Process for the preparation of p-acetoxystyrene

Abstract

This invention discloses a method for preparing p-acetoxystyrene, comprising the following steps: mixing [4-(1-hydroxyethyl)phenyl]acetate, organophosphoric acid, and a polymerization inhibitor, and reacting them thoroughly to obtain the desired p-hydroxystyrene. The method of this invention utilizes organophosphoric acid as a catalyst for the dehydration reaction of [4-(1-hydroxyethyl)phenyl]acetate, thus achieving the preparation of p-acetoxystyrene. Compared with traditional methods for preparing p-acetoxystyrene, this method does not require large amounts of acidic and alkaline dehydrating agents, generates less wastewater, and the organophosphoric acid catalyst can be recycled. Therefore, the method of this invention for preparing p-acetoxystyrene has advantages such as low waste, high yield, and environmental friendliness, and thus has good application value.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis, and in particular to a method for preparing p-acetoxystyrene. Background Technology

[0002] Polymers of p-hydroxystyrene (PHS) and its derivatives are widely used in solid-phase synthesis, phase-transfer catalysis, selective permeation membranes, epoxy resin curing agents, free radical scavengers and antioxidants, and photoresists (also known as photoresists). 248nm deep ultraviolet photoresist is currently the mainstream photoresist product internationally and is one of the key materials for photolithography of integrated circuits and chip manufacturing. P-acetoxystyrene is the core monomer of the main film-forming resin material in 248nm photoresist; therefore, optimizing the synthesis method and process conditions of p-acetoxystyrene is of great value.

[0003] Currently, the most important method in the synthesis of p-hydroxystyrene is the dehydration of [4-(1-hydroxyethyl)phenyl]acetate under certain conditions.

[0004]

[0005] In 1958, Corson et al. reported a dehydration method using potassium bisulfate or activated alumina as a dehydrating agent and p-tert-butylcatechol as a polymerization inhibitor (J. Org. Chem. 1958, 23, 544). Hearst Celanese reported an improved process of the above method in US5151546A and US5245074A, carrying out the dehydration reaction continuously or semi-continuously in a thin-film evaporator. Meanwhile, US5041614A reported a method using phosphoric acid as a dehydrating agent. CN102795999A disclosed a method for synthesizing acetoxystyrene from [4-(1-hydroxyethyl)phenyl]acetate using hydrochloric acid, sulfuric acid, phosphorus trichloride, etc., as dehydrating agents. CN110655462A disclosed a synthesis method using an alkaline acid-binding agent as a dehydrating agent. Patent CN111087303A discloses a synthesis method using solid acid as a dehydrating agent, which yields p-acetoxystyrene via a one-pot cooking method in the presence of a polymerization inhibitor.

[0006] However, the traditional methods for preparing p-hydroxystyrene by dehydrating [4-(1-hydroxyethyl)phenyl]acetate all require large amounts of acidic and alkaline dehydrating agents, often generating a lot of wastewater and having poor environmental friendliness. Summary of the Invention

[0007] Therefore, it is necessary to provide a method for preparing p-acetoxystyrene that can solve the above problems.

[0008] A method for preparing p-acetoxystyrene includes the following steps:

[0009] [4-(1-hydroxyethyl)phenyl]acetate, organophosphate, and polymerization inhibitor are mixed and reacted thoroughly to obtain the desired p-hydroxystyrene. The reaction formula is as follows:

[0010]

[0011] In one embodiment, the organophosphate is a compound having the following structural formula I or structural formula II:

[0012]

[0013] Wherein, R is H, phenyl, trifluoromethyl-substituted phenyl, di-trifluoromethyl-substituted phenyl, halogen-substituted phenyl, methyl-substituted phenyl, or dimethyl-substituted phenyl.

[0014] In one embodiment, the organophosphate is one of a compound having the following structural formula:

[0015]

[0016] In one embodiment, the molar ratio of the organophosphate and the p-[4-(1-hydroxyethyl)phenyl]acetate is 0.05 to 0.5:100.

[0017] In one embodiment, the molar ratio of the organophosphate and the p-[4-(1-hydroxyethyl)phenyl]acetate is 0.1:100.

