Method for producing carbamic acid ester

Abstract

To provide a method for producing a carbamic acid ester from a carbamate as the raw material, without using a sacrificial reagent or an alkyl halide.SOLUTION: Provided is a method for producing a carbamic acid ester including a reaction step of generating a carbamic acid ester represented by formula (A-1) or (A-2) from a carbamate represented by formula (B-1) or (B-2) and an alkoxysilane (R11 represents a hydrogen atom or a hydrocarbon group; R21 and R31 each represent a hydrocarbon group; R12 represents a hydrogen atom or a hydrocarbon group; R22 represents a hydrocarbon group; R32 represents a hydrocarbon group; Q represents a q-valent countercation; q is 1 or 2; Q' represents a (2 / q')-valent countercation; and q' is 1 or 2).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing carbamic acid esters.

Background Art

[0002] Carbamic acid esters are useful compounds having a wide range of uses as pharmaceuticals, agricultural chemicals, various fine chemicals, and synthetic raw materials thereof.

[0003] Heretofore, methods for producing carbamic acid esters using carbon dioxide at normal pressure have been proposed. For example, Non-Patent Document 1 describes, as a method for synthesizing a carbamate derivative, ammonium carbamate in situ synthesized from the reaction of an amine as a carbonyl source and CO2, an equivalent amount of multicomponent synthesis using triphenylphosphine and an equivalent amount of trichloroisocyanuric acid (TCCA) has been studied. In Non-Patent Document 1, CO2 gas at 1 atm is used, and a non-renewable sacrificial reagent is used. Non-Patent Document 2 reports a method for synthesizing a carbamic acid ester via carbamic acid using 1 atm of CO2 gas and 1,8-diazabicyclo[5.4.0]undec-7-ene as a catalyst. In Non-Patent Document 2, PBu3 and DBAD (di-tert-butyl azodicarboxylate), which are non-renewable sacrificial reagents, are used. Non-Patent Document 3 reports the synthesis of a carbamic acid ester using KO2 / Et4NBr or the like, which is a non-renewable sacrificial reagent, from an amine and CO2 gas. Non-Patent Document 4 reports the synthesis of a carbamic acid ester by Mitsunobu reaction using 1 atm of CO2 gas, via carbamic acid, using Ph3P and DEAD (diethyl azodicarboxylate), which are sacrificial reagents.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

[0005] All of the above methods for producing carbamic acid esters require either sacrificial reagents or environmentally unfriendly alkyl halides. An object of the present invention is to provide a method for producing a carbamic acid ester using a carbamate as a raw material without using a sacrificial reagent or an alkyl halide. [Means for Solving the Problems]

[0006] (1) As a result of intensive studies to solve the above problems, the present inventors have found that a carbamic acid ester is formed from a carbamate and a metal alkoxide, and have completed the present invention. The present invention provides the following specific embodiments and the like. [1] A method for producing a carbamic acid ester, comprising producing a carbamic acid ester having a structure represented by the following formula (a-1) or (a-2) from a carbamate and a metal alkoxide. (In the formula, specific chemical structures are represented, but not shown in the translation due to lack of specific chemical structure input) [Chemical formula] (In the above formula, R 1 each independently represents a hydrogen atom or a monovalent hydrocarbon group which may be unsubstituted or substituted, R 2 , R 3 each independently represents a monovalent hydrocarbon group which may be unsubstituted or substituted, and R 20 represents a divalent hydrocarbon group which may be unsubstituted or substituted.) [2] The method for producing a carbamate according to [1], wherein the carbamate is a carbamate represented by the formula (B-1), the metal alkoxide is a metal alkoxide represented by the formula (C-1), and the carbamate having the structure represented by the formula (a-1) is a carbamate represented by the formula (A-1). [Chemical formula] (In the above formula, R 11 represents a hydrogen atom or a monovalent hydrocarbon group which may be unsubstituted or substituted; R 21 , R 31 each independently represents a monovalent hydrocarbon group which may be unsubstituted or substituted; R 41 each independently represents a hydrocarbon ligand which may be unsubstituted or substituted, an alkoxy ligand, an amide ligand, or a halide ligand different from -OR 31 ; M represents a metal atom or a metalloid atom; n represents the oxidation number of M; (n - m) is an integer of 1 to 6; m represents an integer of 0 or more and (n - 1) or less; Q represents a counter cation of q valence ; and q is 1 or 2.) [3] The method for producing a carbamate according to [2], wherein Q is a cation selected from the group consisting of an ammonium cation, an amidinium cation, a guanidinium cation, a phosphonium cation, a phosphazenium cation, a carbocation, an alkali metal cation, and an alkaline earth metal cation. [4] The carbamate is a carbamate represented by the formula (B-2), the metal alkoxide is a metal alkoxide represented by the formula (C-2), and the carbamic acid ester having the structure represented by the formula (a-2) is a carbamic acid ester represented by the formula (A-2). The method for producing a carbamic acid ester according to [1]. [Chemical formula] (In the above formula, R 12 each independently represents a hydrogen atom or a monovalent hydrocarbon group which is unsubstituted or has a substituent; R 22 represents a divalent hydrocarbon group which is unsubstituted or has a substituent; R 32 each independently represents a monovalent hydrocarbon group which is unsubstituted or has a substituent; R 42 each independently represents a hydrocarbon ligand which is unsubstituted or has a substituent, an alkoxy ligand, an amide ligand, or a halide ligand different from -OR 32 ; M'represents a metal atom or a metalloid atom, n'represents the oxidation number of M', and ( n'-m') is an integer of 1 to 6; m'represents an integer of 0 or more and (n'-1) or less; Q 'represents a (2 / q')-valent counter cation; q'is 1 or 2.) [5] The method for producing a carbamic acid ester according to [4], wherein the Q'is a cation selected from the group consisting of an ammonium cation, an amidinium cation, a guanidinium cation, a phosphonium cation, a phosphazenium cation, a carbocation, an alkali metal cation, and an alkaline earth metal cation. [6] The method for producing a carbamic acid ester according to any one of [1] to [5], wherein the metal alkoxide is at least one selected from the group consisting of a titanium compound and a silicon compound. Manufacturing method. [7] The method for producing a carbamic acid ester according to any one of [1] to [6], wherein the metal alkoxide is alkoxysilane and the reaction step is carried out in the presence of a catalyst. [8] The catalyst is at least one selected from the group consisting of organic base carboxylates, alkali metal salts, zinc compounds, titanium(IV) compounds, and zirconium(IV) compounds The method for producing a carbamate according to [7]. [9] The method for producing a carbamate according to any one of [1] to [8], wherein the reaction step is carried out in the presence of an aprotic solvent.

[10] Further comprising a carbamate production step of producing the carbamate by contacting an amino group-containing organic compound with a carbon dioxide-containing mixed gas in the presence of a base in a solvent, and the volume of carbon dioxide in the carbon dioxide-containing mixed gas is 0.01% or more. The method for producing a carbamate according to any one of [1] to [9]. [Advantages of the Invention]

[0007] According to the present invention, a method for producing a carbamate using a carbamate as a raw material without using a sacrificial reagent or an alkyl halide can be provided. [Embodiments for Carrying Out the Invention]

[0008] In explaining the details of the present invention, specific examples will be given for explanation, but it is not limited to the following content as long as it does not deviate from the gist of the present invention, and it can be appropriately changed and implemented.

[0009] <1. Method for Producing Carbamate> The method for producing a carbamate according to an embodiment of the present invention includes a reaction step (hereinafter, may be abbreviated as "reaction step") of producing a carbamate having a structure represented by the following formula (a-1) or (a-2) from a carbamate and a metal alkoxide. It is characterized by that. [Chemical formula] (In the above formula, R 1 each independently represents a hydrogen atom or a monovalent hydrocarbon group having no substituent or a substituent, R 2 , R3 each independently represents a monovalent hydrocarbon group which may be unsubstituted or have a substituent, and R 20 represents a divalent hydrocarbon group which may be unsubstituted or have a substituent.)

