JP2021042171A - Method for producing carboxylic acid ester - Google Patents

Abstract

To provide a production method capable of obtaining a carboxylic acid ester from a reaction of a carboxylic acid with a hydroxy compound at a milder reaction temperature.SOLUTION: There is provided a method for producing a carboxylic acid ester capable of obtaining a carboxylic acid ester by reacting a carboxylic acid with a hydroxy compound in the presence of a catalyst containing a compound (A), wherein the compound (A) is a salt composed of an anion portion and a cation portion, the anion portion is an anion derived from a strong acid having at least one selected from the group consisting of a sulfonyl group and a sulfinyl group, the strong acid has at least one fluorine atom, the cation portion is at least one selected from the group consisting of an iron ion, a zinc ion, a lanthanoid ion and an yttrium ion.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a carboxylic acid ester.

As a method for producing a carboxylic acid ester, a method of esterifying a carboxylic acid with a hydroxy compound in the presence of a catalyst is known.

Non-Patent Document 1 describes a method for producing a carboxylic acid ester by reacting a carboxylic acid with a hydroxy compound in the presence of bis (2,4-pentanedionato) titanium (IV) oxide.

J. Org. Chem. 2005, Vol. 70, No. 21,8625.

However, it has been found that the catalyst described in Non-Patent Document 1 has a problem that the substrate that can be used is limited, the activity is low, and the selectivity is low. According to the study of the present inventor, for example, when this method is applied to the production of phenyl heptanate from enanthic acid and phenol, the reaction hardly proceeds. It was also found that the yield of the carboxylic acid ester was low (the selectivity of the carboxylic acid ester was low) even under relatively mild reaction conditions, or the reaction did not proceed at all.
Therefore, an object of the present invention is to provide a production method in which a carboxylic acid ester can be highly selected from a reaction between a carboxylic acid and a hydroxy compound under relatively mild reaction conditions.

As a result of intensive studies in view of the problems of the prior art, the present inventors have found that the above object can be achieved by carrying out the reaction in the presence of a specific catalyst, and have completed the present invention. .. That is, the present invention has the following aspects.

[1] Carboxylic acid and hydroxy compound
A method for producing a carboxylic acid ester, which comprises reacting in the presence of a catalyst containing the compound (A) to obtain a carboxylic acid ester.
The compound (A) is a salt composed of an anion portion and a cation portion.
The anion portion is an anion derived from a strong acid having at least one selected from the group consisting of a sulfonyl group and a sulfinyl group, and the strong acid has at least one fluorine atom.
A method for producing a carboxylic acid ester, wherein the cation portion is at least one selected from the group consisting of iron ion, zinc ion, lanthanoid ion, and yttrium ion.
[2] The method for producing a carboxylic acid ester according to [1], wherein the strong acid is at least one selected from the group consisting of perfluoroalkyl sulfonic acid and perfluoroalkyl sulfinic acid.
[3] The method for producing a carboxylic acid ester according to [1] or [2], wherein the carboxylic acid is (meth) acrylic acid.
[4] The method for producing a carboxylic acid ester according to any one of [1] to [3], wherein the hydroxy compound is at least one selected from alcohol.
[5] The method for producing a carboxylic acid ester according to any one of [1] to [3], wherein the hydroxy compound is at least one selected from phenols.

According to the present invention, it is an object of the present invention to provide a production method for obtaining a carboxylic acid ester from a reaction between a carboxylic acid and a hydroxy compound at a milder reaction temperature.

In the present specification, acrylic acid and methacrylic acid are collectively referred to as (meth) acrylic acid. In addition, acrylic acid ester and methacrylic acid ester are collectively referred to as (meth) acrylic acid ester.

