A boron-nitrogen doped polycyclic aromatic hydrocarbon compound and a method of synthesizing the same

Abstract

The application discloses a boron-nitrogen doped polycyclic aromatic compound and a synthesis method thereof, and relates to the technical field of organic synthesis. The application takes o-bromonitrobenzene as raw material, and first carries out a Bartoli reaction with vinyl magnesium bromide to synthesize 7-bromoindole; then carries out twice coupling reactions under the action of a metal catalyst to form a dimer of indole; carries out a reaction of the dimer of indole with di-tert-butyl dicarbonate to obtain a single Boc dimer of indole; carries out a borohydration reaction on the single Boc dimer of indole to obtain a boron-containing intermediate; and finally carries out a reaction with a Grignard reagent to obtain the boron-nitrogen doped polycyclic aromatic compound. The synthesis method has the characteristics of a relatively short reaction path, simple operation method and mild reaction conditions. Meanwhile, the compound synthesized by the application is sensitive to fluoride ions and has a high fluorescence quantum yield, and can be applied to the fields of fluoride ion sensors and organic photoelectric materials, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a boron-nitrogen-doped polycyclic aromatic hydrocarbon compound and its synthesis method. Background Technology

[0002] In recent decades, the study of heteroatom-doped polycyclic aromatic hydrocarbons (PAHs) has attracted widespread interest. Various heteroatom-doped conjugated aromatic hydrocarbons have emerged. Boron-doped PAHs, in particular, are well-known for their unique properties. Boron atoms possess an empty p orbital, allowing them to bind with other electron-rich heteroatoms and generate charge transfer within the molecule. This results in photoelectric physical properties entirely different from those of all-carbon conjugated systems, significantly improving the performance of organic optoelectronic devices (Mikinori Ando.; Mika Sakai.; Naoki Ando.; Masato Hirai and Shigehiro Yamaguchi. Org. Biomol. Chem. 2019, 17, 500-5504.). Boron-containing π-systems now have wide applications in medicinal chemistry and organic materials chemistry. Boron-doping design strategies have been widely used to extend the π-conjugation of PAHs and modulate their electronic structures in catalysis, anion bonding, tunable luminescence, and optoelectronic device material design. However, boron atoms are unstable, and their empty p orbitals are highly susceptible to attack by nucleophiles. Therefore, when designing and synthesizing boron-containing conjugated aromatics, groups with large steric hindrance are often introduced to stabilize boron atoms, or N is introduced into boron-containing π systems to form BN bonds, which can also increase the stability of the entire system.

[0003] In recent years, the substitution of C=C bonds in aromatic compounds with BN bonds to construct BN aromatics has attracted considerable interest. While BN aromatics retain their planar structure and aromaticity, their electronic properties are significantly affected. These CC / BN isomers have been utilized in medicinal chemistry and the design of ligands for catalysis, with primary interest in materials science. Furthermore, BN-PAHs have been applied to the design of novel optoelectronic materials, such as organic field-effect transistors (OFETs), organic photovoltaic devices (OPVS), and organic light-emitting diodes (OLEDs).

