JP7440862B2 - Catalyst for carboxylic acid ester synthesis and method for producing carboxylic acid ester - Google Patents

Description

The present invention relates to a catalyst for synthesizing carboxylic acid esters and a method for producing carboxylic acid esters.

Carboxylic acid esters are used in various fields such as pharmaceuticals, fragrances, and chemical products. As a method for producing a carboxylic ester, for example, a method of performing a transesterification reaction between a methyl ester and an alcohol to obtain a carboxylic ester is used. A catalyst is used in the transesterification reaction. Examples of catalysts for the transesterification reaction include those containing organic onium salts of phenols having a substituent at least one ortho position of the phenolic hydroxyl group (see, for example, Patent Document 1). In addition, in the presence of a magnesium alkoxide represented by the general formula Mg(OR) ₂ (where OR is an alkoxy group), (meth)acrylic acid ester and 2-methyl-2-hydroxy-1-propyl By transesterifying alcohol and/or 3-methyl-3-hydroxy-1-butyl alcohol, 2-methyl-2-hydroxy-1-propyl (meth)acrylate and/or 3-methyl-3-hydroxy- It is known that 1-butyl (meth)acrylate can be produced (see, for example, Patent Document 2).

Japanese Patent Application Publication No. 2016-203171 Japanese Patent Application Publication No. 2018-135285

However, when a carboxylic acid ester is produced by transesterifying a (meth)acrylic acid ester and a monohydric alcohol using a magnesium alkoxide whose alkoxy group has 8 or more carbon atoms, Michael addition and the raw material It was found that there were many side reactions such as polymerization of monomers, and the selectivity of the target carboxylic acid ester was low, resulting in poor selectivity. Note that the selectivity here refers to the ratio of the target product to the total amount of the product.

The present invention has been made in view of the above circumstances, and includes suppressing side reactions such as Michael addition and polymerization of raw material monomers in the transesterification reaction between (meth)acrylic acid ester and monohydric alcohol. It is an object of the present invention to provide a catalyst for synthesizing a carboxylic acid ester and a method for producing the carboxylic acid ester, which has excellent selectivity for the target carboxylic acid ester.

The present invention has the following aspects.
[1] A catalyst for synthesizing a carboxylic acid ester for obtaining a carboxylic acid ester by performing a transesterification reaction between a (meth)acrylic acid ester and a monohydric alcohol, which comprises Mg(OEt) ₂ or Mg(Ot-Bu ) A catalyst for synthesizing a carboxylic acid ester, consisting of a magnesium alkoxide represented by ₂ .
[2] In the presence of a magnesium alkoxide represented by Mg(OEt) ₂ or Mg(Ot-Bu) ₂ , a (meth)acrylic ester and a monohydric alcohol are transesterified to produce a carboxylic ester. A method for producing a carboxylic acid ester.
[ 3 ] The method for producing a carboxylic acid ester according to [ 2 ], wherein the reaction temperature is -20°C to 100°C.

According to the present invention, side reactions such as Michael addition and polymerization of raw material monomers are suppressed in the transesterification reaction between (meth)acrylic acid ester and monohydric alcohol, and the selectivity of the target carboxylic acid ester is improved. It is possible to provide an excellent catalyst for synthesizing a carboxylic acid ester and a method for producing a carboxylic acid ester.

Embodiments of the catalyst for synthesizing carboxylic esters and the method for producing carboxylic esters of the present invention will be described.
It should be noted that the present embodiment is specifically explained in order to better understand the gist of the invention, and is not intended to limit the invention unless otherwise specified.

[Catalyst for carboxylic acid ester synthesis]
The catalyst for synthesizing a carboxylic acid ester according to the present embodiment is a catalyst for synthesizing a carboxylic acid ester for obtaining a carboxylic acid ester by performing a transesterification reaction between a (meth)acrylic acid ester and a monohydric alcohol, and is a general catalyst for synthesizing a carboxylic acid ester. It consists of a magnesium alkoxide represented by the formula Mg(OR) ₂ (where OR is an alkoxy group having less than 8 carbon atoms). The R's in Mg(OR) ₂ may be the same or different, but from the viewpoint of easy availability, it is preferable that they are the same.

Examples of the alkoxy group having less than 8 carbon atoms include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, iso-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, Examples include hexyloxy group and heptyloxy group. Among these, as the alkoxy group, from the viewpoint of high reaction selectivity, an alkoxy group having 6 or less carbon atoms is preferable, and an alkoxy group having 4 or less carbon atoms is more preferable. On the other hand, from the viewpoint of similarly high reaction selectivity, the alkoxy group is preferably an alkoxy group having 1 or more carbon atoms, and more preferably an alkoxy group having 2 or more carbon atoms. Particularly preferred alkoxy groups include ethoxy and tert-butoxy groups.

For the above reasons, magnesium ethoxide (Mg(OEt) ₂ ) or magnesium t-butoxide (Mg(Ot-Bu) ₂ ) is preferable as the magnesium alkoxide because of its excellent catalytic activity.

