Method for producing carbamic acid esters

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] This invention relates to a method for producing carbamic acid esters. [Background technology]

[0002] Carbamic acid esters are useful compounds with a wide range of applications as pharmaceuticals, agrochemicals, various fine chemicals, and raw materials for their synthesis.

[0003] To date, methods for producing carbamic acid esters using carbon dioxide at atmospheric pressure have been proposed. For example, Non-Patent Document 1 describes a method for synthesizing carbamate derivatives, which involves the in situ synthesis of ammonium carbamate, equivalent to an amine, as a carbonyl source, by the reaction of an amine with CO2. A multicomponent synthesis using triphenylphosphine and an equivalent amount of trichloroisocyanuric acid (TCCA) is being investigated. Non-patent document 1 uses CO2 gas at 1 atmosphere and employs a non-renewable sacrificial reagent. Non-patent document 2 reports a method for synthesizing carbamic acid esters via carbamic acid using 1,8-diazabicyclo[5.4.0]undeca-7-ene as a catalyst, with CO2 gas at 1 atmosphere. Non-patent document 2 uses PBu3 and DBAD (azodicarboxylate di-tert-butyl) as non-renewable sacrificial reagents. Non-patent document 3 reports the synthesis of carbamic acid esters from amines and CO2 gas using non-renewable sacrificial reagents such as KO2 / Et4NBr. Non-patent document 4 reports the synthesis of carbamic acid esters via the Mitsunobu reaction using CO2 gas at 1 atmosphere, carbamic acid, and sacrificial reagents Ph3P and DEAD (diethyl azodicarboxylate). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] SSE Ghodsinia, B. Akhlaghinia, Phosphorus Sulfur Silicon Relat. Elem., 2016, vol.191, p.1-7 [Non-Patent Document 2] Scott L. Peterson, Sabrina M. Stucka, Christopher J. Dinsmore, Org. Lett. 2010, 12, p.1340-1343 [Non-Patent Document 3] Krishna Nand Singh, Synth. Commun. 2007, 37, p.2651-2654 [Non-Patent Document 4] Devdutt Chaturvedi, Nisha Mishra, Virendra Mishra, Monats. Chem. 2007, 138, p.57-60 [Overview of the project] [Problems that the invention aims to solve]

[0005] All of the above methods for producing carbamic acid esters require either a sacrificial reagent or an alkyl halide that is not environmentally compatible. The object of this invention is to provide a method for producing carbamate esters using carbamate salts as raw materials, without using sacrificial reagents or alkyl halides. [Means for solving the problem]

[0006] The inventors of this invention conducted extensive research to solve the above problems and, as a result, discovered that a carbamate ester can be produced from a carbamate salt and a metal alkoxide, thus completing the present invention. The present invention provides the following specific embodiments, etc. [1] From a carbamate salt and a metal alkoxide, the following formula (a-1) or (a-2) A method for producing a carbamic acid ester, characterized by producing a carbamic acid ester having the structure represented by . [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, and 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 ; 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 method for producing a carbamic acid ester according to [1], wherein the carbamic acid salt is a carbamic acid salt represented by formula (B-2), the metal alkoxide is a metal alkoxide represented by formula (C-2), and the carbamic acid ester having the structure represented by formula (a-2) is a carbamic acid ester represented by formula (A-2). [ka] (In the above formula, R 12 Each of these independently represents a hydrogen atom or a monovalent hydrocarbon group that is unsubstituted or substituted; R 22 R represents an unsubstituted or substituted divalent hydrocarbon group; 32 Each of these independently represents an unsubstituted or substituted monovalent hydrocarbon group; R 42 Each of these is independently an unsubstituted or substituted hydrocarbon ligand, -OR 32 This represents an unsubstituted or substituted alkoxy ligand, amide ligand, or halide ligand, which is different from the above; M' represents a metal atom or metalloid atom, and n' represents the oxidation state of M', ( n'-m') is an integer between 1 and 6; m' represents an integer greater than or equal to 0 and less than or equal to (n'-1); Q ' represents a (2 / q') valence countercation; q' is either 1 or 2. [5] The method for producing a carbamic acid ester according to [4], wherein Q' is a cation selected from the group consisting of ammonium cation, amidinium cation, guanidinium cation, phosphonium cation, phosphazenium cation, carbocation, alkali metal cation, and alkaline earth metal cation. [6] Preparation of 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 titanium compounds and silicon compounds. Construction method. [7] A method for producing a carbamic acid ester according to any one of [1] to [6], wherein the metal alkoxide is an 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 carbamic acid esters as described in [7]. [9] A method for producing a carbamic acid ester according to any one of [1] to [8], wherein the reaction step is carried out in the presence of an aprotic solvent.