[0010] Examples of the reaction for producing a carbamate having a structure represented by the formula (a-1) or (a-2) from a carbamate and a metal alkoxide include, for example, the reaction of benzylammonium N-benzylcarbamate and titanium tetramethoxide shown below. The reaction mechanism in this case is presumed as follows. [Chemical formula] The present invention can produce a carbamate without using a sacrificial reagent or a halogenated alkyl having poor environmental compatibility. Further, as described below, the present invention can also produce a carbamate using a low-concentration carbon dioxide mixed gas as a raw material and produce a carbamate, enabling effective utilization of low-concentration carbon dioxide contained in exhaust gas and the like. Furthermore, since the present invention uses a metal alkoxide that can be regenerated with alcohol, it is possible to realize the production of a carbamate with excellent environmental compatibility in which substantially only low-concentration carbon dioxide, amine, and alcohol are consumed. Hereinafter, the method for producing the carbamate of the present invention will be described in detail.

[0011] <1-1. Carbamate having a structure represented by the formula (a-1) or (a-2)>[ By the production method according to an embodiment of the present invention, a carbamate having a structure represented by the formula (a-1) or (a-2) can be obtained. (R 1 ) R 1 each independently represents a hydrogen atom or a monovalent hydrocarbon group which may be unsubstituted or have a substituent. In the present specification, the "hydrocarbon group" is not limited to a linear saturated hydrocarbon group, and may have a carbon-carbon unsaturated bond, a branched structure, or a cyclic structure, respectively. R 1The number of carbon atoms is not particularly limited, but is usually 1 or more, and is usually 30 or less, preferably 24 or less, more preferably 20 or less. R 1 Examples of the unsubstituted hydrocarbon group represented by include alkyl groups such as ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, iso-butyl group, tert-butyl group, n-pentyl group, iso-pentyl group, neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-docosyl group; cycloalkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group; aromatic hydrocarbon groups such as phenyl group, 1-naphthyl group, 2-naphthyl group, 1-phenanthryl group, 2-phenanthryl group, 3-phenanthryl group, 4-phenanthryl group, 9-phenanthryl group, 1-anthryl group, 2-anthryl group, 9-anthryl group, 1-pyrenyl group, 2-pyrenyl group, 4-pyrenyl group, 1-triphenylenyl group, 2-triphenylenyl group; etc. R 1 When the hydrocarbon group represented by has a substituent, examples of the substituent include deuterium atom; alkyl groups having 1 to 4 carbon atoms such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, isobutyl group, tert-butyl group; cycloalkyl groups having 3 to 4 carbon atoms such as cyclopropyl group, cyclobutyl group; aromatic hydrocarbon groups having 6 to 10 carbon atoms such as phenyl group, 1-naphthyl group, 2-naphthyl group; heterocyclic groups such as oxygen-containing heterocyclic groups such as furanyl group, sulfur-containing heterocyclic groups such as thienyl group, nitrogen-containing heterocyclic groups such as pyrrolyl group, pyridyl group; hydroxyl group; alkoxy group; etc. Therefore, when the hydrocarbon group represented by R 1 has a substituent, R 1Examples thereof include aralkyl groups such as benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group; cycloalkylalkyl groups such as cyclohexylmethyl group; hydrocarbon groups having an oxygen-containing heterocyclic ring such as furfuryl group; hydrocarbon groups having a sulfur-containing heterocyclic ring such as thienylmethyl group; hydrocarbon groups having a nitrogen-containing heterocyclic ring such as pyridylmethyl group, etc. Particularly preferred is a benzyl group. When the hydrocarbon group has a substituent, the number of carbon atoms means the total number of carbon atoms of the substituent and the hydrocarbon group. R 1 Hydrogen is preferred from the viewpoint of the usefulness of the carbamate compound.

[0012] (R 2 、R 3 ) R 2 、R 3 each independently represents an unsubstituted or substituted monovalent hydrocarbon group. R 2 The number of carbon atoms of R is not particularly limited, but is usually 1 or more, and usually 30 or less, preferably 24 or less, more preferably 20 or less. R 3 The number of carbon atoms of R is not particularly limited, but is usually 1 or more, and usually 30 or less, preferably 24 or less, more preferably 20 or less. R 2 、R 3Examples of the unsubstituted hydrocarbon group represented by [[ID=]] are an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, a tert-butyl group, an n-pentyl group, an iso-pentyl group, a neopentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, an n-docosyl group and other alkyl groups; a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group and other cycloalkyl groups; a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-phenanthryl group, a 2-phenanthryl group, a 3-phenanthryl group, a 4-phenanthryl group, a 9-phenanthryl group, a 1-anthryl group, a 2-anthryl group, a 9-anthryl group, a 1-pyrenyl group, a 2-pyrenyl group, a 4-pyrenyl group, a 1-triphenylenyl group, a 2-triphenylenyl group and other aromatic hydrocarbon groups; and the like. R 2 , R 3 When the hydrocarbon group represented by [[ID=]] has a substituent, examples of the substituent include a deuterium atom; an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group; a cycloalkyl group having 3 to 4 carbon atoms such as a cyclopropyl group, a cyclobutyl group; an aromatic hydrocarbon group having 6 to 10 carbon atoms such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group; a heterocyclic group such as an oxygen-containing heterocyclic group such as a furanyl group, a sulfur-containing heterocyclic group such as a thienyl group, a nitrogen-containing heterocyclic group such as a pyrrolyl group, a pyridyl group, and the like. Therefore, when the hydrocarbon group represented by [[ID=]] has a substituent, R 2 , R 3 When the hydrocarbon group represented by [[ID=]] has a substituent, R 2 , R 3Examples thereof include aralkyl groups such as benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group; cycloalkylalkyl groups such as cyclohexylmethyl group; hydrocarbon groups having an oxygen-containing heterocycle such as furfuryl group; hydrocarbon groups having a sulfur-containing heterocycle such as thienylmethyl group; hydrocarbon groups having a nitrogen-containing heterocycle such as pyridylmethyl group, etc. Among them, a benzyl group is particularly preferable. In the case of an alkyl group in which the hydrocarbon group is branched, the number of carbon atoms in the main chain is defined as the number of carbon atoms in the hydrocarbon group. Further, when the hydrocarbon group has a substituent, the number of carbon atoms in the substituent is not included in the number of carbon atoms in the hydrocarbon group. R 2 From the viewpoint of easy availability of raw materials, it is preferably an alkyl group such as n-hexyl group; a cycloalkyl group such as cyclohexyl group; an aromatic hydrocarbon group such as phenyl group; or an aralkyl group such as benzyl group; more preferably a benzyl group, n-hexyl group, cyclohexyl group, or phenyl group; still more preferably a benzyl group or a phenyl group. R 3 From the viewpoint of easy availability of raw materials, it is preferably an alkyl group, more preferably a methyl group, ethyl group, n-propyl group, or n-butyl group.

