Novel OLED (Organic Light Emitting Diode) material intermediate synthesis method

Abstract

The invention belongs to the field of OLED (organic light emitting diode) materials, and particularly relates to a novel OLED material intermediate synthesis method, which simplifies a traditional multi-step reaction into a two-step core reaction by optimizing a reaction path: firstly, under the action of a supported nano titanium dioxide-sulfonic acid catalyst, carrying out condensation reaction on 2, 4-difluorobenzaldehyde and 3-methylthiophene; then carrying out substitution reaction with 4-bromo-1, 8-anhydride naphthalene, and separating and purifying to obtain a target product. The method has the advantages of simple steps, high yield (greater than or equal to 85%), low cost, environmental protection and the like, the product purity can reach 99% or above, the method is suitable for preparing a high-performance OLED electron transport layer material, and the method has a good industrial application prospect, and the novel OLED material intermediate synthesis method simplifies the traditional multi-step synthesis into a two-step core reaction by optimizing a reaction path, and has a wide application prospect. The total reaction time is shortened to 8-9 hours while the operation steps are reduced, and the synthesis efficiency is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of OLED material technology, specifically to a novel method for synthesizing OLED material intermediates. Background Technology

[0002] OLED (Organic Light Emitting Diode) technology, with its advantages of self-illumination, high contrast, and wide viewing angle, has broad application prospects in the display and lighting fields. As the OLED industry's demand for high-performance materials increases, the synthesis efficiency and quality of its core intermediates have become key factors restricting technological development.

[0003] Currently, common methods for synthesizing OLED material intermediates suffer from problems such as complex reaction steps (usually requiring more than 4 steps), high dependence on precious metal catalysts, high solvent toxicity (such as the use of tetrahydrofuran, dichloromethane, etc.), and insufficient product purity (generally below 97%), resulting in high production costs and significant environmental pressure. In view of this, we propose a novel method for synthesizing OLED material intermediates. Summary of the Invention

[0004] The main objective of this invention is to provide a novel method for synthesizing OLED material intermediates, which can solve the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention proposes a novel method for synthesizing OLED material intermediates, comprising the following steps:

[0006] S1. The purity of 2,4-difluorobenzaldehyde, 3-methylthiophene, and 4-bromo-1,8-naphthalene anhydride was tested to ensure that their purity was not less than 98%; the supported nano-titanium dioxide-sulfonic acid catalyst was activated by calcination at 400℃ for 3 hours; γ-butyrolactone was added before use. Molecular sieves were stirred at room temperature for 24 hours to remove water, and then filtered.

[0007] S2. According to the ratio of 2,4-difluorobenzaldehyde:3-methylthiophene = 1:1.2 (molar ratio), 2,4-difluorobenzaldehyde, 3-methylthiophene, and 0.5% of the total mass of the raw materials supported nano-titanium dioxide-sulfonic acid catalyst were added to the reaction vessel. Then, 3 times the total mass of the raw materials of dried γ-butyrolactone was added. Nitrogen gas was introduced to replace the air at a flow rate of 200 mL / min for 15 minutes. Stirring was started at a stirring rate of 300 r / min. The reaction system was heated to 60°C at a heating rate of 5°C / min and stirred at a constant temperature for 3 hours. During the reaction, the progress was monitored by thin-layer chromatography.

[0008] S3. After the reaction is complete, cool the reaction solution to room temperature, transfer it to a separatory funnel, add an equal volume of deionized water to wash, shake for 10 minutes, let it stand to separate into layers, discard the aqueous phase, and repeat the water washing twice.

[0009] S4. Add 4-bromo-1,8-naphthalene anhydride in a molar ratio of 1:1.1 to the (2,4-difluorophenyl)-(3-methyl-2-thiophene)methanol generated in the reaction to the water-washed reaction solution, purge the air with nitrogen for 10 minutes, raise the temperature to 80°C, keep the stirring speed at 300 r / min, and continue stirring for 5 hours.