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

[0007] According to the present invention, a method for producing carbamic acid esters using carbamic acid salts as raw materials without using sacrificial reagents or alkyl halides is provided. [Modes for carrying out the invention]

[0008] In describing the details of the present invention, specific examples will be given, but the invention is not limited to the following, and can be implemented with appropriate modifications, as long as it does not deviate from the spirit of the invention.

[0009] <1. Method for producing carbamic acid esters> A method for producing a carbamic acid ester according to one embodiment of the present invention is characterized by comprising a reaction step (hereinafter sometimes abbreviated as "reaction step") in which a carbamic acid ester having a structure represented by the following formula (a-1) or (a-2) is produced from a carbamic acid salt and a metal alkoxide. [ka] (In the above formula, R 1 Each of these independently represents a hydrogen atom or a monovalent hydrocarbon group that is unsubstituted or substituted, and R 2 , R3 Each of these independently represents an unsubstituted or substituted monovalent hydrocarbon group, and R 20 (This represents an unsubstituted or substituted divalent hydrocarbon group.)

[0010] Reactions that produce carbamic acid esters having a structure represented by formula (a-1) or (a-2) from a carbamate salt and a metal alkoxide include, for example, the reaction between benzylammonium N-benzylcarbamate and titanium tetramethoxide, as shown below. The reaction mechanism in this case is presumed to be as follows. [ka] The present invention enables the production of carbamic acid esters without using sacrificial reagents or alkyl halides, which have poor environmental compatibility. Furthermore, as will be described later, the present invention can also produce carbamate salts and carbamic acid esters using a low-concentration carbon dioxide mixed gas as a raw material, enabling the effective utilization of low-concentration carbon dioxide contained in exhaust gases, etc. Moreover, since the present invention uses metal alkoxides that can be recycled with alcohol, it is possible to produce carbamic acid esters with excellent environmental compatibility, where essentially only low-concentration carbon dioxide, amines, and alcohols are consumed. The method for producing carbamic acid esters according to the present invention will be described in detail below.

[0011] <1-1. Carbamic acid esters having a structure represented by formula (a-1) or (a-2)> A carbamic acid ester having the structure represented by formula (a-1) or (a-2) can be obtained by a manufacturing method according to one embodiment of the present invention. (R 1 ) R 1 Each of these independently represents a hydrogen atom or a monovalent hydrocarbon group that is either unsubstituted or substituted. In this specification, the term "hydrocarbon group" is not limited to a linear saturated hydrocarbon group, but may also have carbon-carbon unsaturated bonds, branched structures, or cyclic structures. 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, and more preferably 20 or less. R 1 Unsubstituted hydrocarbon groups represented by include 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- Examples include alkyl groups such as docosyl groups; cycloalkyl groups such as cyclopropyl groups, cyclobutyl groups, cyclopentyl groups, and cyclohexyl groups; aromatic hydrocarbon groups such as phenyl groups, 1-naphthyl groups, 2-naphthyl groups, 1-phenanthryl groups, 2-phenanthryl groups, 3-phenanthryl groups, 4-phenanthryl groups, 9-phenanthryl groups, 1-anthryl groups, 2-anthryl groups, 9-anthryl groups, 1-pyrenyl groups, 2-pyrenyl groups, 4-pyrenyl groups, 1-triphenylenyl groups, and 2-triphenylenyl groups. R 1 When the hydrocarbon group represented by has substituents, the substituents include: deuterium atoms; C1-C4 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl groups; C3-C4 cycloalkyl groups such as cyclopropyl and cyclobutyl groups; C6-C10 aromatic hydrocarbon groups such as phenyl, 1-naphthyl, and 2-naphthyl groups; and oxygen-containing heterocyclic groups such as furanyl groups. Examples include heterocyclic groups such as sulfur-containing heterocyclic groups like thienyl groups, nitrogen-containing heterocyclic groups like pyrrolyl and pyridyl groups; hydroxyl groups; and alkoxy groups. Therefore, R 1 When the hydrocarbon group represented by R has substituents, 1Examples of preferred groups include aralkyl groups such as benzyl, phenethyl, 1-naphthylmethyl, and 2-naphthylmethyl; cycloalkylalkyl groups such as cyclohexylmethyl; hydrocarbon groups having oxygen-containing heterocycles such as furfuryl; hydrocarbon groups having sulfur-containing heterocycles such as thienylmethyl; and hydrocarbon groups having nitrogen-containing heterocycles such as pyridylmethyl. Particularly preferred is the benzyl group. Furthermore, if the hydrocarbon group has substituents, the carbon number refers to the sum of the carbon numbers of the substituents and the hydrocarbon group. R 1 From the viewpoint of the usefulness of the carbamate ester compound, hydrogen is preferred.

