Process for producing bis-hydroxybenzoic acid ester compound

Abstract

To provide a production method that can give a bis-hydroxybenzoic acid ester compound at high yield.SOLUTION: The present invention provides a method for producing a bis-hydroxybenzoic acid ester compound represented by formula (2) [where Ar denotes a divalent aromatic group, as with Ar in formula (1) below], including the step of reacting, in the presence of mesitylene and an acid catalyst, a diol represented by formula (1) [where Ar denotes an optionally substituted divalent aromatic group] with 4-hydroxy benzoic acid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a bis(hydroxybenzoic acid) ester compound.

Background Art

[0002] The bis(hydroxybenzoic acid) ester compound is a diester of diols and hydroxybenzoic acid, and is known to be used as a constituent unit of curable resins (Patent Documents 1 and 2), polyarylate (Patent Document 3), liquid crystal polymer (Patent Document 4), etc.

[0003] As methods for producing the bis(hydroxybenzoic acid) ester compound, an acid chloride method, a carbodiimide method, an acid catalyst method, etc. are known. As the acid catalyst method, for example, a method of reacting hydroxybenzoic acid and diols in a xylene solvent in the presence of an acid catalyst is simple and common (Patent Documents 1 to 3).

[0004] However, in industrial-scale production, further improvement in the production rate has been demanded.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a production method by which a bis(hydroxybenzoic acid) ester compound can be obtained in a high yield.

Means for Solving the Problems

[0007] In view of the above problems, the present inventors conducted intensive studies. As a result, they found that in the reaction of diols and hydroxybenzoic acid, by carrying out the reaction in a mesitylene solvent, a bis-hydroxybenzoic acid ester compound can be obtained at a high production rate, and thus completed the present invention.

[0008] That is, the present invention includes the following preferred embodiments. 〔1〕A process for reacting a diol represented by the formula (1) TIFF0007715386000001.tif1066 [wherein, Ar represents a divalent aromatic group which may have a substituent] with 4-hydroxybenzoic acid in the presence of mesitylene and an acid catalyst, the method for producing a bis-hydroxybenzoic acid ester compound represented by the formula (2) TIFF0007715386000002.tif34110 [wherein, Ar represents the same divalent aromatic group as Ar in the formula (1)] 〔2〕The method according to 〔1〕, wherein Ar is a group represented by any of the following formulas (a) to (c) TIFF0007715386000003.tif27135 [wherein, "※" each indicates a bonding position] 〔3〕The method according to 〔2〕, wherein Ar is a group represented by the formula (a). 〔4〕The method according to 〔2〕, wherein Ar is a group represented by the formula (b). 〔5〕The method according to 〔2〕, wherein Ar is a group represented by the formula (c). 〔6〕The method according to any one of 〔1〕 to 〔5〕, wherein the amount of mesitylene used is 100 to 3000 parts by mass with respect to 100 parts by mass of the diol represented by the formula (1). 〔7〕The method according to any one of 〔1〕 to 〔6〕, wherein 1 to 3 moles of 4-hydroxybenzoic acid is reacted with 1 mole of the diol represented by the formula (1). ​​〔8〕The method according to any one of 〔1〕~〔7〕, wherein 0.1 to 50 parts by mass of an acid catalyst is present with respect to 100 parts by mass of the diol represented by the formula (1). 〔9〕The method according to any one of 〔1〕~〔8〕, wherein the acid catalyst is p-toluenesulfonic acid. 〔10〕The method according to any one of 〔1〕~〔9〕, wherein the diol represented by the formula (1) and 4-hydroxybenzoic acid are reacted at a temperature of 80 to 200 °C. 〔11〕The method according to any one of 〔1〕~〔10〕, wherein the step is a step of obtaining a crude composition containing the bis(hydroxybenzoic acid ester) compound represented by the formula (2). 〔12〕The method according to 〔11〕, including a step of suspending and washing the crude composition with a suspension washing solvent. 〔13〕The method according to 〔12〕, wherein the suspension washing solvent contains N,N-dimethylformamide. 〔14〕In the formula (1) and the formula (2), Ar is the following formula (a) The method according to 〔13〕, which is a group represented by TIFF0007715386000004.tif3155. 〔15〕The method according to 〔12〕, wherein the suspension washing solvent contains toluene. 〔16〕In the formula (1) and the formula (2), Ar is the following formula (c) The method according to 〔15〕, which is a group represented by TIFF0007715386000005.tif3443. 〔17〕The method according to 〔11〕, including a step of recrystallizing the crude composition with a recrystallization solvent. 〔18〕The method according to 〔17〕, wherein the recrystallization solvent contains N,N-dimethylformamide. 〔19〕In the formula (1) and the formula (2), Ar is the following formula (b) The method according to 〔18〕, which is a group represented by TIFF0007715386000006.tif2748.