〔carboxylic acid〕
In the method for producing a carboxylic acid ester of the present invention, the type and structure of the carboxylic acid as a raw material of the carboxylic acid ester are not limited. For example, the carboxylic acid ^{can be represented as "R 1} COOH", where R ¹ represents a hydrocarbon group which may have a substituent and has 1 to 30 carbon atoms which may have a substituent. It is preferably a hydrocarbon group. The hydrocarbon group may be linear, branched, or have a ring structure. Further, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. An unsaturated bond may be contained in the aliphatic hydrocarbon group. In addition, having a substituent means that it may have one or more arbitrary substituents, for example, having one or more of the following bonds, groups, atoms and the like. It means that it may be. Ester bond, amide bond, ether bond, sulfide bond, disulfide bond, urethane bond, nitro group, cyano group, ketone group, formyl group, acetal group, thioacetal group, sulfonyl group, halogen atom, silicon atom, phosphorus atom, etc. Can be mentioned. Further, as the carboxylic acid, a hydroxycarboxylic acid having a hydroxy group in the same molecule, a polycyclic carboxylic acid, a heterocyclic carboxylic acid composed of two or more kinds of elements, a polyvalent carboxylic acid and the like can be used. ..

The ^{number of carbon atoms of the hydrocarbon group represented by R 1} is preferably 1 to 30, more preferably 2 to 20, from the viewpoint of reactivity and availability of the carboxylic acid. The hydrocarbon group includes, for example, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, and a substituent. Examples thereof include an aryl group which may be used.

More specifically, the hydrocarbon group represented by R ¹ includes a vinyl group, an isopropenyl group, a t-butyl group, an n-hexyl group, a cyclohexyl group, a phenyl group and the like. Among these, R ¹ is preferably a vinyl group and an isopropenyl group. Specific examples of the carboxylic acid include (meth) acrylic acid, pivalic acid, enanthic acid, cyclohexanecarboxylic acid, benzoic acid, and monomethyl adipic acid. Among these, as the carboxylic acid, (meth) acrylic acid is preferable.

As the carboxylic acid, a commercially available one can be used, or one produced by a known method or the like can also be used. In addition, one type of carboxylic acid may be used alone, or two or more types may be used in combination.

The amount of the carboxylic acid used in the method for producing the carboxylic acid ester of the present invention is preferably 0.1 to 10 mol, more preferably 0.5 to 5 mol, per 1 mol of the hydroxy compound. The yield of the carboxylic acid ester can be increased by setting the amount of the carboxylic acid used to be equal to or higher than the above lower limit per 1 mol of the hydroxy compound. Further, by setting the amount of the carboxylic acid used to be equal to or less than the above upper limit value per 1 mol of the hydroxy compound, the load on the post-treatment step after the reaction can be reduced and the economic efficiency can be improved.

[Hydroxy compound]
In the method for producing a carboxylic acid ester of the present invention, the hydroxy compound used as a raw material for the carboxylic acid ester may be an organic compound having a hydroxy group, and the type and structure are not limited. For example, the hydroxy compound can be expressed as "R ² OH", and alcohols and phenols are preferable. R ² represents an optionally may hydrocarbon group having a substituent is preferably a hydrocarbon group having 1 to 30 carbon atoms which may have a substituent. The hydrocarbon group may be linear, branched, or have a ring structure. Further, the hydrocarbon group may contain an unsaturated bond. In addition, having a substituent means that it may have one or more arbitrary substituents, for example, having one or more of the following bonds, groups, atoms and the like. It means that it may be. Ester bond, amide bond, ether bond, sulfide bond, disulfide bond, urethane bond, nitro group, cyano group, ketone group, formyl group, acetal group, thioacetal group, sulfonyl group, halogen atom, silicon atom, phosphorus atom, etc. Can be mentioned.
Further, the hydroxy compound includes a hydroxycarboxylic acid having a carboxy group in the same molecule, a polycyclic hydroxy compound, a heterocyclic hydroxy compound composed of two or more kinds of elements, a hydroxy compound having a plurality of hydroxy groups, and the like. Can be used.