[0012] (R 2 , R 3 ) R 2 , R 3 Each of these independently represents a monovalent hydrocarbon group that is either unsubstituted or substituted. R 2 The number of carbon atoms is not particularly limited, but is usually 1 or more, and is usually 30 or less, preferably 24 or less, and more preferably 20 or less. R 3 The number of carbon atoms is not particularly limited, but is usually 1 or more, and is usually 30 or less, preferably 24 or less, and more preferably 20 or less. R 2 , R 3Unsubstituted hydrocarbon groups represented by include 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- Examples include alkyl groups such as docosyl groups; cycloalkyl groups such as cyclopropyl groups, cyclobutyl groups, cyclopentyl groups, and cyclohexyl groups; aromatic hydrocarbon groups such as phenyl groups, 1-naphthyl groups, 2-naphthyl groups, 1-phenanthryl groups, 2-phenanthryl groups, 3-phenanthryl groups, 4-phenanthryl groups, 9-phenanthryl groups, 1-anthryl groups, 2-anthryl groups, 9-anthryl groups, 1-pyrenyl groups, 2-pyrenyl groups, 4-pyrenyl groups, 1-triphenylenyl groups, and 2-triphenylenyl groups. R 2 , R 3 When the hydrocarbon group represented by has substituents, examples of substituents include deuterium atoms; C1-C4 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl groups; C3-C4 cycloalkyl groups such as cyclopropyl and cyclobutyl groups; C6-C10 aromatic hydrocarbon groups such as phenyl, 1-naphthyl, and 2-naphthyl groups; heterocyclic groups such as oxygen-containing heterocyclic groups such as furanyl groups, sulfur-containing heterocyclic groups such as thienyl groups, and nitrogen-containing heterocyclic groups such as pyrrolyl and pyridyl groups. Therefore, R 2 , R 3 When the hydrocarbon group represented by R has substituents, 2 , R 3Examples of preferred groups include aralkyl groups such as benzyl, phenethyl, 1-naphthylmethyl, and 2-naphthylmethyl; cycloalkylalkyl groups such as cyclohexylmethyl; hydrocarbon groups having oxygen-containing heterocycles such as furfuryl; hydrocarbon groups having sulfur-containing heterocycles such as thienylmethyl; and hydrocarbon groups having nitrogen-containing heterocycles such as pyridylmethyl. Particularly preferred is the benzyl group. In the case of a branched alkyl group, the number of carbon atoms in the main chain is considered to be the number of carbon atoms in the hydrocarbon group. Furthermore, if the hydrocarbon group has substituents, the number of carbon atoms in the substituents is not included in the calculation of the hydrocarbon group's carbon count. R 2 Preferably, the group is an alkyl group such as an n-hexyl group; a cycloalkyl group such as a cyclohexyl group; an aromatic hydrocarbon group such as a phenyl group; or an aralkyl group such as a benzyl group; more preferably a benzyl group, an n-hexyl group, a cyclohexyl group, or a phenyl group; and even more preferably a benzyl group or a phenyl group. R 3 From the standpoint of ease of obtaining raw materials, alkyl groups are preferred, and more preferably methyl groups, ethyl groups, n-propyl groups, and n-butyl groups.

[0013] (R 20 ) R 20 This represents an unsubstituted or substituted divalent hydrocarbon group. Examples of divalent hydrocarbon groups include methylene groups; ethylene groups; linear, branched, or cyclic alkylene groups having 3 or more carbon atoms; or arylene groups 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. The divalent hydrocarbon group may also have unsaturated bonds. Note that if the divalent hydrocarbon group has substituents, the number of carbon atoms in the divalent hydrocarbon group refers to the number of carbon atoms including those of the substituents. Substituents include item (R 1 Examples can be found in the explanation of ). R 20Specifically, these include chain-like hydrocarbon groups such as methylene group, ethylene group, tetramethylethylene group, n-propylene group (trimethylene group), 1-methylpropylene group, 1,1-dimethylpropylene group, 2-methylpropylene group, 1,2-dimethylpropylene group, 2,2-dimethylpropylene group, 1,1,2-trimethylpropylene group, 1,1,3-trimethylpropylene group, n-butylene group (tetramethylene group), 2-methyl-1,4-butylene group, 3-methyl-1,4-butylene group, 2,2-dimethyl-1,4-butylene group, 2,3-dimethyl-1,4-butylene group, 2,2,3-trimethyl-1,4-butylene group, n-pentylene group (pentamethylene group), n-hexanylene group (hexamethylene group); 1,4- Examples include alicyclic hydrocarbon groups such as chlorohexylene groups, 1,4-phenylene groups, 1,2-phenylene groups, and 1,3-phenylene groups obtained by removing two hydrogen atoms from a benzene ring; aromatic hydrocarbon groups such as dimethylphenylene (xylyl group) obtained by removing two hydrogen atoms from the benzene ring of xylene, methylphenylene (trylene group) obtained by removing two hydrogen atoms from the benzene ring of toluene, and naphthalylene groups obtained by removing two hydrogen atoms from naphthalene; and divalent groups consisting of aliphatic hydrocarbon groups and aromatic hydrocarbon groups such as 1,4-phenylenebis(methylene) groups, 1,4-phenylenebis(ethylene) groups, groups obtained by removing one hydrogen atom from each of the two benzene rings of biphenyl, and groups obtained by removing one hydrogen atom from each of the two benzene rings of diphenylmethane.