Advantages of the Invention

[0009] According to the present invention, a bis(hydroxybenzoic acid ester) compound can be obtained at a high production rate.

BEST MODE FOR CARRYING OUT THE INVENTION

[0010] In the present invention, the diol and 4-hydroxybenzoic acid used as reaction raw materials may be commercially available ones, or those produced by methods known to those skilled in the art may also be used.

[0011] The diol used in the present invention has the formula (1): TIFF0007715386000007.tif1066[wherein, Ar represents a divalent aromatic group which may have a substituent] and is a diol represented by the formula.

[0012] Specific examples thereof include 4,4'-dihydroxybiphenyl, hydroquinone, 2-methylhydroquinone, 2-methyl-4,4'-dihydroxybiphenyl, 2,3-dimethylhydroquinone, 2,5-dimethylhydroquinone, 2,6-dimethylhydroquinone, 2,3,5-trimethylhydroquinone, 2-ethylhydroquinone, 2,3-diethylhydroquinone, 2,5-diethylhydroquinone, 2,6-diethylhydroquinone, 2,3,5-triethylhydroquinone, 2-tert-butylhydroquinone, 2,3-di-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butylhydroquinone, 2,3,5-tri-tert-butylhydroquinone, 2-chloro-hydroquinone, 2,3-dichloro-hydroquinone, 2,5-dichloro-hydroquinone, 2,3,5-trichloro-hydroquinone, 2-methoxyhydroquinone and the like. Among them, from the viewpoint of easy availability, one or more selected from the group consisting of 4,4'-dihydroxybiphenyl, hydroquinone and 2-methylhydroquinone are preferable.

[0013] The 4-hydroxybenzoic acid used in the present invention is preferably reacted in an amount of 1 to 3 moles, more preferably 1.2 to 2.8 moles, still more preferably 1.5 to 2.5 moles, and particularly preferably 1.8 to 2.2 moles, per 1 mole of the diol represented by the formula (1).

[0014] When the amount of 4-hydroxybenzoic acid exceeds 3 moles per 1 mole of the diol represented by the formula (1), an excess amount of 4-hydroxybenzoic acid remains, and the bis-hydroxybenzoic acid and 4-hydroxybenzoic acid in the product react with each other. As a result, the production efficiency decreases, and it tends to take a long time to remove 4-hydroxybenzoic acid in the post-treatment process. Also, when the amount of 4-hydroxybenzoic acid is less than 1 mole, the production rate tends to decrease.

[0015] In the present invention, for example, the reaction between 1 mole of the diol represented by the formula (1) and 2 moles of 4-hydroxybenzoic acid is carried out by allowing each reaction raw material to be present in such an amount that the amount of 4-hydroxybenzoic acid is 2 moles per 1 mole of the diol represented by the formula (1).

[0016] Examples of the acid catalyst used in the present invention include one or more selected from the group consisting of p-toluenesulfonic acid, benzenesulfonic acid, 2-naphthalenesulfonic acid, sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid. Sulfuric acid or p-toluenesulfonic acid is preferable in terms of easy availability and excellent reactivity, and particularly, p-toluenesulfonic acid is preferable in terms of excellent reactivity and by-product suppression effect. p-Toluenesulfonic acid may be a hydrate.

[0017] These catalysts may be used alone or in combination of two or more.

[0018] The amount of the acid catalyst used in the present invention is not particularly limited, but is preferably 0.1 to 50 parts by mass, more preferably 1 to 30 parts by mass, and still more preferably 3 to parts by mass with respect to 100 parts by mass of the diol represented by the formula (1).

[0019] When the amount of the acid catalyst is less than 0.1 part by mass with respect to 100 parts by mass of the diol represented by the formula (1), the reaction tends not to proceed sufficiently. When the amount of the acid catalyst exceeds 50 parts by mass, by-products such as the di-ether form of the diol and bis-hydroxybenzoic acid ester compounds which are reaction products of the product with bis-hydroxybenzoic acid and 4-hydroxybenzoic acid tend to be generated, and it is also economically disadvantageous.