According to the catalyst for carboxylic acid ester synthesis according to the present embodiment, side reactions such as Michael addition and polymerization of raw material monomers can be suppressed in the transesterification reaction between (meth)acrylic acid ester and monohydric alcohol, and Excellent selectivity for carboxylic acid esters. Although the detailed mechanism of this is not clear, magnesium alkoxide systematically forms a monomer, dimer, or trimer or higher multimer, and at the same time activates the carbonyl of the methacrylate ester, alcohol This is thought to be because it can activate the. In particular, for alkoxy groups with less than 8 carbon atoms, the abundance ratio of monomers and dimers is high in the reaction system, so the activated methacrylic acid ester and alcohol are located nearby, reducing side reactions. At the same time, it is thought that the catalytic activity is improved.

[Method for producing catalyst for carboxylic acid ester synthesis]
Magnesium alkoxide can be obtained, for example, by adding an excess amount of alcohol corresponding to the alkoxy group of the desired magnesium alkoxide to activated magnesium metal. Magnesium alkoxide can also be obtained by adding a corresponding alcohol to magnesium methoxide (Mg(OMe) ₂ ) and distilling off methanol as a by-product.

[Method for producing carboxylic acid ester]
The method for producing a carboxylic acid ester according to the present embodiment includes a method for producing a carboxylic acid ester in the presence of a magnesium alkoxide represented by the general formula Mg(OR) ₂ (where OR is an alkoxy group having less than 8 carbon atoms). ) This is a method in which a carboxylic ester is obtained by carrying out a transesterification reaction between an acrylic ester and a monohydric alcohol.

The details of the method for producing a carboxylic acid ester according to the present embodiment will be described below, but the method of this embodiment is limited to the extent that the carboxylic acid ester can be produced by the transesterification reaction between a (meth)acrylic acid ester and a monohydric alcohol. The (meth)acrylic acid ester and the monohydric alcohol may be reacted by any procedure.
First, a predetermined amount of dried molecular sieve 5A, magnesium alkoxide represented by the general formula Mg(OR) ₂ , and (meth)acrylic acid ester are added to a reaction container such as a flask, and the mixture is stirred at room temperature (25°C). ) After stirring for 1 to 5 minutes, monohydric alcohol is added to obtain a suspension.
Next, the suspension is stirred at a predetermined reaction temperature for 30 minutes to 96 hours to perform a transesterification reaction between the (meth)acrylic acid ester and the monohydric alcohol, and then the suspension is purified, A carboxylic acid ester is obtained.

There are no particular restrictions on the (meth)acrylic ester, but it is preferably a (meth)acrylic ester in which the ester moiety has 1 or more carbon atoms and 10 or less carbon atoms, and in particular, the ester moiety has 6 or less carbon atoms. It is more preferable to be a (meth)acrylic ester of, particularly preferably a (meth)acrylic ester in which the ester moiety has 2 or less carbon atoms, and among them, methyl methacrylate, methyl acrylate, etc. are most preferable. .

Monohydric alcohols include primary alcohols, secondary alcohols, and tertiary alcohols. Although there are no particular restrictions on the primary alcohol, it is preferably a primary alcohol with 2 or more carbon atoms in order to facilitate separation from the alcohol produced by the transesterification reaction. In order to reduce the burden of refining the acid ester, a primary alcohol having 30 or less carbon atoms is preferable. Examples of such primary alcohols include methanol, ethanol, propan-1-ol, butan-1-ol, pentan-1-ol, hexan-1-ol, heptan-1-ol, and octan-1-ol. ol, nonan-1-ol, decan-1-ol, undecane-1-ol, dodecan-1-ol, tridecan-1-ol, tetradecane-1-ol, pentadecane-1-ol, hexadecane-1-ol, Heptadecan-1-ol, octadecane-1-ol, nonadecan-1-ol, icosan-1-ol, heneicosan-1-ol, docosan-1-ol, tricosan-1-ol, tetracosan-1-ol, pentacosan-1-ol 1-ol, hexacosan-1-ol, heptacosan-1-ol, octacosan-1-ol, nonacosan-1-ol, triacontan-1-ol, policosanol, 2-methyl:2-methylpropan-1-ol, 3-Methyl: 3-methylbutan-1-ol and the like. Among these, the primary alcohol is more preferably a primary alcohol having 3 or more carbon atoms, particularly preferably a primary alcohol having 4 or more carbon atoms, and on the other hand, a primary alcohol having 20 or less carbon atoms. A primary alcohol is more preferable, and a primary alcohol having 10 or less carbon atoms is particularly preferable.

There are no particular restrictions on the secondary alcohol, but it is preferably a secondary alcohol with 3 or more carbon atoms, more preferably a secondary alcohol with 4 or more carbon atoms, and a secondary alcohol with 5 or more carbon atoms. Particularly preferred is a secondary alcohol; on the other hand, in order to reduce the burden of refining the target carboxylic ester, a secondary alcohol with a carbon number of 30 or less is preferred, and a secondary alcohol with a carbon number of 25 or less is preferred. A secondary alcohol is more preferable, and a secondary alcohol having 20 or less carbon atoms is particularly preferable. Examples of such secondary alcohols include propan-2-ol, butan-2-ol, pentan-2-ol, hexan-2-ol, cyclohexanol, heptan-2-ol, and 2-methyl:2-ol. -methylbutan-1-ol and the like.
The tertiary alcohol is not particularly limited, but it is preferably a tertiary alcohol with 4 or more carbon atoms. It is preferably a tertiary alcohol having 25 or less carbon atoms, more preferably a tertiary alcohol having 25 or less carbon atoms, and particularly preferably a tertiary alcohol having 20 or less carbon atoms. Examples of such tertiary alcohols include 1-adamantanol and tert-butanol.