[0018] In one embodiment, the method further includes recovering the organophosphate in the reactants after the operation of obtaining p-hydroxystyrene.

[0019] In one embodiment, the operation of recovering the organophosphoric acid from the reactants is as follows: the reactants are subjected to vacuum distillation to remove the p-acetoxystyrene. The distillate residue and water are then thoroughly mixed at a volume ratio of 0.5 to 5:10, and the pH is adjusted to 14. A first aqueous phase and a first organic phase are then separated. The pH of the first aqueous phase is adjusted to 3, and ethyl acetate is added to the first aqueous phase for extraction. After extraction, a second aqueous phase and a second organic phase are separated again. A desiccant is added to the second organic phase, and the organophosphoric acid is recovered after vacuum concentration.

[0020] In one embodiment, the polymerization inhibitor is p-tert-butylcatechol, and the molar ratio of the polymerization inhibitor to p-[4-(1-hydroxyethyl)phenyl]acetate is 0.05 to 2:100.

[0021] In one embodiment, during the process of fully reacting the mixture of [4-(1-hydroxyethyl)phenyl]acetate, organophosphate, and polymerization inhibitor, the reaction temperature is 80°C to 100°C, and the reaction time is 1 hour to 3 hours.

[0022] In one embodiment, the molar ratio of the polymerization inhibitor to the p-[4-(1-hydroxyethyl)phenyl]acetate is 1:100;

[0023] The method for preparing p-acetoxystyrene of the present invention achieves the preparation of p-acetoxystyrene by using organic phosphoric acid as a catalyst for the dehydration reaction of [4-(1-hydroxyethyl)phenyl]acetate.

[0024] Compared with traditional methods for preparing p-acetoxystyrene, the method of the present invention does not require the use of large amounts of acidic and alkaline dehydrating agents, generates less wastewater, and the organophosphoric acid catalyst can be recycled.

[0025] Therefore, the preparation method of p-acetoxystyrene of the present invention has the advantages of less waste, high yield, and green and clean operation, and thus has good application value. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. 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.

[0027] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0028] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" and "second" may explicitly or implicitly include at least one of the stated features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0029] This invention discloses a method for preparing p-acetoxystyrene according to one embodiment, comprising the following steps:

[0030] [4-(1-hydroxyethyl)phenyl]acetic acid, organophosphate, and polymerization inhibitor are mixed and reacted thoroughly to obtain the desired p-hydroxystyrene.

[0031] The reaction equations for the above reactions are as follows:

[0032]

[0033] The method for preparing p-acetoxystyrene of the present invention achieves the preparation of p-acetoxystyrene by using organic phosphoric acid as a catalyst for the dehydration reaction of [4-(1-hydroxyethyl)phenyl]acetate.

[0034] Compared with traditional methods for preparing p-acetoxystyrene, the method of the present invention does not require the use of large amounts of acidic and alkaline dehydrating agents, generates less wastewater, and the organophosphoric acid catalyst can be recycled.

[0035] Therefore, the preparation method of p-acetoxystyrene of the present invention has the advantages of less waste, high yield, and green and clean operation, and thus has good application value.

[0036] Preferably, the organophosphate is a compound having the following structural formula I or structural formula II:

[0037]

[0038] Wherein, R is H, phenyl, trifluoromethyl-substituted phenyl, di-trifluoromethyl-substituted phenyl, halogen-substituted phenyl, methyl-substituted phenyl, or dimethyl-substituted phenyl.

[0039] Specifically, in this embodiment, the organophosphate is one of the compounds having the following structural formula:

[0040]

[0041] Preferably, in this embodiment, the molar ratio of organophosphate and [4-(1-hydroxyethyl)phenyl]acetate is 0.05 to 0.5:100.

[0042] More preferably, in this embodiment, the molar ratio of organophosphate and [4-(1-hydroxyethyl)phenyl]acetate is 0.1:100.

[0043] In this embodiment, during the process of fully reacting the mixture of [4-(1-hydroxyethyl)phenyl]acetate, organophosphate, and polymerization inhibitor, an organic solvent may or may not be added.