[0020] In the method of the present invention, mesitylene is used as the solvent. By using mesitylene as the solvent, side reactions are suppressed while the production rate of the bis-hydroxybenzoic acid ester compound is significantly improved.

[0021] The amount of mesitylene used in the present invention is preferably 100 to 3000 parts by mass (1 to 30 times by mass with respect to the diol), more preferably 150 to 2000 parts by mass, still more preferably 200 to 1500 parts by mass, and particularly preferably 300 to 1000 parts by mass with respect to 100 parts by mass of the diol represented by the formula (1). When the amount of mesitylene used is within the above range, the production rate of the bis-hydroxybenzoic acid ester compound can be improved efficiently.

[0022] The reaction temperature in the reaction of the diol represented by the formula (1) and 4-hydroxybenzoic acid is not particularly limited, but is preferably 80 to 200 ° C, more preferably 100 to 180 ° C. When the reaction temperature is within the above range, side reactions are suppressed while the reaction easily proceeds sufficiently.

[0023] The reaction time is not particularly limited because it varies depending on conditions such as the reaction temperature, but is usually 1 to 30 hours, preferably 2 to 20 hours, and more preferably 3 to 15 hours, and may be appropriately selected.

[0024] In the present invention, the reaction of the diol represented by the formula (1) and 4-hydroxybenzoic acid is preferably carried out under a stream of an inert gas or bubbling, or under reduced pressure conditions. By reacting under such conditions, reaction inhibition and catalyst deactivation by oxygen and moisture can be avoided, and the reaction can proceed smoothly.

[0025] The inert gas may be any gas that does not inhibit the reaction. Specifically, examples include one or more selected from the group consisting of nitrogen, carbon dioxide, argon, helium, neon, xenon, and krypton. Among these, nitrogen is preferable in terms of easy availability and economy.

[0026] The inert gas may be blown into the space above the reaction solution in the reaction vessel containing the diol represented by formula (1) and 4-hydroxybenzoic acid, which are the raw materials, or may be blown directly into the reaction solution.

[0027] By the above reaction of the diol represented by formula (1) and 4-hydroxybenzoic acid, formula (2): TIFF0007715386000008.tif34110[wherein, Ar represents the same divalent aromatic group as Ar in formula (1)] The bis-hydroxybenzoic acid ester compound represented by the formula is produced.

[0028] Examples of the bis(hydroxybenzoic acid) ester compound represented by the formula (2) include 4,4′-bis(4-hydroxybenzoic acid)-1,1′-biphenyl, 1,4-bis(4-hydroxybenzoic acid) phenyl, 2-methyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2-methyl-4,4′-bis(4-hydroxybenzoic acid)-1,1′-biphenyl, 2,3-dimethyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,5-dimethyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,6-dimethyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,3,5-trimethyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2-ethyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,3-diethyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,5-diethyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,6-diethyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,3,5-triethyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2-tert-butyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,3-di-tert-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,5-di-tert-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,6-di-tert-butyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,3,5-tri-tert-butyl-1,4-bis(4-hydroxybenzoic acid) phenyl, 2-chloro-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,3-dichloro-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,5-dichloro-1,4-bis(4-hydroxybenzoic acid) phenyl, 2,3,5-trichloro-1,4-bis(4-hydroxybenzoic acid) phenyl, 2-methoxy-1,4-bis(4-hydroxybenzoic acid) phenyl, and the like. Among them, one or more selected from the group consisting of 4,4′-bis(4-hydroxybenzoic acid)-1,1′-biphenyl, 1,4-bis(4-hydroxybenzoic acid) phenyl, and 2-methyl-1,4-bis(4-hydroxybenzoic acid) phenyl are preferable. Each structural formula is shown below.

[0029] · 4,4'-Bis(4-hydroxybenzoic acid)-1,1'-biphenyl TIFF0007715386000009.tif24103· 1,4-Bis(4-hydroxybenzoic acid)phenyl TIFF0007715386000010.tif2797· 2-Methyl-1,4-bis(4-hydroxybenzoic acid)phenyl TIFF0007715386000011.tif3093

[0030] In the presence of mesitylene and an acid catalyst, by reacting a diol represented by formula (1) with 4-hydroxybenzoic acid, a crude composition containing a bis-hydroxybenzoic acid ester compound represented by formula (2) is obtained. The crude composition containing the bis-hydroxybenzoic acid ester compound represented by formula (2) can be further purified to increase its purity.