The following formula (1) shows a chemical formula related to the transesterification reaction between a methacrylic acid ester and a monohydric alcohol. The following formula (2) shows a chemical formula related to the transesterification reaction between an acrylic ester and a monohydric alcohol.

In the above formulas (1) and (2), R1 and R3 are each an alkyl group having 1 or more carbon atoms. Among these, each of R1 and R3 is preferably an alkyl group having 1 or more carbon atoms, on the other hand, it is preferably an alkyl group having 10 or less carbon atoms, more preferably an alkyl group having 6 or less carbon atoms, and 2 or less carbon atoms. Particularly preferred is an alkyl group.
In the above formulas (1) and (2), R2 represents an alkyl group. Among these, when R2-OH is a primary alcohol, R2 is preferably an alkyl group having 2 or more carbon atoms, more preferably an alkyl group having 3 or more carbon atoms, and an alkyl group having 4 or more carbon atoms. It is particularly preferably an alkyl group having 30 or less carbon atoms, more preferably an alkyl group having 20 or less carbon atoms, and particularly preferably an alkyl group having 20 or less carbon atoms.

When R2-OH is a secondary alcohol, R2 is preferably an alkyl group having 3 or more carbon atoms, more preferably an alkyl group having 4 or more carbon atoms, and preferably an alkyl group having 5 or more carbon atoms. is particularly preferred; on the other hand, an alkyl group having 30 or less carbon atoms is preferred, an alkyl group having 25 or less carbon atoms is even more preferred, and an alkyl group having 20 or less carbon atoms is particularly preferred.

When R2-OH is a tertiary alcohol, R2 is preferably an alkyl group having 4 or more carbon atoms, while preferably an alkyl group having 30 or less carbon atoms, and preferably an alkyl group having 25 or less carbon atoms. More preferably, it is an alkyl group having 20 or less carbon atoms.

The blending ratio of (meth)acrylic acid ester and monohydric alcohol, in other words, the molar ratio of (meth)acrylic acid ester to monohydric alcohol is not particularly limited, but is preferably 2 or more, It is more preferably 5 or more, while it is preferably 30 or less, and more preferably 10 or less. When the blending ratio of the (meth)acrylic ester and the monohydric alcohol is 2 or more, the transesterification reaction between the (meth)acrylic ester and the monohydric alcohol tends to proceed efficiently. On the other hand, when the blending ratio is 30 or less, the desired product can be obtained with high productivity. (Meth)acrylic ester and monohydric alcohol may be used alone or in combination of two or more. When two or more types are used, it is preferable that the total amount falls within the above range.

The transesterification reaction temperature between the (meth)acrylic ester and the monohydric alcohol is preferably -20°C or higher and 100°C or lower, more preferably 10°C or higher, and on the other hand, 80°C or lower. It is more preferable that there be. When the reaction temperature is −20° C. or higher, the transesterification reaction between the (meth)acrylic ester and the monohydric alcohol tends to proceed efficiently. When the reaction temperature is 100° C. or less, energy consumption due to heating can be suppressed.

The transesterification reaction between a (meth)acrylic ester and an alcohol may be performed in a solvent or without a solvent. However, in consideration of productivity and the burden of solvent recovery, it is preferable to carry out the process without a solvent. Note that "solvent-free" means that the amount of solvent relative to alcohol is 30% by mass or less.

On the other hand, when using a solvent, there are no particular restrictions on the solvent, but examples include benzene, toluene, xylene, n-hexane, cyclohexane, n-heptane, n-octane, n-nonane, n-decane, , 4-dioxane, tetrahydrofuran, tetrahydropyran, anisole, methyl-tert-butyl ether, dibutyl ether, diphenyl ether, ethylene glycol monomethyl ether, ethylene glycol mono-n-butyl ether, acetone, methyl ethyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, Examples include cyclohexanone, 2-methylcyclohexanone, dimethylformaldehyde, dimethylacetamide and the like. One type of solvent may be used alone, or two or more types may be used in combination.

The molar ratio of magnesium alkoxide to monohydric alcohol is not particularly limited, but in order to efficiently promote the transesterification reaction, it is preferably 0.001 or more, more preferably 0.005 or more, It is particularly preferably at least .01, on the other hand, in order to reduce the purification load after the reaction, it is preferably at most 0.3, more preferably at most 0.2, and at most 0.1. is particularly preferred.
One type of magnesium alkoxide may be used alone, or two or more types may be used in combination. When using two or more types in combination, it is preferable that the total amount falls within the above range. Note that catalysts other than the magnesium alkoxide may be used in combination as long as the effects of the present invention are not impaired.

Other compounds than those mentioned above may be present in the reaction system. For example, polymerization inhibitors may be used to inhibit polymerization. Note that the polymerization inhibitor is not particularly limited and includes known polymerization inhibitors.

