct new compounds. Based on the spectral characteristics of the bis(furanobenzothiadiazole) skeleton, the constructed new compounds can be used in organic semiconductor materials, showing potential applications in organic photovoltaics, detectors, and near-infrared dyes. Compounds of Formula 7 have a wide substrate range, can be modified by various groups, and exhibit high skeletal expandability.

[0047] The present invention will now be described. Experimental methods that do not specify the operation steps are performed in accordance with the corresponding product manuals. Unless otherwise specified, the instruments, reagents and consumables used in the embodiments can be purchased from commercial companies.

[0048] Example 1

[0049] Formula 6;

[0050] The synthesis of the compound shown in Formula 6 includes the following steps:

[0051]

[0052] Under nitrogen protection, 250 mL of ultra-dry tetrahydrofuran was added to a double-necked flask, which was then placed in ethanol at -78 °C and stirred. 84 mL of n-butyllithium (210 mmol, 2.5 M) was added, followed by the slow addition of 17.92 mL of 3-bromofuran (200 mmol). The mixture was stirred for 3 hours.

[0053] Under nitrogen protection, 250 mL of ultra-dry tetrahydrofuran was added to a double-necked flask, which was then placed in ethanol at -78 °C and stirred. Under nitrogen protection, 17.58 g of lithium bromide (202.4 mmol) and 28.98 g of cuprous bromide (202 mmol) were added. After the addition was complete, the previously prepared reaction solution was slowly added, and the mixture was stirred for 30 minutes. Then, 8.7 mL of oxalyl chloride (102 mmol) dissolved in 30 mL of tetrahydrofuran was slowly added dropwise to the flask. The mixture was stirred at -78 °C for 2 hours, then moved to room temperature and stirred for 6 hours. The reaction was confirmed by TLC. After the solvent was removed under vacuum, a saturated ammonium chloride solution was added, and the mixture was extracted with dichloromethane. The resulting product was purified by column chromatography on silica gel using petroleum ether and ethyl acetate as eluents, yielding 17.43 g of 1,2-bis(furan-3-yl)ethane-1,2-dione (Formula 2), in 91% yield.

[0054] Under nitrogen protection, 400 mL of ultra-dry dichloromethane was added to a double-necked flask, which was then placed at 0 °C. With stirring, 1.36 g of 1,2-bis(furan-3-yl)ethane-1,2-dione (7.15 mmol) and 1.79 g of 2,3-dichloro-5,6-dicyanobenzoquinone (7.87 mmol) as shown in Formula 2 were added. After stirring for 5 minutes, 4 mL of trifluoromethanesulfonic acid was added, and the reaction was stirred for another 5 minutes. The reaction was then quenched with water. Extraction was performed with dichloromethane, and the solution was dried over anhydrous sodium sulfate. After filtration, volatiles were removed under vacuum, and the solution was purified by column chromatography on silica gel using dichloromethane as the eluent, yielding 935 mg of bis(furanophenylenedione) as shown in Formula 3, with a yield of 70%. 1 H NMR (CDCl3,400 MHz, δ / ppm): 7.48 (s, 2H), 6.79 (s, 2H). 13 C NMR (CDCl3, 100 MHz, δ / ppm): 173.42, 150.24, 144.39, 117.87, 109.77.

[0055] Under nitrogen protection, 1.2 g of bis(furanophenylenedione) (6.38 mmol) and 1.11 g of hydroxylamine hydrochloride (15.95 mmol) as shown in Formula 3 were added to a double-necked flask, followed by 65 mL of ultra-dry ethanol. The mixture was stirred at 80 °C for 16 hours. After the reaction was complete, the mixture was cooled to room temperature, and 147 mg of palladium catalyst on carbon was added under a protective gas atmosphere. The mixture was stirred at 65 °C, and 11 mL of hydrazine hydrate in ethanol was slowly added dropwise. After the addition was complete, the temperature was raised to 85 °C, and the mixture was stirred for 24 hours. After the reaction was complete, the catalyst was removed by diatomaceous earth, and the mixture was washed with ethanol. The solvent was removed under vacuum, and water was added to obtain a light yellow suspension. Filtration yielded a light yellow solid, which is bis(furanophenylenediamine) as shown in Formula 5.

[0056] Under nitrogen protection, triethylamine and 6.0 mL of ultra-dry dichloromethane were added to a two-necked flask containing bis(furanophenylenediamine) as shown in Formula 5. 8.6 mL of thionyl chloride solution was then slowly added dropwise, and the mixture was stirred at 40 °C for 4 hours. After the reaction was complete, dilute hydrochloric acid was added to quench the reaction. The mixture was poured into a separatory funnel, extracted with dichloromethane, dried over anhydrous sodium sulfate, filtered, and purified under vacuum by column chromatography on silica gel. Petroleum ether and ethyl acetate were used as eluents to obtain 322 mg of the corresponding bis(furanophenylenediamine) as shown in Formula 6, with a yield of 85%. 1 H NMR (CDCl3,400 MHz, δ / ppm): 7.82-7.83 (d,2H), 7.41-7.42 (d, 2H). 13 C NMR (CDCl3,100 MHz, δ / ppm):155.52, 145.27, 143.22,112.75, 106.43.

[0057] Example 2

[0058] Equation 7a;

[0059] The compound shown in formula 7a was prepared using the compound of formula 6 obtained in Example 1 as a raw material.