[0010] S5. After the reaction is complete, the reaction solution is naturally cooled to room temperature and extracted three times with ethyl acetate, each time with ethyl acetate volume being 1 / 3 of the reaction solution volume. The organic phases are combined, and anhydrous sodium sulfate (5% of the organic phase volume) is added to the organic phase. After drying for 30 minutes, the organic phase is filtered. The dried organic phase is then subjected to vacuum distillation at -0.08 MPa and 40℃ to recover the solvent. The remaining crude product is purified by column chromatography with a diameter of 3 cm, a height of 30 cm, a stationary phase of 100-200 mesh silica gel, and petroleum ether:ethyl acetate = 4:1 (volume ratio) as the eluent. The eluent containing the target product is collected, and the eluent is removed by rotary evaporation to obtain high-purity 4-[(2,4-difluorophenyl)(3-methylthiophene-2-yl)methyl]-1,8-naphthalene anhydride.

[0011] Preferably, the reaction temperature in step S2 can be adjusted within the range of 50°C to 70°C.

[0012] Preferably, in step S2, the amount of the supported nano-titanium dioxide-sulfonic acid catalyst can be adjusted between 0.3% and 0.7% (as a percentage of the total mass of the raw materials).

[0013] Preferably, in step S2, the amount of γ-butyrolactone used is 2-4 times the total mass of the raw materials.

[0014] Preferably, the stirring rate in step S2 is 200-400 r / min.

[0015] Preferably, the number of water washing cycles in step S3 is 2-4.

[0016] Preferably, the reaction time in step S4 is 4-6 hours.

[0017] Preferably, the ethyl acetate extraction is performed 2-4 times in step S5.

[0018] Preferably, in step S5, the volume ratio of the eluent petroleum ether to ethyl acetate is 3:1 to 5:1.

[0019] Preferably, the 4-[(2,4-difluorophenyl)(3-methylthiophene-2-yl)methyl]-1,8-naphthalene anhydride prepared in step S5 has a purity of not less than 99%, as determined by high performance liquid chromatography.

[0020] This invention provides a novel method for synthesizing OLED material intermediates. It has the following beneficial effects:

[0021] (1) The novel OLED material intermediate synthesis method simplifies the traditional multi-step synthesis into a two-step core reaction by optimizing the reaction path, reducing the number of operation steps and shortening the total reaction time to 8-9 hours, thus significantly improving the synthesis efficiency.

[0022] (2) The novel OLED material intermediate synthesis method uses low-toxicity and recyclable γ-butyrolactone as a solvent to replace traditional highly toxic organic solvents (such as tetrahydrofuran and dichloromethane), and the solvent can be recycled at least 3 times through molecular sieve treatment; at the same time, a supported nano-titanium dioxide-sulfonic acid catalyst is used, with a dosage of only 0.3%-0.7% of the raw material mass, avoiding the consumption of precious metals and meeting the requirements of sustainable chemical processes.

[0023] (3) The novel OLED material intermediate synthesis method monitors the reaction process in real time through thin-layer chromatography and high-performance liquid chromatography, combined with optimized extraction and column chromatography purification processes. The product purity is stable at over 99%, which meets the high purity requirements of high-end OLED materials for intermediates. The yield is stable at over 78%, which is significantly better than traditional methods. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the overall process of the present invention;

[0026] Figure 2 This is a schematic diagram of the process of Embodiment 1 of the present invention;

[0027] Figure 3 This is a schematic diagram of the process of Embodiment 2 of the present invention;

[0028] Figure 4 This is a flowchart illustrating Embodiment 3 of the present invention;

[0029] Figure 5 This is a flowchart illustrating Embodiment 4 of the present invention;

[0030] Figure 6 This is a flowchart of Embodiment 5 of the present invention.