Methods for purifying the above suspension include, but are not particularly limited to, purification using a silica gel column (mobile phase: hexane/methyl acetate), washing, filtration, distillation, etc. There are no particular limitations, and any known method may be used.

According to the method for producing a carboxylic acid ester according to the present embodiment, side reactions such as Michael addition and polymerization of raw material monomers are suppressed in the transesterification reaction between a (meth)acrylic acid ester and a monohydric alcohol, and the desired Excellent selectivity for carboxylic acid esters.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1]
(Production of carboxylic acid ester)
In a flask, 400 mg of dried molecular sieve 5 Å, 11.4 mg (0.1 mol) of magnesium ethoxide (Mg(OEt) ₂ ), 1.49 mL (14 mmol) of methyl methacrylate, and copper dimethyldithiocarbamate as a polymerization inhibitor. (II) 1.2 mg (0.004 mmol) and 18.8 mg (0.2 mmol) of dimethylsulfone as an internal standard were added, and the mixture was stirred at room temperature (25°C) for 3 minutes, and then benzyl alcohol (hereinafter referred to as 0.206 mL (2 mmol) was added to obtain a suspension. The amount of Mg(OEt) ₂ added to benzyl alcohol was 5 mol% in molar ratio.
The suspension was then stirred at room temperature (25°C) for 3 hours.
Next, the suspension was purified with a silica gel column (mobile phase: hexane/methyl acetate) to obtain the compound of Example 1.
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 1.97 (s, 3H), 5.20 (s, 2H), 5.59 (s, 1H), 6.16 (s , 1H), 7.30-7.40 (m, 5H).
¹³ C-NMR (100 MHz, solvent: CDCl ₃ ) δ (ppm): 18.5, 66.5, 125.9, 128.1 (2C), 128.2, 128.6 (2C), 136.2 , 136.3, 167.3.
IR (neat) 3034, 2957, 1719, 1637, 1454, 1319, 1294 ^{, 1159 cm −1} .
HRMS (DART+) calcd for C ₁₁ H ₁₃ O ₂ [M+H] ⁺ 177.0916, found 177.0912.
From the above measurement data, it was confirmed that benzyl methacrylate represented by the following formula (3) was obtained. Note that the following formula (4) shows a reaction formula for synthesizing benzyl methacrylate by transesterification of methyl methacrylate and benzyl alcohol.
Furthermore, the yield and selectivity of benzyl methacrylate were calculated from the proportion of the target product benzyl methacrylate in the total amount of the product, and the yield was 40% and the selectivity was 100%. In addition, after separating the desired product from by-products by silica gel column chromatography, the selectivity was calculated by directly measuring the weight of the desired product using an electronic balance.

[Example 2]
(Production of carboxylic acid ester)
Example 1 except that magnesium t-butoxide (Mg(Ot-Bu) ₂ ) was used instead of magnesium ethoxide (Mg(OEt) ₂ ) and the suspension was stirred at room temperature (25° C.) for 2 minutes. Benzyl methacrylate was obtained in the same manner as above.
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 1.97 (s, 3H), 5.20 (s, 2H), 5.59 (s, 1H), 6.16 (s , 1H), 7.30-7.40 (m, 5H).
¹³ C-NMR (100 MHz, solvent: CDCl ₃ ) δ (ppm): 18.5, 66.5, 125.9, 128.1 (2C), 128.2, 128.6 (2C), 136.2 , 136.3, 167.3.
IR (neat) 3034, 2957, 1719, 1637, 1454, 1319, 1294 ^{, 1159 cm −1} .
HRMS (DART+) calcd for C ₁₁ H ₁₃ O ₂ [M+H] ⁺ 177.0916, found 177.0912.
From the above measurement data, it was confirmed that benzyl methacrylate represented by the above formula (3) was obtained. In addition, when the yield and selectivity of benzyl methacrylate were calculated, the yield was 95% and the selectivity was 100%.

[Comparative example 1]
(Production of carboxylic acid ester)
Potassium t-butoxide (hereinafter sometimes abbreviated as "KOt-Bu") was used as a catalyst instead of magnesium ethoxide (Mg(OEt) ₂ ), and the suspension was heated at room temperature (25°C) for 30 minutes. The reaction was carried out in the same manner as in Example 1 except for stirring.
However, methyl methacrylate polymerized soon after the reaction started, and the transesterification reaction between methyl methacrylate and benzyl alcohol did not occur. That is, the yield of benzyl methacrylate was 0%. Therefore, the selection rate was not evaluated.

Table 1 shows the catalyst, ester, and alcohol used in Example 1, Example 2, and Comparative Example 1, and the amount of catalyst, reaction temperature, reaction time, and selectivity in Example 1, Example 2, and Comparative Example 1. . In Table 1, the molar ratio of catalyst is the amount of catalyst added to benzyl alcohol expressed as a molar ratio.

From the results of Example 1, it was found that magnesium ethoxide (Mg(OEt) ₂ ) has excellent selectivity because no by-products are generated. From the results of Example 2, it was found that magnesium t-butoxide (Mg(Ot-Bu) ₂ ) has excellent selectivity because no by-products are produced. On the other hand, the results of Comparative Example 1 revealed that potassium t-butoxide had poor selectivity.