[0004] Pyrene, a member of the polycyclic aromatic hydrocarbon family, possesses high fluorescence efficiency, carrier mobility, and excitoassociation emission efficiency, along with characteristics such as electron richness, macrocyclic conjugation, ease of chemical modification, and good crystallinity. In solution, pyrene exhibits strong blue fluorescence, high quantum yield, and excellent optical properties. The fluorescence properties of pyrene and its derivatives have been used for the detection of guest molecules and microenvironments. In 1837, Laurent first discovered pyrene in the residues after the dry distillation of coal tar. Subsequently, Graebe used CS2 extraction to separate pyrene. In 1913, Weitzenbock et al. discovered the first efficient method for synthesizing pyrene using xylene as a raw material, laying the foundation for scientists' research on pyrene and its derivatives. The synthesis of boron-nitrogen-doped polycyclic aromatic hydrocarbons (PAHs) was first reported in 1958 by the Dewar group. They synthesized the first 9,10-boronazphenanthroline and its derivatives via a Friedel-Crafts reaction using o-vinylaniline and boron trichloride catalyzed by excess aluminum trichloride. In 1960 and 1964, the Dewar group published the first methods for synthesizing pyrene with a double boron-nitrogen doping structure and pyrene with a single boron-nitrogen doping structure, respectively, similar to their reported method for pyrene. In 2007, the Piers group reported a method for synthesizing pyrene-like aromatics with a BN unit as the central structure. Studies have shown that boron-nitrogen-doped aromatics and all-carbon aromatics exhibit distinctly different properties. BN aromatics are more easily reduced, and their fluorescence spectra show a significant redshift. In 2015, the Wang Suning research group, in collaboration with the Gong and Lu groups, synthesized double boron-nitrogen-doped pyrene compounds using photocatalysis or electrocatalysis, and successfully assembled them as light-emitting layers in organic light-emitting devices.

[0005] With the continuous efforts of researchers, many simple synthesis methods have been invented. In the research process, it was discovered that boron-nitrogen doping can effectively regulate the photoelectric physical properties of aromatic systems. Boron-nitrogen-doped polycyclic conjugated aromatic hydrocarbons have successfully aroused people's research interest. The unique photoelectric properties and supramolecular properties of these compounds have great application value in the fields of organic optoelectronic materials, energy storage, field emission, etc. Their practical application in the field of organic semiconductor devices (such as OFETS, OPVS, and OLEDS) has also attracted attention. Due to their unique properties, they are also of great significance to the future application of solar energy and the development of photocatalysis. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a method for synthesizing boron-nitrogen-doped polycyclic aromatic hydrocarbon compounds, which provides more synthetic schemes for obtaining more efficient organic optoelectronic materials.

[0007] This invention is achieved using the following technical solution:

[0008] A method for synthesizing boron-nitrogen-doped polycyclic aromatic hydrocarbons, the specific synthetic route is as follows:

[0009]

[0010]

[0011] In the formula, R1 is an alkyl group, aryl group (benzene ring, thiophene ring, furan ring, pyrrole, pyridine, benzothiophene, benzofuran, benzopyrrole, benzopyridine, naphthyl ring, anthracene ring, phenaene, tetraphenylene, pyrene, etc.). (Linear or angled compounds such as pentacene, hexaphene, indene, fluorene, etc.). The structural formula of compound 5 described in this invention includes, but is not limited to, the following structural formulas:

[0012]

[0013]

[0014] The method for synthesizing boron-nitrogen-doped polycyclic aromatic hydrocarbon compounds according to the present invention includes the following steps:

[0015] S1. Using o-bromonitrobenzene as a raw material, 7-bromoindole is synthesized by reacting it with vinyl magnesium bromide in an organic solvent via the Bartoli reaction.

[0016] S2. The 7-bromoindole is first coupled with pinacol diboronate under the action of a metal catalyst, and then 7-bromoindole (i.e., compound 2) is added to carry out a secondary coupling reaction to form a dimer of indole.

[0017] S3. The indole dimer is reacted with di-tert-butyl dicarbonate to obtain a mono-Boc indole dimer;

[0018] S4. The indole dimer of the single Boc is subjected to a hydroboration reaction with boron trichloride to obtain a boron-containing intermediate.

[0019] S5. The boron-containing intermediate is reacted with Grignard reagent to obtain a boron-nitrogen-doped polycyclic aromatic hydrocarbon compound.

[0020] Preferably, the organic solvent in step S1 is tetrahydrofuran, and the Bartoli reaction is carried out under nitrogen protection at a temperature of -40 to 50°C for 40 to 60 minutes with stirring.

[0021] Preferably, in step S1, the molar ratio of o-bromonitrobenzene to vinyl magnesium bromide is 1:3.0 to 3.2.

