JP2008238007A - Catalyst for synthesizing ester and manufacturing method of ester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for synthesizing an ester compound with high efficiency by transesterification reaction and to provide a catalyst used for the method. <P>SOLUTION: The method for synthesizing the ester compound is characterized by using the catalyst for synthesizing an ester containing a compound (A) represented by general formula (1) or an organic phosphine compound represented by general formula PR<SB>3</SB>(R; an alkyl group, an alkenyl group or an alkynyl group) and a compound (B) represented by general formula (2) to synthesize a target ester compound by transesterification reaction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ester synthesis catalyst and an ester production method.

  Ester compounds exist widely as natural products, and are widely used in various materials, food and cosmetic additives, and the like. A transesterification reaction is known as a method for synthesizing such an ester compound. The transesterification reaction is a method of synthesizing a new ester compound from a raw material ester compound by utilizing recombination of alcohol.

  The transesterification reaction is used not only in a laboratory but also at an industrial level as one of ester synthesis methods. Its versatility is not limited to the synthesis of simple ester compounds, but is diverse, such as the construction of macrolactone skeletons often found in natural products, ring-opening polymerization of lactones, and optical resolution of racemic compounds. Therefore, the transesterification reaction is one of highly practical reactions in organic synthesis. And in order to raise the yield of transesterification, the development of the catalyst for transesterification is advanced.

  Non-Patent Documents 1 to 5 describe enzymes, titanium (IV) alkoxides, alkyl tins, samarium iodides, and N-heterocyclic carbenes as catalysts for transesterification reactions. Non-Patent Document 6 describes that the fluoroalkyl tin catalyst exhibits high activity.

Furthermore, Non-Patent Document 7 describes lanthanum (III) triisopropoxide ([La (Oi-Pr) ₃ ]) as a catalyst for transesterification. Non-Patent Document 8 describes lanthanum (III) tris-trifluoromethylsulfonium salt ([La (OTf) ₃ ]) as a catalyst for transesterification. Patent Document 1 describes a method for producing a bis (3-hydroxypropyl) terephthalate monomer by a transesterification reaction using lanthanum trisacetylacetonate as a catalyst.

Enzyme Microb. Technol. 1993, 15, 367. Tetrahedron Lett. 1998, 39, 4223. J. Org. Chem. 1991, 56, 5307. J. Org. Chem. 1996, 61, 3088. J. Org. Chem. 2003, 68, 2812. Adv. Synth. Catal. 2002, 344, 84. Chem. Lett. 1995, 246. J. Am. Chem. Soc. 2003, 125, 1559. Japanese translation of PCT publication No. 2002-506843

  An object of the present invention is to provide a method for synthesizing a target ester compound by transesterification with high efficiency and a catalyst that can be used in the method.

The ester synthesis catalyst of the present invention comprises (A) a compound represented by the following general formula (1) or an organic phosphine compound represented by the general formula PR ₃ (R: an alkyl group, an alkenyl group or an alkynyl group); B) A compound represented by the following general formula (2):

（式中、上記Ｒ^１及びＲ^２は、それぞれ独立して一価の炭化水素基である。上記Ｒ^１及びＲ^２は、互いに結合して環を形成してもよい。上記Ｒ^３は、水素原子又は上記Ｒ^１と互いに結合して環を形成している一価の炭化水素基である。上記Ｒ^４は、水素原子又は上記Ｒ^２と互いに結合して環を形成している一価の炭化水素基である。）

（式中、上記Ｒ^５〜Ｒ^１０は、それぞれ独立して水素原子、電子求引性基、又はその他の置換基である。但し、上記Ｒ^５〜Ｒ^１０の少なくとも１つは電子求引性基である。また、上記電子求引性基が、ハロゲン原子及びハロゲン原子を少なくとも１個含有する一価の炭化水素基以外の電子求引性基の場合、該電子求引性基の数は０〜３である。）

(Wherein, the R ¹ and R ² are each independently a monovalent hydrocarbon group. The above R ¹ and R ^2, are bonded may form a ring. R ³ above each other, A monovalent hydrocarbon group which is bonded to each other with a hydrogen atom or R ¹ to form a ring, and R ⁴ is a monovalent hydrocarbon which is bonded to a hydrogen atom or R ² with each other to form a ring. Hydrocarbon group.)

(In the formula, R ^{5 to} R ¹⁰ are each independently a hydrogen atom, an electron withdrawing group, or other substituents, provided that at least one of R ^{5 to} R ¹⁰ is an electron withdrawing property. When the electron withdrawing group is an electron withdrawing group other than a halogen atom and a monovalent hydrocarbon group containing at least one halogen atom, the number of the electron withdrawing groups is 0-3.)

