Process for the electrocatalytic preparation of 10-(4-biphenylyl)-2-isopropylthioxanthium hexafluorophosphate

Abstract

The application discloses a method for electrocatalytically preparing 10-(4-biphenyl)-2-isopropyl thioxanthone sulfonium hexafluorophosphate, which uses 2-isopropyl thioxanthone as raw material to electrocatalytically prepare 10-(4-biphenyl)-2-isopropyl thioxanthone sulfonium hexafluorophosphate. In the method, an intermediate sulfoxide is obtained by adopting an anodic oxidation method under an electrocatalytic condition and using water as an oxygen source, thus avoiding the use of an additional oxidant and overcoming the defects of the prior art method, such as the need of an additional oxidant, high cost of production raw material and poor product quality.

Description

Technical Field

[0001] This invention relates to the field of cationic photoinitiator preparation technology, specifically to a method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thioonium hexafluorophosphate. Background Technology

[0002] Cationic photoinitiators have demonstrated unique advantages in the field of photocurable materials, such as oxygen-free polymerization inhibition, low curing shrinkage, and strong adhesion. These properties give them a significant advantage in the cationic polymerization of resins such as epoxy resins, vinyl ethers, alicyclic epoxides, and oxetanes. However, despite these advantages, the post-curing characteristics, high cost, and sensitivity to moisture and alkaline gases limit their widespread application.

[0003] In recent years, the development of onium salt cationic photoinitiators has been rapid, with the continuous emergence of new varieties, greatly expanding the application range of photocurable materials. Structurally, onium salt cationic photoinitiators consist of two parts: anion and cation. The cationic part mainly includes iodonium salts and thiodonium salts. These photoinitiators undergo a transition by absorbing radiation energy, generating a superacid cation capable of initiating polymerization. The weaker the nucleophilicity of the anion, the stronger the acidity of the generated superacid, and thus the higher the initiation efficiency. This characteristic determines the photochemical properties of the photoinitiator, including its maximum absorption wavelength, molar absorptivity, quantum yield, and thermal stability.

[0004] Traditional methods for formulating cationic photocurable coatings widely use triarylsulfonium salt photoinitiators such as UVI699. However, their use is limited by the simple phenyl compounds such as benzene produced after photodecomposition.

[0005] To overcome the above problems, patent application US4882201 uses long-chain substituted phenylthioonium salts, and patent application WO03072567 describes a biphenyl-substituted thioonium salt for food, namely 10-(4-biphenyl)-2-isopropylthioxanthionium hexafluorophosphate, with the structure shown in formula (I). The preparation method described in patent application WO03072567 is the oxidation of 2-isopropylthioxanthone to obtain sulfoxide, the sulfoxide reacting with biphenyl to form a salt to obtain a hydrogen sulfate thioonium salt, which is then subjected to ion exchange with an aqueous solution of potassium hexachlorophosphate in acetic acid to obtain the target product.

[0006]

[0007] Patent application WO03072567 uses cerium ammonium nitrate as an oxidant in the oxidation reaction of thioethers. However, due to the excessive amount of cerium ammonium nitrate used in this technology and its particularly high price, the production cost of the target product is high and it has no industrial value.

[0008] Although patent CN101153037B improved upon the method in patent application WO03072567, it still uses an external oxidant, cerium ammonium nitrate. Japanese patent application JP0240354A uses sodium hypobromite as an oxidant to replace cerium ammonium nitrate in order to oxidize sulfur to prepare sulfoxide, but it still cannot avoid the use of an external oxidant.

[0009] Therefore, there is an urgent need to develop a method for preparing 10-(4-biphenyl)-2-isopropylthioxanthionium hexafluorophosphate, which can overcome the problems of existing technologies such as the need for external oxidants, high raw material costs, and poor product quality, thereby expanding the application range of onium salt cationic photoinitiators. Summary of the Invention

[0010] The purpose of this invention is to provide a method for preparing 10-(4-biphenyl)-2-isopropylthioxanthionium hexafluorophosphate from 2-isopropylthioxanthione as a raw material. This method involves electro-oxidizing 2-isopropylthioxanthione to obtain the intermediate sulfoxide, which is then reacted with biphenyl to form a salt, yielding trifluoromethanesulfonium sulfonium salt. Finally, the salt is ion-exchanged with an aqueous solution of potassium hexafluorophosphate to obtain the target product. This method overcomes the disadvantages of existing methods, such as the need for an external oxidant, high raw material costs, and poor product quality.

[0011] To achieve the above-mentioned objective, this invention provides a method for the electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thionium hexafluorophosphate, comprising the following steps:

[0012] Step (1): Add 2-isopropylthioxanthone and electrolyte to an aqueous alcohol solvent, insert the cathode and anode electrodes for electrocatalysis, and use water as an oxygen source to anolyte the intermediate sulfoxide.