The hydrocarbon groups represented by R ^2, from the viewpoint of the availability reactivity and hydroxy compounds, preferably from 1 to 30, more preferably 2 to 20, with 6 to 20 It is more preferable to have. The hydrocarbon has, for example, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, and a substituent. Examples thereof include an aryl group which may be present.

As the hydroxy compound, phenols are preferable because carboxylic acid esters derived from phenols, which have been difficult to synthesize in the past, can be easily synthesized under mild conditions. Specifically, phenol and 4-methoxyphenol are particularly preferable, and since there are few steric hindrances, the carboxylic acid ester can be selectively obtained even under relatively mild conditions. Examples of other phenols include 4-phenylphenol and 1-naphthol.

According to the conventional method, when a carboxylic acid ester is produced using phenols as a hydroxy compound, ketones and the like are produced as side reactions such as Fries rearrangement and Friedel-Crafts reaction, and the carboxylic acid is produced. The yield of acid ester may decrease. According to the method for producing a carboxylic acid ester of the present invention, even when phenols are used as the hydroxy compound, the reaction can proceed under mild conditions and side reactions can be suppressed, and the yield of the carboxylic acid ester can be suppressed. Easy to improve.

As the hydroxy compound, a commercially available compound can be used, or a compound produced by a known method or the like can also be used. In addition, one type of hydroxy compound may be used alone, or two or more types may be used in combination.

〔catalyst〕
The catalyst used in the method for producing a carboxylic acid ester of the present invention contains the compound (A) from the viewpoint of efficiently synthesizing the carboxylic acid ester. Preferably, the catalyst contains compound (A) as a main component, but may contain other substances as long as the effects of the present invention are not significantly impaired.
<Compound (A)>
The compound (A) is a salt composed of an anion portion and a cation portion, the anion portion is an anion derived from a strong acid having a sulfonyl group or a sulfinyl group, and the strong acid has at least one fluorine atom. , The cation portion is at least one selected from iron ion, zinc ion, lanthanoid (for example, lanthanum, cerium, neodymium, thulium, ytterbium, etc.) ion, and ytterbium ion.
The strong acid used in the present invention means an acid having an acid dissociation constant (pKa) of 0 or less in water at 25 ° C. Further, the strong acid of the present invention has at least one fluorine atom and has a sulfonyl group or a sulfinyl group from the viewpoint that a carboxylic acid ester can be efficiently synthesized.
The strong acid of the present invention has at least one fluorine atom, but from the viewpoint of reactivity and availability, it preferably has 1 to 20 fluorine atoms, and more preferably 3 to 9 fluorine atoms. It is preferable to have 3 to 7 fluorines, more preferably.
In addition, the strong acid of the present invention has at least one selected from the group consisting of a sulfonyl group and a sulfinyl group. Examples of such a strong acid include a sulfo group, an acid containing a sulfonyl group other than the sulfo group, a sulfino group, and an acid containing a sulfinyl group other than the sulfino group.
Specific examples of the strong acid of the present invention include an acid containing a perfluoroalkyl sulfonic acid and a perfluoroalkyl sulfonyl group (excluding perfluoroalkyl sulfonic acid), and an acid containing a perfluoroalkyl sulfinic acid and a perfluoroalkyl sulfinyl group (excluding perfluoroalkyl sulfonic acid). Perfluoroalkylsulfinic acid) is preferred. More preferably, it is perfluoroalkyl sulfonic acid and perfluoroalkyl sulfinic acid, and most preferably it is perfluoroalkyl sulfonic acid.
The cation portion of compound (A) is at least one selected from iron ion, zinc ion, lanthanoid (for example, lanthanum, cerium, neodymium, thulium, etc.) ion, and yttrium ion. From the viewpoint of efficiently synthesizing the carboxylic acid ester, the cation portion is preferably at least one selected from iron ion, zinc ion, and lanthanoid ion, and more preferably iron ion, zinc ion, and lanthanide ion. And at least one selected from cerium ions.
The compound (A) is a perfluoroalkyl sulfonate or a perfluoroalkyl sulfinate of one or more metals selected from iron, zinc, lanthanum and cerium from the viewpoint of efficiently synthesizing a carboxylic acid ester. It is preferable to have. Since the solubility of the catalyst changes depending on the anion portion of the compound (A) constituting the catalyst, the catalyst can be used as a homogeneous catalyst or a heterogeneous catalyst. The catalyst may be either hydrate or anhydrous, and is not particularly limited.