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

[0015] <1-2. Carbamate> The carbamate salt used in this embodiment can be any one capable of producing a carbamate ester represented by formula (a-1) or (a-2). That is, a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group R 1 and unsubstituted or substituted monovalent hydrocarbon groups R2 Carbamate salts containing or unsubstituted or substituted monovalent hydrocarbon groups R 1 and unsubstituted or substituted divalent hydrocarbon groups R 20 Any carbamate containing the specified compound is acceptable. Preferably, a carbamate represented by formula (B-1) or formula (B-2) described below is included.

[0016] Carbamate salts may be obtained commercially or synthesized. When synthesized, the manufacturing method is not particularly limited, but for example, an amino group-containing organic compound having one or more primary or secondary amino groups, more specifically, one produced by the reaction of an aliphatic monoamine such as benzylamine or hexylamine, or an aliphatic diamine such as ethylenediamine, with carbon dioxide can be used. As for 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 atmosphere or less, for example, a mixed gas with a carbon dioxide content of 0.01% or more by volume, can also be used. In one embodiment of the present invention, it is preferable to further include a carbamate salt production step in which an amino group-containing organic compound is brought into contact with a carbon dioxide-containing mixed gas in a solvent to produce a carbamate salt. 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, even more preferably 15% or more, particularly preferably 20% or more, and preferably 50% or less. The solvent used in the synthesis process is not particularly limited, but hydrocarbon solvents such as hexane, benzene, and toluene can be preferably used. The reaction time can be appropriately adjusted according to the partial pressure of carbon dioxide in the carbon dioxide-containing gas mixture and the reaction scale. For example, if the volume of carbon dioxide in the carbon dioxide-containing gas mixture is 15%, a carbamate salt can be synthesized with a yield of 80% or more by reacting 1 mmol of an amino group-containing organic compound as a starting material for 5 to 10 minutes. Also, when using 40 mmol of an amino group-containing organic compound, a yield of 90 minutes or more can be achieved with a reaction time of about 180 minutes. The resulting carbamate salt can be easily isolated by filtration.

[0017] The inventors have confirmed that carbamate salts can be produced in a high yield of, for example, 99% or more, by the reaction shown in the following scheme as a carbamate salt production step. Furthermore, carbamate salts were also obtained in a high isolation yield of 93% in synthesis using a mixed gas of low partial pressure carbon dioxide. [ka]

[0018] While methods for producing carbamic acid esters using carbon dioxide as a raw material have been reported previously, they all require either a sacrificial reagent or an alkyl halide, which is not environmentally friendly. In contrast, the production method of this embodiment does not require a sacrificial reagent or an alkyl halide, and can even use a mixed gas containing carbon dioxide at a low partial pressure. For example, exhaust gas from thermal power plants typically contains about 15% carbon dioxide. A method for producing carbamate salts and then carbamic acid esters using such a low-concentration carbon dioxide-containing mixed gas is a reaction that enables the effective utilization of low-concentration carbon dioxide, is effective in reducing greenhouse gas emissions, and is an environmentally friendly production method.

[0019] <1-3. Metal Alkoxides> The metal alkoxide used in this embodiment can be any one capable of producing a carbamic acid ester represented by formula (a-1) or (a-2). That is, an alkoxide group-OR 3 Any metal alkoxide containing the specified compound is acceptable. Preferably, a metal alkoxide represented by formula (C-1) or (C-2) described below is used. The metal alkoxide may be obtained commercially or synthesized. Furthermore, metal alkoxides are regenerative reagents that can be recycled with alcohol. After the reaction process, the residue can be recovered from the reaction product and recycled using alcohol. The recycled metal alkoxide can then be reused in the reaction process. Therefore, as one embodiment of the present invention, it is possible to provide an environmentally friendly method for producing carbamate esters using low-concentration carbon dioxide, where substantially only low-concentration carbon dioxide, amines, and alcohols are consumed.

