A method for preparing a sulfonium salt that can be used as a photoacid generator

Abstract

This invention provides a novel method for preparing sulfonium salt compound 1, a photoacid generator, belonging to the field of organic chemistry. The method is characterized by the reaction of compound 3 and compound 4 in the presence of a monovalent copper catalyst and an organic solvent to obtain compound 1. The synthetic route is as follows: This invention uses readily available and inexpensive p-tert-butylbenzene as a starting material, and obtains a high-purity product through an iodonium reaction and a sulfonium reaction. The synthetic method of this invention uses readily available and inexpensive substrates, has a short route, and low cost. It uses a monovalent copper catalyst such as cuprous iodide instead of a divalent copper catalyst such as copper acetate, which improves the yield of sulfonium salt, avoids the use of toxic divalent copper and toxic reagents, and unexpectedly reduces the residual copper ion content, which is beneficial for obtaining high-quality photoresist and has good market value and far-reaching practical significance.

Description

Technical Field

[0001] This invention relates to the preparation of a sulfonium salt, a photoacid generator, belonging to the field of organic chemistry. Background Technology

[0002] Photoresist, also known as photoresist, is a medium that uses photochemical reactions to transfer patterns. It is a diverse class of fine chemicals with varying properties and extremely wide applications. Photoresist is a photosensitive liquid mixture composed of three main components: photosensitive resin, sensitizer, and solvent. In the photolithography process, it is used as an anti-corrosion coating material. Depending on the development method, photoresist is divided into positive photoresist and negative photoresist. The development of positive photoresist utilizes a photoacid generator to catalyze the decomposition of the photoresist, changing the polymer polarity. After treatment with the developer, either positive or negative development is achieved. The chemical structure of the anions and cations of photoacid generators can determine or affect the characteristics and properties of photoacid generators. Different chemical compositions, shapes and sizes may also cause significant changes in the solubility, diffusivity, stability, volatility, acidity and catalytic activity of the photoacid generator or its conjugate photoacid. These changes can directly lead to changes in many parameters related to the performance of photoresists, such as curing efficiency, photosensitivity, sensitivity, post-exposure delay stability, resolution, standing wave ratio, image profile and acid loss.

[0003] Compound 1, chemically named 4-(4-tert-butylphenyl)-1,4-oxothiacyclohexane-4-methylsulfate, is a sulfonium salt that can be used as a photoacid generator. It can provide cations for the production of different photoacid generators, replacing the common triphenylsulfonium salt and meeting the requirements of different process conditions for photoacid generators.

[0004]

[0005] However, there are few reports on the preparation of this compound, and it is unstable during preparation, easily losing its methyl group. Furthermore, during the research process of this invention, the researchers found that the products obtained by existing preparation methods have a large amount of residual copper ions. Controlling the metal ion content is one of the core aspects of photoresist purity control. Even trace amounts of metal ions can cause mobile ion contamination, leading to changes in the threshold voltage of the device and adversely affecting its performance. Excessive residual copper ions in the photoacid generator directly affect the quality of subsequent photoresists; excessive metal ions may lead to a decrease in photoresist performance, such as resolution and contrast. Additionally, existing technologies use toxic divalent copper catalysts and the toxic solvent chloroform, posing potential hazards and making them unsuitable for industrial-scale production.

[0006] Therefore, a new preparation method is needed to solve the above problems in the existing technology. Summary of the Invention

[0007] This invention provides a novel method for preparing sulfonium salt compound 1, a photoacid generator. Using readily available and inexpensive p-tert-butylbenzene as a starting material, the product with HPLC purity ≥99% can be obtained through iodonium reaction and sulfonium reaction. The synthetic method of this invention has advantages such as readily available and inexpensive substrates, a simple route, low cost, avoidance of the use of toxic reagents, stable product, and low copper ion residue.

