JP7675618B2 - Method for producing 2-methylene-1,3-propanediol - Google Patents

Description

The present invention relates to a method for producing 2-methylene-1,3-propanediol.

2-methylene-1,3-propanediol (hereinafter also referred to as "MPDA") is one of the raw materials for 2-methylene-1,3-propanediol diacetate (hereinafter also referred to as "MPDAc"). MPDAc is used, for example, as a modifier (comonomer) for ethylene-vinyl alcohol copolymer (hereinafter also referred to as "EVOH"). MPDAc-modified EVOH obtained by saponifying a copolymer of ethylene, vinyl ester, and MPDAc has the characteristics of having improved stretchability and shrinkability while maintaining good barrier properties compared to unmodified EVOH.

As a method for synthesizing MPDA, which is one of the raw materials for MPDAc, a method is known in which pentaerythritol is brominated and the resulting monobrominated pentaerythritol is reacted with a base. Non-Patent Document 1 describes that MPDA was synthesized by the following procedure. 39.8 g (0.2 mol) of the monobrominated pentaerythritol (pentaerythritol monobromide; 2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol, hereinafter also referred to as "BrPE") was dissolved in 160 mL of ethanol, 190 mL of ethanol solution of 13 g (0.23 mol) of potassium hydroxide was added, and the mixture was stirred at room temperature for 2 hours. The mixture was then heated to reflux for 5 minutes, cooled in an ice bath, and the precipitated potassium bromide was removed by filtration. The mixture was then neutralized with acetic acid and distilled under reduced pressure to obtain 4 g of MPDA. This synthesis also yielded 16.5 g of 3,3-bis(hydroxymethyl)-oxetane (hereinafter also referred to as "BHMO").

C. H. Issidorides and A. I. Matar, "Pentaerythritol Derivatives. I. The Preparation of Pentaerythritol Monomethyl Ether," Journal of the American Chemical Society, 1955, 77(23), p6382-6383

In the synthesis method of Non-Patent Document 1, 4 g (0.0454 mol) of MPDA is obtained from 39.8 g (0.2 mol) of BrPE, and the yield of MPDA is 23%. In addition to MPDA, 16.5 g (0.140 mol) of BHMO is also produced with a yield of 70%. Thus, the above synthesis method has a low yield of MPDA and is not a useful method for synthesizing MPDA.

The present invention was made based on these circumstances, and its purpose is to provide a method for producing MPDA with a high yield.

上記式（１）中、Ｒ^１、Ｒ^２及びＲ^３は、それぞれ独立して、水素原子又は炭素数２～１９のアシル基である。但し、Ｒ^１、Ｒ^２及びＲ^３がすべて水素原子の場合を除く。Ｘは、塩素原子、臭素原子、ヨウ素原子、メシル基又はトシル基である。
［２］上記反応させる工程を４０℃以上１２０℃以下の温度で行う、［１］のＭＰＤＡの製造方法；
［３］上記Ｘが臭素原子である、［１］又は［２］のＭＰＤＡの製造方法；
［４］上記Ｒ^１、Ｒ^２及びＲ^３が、それぞれ独立して、水素原子又はアセチル基である、［１］～［３］のいずれかのＭＰＤＡの製造方法；
［５］上記反応させる工程の前に、下記式（２）で表される化合物のエステル化により、上記式（１）で表される化合物を得る工程をさらに備える、［１］～［４］のいずれかのＭＰＤＡの製造方法；

上記式（２）中、Ｘは、塩素原子、臭素原子、ヨウ素原子、メシル基又はトシル基である。
［６］下記式（２）で表される化合物と塩基とを４０℃以上１２０℃以下の反応温度で反応させる工程を備える、ＭＰＤＡの製造方法；

上記式（２）中、Ｘは、塩素原子、臭素原子、ヨウ素原子、メシル基又はトシル基である。
［７］上記反応させる工程で得られた生成物を含む溶液に３０℃以下の温度でハロゲン化水素を混合する工程、及び上記ハロゲン化水素を混合する工程を経た上記溶液に塩基を混合する工程をさらに備える［１］～［６］のいずれかのＭＰＤＡの製造方法；
を提供することで達成される。 The above objectives are:
[1] A method for producing MPDA, comprising a step of reacting a compound represented by the following formula (1) with a base:

In the above formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom or an acyl group having 2 to 19 carbon atoms, except when R ¹ , R ² and R ³ are all hydrogen atoms. X is a chlorine atom, a bromine atom, an iodine atom, a mesyl group or a tosyl group.
[2] The method for producing MPDA according to [1], wherein the reacting step is carried out at a temperature of 40° C. or higher and 120° C. or lower;
[3] The method for producing MPDA according to [1] or [2], wherein X is a bromine atom;
[4] The method for producing MPDA according to any one of [1] to [3], wherein R ¹ , R ² and R ³ are each independently a hydrogen atom or an acetyl group;
[5] The method for producing MPDA according to any one of [1] to [4], further comprising a step of obtaining a compound represented by formula (1) by esterification of a compound represented by formula (2) below, prior to the reacting step;

In the above formula (2), X is a chlorine atom, a bromine atom, an iodine atom, a mesyl group, or a tosyl group.
[6] A method for producing MPDA, comprising a step of reacting a compound represented by the following formula (2) with a base at a reaction temperature of 40° C. or higher and 120° C. or lower:

In the above formula (2), X is a chlorine atom, a bromine atom, an iodine atom, a mesyl group, or a tosyl group.
[7] The method for producing MPDA according to any one of [1] to [6], further comprising the steps of mixing hydrogen halide with a solution containing the product obtained in the reacting step at a temperature of 30° C. or less, and mixing a base with the solution that has been subjected to the step of mixing hydrogen halide;
This is achieved by providing

The present invention provides a method for producing MPDA with a high yield.

<First Form>
A first embodiment of the method for producing 2-methylene-1,3-propanediol (MPDA) of the present invention includes a step (step B1) of reacting a compound represented by the following formula (1) with a base.

In the above formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom or an acyl group having 2 to 19 carbon atoms, except when R ¹ , R ² and R ³ are all hydrogen atoms. X is a chlorine atom, a bromine atom, an iodine atom, a mesyl group (CH ₃ -SO ₂ -) or a tosyl group (CH ₃ -C ₆ H ₄ -SO ₂ -).

According to this manufacturing method, MPDA can be manufactured in a high yield. The reason for this is unclear, but the following reason is presumed. In the reaction of BrPE (2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol) or the like described in Non-Patent Document 1 with a base, the synthesis reaction of MPDA by elimination of formaldehyde competes with the synthesis reaction of BHMO by intramolecular cyclization, and the intramolecular cyclization becomes dominant at room temperature. BrPE is a compound in which X in the formula (2) described below is Br. In contrast, when a portion of the hydroxyl groups of BrPE or the like is esterified and the esterified compound represented by the above formula (1) is reacted with a base, the intramolecular cyclization is suppressed and the elimination reaction is more likely to occur, which is presumed to increase the yield of MPDA.

In this production method, it is preferable to further include a step (step A) prior to step B1 of obtaining a compound represented by formula (1) by esterification of a compound represented by formula (2) below.

In the above formula (2), X is a chlorine atom, a bromine atom, an iodine atom, a mesyl group (CH ₃ —SO ₂ —) or a tosyl group (CH ₃ —C ₆ H ₄ —SO ₂ —).

When the production method further includes step A, MPDA can be efficiently produced using, for example, BrPE, in which X in formula (2) is Br, as a raw material.

In the first embodiment of the present invention, MPDA can be produced according to the following scheme 1. Scheme 1 also includes step C, which will be described later.

The first embodiment of the present invention will be described in detail below, along with each step.

(Process A)
In this step, the compound represented by the above formula (1) is obtained by esterification of the compound represented by the above formula (2).

In the above formula (2), X is preferably a bromine atom.

Examples of the compound represented by the above formula (2) include 2-bromomethyl-2-hydroxymethyl-1,3-propanediol and 2-chloromethyl-2-hydroxymethyl-1,3-propanediol. One or more of the compounds represented by the above formula (2) can be used. The compound represented by the above formula (2) can be synthesized by a known method such as halogenation, mesylation, or tosylation of pentaerythritol.