[0031] Purification preferably includes a step of suspension washing with a suspension washing solvent and / or a step of recrystallization with a recrystallization solvent, in that the purity of the product can be efficiently increased. After the crude composition after the above reaction is cooled from the reaction temperature to 10 to 100 °C, mesitylene is removed by filtration or the like, and then it is subjected to a subsequent purification method.

[0032] Before the above purification operation, if necessary, washing with an aqueous medium to remove water-soluble compounds, filtration treatment to remove insoluble foreign matters, and adsorption treatment with an adsorbent such as activated carbon to remove coloring substances, metals, etc. may be performed.

[0033] The crude composition containing the bis-hydroxybenzoic acid ester compound represented by formula (2) means a composition containing impurities such as reaction raw materials, catalysts, and reaction by-products in addition to the target bis-hydroxybenzoic acid ester compound represented by formula (2). The content of impurities varies depending on the reaction method, but is usually 1 to 25% by mass in the crude composition, and in another case, 3 to 15% by mass.

[0034] Specific impurities contained in the crude composition include, in addition to residues of raw materials such as 4-hydroxybenzoic acid, diol, and catalyst, reaction intermediates that are reaction products of diol and 4-hydroxybenzoic acid, dimerized ether forms of diol that are reaction by-products, and reaction products of bis-hydroxybenzoic acid ester and 4-hydroxybenzoic acid such as sulfate esters and products.

[0035] The step of performing suspension washing is preferably carried out by adding a suspension washing solvent to a crude composition containing a bis-hydroxybenzoic acid ester compound represented by formula (2) and stirring in a suspended state at 60 to 140 °C for 1 to 10 hours.

[0036] Examples of the suspension washing solvent used in the step of performing suspension washing include one or more selected from the group consisting of N,N-dimethylformamide (DMF), toluene, water, methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, glycerin, acetic acid, N-methyl-2-pyrrolidone, dimethyl sulfoxide, acetonitrile, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, tetrahydrofuran, 4-methyltetrahydropyran, dioxane, ethyl acetate, propyl acetate, and butyl acetate. N,N-dimethylformamide (DMF) or toluene is preferred because of its excellent impurity removal properties.

[0037] The amount of the suspension washing solvent used in the step of performing suspension washing varies depending on the type of the solvent, but is preferably 1 to 20 times the mass of the diol used as the raw material, more preferably 1.5 to 10 times the mass. When the amount of the suspension washing solvent used is less than 1 time the mass of the diol used, impurities such as reaction intermediates of the raw material, diol and 4-hydroxybenzoic acid, catalyst, or reaction products of bis-hydroxybenzoic acid ester and 4-hydroxybenzoic acid as the product are incorporated into the crystals, and it tends to be difficult to obtain high-purity crystals. When it exceeds 20 times the mass, the yield of the bis-hydroxybenzoic acid ester compound may be significantly reduced.

[0038] The recrystallization step is preferably carried out by adding a recrystallization solvent to a crude composition containing the bis(hydroxybenzoic acid) ester compound represented by the formula (2), heating the temperature to 80 to 100 °C to completely dissolve the crude composition, and then cooling the temperature to 20 to 0 °C with stirring to precipitate crystals of the bis(hydroxybenzoic acid) ester compound.

[0039] The recrystallization solvent used in the recrystallization step includes one or more selected from the group consisting of N,N-dimethylformamide (DMF), toluene, water, methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, glycerin, acetic acid, N-methyl-2-pyrrolidone, dimethyl sulfoxide, acetonitrile, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, tetrahydrofuran, 4-methyltetrahydropyran, dioxane, ethyl acetate, propyl acetate, and butyl acetate. N,N-dimethylformamide (DMF) is preferred because of its excellent impurity removal property.

[0040] The amount of the recrystallization solvent used in the recrystallization step varies depending on the type of the solvent, but is preferably 1 to 20 times by mass, more preferably 1.5 to 10 times by mass, based on the amount of the diol used as the raw material. When the amount of the recrystallization solvent used is less than 1 time by mass based on the amount of the diol used, impurities such as the raw material, catalyst, or by-products are likely to be incorporated into the crystals, making it difficult to obtain high-purity crystals. When it exceeds 20 times by mass, the yield of the bis(hydroxybenzoic acid) ester compound may significantly decrease.