[0013] Step (2): Dissolve intermediate sulfoxide and biphenyl in an organic solvent, and add trifluoromethanesulfonic acid dropwise to the organic solvent to carry out a salt formation reaction to obtain compound (II) 10-(4-biphenyl)-2-isopropylthioxanthionyl thionyl trifluoromethanesulfonate;

[0014] Step (3): Dissolve compound (II) in an alcohol solvent, add potassium hexafluorophosphate aqueous solution dropwise to the alcohol solvent, and collect the precipitated solid particles to obtain compound (I);

[0015]

[0016] In step (2) of this invention, the organic solvent can be an organic solvent such as dichloromethane.

[0017] According to the present invention, in a method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thionyl hexafluorophosphate, preferably, in step (1), the electrolyte is any one or more of lithium perchlorate, tetrabutylammonium bromide, tetrabutylammonium iodide, and tetrabutylammonium hexafluorophosphate.

[0018] According to the method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionium hexafluorophosphate according to the present invention, preferably, in steps (1) and (2), the molar ratio of 2-isopropylthioxanthion, trifluoromethanesulfonic acid and biphenyl is 1:1 to 6:1 to 3.

[0019] According to the present invention, in the method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thionyl hexafluorophosphate, preferably, in step (1), the aqueous alcohol solvent is an aqueous solution of trifluoroethanol or an aqueous solution of hexafluoroisopropanol, and the mass percentage concentration of the aqueous alcohol solvent is 95%-98%.

[0020] According to the present invention, in a method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionone thionyl hexafluorophosphate, preferably, in step (1), the weight-to-volume ratio of 2-isopropylthioxanthionone to aqueous alcohol solvent is 1:50-100 g / mL.

[0021] According to the present invention, in the method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thionyl hexafluorophosphate, preferably, in step (1), the anode is any one of a graphite electrode, a PVC electrode, or a PtO2 electrode; and the cathode is any one of a graphite electrode, a platinum electrode, a nickel electrode, or a silver electrode.

[0022] According to the method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thionyl hexafluorophosphate according to the present invention, preferably, in step (1), the current is 10-50 mA and the current density is 2.0-5.0 mA / cm². 2 .

[0023] According to the method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thionyl hexafluorophosphate according to the present invention, preferably, in step (2), the process of adding trifluoromethanesulfonic acid and the salt formation reaction are both carried out below 15°C.

[0024] According to the present invention, in the method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thioonium hexafluorophosphate, preferably, in step (3), the alcohol solvent can be methanol or ethanol.

[0025] According to the present invention, in the method for electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thionyl hexafluorophosphate, preferably, in step (3), the amount of alcohol solvent used is 30-60% (V / V) of potassium hexafluorophosphate aqueous solution.

[0026] The beneficial effects of this invention are:

[0027] This invention provides a method for preparing 10-(4-biphenyl)-2-isopropylthioxanthionone thioonium hexafluorophosphate from 2-isopropylthioxanthionone. The method involves electro-oxidizing 2-isopropylthioxanthionone to obtain the intermediate sulfoxide, which is then reacted with biphenyl to form a salt to obtain trifluoromethanesulfonium thioonium salt. Finally, the salt is ion-exchanged with an aqueous solution of potassium hexafluorophosphate to obtain the target product.

[0028] The method of the present invention uses anodizing under electrocatalytic conditions and water as an oxygen source to obtain the intermediate sulfoxide during the oxidation process, avoiding the use of external oxidants. In addition, the method of adding an aqueous solution of potassium hexafluorophosphate dropwise to the alcohol solution of the intermediate during the ion exchange reaction overcomes the disadvantages of existing methods, such as the need for external oxidants, high raw material costs, and poor product quality. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples.

[0030] Example 1

[0031] This embodiment provides a method for the electrocatalytic preparation of 10-(4-biphenyl)-2-isopropylthioxanthionyl thioonium hexafluorophosphate, comprising the following steps:

[0032] Step (1): Add 508 g of 2-isopropylthioxanthone (2 mol, 1.0 equivalent), 424 g of lithium perchlorate (4 mol, 2 equivalent), and 30 L of 2,2,2-trifluoroethanol aqueous solution (98% by mass) to a 50 ml reaction flask. Insert the cap with the anode (graphite electrode) and cathode (platinum electrode) into the mixture and apply a constant current of 10 mA (j = 2.5 mA / cm²) at room temperature. 2 Electrolysis was carried out for 5 hours. After electrolysis, the anode electrode was rinsed with dichloromethane, the solvent was removed under vacuum, the residue was washed with diethyl ether, and dried under vacuum to obtain 491 g of isopropylthioxanthone sulfoxide, a light yellow solid, with a yield of 91%. Melting point: 200-201℃.