The esterification of the compound represented by the above formula (2) can be carried out by reacting the compound represented by the above formula (2) with a carboxylic acid, a carboxylic acid anhydride, a carboxylic acid halide, or the like. Examples of the carboxylic acid include acetic acid, propionic acid, butyric acid, and benzoic acid. Examples of the carboxylic acid include a carboxylic acid having 2 to 19 carbon atoms, more preferably a carboxylic acid having 2 to 7 carbon atoms, even more preferably a carboxylic acid having 2 to 4 carbon atoms, and particularly preferably acetic acid. Examples of the carboxylic acid halide include a chloride and a bromide. Among the carboxylic acids, carboxylic acid anhydrides, and carboxylic acid halides, it is preferable to use a carboxylic acid. In addition, acetic acid, acetic anhydride, or a halide of acetic acid (acetyl chloride, acetyl bromide, etc.) is preferable, and acetic acid is more preferable.

This step can be carried out by mixing the compound represented by the above formula (2) with a carboxylic acid or the like in a solvent such as water or alcohol, and is preferably carried out under heating. The reaction temperature (reaction solution temperature) of this step is, for example, preferably 60°C or higher and 120°C or lower, more preferably 80°C or higher and 110°C or lower, and even more preferably 90°C or higher and lower than 100°C. The reaction time is, for example, preferably 5 minutes or higher and 8 hours or lower, more preferably 15 minutes or higher and 6 hours or lower, and even more preferably 30 minutes or higher and 4 hours or lower. This step may be carried out under pressure or reduced pressure, or under atmospheric pressure. In addition, water is preferable as the solvent. The reaction solution used in this step may further contain other components other than the compound represented by the above formula (2), the carboxylic acid, and the solvent.

The amount of the carboxylic acid or the like used in this step is, for example, preferably 0.2 moles or more and 10 moles or less, more preferably 1 mole or more and 5 moles or less, and even more preferably 1.2 moles or more and 4 moles or less, relative to 1 mole of the compound represented by the above formula (2). In this step, at least a portion of the compound represented by the above formula (2) present in the reaction solution is esterified.

In the solution containing the compound represented by formula (1) obtained through this step, by-products, unreacted compounds represented by formula (2), carboxylic acids, etc. may be present. In addition, such a solution can be used as is in the next step B1. The obtained solution may be purified or the like before being used in step B1.

(Process B1)
In this step, the compound represented by formula (1) is reacted with a base. In this reaction, the base acts as a catalyst to produce MPDA from the compound represented by formula (1). When the reaction solution also contains a compound represented by formula (2), this compound represented by formula (2) also becomes MPDA in this step. In addition, in this step, BHMO may also be produced as a by-product.

In the above formula (1), X is preferably a bromine atom.

Examples of the acyl group having 2 to 19 carbon atoms represented by R ¹ , R ² and R ³ in the above formula (1) include an acetyl group, a propanoyl group, a butanoyl group, a benzoyl group, etc. As the acyl group having 2 to 19 carbon atoms, an acyl group having 2 to 7 carbon atoms is preferable, an acyl group having 2 to 4 carbon atoms is more preferable, and an acetyl group is particularly preferable. That is, it is particularly preferable that R ¹ , R ² and R ³ are each independently a hydrogen atom or an acetyl group.

In the above formula (1), all of R ¹ , R ² and R ³ may be acyl groups, only two of them may be acyl groups, or only one of them may be an acyl group. The compound represented by the above formula (1) may be used alone or in a mixture of two or more kinds.

Examples of bases used in this step include sodium hydroxide, potassium hydroxide, sodium methoxide, tetramethylammonium hydroxide, calcium hydroxide, etc. Among these, sodium hydroxide or potassium hydroxide is preferred, and sodium hydroxide is more preferred. One or more types of bases can be used.