[0020] <1-4. Method for producing carbamic acid ester represented by formula (A-1)> In one embodiment of the present invention, it is preferable that the carbamate salt is a carbamate salt represented by formula (B-1), the metal alkoxide is a metal alkoxide represented by formula (C-1), and the carbamate ester having the structure represented by formula (a-1) is a carbamate ester represented by formula (A-1). [ka] In the above formula, R 11 R represents a hydrogen atom or a monovalent hydrocarbon group that is unsubstituted or substituted; 21 , R 31 Each of these independently represents an unsubstituted or substituted monovalent hydrocarbon group; R 41 Each of these is independently an unsubstituted or substituted hydrocarbon ligand, -OR 31 This represents an unsubstituted or substituted alkoxy ligand, amide ligand, or halide ligand, distinct from the above; M represents a metal atom or metalloid atom; n represents the oxidation state of M, where (nm) is an integer from 1 to 6; m represents an integer between 0 and (n-1); and Q is the q-valence. represents a 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 is unsubstituted or has a substituent, and R 21 , R 31 each independently represents a monovalent hydrocarbon group which is unsubstituted or has a substituent. Details of R 11 are as described above for R 1 . Details of R 21 are as described above for R 2 . Details of R 31 are as described above for R 3 .

[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 is unsubstituted or has a substituent, and R<s 21 , R 31 each independently represents a monovalent hydrocarbon group which is unsubstituted or has a substituent, and Q represents a 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, details of R 11 are as described above for R 1 . Also, details of R 21 are as described above for R 2 . Details of R 31 are as described above for R 3 .

[0023] (Q) Q represents the countercation in the carbamate salt, and is not particularly limited as long as it is a monovalent or divalent cation, but 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. Examples of ammonium cations 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 amidinium cations include formamidinium cation, acetamidinium cation, 1,5-diazabicyclo[4.3.0]non-5-ene cation, and 1,8-diazabicyclo[5.4.0]undecé-7-ene cation, which are obtained by protonating formamidinium, acetamidinium cation, 1,5-diazabicyclo[4.3.0]non-5-enium cation, and 1,8-diazabicyclo[5.4.0]undecé-7-enium cation, as well as derivatives thereof having one or more substituents. Examples of the substituents include item (R 1 ) Examples of hydrocarbon groups such as alkyl groups, cycloalkyl groups, and aromatic hydrocarbon groups as illustrated in the explanation. These are some examples. Examples of guanidinium cations include 1,1,3,3-tetramethylguanidinine, 2-tert-butyl-1,1,3,3-tetramethylguanidinine, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, and 7-methyl-1,5,7-triazabicyclo[4.4.0]deca-5-ene, which are protonated, as well as derivatives thereof having one or more substituents. 1 Examples of hydrocarbon groups include alkyl groups, cycloalkyl groups, aromatic hydrocarbon groups, etc., as illustrated in the explanation of ). Examples of phosphonium cations include tertiary phosphonium cations such as triphenylphosphonium cation and tri-tert-butylphosphonium cation; and quaternary phosphonium cations such as tetraphenylphosphonium cation, tetra-p-tolylphosphonium cation, triphenylbenzylphosphonium cation, triphenylbutyl cation, tetraethylphosphonium cation, and tetrabutylphosphonium cation. As for phosphazenium cations, tert-butylimino-tris(dimethylami (n)phosphoranes, tert-butylimino-tri(pyrrolidino)phosphoranes, 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine, 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) 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. 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, ammonium cations, amidinium cations, guanidinium cations, phosphonium cations, phosphazenium cations, carbocations, alkali metal cations, and alkaline earth metal cations are used, and more preferably ammonium cations or amidinium cations. Among these, primary ammonium cations are preferred. These are a nium cation, a tertiary ammonium cation, and a 1,8-diazabicyclo[5.4.0]undecé-7-enium cation. (q) q is either 1 or 2. q represents the number of carbamate anions and is the same value as the valence of Q. Therefore, if Q is a monovalent cation, q is 1, and if Q is a divalent cation, q is 2.