[0041] Which of the steps of suspension washing with a suspension washing solvent and recrystallization with a recrystallization solvent is adopted is determined by the solubility of the crude composition containing the bis(hydroxybenzoic acid) ester compound represented by the formula (2) as the target product in the solvent used, and conditions such as the temperature, stirring, and amount of the solvent used during suspension or dissolution. The case where a part of the crude composition is dissolved is also included in the step of suspension washing.

[0042] The crystals obtained by suspension washing or recrystallization are separated into solid and liquid by conventional means such as filtration to recover the target bis-hydroxybenzoic acid ester compound. When performing solid-liquid separation, it is preferable to appropriately pour an organic solvent to wash the crystals. As the organic solvent used for solid-liquid separation, one or more selected from the group consisting of methanol, ethanol, 1-propanol, and 2-propanol are preferably used. The organic solvent is preferably used in an amount of 0.5 to 2 times the mass of the diol.

[0043] The crystals recovered by solid-liquid separation can be dried by ventilation under normal pressure or dried under reduced pressure to distill off the solvent, thereby obtaining a high-purity bis-hydroxybenzoic acid ester compound.

Examples

[0044] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. The abbreviations of each compound are as follows. BP-POB2: 4,4′-bis(4-hydroxybenzoic acid)-1,1′-biphenyl HQ-POB2: 1,4-bis(4-hydroxybenzoic acid)phenyl MeHQ-POB2: 2-methyl-1,4-bis(4-hydroxybenzoic acid)phenyl

[0045] Each compound was analyzed by the following method.

[0046] ·Analysis of BP-POB2 <High Performance Liquid Chromatography (HPLC)> Apparatus: Waters Alliance 2690 / 2996 Column model number: L-Column ODS Liquid volume: 1 mL / min Solvent ratio: H2O (pH 2.3) / acetonitrile = 90 / 10 (7.0 minutes) → 1 minute → 60 / 40 (7.0 minutes) → 1 minute → 30 / 70 (4 minutes) → 1 minute → 10 / 90 (19 minutes), gradient analysis Wavelength: 254 nm Column temperature: 40 °C

[0047] ·Analysis of HQ-POB2 <Ultra Performance Liquid Chromatography (UPLC)> Equipment: Waters UPLC H-Class system Column model number: ACQUITY UPLC HSS C18 1.8 μm 2.1×50 mm Equipment: Hitachi Chromaster Column model number: L-Column ODS Flow rate: 0.5 mL / min Solvent ratio: H2O (pH 2.3) / Methanol = 90 / 10 (1.8 min) → 0.2 min → 30 / 70 (3.6 min) → 0.5 min → 20 / 80 (2.3 min) → 0.5 min → 10 / 90 (2.1 min), gradient analysis Wavelength: 229 nm Column temperature: 40 °C

[0048] ·Analysis of MeHQ-POB2 <High Performance Liquid Chromatography (HPLC)> Equipment: Waters Alliance 2690 / 2996 Column model number: L-Column ODS Flow rate: 1.0 mL / min Solvent ratio: H2O (pH 2.3) / Methanol = 90 / 10 (20 min) → 1 min → 30 / 70 (20 min) → 1 min → 10 / 90 (13 min), gradient analysis Wavelength: 229 nm Column temperature: 40 °C

[0049] Example 1: Synthesis of BP-POB2 Into a 0.5 L four-necked flask equipped with a stirrer, a temperature sensor, and a Dean-Stark apparatus, 40.0 g (0.215 mol) of 4,4′-dihydroxybiphenyl (BP, manufactured by Tokyo Chemical Industry Co., Ltd.), 59.3 g (0.430 mol) of 4-hydroxybenzoic acid (POB, manufactured by Ueno Pharmaceutical Co., Ltd.), 4.4 g of p-toluenesulfonic acid monohydrate (PTS·H2O) (11 parts by mass based on 100 parts by mass of BP), and 240.0 g of mesitylene (6.0 times the mass of BP) were added. While flowing nitrogen, the temperature was raised to reflux at 160 - 164 °C and reacted at the same temperature for 7 hours to obtain a crude composition. The obtained crude composition was quantitatively analyzed by HPLC. The results are shown in Table 1.