Further, from the viewpoint of catalyst recovery and reuse, the catalyst is preferably a heterogeneous catalyst, and more preferably immobilized on a solid. Here, "immobilized" means that the catalyst is bonded to the solid to be in an insoluble / immobilized state, and the catalyst is attached to the solid. It also includes "supporting" the state.

The solid is not particularly limited as long as it is insoluble in water, an organic solvent, or the like and has a functional group capable of chemically bonding to the surface of the solid. More specifically, the solid can include porous particles, organic polymers, inorganic polymers, metal oxides and the like, and specifically, for example, activated carbon, polystyrene, polyethylene, silica gel, and alumina. And so on.

The immobilized compound is not particularly limited as long as the catalyst is bonded to the surface of the solid directly or via a spacer group.
The method of immobilization is not particularly limited, and examples thereof include a method of immobilizing the catalyst and the solid in a bonding mode such as a covalent bond, an ionic bond, and a coordination bond.

The amount of the catalyst immobilized on the solid is not particularly limited as long as the carboxylic acid ester can be efficiently obtained, but is preferably 0.01 to 50 mmol per 1 g of the solid. The yield of the carboxylic acid ester can be increased by setting the amount of the catalyst immobilized on the solid to the above lower limit or more with respect to 1 g of the solid. The amount of the catalyst immobilized on the solid is set to be equal to or less than the above upper limit value with respect to 1 g of the solid because it is unlikely that the effect will be dramatically improved even if the upper limit value is exceeded.
In the method for producing a carboxylic acid ester of the present invention, the carboxylic acid and the hydroxy compound are reacted in the presence of the above-mentioned catalyst. Here, "in the presence of a catalyst" means that the catalyst is present at at least a part of the reaction process, and does not have to be always present at all stages of the reaction process. Therefore, in the method for producing a carboxylic acid ester of the present invention, if the catalyst is added into the reaction system, the requirement of "in the presence of the catalyst" is satisfied. For example, even if some change occurs in the catalyst during the reaction process after the catalyst is added into the reaction system, the requirement of "in the presence of the catalyst" is satisfied.

The amount of the compound (A) used in the method for producing a carboxylic acid ester of the present invention is preferably 0.01 to 1000 mol, more preferably 0.1 to 500 mol, per 100 mol of the hydroxy compound used. The yield of the carboxylic acid ester can be increased by setting the amount of the compound (A) to be at least the above lower limit value per 100 mol of the amount of the hydroxy compound used. Further, by setting the amount of the compound (A) to be less than or equal to the above upper limit value per 100 mol of the amount of the hydroxy compound used, the load on the post-treatment step after the reaction can be reduced and the economic efficiency can be improved. Can be done. Further, even if it exceeds 1000 mol, it is unlikely that the effect will be dramatically improved. When two or more kinds of the compound (A) are used, the total amount used may be within the above range.
As the compound (A), it is preferable to use a perfluoroalkyl sulfonate or a perfluoroalkyl sulfinate. Hereinafter, the perfluoroalkyl sulfonate and the perfluoroalkyl sulfinate will be described.

(Perfluoroalkyl sulfonate)
As the cation part constituting the perfluoroalkyl sulfonate, iron ion, zinc ion, lanthanoid (for example, lanthanum, cerium, neodymium, thulium, etc.) can be used because the yield of carboxylic acid ester can be further increased. Ions and yttrium ions are used. Preferred are iron ion, zinc ion, lanthanum ion, and cerium ion.