[Example 3]
(Production of carboxylic acid ester)
In a flask, 400 mg of dried molecular sieve 5Å, 11.4 mg (0.1 mol) of magnesium ethoxide (Mg(OEt) ₂ ), 1.26 mL (14 mmol) of methyl acrylate, and copper dimethyldithiocarbamate as a polymerization inhibitor. 1.2 mg (0.004 mmol) of (II) and 18.8 mg (0.2 mmol) of dimethylsulfone as an internal standard were added, and the mixture was stirred at room temperature (25°C) for 3 minutes, followed by 0.206 mL of benzyl alcohol ( 2 mmol) was added to obtain a suspension. The amount of Mg(OEt) ₂ added to benzyl alcohol was 5 mol% in molar ratio.
The suspension was then stirred at room temperature (25°C) for 3 hours.
Next, the suspension was purified using a silica gel column (mobile phase: hexane/methyl acetate) to obtain the compound of Example 3.
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 5.19 (s, 2H), 5.84 (dd, J = 10.4, 1.6 Hz, 1H), 6.16 ( dd, J = 17.4, 10.5 Hz, 1H), 6.44 (dd, J = 17.2, 1.4 Hz, 1H), 7.31-7.41 (m, 5H).
¹³ C-NMR (100 MHz, solvent: CDCl ₃ ) δ (ppm): 66.4, 128.3 (2C), 128.4 (2C), 128.7 (2C), 131.2, 135.9, 166.1.
IR (neat) 3034, 2954, 1953, 1725, 1634, 1455, 1406, 1295, 1269, 1186, 1049 ^{cm −1} .
HRMS (FAB+) calcd for C ₁₀ H ₁₀ O ₂ [M] ⁺ 162.0681, found 162.0680.
From the above measurement data, it was confirmed that benzyl acrylate represented by the following formula (5) was obtained. In addition, when the yield and selectivity of benzyl acrylate were calculated, the yield was 92% and the selectivity was 100%.

[Example 4]
(Production of carboxylic acid ester)
Example except that magnesium t-butoxide (Mg(Ot-Bu) ₂ ) was used instead of magnesium ethoxide (Mg(OEt) ₂ ), and the stirring time (reaction time) of the suspension was 30 minutes. Benzyl acrylate was obtained in the same manner as in Example 3.
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 5.19 (s, 2H), 5.84 (dd, J = 10.4, 1.6 Hz, 1H), 6.16 ( dd, J = 17.4, 10.5 Hz, 1H), 6.44 (dd, J = 17.2, 1.4 Hz, 1H), 7.31-7.41 (m, 5H).
¹³ C-NMR (100 MHz, solvent: CDCl ₃ ) δ (ppm): 66.4, 128.3 (2C), 128.4 (2C), 128.7 (2C), 131.2, 135.9, 166.1.
IR (neat) 3034, 2954, 1953, 1725, 1634, 1455, 1406, 1295, 1269, 1186, 1049 ^{cm −1} .
HRMS (FAB+) calcd for C ₁₀ H ₁₀ O ₂ [M] ⁺ 162.0681, found 162.0680.
From the above measurement data, it was confirmed that benzyl acrylate represented by the above formula (5) was obtained. In addition, when the yield and selectivity of benzyl acrylate were calculated, the yield was 99% and the selectivity was 100%.

[Comparative example 2]
(Production of carboxylic acid ester)
The same method as Example 3 except that sodium methoxide (NaOMe) was used as a catalyst instead of magnesium ethoxide (Mg(OEt) ₂ ) and the suspension stirring time (reaction time) was 30 minutes. Benzyl acrylate was obtained. In addition, when the yield and selectivity of benzyl acrylate were calculated, the yield was 43% and the selectivity was 46%.

[Comparative example 3]
(Production of carboxylic acid ester)
Same as Example 3 except that potassium t-butoxide (KOt-Bu) was used as a catalyst instead of magnesium ethoxide (Mg(OEt) ₂ ) and the stirring time (reaction time) of the suspension was 30 minutes. Benzyl acrylate was obtained in a similar manner. In addition, when the yield and selectivity of benzyl acrylate were calculated, the yield was 20% and the selectivity was 25%.

[Comparative example 4]
(Production of carboxylic acid ester)
Same as Example 3 except that diisopropoxycalcium (hereinafter sometimes abbreviated as "Ca(i-OPr) ₂ ") was used as a catalyst instead of magnesium ethoxide (Mg(OEt) ₂ ). Benzyl acrylate was obtained by the method. In addition, when the yield and selectivity of benzyl acrylate were calculated, the yield was 57% and the selectivity was 82%.

[Comparative example 5]
(Production of carboxylic acid ester)
The reaction was carried out in the same manner as in Example 3, except that iron ethoxide (hereinafter sometimes abbreviated as "Fe(OEt) ₃ ") was used as a catalyst instead of magnesium ethoxide (Mg(OEt) ₂ ). I did it.
However, transesterification reaction between methyl acrylate and benzyl alcohol did not occur. That is, the yield of benzyl acrylate was 0%. Therefore, the selection rate was not evaluated.