[0008] The synthesis process route of this invention is as follows:

[0009]

[0010] Includes the following steps:

[0011] Step 1: Compound 3 and Compound 4 react in the presence of a monovalent copper catalyst and an organic solvent to obtain Compound 1.

[0012] As a further improvement of the present invention, including but not limited to, the monovalent copper catalyst in step 1 is selected from cuprous chloride, cuprous bromide, and cuprous iodide, preferably cuprous iodide.

[0013] As a further improvement of the present invention, including but not limited to, the inventors have found that using cuprous iodide is superior to other monovalent copper catalysts; when using divalent copper catalysts, the high copper ion content of compound 1 will have an adverse effect on the quality of subsequent photoresist, and only when using monovalent copper catalysts, especially cuprous iodide, can compound 1 with high purity and low copper ion content be obtained.

[0014] As a further improvement of the present invention, including but not limited to, the molar ratio of compound 3 and monovalent copper catalyst in step 1 is 1:(0.01 to 0.5), preferably 1:(0.01 to 0.3).

[0015] As a further improvement of the present invention, in some embodiments, the molar ratio of compound 3 and monovalent copper catalyst in step 1 is 1:(0.01 to 0.05).

[0016] As a further improvement of the present invention, including but not limited to, the organic solvent in step 1 is chlorobenzene.

[0017] As a further improvement of the present invention, including but not limited to, the reaction temperature of step 1 is 40-90°C, preferably 50-80°C.

[0018] As a further improvement of the present invention, including but not limited to, the reaction time of step 1 is 0.5 to 5 hours, preferably 0.5 to 4 hours.

[0019] As a further improvement of the present invention, including but not limited to, the molar ratio of compound 3 and compound 4 in step 1 is selected from 1:(1 to 3), preferably 1:(1 to 2).

[0020] As a further improvement of the present invention, including but not limited to, in some embodiments, in step 1, compound 3 is dissolved in chlorobenzene, compound 4 and cuprous iodide are added, the temperature is raised to 50-70°C, and the reaction is carried out for 0.5-3 hours to obtain compound 1.

[0021] As a further improvement of the present invention, including but not limited to, in some embodiments, after the reaction in step 1 is complete, the mixture is cooled to room temperature and stirred for a period of time, and then filtered to obtain compound 1. The above compound 1 can be further purified by multiple slurrying or recrystallization; the slurrying solution is, for example, one of methanol and methyl tert-butyl ether.

[0022] As a further improvement of the present invention, including but not limited to, in some embodiments, after the reaction in step 1 is complete, the mixture is cooled to room temperature and stirred for a period of time, filtered to obtain compound 1, methanol is added at room temperature and stirred for a period of time, then filtered, the filtrate is concentrated, and then recrystallized using methyl tert-butyl ether to obtain pure compound 1.

[0023] Furthermore, compound 3 was prepared by the following method:

[0024]

[0025] Includes the following steps:

[0026] Step 2: Compound 2 reacts in the presence of an acidic reagent and iodate to give an intermediate product;

[0027] Step 3: The intermediate product obtained in Step 2 and dimethyl sulfate react in an organic solvent to obtain compound 3.

[0028] As a further improvement of the present invention, including but not limited to, the acidic reagent in step 2 is selected from one or more of sulfuric acid, acetic acid, and acetic anhydride.

[0029] As a further improvement of the present invention, including but not limited to, the iodate in step 2 is selected from one or more of potassium iodate, lithium iodate, and sodium iodate, preferably potassium iodate.

[0030] As a further improvement of the present invention, including but not limited to, the reaction temperature of step 2 is -20 to 10°C, preferably -15 to 5°C.

[0031] As a further improvement of the present invention, including but not limited to, the reaction time of step 2 is 12 to 36 hours, preferably 18 to 30 hours.

[0032] As a further improvement of the present invention, including but not limited to, after the reaction in step 2 is complete, the reaction is quenched with water, filtered, extracted with an organic solvent, the organic phases are combined, deionized water is added for extraction, the aqueous phases are combined, and the temperature is lowered to -5 to 5°C to obtain the intermediate product.