[0024] Specific examples of carbamates represented by formula (B-1) include, but are not limited to, amidinium salts, guanidinium salts, phosphonium salts, phosphazenium salts, carbocation salts, alkali metal salts, or alkaline earth metal salts, where the counter cation of these is an amidinium cation other than the 1,8-diazabicyclo[5.4.0]undecé-7-enium cation, guanidinium salt, phosphonium salt, phosphazenium salt, carbocation salt, alkali metal salt, or alkaline earth metal salt. [ka]

[0025] <1-4-3. Metal alkoxides represented by formula (C-1)> 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, and (n - m) is an integer from 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 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 preferable. (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 include methylcyclooctadienyl ligands and methylcyclooctatetraenyl ligands. Examples of substituents that hydrocarbon ligands may have include oxygen-containing heterocyclic groups such as hydroxyl groups, ester groups (-COOR), amide groups (-CONRR'), halogen atoms, alkylthio groups (-SR), amino groups (-NRR'), carboxyl groups, nitro groups, sulfonic acid groups (-SO3H), and furanyl groups, sulfur-containing heterocyclic groups such as thienyl groups, and nitrogen-containing heterocyclic groups such as pyridyl groups. -OR 31 Examples of unsubstituted alkoxy ligands, distinct from those mentioned above, include methoxy ligands, ethoxy ligands, propoxy ligands, butoxy ligands, pentoxy ligands, dodecyloxy ligands, and phenoxy ligands. Examples of substituents that alkoxy ligands may have include hydroxyl groups, ester groups (-COOR), amide groups (-CONRR'), halogen atoms, alkylthio groups (-SR), amino groups (-NRR'), carboxyl groups, nitro groups, sulfonic acid groups (-SO3H), oxygen-containing heterocyclic groups such as furanyl groups, sulfur-containing heterocyclic groups such as thienyl groups, and nitrogen-containing heterocyclic groups such as pyridyl groups. Examples of amide ligands include unsubstituted amide ligands (NH2), methylamide ligands (NHMe), dimethylamide ligands (NMe2), diethylamide ligands (NEt2), di-n-propylamide ligands (NPr2), isopropylamide ligands, di-n-butylamide ligands, and di-t-butylamide ligands. Examples of halide ligands include fluorine ligands, chlorine ligands, bromine ligands, and iodine ligands. If m is between 2 and 5, there are multiple R 41 They may be the same or different, but in terms of ease of acquisition, all R 41 It is preferable that they are the same. (n) n represents the oxidation number of M, and (nm) is an integer between 1 and 6. (m) m represents an integer between 0 and (n-1), i.e., an integer between 0 and 5.

[0026] Specifically, the metal alkoxide represented by formula (C-1) is: 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, propyl Alkoxysilanes such as riethoxysilane, propyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, cyclohexyltripropoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, dimethoxydiethylsilane, diethoxydiethylsilane, dimethoxymethylvinylsilane, dimethoxydiphenylsilane, dimethoxymethylphenylsilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane; 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, tetradodecyl Siloxytitanium, tetrastearyloxytitanium, tetrakis(8-hydroxyoctyloxy)titanium, diisopropoxybis(2-ethyl-1,3-hexanediolato)titanium, bis(2-ethylhexyloxy)bis(2-ethyl-1,3-hexanediolato)titanium, tetrakis(2-chloroethoxy)titanium, tetrakis(2-bromoethoxy)titanium, tetrakis(2-methoxyethoxy)titanium, tetrakis(2-ethoxyethoxy)titanium, butoxytrimethoxytitanium, dibutoxydimethoxytitanium, butoxytriethoxytitanium, dibutoxydiethoxytitanium, butoxytri Alkoxy titanium compounds such as sopropoxytitanium, 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, dimethyltitanium diacetylacetonate, and ethyltitanium triacetylacetonate; 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 Alkoxyzirconiums such as (2-ethyl-1,3-hexanediolato)zirconium, bis(2-ethylhexyloxy)bis(2-ethyl-1,3-hexanediolato)zirconium, tetrakis(2-chloroethoxy)zirconium, tetrakis(2-bromoethoxy)zirconium, tetrakis(2-methoxyethoxy)zirconium, tetrakis(2-ethoxyethoxy)zirconium, butoxytrimethoxyzirconium, dibutoxydimethoxyzirconium, butoxytriethoxyzirconium, dibutoxydiethoxyzirconium, butoxytriisopropoxyzirconium, dibutoxydiisopropoxyzirconium, tetraphenoxyzirconium, tetrakis(o-chlorophenoxy)zirconium, tetrakis(m-nitrophenoxy)zirconium, and tetrakis(p-methylphenoxy)zirconium; Alkoxygermaniums such as tetraethoxygermanium, tetrapropoxygermanium, tetraisopropoxygermanium, tetra(n-butoxy)germanium, tetra(2-butoxy)germanium, and tetra(t-butoxy)germanium; Alkoxyindium 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, and tri(s-butoxy)indium; Alkoxytins such as dibutyldimethoxytin, dibutyldiethoxytin, and dibutyldipropoxytin; Alkoxytantalums such as tetramethoxytantalum, tetraethoxytantalum, tetra(n-propoxy)tantalum, tetraisopropoxytantalum, tetra(n-butoxy)tantalum, tetra(2-butoxy)tantalum, tetra(t-butoxy)tantalum, and pentaethoxytantalum; Alkoxyzincs such as isopropoxyzinc, tetra(n-butoxy)zinc, tetra(2-butoxy)zinc, and tetra(t-butoxy)zinc; Pentamethoxytungsten, pentaethoxytungsten, pentaisopropoxy Alkoxytungstens such as tungsten, tungsten(V)pentabutoxytungsten, triisobutoxytungsten, and tri(t-butoxy)tungsten; These are some examples. The metal alkoxide represented by formula (C-1) is preferably at least one selected from the group consisting of titanium compounds and silicon compounds, from the viewpoint of availability, 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 even more preferably titanium tetramethoxide, titanium tetra-iso-propoxide, titanium tetra-n-butoxide, titanium tetra-t-butoxide, and tetramethoxysilane. In this embodiment, a metal alkoxide compound may be added to the reaction system, or a metal alkoxide may be generated in the reaction system and used. For example, one method is to react zirconium tetrachloride (ZrCl4) with sodium ethoxide to generate tetraethoxyzirconium. Another method is to react zirconocene dichloride (Cp2ZrCl2) with sodium ethoxide to generate zirconocene diethoxide. Yet another method is to react dibutyldichlorotin (Bu2SnCl2) with sodium ethoxide to generate dibutyldiethoxytin.