This step can be carried out by mixing the compound represented by formula (1) and the base in a solvent such as water or alcohol, and is preferably carried out under heating. The lower limit of the reaction temperature (reaction solution temperature) in this step is preferably 40°C, more preferably 60°C, and even more preferably 80°C. By setting the reaction temperature at or above the lower limit, intramolecular cyclization is further suppressed, and the yield of MPDA can be further increased. The upper limit of this reaction temperature is preferably 120°C, more preferably 110°C, and even more preferably 100°C. By setting the reaction temperature at or below the upper limit, it is possible to suppress the occurrence of other side reactions and also to suppress corrosion of the manufacturing equipment caused by the elution of the glass lining by the base. In addition, water is preferable as the solvent. The reaction solution used in this step may further contain other components other than the compound represented by formula (1), the remaining compound represented by formula (2), the base, and the solvent.

The reaction time in this step is preferably, for example, from 5 minutes to 4 hours, more preferably from 10 minutes to 3 hours, and even more preferably from 20 minutes to 2 hours. This step may be carried out under increased or reduced pressure, or under atmospheric pressure.

The amount of base used in this step is, for example, preferably 0.5 to 20 moles, more preferably 1 to 15 moles, and even more preferably 2 to 10 moles, relative to the total mole of the compound represented by the above formula (1) and the compound represented by the above formula (2). When steps A and B1 are performed consecutively, that is, when a carboxylic acid or the like is added to a solution containing the compound represented by the above formula (2) to produce the compound represented by the above formula (1), and a base is added to the solution to perform step B1, the remaining carboxylic acid or the like and the base may be neutralized, and the base may be consumed. Therefore, it is preferable to adjust the amount of base to be added taking into account the amount of the remaining carboxylic acid or the like.

After step B1, the solution containing the product MPDA can be purified by a known method to isolate MPDA. As described below, the raw material compound represented by formula (2) may be subjected to a regeneration step (step C) to further increase the yield of MPDA.

<Second Form>
A first embodiment of the method for producing 2-methylene-1,3-propanediol (MPDA) of the present invention includes a step (step B2) of reacting a compound represented by the following formula (2) with a base at a reaction temperature of 40° C. or higher and 120° C. or lower:

In the above formula (2), X is a chlorine atom, a bromine atom, an iodine atom, a mesyl group (CH ₃ —SO ₂ —) or a tosyl group (CH ₃ —C ₆ H ₄ —SO ₂ —).

In this manufacturing method, the compound represented by the above formula (2) is reacted with a base at a relatively high temperature without being esterified. In the second embodiment of the present invention, MPDA is manufactured according to the following scheme 2. Scheme 2 also includes step C, which will be described later. This manufacturing method can also produce MPDA in a high yield. The reason for this is unclear, but the following reason is presumed. As described above, in the reaction of BrPE and the like with a base described in Non-Patent Document 1, the synthesis reaction of MPDA by elimination of formaldehyde and the synthesis reaction of BHMO by intramolecular cyclization compete with each other, and at room temperature, intramolecular cyclization becomes dominant. Therefore, it is presumed that the intramolecular cyclization is suppressed by increasing the reaction temperature, and the yield of MPDA is increased.

Step B2 can be carried out in the same manner as step B1 described above, except that instead of the compound represented by formula (1), a compound represented by formula (2) is used and the reaction temperature is set to 40°C or higher and 120°C or lower. The specific form and preferred form of step B2 are the same as the specific form and preferred form of step B1 described above, except that a compound represented by formula (2) is used. In addition, the specific form and preferred form of the compound represented by formula (2) used in step B2 are the same as the specific form and preferred form of the compound represented by formula (2) used in step A described above.

(Process C etc.)
In both the first and second aspects, the production method of the present invention preferably further comprises a step (step C) of mixing hydrogen halide at a temperature of 30° C. or lower with a solution containing a product obtained in the step (step B1 or step B2) of reacting the compound represented by formula (1) or (2) with a base, and a step (steps B1 and B2) of mixing a base with the solution that has been subjected to the step (step C) of mixing hydrogen halide.

In steps B1 and B2, as described above, the synthesis reaction of MPDA by elimination of formaldehyde competes with the synthesis reaction of BHMO by intramolecular cyclization. Therefore, the solution containing the product MPDA obtained through step B1 or step B2 usually also contains the by-product BHMO. Therefore, by carrying out step C, BHMO is regenerated into the compound represented by formula (2) above, which is the raw material, and this can be used again as a raw material.