[0013] (R 20 ) R 20 represents an unsubstituted or substituted divalent hydrocarbon group. Examples of the divalent hydrocarbon group include a methylene group; an ethylene group; a linear, branched or cyclic alkylene group having 3 or more carbon atoms; or an arylene group having 6 or more carbon atoms. The number of carbon atoms in the divalent hydrocarbon group is not particularly limited, but is preferably 2 or more, preferably 10 or less, and more preferably 7 or less. Further, the divalent hydrocarbon group may have an unsaturated bond. When the divalent hydrocarbon group has a substituent, the number of carbon atoms in the divalent hydrocarbon group means the number of carbon atoms including the number of carbon atoms in the substituent. Examples of the substituent include those exemplified in the description of item (R 1 ). R 20Specific examples include chain hydrocarbon groups such as a methylene group, an ethylene group, a tetramethylethylene group, an n-propylene group (trimethylene group), a 1-methylpropylene group, a 1,1-dimethylpropylene group, a 2-methylpropylene group, a 1,2-dimethylpropylene group, a 2,2-dimethylpropylene group, a 1,1,2-trimethylpropylene group, a 1,1,3-trimethylpropylene group, an n-butylene group (tetramethylene group), a 2-methyl-1,4-butylene group, a 3-methyl-1,4-butylene group, a 2,2-dimethyl-1,4-butylene group, a 2,3-dimethyl-1,4-butylene group, a 2,2,3-trimethyl-1,4-butylene group, an n-pentylene group (pentamethylene group), an n-hexanylene group (hexamethylene group); alicyclic hydrocarbon groups such as a 1,4-cyclohexylene group; a 1,4-phenylene group, a 1,2-phenylene group, a 1,3-phenylene group obtained by removing two hydrogen atoms from a benzene ring; aromatic hydrocarbon groups such as a dimethylphenylene group (xylyl group) obtained by removing two hydrogen atoms from the benzene ring of xylene, a methylphenylene group (tolylene group) obtained by removing two hydrogen atoms from the benzene ring of toluene, a naphthanylene group obtained by removing two hydrogen atoms from naphthalene; divalent groups composed of aliphatic hydrocarbon groups and aromatic hydrocarbon groups such as a 1,4-phenylenebis(methylene) group, a 1,4-phenylenebis(ethylene) group, a group obtained by removing one hydrogen atom from each of the two benzene rings of biphenyl, and a group obtained by removing one hydrogen atom from each of the two benzene rings of diphenylmethane.

[0014] Examples of the carbamate represented by the formula (a-1) or (a-2) include the following compounds.

Chemical formula

[0015] <1-2. Carbamate> The carbamate used in this embodiment may be any one that can produce the carbamate represented by the formula (a-1) or (a-2). That is, a hydrogen atom or a monovalent hydrocarbon group R with or without substituents 1 and a monovalent hydrocarbon group R with or without substituents2 A carbamate containing the same, or a monovalent hydrocarbon group R which is unsubstituted or has a substituent 1 and a divalent hydrocarbon group R which is unsubstituted or has a substituent 20 Any carbamate may be used. Preferably, examples include carbamates represented by the following formula (B-1) or formula (B-2).

[0016] Commercially available carbamates may be obtained and used, or they may be synthesized and used. When synthesizing, the production method is not particularly limited. For example, an amino group-containing organic compound having one or more primary or secondary amino groups, more specifically, an aliphatic monoamine such as benzylamine or hexylamine, or an aliphatic diamine such as ethylenediamine, can be used which is produced by the reaction with carbon dioxide. Also, as the carbon dioxide used in the reaction, pure carbon dioxide gas can be used, but a mixed gas containing carbon dioxide at a partial pressure of 1 atm or less, for example, a mixed gas having a carbon dioxide content of 0.01% or more by volume ratio, can also be used. In one embodiment of the present invention, it is preferably further included a carbamate generation step of generating a carbamate by bringing an amino group-containing organic compound into contact with a carbon dioxide-containing mixed gas in a solvent. The volume of carbon dioxide in the carbon dioxide-containing mixed gas is usually 0.01% or more, preferably 1% or more, more preferably 10% or more, still more preferably 15% or more, particularly preferably 20% or more, and preferably 50% or less. Carbamate production The solvent used in the forming process is not particularly limited, but hydrocarbon solvents such as hexane, benzene, and toluene can be preferably used. The reaction time may be appropriately adjusted according to the carbon dioxide partial pressure in the carbon dioxide-containing mixed gas and the reaction scale. For example, when the volume of carbon dioxide in the carbon dioxide-containing mixed gas is 15%, using 1 mmol of the amino group-containing organic compound as a raw material and reacting for 5 minutes or more and within 10 minutes, carbamate can be synthesized with a yield of 80% or more. Also, when using 40 mmol of the amino group-containing organic compound, a yield of 90 minutes or more can be achieved with a reaction time of about 180 minutes. The generated carbamate can be easily isolated by filtration.

[0017] The present inventors confirmed that as the carbamate formation step, carbamate can be formed in a high yield of, for example, 99% or more by the reaction shown in the following scheme. Also, in the synthesis using a mixed gas of low partial pressure carbon dioxide, carbamate was obtained in a high isolated yield of 93%.

Chemical formula

[0018] Although methods for producing carbamate esters using carbon dioxide as a raw material have been reported so far, all require a sacrificial reagent or an alkyl halide with poor environmental compatibility. On the other hand, in the production method of this embodiment, neither a sacrificial reagent nor an alkyl halide is used, and moreover, a mixed gas with low partial pressure of carbon dioxide can also be used. For example, the exhaust gas from a thermal power plant usually contains about 15% carbon dioxide. The method of producing carbamate using such a low-concentration carbon dioxide-containing mixed gas and then producing carbamate ester is a reaction that enables effective utilization of low-concentration carbon dioxide, is effective in reducing greenhouse gas emissions, and is a manufacturing method with excellent environmental compatibility.

[0019] <1-3. Metal alkoxide> The metal alkoxide used in this embodiment may be any one that can produce a carbamate represented by the formula (a-1) or (a-2). That is, an alkoxide group -OR 3 Any metal alkoxide containing it may be used. Preferably, a metal alkoxide represented by the formula (C-1) or (C-2) described later can be mentioned. The metal alkoxide may be obtained and used as a commercially available product, or may be synthesized and used. In addition, the metal alkoxide is a reactant that can be regenerated with alcohol. After performing the reaction step, the residue is recovered from the reaction product and can be regenerated using alcohol. The regenerated metal alkoxide may be reused in the reaction step. Therefore, as one embodiment of the present invention, a method for producing a carbamate using low-concentration carbon dioxide and substantially consuming only low-concentration carbon dioxide, amine, and alcohol, which is excellent in environmental harmony, can be provided.

[0020] <Method for Producing Carbamate Represented by Formula (A-1)> In one embodiment of the present invention, the carbamate is a carbamate represented by the formula (B-1), the metal alkoxide is a metal alkoxide represented by the formula (C-1), and the carbamate having the structure represented by the formula (a-1) is preferably a carbamate represented by the formula (A-1). [Chemical formula] In the above formula, R 11 represents a hydrogen atom or a monovalent hydrocarbon group that is unsubstituted or has a substituent; R 21 , R 31 each independently represents a monovalent hydrocarbon group that is unsubstituted or has a substituent; R 41 each independently represents a hydrocarbon ligand that is unsubstituted or has a substituent, an alkoxy ligand, an amide ligand, or a halide ligand different from -OR 31 ; M represents a metal atom or a metalloid atom; n represents the oxidation number of M, (n - m) is an integer from 1 to 6, and m represents an integer from 0 to (n - 1); Q is a q-valent represents the counter cation; q is 1 or 2.

[0021] <1-4-1. Carbamate represented by formula (A-1)> In formula (A-1), R 11 represents a hydrogen atom or a monovalent hydrocarbon group which may be unsubstituted or substituted, and R 21 , R 31 each independently represents a monovalent hydrocarbon group which may be unsubstituted or substituted. For the details of R 11 , the description of R 1 above applies. For the details of R 21 , the description of R 2 above applies. For the details of R 31 , the description of R 3 above applies.

[0022] <1-4-2. Carbamate represented by formula (B-1)> In formula (B-1), R 11 represents a hydrogen atom or a monovalent hydrocarbon group which may be unsubstituted or substituted, and R 21 , R 31 each independently represents a monovalent hydrocarbon group which may be unsubstituted or substituted, and Q represents the counter cation. R in formula (B-1) 11 corresponds to R in formula (A-1) 11 . Also, R in formula (B-1) 21 corresponds to R in formula (A-1) 21 . Also, R in formula (B-1) 31 corresponds to R in formula (A-1) 31 . Therefore, for the details of R 11 , the description of R 1 above applies. Also, for the details of R 21 , the description of R 2 above applies. For the details of R 31 , the description of R 3 above applies.