The perfluoroalkyl sulfonate anion (anion derived from perfluoroalkyl sulfonic acid) constituting the perfluoroalkyl sulfonate is contained in the perfluoroalkyl sulfonate because the yield of the carboxylic acid ester can be further increased. It is preferable that one or more are contained. From the viewpoint of reactivity and availability of the perfluoroalkyl sulfonate, the perfluoroalkyl group constituting the perfluoroalkyl sulfonate is preferably 1 to 10 carbon atoms, preferably 1 to 7 carbon atoms. More preferably, it is more preferably 1 to 4.

More specifically, examples of the perfluoroalkyl group in the perfluoroalkyl sulfonate anion include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group and the like. Among these, a trifluoromethyl group is preferable from the viewpoint of reactivity and availability of perfluoroalkyl sulfonate.

As the perfluoroalkyl sulfonate, a commercially available one can be used, or one produced by a known method or the like can also be used. These may be used alone or in combination of two or more.

(Perfluoroalkylsulfinate)
As the cation part constituting the perfluoroalkylsulfinate, iron ion, zinc ion, lanthanoid (for example, lanthanum, cerium, neodymium, thulium, ytterbium, etc.) can be obtained from the viewpoint that the yield of carboxylic acid ester can be further increased. ) Ion and yttrium ion are used. It is preferably iron ion, zinc ion, lanthanum ion, and cerium ion, and more preferably zinc ion.

The perfluoroalkylsulfinate anion (anion derived from perfluoroalkylsulfinic acid) constituting the perfluoroalkylsulfinate is contained in the perfluoroalkylsulfinate because the yield of the carboxylic acid ester can be further increased. It is preferable that one or more of them are contained in. From the viewpoint of reactivity and availability of perfluoroalkylsulfinate, the perfluoroalkyl groups constituting the perfluoroalkylsulfinate preferably have 1 to 10 carbon atoms, preferably 1 to 7 carbon atoms. More preferably, it is more preferably 1 to 4.

More specifically, examples of the perfluoroalkyl group in the perfluoroalkyl sulfinate anion include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group and the like. Among these, a trifluoromethyl group is preferable from the viewpoint of reactivity and availability of perfluoroalkylsulfinate.

As the perfluoroalkylsulfinate, a commercially available product can be used, or a product produced by a known method or the like can also be used. These may be used alone or in combination of two or more.

[Reaction conditions]
The reaction conditions in the method for producing a carboxylic acid ester of the present invention are not particularly limited, and the reaction conditions can be appropriately changed during the reaction process.
The form of the reaction vessel used for the reaction is not particularly limited.

The reaction temperature is not particularly limited, but is preferably 80 to 220 ° C, more preferably 100 to 200 ° C, and even more preferably 120 to 180 ° C. By setting the reaction temperature to the above lower limit value or more, the reaction can proceed efficiently. Further, by setting the reaction temperature to the above upper limit value or less, the amount of by-products and the coloring of the reaction solution can be suppressed.

The reaction time is not particularly limited, but is preferably, for example, 1 to 72 hours, more preferably 3 to 48 hours, and even more preferably 5 to 24 hours. By setting the reaction time to the above lower limit value or more, the reaction can be sufficiently proceeded. Further, the reason why the reaction time is set to the above upper limit value or less is that it is unlikely that the effect will be dramatically improved even if it exceeds 72 hours.
The reaction atmosphere and reaction pressure are also not particularly limited.