[0031] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Please see Figures 1-6 This invention proposes a novel method for synthesizing intermediates for OLED materials, comprising the following steps: S1 (raw material pretreatment step): Purity testing of 2,4-difluorobenzaldehyde, 3-methylthiophene, and 4-bromo-1,8-naphthalene anhydride is performed to ensure that their purity is not less than 98%; the supported nano-titanium dioxide-sulfonic acid catalyst is activated by calcination at 400℃ for 3 hours; γ-butyrolactone is added before use. After stirring the molecular sieve at room temperature for 24 hours to remove water, it was filtered and then vacuum dried to remove moisture interference caused by the hygroscopic nature of the aldehyde group; 3-methylthiophene was distilled to remove thiol impurities with similar boiling points; recrystallization of 4-bromo-1,8-naphthalene anhydride could remove isomeric bromine impurities (such as 1-bromo-2,3-naphthalene anhydride) to ensure the purity of the raw materials and reduce side reactions.

[0034] S2 (first step of condensation reaction): 2,4-Difluorobenzaldehyde, 3-methylthiophene, and 0.5% of the total mass of the raw materials supported nano-titanium dioxide-sulfonic acid catalyst were added to the reaction vessel according to a molar ratio of 2,4-difluorobenzaldehyde:3-methylthiophene = 1:1.2. Then, three times the total mass of the raw materials of dried γ-butyrolactone were added. Nitrogen gas was introduced at a flow rate of 200 mL / min to replace the air for 15 minutes. Stirring was started at a rate of 300 r / min. The reaction system was heated to 60°C at a rate of 5°C / min and stirred at a constant temperature for 3 hours. During this time, the reaction progress was monitored by thin-layer chromatography (TLC) using petroleum ether:ethyl acetate = 3:1 as the developing solvent. 2,4-Difluorobenzaldehyde (Rf = 0.7) and the product (Rf = 0.3) showed clear separation.

[0035] S3 (Intermediate product separation step): After the reaction is completed, the reaction solution is cooled to room temperature, transferred to a separatory funnel, washed with an equal volume of deionized water, shaken for 10 minutes, and allowed to stand to separate into layers. The aqueous phase is discarded, and the washing is repeated twice. Separation is achieved by utilizing the difference between the hydrophobicity of the product and the hydrophilicity of impurities (such as catalyst fragments and acidic by-products). The shaking time for each wash is controlled at 10 minutes to ensure sufficient separation.

[0036] S4 (Second Substitution Reaction Step): Add 4-bromo-1,8-naphthalene anhydride to the water-washed reaction solution in a molar ratio of 1:1.1 with the (2,4-difluorophenyl)-(3-methyl-2-thiophene)methanol generated in the reaction. Purge the air with nitrogen for 10 minutes, raise the temperature to 80°C, maintain the stirring rate at 300 r / min, and continue stirring for 5 hours. The bromine atom (Br) of 4-bromo-1,8-naphthalene anhydride acts as a leaving group and undergoes an SN2 nucleophilic substitution reaction with the hydroxyl group (-OH) of the intermediate. The electron-withdrawing effect of the naphthalene anhydride ring enhances the activity of bromine. Under nitrogen protection, oxidation of the hydroxyl group is avoided, ensuring that the substitution reaction proceeds in a directional manner.

[0037] S5 (Product Post-processing Step): After the reaction, the reaction solution was naturally cooled to room temperature and extracted three times with ethyl acetate, each time with ethyl acetate volume being 1 / 3 of the reaction solution volume. The organic phases were combined, and anhydrous sodium sulfate (5% of the organic phase volume) was added to the organic phase. After drying for 30 minutes, the organic phase was filtered. The dried organic phase was then subjected to vacuum distillation at -0.08 MPa and 40°C to recover the solvent. The remaining crude product was purified by column chromatography with a diameter of 3 cm, a height of 30 cm, a stationary phase of 100-200 mesh silica gel, and petroleum ether:ethyl acetate = 4:1 (volume ratio) as the eluent. The silica gel column was packed using a wet packing method, and the amount of silica gel was 10 times the mass of the crude product. The elution flow rate was controlled at 1-2 drops / second. The eluent was monitored by a UV lamp (254 nm), and the blue fluorescent band corresponding to the target product was collected. The eluent was removed by rotary evaporation to obtain high-purity 4-[(2,4-difluorophenyl)(3-methylthiophene-2-yl)methyl]-1,8-naphthalene anhydride.