[0023] (Q) Q represents the counter cation in the carbamate and is not particularly limited as long as it is a monovalent or divalent cation. Examples include ammonium cation, amidinium cation, guanidinium cation, phosphonium cation, phosphazenium cation, carbocation, sulfonium cation, iodonium cation, alkali metal cation, alkaline earth metal cation, and the like. Examples of the ammonium cation include primary ammonium cations such as n - butylammonium cation; secondary ammonium cations such as diethylammonium cation; tertiary ammonium cations such as triethylammonium cation; and quaternary ammonium cations such as tetramethylammonium cation, phenyltrimethylammonium cation, and tetrabutylammonium cation. Examples of the amidinium cation include formamidinium cation, acetamidinium cation, 1,5 - diazabicyclo[4.3.0]non - 5 - enium cation, and 1,8 - diazabicyclo[5.4.0]undec - 7 - enium cation, which are respectively protonated forms of formamidine, acetamidine, 1,5 - diazabicyclo[4.3.0]non - 5 - ene, and 1,8 - diazabicyclo[5.4.0]undec - 7 - ene, and derivatives thereof having one or more substituents. Examples of the substituents include hydrocarbon groups such as the alkyl group, cycloalkyl group, and aromatic hydrocarbon group exemplified in the description of item (R 1 ) and the like. Examples of the guanidinium cation include protonated 1,1,3,3 - tetramethylguanidinium cation, 2 - tert - butyl - 1,1,3,3 - tetramethylguanidinium cation, 1,5,7 - triazabicyclo[4.4.0]dec - 5 - ene, and 7 - methyl - 1,5,7 - triazabicyclo[4.4.0]dec - 5 - ene, namely, 1,1,3,3 - tetramethylguanidinium cation, 2 - tert - butyl - 1,1,3,3 - tetramethylguanidinium cation, 1,5,7 - triazabicyclo[4.4.0]dec - 5 - enium cation, and 7 - methyl - 1,5,7 - triazabicyclo[4.4.0]dec - 5 - enium cation, as well as derivatives thereof having one or more substituents. Examples of the substituent include hydrocarbon groups such as the alkyl group, cycloalkyl group, and aromatic hydrocarbon group exemplified in the description of item (R 1 ). Examples of the phosphonium cation include tertiary phosphonium cations such as triphenylphosphonium cation and tritert - butylphosphonium cation; and quaternary phosphonium cations such as tetraphenylphosphonium cation, tetra - p - tolylphosphonium cation, triphenylbenzylphosphonium cation, triphenylbutyl cation, tetraethylphosphonium cation, and tetrabutylphosphonium cation. Examples of the phosphazenium cation include tert - butylimino - tris(dimethylamino)phosphorane, tert - butylimino - tri(pyrrolidino)phosphorane, 2 - tert - butylimino - 2 - diethylamino - 1,3 - dimethylperhydro - 1,3,2 - diazaphosphorin, 1 - tert - butyl - 2,2,4,4,4 - pentakis(dimethylamino)-2λ ,4λ 5 ,4λ 5 - catena - bis(phosphazene), and 1 - tert - butyl - 4, 4,4 - tris(dimethylamino)-2,2 - bis[tris(dimethylamino)phosphoranylideneamino]-2λ 5 ,4λ 5-Catenadi(phosphazene) protonated tert-butylimino-tris(dimethylamino)phosphoranium cation, t ert-butylimino-tri(pyrrolidino)phosphoranium cation, 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorinium cation, 1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2λ 5 ,4λ 5 -Catenadi(phosphazene), and 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylideneamino]-2λ 5 ,4λ 5 -Catenadi(phosphazene) onium cations and derivatives thereof having one or more substituents, etc. are exemplified. Examples of the substituents include hydrocarbon groups such as the alkyl group, cycloalkyl group, and aromatic hydrocarbon group exemplified in the description of item (R 1 ). Examples of the carbocation include monovalent carbocations such as triphenylmethyl cation, tropylium cation, and azulenium cation. Examples of the sulfonium cation include triphenylsulfonium cation, 4-(phenylthio)phenyl diphenylsulfonium cation, bis[4-(diphenylsulfonio)phenyl] sulfide, and 4-hydroxyphenylmethylbenzylsulfonium cation. Examples of the iodonium cation include diphenyliodonium cation, di-p-tolyliodonium cation, and 4-isopropylphenyl(p-tolyl)iodonium cation. Examples of the alkali metal cation include lithium cation, sodium cation, and potassium cation. Examples of the alkaline earth metal cation include magnesium cation and calcium cation. Preferably, from the viewpoint of ease of synthesis, it is an ammonium cation, an amidinium cation, a guanidinium cation, a phosphonium cation, a phosphazenium cation, a carbocation, an alkali metal cation, or an alkaline earth metal cation, more preferably an ammonium cation or an amidinium cation. Among them, preferably, it is a primary ammonium cation, a tertiary ammonium cation, or a 1,8-diazabicyclo[5.4.0]undec-7-enium cation. (q) q is 1 or 2. q indicates the number of carbamate anions and has the same value as the valence of Q. Therefore, when Q is a monovalent cation, q is 1, and when Q is a divalent cation, q is 2.

[0024] Specific examples of the carbamate represented by formula (B-1) include methylammonium N-methylcarbamate, ethylammonium N-ethylcarbamate, propylammonium N-propylcarbamate, butylammonium N-butylcarbamate, pentylammonium N-pentylcarbamate, hexylammonium N-hexylcarbamate, benzylammonium N-benzylcarbamate, phenylammonium N-phenylcarbamate, the compound represented by the following formula, and amidinium salts, guanidinium salts, phosphonium salts, phosphazenium salts, carbocation salts, alkali metal salts, or alkaline earth metal salts in which the counter cation thereof is an amidinium cation, a guanidinium cation, a phosphonium cation, a phosphazenium cation, a carbocation, an alkali metal cation, or an alkaline earth metal cation other than the 1,8-diazabicyclo[5.4.0]undec-7-enium cation, etc., but are not limited thereto. [Chemical formula]

[0025] [Metal alkoxide represented by formula (C-1) in 1-4-3.] In formula (C-1), R 31represents a monovalent hydrocarbon group with or without substituents; R 41 each independently represents a hydrocarbon ligand with or without substituents, an alkoxy ligand, an amide ligand, or a halide ligand different from -OR 31 ; M represents a metal atom or a metalloid atom; n represents the oxidation number of M, (n - m) is an integer from 1 to 6, and m represents an integer of 0 or more and (n - 1) or less. (M) M represents a metal atom or a metalloid atom. The types of metal atoms and metalloid atoms are not particularly limited. For example, metal atoms or metalloid atoms selected from the group consisting of silicon, titanium, zirconium, germanium, indium, tin, tantalum, zinc, and tungsten can be mentioned. Among them, from the viewpoint of easy availability, silicon and titanium are preferred. (R 31 ) R 31 represents a monovalent hydrocarbon group with or without substituents. R in formula (C-1) 31 corresponds to R in formula (A-1) 31 . Therefore, the details of R 31 are applicable to the description of R 3 described above. (R 41 ) R 41 each independently represents a hydrocarbon ligand with or without substituents, an alkoxy ligand, an amide ligand, or a halide ligand different from -OR 31 . Examples of unsubstituted hydrocarbon ligands include alkyl ligands such as methyl ligand and ethyl ligand, cycloalkyl ligands such as cyclohexyl ligand, aryl ligands such as phenyl ligand, naphthyl ligand, cyclopentadienyl ligand, cyclohexadienyl ligand, cyclooctadienyl ligand, cyclooctatetraenyl ligand, norbornadienyl ligand, benzyl ligand, methylcyclopentadienyl ligand, methylcyclohexadienyl ligand, Examples of aralkyl ligands such as methylcyclooctadienyl ligands and methylcyclooctatetraenyl ligands can be mentioned. Examples of substituents that the hydrocarbon ligand may have include, for example, a hydroxy group, an ester group (-COOR), an amide group (-CONRR'), a halogen atom, an alkylthio group (-SR), an amino group (-NRR'), a carboxy group, a nitro group, a sulfonic acid group (-SO3H), an oxygen-containing heterocyclic group such as a furanyl group, a sulfur-containing heterocyclic group such as a thienyl group, and a nitrogen-containing heterocyclic group such as a pyridyl group. -OR 31 Examples of unsubstituted alkoxy ligands, which are different from the above, include a methoxy ligand, an ethoxy ligand, a propoxy ligand, a butoxy ligand, a pentoxy ligand, a dodecyloxy ligand, a phenoxy ligand, and the like. Examples of substituents that the alkoxy ligand may have include, for example, a hydroxy group, an ester group (-COOR), an amide group (-CONRR'), a halogen atom, an alkylthio group (-SR), an amino group (-NRR'), a carboxy group, a nitro group, a sulfonic acid group (-SO3H), an oxygen-containing heterocyclic group such as a furanyl group, a sulfur-containing heterocyclic group such as a thienyl group, and a nitrogen-containing heterocyclic group such as a pyridyl group. Examples of amide ligands include an unsubstituted amide ligand (NH2), a methylamide ligand (NHMe), a dimethylamide ligand (NMe2), a diethylamide ligand (NEt2), a di-n-propylamide ligand (NPr2), an isopropylamide ligand, a di-n-butylamide ligand, a di-t-butylamide ligand, and the like. Examples of halide ligands include a fluorine ligand, a chlorine ligand, a bromine ligand, an iodine ligand, and the like. When m is 2 to 5, a plurality of R 41 may be the same or different, but from the viewpoint of ease of availability, all R 41 are preferably the same. (n) n represents the oxidation number of M, and (n - m) is an integer of 1 to 6. (m) m represents an integer of 0 or more and (n - 1) or less. That is, it is an integer of 0 to 5.