The upper limit of the reaction temperature (reaction solution temperature) in this step C is preferably 30°C, more preferably 20°C, and even more preferably 15°C. By setting the reaction temperature below the above upper limit, the reaction of the mixed hydrogen halide with MPDA can be suppressed, and the yield of MPDA can be increased. The lower limit of the reaction temperature in this regeneration step may be, for example, 0°C or 5°C.

Examples of hydrogen halides include hydrogen bromide, hydrogen chloride, and hydrogen iodide, with hydrogen bromide being preferred. One or more types of hydrogen halides can be used. Hydrogen halides can be used as aqueous solutions of hydrobromic acid, hydrochloric acid, etc.

The amount of hydrogen halide used in this step is preferably, for example, 0.5 to 10 moles, more preferably 1 to 6 moles, per mole of the total of the products (MPDA and BHMO) in the solution.

The reaction time in this step is, for example, preferably from 0.5 hours to 12 hours, more preferably from 1 hour to 8 hours, and even more preferably from 1.5 hours to 5 hours.

Following this step C, for example, step B2 can be carried out in which a base is mixed with a solution containing the obtained product (MPDA and the compound represented by the above formula (2), etc.) (see scheme 2). This step B2 converts the regenerated compound represented by the above formula (2) to MPDA, and the yield of MPDA can be increased. Step B2 after step C can be carried out in the same manner as step B2 described in the explanation of the second embodiment. Note that since the solution containing the product obtained through step C is usually acidic, it is preferable to use a base in consideration of the amount consumed by neutralization. Alternatively, the solution may be neutralized once and then subjected to step B2.

Following step C, step A may be carried out to obtain a compound represented by formula (1) by esterifying the regenerated compound represented by formula (2) (see scheme 1). Then, step B2 may be carried out to react the compound represented by formula (1) with the base by mixing a base with a solution containing the compound represented by formula (1). Step A after step C and the subsequent step B1 may be carried out in the same manner as step A and step B1 described in the explanation of the first embodiment. By producing MPDA by carrying out such steps, the yield of MPDA can be further increased.

The cycle of scheme 1 or scheme 2 involving the regeneration step may be carried out two or more times. That is, MPDA may be produced by a cycle in which step C is carried out two or more times. By carrying out the regeneration process multiple times, the by-product BHMO can be reduced and the yield of MPDA can be further increased.

(Other processes, etc.)
In the production method, it is preferable to include a step (purification step) of purifying the solution containing the obtained product (product liquid) after the final step B1 or B2. By carrying out the purification, MPDA with high purity can be obtained. Purification of MPDA can be carried out by a conventionally known method.

In addition, in this manufacturing method, the product liquid usually contains a salt of a hydrogen halide, such as sodium bromide, and a base. Such a salt containing a halogen can be recovered and reused as hydrogen halide by a known method, for example, by reacting it with an acid, such as sulfuric acid or phosphoric acid, in water.

(Applications, etc.)
The MPDA obtained by this production method can be used in various conventionally known applications. For example, 2-methylene-1,3-propanediol diacetate (MPDAc) can be obtained by acetylating MPDA using acetic acid, acetic anhydride, or the like in the presence of a catalyst. MPDAc can be suitably used as a comonomer in the production of modified ethylene-vinyl ester copolymers (modified EVOH). Such MPDAc-modified EVOH has the characteristics of having improved stretchability and shrinkability while maintaining good barrier properties compared to unmodified EVOH.

<Other embodiments>
The present invention is not limited to the above embodiment. For example, in the first embodiment described above, the step B1 of obtaining the compound represented by the formula (1) by esterification of the compound represented by the formula (2) may not be performed. For example, the compound represented by the formula (1) may be purchased and the step B1 may be performed using the compound. The compound represented by the formula (1) may also be synthesized by a method other than esterification. For example, the compound represented by the formula (1) may be obtained by (a) reacting pentaerythritol tetraacetate with hydrogen halide, (b) mixing a mixture of pentaerythritol tetraacetate and pentaerythritol at any ratio with hydrogen halide and performing a halogenation reaction while performing an ester exchange reaction, or (c) adding acetic acid to pentaerythritol and reacting it with hydrogen halide.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