[0050] Example 2: Synthesis of HQ-POB2 Into a 0.5 L four-necked flask equipped with a stirrer, a temperature sensor, and a Dean-Stark apparatus, 40.0 g (0.363 mol) of hydroquinone (HQ, manufactured by Tokyo Chemical Industry Co., Ltd.), 100.4 g (0.726 mol) of 4-hydroxybenzoic acid (POB, manufactured by Ueno Pharmaceutical Co., Ltd.), 4.0 g of p-toluenesulfonic acid monohydrate (PTS·H2O) (10 parts by mass based on 100 parts by mass of HQ), and 352.0 g of mesitylene (8.8 times the mass of HQ) were added. While flowing nitrogen, the temperature was raised to reflux at 160 - 164 °C and reacted at the same temperature for 7 hours to obtain a crude composition. The obtained crude composition was quantitatively analyzed by UPLC. The results are shown in Table 1.

[0051] Example 3: Synthesis of MeHQ-POB2 Into a 0.5 L four-necked flask equipped with a stirrer, a temperature sensor, and a Dean-Stark apparatus, 40.0 g (0.322 mol) of 2-methylhydroquinone (MeHQ, manufactured by Wako Pure Chemical Industries, Ltd.), 89.0 g (0.644 mol) of 4-hydroxybenzoic acid (POB, manufactured by Ueno Pharmaceutical Co., Ltd.), 4.4 g of p-toluenesulfonic acid monohydrate (PTS·H2O) (11 parts by mass based on 100 parts by mass of MeHQ), and 240.0 g of mesitylene (6.0 times the mass of MeHQ) were added. While flowing nitrogen, the temperature was raised to reflux at 160 - 164 °C and reacted at the same temperature for 5 hours to obtain a crude composition. The obtained crude composition was quantitatively analyzed by HPLC. The results are shown in Table 1.

[0052] Comparative Example 1: Synthesis of BP-POB2 Mesitylene was changed to xylene, and the reaction was carried out in the same manner as in Example 1 except that the reflux was carried out at a temperature of 138 to 141 °C to obtain a crude composition. The obtained crude composition was quantitatively analyzed by HPLC. The results are shown in Table 1.

[0053] Comparative Example 2: Synthesis of HQ-POB2 Mesitylene was changed to xylene, and the reaction was carried out in the same manner as in Example 2 except that the reflux was carried out at a temperature of 138 to 141 °C to obtain a crude composition. The obtained crude composition was quantitatively analyzed by UPLC. The results are shown in Table 1.

[0054] Comparative Example 3: Synthesis of MeHQ-POB2 Mesitylene was changed to xylene, and the reaction was carried out in the same manner as in Example 3 except that the reflux was carried out at a temperature of 138 to 141 °C to obtain a crude composition. The obtained crude composition was quantitatively analyzed by HPLC. The results are shown in Table 1.

[0055] Example 4: Purification of BP-POB2 (Suspension Washing) After filtering the reaction solution obtained in Example 1, the solid was washed with 40 g of DMF to obtain a crude composition containing BP-POB2. The obtained crude composition containing BP-POB2 and 180 g of DMF (4.5 mass times with respect to BP) were charged into a 0.5 L four-necked flask equipped with a stirrer and a temperature sensor, and stirring was continued in a suspended state at 140 °C for 3 hours. The suspension was cooled to 40 °C, suction filtered, washed with 40 g of methanol, and the obtained solid content was added again to a 0.5 L four-necked flask equipped with a stirrer and a temperature sensor. Further, 240 g of methanol (6.0 mass times with respect to BP) was charged, and stirring was continued in a suspended state at 60 °C for 2 hours. The suspension was cooled to 40 °C, suction filtered, washed with 40 g of methanol, and the recovered crystals were dried under reduced pressure at 10 Torr and 70 °C to obtain BP-POB2 (yield 81.7%). The obtained BP-POB2 was quantitatively analyzed by HPLC. The analysis results are shown in Table 2.

[0056] Example 5: Purification of HQ-POB2 (Recrystallization) After filtering the reaction solution obtained in Example 2, the solid was washed with 260 g of methanol to obtain a crude composition containing HQ-POB2. A 0.5 L four-necked flask equipped with a stirrer and a temperature sensor was charged with the obtained crude composition containing HQ-POB2 and 440 g of DMF (11.0 mass times relative to HQ), and the temperature was raised to 80 °C with stirring to dissolve HQ-POB2. After hot filtration with a filter, the temperature was lowered to 5 °C with stirring to precipitate crystals. After suction filtration, the crystals were washed with 100 g of cyclohexanone and recovered. A 1 L four-necked flask equipped with a stirrer and a temperature sensor was charged with the obtained crude composition containing HQ-POB2 and 520 g of cyclohexanone (13.0 mass times relative to HQ), and the temperature was raised to 150 °C with stirring, and stirring was continued in a suspended state at 150 °C for 2 hours. The suspension was cooled to 40 °C, suction filtered, washed with 80 g of methanol, and the crystals were recovered. By drying under reduced pressure at 20 Torr and 75 °C, HQ-POB2 was obtained (yield 71.0%). Quantitative analysis of the obtained HQ-POB2 was performed by UPLC. The analysis results are shown in Table 3.