[0033] Furthermore, the organic solvent is toluene.

[0034] As a further improvement of the present invention, including but not limited to, in step 3, the intermediate product obtained in step 2 and dimethyl sulfate are refluxed to obtain compound 3.

[0035] As a further improvement of the present invention, including but not limited to, the organic solvent in step 3 is selected from any one or more of methanol, ethanol, and isopropanol, preferably methanol.

[0036] As a further improvement of the present invention, including but not limited to, the reaction time of step 3 is 2 to 18 hours, preferably 2 to 10 hours.

[0037] As a further improvement of the present invention, including but not limited to, step 3 may optionally include post-treatment after the reaction is completed, the post-treatment including removing the solvent by vacuum evaporation and recrystallizing with an organic solvent; for example, the organic solvent is tetrahydrofuran.

[0038] The main advantages of the method of the present invention are:

[0039] 1. Existing technologies use toxic divalent copper catalysts and toxic solvents like chloroform, posing potential hazards and unsuitable for large-scale industrial production. The divalent copper used in existing technologies operates on Lewis acid catalysis, while monovalent copper uses metal catalysis similar to the Ullmann reaction. The mechanisms of these two reactions differ. During the invention process, the inventors unexpectedly discovered that using monovalent copper catalysts, such as cuprous iodide, can efficiently yield the target sulfonium salt with low copper ion residue, demonstrating unexpected technical advantages. Furthermore, they found that using chlorobenzene as a solvent can further increase the yield by 15% while maintaining low copper ion residue, and also solves the problem of using toxic reagents in existing technologies.

[0040] 2. This invention uses a monovalent copper catalyst, such as cuprous iodide, instead of a divalent copper catalyst such as copper acetate, which improves the yield of sulfonium salts and avoids the use of toxic divalent copper. At the same time, compared with the prior art, this invention reduces the residual amount of copper ions in the obtained sulfonium salts by more than 6 times by changing the catalyst, solvent, specific reaction temperature and time, which is beneficial to obtaining high-quality photoresist.

[0041] 3. This invention uses chlorobenzene instead of chloroform, which enables solvent recovery and avoids the use of the toxic solvent chloroform, while also further improving the yield, which is more in line with the concept of green chemistry. When other conventional aromatic solvents are used, the substrate aggregates and cannot react.

[0042] 4. This invention provides a novel method for preparing compound 1. This route is simple to operate, safe to react, and has a short reaction time. It can be scaled up to 30 kg scale for large-scale production, and therefore has good market value and far-reaching practical significance. Detailed Implementation

[0043] The beneficial effects of the present invention will be further described through the following embodiments. It should be understood that these embodiments are for illustrative purposes only and do not limit the scope of the present invention. At the same time, obvious changes and modifications made by those skilled in the art according to the present invention are also included within the scope of the present invention.

[0044] Unless otherwise specified, all raw materials or reagents used in the examples are commercially available.

[0045] In the examples, room temperature refers to 20–30°C. Unless otherwise specified, the reagents are used directly without purification. All solvents were purchased from commercial suppliers, such as Sigma Aldrich, and are ready for use without treatment.

[0046] Example 1: Preparation of Compound 3

[0047]

[0048] Sulfuric acid (4380g) was added to a reactor and mechanically stirred. Acetic acid (3040g) and potassium iodate (4786g) were added at -10 to 10℃. Acetic anhydride (9120g) and compound 2 (2000g) were added dropwise at -10 to 0℃. The reaction was maintained at -10 to 0℃ for 24 hours. After the reaction was completed, deionized water was added dropwise at -10 to 0℃ to quench the reaction. After the addition was complete, the aqueous phase was obtained by filtration. Toluene was added and extracted twice. The organic phases were combined, and deionized water was added and extracted again. The aqueous phases were combined and cooled to 0 to 5℃, and a white solid product precipitated. The product was filtered and dried to obtain 5846g of crude product. This crude product was dissolved in methanol, and dimethyl sulfate (752g) was added dropwise. After the addition was complete, the mixture was heated to reflux for 6 hours. The reaction was confirmed to be complete by NMR. The methanol was removed by vacuum distillation, and tetrahydrofuran was added to dissolve the residue. The mixture was heated to complete dissolution and then cooled to 10℃ to crystallize, yielding 5260g of white solid, with a yield of 70%.