(Compositional Analysis of Reactants and Products)
The compositions of the reactants and products were analyzed by ¹ H-NMR (measurement solvent: deuterium oxide) at a measurement temperature of 25° C. The chemical shifts of each compound are as follows:
2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol (BrPE): 3.44 ppm (6H), 3.33 ppm (2H)
2-Methylene-1,3-propanediol (MPDA): 5.04 ppm (2H), 4.00 ppm (4H)
3,3-Bis(hydroxymethyl)-oxetane (BHMO): 4.42 ppm (4H), 3.69 ppm (4H)
Compound (mono-acetyl substitution product) in which R ¹ in the above formula (1) is an acetyl group, R ² and R ³ are hydrogen atoms, and X is Br: 3.94 ppm (2H), 3.47 ppm (4H), 3.36 ppm (2H), 1.97 ppm (3H)
The composition ratio of each compound was determined by ^1H -NMR. The amounts of other components were calculated by the following procedure. From the total integral value of the chemical shift from 0.5 to 6 ppm in the measured ^1H -NMR chart, the peaks derived from the solvent heavy water: 4.65 ppm, acetic acid: 1.93 ppm (3H), BrPE, MPDA and BHMO were excluded, and the resulting value was assumed to be an 8H compound, and the yield of other components was calculated.

[Example 1] Synthesis of MPDA (Step B2: Reaction solution temperature 95°C)
100 parts by mass of 2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol (BrPE) and 100 parts by mass of water were placed in a three-neck flask equipped with a reflux condenser, and the mixture was stirred for 10 minutes in a 110° C. oil bath at a reaction temperature of 95° C. to dissolve. With the reaction temperature at 95° C., 160 parts by mass (2.0 molar equivalents) of a 25% by mass aqueous sodium hydroxide solution was added, and the mixture was stirred for 30 minutes at a reaction temperature of ⁹⁵ ° C. The reactor was removed from the oil bath and cooled to room temperature, and the yields of 2-methylene-1,3-propanediol (MPDA), 3,3-bis(hydroxymethyl)-oxetane (BHMO), and other products were analyzed by 1 H-NMR (measurement solvent: deuterium oxide), and were 40%, 57%, and 3%, respectively. The yield of MPDA at a reaction temperature of 95° C. was 40%.

[Example 2] Synthesis of MPDA (Step B2: Reaction solution temperature 70°C)
The reaction was carried out under the same conditions as in Example 1, except that the oil bath temperature was changed to 85° C. and the reaction solution temperature was changed to 70° C. The yields of MPDA, BHMO and other products were analyzed by ¹ H-NMR (measurement solvent: heavy water) and were found to be 33%, 63% and 4%, respectively. The yield of MPDA at a reaction solution temperature of 70° C. was 33%.

[Comparative Example 1] Synthesis of MPDA (Step B2: Reaction solution temperature 25°C)
The reaction was carried out under the same conditions as in Example 1, except that an oil bath was not used, the reaction solution temperature was changed to 25° C., and the reaction time was changed to 4 hours. The yields of MPDA, BHMO, and other products were analyzed by ¹ H-NMR (measurement solvent: heavy water) and were found to be 20%, 75%, and 5%, respectively. The yield of MPDA at a reaction solution temperature of 25° C. was 20%.

Comparing Examples 1 and 2 with Comparative Example 1, it can be seen that by increasing the reaction temperature (reaction solution temperature) to 40°C or higher, the production of BHMO is suppressed and the yield of MPDA is increased.

[Example 3] Synthesis of MPDA (Step A + Step B1: Reaction solution temperature 95°C)
100 parts by mass of BrPE, 100 parts by mass of water, and 60 parts by mass of acetic acid were placed in a three-neck flask equipped with a reflux condenser, and the mixture was stirred for 10 minutes in a 110° C. oil bath at a reaction temperature of 95° C. to dissolve the mixture. An esterification reaction was then carried out for 2 hours at 95° C. When the esterification rate of BrPE was confirmed by ¹ H-NMR (measurement solvent: heavy water), it was confirmed that 32% of an acetyl monosubstitution product in which X in the above formula (1) is Br (bromine) was produced.
Thereafter, with the reaction solution temperature at 95° C., 320 parts by mass (4.0 molar equivalents) of a 25% by mass aqueous sodium hydroxide solution was added, and the reaction solution was stirred for 30 minutes at a temperature of 95° C. The reactor was removed from the oil bath and cooled to room temperature, and the yields of other products excluding MPDA, BHMO, and acetic acid were analyzed by ¹ H-NMR (measurement solvent: heavy water), and the results were 52%, 44%, and 4%, respectively. The yield of MPDA when acetic acid was added at a reaction solution temperature of 95° C. was 52%, and MPDA was obtained in a higher yield by esterifying with acetic acid and then reacting with a base.