The carboxylic acid ester of the present invention may be produced using a solvent or without a solvent (without using a solvent). If the reaction solution has a high viscosity, a solvent can be used if necessary. The type of solvent is not particularly limited, but for example, an organic compound having 1 to 25 carbon atoms can be used, and an organic compound having 1 to 25 carbon atoms can be appropriately selected depending on the reaction conditions. Examples of the organic compound having 1 to 25 carbon atoms include ethers such as dibutyl ether, hydrocarbons such as toluene and xylene, and halogenated hydrocarbons such as chlorobenzene. As the solvent, one kind may be used alone, or two or more kinds of mixed solvents may be used. The amount of the solvent used is also not particularly limited and can be appropriately selected.

The method for introducing the raw materials (carboxylic acid and hydroxy compound), catalyst, solvent, etc. used in the reaction into the reaction vessel is not particularly limited, but all the raw materials may be introduced at once, and some or all of them may be introduced at once. Raw materials and the like may be introduced in stages, and some or all of the raw materials and the like may be continuously introduced. Further, an introduction method combining these methods may be used.

[Carboxylate ester]
The product obtained by the method for producing a carboxylic acid ester of the present invention is a carboxylic acid ester which can be expressed as ^{"R 1} COOR ^2". Here, R ¹ and R ² are as described in the column for explaining the carboxylic acid and the column for explaining the hydroxy compound, respectively.

When the carboxylic acid used in the method for producing a carboxylic acid ester of the present invention is (meth) acrylic acid, a (meth) acrylic acid ester is produced. Since (meth) acrylic acid and (meth) acrylic acid ester are compounds that are easily polymerized, a polymerization inhibitor may be added in advance in order to prevent polymerization. The timing of adding the polymerization inhibitor is not particularly limited, but it is preferable to add the polymerization inhibitor at the start of the reaction from the viewpoint of ease of operation.

The type of the polymerization inhibitor used is not particularly limited, and for example, a known polymerization inhibitor such as 2,2,6,6-tetramethylpiperidin1-oxyl (free radical) can be used. These may be used alone or in combination of two or more. When a polymerization inhibitor is added, the amount of the polymerization inhibitor used is preferably 0.001 to 0.5 parts by mass with respect to 100 parts by mass of (meth) acrylic acid or (meth) acrylic acid ester, and is 0. More preferably, it is 0.01 to 0.1 parts by mass. Polymerization can be prevented by setting the amount of the polymerization inhibitor used to be equal to or greater than the above lower limit with respect to 100 parts by mass of (meth) acrylic acid or (meth) acrylic acid ester. Setting the amount of the polymerization inhibitor used to be less than or equal to the above upper limit value with respect to 100 parts by mass of (meth) acrylic acid or (meth) acrylic acid ester is considered to dramatically improve the effect even if it exceeds the upper limit value. This is because it is difficult. Further, a gas containing oxygen such as air may be blown. The amount of the gas blown can be appropriately selected according to the reaction conditions and the like.

In the method for producing a carboxylic acid ester of the present invention, the obtained carboxylic acid ester may be used as it is in the next reaction, or may be purified if necessary. The purification conditions are not particularly limited, and the purification conditions can be appropriately changed during the reaction process and at the end of the reaction. For example, after completion of the reaction, the carboxylic acid ester can be purified from the obtained reaction mixture by methods such as filtration, vacuum distillation, chromatography, and recrystallization. These purification methods can be carried out alone or in combination.
In the method for producing a carboxylic acid ester of the present invention, the storage container for the obtained carboxylic acid ester is not particularly limited, and for example, a glass container, a resin container, a metal container, or the like can be used.

The method for producing a carboxylic acid ester of the present invention is characterized in that a compound (A) composed of an anion derived from a strong acid having a specific structure and a specific metal cation is used. Compound (A) functions as a Lewis acid in the reaction system, but causes a side reaction (for example, Fries rearrangement using Lewis acid, Friedel-Crafts reaction, etc.) using the produced carboxylic acid ester as a raw material. Since it does not show strong Lewis acidity to cause it, it is presumed that side reactions can be suppressed. In the present invention, by using such a compound (A), the progress of the side reaction can be suppressed while the esterification reaction proceeds, and the carboxylic acid ester can be obtained with high selectivity.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples, and is arbitrarily modified and carried out without departing from the gist of the present invention. be able to.