[0022] Preferably, the metal catalyst in step S2 is 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride or tetra(triphenylphosphine)palladium.

[0023] Preferably, the molar ratio of indole dimer to di-tert-butyl dicarbonate in step S3 is 1:1.1 to 1.5.

[0024] Preferably, the molar ratio of the indole dimer of the single Boc to boron trichloride in step S4 is 1:3.0 to 4.0.

[0025] Preferably, the temperature of the borohydride reaction in step S4 is 100–120°C, and the reaction time is 10–15 h.

[0026] The present invention involves reacting the prepared boron-nitrogen-doped polycyclic aromatic hydrocarbon compound (i.e., compound 5) as follows to obtain compound 7. The specific synthetic route is as follows:

[0027]

[0028]

[0029] Where R2 is an alkyl group, aryl group (benzene ring, thiophene ring, furan ring, pyrrole, pyridine, benzothiophene, benzofuran, benzopyrrole, benzopyridine, naphthyl ring, anthracene ring, phenaene, tetraphenylene, pyrene, etc.). (Linear or angled pentane, hexaphene, indene, fluorene, etc.). Wherein R2 can also be a single substituted halogen atom X: F, Cl, Br, I. Compound 7 of the present invention includes, but is not limited to, the following structural formulas:

[0030]

[0031]

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention provides a synthetic route for boron-nitrogen-doped polycyclic aromatic hydrocarbons. The synthetic method of this invention features a short reaction path, simple operation, and mild reaction conditions. Furthermore, the compounds synthesized in this invention exhibit high sensitivity to fluoride ions and high fluorescence quantum yield, making them suitable for applications in fluoride ion sensors and organic optoelectronic materials, and demonstrating broad application prospects. Attached Figure Description

[0034] Figure 1 This is the 1H NMR spectrum of compound 5a;

[0035] Figure 2 This is the carbon NMR spectrum of compound 5a;

[0036] Figure 3 This is the infrared spectrum of compound 5a;

[0037] Figure 4This is the 1H NMR spectrum of compound 6a;

[0038] Figure 5 Compound 5a at a concentration of 1×10 -5 Absorption spectrum of M in dichloromethane solution;

[0039] Figure 6 Compound 5a at a concentration of 1×10 -5 Emission spectrum of M in dichloromethane solution;

[0040] Figure 7 This is the emission spectrum of compound 5a with different concentrations of fluoride ions added to a tetrahydrofuran solution. Detailed Implementation

[0041] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be thorough and complete.

[0042] Example 1

[0043] A method for synthesizing a boron-nitrogen-doped polycyclic aromatic hydrocarbon compound (Example 5a) is described below:

[0044]

[0045] The steps are as follows:

[0046] 1) Synthesis of Compound 2: A solution of vinyl magnesium bromide (1 M in tetrahydrofuran, 30 mL, 29.86 mmol, 3.0 equivalent) was slowly added to a solution of 2-bromonitrobenzene (2 g, 9.95 mmol, 1.0 equivalent) in anhydrous tetrahydrofuran (20 mL), and stirred under nitrogen at -45 °C for 45 min. The mixture was then poured into a saturated ammonium chloride solution (50 mL) and extracted three times with ethyl acetate (3 × 50 mL). The collected organic phase was dried over magnesium sulfate and concentrated under reduced pressure. Purification by chromatography (petroleum:ethyl acetate = 20:1) yielded an orange solid (Compound 2).

[0047] 1 H NMR (400MHz, CDCl3): δ8.34(br,1H,NH),7.60(d,J=8.1Hz,1H,Ar),7.36(d,J=7.6Hz,1H, Ar),7.26-7.28(m,1H,Ar),7.02(dd,J1=8.1Hz,J2=7.6Hz,1H,Ar),6.64-6.66(m,1H,Ar).