  The method for producing an ester compound of the present invention is characterized by carrying out a transesterification reaction using the ester synthesis catalyst of the present invention.

  According to the present invention, a target ester can be synthesized by transesterification with high efficiency. In particular, according to the present invention, a target ester can be synthesized by a transesterification reaction with high efficiency without excessive use of an ester or alcohol as a substrate. In addition, the catalyst of the present invention is easy to obtain and handle compared to conventional catalysts using metal or carbene.

(I) Ester Synthesis Catalyst The ester synthesis catalyst of the present invention (hereinafter simply referred to as “the catalyst of the present invention”) is represented by (A) the compound represented by the above general formula (1) or PR _3. Containing an organic phosphine compound (hereinafter referred to as “component (A)”) and (B) a compound represented by the general formula (2) (hereinafter referred to as “component (B)”). Features. The component (A) functions as a base, and the component (B) functions as an acid. The catalyst of the present invention exhibits high catalytic activity by using this acid and base in combination.

(1) Component (A) In the general formula (1), R ¹ and R ² are each independently a monovalent hydrocarbon group. Examples of the monovalent hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an arylalkyl group, and an arylalkenyl group.

  The number of carbon atoms of the alkyl group, alkenyl group, and alkynyl group (hereinafter collectively referred to as “alkyl group and the like”) is not particularly limited. Carbon number of the said alkyl group is 1-10 normally, Preferably it is 1-8, More preferably, it is 1-6, More preferably, it is 1-4, Most preferably, it is 1-3. Moreover, carbon number of the said alkenyl group and alkynyl group is 2-10 normally, Preferably it is 2-8, More preferably, it is 2-6, More preferably, it is 2-4. When the said alkyl group etc. are cyclic structures, carbon number, such as the said alkyl group, is 4-12 normally, Preferably it is 4-10, More preferably, it is 5-8, More preferably, it is 6-8.

  There is no particular limitation on the structure of the alkyl group or the like. The alkyl group or the like may be linear or have a side chain. The alkyl group or the like may have a chain structure or a cyclic structure (a cycloalkyl group, a cycloalkenyl group, and a cycloalkynyl group). Moreover, the said alkyl group etc. may have 1 type, or 2 or more types of other substituents. Furthermore, the said alkyl group etc. may contain 1 or 2 or more atoms other than a carbon atom and a hydrogen atom. For example, the alkyl group or the like may have a substituent containing an atom other than a carbon atom and a hydrogen atom as a substituent. Moreover, the said alkyl group etc. may contain 1 or 2 or more atoms other than a carbon atom and a hydrogen atom in a chain structure or a cyclic structure. Examples of the atoms other than the carbon atom and hydrogen atom include one or more of an oxygen atom, a nitrogen atom, and a sulfur atom.

  Specific examples of the alkyl group include, for example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, pentyl group, Examples include isopentyl group, neopentyl group, hexyl group, heptyl group, octyl group, and 2-ethylhexyl group. Specific examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a 2-methylcyclohexyl group. Examples of the alkenyl group include a vinyl group, an allyl group, and an isopropenyl group. Specific examples of the cycloalkenyl group include a cyclohexenyl group.

  The number of carbon atoms of the aryl group, arylalkyl group, and arylalkenyl group (hereinafter collectively referred to as “aryl group etc.”) is not particularly limited. Carbon number, such as said aryl group, is 6-15 normally, Preferably it is 6-12, More preferably, it is 6-10.

  The structure of the aryl group or the like is not particularly limited. The aryl group or the like may have one or more other substituents. For example, the aromatic ring contained in the aryl group or the like may have one or more other substituents. The position of this substituent may be any of o-, m-, and p-. Specific examples of the substituent include one or more of a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), alkyl group, alkenyl group, nitro group, amino group, hydroxyl group, and alkoxy group. Is mentioned. When these substituents are located on the aromatic ring, the position of the substituent may be any of o-, m-, and p-.

  Specific examples of the aryl group include a phenyl group, a tolyl group, an ethylphenyl group, a xylyl group, a cumenyl group, a mesityl group, a methoxyphenyl group (o-, m-, and p-), and an ethoxyphenyl group (o -, M-, and p-), 1-naphthyl group, 2-naphthyl group, and biphenylyl group. Specific examples of the arylalkyl group include a benzyl group, a methoxybenzyl group (o-, m-, and p-), an ethoxybenzyl group (o-, m-, and p-), and a phenethyl group. Specific examples of the arylalkenyl group include a styryl group and a cinnamyl group.