In the examples, the analysis of the hydroxy compound, the carboxylic acid ester, etc. was performed by gas chromatography using tetradecane as an internal standard substance.
The conversion rate (%) of the hydroxy compound, the selectivity (%) of the carboxylic acid ester, and the yield (%) of the carboxylic acid ester were calculated from the following formulas (1) to (3), respectively.
Conversion rate of hydroxy compound (%) = {(S1-R1) / S1} × 100 (1)
Carboxylate ester selectivity (%) = {P1 / (S1-R1)} x 100 (2)
Yield of carboxylic acid ester (%) = (P1 / S1) × 100 (3)
S1: Amount of substance (mol) of the hydroxy compound used
R1: Amount of substance (mol) of the hydroxy compound remaining after the reaction
P1: Amount of substance (mol) of the produced carboxylic acid ester
(S1-R1) is the amount of substance (mol) of the hydroxy compound consumed in the reaction. The yield (%) of the carboxylic acid ester is represented by the product of the conversion rate (%) and the selectivity (%).
The amount of the catalyst added (mol%) was calculated from the following formula (4).
Amount of catalyst added (mol%) = (C1 / S1) x 100 (4)
C1: Amount of substance (mol) of catalyst used
S1: Amount of substance (mol) of the hydroxy compound used
The equipment configuration of gas chromatography is as follows.
<Gas chromatography equipment configuration>
Equipment: [Shimadzu] GC-2014
Carrier gas: Helium detector: FID
Column: [Agilent J & W] Selected according to the raw material using DB-1 or DB-5.
The acid dissociation constant (pKa) of the acid used in the examples at 25 ° C. in water was -14 for trifluoromethanesulfonic acid, -14 or less for bis (trifluoromethanesulfonyl) imide, and -0.6 for trifluoromethanesulfinic acid. Is.
In the case of bis (2,4-pentanedionato) titanium (IV) oxide, the pKa of acetylacetone is 8.9.

[Example 1]
In a test tube having a capacity of 25 mL (Φ18 × L195 mm), 0.471 g (5 mmol) of phenol, 0.088 g (0.25 mmol) of iron (II) trifluoromethanesulfonate, 0.651 g (5 mmol) of enanthic acid, and tetradecane 0. 050 g (0.25 mmol) was sequentially added to prepare a reaction solution. After closing the upper part of the test tube, the reaction solution was stirred and reacted at 120 ° C. to produce phenyl heptate. Table 1 shows the reaction results 5 hours after the start of the reaction.

[Examples 2 to 14]
Phenyl heptate was produced using the raw materials and catalysts shown in Table 1 in the same manner as in Example 1 except that the amounts and conditions used were changed to those shown in the same table. The reaction results 5 hours after the start of the reaction are shown in Table 1, respectively.

[Comparative Examples 1 to 7]
Phenyl heptate was produced using the raw materials and catalysts shown in Table 2 in the same manner as in Example 1 except that the amounts and conditions used were changed to those shown in the same table. The reaction results 5 hours after the start of the reaction are shown in Table 2, respectively. In Comparative Examples, the yield of phenyl heptate and the selectivity of phenol were lower than those of Examples 1 to 14.

[Examples 15 to 23]
Using the raw materials and catalysts shown in Table 3, a carboxylic acid ester was produced in the same manner as in Example 1 except that the amounts and conditions used were changed to those shown in the same table. Table 3 shows the reaction results 5 hours after the start of the reaction.