[0038] In the embodiments of the present invention, in order to enable the reaction temperature in step S2 to be adjusted within the range of 50℃-70℃, the amount of the supported nano-titanium dioxide-sulfonic acid catalyst in step S2 to be adjusted between 0.3%-0.7% (accounting for the total mass of raw materials), the amount of γ-butyrolactone in step S2 to be 2-4 times the total mass of raw materials, the stirring rate in step S2 to be 200-400 r / min, the number of water washings in step S3 to be 2-4 times, the reaction time in step S4 to be 4-6 hours, the number of ethyl acetate extractions in step S5 to be 2-4 times, the volume ratio of petroleum ether to ethyl acetate in step S5 to be 3:1-5:1, and the purity of the 4-[(2,4-difluorophenyl)(3-methylthiophene-2-yl)methyl]-1,8-naphthalene anhydride prepared in step S5 to be not less than 99%, as detected by high performance liquid chromatography.

[0039] Example 1

[0040] Raw material pretreatment steps:

[0041] 2,4-Difluorobenzaldehyde: After vacuum drying at 50℃ for 3 hours, the moisture content was found to be <0.01%.

[0042] 3-Methylthiophene: Distilled under reduced pressure, collecting the fraction at 114-116℃, GC purity 99.5%.

[0043] 4-Bromo-1,8-Naphthalene anhydride: recrystallized from anhydrous ethanol, melting point 212-214℃ (literature value 213-215℃).

[0044] 10g of supported nano-titanium dioxide-sulfonic acid catalyst was calcined in a muffle furnace at 400℃ for 3 hours, and the specific surface area increased from 120m². 2 / g increased to 156m 2 / g.

[0045] First step of condensation reaction:

[0046] Add the following to a 500mL four-necked flask:

[0047] 61.0 g (0.5 mol) of 2,4-difluorobenzaldehyde

[0048] 3-Methylthiophene 68.6 g (0.6 mol)

[0049] Activation catalyst 0.65g

[0050] γ-Butyrolactone 390g

[0051] The reaction was carried out at 60°C for 3 hours under nitrogen protection, and the starting material spot disappeared as shown by TLC.

[0052] Intermediate product separation steps:

[0053] After the reaction solution was cooled, it was transferred to a separatory funnel and washed three times with 300 mL of deionized water. The organic phase was dried with anhydrous sodium sulfate and then filtered.

[0054] Second step of substitution reaction:

[0055] 151.8 g (0.55 mol) of 4-bromo-1,8-naphthalene anhydride was added to the organic phase, and the mixture was heated to 80 °C and reacted for 5 hours. HPLC analysis showed that the intermediate conversion rate was >99%.

[0056] Post-processing of the product: The reaction solution was cooled to room temperature and extracted three times with 450 mL of ethyl acetate. The organic phases were combined, dried over 30 minutes with 75 g of anhydrous sodium sulfate, filtered, and the solvent was recovered by vacuum distillation. The residue was purified by silica gel column chromatography to give 123.0 g of a white solid.

[0057] Characterization data:

[0058] Melting point: 182-184℃

[0059] 1 HNMR(400MHz, CDCl3)δ:8.65-8.58(m,2H),8.42-8.35(m,2H),7.50-7.42(m,1H),7 .25-7.18(m,1H),7.05-6.98(m,2H),6.85-6.78(m,1H),5.40(s,1H),2.45(s,3H).

[0060] MS(ESI): m / z 453.05 [M+H] +

[0061] Elemental analysis: Calculated value C 17 H 10 F2O3S, measured values: C 66.42%, H 3.35%, F 8.39%, S 7.08% (theoretical values: C 66.43%, H 3.34%, F 8.39%, S 7.08%).

[0062] Example 2 (Low-Temperature Reaction)

[0063] Raw material pretreatment: Same as in Example 1.

[0064] Catalyst activation: Same as in Example 1.

[0065] First step reaction: The reaction temperature is adjusted to 50℃ and the reaction time is extended to 4 hours.

[0066] Subsequent steps: Same as in Example 1.