R ¹ and R ² may be bonded to each other to form a ring. There is no particular limitation on the structure of the ring. For example, the number of ring members can usually be a 4- to 10-membered ring, preferably a 5- to 8-membered ring including a nitrogen atom. The number of ring members is usually a 5-membered ring or a 6-membered ring. The ring may contain a hetero atom (oxygen atom, nitrogen atom, sulfur atom, etc.) in the structure. Furthermore, the ring may have other substituents. Moreover, the said ring may have an unsaturated bond in the structure.

R ³ is a hydrogen atom or a monovalent hydrocarbon group that is bonded to R ¹ to form a ring. R ⁴ is a hydrogen atom or a monovalent hydrocarbon group that is bonded to R ² to form a ring. For example, each of R ³ and R ⁴ can be a hydrogen atom. In the general formula (1), only ^one of R ¹ and R ³ and R ² and R ⁴ may be bonded to each other to form a ring. Furthermore, in the general formula (1), both R ¹ and R ³ and R ² and R ⁴ may be bonded to each other to form a ring. The ring structure is not particularly limited. For example, the number of ring members can usually be a 4- to 10-membered ring, preferably a 5- to 8-membered ring including a nitrogen atom. The number of ring members is usually a 5-membered ring or a 6-membered ring. The ring may contain a hetero atom (oxygen atom, nitrogen atom, sulfur atom, etc.) in the structure. Furthermore, the ring may have other substituents. The ring may have an unsaturated bond in the structure.

The PR ₃ is one type of organic phosphine compound. R is an alkyl group, an alkenyl group, or an alkynyl group. The description of R ¹ and R ² is appropriate for the types and structures of the alkyl group, alkenyl group, and alkynyl group. Specific examples of R include, for example, an alkyl group having 1 to 5 carbon atoms (methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, and t-butyl group). Etc.). The _three Rs included in the PR ₃ may have the same structure or different structures.

(2) Component (B) In the compound represented by the general formula (2), R ^{5 to} R ¹⁰ are each independently a hydrogen atom, an electron withdrawing group, or other substituent. However, at least one of the R ^{5 to} R ¹⁰ is an electron withdrawing group. In the formula, the number of electron withdrawing groups other than a halogen atom and a monovalent hydrocarbon group containing at least one halogen atom is 0 to 3.

  There is no limitation in particular in the kind and structure of the said electron withdrawing group. Examples of the electron withdrawing group include a monovalent hydrocarbon group containing at least one halogen atom (one kind or two or more kinds such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom) and a halogen atom. (Hereinafter referred to as “halogenated hydrocarbon group”), alkoxycarbonyl group (such as methoxycarbonyl group and ethoxycarbonyl group), alkylcarbonyl group (such as methylcarbonyl group and ethylcarbonyl group), amide group, carboxyl group, nitro group , A cyano group, a formyl group, a sulfonic acid group, and a sulfonyl group. The electron withdrawing group is preferably a halogen atom or a halogenated hydrocarbon group.

  The type and structure of the halogenated hydrocarbon group are not particularly limited as long as at least one hydrogen atom in the monovalent hydrocarbon group is substituted with a halogen atom. As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned, for example. Further, the number of the halogen atoms contained in the halogenated hydrocarbon group is not particularly limited. The number of halogen atoms can be 1 or more, preferably 2 or more, more preferably 3 or more. Further, when two or more halogen atoms are contained, each halogen atom may be the same atom or different atoms.

There is no particular limitation on the type and structure of the monovalent hydrocarbon group. Examples of the monovalent hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an arylalkyl group, and an arylalkenyl group. The description of R ¹ and R ² is appropriate for the type and structure of the monovalent hydrocarbon group. Specific examples of the monovalent hydrocarbon group include an alkyl group having 1 to 3 carbon atoms (methyl group, ethyl group, n-propyl group, i-propyl group).

  Examples of the halogenated hydrocarbon group include 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and more preferably one or more hydrogen atoms of an alkyl group having 1 to 3 carbon atoms. A group in which 2 or more, more preferably 3 or more hydrogen atoms are substituted with halogen atoms is preferable. Examples of the halogenated hydrocarbon group include one or more hydrogen atoms of an alkenyl group having 2 to 10 carbon atoms, preferably 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, and more preferably 2 or 3 carbon atoms. A group in which 2 or more, more preferably 3 or more hydrogen atoms are substituted with halogen atoms is preferable.