[0027] <1-5. Method for producing carbamic acid ester represented by formula (A-2)> Furthermore, in another embodiment of the present invention, it is preferable that the carbamate salt is a carbamate salt represented by formula (B-2), the metal alkoxide is a metal alkoxide represented by formula (C-2), and the carbamate ester having the structure represented by formula (a-2) is a carbamate ester represented by formula (A-2). [ka] In the above formula, R 12 Each of these independently represents a hydrogen atom or a monovalent hydrocarbon group that is unsubstituted or substituted; R 22 R represents an unsubstituted or substituted divalent hydrocarbon group; 32 Each of these independently represents an unsubstituted or substituted monovalent hydrocarbon group; R 42 Each of these is independently an unsubstituted or substituted hydrocarbon ligand, -OR 32 Q' represents an unsubstituted or substituted alkoxy ligand, amide ligand, or halide ligand, distinct from the above; M' represents a metal atom or metalloid atom; n' represents the oxidation state of M', where (n'-m') is an integer from 1 to 6; m' represents an integer greater than or equal to 0 and less than or equal to (n'-1); Q' represents a (2 / q') valent countercation, where q' is either 1 or 2.

[0028] <1-5-1. Carbamic acid ester represented by formula (A-2)> In formula (A-2), R 12 Each of these independently represents a hydrogen atom or a monovalent hydrocarbon group that is unsubstituted or substituted, and R 22 R represents an unsubstituted or substituted divalent hydrocarbon group, 32 Each of these independently represents a monovalent hydrocarbon group that is either unsubstituted or substituted. R 12 For details, see the above R 1 The explanation applies. R 22 For details, see the above R 20 The explanation applies. R 32 For details, see the above R 3 The explanation applies.

[0029] <1-5-2. Carbamate represented by formula (B-2)> In formula (B-2), R 12 Each of these independently represents a hydrogen atom or a monovalent hydrocarbon group that is unsubstituted or substituted, and R 22 Q' represents an unsubstituted or substituted divalent hydrocarbon group, and Q' represents a countercation. R in equation (B-2) 12 R is in equation (A-2) 12 This corresponds to R in equation (B-2). 22 R is in equation (A-2) 22 This corresponds to R. 12 For details, see the above R 1 The explanation applies. Also, R 22 For details, see the above R 2 The explanation applies.