[0060]

[0061] At room temperature, 120 mg of 0.555 mmol of bis(furanobenzothiadiazole) (Formula 6), 4 mL of chloroform, and 4.8 mL of acetic acid solution were added to a 50 mL double-necked flask. 1.1 mL of elemental bromine (21.50 mmol) was added, and the mixture was stirred under reflux for 8 hours. The reaction was quenched with saturated sodium sulfite solution, extracted with dichloromethane, dried over anhydrous sodium sulfate, filtered, and purified by column chromatography on silica gel using petroleum ether and ethyl acetate as eluents. This yielded 146.7 mg of the bis(furanobenzothiadiazole) skeleton compound (Formula 7), with a yield of 70.7%. 1 H NMR (CDCl3,400 MHz, δ / ppm): 7.34(s, 2H). 13 C NMR (CDCl3, 100 MHz, δ / ppm): 150.75, 143.09, 127.71, 115.98, 108.39.

[0062] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A compound based on a bisfuranobenzothiadiazole skeleton, characterized in that: The structure is shown in Equation 7; Formula 7; R1 is hydrogen or halogen.

2. The compound based on the bisfuranobenzothiadiazole skeleton according to claim 1, characterized in that: R1 can be F, Cl, Br, or I.

3. A method for preparing the compound based on the bisfuranobenzothiadiazole skeleton as described in claim 1 or 2, characterized in that: The synthesis method is as follows: Among them, the compounds of formula 6 or formula 7 are compounds based on the bisfuranobenzothiadiazole skeleton.

4. The method for preparing the compound based on the bisfuranobenzothiadiazole skeleton according to claim 3, characterized in that: The specific steps are as follows: Step 1: Add the compound shown in Formula 1 to a first anhydrous organic solvent containing organolithium, react at -70~-78℃, then add lithium bromide and cuprous bromide, stir and react; then add oxalyl chloride and stir and react; to prepare the compound of Formula 2; Step 2: Add the compound of formula 2, the oxidant and the activating substance to the second anhydrous organic solvent, and stir the reaction at 0°C to obtain the compound of formula 3; Step 3: Add a reducing agent and a third anhydrous solvent to a container containing compound of formula 3, heat the mixture at 70-85°C to obtain compound of formula 4, then add a catalyst and a reducing agent, and react at 65-85°C to obtain compound of formula 5; add compound of formula 5 and a halogen-containing inorganic compound to a fourth solvent to react and obtain compound of formula 6.

5. The method for preparing the compound based on the bisfuranobenzothiadiazole skeleton according to claim 4, characterized in that: It also includes, Step 4: Add the fifth solvent and halogen source to the container containing compound 6, and stir the reaction at 60~80℃ to obtain compound 7.

6. The method for preparing compounds based on the bisfuranobenzothiadiazole skeleton according to claim 4 or 5, characterized in that: In step one, the first anhydrous organic solvent is ultra-dry tetrahydrofuran, the organolithium is n-butyllithium, the molar ratio of compound 1 to lithium bromide is 1.0:1.0~1.2, the molar ratio of lithium bromide to cuprous bromide is 1.0:1.0~1.2, and the molar ratio of organolithium to 3-bromofuran is 1-1.

05.

7. The method for preparing compounds based on the bisfuranobenzothiadiazole skeleton according to claim 4 or 5, characterized in that: The oxidant and activator are ferric chloride and nitromethane, or molybdenum pentachloride and nitromethane, or vanadium trifluoride and boron trifluoride ether solution, or (bis(trifluoroacetoxy)iodo)benzene and boron trifluoride ether solution, or DDQ and trifluoromethanesulfonic acid; the second anhydrous organic solvent is ultra-dry dichloromethane; the molar ratio of 1,2-bis(furan-3-yl)ethane-1,2-dione to the oxidant and activator is 1.0:1~1.2:6~6.

5.

8. The method for preparing compounds based on the bisfuranobenzothiadiazole skeleton according to claim 4 or 5, characterized in that: When preparing compound of formula 4, the reducing agent is hydroxylamine hydrochloride, the third anhydrous organic solvent is anhydrous ethanol, and the molar ratio of compound of formula 3 to reducing agent is 1.0:2.5~3.0; When preparing compound of formula 5, the catalyst is palladium on carbon, the reducing agent is hydrazine hydrate, and the molar ratio of compound of formula 4, catalyst and reducing agent is 1.0:0.8~1.2:30.0~50.0; When preparing compound 6, the fourth solvent is dichloromethane / triethylamine or N,N-dimethylformamide, the halogenated inorganic compound is sulfoxide or disulfur dichloride, and the molar ratio of diamine compound to halogenated inorganic compound is 1:2.5~4.

0.

9. The method for preparing the compound based on the bisfuranobenzothiadiazole skeleton according to claim 5, characterized in that: The halogen source is at least one of xenon difluoride, elemental bromine, elemental chlorine, and elemental iodine; the fifth solvent is at least one of dichloromethane, chloroform, and tetrahydrofuran; the molar ratio of the compound of formula 6 to the halogen source is 1:2.0~2.

2.

10. The method for preparing compounds based on the bisfuranobenzothiadiazole skeleton according to claim 4 or 5, characterized in that: The synthesis process is carried out under a protective gas condition, with nitrogen as the protective gas.

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