[0048] 2) Synthesis of Compound 3: Compound 2 (1.00 equiv, 2.56 mmol, 500.3 mg), 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride (0.05 equiv, 0.73 mmol, 93.8 mg), pinacol diboronate (1.00 equiv, 2.56 mmol, 651.1 mg), and potassium acetate (3.60 equiv, 9.23 mmol, 905.8 mg) were weighed into a reaction flask, and the atmosphere was purged three times. Under nitrogen protection, N,N-dimethylformamide was added and allowed to dissolve completely. The system was heated to 100 °C and refluxed for 2 hours at 400 rpm. Compound 2 (1.00 equiv, 2.56 mmol, 500.4 mg) and tetrakis(triphenylphosphine)palladium (0.08 equiv, 0.21 mmol, 237.2 mg) were weighed and rapidly added into the above reaction flask under a nitrogen atmosphere. Weigh sodium hydroxide (2.00 equiv, 5.13 mmol, 213.1 mg), dissolve it in 2 ml of water, and inject it into a reaction flask using a disposable syringe. Reflux the system at 100 °C for 12 hours, and let it react overnight, resulting in a brownish-red color. The next day, TLC analysis was performed. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, and dried over anhydrous magnesium sulfate. The mixture was filtered, evaporated to dryness, and subjected to column chromatography (PE:EA = 7:1), finally yielding a white solid (compound 3).

[0049] 1 H NMR (400MHz, CDCl3) δ8.22(s,2H,NH),7.71(d,J=8.0Hz,2H,Ar.),7.38(d,J1=7 .2Hz,2H,Ar.),7.26(t,2H,Ar.),7.20(s,2H,Ar.),6.66(t,J1=5.2Hz,2H,Ar.).

[0050] 3) Synthesis of Compound 4: Compound 3 (1.00 equiv, 0.86 mmol, 201.1 mg) and 4-dimethylaminopyridine (0.34 equiv, 0.29 mmol, 35.6 mg) were weighed and placed in a reaction flask, and the atmosphere was purged three times. Under nitrogen protection, triethylamine (1.50 equiv, 1.29 mmol, 180 μL) was injected into the reaction flask using a disposable syringe, followed by the addition of 5 mL of dichloromethane to dissolve it. The disposable syringe was first moistened with di-tert-butyl dicarbonate, and then di-tert-butyl dicarbonate (1.30 equiv, 1.29 mmol, 281.5 mg) was weighed and injected into the reaction flask. The mixture was placed at 0 °C and stirred for 40 min. The refrigeration device was turned off, and the reaction was monitored by TLC. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, and dried over anhydrous magnesium sulfate. The mixture was filtered, evaporated to dryness, and subjected to column chromatography (PE:EA = 15:1), finally yielding a white solid (compound 4).

[0051] 1 H NMR (400MHz, CDCl3): δ7.97(s,1H,NH),7.62-7.65(m,3H,Ar),7.49(dd,J1=6.4Hz,J2=1.2Hz,1H,Ar),7.34-7.39(m,2H,Ar),7.23( t,J=8.0Hz,1H,Ar),7.14(t,J=2.8Hz,1H,Ar),6.71(d,J=3.6Hz,1H,Ar),6.58(dd,J1=3.2Hz,J1=2.0Hz,1H,Ar),0.93(s,9H,CH3).

[0052] 4) Synthesis of Compound 5a: Compound 4 (1.00 equiv, 0.30 mmol, 100 mg) was weighed in a glove box and placed in a sealed tube. 5 ml of toluene was added to dissolve it completely. Boron trichloride (3.00 equiv, 0.90 mmol, 0.90 ml) and triethylamine (3.00 equiv, 0.90 mmol, 0.13 ml) were injected into the sealed tube using two disposable syringes, respectively. After addition, the tube was placed in an oil bath at 110 °C and reacted for 12 hours. The reaction was allowed to proceed overnight. The heating device was then turned off, and the tube was cooled to room temperature. MesMgBr in THF (12.00 equiv, 3.6 mmol, 3.6 ml) was injected into the sealed tube using a disposable syringe in a glove box and reacted at room temperature for 12 hours. The reaction was monitored by TLC. After completion, the mixture was extracted with dichloromethane and water, the organic layers were combined, and dried over anhydrous magnesium sulfate. The mixture was filtered, evaporated to dryness, and subjected to plate chromatography (PE:EA = 20:1) to finally obtain a light yellow solid (compound 5a).