[0026] Specific examples of the metal alkoxide represented by formula (C-1) include tetramethoxysilane, tetraethoxysilane, tetra(n-propoxy)silane, tetra(iso-propoxy)silane, tetra(n-butoxy)silane, tetra(2-butoxy)silane, tetra(t-butoxy)silane, trimethoxy(iso-propoxy)silane, trimethoxy(n-butoxy)silane, trimethoxy(2-butoxy)silane, trimethoxy(t-butoxy)silane, trimethoxysilane, triethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, cyclohexyltripropoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, dimethoxydiethylsilane, diethoxydiethylsilane, dimethoxymethylvinylsilane, dimethoxydiphenylsilane, dimethoxymethylphenylsilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and other alkoxysilanes; tetramethoxytitanium (titanium tetramethoxide), tetraethoxytitanium, tetraallyloxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium (titanium tetra-iso-propoxide), tetra-n-butoxytitanium (titanium tetra-n-butoxide), tetraisobutoxytitanium, tetra-sec-butoxytitanium, tetra-t-butoxytitanium (titanium tetra-t-butoxide), tetra-n-pentyloxytitanium, tetracyclopentyloxytitanium, tetrahexyloxytitanium, tetracyclohexyloxytitanium, tetrabenzyloxytitanium, tetraoctyloxytitanium, tetrakis(2-ethylhexyloxy)titanium, tetradecyloxytitanium, tetradode Siloxytitanium, tetrastearyloxytitanium, tetrakis(8-hydroxyoctyloxy)titanium, diisopropoxybis(2-ethyl-1,3-hexanedionato)titanium, bis(2-ethylhexyloxy)bis(2-ethyl-1,3-hexanedionato)titanium, tetrakis(2-chloroethoxy)titanium, tetrakis(2-bromoethoxy)titanium, tetrakis(2-methoxyethoxy)titanium, tetrakis(2-ethoxyethoxy)titanium, butoxytriethoxytitanium, dibutoxydimethoxytitanium, butoxytriethoxytitanium, dibutoxydiethoxytitanium, butoxytriisopropoxytitanium, dibutoxydiisopropoxytitanium, tetraphenoxytitanium, tetrakis(o-chlorophenoxy)titanium, tetrakis(m-nitrophenoxy)titanium, tetrakis(p-methylphenoxy)titanium, tetrakis(trimethylsilyloxy)titanium, triethoxytitanium, trimethoxytitanium, triisopropoxytitanium, tributoxytitanium, methyldimethoxytitanium, ethyltriethoxytitanium, methyltriisopropoxytitanium, tetradimethylaminotitanium, dimethyltitaniumdiacetylacetonate, ethyltitaniumtriacetylacetonate, and other alkoxytitaniums; Alkoxyzirconiums such as tetramethoxyzirconium, tetraethoxyzirconium, tetraallyloxyzirconium, tetra-n-propoxyzirconium, tetraisopropoxyzirconium, tetra-n-butoxyzirconium, tetraisobutoxyzirconium, tetra-sec-butoxyzirconium, tetra-t-butoxyzirconium, tetra-n-pentyloxyzirconium, tetracyclopentyloxyzirconium, tetrahexyloxyzirconium, tetracyclohexyloxyzirconium, tetrabenzyloxyzirconium, tetraoctyloxyzirconium, tetrakis(2-ethylhexyloxy)zirconium, tetradecyloxyzirconium, tetradodecyloxyzirconium, tetrastearyloxyzirconium, tetrakis(8-hydroxyoctyloxy)zirconium, diisopropoxybis(2-ethyl-1,3-hexanedionato)zirconium, bis(2-ethylhexyloxy)bis(2-ethyl-1,3-hexanedionato)zirconium, tetrakis(2-chloroethoxy)zirconium, tetrakis(2-bromoethoxy)zirconium, tetrakis(2-methoxyethoxy)zirconium, tetrakis(2-ethoxyethoxy)zirconium, butoxytrimethoxyzirconium, dibutoxydimethoxyzirconium, butoxy-triethoxyzirconium, dibutoxydiethoxyzirconium, butoxy-triisopropoxyzirconium, dibutoxydiisopropoxyzirconium, tetraphenoxyzirconium, tetrakis(o-chlorophenoxy)zirconium, tetrakis(m-nitrophenoxy)zirconium, tetrakis(p-methylphenoxy)zirconium; Alkoxygermaniums such as tetraethoxygermanium, tetrapropoxygermanium, tetraisopropoxygermanium, tetra(n-butoxy)germanium, tetra(2-butoxy)germanium, tetra(t-butoxy)germanium; Alkoxy indiums such as tetra(n-butoxy)indium, tetra(2-butoxy)indium, tetra(t-butoxy)indium, trimethoxyindium, triethoxyindium, tri(n-propoxy)indium, triisopropoxyindium, tri(n-butoxy)indium, triisobutoxyindium, tri(t-butoxy)indium, tri(s-butoxy)indium; Alkoxy tins such as dibutyldimethoxytin, dibutyldiethoxytin, dibutyldipropoxytin; Alkoxy tantalums such as tetramethoxytantalum, tetraethoxytantalum, tetra(n-propoxy)tantalum, tetraisopropoxytantalum, tetra(n-butoxy)tantalum, tetra(2-butoxy)tantalum, tetra(t-butoxy)tantalum, pentaethoxytantalum; Alkoxy zincs such as isopropoxy zinc, tetra(n-butoxy)zinc, tetra(2-butoxy)zinc, tetra(t-butoxy)zinc; Pentamethoxytungsten, pentaethoxytungsten, pentaisopropoxyt ungsten, tungsten(V) pentabutoxytungsten, triisobutoxytungsten, tri(t-butoxy)tungsten and other alkoxy tungstens; may be mentioned. As the metal alkoxide represented by the formula (C-1), from the viewpoint of availability, it is preferably at least one selected from the group consisting of titanium compounds and silicon compounds, more preferably titanium tetramethoxide, titanium tetra-iso-propoxide, titanium tetra-n-butoxide, titanium tetra-t-butoxide, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, and still more preferably titanium tetramethoxide, titanium tetra-iso-propoxide, titanium tetra-n-butoxide, titanium tetra-t-butoxide, tetramethoxysilane. In this embodiment, a metal alkoxide compound may be introduced into the reaction system, or a metal alkoxide may be generated and used in the reaction system. For example, a method of reacting zirconium tetrachloride (ZrCl4) with sodium ethoxide to generate tetraethoxyzirconium can be mentioned. Further, a method of reacting zirconocene dichloride (Cp2ZrCl2) with sodium ethoxide to generate zirconocene diethoxide can be mentioned. Further, a method of reacting dibutyltin dichloride (Bu2SnCl2) with sodium ethoxide to generate dibutyltin diethoxide can be mentioned.