[0033] 1H NMR (400MHz, CDCl3): δ8.29 (d, J = 7.6Hz, 2H), 8.14 (d, J = 7.60Hz, 2H), 7.96 (t, J = 7.6Hz, 2H), 7.88 (t, J = 6.8Hz, 2H); 13 C NMR (100MHz, CDCl3) δ177.4,139.9,134.2,132.7,129.6,128.0,122.2. HRMS(ESI-TOF)(m / z):calcd for C 15 H 12 O2S + ([M + H] + ),256.0553,found,256.0540.

[0034] Step (2): Isopropylthioxanthone sulfoxide (41g, 0.15mol, 1 equivalent), biphenyl (52g, 0.17mol, 1.1 equivalent) and 18mL of dichloromethane were added to a 500ml four-necked flask and stirred to dissolve. Then, the mixture was placed in a low-temperature bath to cool to below 15℃. 50mL of trifluoromethanesulfonic acid was added dropwise, keeping the temperature of the reaction solution below 15℃. After the addition was complete, the mixture was stirred at 15℃ for 2 hours. The reaction solution was then transferred to a 2.5L reaction flask, and 1L of water and 1L of dichloromethane were added. After stirring for 30 minutes, the mixture was placed in a separatory funnel to separate the layers. The lower layer of dichloromethane solution was collected and evaporated to dryness using a rotary evaporator to obtain 10-(4-biphenyl)-2-isopropylthioxanthone-10-thionyltrifluoromethanesulfonate.

[0035] Step (3): Dissolve 10-(4-biphenyl)-2-isopropylthioxanthionone-10-thionium trifluoromethane sulfonate obtained in step (2) in 300 mL of methanol, and add 500 mL of aqueous solution containing 28 g of potassium hexafluorophosphate (0.152 mol) dropwise to the methanol solution. After the addition is complete, continue stirring for 5 h, collect the precipitated powdery solid, filter, wash with water and dry to obtain 10-(4-biphenyl)-2-isopropylthioxanthionone-10-thionium hexafluorophosphate, 68 g of yellow solid product, yield 89%, melting point: 183-190℃.

[0036] 1 H NMR(CDCl3): δ8.67-8.65(m,1H),8.51-8.50(d,1H),8.21-8.18(m,1H),8.13-8.11( m,1H),7.86-7.74(m,6H),7.71-7.42(m,6H),3.19-3.12(m,1H),1.28-1.27(m,6H).

[0037] Example 2

[0038] Except for step (1), the method of Example 2 is the same as that of Example 1. Step (1) of Example 2 is as follows:

[0039] Step (1): Add 508 g of 2-isopropylthioxanthone (2 mol, 1.0 equivalent), 1.29 kg of tetrabutylammonium bromide (4 mol, 2 equivalent), and 30 L of hexafluoroisopropanol (97% by mass) to a 50 ml reaction flask. Insert the cap with the anode (graphite electrode) and cathode (graphite electrode) into the mixture and apply a constant current of 30 mA (j = 3.3 mA / cm) at room temperature. 2 Electrolysis was carried out for 2 hours. After electrolysis, the anode electrode was rinsed with dichloromethane, the solvent was removed under vacuum, the residue was washed with diethyl ether, and dried under vacuum to obtain 513 g of isopropylthioxanone sulfoxide, a light yellow solid, with a yield of 95%.

[0040] Example 3

[0041] Except for step (1), the method in Example 3 is the same as that in Example 1. Step (1) of Example 3 is as follows:

[0042] Step (1): Add 2-isopropylthioxanthone (508 g, 2 mol, 1.0 equivalent), tetrabutylammonium hexafluorophosphate (1.55 kg, 4 mol, 2 equivalent), and 2,2,2-trifluoroethanol (30 L, 95% by mass) to a 50 ml reaction flask. Insert the cap with the anode (PVC electrode) and cathode (nickel electrode) into the mixture and apply a constant current of 50 mA (j = 3.3 mA / cm) at room temperature. 2 Electrolysis was carried out for 2 hours. After electrolysis, the anode electrode was rinsed with dichloromethane, the solvent was removed under vacuum, the residue was washed with diethyl ether, and dried under vacuum to obtain 502 g of isopropylthioxanone sulfoxide, a light yellow solid, with a yield of 93%.

[0043] Comparative example:

[0044] The method mentioned in Example 1 of patent CN101153037B is as follows:

[0045] In a 1L four-necked flask, add 60.0g (0.24mol) of 2-isopropylthioxanthone, 450mL of acetic acid, 100mL of water, 18.0g of cerium ammonium nitrate (0.0328mol), and 10.0g of 48% hydrobromic acid solution. After stirring until homogeneous, maintain the temperature at 25–30℃. Add 200g (0.24mol) of 10% sodium hypochlorite solution dropwise through a dropping funnel and stir for 24 hours. Add 400mL of water to the reaction mixture, stir for 1 hour, filter, wash the filter cake with 100mol of water, and dry to obtain 54g of light yellow isopropylthioxanthone sulfoxide, with a yield of 88%.