Examples of the halogenated hydrocarbon group include the following groups. In the following formula, X is a halogen atom. In the following formulae, R ^a is a hydrogen atom or a monovalent hydrocarbon group. Examples of the monovalent hydrocarbon group include an alkyl group and an alkenyl group. The description of R ¹ and R ² is appropriate for the type and structure of the monovalent hydrocarbon group. Further, R ^a may be a halogenated alkyl group or a halogenated alkenyl group. R ^a is preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms (preferably 1 to 4, more preferably 1 to 3, more preferably 1 or 2), and an alkyl group having 2 to 2 carbon atoms. 6 (preferably 2 to 4, more preferably 2 or 3) alkenyl groups and halogenated alkenyl groups. In the following formula, when two R ^a are present, each R ^a may be the same group or a different group.

  Specific examples of the halogenated hydrocarbon group include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a chloromethyl group, a dichloromethyl group, a trichloromethyl group, a 1,1-difluoroethyl group, and 1, A 1-dichloromethyl group is mentioned.

  In the compound represented by the general formula (2), the type and structure of the other substituents are not particularly limited.

In the compound represented by the general formula (2), the type and structure of R ^{5 to} R ¹⁰ are not particularly limited as long as at least one of the R ^{5 to} R ¹⁰ is the electron withdrawing group. For example, in the compound represented by the general formula (2), the number of the electron withdrawing groups can be 1 or more, preferably 2 or more, more preferably 3 or more, more preferably 4 or more. Of course, all of R ^{5 to} R ¹⁰ may be the electron withdrawing property. For example, when the electron withdrawing group is the halogen atom or the halogenated hydrocarbon group, the number of the halogen atom or the halogenated hydrocarbon group is 1 or more, preferably 2 or more, more preferably 3 or more, more Preferably it can be 4 or more. In this case, the compound represented by the general formula (2) may contain only one of the halogen atom and the halogenated hydrocarbon group, or may contain both. When the electron withdrawing group is a halogen atom, all of R ^{5 to} R ¹⁰ can be the halogen atom.

  However, in the compound represented by the general formula (2), the electron withdrawing group is an electron withdrawing group other than “a halogen atom and a monovalent hydrocarbon group containing at least one halogen atom”. In this case, the number of electron withdrawing groups is 0-3. When the number of the electron withdrawing groups is 4 or more, the acidity of the compound represented by the general formula (2) becomes too high and the stability is lowered. As a result, the catalytic activity is lowered, which is not preferable. .

Moreover, the number of the electron withdrawing groups contained in each aromatic ring of the compound represented by the general formula (2) may be the same or different. For example, in the general formula (2), at least one of the R ^{5 to} R ⁷ is the electron withdrawing group, and at least one of the R ^{8 to} R ¹⁰ is the electron withdrawing group. Can do.

Further, the position of the electron withdrawing group is not particularly limited. The position of the electron withdrawing group is usually the m-position (R ⁵ , R ⁷ , R ⁸ , and R ¹⁰ ). For example, in the compound represented by the general formula (2), at least two, preferably at least three of R ⁵ , R ⁷ , R ⁸ , and R ¹⁰ can be used as the electron withdrawing group. . For example, at least 2, preferably 3, and more preferably all of R ⁵ , R ⁷ , R ⁸ and R ¹⁰ can be the halogen atom or the halogenated hydrocarbon group. In addition, the position of the electron withdrawing group contained in each aromatic ring of the compound represented by the general formula (2) may be the same or different.

Examples of the compound represented by the general formula (2) include compounds represented by the following general formula. In the following formulae, R ^{5 ′ to} R ^{10 ′} are the electron withdrawing group, preferably the halogen atom or the halogenated hydrocarbon group.

(3) Others In the catalyst of the present invention, the ratio of the component (A) to the component (B) is not particularly limited. The proportion of the component (B) is 0.5 to 1.5 mol%, preferably 0.5 to 1.3 mol%, more preferably 0.7 to 1.3 mol%, relative to 1 mol% of the component (A). It is. It is preferable for the ratio of the component (B) to be within the above range since the desired ester compound can be obtained in a high yield.

  The method for obtaining the catalyst of the present invention is not particularly limited. For example, the catalyst of the present invention can be obtained by adding the component (A) and the component (B) to a solvent. The blending ratio of the component (A) and the component (B) can be within the above range. As the solvent, a low polarity or nonpolar organic solvent can be used. The solvent may be one type of solvent or a mixed solvent of two or more types. Examples of the low polarity organic solvent include dichloromethane, 1,2-dichloroethane, anisole, toluene, benzene, and chlorobenzene. The nonpolar solvent may be an aliphatic organic solvent or an aromatic organic solvent. Examples of the aliphatic organic solvent include alkanes and cycloalkanes (for example, having 4 or more carbon atoms, preferably 5 or more carbon atoms). Specific examples of the aliphatic organic solvent include pentane, hexane, cyclohexane, heptane, and octane.