[Comparative example 6]
(Production of carboxylic acid ester)
The reaction was carried out in the same manner as in Example 3, except that zinc methoxide (hereinafter sometimes abbreviated as "Zn(OMe) ₂ ") was used as a catalyst instead of magnesium ethoxide (Mg(OEt) ₂ ). I did it.
However, transesterification reaction between methyl acrylate and benzyl alcohol did not occur. That is, the yield of benzyl acrylate was 0%. Therefore, the selection rate was not evaluated.

“Comparative Example 7”
(Production of carboxylic acid ester)
Same as Example 3 except that titanium n-butoxide (hereinafter sometimes abbreviated as "Ti(On-Bu) ₄ ") was used as a catalyst instead of magnesium ethoxide (Mg(OEt) ₂ ). The reaction was carried out by the method of
However, transesterification reaction between methyl acrylate and benzyl alcohol did not occur. That is, the yield of benzyl acrylate was 0%. Therefore, the selection rate was not evaluated.

[Comparative example 8]
(Production of carboxylic acid ester)
Same as Example 3 except that lanthanum isopropoxide (hereinafter sometimes abbreviated as "La(i-OPr) ₃ ") was used as a catalyst instead of magnesium ethoxide (Mg(OEt) ₂ ). Benzyl acrylate was obtained by the method. In addition, when the yield and selectivity of benzyl acrylate were calculated, the yield was 65% and the selectivity was 65%.

The catalyst, ester, and alcohol used in Example 3, Example 4, and Comparative Examples 3 to 8, and the amount of catalyst, reaction temperature, reaction time, and Table 2 shows the selectivity. In Table 2, the molar ratio of catalyst is the amount of catalyst added to benzyl alcohol expressed as a molar ratio.

From the results of Example 3, it was found that magnesium ethoxide (Mg(OEt) ₂ ) has excellent selectivity because no by-products are generated. From the results of Example 4, it was found that magnesium t-butoxide (Mg(Ot-Bu) ₂ ) has excellent selectivity because no by-products are generated. Furthermore, it has been found that magnesium t-butoxide (Mg(Ot-Bu) ₂ ) can complete the synthesis of benzyl acrylate in a shorter time than magnesium ethoxide (Mg(OEt) ₂ ). On the other hand, from the results of Comparative Example 2, it was found that sodium methoxide was inferior in selectivity due to the production of by-products. From the results of Comparative Example 3, it was found that potassium t-butoxide had poor selectivity. From the results of Comparative Example 4, it was found that diisopropoxycalcium was inferior in selectivity. From the results of Comparative Example 5, it was found that iron ethoxide was inferior in selectivity. From the results of Comparative Example 6, it was found that zinc methoxide had poor selectivity. From the results of Comparative Example 7, it was found that titanium n-butoxide had poor selectivity. From the results of Comparative Example 8, it was found that lanthanum isopropoxide had poor selectivity.

[Example 5]
(Production of carboxylic acid ester)
In a flask, 400 mg of dried molecular sieve 5Å, 11.4 mg (0.1 mol) of magnesium ethoxide (Mg(OEt) ₂ ), 4.23 mL (40 mmol) of methyl methacrylate, and copper dimethyldithiocarbamate as a polymerization inhibitor. 1.2 mg (0.004 mmol) of (II) and 18.8 mg (0.2 mmol) of dimethylsulfone as an internal standard were added, and the mixture was stirred at room temperature (25°C) for 3 minutes, followed by 0.206 mL of benzyl alcohol ( 2 mmol) was added to obtain a suspension. The amount of Mg(OEt) ₂ added to benzyl alcohol was 5 mol% in molar ratio.
The suspension was then stirred at 100°C for 3 hours.
Next, the suspension was purified using a silica gel column (mobile phase: hexane/methyl acetate) to obtain the compound of Example 3.
The results of ¹ H-NMR, ¹³ C-NMR, IR and HRMS analysis of the obtained compound were similar to those in Example 1.
From the measurement data, it was confirmed that benzyl methacrylate represented by the above formula (1) was obtained.
In addition, when the yield and selectivity of benzyl methacrylate were calculated, the yield was 89% and the selectivity was 100%.

[Example 6]
(Production of carboxylic acid ester)
The compound of Example 6 was obtained in the same manner as in Example 5, except that magnesium t-butoxide (Mg(Ot-Bu) ₂ ) was used instead of magnesium ethoxide (Mg(OEt) ₂ ).
The results of ¹ H-NMR, ¹³ C-NMR, IR and HRMS analysis of the obtained compound were similar to those in Example 1.
From the measurement data, it was confirmed that benzyl methacrylate represented by the above formula (1) was obtained.
In addition, when the yield and selectivity of benzyl methacrylate were calculated, the yield was 88% and the selectivity was 100%.

Table 3 shows the catalyst, ester, and alcohol used in Example 5 and Example 6, as well as the amount of catalyst, reaction temperature, reaction time, and selectivity in Example 5 and Example 6. In Table 3, the molar ratio of catalyst is the amount of catalyst added to benzyl alcohol expressed as a molar ratio.