[0046] Comparative analysis shows that, using the method of this invention, the yield of the intermediate isopropylthioxanthone sulfoxide is increased from 88% to over 91%, even reaching 95%, without the use of an external oxidant, demonstrating a significant improvement in yield. Therefore, this invention overcomes the shortcomings of existing methods, such as the need for an external oxidant, high raw material costs, and poor product quality, and possesses significant advantages.

[0047] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for the electrocatalytic preparation of 10-(4-biphenylyl)-2- isopropylthioxanthium hexafluorophosphate, characterized in that, The method comprises the following steps: Step (1): 2-isopropylthioxanthone, electrolyte are added into an aqueous alcohol solvent, and electrocatalysis is carried out by inserting a cathode and an anode, so that an intermediate sulfoxide is obtained by oxidation at the anode with water as an oxygen source; Step (2): the intermediate sulfoxide and biphenyl are dissolved in an organic solvent, and trifluoromethanesulfonic acid is added dropwise into the organic solvent to carry out a salt formation reaction, so that a compound of formula (II) 10-(4-biphenyl)-2-isopropylthioxanthone sulfonium trifluoromethanesulfonate is obtained; Step (3): the compound of formula (II) is dissolved in an alcohol solvent, and an aqueous solution of potassium hexafluorophosphate is added dropwise into the alcohol solvent, and the precipitated solid particles are collected, so that a compound of formula (I) is obtained; ; wherein, in step (1), the current is 10-50 mA and the current density is 2.0-5.0 mA / cm 2 , the aqueous alcohol solvent is a solution of trifluoroethanol or hexafluoroisopropanol in water, and the mass percentage concentration of the aqueous alcohol solvent is 95%-98%.

2. A method of electrocatalytic preparation of 10-(4-biphenyl)-2- isopropylthioxanthium hexafluorophosphate according to claim 1, characterized in that, In step (1), the electrolyte is any one or more of lithium perchlorate, tetrabutylammonium bromide, tetrabutylammonium iodide, and tetrabutylammonium hexafluorophosphate.

3. A method of electrocatalytic preparation of 10-(4-biphenyl)-2- isopropylthioxanthium hexafluorophosphate according to claim 1, characterized in that, In steps (1) and (2), the molar ratio of 2-isopropylthioxanthone, trifluoromethanesulfonic acid, and biphenyl is 1:1-6:1-3.

4. A method of electrocatalytic preparation of 10-(4-biphenyl)-2- isopropylthioxanthium hexafluorophosphate according to claim 3, characterized in that, In step (1), the aqueous alcohol solvent is a trifluoroethanol aqueous solution or a hexafluoroisopropanol aqueous solution, and the mass percentage concentration of the aqueous alcohol solvent is 95-98%.

5. A method of electrocatalytic preparation of 10-(4-biphenyl)-2- isopropylthioxanthium hexafluorophosphate according to claim 4, characterized in that, In step (1), the weight-to-volume ratio of 2-isopropylthioxanthone to the aqueous alcohol solvent is 1:50-100 g / mL.

6. A method of electrocatalytic preparation of 10-(4-biphenyl)-2- isopropylthioxanthium hexafluorophosphate according to claim 3, characterized in that, In step (1), the anode is any one of a graphite electrode, a PVC electrode, and a PtO2 electrode; and the cathode is any one of a graphite electrode, a platinum electrode, a nickel electrode, and a silver electrode.

7. A method of electrocatalytic preparation of 10-(4-biphenyl)-2- isopropylthioxanthium hexafluorophosphate according to claim 6, characterized in that, In the step (1), the current is 10-50 mA, and the current density is 2.0-5.0 mA / cm 2 .

8. A method of electrocatalytic preparation of 10-(4-biphenyl)-2- isopropylthioxanthium hexafluorophosphate according to claim 1, characterized in that, In step (2), the process of adding trifluoromethanesulfonic acid dropwise and the salt formation reaction are both carried out below 15℃.

9. The method of electrocatalytic preparation of 10-(4-biphenyl)-2- isopropylthioxanthium hexafluorophosphate according to claim 1, characterized by that, In step (3), the alcohol solvent is methanol or ethanol.

10. A method of electrocatalytic preparation of 10-(4-biphenyl)-2- isopropylthioxanthium hexafluorophosphate according to claim 9, characterized in that, In step (3), the amount of the alcohol solvent is 30-60% of the volume of the aqueous solution of potassium hexafluorophosphate.

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