[0027] <Method for producing carbamate represented by formula (A-2)> As another embodiment of the present invention, it is preferable that the carbamate is a carbamate represented by formula (B-2), the metal alkoxide is a metal alkoxide represented by formula (C-2), and the carbamate having the structure represented by formula (a-2) is a carbamate represented by formula (A-2).

Chemical formula

[0028] <1-5-1. Carbamate represented by formula (A-2)> In formula (A-2), R 12 each independently represents a hydrogen atom or a monovalent hydrocarbon group which may be unsubstituted or have a substituent, and R 22 represents a divalent hydrocarbon group which may be unsubstituted or have a substituent, and R 32 each independently represents a monovalent hydrocarbon group which may be unsubstituted or have a substituent. For the details of R 12 , the description of R 1 above applies. For the details of R 22 , the description of R 20 above applies. For the details of R 32 , the description of R 3 above applies.

[0029] <1-5-2. Carbamate represented by formula (B-2)> In formula (B-2), R 12 each independently represents a hydrogen atom or a monovalent hydrocarbon group which may be unsubstituted or have a substituent, and R 22 represents a divalent hydrocarbon group which may be unsubstituted or have a substituent, and Q’ represents a counter cation. R in formula (B-2) 12 corresponds to R in formula (A-2) 12 . Also, R in formula (B-2) 22 corresponds to R in formula (A-2) 22 . Therefore, for the details of R 12 , the description of R 1 above applies. Also, for the details of R 22 , the description of R 2 above applies.

[0030] (Q’) Q' represents a counter cation in the carbamate, and is not particularly limited as long as it is a monovalent or divalent cation. Examples include ammonium cation, amidinium cation, guanidinium cation, phosphonium cation, phosphazenium cation, carbocation, sulfonium cation, iodonium cation, alkali metal cation, alkaline earth metal cation, etc. Specific examples of these cations include those described above in the section of (Q). Preferably, from the viewpoint of ease of synthesis, ammonium cation, amidinium cation, guanidinium cation, phosphonium cation, phosphazenium cation, carbocation, alkali metal cation, alkaline earth metal cation, and more preferably ammonium cation, amidinium cation, guanidinium cation, phosphazenium cation. Among them, preferably, tert-butylimino-tri(pyrrolidino)phosphoranium cation, 1,8-diazabicyclo[5.4.0]undec-7-enium cation. (q')[[]END]] q' is 1 or 2. (2 / q') indicates the number of counter cations Q. That is, when Q is a monovalent cation, q' is 2, and when Q is a divalent cation, q' is 1.

[0031] Specific examples of the carbamate represented by formula (B-2) include compounds represented by the following formula and their salts with counter cations such as amidinium cations, guanidinium cations, phosphonium cations, phosphazenium cations, carbocations, alkali metal cations, or alkaline earth metal cations other than 1,8-diazabicyclo[5.4.0]undec-7-enium cation, such as amidinium salts, guanidinium salts, phosphonium salts, phosphazenium salts, carbocation salts, alkali metal salts, or alkaline earth metal salts. ​Specific examples of the carbamate represented by the formula (B-2) include compounds represented by the following formula and amidinium salts, guanidinium salts, phosphonium salts, phosphazenium salts, carbocation salts, alkali metal salts, or alkaline earth metal salts in which the counter cation thereof is an amidinium cation, guanidinium cation, phosphonium cation, phosphazenium cation other than tert-butylimino-tri(pyrrolidino)phosphoranium cation, carbocation, alkali metal cation, or alkaline earth metal cation, but are not limited thereto.

Chemical formula

[0032] <1-5-3. Metal alkoxide represented by the formula (C-2)> In the formula (C-2), R 32 represents a monovalent hydrocarbon group which may be unsubstituted or have a substituent; R 42 each independently represents a hydrocarbon ligand which may be unsubstituted or have a substituent, an alkoxy ligand, an amide ligand, or a halide ligand which is different from -OR 32 ; M' represents a metal atom or a metalloid atom, n' represents the oxidation number of M', (n'-m') is an integer of 1 to 6; m' represents an integer of 0 or more and (n'-1) or less. (M') M' represents a metal atom or a metalloid atom. The types of the metal atom and the metalloid atom are not particularly limited, and examples thereof include metal atoms or metalloid atoms selected from the group consisting of silicon, titanium, zirconium, germanium, indium, tin, tantalum, zinc, and tungsten. Among them, from the viewpoint of easy availability, silicon and titanium are preferable. (R 32 ) R 32 in the formula (C-2) corresponds to R 32 in the formula (A-2). Therefore, the details of R 32 are applicable to the description of R 3 described above. (R42 ) R 42 is each independently a hydrocarbon ligand which may be unsubstituted or have a substituent, -OR 32 represents an alkoxy ligand, an amide ligand, or a halide ligand which is different from -OR and may be unsubstituted or have a substituent. A hydrocarbon ligand which may be unsubstituted or have a substituent, -OR 32 Specific examples of the alkoxy ligand, amide ligand, and halide ligand which are different from -OR and may be unsubstituted or have a substituent include the ligands exemplified by R 41 respectively. When m is 2 to 5, a plurality of R 42 may be the same or different, but from the viewpoint of ease of availability, it is preferable that all R 42 are the same. (n’) n’ represents the oxidation number of M’, and (n’ - m’) is an integer of 1 to 6. (m’) m’ represents an integer of 0 or more and (n’ - 1) or less. That is, it is an integer of 0 to 5. Specific examples of the metal alkoxide represented by the formula (C-2) include the metal alkoxides exemplified by the formula (C-1). Preferably, from the viewpoint of ease of availability, it is preferably at least one selected from the group consisting of titanium compounds and silicon compounds, more preferably titanium tetramethoxide, titanium tetra-iso-propoxide, titanium tetra-n-butoxide, titanium tetra-t-butoxide, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, and tetra-n-butoxysilane, and even more preferably titanium tetramethoxide, titanium tetra-iso-propoxide, titanium tetra-n-butoxide, titanium tetra-t-butoxide, and tetramethoxysilane.

[0033] <1-6. Reaction Step> The reaction process may include, for example, charging a carbamate of a raw material and a metal alkoxide into a sealed reaction vessel and reacting them at 200°C for 48 hours. Also, for example, an amine is placed in a sealed reaction vessel, a carbon dioxide-containing gas is blown in to produce a carbamate, and then a titanium alkoxide, which is a metal alkoxide, is added thereto and heated to cause a reaction. Hereinafter, the reaction conditions will be described.

[0034] (Reaction solvent) The reaction process may or may not use a reaction solvent, but it is preferable to use a reaction solvent. The type of the reaction solvent is not particularly limited, but ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; nitriles such as acetonitrile and propionitrile; aprotic polar solvents such as dimethylacetamide, N,N-dimethylformamide, N,N'-dimethylpropyleneurea, 1,3-dimethyl-2-imidazolidinone, and N-methylpyrrolidone are preferable. As the reaction solvent, an aprotic solvent is more preferable, ethers and aprotic polar solvents are even more preferable, and 1,4-dioxane, which is an aprotic ether, and N-methylpyrrolidone, which is an aprotic polar solvent, are particularly preferable. When the above reaction solvent is used, the carbamate can be produced more efficiently. Also, when the difference between the boiling point of the solvent and the boiling point of the product is large, it can be easily purified and the solvent can be reused. The reaction solvent may be used alone or in combination of two or more. The amount of the reaction solvent used is not particularly limited and can be appropriately selected according to the target carbamate.