[0049] Example 2: Preparation of Compound 1

[0050]

[0051] Compound 3 (500 g) was dissolved in chlorobenzene (2 L), and compound 4 (108.3 g) and cuprous iodide (5 g) were added sequentially. The mixture was mechanically stirred under nitrogen protection. The oil bath was heated to an internal temperature of 60–65 °C and reacted for 1 h. After the reaction was completed by TLC monitoring, the internal temperature was lowered to 20–25 °C and stirred for 0.5 h. The mixture was filtered to obtain 444 g of a white wet solid. The wet solid was dissolved in methanol (2.5 L) at room temperature, filtered through diatomaceous earth, and the filtrate was concentrated under reduced pressure to obtain a pale yellow wet solid. Methyl tert-butyl ether (2.5 L) was added at room temperature, and the mixture was heated to 45–50 °C and stirred for 1 h. Then the temperature was lowered to 20–25 °C and stirred for 0.5 h. The mixture was filtered to obtain a white wet solid, which was dried at 55–60 °C to obtain 320.6 g of a white solid, with a yield of 97%, HPLC purity of 99.92%, and ICP-MS analysis showing a copper ion content of 361 ppm.

[0052] Comparative Example 1: Preparation of Compound 1

[0053] Compound 3 (250 g) was dissolved in chlorobenzene (1 L), and compound 4 (54.2 g) and copper acetate (2.4 g) were added. The mixture was mechanically stirred under nitrogen protection. The oil bath was heated to an internal temperature of 60–65 °C and reacted for 1 h. After the reaction was completed by TLC monitoring, the internal temperature was lowered to 20–25 °C and stirred for 0.5 h. The mixture was filtered to obtain 184 g of a white wet solid. The wet solid was dissolved in methanol (1 L) at room temperature, filtered through diatomaceous earth, and the filtrate was concentrated under reduced pressure at 45–50 °C to obtain a pale yellow wet solid. Methyl tert-butyl ether (1 L) was added at room temperature, and the mixture was heated to 45–50 °C and stirred for 1 h. Then the temperature was lowered to room temperature and stirred for 0.5 h. The mixture was filtered to obtain a white wet solid. The white solid was dried at 55–60 °C for 24 h, yielding 81.2 g of white solid. The yield was 49%, the HPLC purity was 99.6%, and the copper ion content was 2329 ppm as determined by ICP-MS.

[0054] Comparative Example 2: Preparation of Compound 1

[0055] The comparative sample was prepared according to the method in the prior art JP2017057192A.

[0056] Compound 3 (100 g) was dissolved in chloroform (700 ml), and compound 4 (20.6 g) was added. The mixture was stirred at room temperature for 0.5 h, and then copper acetate (1 g) was added. The mixture was mechanically stirred under nitrogen protection. The oil bath was heated to an internal temperature of 80 °C, and the mixture was refluxed for 2 h. After the reaction was complete as monitored by TLC, the mixture was concentrated at an external temperature of 40–45 °C. Then, 880 ml of methyl tert-butyl ether was added, and the mixture was stirred at room temperature for 0.5 h. The mixture was then filtered and dried at 55–60 °C to obtain 53 g of a white solid product, with a yield of 70%, an HPLC purity of 98%, and an ICP-MS analysis showing a copper ion content of 18501 ppm.