[Example 4-1] Regeneration of raw materials in the presence of MPDA (Step C: Reaction solution temperature 10°C)
A three-neck flask containing 360 parts by mass of the solution containing the product obtained in Example 1 was placed in an ice bath at 0° C. and stirred, and 202 parts by mass (2.2 molar equivalents) of 48% by mass hydrobromic acid was slowly added dropwise so that the reaction liquid temperature was 5° C. or less. The reaction liquid temperature was further maintained at 10° C. and stirred for 3 hours. At a reaction liquid temperature of 10° C., 16 parts by mass of a 25% by mass aqueous sodium hydroxide solution was further added for neutralization. The yields of MPDA, BHMO, BrPE, and other products were analyzed by ¹ H-NMR (measurement solvent: heavy water) and were 40%, 0%, 57%, and 3%, respectively. At a reaction liquid temperature of 10° C., MPDA did not react with HBr, and BHMO was quantitatively converted to BrPE.

[Example 4-2] Synthesis of MPDA (Step B2: Reaction temperature 95°C)
578 parts by mass of the solution containing the product obtained in Example 4-1 was placed in a three-neck flask equipped with a reflux condenser, and stirred for 10 minutes at a reaction temperature of 95° C. in a 110° C. oil bath. With the reaction temperature at 95° C., 160 parts by mass (2.0 molar equivalents) of a 25% by mass aqueous sodium hydroxide solution was added, and the reaction temperature was stirred for 30 minutes at 95° C. The reactor was removed from the oil bath and cooled to room temperature, and the yields of MPDA, BHMO, and other products were analyzed by ¹ H-NMR (measurement solvent: heavy water), and were 63%, 31%, and 6%, respectively. The yield of MPDA obtained in this reaction was 63%, and MPDA was obtained in a high yield.

[Example 5] Regeneration of raw materials (second time) and synthesis of MPDA Regeneration of raw materials and synthesis of MPDA were carried out in the same manner as in Examples 4-1 and 4-2, except that a solution containing 738 parts by mass of the product obtained in Example 4-2 was used as the raw material instead of 360 parts by mass of the solution containing the product obtained in Example 1. The yields of MPDA, BHMO, and other products were analyzed by ¹ H-NMR (measurement solvent: deuterium oxide) and were 75%, 17%, and 8%, respectively. The yield of MPDA obtained in this reaction was 75%, and MPDA was obtained in a higher yield.

[Reference Example 2-1] Regeneration of raw materials in the presence of MPDA (Step C: reaction solution temperature 95°C)
A three-neck flask containing 360 parts by mass of the solution containing the product obtained in Example 1 was placed in an oil bath at 110° C. and stirred, and 202 parts by mass (2.2 molar equivalents) of 48% by mass hydrobromic acid was slowly dropped so that the reaction liquid temperature reached 95° C. The reaction liquid was stirred for another 3 hours at a temperature of 95° C., and neutralized by adding 16 parts by mass of a 25% by mass aqueous sodium hydroxide solution. The yields of MPDA, BHMO, BrPE, and other products were analyzed by ¹ H-NMR (measurement solvent: heavy water), and were 2%, 0%, 57%, and 41%, respectively. At a reaction liquid temperature of 95° C., MPDA reacted with HBr, and BHMO could not be converted to BrPE while leaving MPDA.