From the results of Example 5 and Example 6, it is clear that magnesium ethoxide (Mg(OEt) ₂ ) and magnesium ethoxide (Mg(OEt) ₂ ) produce no by-products even when the reaction temperature is 100°C. It was found that the selectivity is excellent because no product is generated.

[Example 7]
(Production of carboxylic acid ester)
0.212 mL (2 mmol) of cyclohexanol (hereinafter sometimes abbreviated as "ROH-1") was used in place of benzyl alcohol, and magnesium t-butoxide (in place of magnesium ethoxide (Mg(OEt) ₂ ) was used. The compound of Example 7 was obtained in the same manner as in Example 1 except that Mg(Ot-Bu) ₂ ) was used.
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 1.20-1.61 (m, 6H), 1.67-1.80 (m, 2H), 1.80-1. 91 (m, 2H), 1.94 (s, 3H), 4.76-4.92 (m, 1H), 5.53 (t, J = 1.5Hz, 1H), 6.09 (d, J=0.6Hz, 1H).
¹³ C-NMR (100 MHz, solvent: CDCl ₃ ) δ (ppm): 18.3, 23.5 (2C), 25.4, 31.4 (2C), 72.5, 124.8, 136.9 , 166.8.
IR (neat) 2936, 2858, 1717, 1450, 1169, ^{1016 cm −1} .
HRMS (FAB+) calcd for C ₁₀ H ₁₆ NaO ₂ [M+Na] ⁺ 191.1048, found 191.1047.
From the above measurement data, it was confirmed that cyclohexyl methacrylate represented by the following formula (6) was obtained. In addition, when the yield and selectivity of cyclohexyl methacrylate were calculated, the yield was 99% and the selectivity was 100%.

[Example 8]
(Production of carboxylic acid ester)
0.212 mL (2 mmol) of cyclohexanol (ROH-1) was used instead of benzyl alcohol, and magnesium t-butoxide (Mg(Ot-Bu) ₂ ) was used instead of magnesium ethoxide (Mg(OEt) ₂ ). The compound of Example 8 was obtained in the same manner as in Example 3 except for the following.
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR, and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 1.20-1.61 (m, 6H), 1.74 (m, 2H), 1.88 (m, 2H), 4 .83 (m, 1H), 5.79 (dd, J = 10.8, 1.4Hz, 1H), 6.11 (dd, J = 17.2, 10.5Hz, 1H), 6.38 ( dd, J=17.6, 1.4Hz, 1H).
¹³ C-NMR (100 MHz, solvent: CDCl ₃ ) δ (ppm): 23.8 (2C), 25.5, 31.7 (2C), 72.8, 129.3, 130.2, 165.8 .
IR (neat) 2938, 2859, 1721, 1637, 1451, 1405, 1295, 1275, 1196, 1053 ^{cm −1} .
HRMS (FAB+) calcd for C ₉ H ₁₅ O ₂ [M+H] ⁺ 155.1072, found 155.1066.
From the above measurement data, it was confirmed that cyclohexyl acrylate represented by the following formula (7) was obtained. In addition, when the yield and selectivity of cyclohexyl acrylate were calculated, the yield was 99% and the selectivity was 100%.

[Example 9]
(Production of carboxylic acid ester)
0.236 g (2 mmol) of 1,6-hexanediol (hereinafter sometimes abbreviated as "ROH-2") was used instead of benzyl alcohol, and magnesium ethoxide (Mg(OEt) ₂ ) was used instead of magnesium ethoxide (Mg(OEt) 2 ). The compound of Example 9 was obtained in the same manner as in Example 1 except that t-butoxide (Mg(Ot-Bu) ₂ ) was used.
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 1.42-1.46 (m, 4H), 1.67-1.74 (m, 4H), 1.95 (s, 6H), 4.13-4.17 (m, 4H), 5.54-5.56 (m, 2H), 6.09-6.10 (m, 2H).
^13C -NMR (100MHz, solvent: CDCl ₃ ) δ (ppm): 18.4 (2C), 25.8 (2C), 28.6 (2C), 64.7 (2C), 125.3 (2C ), 136.5 (2C), 167.6 (2C).
IR (neat) 2939, 2861, 1719, 1637, 1454, 1321, 1297 ^{, 1166 cm −1} .
HRMS (DART+) calcd for C14H23O4 [M+H] ⁺ 255.1596, found 255.1597.
From the above measurement data, it was confirmed that hexane-1,6-diylbis(2-methyl acrylate) represented by the following formula (8) was obtained. Note that when the yield and selectivity of hexane-1,6-diylbis(2-methyl acrylate) were calculated, the yield was 80% and the selectivity was 100%.