[0057] Comparative Example 3: Preparation of Compound 1

[0058] Compound 3 (100 g) was dissolved in chloroform (700 ml), and compound 4 (20.6 g) was added. The mixture was stirred at room temperature for 0.5 h, and then cuprous iodide (1 g) was added. The mixture was mechanically stirred under nitrogen protection. The oil bath was heated to an internal temperature of 60–65 °C, and the reaction was carried out for 1 h. The reaction was monitored by TLC until it was complete. The mixture was concentrated at an external temperature of 40–45 °C to remove chloroform. 400 ml of methanol was added, and the mixture was dissolved at room temperature. The solution was filtered through a 50 g diatomaceous earth filter. The filtrate was collected and concentrated under reduced pressure at 40–45 °C to remove methanol. 500 ml of methyl ether was added, and the mixture was stirred at room temperature for 2 h. The solution was then filtered to obtain a white solid wet product. The product was dried at 55–60 °C to obtain 53.0 g of a white solid product, with a yield of 80%. The copper ion content was determined to be 400 ppm by ICP-MS.

[0059] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing compound 1, characterized in that, Includes the following steps: Step 1: Compound 3 and Compound 4 react in the presence of cuprous iodide and the organic solvent chlorobenzene to give Compound 1; 2. The preparation method according to claim 1, characterized in that, The molar ratio of compound 3 and cuprous iodide in step 1 is 1:(0.01-0.5).

3. The preparation method according to claim 2, characterized in that, The molar ratio of compound 3 and cuprous iodide in step 1 is 1:(0.01-0.3).

4. The preparation method according to claim 1, characterized in that, In step 1, the reaction temperature is 40–90°C and the reaction time is 0.5–5 h.

5. The preparation method according to claim 4, characterized in that, In step 1, the reaction temperature is 50–80°C and the reaction time is 0.5–4 hours.

6. The preparation method according to claim 1, characterized in that, In step 1, the molar ratio of compound 3 to compound 4 is 1:(1-3).

7. The preparation method according to claim 6, characterized in that, In step 1, the molar ratio of compound 3 to compound 4 is 1:(1-2).

8. The preparation method according to claim 1, characterized in that, Compound 1 was obtained by dissolving compound 3 in chlorobenzene, adding compound 4 and cuprous iodide, heating to 50–70°C, and reacting for 0.5–3 hours.

9. The preparation method according to claim 1, characterized in that, Compound 3 was prepared by the following method: Includes the following steps: Step 2: Compound 2 reacts in the presence of an acidic reagent and iodate to give an intermediate product; Step 3: The intermediate product obtained in Step 2 and dimethyl sulfate react in an organic solvent to obtain compound 3.

10. The preparation method according to claim 9, characterized in that, Step 2 satisfies at least one of the following conditions: The acidic reagent is selected from one or more of sulfuric acid, acetic acid, and acetic anhydride; The iodate is selected from one or more of potassium iodate, lithium iodate, and sodium iodate; The reaction temperature is -20 to 10℃; The reaction time is 12–36 hours; After the reaction was complete, the mixture was quenched with water, filtered, extracted with an organic solvent, the organic phases were combined, deionized water was added for extraction, the aqueous phases were combined, and the temperature was lowered to -5 to 5°C to obtain the intermediate product.

11. The preparation method according to claim 10, characterized in that, Step 2 satisfies at least one of the following conditions: The iodate is potassium iodate; The reaction temperature is -15 to 5℃; The reaction time is 18–30 hours.

12. The preparation method according to claim 9, characterized in that, Step 3 must satisfy at least one of the following conditions: The organic solvent is selected from any one or more of methanol, ethanol, and isopropanol; The reaction time is 2–18 hours; After the reaction is complete, post-treatment is performed, which includes removing the solvent by vacuum evaporation and recrystallizing with an organic solvent.

13. The preparation method according to claim 12, characterized in that, Step 3 must satisfy at least one of the following conditions: The organic solvent is methanol; The reaction time is 2 to 10 hours.

Images