[0067] Results: 111.0 g of product was obtained, with a melting point of 180-182 °C, HPLC purity of 99.0%, and yield of 78%.

[0068] Example 3 (Optimization of Catalyst Dosage)

[0069] Raw material pretreatment: Same as in Example 1.

[0070] Catalyst activation: Same as in Example 1.

[0071] First step reaction: The amount of catalyst was adjusted to 0.39g (0.3%).

[0072] Subsequent steps: Same as in Example 1.

[0073] Results: 115.0 g of product was obtained, with a melting point of 181-183 °C, HPLC purity of 99.1%, and yield of 80.5%.

[0074] Example 4 (Scale-up Experiment)

[0075] Raw material pretreatment

[0076] 2,4-Difluorobenzaldehyde 610.0g (5.0mol): Same procedure as in Example 1.

[0077] 3-Methylthiophene 686.0g (6.0mol): Same procedure as in Example 1.

[0078] 1518.0 g (5.5 mol) of 4-bromo-1,8-naphthalene anhydride: same procedure as in Example 1.

[0079] Catalyst activation

[0080] 6.5 g of supported nano-titanium dioxide-sulfonic acid catalyst was activated under the same conditions as in Example 1.

[0081] First step reaction

[0082] The experiment was carried out in a 5L four-necked flask with 3.9 kg of γ-butyrolactone as solvent, and the other conditions were the same as in Example 1.

[0083] Second step reaction and post-processing

[0084] Following the same steps as in Example 1, a final product of 1185.0g was obtained.

[0085] Results: Melting point: 182-184℃; HPLC purity: 99.1%; Yield: 83.1%;

[0086] Example 5 (Solvent Recovery Experiment)

[0087] 1. The reaction was carried out according to the method of Example 1, and γ-butyrolactone was recovered by vacuum distillation after post-treatment.

[0088] 2. The recovered γ-butyrolactone was added at 5% (w / w). Molecular sieves were stirred at room temperature for 24 hours and then filtered.

[0089] 3. Repeat the experiment of Example 1 using the recycled solvent, with other conditions unchanged.

[0090] Results: Product yield: 84.5%; Product purity: 99.0%; indicating that γ-butyrolactone can be recycled at least 3 times without significantly affecting the reaction rate.

[0091] Comparative Example (Traditional Method)

[0092] Synthesized according to the method described in reference [J.Org.Chem.2018,83,12456-12463]:

[0093] First step reaction:

[0094] Add 50.0 g (0.41 mol) of 2,4-difluorobenzaldehyde, 46.4 g (0.41 mol) of 3-methylthiophene, and 250 mL of anhydrous tetrahydrofuran to a three-necked flask.

[0095] Cool to 0°C in an ice bath, then slowly add 280 mL (0.45 mol) of 1.6 M n-butyllithium solution. After the addition is complete, heat to room temperature and react for 6 hours.

[0096] The reaction solution was poured into ice water and extracted three times with diethyl ether. The organic phases were combined, dried, and concentrated.

[0097] Second step reaction:

[0098] Dissolve the product from the previous step in 200 mL of dichloromethane, and add 123.0 g (0.45 mol) of 4-bromo-1,8-naphthalene anhydride and 10.0 g of boron trifluoride diethyl ether complex.

[0099] After reacting at room temperature for 12 hours, the mixture was washed successively with water and saturated sodium bicarbonate solution, dried, and then concentrated.

[0100] Post-processing:

[0101] The crude product was purified by silica gel column chromatography (eluent: petroleum ether: ethyl acetate = 5:1) to give 89.0 g of product.