  The composition of the catalyst of the present invention is not particularly limited as long as it contains the component (A) and the component (B). The catalyst of the present invention may contain components other than the component (A) and the component (B). There is no particular limitation on the form of the catalyst of the present invention. The catalyst of the present invention may be present in a solvent, or may be present as a residue by distilling off the solvent. Furthermore, the catalyst of the present invention may be used as it is. Further, the catalyst of the present invention may be formed in, for example, a reaction solvent without being isolated as a catalyst and used as it is in the reaction.

  The catalyst of the present invention can catalyze the synthesis of an ester compound, particularly a transesterification reaction in which an ester compound as a raw material is reacted with an alcohol to obtain a target ester compound. Therefore, the said catalyst can be utilized as a catalyst for transesterification.

(II) A method for producing an ester compound.
The method for producing an ester compound of the present invention (hereinafter referred to as “the production method of the present invention”) is characterized by carrying out a transesterification reaction using the catalyst of the present invention. Hereinafter, in the transesterification reaction, the ester compound and alcohol which are substrates are referred to as “substrate ester compound” and “substrate alcohol”.

  In the production method of the present invention, the type and structure of the substrate ester compound are not particularly limited. The substrate ester compound may be a monoester compound or a polyester compound such as a diester compound.

When the substrate ester compound is represented by RCOOR ′ (R: monovalent hydrocarbon group derived from carboxylic acid, R ′: monovalent hydrocarbon group derived from alcohol), the types and structures of R and R ′ include There is no particular limitation. Examples of R include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an arylalkyl group, and an arylalkenyl group. Examples of R ′ include an alkyl group, an alkenyl group, an alkynyl group, an arylalkyl group, and an arylalkenyl group. For the types and structures of the alkyl group, alkenyl group, alkynyl group, aryl group, arylalkyl group, and arylalkenyl group, the description of R ¹ and R ^{2 in} the catalyst of the present invention is appropriate. In addition, when said R and R 'have an unsaturated bond, there is no limitation in particular also in the number of this unsaturated bond.

The R of the substrate ester compound is preferably a chain alkyl group or a chain alkenyl group. R is preferably a chain alkyl group or a chain alkenyl group having 1 to 12, more preferably 1 to 10, and more preferably 2 to 9 carbon atoms. The R ′ of the substrate ester compound is preferably an alkyl group or an alkenyl group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and more preferably 1 to 3 carbon atoms. Specific examples of R in the substrate ester compound include structures of the following general formulas (I) to (III). In the following general formulas (I) to (III), R ^b is a hydrogen atom or a monovalent hydrocarbon group. The description of R ¹ and R ^{2 in} the catalyst of the present invention is appropriate for the type and structure of the monovalent hydrocarbon group. ^Rb is preferably a hydrogen atom or an alkyl group, alkenyl group, or aryl group having 1 to 8, preferably 1 to 6, and more preferably 1 to 4 carbon atoms.

  Specific examples of the substrate ester compound include carboxylic acid methyl ester, carboxylic acid ethyl ester, carboxylic acid allyl ester, and carboxylic acid vinyl ester. Specific examples of the substrate ester compound include phenylacetate ester and cinnamic acid ester (both aromatic rings may have a substituent), and chain alkyl having 5 to 12 carbon atoms. Group and an alkenyl group having 5 to 12 carbon atoms.

  In the production method of the present invention, the type and structure of the substrate alcohol are not particularly limited. The substrate alcohol may be a monohydric alcohol or a dihydric or higher polyhydric alcohol. The substrate alcohol may be any of primary alcohol, secondary alcohol, and tertiary alcohol. The substrate alcohol is preferably a primary alcohol or a secondary alcohol, and more preferably a primary alcohol.

When the substrate alcohol is represented by R—OH (R: monovalent hydrocarbon group), the type and structure of R are not particularly limited. Examples of R include an alkyl group, an alkenyl group, an alkynyl group, an arylalkyl group, and an arylalkenyl group. For the types and structures of the alkyl group, alkenyl group, alkynyl group, aryl group, arylalkyl group, and arylalkenyl group, the description of R ¹ and R ^{2 in} the catalyst of the present invention is appropriate. In addition, when said R has an unsaturated bond, there is no limitation in particular also in the number of this unsaturated bond.