[0044] Specifically, the organic solvent can be toluene.

[0045] Preferably, this embodiment further includes a step of recovering the organophosphate in the reactants after obtaining p-hydroxystyrene.

[0046] Specifically, the operation for recovering organophosphoric acid from the reactants is as follows: the reactants are subjected to vacuum distillation to remove p-acetoxystyrene. The distillate residue is then thoroughly mixed with water at a volume ratio of 0.5–5:10, and the pH is adjusted to 14. The first aqueous phase and the first organic phase are then separated. The pH of the first aqueous phase is adjusted to 3, and ethyl acetate is added to the first aqueous phase for extraction. After extraction, the second aqueous phase and the second organic phase are separated again. A drying agent is added to the second organic phase, and the organophosphoric acid is recovered after vacuum concentration.

[0047] pH can be adjusted using NaOH and HCl solutions, and anhydrous sodium sulfate can be used as a drying agent.

[0048] Preferably, in this embodiment, the polymerization inhibitor is p-tert-butylcatechol, and the molar ratio of the polymerization inhibitor to [4-(1-hydroxyethyl)phenyl]acetate is 0.05 to 2:100.

[0049] More preferably, in this embodiment, the molar ratio of the polymerization inhibitor to [4-(1-hydroxyethyl)phenyl]acetate is 1:100.

[0050] Preferably, in this embodiment, during the process of fully reacting the [4-(1-hydroxyethyl)phenyl]acetate, organophosphoric acid, and polymerization inhibitor, the reaction temperature is 80°C to reflux temperature, and the reaction time is 1h to 3h.

[0051] More preferably, in this embodiment, during the reflux reaction of [4-(1-hydroxyethyl)phenyl]acetate, organophosphoric acid and polymerization inhibitor, the reaction temperature is 90°C to 110°C.

[0052] In a particularly preferred embodiment, during the reflux reaction of [4-(1-hydroxyethyl)phenyl]acetate, organophosphoric acid, and polymerization inhibitor, the reaction temperature is 90°C and the reaction time is 2 hours.

[0053] The following are specific examples.

[0054] In a specific embodiment, [4-(1-hydroxyethyl)phenyl]acetate was prepared from 4-hydroxyacetophenone using a method described in the literature (J. Org. Chem. 2003, 68, 9340–9347). 4-hydroxyacetophenone, organophosphates A1–A6, p-tert-butylcatechol, dibromomethane, deuterated chloroform, and ethyl acetate were all purchased from Shanghai Titan Technology Co., Ltd.

[0055] Example 1

[0056] 180 mg (1 mmol) of [4-(1-hydroxyethyl)phenyl]acetate, 0.2 mg of p-tert-butylcatechol and 0.1 mol% of organophosphoric acid were mixed and catalytically reacted at 90 °C for 3 hours to obtain the reactant.

[0057] The above operations were divided into 6 groups, with different organic phosphoric acids A1 to A6 added to each group.

[0058] After the reactants were concentrated under reduced pressure, dibromomethane was added as an internal standard and deuterated chloroform was used as a solvent. The reaction yields under different conditions were calculated by 1H NMR and the results are shown in Table 1 below.

[0059] Table 1

[0060]

[0061]

[0062] Example 2

[0063] In a three-necked flask, 18 g (0.1 mol) of [4-(1-hydroxyethyl)phenyl]acetate, 34.8 mg of naphthol phosphate (organophosphate A2), and 16.6 mg of p-tert-butylcatechol were added. The mixture was stirred at 90 °C for 2 hours to obtain the reactants. The reactants were then distilled under reduced pressure to give 14.2 g of the product, with a yield of 88%.

[0064] The obtained product was analyzed by 1H NMR. The results are as follows: 1H NMR (400MHz, CDCl3) δ 7.50-7.40 (m, 2H), 7.17-7.05 (m, 2H), 6.80-6.65 (m, 1H), 5.76 (dd, J = 17.7, 2.7Hz, 1H), 5.29 (dd, J = 11.2, 2.6Hz, 1H), 2.31 (s, 3H).