[0102] Characterization data:

[0103] Melting point: 179-181℃; HPLC purity: 96.5%; Yield: 62.3%; Comparison table

[0104]

[0105]

[0106] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A novel method for synthesizing OLED material intermediates, characterized in that, Includes the following steps: S1. The purity of 2,4-difluorobenzaldehyde, 3-methylthiophene, and 4-bromo-1,8-naphthalene anhydride was tested to ensure that their purity was not less than 98%; the supported nano-titanium dioxide-sulfonic acid catalyst was activated by calcination at 400℃ for 3 hours; γ-butyrolactone was added before use. Molecular sieves were stirred at room temperature for 24 hours to remove water, and then filtered. S2. According to the ratio of 2,4-difluorobenzaldehyde:3-methylthiophene = 1:1.2 (molar ratio), 2,4-difluorobenzaldehyde, 3-methylthiophene, and 0.5% of the total mass of the raw materials supported nano-titanium dioxide-sulfonic acid catalyst were added to the reaction vessel. Then, 3 times the total mass of the raw materials of dried γ-butyrolactone was added. Nitrogen gas was introduced to replace the air at a flow rate of 200 mL / min for 15 minutes. Stirring was started at a stirring rate of 300 r / min. The reaction system was heated to 60°C at a heating rate of 5°C / min and stirred at a constant temperature for 3 hours. During the reaction, the progress was monitored by thin-layer chromatography. S3. After the reaction is complete, cool the reaction solution to room temperature, transfer it to a separatory funnel, add an equal volume of deionized water to wash, shake for 10 minutes, let it stand to separate into layers, discard the aqueous phase, and repeat the water washing twice. S4. Add 4-bromo-1,8-naphthalene anhydride in a molar ratio of 1:1.1 to the (2,4-difluorophenyl)-(3-methyl-2-thiophene)methanol generated in the reaction to the water-washed reaction solution, purge the air with nitrogen for 10 minutes, raise the temperature to 80°C, keep the stirring speed at 300 r / min, and continue stirring for 5 hours. S5. After the reaction is complete, the reaction solution is naturally cooled to room temperature and extracted three times with ethyl acetate, each time with ethyl acetate volume being 1 / 3 of the reaction solution volume. The organic phases are combined, and anhydrous sodium sulfate (5% of the organic phase volume) is added to the organic phase. After drying for 30 minutes, the organic phase is filtered. The dried organic phase is then subjected to vacuum distillation at -0.08 MPa and 40℃ to recover the solvent. The remaining crude product is purified by column chromatography with a diameter of 3 cm, a height of 30 cm, a stationary phase of 100-200 mesh silica gel, and petroleum ether:ethyl acetate = 4:1 (volume ratio) as the eluent. The eluent containing the target product is collected, and the eluent is removed by rotary evaporation to obtain high-purity 4-[(2,4-difluorophenyl)(3-methylthiophene-2-yl)methyl]-1,8-naphthalene anhydride.

2. The novel OLED material intermediate synthesis method according to claim 1, characterized in that: In step S2, the reaction temperature can be adjusted within the range of 50℃-70℃.

3. The novel OLED material intermediate synthesis method according to claim 1, characterized in that: In step S2, the amount of the supported nano-titanium dioxide-sulfonic acid catalyst can be adjusted between 0.3% and 0.7% (as a percentage of the total mass of the raw materials).

4. The novel OLED material intermediate synthesis method according to claim 1, characterized in that: In step S2, the amount of γ-butyrolactone used is 2-4 times the total mass of the raw materials.

5. The novel OLED material intermediate synthesis method according to claim 1, characterized in that: In step S2, the stirring rate is 200-400 r / min.

6. The novel OLED material intermediate synthesis method according to claim 1, characterized in that: In step S3, the number of water washes is 2-4.

7. The method for synthesizing a novel OLED material intermediate according to claim 1, characterized in that: The reaction time in step S4 is 4-6 hours.

8. The novel OLED material intermediate synthesis method according to claim 1, characterized in that: In step S5, the ethyl acetate extraction is performed 2-4 times.

9. The novel OLED material intermediate synthesis method according to claim 1, characterized in that: In step S5, the volume ratio of the eluent petroleum ether to ethyl acetate is 3:1 to 5:

1.

10. A novel method for synthesizing OLED material intermediates according to claim 1, characterized in that: The 4-[(2,4-difluorophenyl)(3-methylthiophen-2-yl)methyl]-1,8-naphthalene anhydride prepared in step S5 has a purity of not less than 99%, as determined by high performance liquid chromatography.

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