  The R of the substrate alcohol is preferably an alkyl group and alkenyl group having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, a cycloalkyl group and cycloalkenyl group having 4 to 12 carbon atoms, preferably 4 to 10 carbon atoms, And an arylalkyl group. More specifically, for example, methanol, n-propanol, i-propanol, 1-butanol, 2-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, cyclohexanol, And benzyl alcohol.

  In the production method of the present invention, the type and structure of the target ester compound are not particularly limited. The target ester compound can be appropriately selected depending on the combination of the substrate ester compound and the substrate alcohol.

  In the production method of the present invention, the ratio of the substrate ester compound and the substrate alcohol is not particularly limited. In the production method of the present invention, the molar ratio of the substrate ester compound to the substrate alcohol is 1: (0.5 to 2.5), preferably 1: (0.5 to 2), more preferably 1: (0.8 to 1.8), more preferably 1: (0.8 to 1.5), and particularly preferably 1: (0.8 to 1.2). The transesterification reaction is a reversible reaction. Therefore, in the transesterification reaction, in order to bias the equilibrium toward the product side, it is usually necessary to use one of the starting ester or alcohol in a stoichiometric amount or more. However, when the raw material is used excessively, the raw material remains after the reaction, which is uneconomical and the processing of the excessive raw material becomes a problem. However, in the production method of the present invention, the target ester can be obtained by transesterification with high efficiency even when the molar ratio is within the above range. As a result, the generation of excess substrate can be suppressed, which is preferable.

  In the production method of the present invention, there are no particular limitations on the type of solvent used for the transesterification reaction. As the solvent, a low polarity or nonpolar organic solvent can be used. The solvent may be one type of solvent or a mixed solvent of two or more types. Examples of the low polar organic solvent include dichloromethane, 1,2-dichloroethane, anisole, toluene, benzene, and chlorobenzene. The nonpolar solvent may be an aliphatic organic solvent or an aromatic organic solvent. Examples of the aliphatic organic solvent include alkanes and cycloalkanes (for example, having 4 or more carbon atoms, preferably 5 or more carbon atoms). Specific examples of the aliphatic organic solvent include pentane, hexane, cyclohexane, and heptane. It is preferable to use the aliphatic organic solvent as the solvent because the target ester compound can be obtained in a high yield even when the ratio (molar ratio) of the substrate ester compound and the substrate alcohol is close to 1: 1. Further, it is preferable to use octane as the solvent because a target ester compound can be obtained in a high yield even when a bulky ester or alcohol is used as a substrate.

  In the production method of the present invention, the ester exchange reaction is carried out using the ester synthesis catalyst of the present invention. In the production method of the present invention, the specific usage of the ester synthesis catalyst of the present invention is not particularly limited as long as the component (A) and the component (B) are present in the reaction system. For example, in the production method of the present invention, by adding the ester synthesis catalyst of the present invention prepared in advance to the reaction solvent, the component (A) and the component (B) can be present in the reaction solvent. In the production method of the present invention, the component (A) and the component (B) may be present in the reaction solvent by adding the component (A) and the component (B) to the reaction solvent. . When the component (A) and the component (B) are added to the reaction solvent, the order of addition is not particularly limited. After adding either one of the component (A) and the component (B), the other may be added, or both may be added simultaneously.

  In the production method of the present invention, the amount of the component (A) and the component (B) is not particularly limited. The amount of the component (A) and the component (B) is independently 0.5 to 15 mol%, preferably 1 to 12 mol%, more preferably 2 to 10 mol%, based on the substrate ester compound. Moreover, there is no limitation in particular also in the ratio of the said (A) component and the said (B) component. The proportion of the component (B) is 0.5 to 1.5 mol%, preferably 0.5 to 1.3 mol%, more preferably 0.7 to 1.3 mol%, relative to 1 mol% of the component (A). It is. It is preferable for the ratio of the component (B) to be within the above range since the desired ester compound can be obtained in a high yield.

  In the production method of the present invention, the reaction conditions for the transesterification reaction are not particularly limited. The reaction conditions can be appropriately selected according to the types and structures of the substrate ester compound and the substrate alcohol. The reaction time can be, for example, 1 to 48 hours, preferably 1 to 24 hours. Moreover, as reaction temperature, it is 70-150 degreeC, for example, Preferably it can be set as 80-130 degreeC.

  Hereinafter, the present invention will be described specifically by way of examples. In addition, this invention is not restricted to the form shown in the Example. The embodiment of the present invention can be variously modified within the scope of the present invention depending on the purpose and application.

(1) Transesterification reaction (I)
The transesterification reaction was performed using various acidic compounds and basic compounds as catalysts, and the yield was examined.