[Example 10]
(Production of carboxylic acid ester)
0.236 g (2 mmol) of 1,6-hexanediol (ROH-2) was used instead of benzyl alcohol, and magnesium t-butoxide (Mg(Ot-Bu) was used instead of magnesium ethoxide (Mg(OEt) ₂ ). The compound of Example 10 was obtained in the same manner as in Example 3 except that ₂ ) was used.
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 1.41-1.44 (m, 4H), 1.66-1.73 (m, 4H), 4.16 (t, J=6.4Hz, 4H), 5.82 (dd, J=10.1, 1.4Hz, 2H), 6.12 (dd, J=17.4, 10.5Hz, 2H), 6.40 (dd, J=17.4, 1.4Hz, 2H).
^13C -NMR (100MHz, solvent: CDCl ₃ ) δ (ppm): 25.7 (2C), 28.6 (2C), 64.6 (2C), 128.6 (2C), 130.7 (2C ), 166.4 (2C).
IR (neat) 2941, 2862, 1718, 1636, 1620, 1467, 1409, 1274, ^{1197 cm −1} .
HRMS (DART+) calcd for C ₁₂ H ₁₉ O ₄ [M+H] ⁺ 227.1283, found 227.1284.
From the above measurement data, it was confirmed that hexane-1,6-diyl diacrylate (3r) represented by the following formula (9) was obtained. Note that when the yield and selectivity of hexane-1,6-diyl diacrylate (3r) were calculated, the yield was 99% and the selectivity was 100%.

[Example 11]
(Production of carboxylic acid ester)
Instead of benzyl alcohol, 0.300 g (2 mmol) of triethylene glycol (hereinafter sometimes abbreviated as "ROH-3") represented by the following formula (10) was used, and magnesium ethoxide (Mg(OEt) The compound of Example ₁₁ was obtained in the same manner as in Example 1 except that magnesium t-butoxide (Mg(Ot-Bu) ₂ ) was used instead of 2).
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 1.95 (s, 6H), 3.68 (s, 4H), 3.74-3.77 (m, 4H), 4 .29-4.32 (m, 4H), 5.57-5.59 (m, 2H), 6.13-6.14 (m, 2H).
¹³ C-NMR (100 MHz, solvent: CDCl ₃ ) δ (ppm): 18.4 (2C), 63.9 (2C), 69.3 (2C), 70.7 (2C), 125.9 (2C ), 136.2 (2C), 167.5 (2C).
IR (neat) 2955, 2874, 1719, 1637, 1454, 1319, 1297, 1171, 1043 ^{cm −1} .
HRMS (DART+) calcd for C ₁₄ H ₂₃ O ₆ [M+H] ⁺ 287.1495, found 287.1495.
From the above measurement data, it was confirmed that triethylene glycol dimethacrylate represented by the following formula (11) was obtained. In addition, when the yield and selectivity of triethylene glycol dimethacrylate were calculated, the yield was 96% and the selectivity was 100%.

[Example 12]
(Production of carboxylic acid ester)
0.300 g (2 mmol) of triethylene glycol (ROH-3) was used instead of benzyl alcohol, and magnesium t-butoxide (Mg(Ot-Bu) ₂ ) was used instead of magnesium ethoxide (Mg(OEt) ₂ ). A compound of Example 12 was obtained in the same manner as in Example 3 except that .
The measurement data of ¹ H-NMR, ¹³ C-NMR, IR and HRMS of the obtained compound are shown below.
¹ H-NMR data (400 MHz, solvent: CDCl ₃ ) δ (ppm): 3.68 (s, 4H), 3.74-3.76 (m, 4H), 4.31-4.33 (m, 4H), 5.84 (dd, J=10.6, 1.4Hz, 2H), 6.16 (dd, J=17.4, 10.6Hz, 2H), 6.43 (dd, J=17 .4, 1.4Hz, 2H).
^13C -NMR (100MHz, solvent: CDCl ₃ ) δ (ppm): 63.8 (2C), 69.3 (2C), 70.7 (2C), 128.4 (2C), 131.2 (2C) ), 166.3 (2C).
IR (neat) 2952, 2875, 1725, 1636, 1619, 1454, 1409, 1352, 1298, 1197, 1131, ^{1067 cm −1} .
HRMS (DART+) calcd for C ₁₂ H ₁₉ O ₆ [M+H] ⁺ 259.1182, found 259.1189.
From the above measurement data, it was confirmed that triethylene glycol diacrylate represented by the following formula (12) was obtained. In addition, when the yield and selectivity of triethylene glycol diacrylate were calculated, the yield was 92% and the selectivity was 100%.

Table 4 shows the catalysts, esters, and alcohols used in Examples 7 to 12, as well as the catalyst amounts, reaction temperatures, reaction times, and selectivities in Examples 7 to 12. In Table 4, the molar ratio of catalyst is the amount of catalyst added to methyl acrylate expressed as a molar ratio.

From the results of Examples 7 to 12, it was found that magnesium t-butoxide (Mg(Ot-Bu) ₂ ) has excellent selectivity because no by-products are generated.

Claims (3)

A catalyst for synthesizing a carboxylic acid ester for obtaining a carboxylic acid ester by carrying out a transesterification reaction between a (meth)acrylic acid ester and a monohydric alcohol, the catalyst comprising:
A catalyst for synthesizing carboxylic acid esters, consisting of a magnesium alkoxide represented by Mg(OEt) ₂ or Mg(Ot-Bu) ₂ . In the presence of a magnesium alkoxide represented by Mg(OEt) ₂ or Mg(Ot-Bu) ₂ , a (meth)acrylic ester is transesterified with a monohydric alcohol to obtain a carboxylic ester. Method for producing acid ester. The method for producing a carboxylic acid ester according to claim 2 , wherein the reaction temperature is -20°C to 100°C.