[0065] Based on the above 1H NMR spectroscopy results, it can be confirmed that the prepared product is p-acetoxystyrene.

[0066] Add 5 mL of water to the above distillation residue, adjust the pH to 14 with 0.1 N NaOH aqueous solution, separate the aqueous phase using a separatory funnel, wash the organic phase again with 5 mL of water, and continue to separate the aqueous phase. Combine the two aqueous phases, add 1 N HCl aqueous solution dropwise until the pH reaches 3. Extract three times with 3 mL of ethyl acetate, combine the organic phases, dry with anhydrous sodium sulfate, concentrate under reduced pressure, and recover 29.0 mg of organophosphate A2 catalyst.

[0067] Example 3

[0068] In a three-necked flask, 18 g (0.1 mol) of [4-(1-hydroxyethyl)phenyl]acetate, 29.0 mg of the organophosphate A2 catalyst recovered in Example 2, and 16.6 mg of p-tert-butylcatechol were added. The mixture was stirred at 90 °C for 3 hours to obtain the reactant. The reactant was then distilled under reduced pressure to give 12.5 g of p-acetoxystyrene, with a yield of 77%.

[0069] Characterized by 1H NMR spectroscopy, the product obtained was p-acetoxystyrene.

[0070] 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 patent application. 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 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 method for preparing p-acetoxystyrene, characterized in that, Includes the following steps: [4-(1-hydroxyethyl)phenyl]acetate, organophosphate, and polymerization inhibitor are mixed and reacted thoroughly to obtain the desired p-hydroxystyrene. The reaction formula is as follows: ； The organophosphate is a compound having the following structural formula I or structural formula II: ； Wherein, R is H, phenyl, trifluoromethyl-substituted phenyl, di-trifluoromethyl-substituted phenyl, halogen-substituted phenyl, methyl-substituted phenyl, or dimethyl-substituted phenyl.

2. The method for preparing p-acetoxystyrene according to claim 1, characterized in that, The organic phosphoric acid is one of the compounds having the following structural formula: 。 3. The method for preparing p-acetoxystyrene according to claim 2, characterized in that, The molar ratio of the organic phosphoric acid and the [4-(1-hydroxyethyl)phenyl]acetate is 0.05~0.5:

100.

4. The method for preparing p-acetoxystyrene according to claim 3, characterized in that, The molar ratio of the organic phosphoric acid and the [4-(1-hydroxyethyl)phenyl]acetic acid ester is 0.1:

100.

5. The method for preparing p-acetoxystyrene according to claim 3, characterized in that, It also includes the operation of recovering the organophosphate from the reactants after the operation of obtaining p-hydroxystyrene.

6. The method for preparing p-acetoxystyrene according to claim 5, characterized in that, The operation for recovering the organophosphoric acid from the reactants is as follows: the reactants are subjected to vacuum distillation to remove the p-acetoxystyrene. The distillate residue is then thoroughly mixed with water at a volume ratio of 0.5 to 5:10, and the pH is adjusted to 14. The first aqueous phase and the first organic phase are then separated. The pH of the first aqueous phase is adjusted to 3, and ethyl acetate is added to the first aqueous phase for extraction. After extraction, the second aqueous phase and the second organic phase are separated again. A drying agent is added to the second organic phase, and the organophosphoric acid is recovered after vacuum concentration.

7. The method for preparing p-acetoxystyrene according to any one of claims 1 to 6, characterized in that, The polymerization inhibitor is p-tert-butylcatechol, and the molar ratio of the polymerization inhibitor to the [4-(1-hydroxyethyl)phenyl]acetate is 0.05~2:

100.

8. The method for preparing p-acetoxystyrene according to claim 7, characterized in that, In the operation of fully reacting the mixture of [4-(1-hydroxyethyl)phenyl]acetate, organophosphate and polymerization inhibitor, the reaction temperature is 80℃~100℃ and the reaction time is 1h~3h.

9. The method for preparing p-acetoxystyrene according to claim 8, characterized in that, The molar ratio of the polymerization inhibitor to the [4-(1-hydroxyethyl)phenyl]acetic acid ester is 1:100.

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