  A Soxhlet tube and a cold finger were attached to a 10 ml eggplant flask containing a stirrer chip to prepare a reaction apparatus. The Soxhlet tube is connected to the upper part of the eggplant flask. Next, molecular sieves 4A (MS4A) (3.50 g) was placed in a Soxhlet tube. The MS4A was previously dried in a microwave oven (heated at 700 W for 1 minute and then dried three times until it was cooled to room temperature under reduced pressure). The MS4A was added to adsorb methanol produced in the transesterification reaction.

The reactor was heated and dried under reduced pressure, and then charged with nitrogen. 4-dimethylaminopyridine (DMAP) (12.2 mg, 0.1 mmol) and 1,3-bis [3,5-bis (trifluoromethyl) phenyl] thiourea (50.0 mg, in nitrogen gas) in heptane. A mixed solution (5 ml) containing 0.1 mmol) was added into the reactor. After stirring at room temperature for 1 hour, distilled anhydrous benzyl alcohol (541 mg, 5 mmol) and methyl phenylacetate (751 mg, 5 mmol) were added respectively, and the mixture was heated to reflux for 6 hours using an oil bath heated to 90 ° C. went. After returning to room temperature, the reaction solution was concentrated under reduced pressure using an evaporator, and the residue was separated and purified with a mixed solvent of hexane-ethyl acetate using silica gel column chromatography. As a result, the target benzyl ester was obtained as a colorless and transparent oily substance. When the reaction solution was analyzed by ¹ H-NMR, the yield of the objective phenylacetate benzyl acetate was 91%.

  Using each acidic compound and basic compound shown below as a catalyst, a target ester compound was synthesized by performing a transesterification reaction in the same manner as described above. The kind of catalyst used and the yield of the ester compound are shown below.

  From Table 1, as a catalyst, when only 1,3-bis [3,5-bis (trifluoromethyl) phenyl] thiourea (hereinafter simply referred to as “thiourea compound”) and only DMAP were used. None of the cases showed almost catalytic activity. On the other hand, when both were used together, the yield was 91%, and a remarkable catalytic activity was recognized. Further, when tri-n-butylphosphine was used instead of DMAP, a relatively high catalytic activity was observed although it was lower than that of DMAP.

  On the other hand, when other acidic compounds (catechol, phosphoric acid, and sulfuric acid) were used in combination with DMAP instead of the thiourea compound, the catalytic activity was extremely low. In particular, in view of the fact that the catalytic activity was extremely low even when sulfuric acid was used, it can be seen that the acidic compound is not simply high in acidity. Furthermore, when the strongly basic 1,4-diazabicyclo [2.2.2] octane was used in combination with the thiourea compound instead of the DMAP, the catalyst activity was hardly exhibited. From this result, when a strongly basic compound (1,4-diazabicyclo [2.2.2] octane, quinuclidine, etc.) is used in place of the above DMAP, it shows almost no catalytic activity or very high catalytic activity. It is considered low.

(2) Transesterification reaction (II)
As a catalyst, various above-mentioned (A) components and the said thiourea compound were used together, transesterification was performed, and the yield was investigated.

  The following compounds were used as the component (A). Moreover, the target ester compound was synthesize | combined by performing the transesterification by the method similar to said (1) except making reaction conditions into the following conditions. The kind of catalyst used and the yield of the ester compound are shown below.

From Table 2, when the aminopyridine compound was used as the component (A), the yield was higher than when the phosphine compound was used. Therefore, it can be seen that the compound represented by the general formula (1) is more preferable as the component (A). In addition, in aminopyridine-based compounds, pyrrolidinopyridine (R ¹ and R ^{2 in} the general formula (1) are bonded to each other rather than DMAP (R ¹ and R ^{2 in} the general formula (1) are methyl groups). The yield was higher.

(3) Transesterification reaction (III)
As a catalyst, various above-mentioned (B) components and 4-pyrrolidinopyridine were used in combination, and a transesterification reaction was performed to examine the yield.

  4-Pyrrolidinopyridine and the compound shown below were used as a catalyst. A target ester compound was synthesized by performing a transesterification reaction in the same manner as in the above (1) except that the reaction conditions were as follows. The kind of catalyst used and the yield of the ester compound are shown below.

  From Table 3, the thiourea compound having four trifluoromethyl groups at the m-position had the highest yield. The compound obtained by reducing one trifluoromethyl group from the thiourea compound had lower acidity and a slightly lower yield (60%) than the thiourea compound, but still had sufficient catalytic activity. On the other hand, when the trifluoromethyl group of the thiourea compound was changed to a nitro group, a considerable amount of the compound was decomposed during the heating reaction, and the catalytic activity was significantly reduced. When urea having a trifluoromethyl group was used instead of thiourea, almost no catalytic activity was observed.