[0057] Example 6: Purification of MeHQ-POB2 (Suspension Washing) After filtering the reaction solution obtained in Example 3, the solid was washed with 120 g of methanol to obtain a crude composition containing MeHQ-POB2. A 0.5 L four-necked flask equipped with a stirrer and a temperature sensor was charged with the obtained crude composition containing MeHQ-POB2 and 360 g of a mixed medium of toluene:methanol 7:3 (mass ratio) (9.0 mass times relative to MeHQ), and stirring was continued in a suspended state at 25 °C for 1 hour. After suction filtration of the suspension, the crystals were washed with 117 g of methanol and dried by ventilation at 100 °C to obtain MeHQ-POB2 (yield 83.9%). Quantitative analysis of the obtained MeHQ-POB2 was performed by HPLC. The analysis results are shown in Table 4.

[0058] As shown in Table 1, it can be seen that in Examples 1 to 3 of the present invention using mesitylene solvent, the production rate of the bis-hydroxybenzoic acid ester compound is significantly higher compared to Comparative Examples 1 to 3 carried out using solvents other than mesitylene. Also, as shown in Tables 2 to 4, it can be seen that by further performing purification such as suspension washing and recrystallization, by-products can be significantly removed.

[0059] TIFF0007715386000012.tif25050

[0060] TIFF0007715386000013.tif36122

[0061] TIFF0007715386000014.tif37121

[0062] TIFF0007715386000015.tif38137

Claims

1. In the presence of mesitylene and p-toluenesulfonic acid as an acid catalyst, a diol represented by the formula (1) [wherein, Ar represents a divalent aromatic group which may have a substituent] and 4-hydroxybenzoic acid are reacted, and a process for producing a bis(hydroxybenzoic acid ester) compound represented by the formula (2) [wherein, Ar represents the same divalent aromatic group as Ar in the formula (1)] is provided.

2. The method according to claim 1, wherein Ar is a group represented by any one of the following formulas (a) to (c) [wherein, "※" each indicates a bonding position]

3. The method according to claim 2, wherein Ar is a group represented by the formula (a).

4. The method according to claim 2, wherein Ar is a group represented by the formula (b).

5. The method according to claim 2, wherein Ar is a group represented by the formula (c).

6. The method according to any one of claims 1 to 5, wherein the amount of mesitylene used is 100 to 3000 parts by mass based on 100 parts by mass of the diol represented by the formula (1).

7. The method according to any one of claims 1 to 6, wherein 1 to 3 moles of 4-hydroxybenzoic acid are reacted with 1 mole of the diol represented by the formula (1).

8. The method according to any one of claims 1 to 7, wherein 0.1 to 50 parts by mass of an acid catalyst is present based on 100 parts by mass of the diol represented by the formula (1).

9. The method according to any one of claims 1 to 8, wherein the diol represented by the formula (1) and 4-hydroxybenzoic acid are reacted at a temperature of 80 to 200 °C.

10. The method according to claim 1, wherein the step is a step of obtaining a crude composition containing the bis(hydroxybenzoic acid ester) compound represented by the formula (2).

11. The method according to claim 10, which includes a step of subjecting the crude composition to suspension washing with a suspension washing solvent.

12. The method according to claim 11, wherein the suspension washing solvent contains N,N-dimethylformamide.

13. In the formulas (1) and (2), the method according to claim 12, wherein Ar is a group represented by the following formula (a)

14. The method according to claim 11, wherein the suspension washing solvent contains toluene.

15. In the formulas (1) and (2), the method according to claim 14, wherein Ar is a group represented by the following formula (c)

16. The method according to claim 10, which includes a step of recrystallizing the crude composition with a recrystallization solvent.

17. The method according to claim 16, wherein the recrystallization solvent contains N,N-dimethylformamide.

18. In the formula (1) and the formula (2), Ar is a group represented by the following formula (b) The method according to claim 17.

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