[Example 24]
2.353 g (25 mmol) of phenol, 0.045 g (0.12 mmol) of zinc (II) trifluoromethanesulfonate, 3.255 g (25 mmol) of heptanic acid, 0.248 g (1.25 mmol) of tetradecane in a 30 mL eggplant flask. ) And 5 mL of xylene were sequentially added to prepare a reaction solution. A Dean-Stark trap and a Dimroth condenser were attached to the upper part of the eggplant flask, and the inside of the Dean-Stark trap was filled with xylene. The reaction solution was stirred and reacted at 170 ° C. to produce phenyl heptate. Table 4 shows the reaction results 5 hours after the start of the reaction.

[Examples 25 to 35]
Using the raw materials, catalysts, and solvents shown in Table 4, a carboxylic acid ester was produced in the same manner as in Example 24 except that the amounts and conditions used were changed to those shown in the same table. The reaction results 5 hours after the start of the reaction are shown in Table 4, respectively. The solvent used to fill the Dean-Stark trap was the same as the solvent used in the reaction.
[Comparative Examples 8 and 9]
Phenyl heptate was produced using the raw materials, catalysts, and solvents shown in Table 4 in the same manner as in Example 24 except that the amounts and conditions used were changed to those shown in the same table. The reaction results 5 hours after the start of the reaction are shown in Table 4, respectively. The solvent used to fill the Dean-Stark trap was the same as the solvent used in the reaction. In the comparative example, the yield of phenyl heptate was lower than that in Examples 24 to 35.

From the above results, it was found that in Examples 1 to 14 to which the present invention was applied, the carboxylic acid ester was obtained under mild conditions. In particular, it was found that not only the conversion rate of alcohol but also the selectivity of the carboxylic acid ester was high, and the progress of the side reaction was suppressed while the esterification reaction proceeded. In Examples 15 to 23 in which the reaction temperature was higher than in Examples 1 to 14, the yield of the carboxylic acid ester was improved as compared with Examples 1 to 14. In Examples 24 to 35, in which water produced as a by-product together with the carboxylic acid ester was distilled off using a Dean Stark Trap, the yield of the carboxylic acid ester was significantly improved as compared with Examples 15 to 35.
On the other hand, Comparative Example 1 in which a titanium compound was used instead of compound (A), Comparative Example 2 in which the cation portion of compound (A) was changed to copper ion, and Comparative Example in which the cation portion of compound (A) was changed to scandium ion. 3. Comparative Example 4 in which the cation portion of compound (A) was changed to indium ion, Comparative Example 5 in which the cation portion of compound (A) was changed to tin ion, and Comparative Example in which the cation portion of compound (A) was changed to hafnium ion. 6. In all of Comparative Example 7 in which the acid was used instead of the compound (A), the esterification reaction did not proceed sufficiently.
Further, in Comparative Examples 8 and 9 in which the titanium compound was used instead of the compound (A), the esterification reaction did not proceed sufficiently even when water was distilled off using the Dean-Stark trap.

Claims (5)

Carboxylic acid and hydroxy compound,
A method for producing a carboxylic acid ester, which comprises reacting in the presence of a catalyst containing the compound (A) to obtain a carboxylic acid ester.
The compound (A) is a salt composed of an anion portion and a cation portion.
The anion portion is an anion derived from a strong acid having at least one selected from the group consisting of a sulfonyl group and a sulfinyl group, and the strong acid has at least one fluorine atom.
A method for producing a carboxylic acid ester, wherein the cation portion is at least one selected from the group consisting of iron ion, zinc ion, lanthanoid ion, and yttrium ion. The method for producing a carboxylic acid ester according to claim 1, wherein the strong acid is at least one selected from the group consisting of perfluoroalkyl sulfonic acid and perfluoroalkyl sulfinic acid. The method for producing a carboxylic acid ester according to claim 1 or 2, wherein the carboxylic acid is (meth) acrylic acid. The method for producing a carboxylic acid ester according to any one of claims 1 to 3, wherein the hydroxy compound is at least one selected from alcohol. The method for producing a carboxylic acid ester according to any one of claims 1 to 3, wherein the hydroxy compound is at least one selected from phenols.