[0035] (Catalyst) In one embodiment of the present invention, the reaction process may be carried out in the presence of a catalyst. In particular, when an alkoxysilane is used as the metal alkoxide, it is preferable to carry out the reaction process in the presence of a catalyst. Examples of the catalyst preferably include organic base carboxylates, alkali metal salts, zinc compounds, titanium(IV) compounds, and zirconium(IV) compounds. Examples of the organic base carboxylate include acetates of 1,8-diazabicyclo[5.4.0]undec-7-ene, acetates of 1,5-diazabicyclo[4.3.0]non-5-ene, nitrates of 1,1 ,3,3-tetramethylguanidine, and the like. Examples of the alkali metal salts include alkali metal acetates such as lithium acetate, sodium acetate, potassium acetate, rubidium acetate, and cesium acetate; alkali metal carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide; and alkali metal alkoxides such as lithium alkoxide, sodium alkoxide, potassium alkoxide, rubidium alkoxide, and cesium alkoxide. Examples of the zinc compounds include zinc halides such as zinc chloride and zinc bromide; zinc sulfate; zinc sulfonates such as p-toluenesulfonic acid zinc and trifluoromethanesulfonic acid zinc; zinc carboxylate derivatives such as zinc formate, zinc acetate, zinc propionate, zinc octanoate, zinc salicylate, zinc pivalate, zinc acrylate, p-chlorobenzoic acid zinc, zinc phenolate, zinc chloroacetate, zinc acetylacetonate, zinc oxalate, and zinc trifluoroacetate, and zinc(II)-1,10-phenanthroline complex. Examples of the titanium(IV) compounds include titanium(IV)oxysulfate·n hydrate, TiCl4, TiBr4, Ti(OC2H5)Cl3, Ti(OC5H7)Cl3, and Ti(O-iso-C4H9)Cl3. Examples of the zirconium(IV) compounds include zirconium(IV) chloride and zirconium(IV) oxychloride octahydrate. The catalyst may be formed from, for example, two or more compounds and then used. For example, zinc acetate and 1,10-phenanthroline may be put into a reaction vessel to form a zinc(II)-1,10-phenanthroline (phen) complex, which may be used as the catalyst. Among them, zinc compounds such as zinc acetate, zinc pivalate, zinc(II)-1,10-phenanthroline (phen) complex, zinc p-toluenesulfonate, and zinc trifluoromethanesulfonate are preferred, and zinc acetate and zinc(II)-1,10-phenanthroline (phen) complex are more preferred. The amount of catalyst used (charged amount) in the reaction step is not particularly limited and should be appropriately selected according to the target carbamate ester. However, it is preferably 10 mol% or more and 70 mol% or less, more preferably 50 mol% or less, based on the amount of substance of the carbamate. Also, one type of catalyst may be used, or two or more types may be used.

[0036] (Reaction temperature) The temperature of the reaction step (sometimes referred to as the "reaction temperature") is not particularly limited and may be appropriately adjusted according to the reaction scale, etc. Usually, it is 140 °C or higher, preferably 150 °C or higher, and usually 250 °C or lower, preferably 210 °C or lower.

[0037] (Reaction time) The reaction time is not particularly limited and may be appropriately adjusted according to the reaction temperature, reaction scale, etc. Usually, it is 30 minutes or more, preferably 1 hour or more, and usually 48 hours or less, preferably 24 hours or less, more preferably 20 hours or less.

[0038] (Reaction atmosphere) The atmosphere of the reaction step may be an air atmosphere or an inert gas atmosphere such as nitrogen or argon. Also, the reaction step may be carried out under any conditions of pressurization and depressurization. Usually, it is 0.01 atm or more, preferably 0.05 atm or more, more preferably 0.1 atm or more, and usually 10 atm or less, preferably 5 atm or less, more preferably 2 atm or less.

[0039] (Reaction vessel) The reaction vessel is not particularly limited and should be appropriately selected according to a continuous process or a batch process. In one embodiment of the present invention, it may be a continuous process or a batch process. In the case of a batch process, it is preferably a sealed reaction vessel (sealed reaction container), more preferably a sealed reaction container having the same volume as a mixture of a carbamate, a metal alkoxide, a reaction solvent and a catalyst as required.

[0040] (Other steps) In the method for producing a carbamate according to the present embodiment, any steps may be included in addition to the above reaction steps. Examples of optional steps include the carbamate formation step described in the section of (carbamate), the step of regenerating the metal alkoxide with alcohol, the purification step for increasing the purity of the carbamate, and the like. In the purification step, purification methods commonly used in the field of organic synthesis such as filtration, adsorption, column chromatography, distillation, etc. can be employed.

Examples

[0041] The present invention will be described more specifically with reference to the following examples, but it can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0042] <Example 1-1> To a sealed reaction vessel with a volume of 5 mL, benzylammonium N-benzylcarbamate (2.0 mmol), titanium tetramethoxide (2.0 mmol), and 1,4-dioxane (5 mL) were added, and the mixture was reacted at 200 °C for 48 hours. The yield of N-benzylcarbamic acid alkyl ester was 8%. The yield was determined by 1 1H NMR using mesitylene (50 mg) as an internal standard.

[0043] <Example 1-2> An N-benzylcarbamic acid alkyl ester was obtained in the same manner as in Example 1-1 except that the reaction temperature was changed as shown in Table 1. The yields are shown in Table 1.

[0044] <Example 1-3> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 1-2, except that the reaction time was changed as shown in Table 1. The yields are shown in Table 1.

[0045] <Example 1-4> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 1-1, except that the metal alkoxide and the amount of the solvent were changed as shown in Table 1. The yields are shown in Table 1.

[0046] <Example 1-5> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 1-4, except that the reaction temperature was changed as shown in Table 1. The yields are shown in Table 1.

[0047] <Example 1-6> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 1-5, except that the reaction temperature was changed as shown in Table 1. The yields are shown in Table 1.

[0048] <Example 1-7> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 1-1, except that the metal alkoxide and the amount of the solvent were changed as shown in Table 1. The yields are shown in Table 1.

[0049] <Example 1-8> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 1-7, except that the reaction temperature was changed as shown in Table 1. The yields are shown in Table 1.

[0050] <Example 1-9> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 1-7, except that the reaction time and the reaction temperature were changed as shown in Table 1. The yields are shown in Table 1.

[0051] <Example 1-10> An alkyl N-benzylcarbamate was obtained in the same manner as in Examples 1-7, except that the reaction temperature was changed as shown in Table 1. The yields are shown in Table 1.

[0052] <Examples 1-11> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 1-1, except that the metal alkoxide and the amount of the solvent were changed as shown in Table 1. The yields are shown in Table 1.

[0053] <Example 1-12> An alkyl N-benzylcarbamate was obtained in the same manner as in Examples 1-11, except that the reaction temperature was changed as shown in Table 1. The yields are shown in Table 1.

[0054]

Chemical formula

[0055]

Table 1

[0056] It was shown that various titanium compounds can be used as the metal alkoxide to produce an alkyl carbamate from Examples 1-1 to 1-12.

[0057] <Example 2-1> To a sealed reaction vessel with a volume of 5 mL, benzylammonium N-benzylcarbamate (2.0 mmol), tetramethoxysilane (2.0 mmol), zinc acetate (0.2 mmol), and 1,4-dioxane (4.5 mL) were added, and the mixture was reacted at 200 °C for 1 hour. The yield of methyl N-benzylcarbamate was 18%. The yield was determined by 1 1H NMR using mesitylene (50 mg) as an internal standard.

[0058] <Example 2-2> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 2-1, except that the reaction temperature was changed as shown in Table 2. The yields are shown in Table 2.

[0059] <Example 2-3> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 2-2, except that the reaction time was changed as shown in Table 2. The yields are shown in Table 2.

[0060] <Example 2-4> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 2-3, except that the reaction temperature was changed as shown in Table 2. The yields are shown in Table 2.

[0061] <Example 2-5> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 2-3, except that the catalyst was changed as shown in Table 2. The yields are shown in Table 2. In Table 2, phen represents 1,10-phenanthroline.