[Reference Example 2-2] Synthesis of MPDA (Step B2: Reaction solution temperature 95°C)
578 parts by mass of the solution containing the product obtained in Reference Example 2-1 was added to a three-neck flask equipped with a reflux condenser, and the mixture was stirred for 10 minutes at a reaction temperature of 95° C. in an oil bath at 110° C. With the reaction temperature at 95° C., 160 parts by mass (2.0 molar equivalents) of a 25% by mass aqueous sodium hydroxide solution was added, and the mixture was stirred for 30 minutes at a reaction temperature of 95° C. The reactor was removed from the oil bath and cooled to room temperature, and the yields of MPDA, BHMO, and other products were analyzed by ¹ H-NMR (measurement solvent: heavy water), and were 23%, 32%, and 45%, respectively. The yield of MPDA obtained in this reaction was 23%, and the yield of MPDA was low.

[Example 6-1] Synthesis of brominated pentaerythritol having an acetyl group 304 parts by mass of pentaerythritol tetraacetate was placed in a three-neck flask equipped with a reflux condenser, and dissolved in a mixture of 120 parts by mass (2.0 molar equivalents) of acetic acid and 510 parts by mass (5.0 molar equivalents) of acetic anhydride. Furthermore, 169 parts by mass (1.0 molar equivalents) of 48% by mass of hydrobromic acid was added, and the reaction solution was stirred at a temperature of 118°C for 5 hours in a 130°C oil bath to carry out a bromination reaction. The reflux condenser was removed, and the equipment was changed to one equipped with a connecting tube, a cooling tube, and a flask, and acetic acid and unreacted hydrogen bromide were distilled off under a reduced pressure of 200 Torr. The flask was removed from the oil bath, returned to room temperature, and then returned to normal pressure with nitrogen gas. The bromination rate was analyzed by ^13C -NMR (measurement solvent: deuterated ortho-dichlorobenzene) based on the integral value of quaternary carbon (40 to 43 ppm, TMS standard), and it was confirmed that 35% of the product was non-brominated, 55% was monobrominated (a compound in which R ¹ , R ² and R ³ in the above formula (1) are acetyl groups, and X is Br), and 10% was dibrominated. The amount of the product obtained was 322 parts by mass.

[Example 6-2] Synthesis of MPDA (Step B1: Reaction solution temperature 70°C)
461 parts by mass of ethanol was added to a three-neck flask containing 322 parts by mass of the mixture of brominated pentaerythritol having acetyl groups obtained in Example 6-1, and the mixture was stirred and dissolved, and the flask was placed in an oil bath at 80° C., and 1600 parts by mass (6.0 molar equivalents) of a 15% by mass ethanol solution of sodium hydroxide was gradually added so as to maintain the reaction liquid temperature at 70° C. After the addition, the mixture was stirred for 1 hour at 70° C. After cooling to room temperature, the yields of MPDA, BHMO and other products were analyzed by ¹ H-NMR (measurement solvent: deuterium oxide) to find that they were 40%, 10% and 50%, respectively, and MPDA was obtained with high selectivity to BHMO.

Claims (6)

A method for producing 2-methylene-1,3-propanediol, comprising a step of reacting a compound represented by the following formula (1) with a base:

In the above formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom or an acyl group having 2 to 19 carbon atoms, except when R ¹ , R ² and R ³ are all hydrogen atoms. X is a chlorine atom, a bromine atom or an iodine atom . The method for producing 2-methylene-1,3-propanediol according to claim 1, wherein the reaction step is carried out at a temperature of 40°C or higher and 120°C or lower. The method for producing 2-methylene-1,3-propanediol according to claim 1 or 2, wherein X is a bromine atom. The method for producing 2-methylene-1,3-propanediol according to any one of claims 1 to 3, wherein R ¹ , R ² and R ³ are each independently a hydrogen atom or an acetyl group. The method for producing 2-methylene-1,3-propanediol according to any one of claims 1 to 4, further comprising a step of obtaining a compound represented by formula (1) by esterification of a compound represented by formula (2) below, prior to the reacting step:

In the above formula (2), X is a chlorine atom, a bromine atom , or an iodine atom . The method for producing 2-methylene-1,3-propanediol according to any one of claims 1 to 5, further comprising: a step of mixing hydrogen halide with a solution containing the product obtained in the reacting step at a temperature of 30°C or less ; and a step of mixing a base with the solution that has been subjected to the step of mixing hydrogen halide.