[0053] 1 H NMR (400MHz, CDCl3): δ7.88(d,J=8.0Hz,2H,Ar),7.82(d,J=7.6Hz,2H,Ar),7.42(d,J=3.2H z,2H,Ar),7.01(s,4H,Ar),6.87(d,J=3.6Hz,2H,Ar),2.43(s,6H,CH3),2.18(s,12H,CH3). .

[0054] Example 2

[0055] Synthetic route of compound 7:

[0056]

[0057] Examples of the above compounds are given below:

[0058]

[0059] A method for synthesizing compound 7a, comprising the following steps:

[0060] (1) Synthesis of compound 6a: Weigh 5a (1.00 equiv, 0.20 mmol, 100 mg) into a reaction flask, add 2 ml of anhydrous DCM, slowly add 0.40 ml of Br2 (1 mol / L, dissolved in DCM), react at 0 °C for 1 hour, after the reaction is complete, extract with DCM / Na2S2O3 solution, collect the organic phase, dry with anhydrous magnesium sulfate, filter, remove the solvent and purify by silica gel column chromatography (using petroleum ether: ethyl acetate = 15:1 as the eluent) to obtain a white solid (compound 6a).

[0061] 1 H NMR (400MHz, CDCl3): δ7.93(d,J=8.0Hz,2H,Ar),7.75(d,J=8.0Hz,2H,Ar),7.44(s,2H,Ar),7.01(s,4H,Ar),2.43(s,6H,CH3),2.22(s,12H,CH3).

[0062] (2) Synthesis of compound 7a: 6a (1.00 equiv, 0.20 mmol, 130 mg), phenylboronic acid (2.20 equiv, 0.44 mmol, 57 mg), tetrakis(triphenylphosphine)palladium (0.10 equiv, 0.02 mmol, 23 mg), and potassium carbonate (6.00 equiv, 1.20 mmol, 152 mg) were weighed into a reaction flask under nitrogen protection. 10 ml of solvent (diox:H2O = 4:1) was added. The system was stirred at 100 °C for 12 hours. After the reaction was completed, the mixture was extracted three times with DCM and water. The organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. The mixture was then purified by column chromatography using petroleum ether as the eluent to obtain a white solid (compound 7a).

[0063] To further investigate the photoelectric physical properties of these compounds, we performed ultraviolet absorption, fluorescence emission, electrochemical property tests, and single-crystal diffraction structure characterization. Taking compound 5a as an example, its photoelectric properties are briefly described. Compound 5a at room temperature reacts with anhydrous dichloromethane (concentration 1×10⁻⁶). -5 In compound M), the maximum absorption wavelength is reached at 326 nm, while the maximum emission wavelength is reached at 469 nm. The fluorescence quantum yield is 37%, and the fluorescence lifetime is 9.87 ns, indicating that compound 5a has certain luminescent properties and can be used to fabricate light-emitting diodes. Furthermore, it can be observed that when TBAF is added, the emission peak around 500 nm gradually decreases, and a new emission peak is generated at 427 nm. These findings lay the foundation for the application of boron-nitrogen-doped fused-ring aromatic hydrocarbons containing pyrrole rings in this invention to optoelectronic materials and fluoride ion sensors.

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A boron-nitrogen-doped polycyclic aromatic hydrocarbon compound, characterized in that, comprising the following structural formula: .

2. The method for synthesizing boron-nitrogen-doped polycyclic aromatic hydrocarbon compounds as described in claim 1, characterized in that, The synthetic route is as follows: .

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