(4) Transesterification reaction (IV)
The transesterification reaction was performed using various substrate ester compounds and substrate alcohols, and the yield was examined.

  The following ester compounds were used as substrate ester compounds. A target ester compound was synthesized by performing a transesterification reaction in the same manner as in the above (1) except that the reaction conditions were as follows. The yield of the ester compound is shown below.

  The target ester compound was synthesized by carrying out a transesterification reaction in the same manner as in the above (1) except that the following ester compound was used as the substrate ester compound and the reaction conditions were as follows. The yield of the ester compound is shown below.

  From Table 4, phenylacetate, cinnamate, and caprate showed high yields by heating and refluxing using heptane as a solvent. On the other hand, benzoate and cyclohexyl carboxylate in which the vicinity of the α-position is sterically crowded are decreased in reactivity (it is considered that the catalyst and alcohol are difficult to approach the substrate). However, when octane was used as the solvent and the heating temperature was increased and the heating was refluxed, a high yield was obtained.

  Further, esters other than methyl ester were also examined. As a result, from Table 5, the yield of ethyl ester was lower than that of methyl ester. On the other hand, the yield of allyl ester was slightly higher than that of methyl ester. In addition, since the vinyl alcohol to be eliminated becomes an aldehyde, the vinyl ester is considerably more reactive than other esters because the equilibrium is biased toward the product.

  Next, the generality of the substrate alcohol was examined. As a result, from Table 6, benzyl alcohol had the highest yield. Moreover, although other primary alcohol was lower than benzyl alcohol, it showed a high yield. Further, the secondary alcohol had a lower yield than the primary alcohol, but showed a relatively high catalytic activity.

(5) Transesterification reaction (V)
As the catalyst, the above thiourea compound and 4-pyrrolidinopyridine were used. The ester compound shown below was synthesized by performing a transesterification reaction in the same manner as in the above (1) except that the reaction conditions were as follows. The yield of the ester compound is shown below.

Claims (10)

(A) a compound represented by the following general formula (1) or an organic phosphine compound represented by the general formula PR ₃ (R: alkyl group, alkenyl group or alkynyl group), and (B) the following general formula (2) And a compound for ester synthesis characterized by comprising:

(Wherein, the R ¹ and R ² are each independently a monovalent hydrocarbon group. The above R ¹ and R ^2, are bonded may form a ring. R ³ above each other, A monovalent hydrocarbon group which is bonded to each other with a hydrogen atom or R ¹ to form a ring, and R ⁴ is a monovalent hydrocarbon which is bonded to a hydrogen atom or R ² with each other to form a ring. Hydrocarbon group.)

(In the formula, R ^{5 to} R ¹⁰ are each independently a hydrogen atom, an electron withdrawing group, or other substituents, provided that at least one of R ^{5 to} R ¹⁰ is an electron withdrawing property. In the formula, the number of electron-attracting groups other than a halogen atom and a monovalent hydrocarbon group containing at least one halogen atom is 0 to 3.) The catalyst for ester synthesis according to claim ^1, wherein R ¹ and R ² are monovalent hydrocarbon groups and are bonded to each other to form a ring. At least one of the R ⁵ to R ⁷ are the electron-withdrawing group, at least one catalyst for ester synthesis according to claim 1 or 2 wherein the said electron-withdrawing group of the R ⁸ to R ¹⁰ . 4. The ester synthesis catalyst according to claim 1, wherein at least two of R ⁵ , R ⁷ , R ⁸ , and R ¹⁰ are the electron withdrawing group.   The catalyst for ester synthesis according to any one of claims 1 to 4, wherein the electron withdrawing group is a halogen atom or a monovalent hydrocarbon group containing at least one halogen atom. 6. The ester synthesis catalyst according to claim 5, wherein the monovalent hydrocarbon group containing at least one halogen atom is any of the following groups.

(Wherein, R ^a is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms. X is a halogen atom.)   A method for producing an ester compound, comprising performing a transesterification reaction using the ester synthesis catalyst according to any one of claims 1 to 6.   The method for producing an ester compound according to claim 7, wherein the ester compound as a substrate is carboxylic acid methyl ester, carboxylic acid ethyl ester, carboxylic acid allyl ester, or carboxylic acid vinyl ester.   The method for producing an ester compound according to claim 7 or 8, wherein the alcohol as a substrate is a primary alcohol.   The method for producing an ester compound according to any one of claims 7 to 9, wherein the molar ratio of the ester compound as a substrate to the alcohol is 1: (0.5 to 2.5).