[0062]

Chemical formula

[0063]

Table 2

[0064] It was shown that an alkyl carbamate can be produced using a silicon compound as the metal alkoxide.

[0065] <Example 3-1> To a sealed reaction vessel with a volume of 5 mL, benzylamine (2.0 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (2.0 mmol), and 1,4-dioxane (4.5 mL) were added, and a CO2 / N2 mixed gas (v:v = 15:85) was bubbled through for 15 minutes. Subsequently, titanium tetramethoxide (2.0 mmol) was added, and the reaction was carried out at 200 °C for 1 hour. The yield of methyl N-benzylcarbamate was 50%. The yield was determined by 1 1H NMR using mesitylene (50 mg) as an internal standard.

[0066] <Example 3-2> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 3-1 except that the reaction temperature was changed as shown in Table 3. The yields are shown in Table 3.

[0067] <Example 3-3> An alkyl N-benzylcarbamate was obtained in the same manner as in Example 3-1 except that the volume ratio of the CO2 / N2 mixed gas was changed as shown in Table 3. The yields are shown in Table 3.

[0068]

Chemical formula

[0069]

Table 3

[0070] <Example 4-1> A mixed solution containing dicarbamate prepared by bubbling a carbon dioxide / nitrogen mixed gas (1 atm, v:v = 15:85) at a flow rate of 0.1 L / min for 20 minutes into a mixture of hexamethylenediamine (116 mg, 1.0 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (457 g, 3.0 mmol), and N-methylpyrrolidone (1.0 mL) was placed in a 5 mL sealed reaction vessel. Titanium tetrabutoxide (680 mg, 2.0 mmol) and N-methylpyrrolidone (3.6 mL) were added, and the mixture was reacted at 180 °C for 3 hours. The yield of N,N'-hexamethylenebis(dibutylcarbamate) was 60%. The yield was determined by 1H NMR using mesitylene (50 mg) as an internal standard. 1 Determined by 1H NMR.

[0071]

Chemical formula

[0072] <Example 4-2> A mixed solution containing carbamate prepared by bubbling a carbon dioxide / nitrogen mixed gas (1 atm, v:v = 15:85) at a flow rate of 0.1 L / min for 20 minutes into a mixture of aniline (186 mg, 2.0 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (1.52 g, 10.0 mmol), and N-methylpyrrolidone (1.5 ml) was placed in a 5 mL sealed reaction vessel. Titanium tetrabutoxide (680 mg, 2.0 mmol) and N-methylpyrrolidone (1.6 ml) were added, and the mixture was reacted at 180 °C for 3 hours. The yield of butyl-N-phenylcarbamate was 40%. The yield was determined by 1H NMR using mesitylene (50 mg) as an internal standard. 1 Determined by 1H NMR.

[0073]

Chemical formula

[0074] <Example 4-3> A mixed solution containing dicarbamate prepared by bubbling a carbon dioxide / nitrogen mixed gas (1 atm, v:v = 15:85) at a flow rate of 0.1 L / min for 20 minutes into a mixture of hexamethylenediamine (116 mg, 1.0 mmol), tert-butylimino-tris(pyrrolidino)phosphorane (1250 mg, 4.0 mmol), and N-methylpyrrolidone (2.0 ml) was placed in a 5 mL sealed reaction vessel. Titanium tetrabutoxide (680 mg, 2.0 mmol) and N-methylpyrrolidone (3.6 ml) were added, and the mixture was reacted at 180 °C for 3 hours. The yield of N,N'-hexamethylenebis(dibutylcarbamate) was 52%. The yield was determined by 1H NMR using mesitylene (50 mg) as an internal standard. 1 Determined by 1H NMR. [Chemical formula]

[0075] It was shown that an alkyl carbamate can be produced by adding a titanium alkoxide, which is a metal alkoxide, to a reaction system that generates carbamate using an amine and carbon dioxide as raw materials and reacting them. Moreover, it was shown that an alkyl carbamate can be produced using a low-concentration carbon dioxide gas with a carbon dioxide volume of 15% in the carbon dioxide-containing mixed gas. [Industrial Applicability]

[0076] According to the present invention, a carbamic acid ester can be produced using a carbamate and a metal alkoxide as raw materials. Further, the present invention can produce a carbamate using a low-concentration carbon dioxide mixed gas as a raw material and then produce a carbamic acid ester, which enables the effective utilization of low-concentration carbon dioxide contained in exhaust gas and the like. Furthermore, the metal alkoxide used in the present invention can be recovered after the reaction and then regenerated using alcohol, so that substantially only low-concentration carbon dioxide, amine, and alcohol are consumed, and it is a reaction with excellent environmental compatibility.

Claims

1. A process for producing a carbamate, comprising a reaction step of producing a carbamate represented by the following formula (A-1) or (A-2) from a carbamate represented by the following formula (B-1) or (B-2) and an alkoxysilane (however, excluding those carried out in the presence of a zinc compound). 【Chemical 1】 【Chemical Formula 2】 (In the above formula, R １１ represents a hydrogen atom or a monovalent hydrocarbon group which may be unsubstituted or substituted; R ２１ , R ３１ each independently represent a monovalent hydrocarbon group which may be unsubstituted or substituted; R １２ each independently represent a hydrogen atom or a monovalent hydrocarbon group which may be unsubstituted or substituted; R ２２ represents a divalent hydrocarbon group which may be unsubstituted or substituted; R ３２ each independently represent a monovalent hydrocarbon group which may be unsubstituted or substituted; Q represents a q-valent counter cation; q is 1 or 2; Q' represents a (2 / q')-valent counter cation; q' is 1 or 2.)

2. The method for producing a carbamate according to claim 1, wherein the carbamate is a carbamate represented by the formula (B-1), the alkoxysilane is an alkoxysilane represented by the following formula (C-1), and the carbamate is a carbamate represented by the formula (A-1). [Chemical 3] (In the above formula, R ３１ each independently represents a monovalent hydrocarbon group which is unsubstituted or has a substituent; R ４１ each independently represents a hydrocarbon ligand which is unsubstituted or has a substituent, an alkoxy ligand, an amide ligand, or a halide ligand different from -OR ３１ ; M represents silicon; n is 4; (n - m) is an integer of 1 to 4; and m represents an integer of 0 to 3.)

3. The method for producing a carbamate according to claim 1 or 2, wherein Q is a cation selected from the group consisting of an ammonium cation, an amidinium cation, a guanidinium cation, a phosphonium cation, a phosphazenium cation, a carbocation, an alkali metal cation, and an alkaline earth metal cation.

4. The carbamate is a carbamate represented by the formula (B-2), the alk oxysilane is an alkoxysilane represented by the following formula (C-2), and the carbamate is a carbamate represented by the formula (A-2). The method for producing a carbamate according to claim 1. 【Chemical 4】 (In the above formula, R ３２ each independently represents a monovalent hydrocarbon group which may be unsubstituted or have a substituent; R ４２ each independently represents a hydrocarbon ligand which may be unsubstituted or have a substituent, an alkoxy ligand, an amide ligand, or a halide ligand different from -OR ３２ ; M' represents silicon, n' is 4; (n' - m') is an integer of 1 to 4; m' represents an integer of 0 to 3.)

5. The method for producing a carbamate according to claim 1 or 4, wherein Q' is a cation selected from the group consisting of an ammonium cation, an amidinium cation, a guanidinium cation, a phosphonium cation, a phosphazenium cation, a carbocation, an alkali metal cation, and an alkaline earth metal cation.

6. The method for producing a carbamate according to any one of claims 1 to 5, wherein the reaction step is carried out in the presence of an aprotic solvent.

7. The method for producing a carbamate according to any one of claims 1 to 6, further comprising a carbamate formation step of forming the carbamate by contacting an amino group-containing organic compound with a carbon dioxide-containing mixed gas in the presence of a base in a solvent, wherein the volume of carbon dioxide in the carbon dioxide-containing mixed gas is 0.01% or more.

Images