[0030] (Q') Q' represents the countercation in the carbamate salt and is not particularly limited as long as it is a monovalent or divalent cation, but examples include ammonium cation, amidinium cation, guanidinium cation, phosphonium cation, phosphazenium cation, carbocation, sulfonium cation, iodonium cation, alkali metal cation, and alkaline earth metal cation. Specific examples of these cations are those mentioned above in section (Q). Preferably, from the viewpoint of ease of synthesis, ammonium cations, amidinium cations, guanidinium cations, phosphonium cations, phosphazenium cations, carbocations, alkali metal cations, and alkaline earth metal cations are used, and more preferably ammonium cations, amidinium cations, guanidinium cations, and phosphazenium cations. Among these, tert-butylimino-tri(pyrrolidino)phosphoranium cations and 1,8-diazabicyclo[5.4.0]undecé-7-enium cations are used. (q') q' is either 1 or 2. (2 / q') indicates the number of countercations Q; that is, if Q is a monovalent cation, q' is 2, and if Q is a divalent cation, q' is 1.

[0031] Specific examples of carbamates represented by formula (B-2) include compounds represented by the following formulas and amidinium salts, guanidinium salts, phosphonium salts, phosphazenium salts, carbocation salts, alkali metal salts, or alkaline earth metal salts, where the counter cation of these compounds is an amidinium cation other than the 1,8-diazabicyclo[5.4.0]undecé-7-enium cation, such as an amidinium cation, guanidinium cation, phosphonium cation, phosphazenium cation, carbocation salt, alkali metal salt, or alkaline earth metal salt. [ka] Specific examples of carbamates represented by formula (B-2) include, but are not limited to, compounds represented by the following formula and their countercations being phosphazenium cations other than amidinium cation, guanidinium cation, phosphonium cation, tert-butylimino-tri(pyrrolidino)phosphoranium cation, carbocations, alkali metal cations, or alkaline earth metal cations, such as amidinium salts, guanidinium salts, phosphonium salts, phosphazenium salts, carbocation salts, alkali metal salts, or alkaline earth metal salts. [ka]

[0032] <1-5-3. Metal alkoxides represented by formula (C-2)> In formula (C-2), R 32 R represents an unsubstituted or substituted monovalent hydrocarbon group; 42 Each of these is independently an unsubstituted or substituted hydrocarbon ligand, -OR 32 This represents an unsubstituted or substituted alkoxy ligand, amide ligand, or halide ligand, distinct from the above; M' represents a metal atom or metalloid atom, n' represents the oxidation state of M', (n'-m') is an integer from 1 to 6; and m' represents an integer between 0 and (n'-1). (M') M' represents a metallic atom or a metalloid atom. The types of metal atoms and metalloid atoms are not particularly limited, but examples include metal atoms or metalloid atoms selected from the group consisting of silicon, titanium, zirconium, germanium, indium, tin, tantalum, zinc, and tungsten. Among these, silicon and titanium are preferred due to their availability. (R 32 ) R in equation (C-2) 32 R is in equation (A-2) 32 This corresponds to R. 32 For details, see the above R 3 The explanation applies. (R42 ) R 42 Each of these is independently an unsubstituted or substituted hydrocarbon ligand, -OR 32 This represents an unsubstituted or substituted alkoxy ligand, amide ligand, or halide ligand, which is different from the above. Unsubstituted or substituted hydrocarbon ligands, -OR 32 Specific examples of alkoxy ligands, amide ligands, and halide ligands that are different from those with substitutions or substituents include, respectively, R 41 The ligands exemplified above are examples. When m is 2 to 5, there are multiple R 42 They may be the same or different, but in terms of ease of acquisition, all R 42 It is preferable that they are the same. (n') n' represents the oxidation number of M', and (n'-m') is an integer between 1 and 6. (m') m' represents an integer between 0 and (n'-1), i.e., an integer between 0 and 5. Specific examples of metal alkoxides represented by formula (C-2) include the metal alkoxides exemplified in formula (C-1). Preferably, from the viewpoint of availability, it is at least one selected from the group consisting of titanium compounds and silicon compounds, and 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. More preferably are titanium tetramethoxide, titanium tetra-iso-propoxide, titanium tetra-n-butoxide, titanium tetra-t-butoxide, and tetramethoxysilane.

[0033] <1-6. Reaction Process> The reaction process may involve, for example, placing the raw materials, a carbamate salt and a metal alkoxide, into a sealed reaction vessel and reacting them at 200°C for 48 hours. Alternatively, for example, an amine may be placed in a sealed reaction vessel, carbon dioxide-containing gas may be blown in to produce a carbamate salt, and then titanium alkoxide, a metal alkoxide, may be added and the reaction may be carried out by heating. The reaction conditions will be described below.

[0034] (reaction solvent) The reaction step may or may not use a reaction solvent, but it is preferable to use one. The type of reaction solvent is not particularly limited, but ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; nitriles such as acetonitrile and propionitrile; and aprotic polar solvents such as dimethylacetamide, N,N-dimethylformamide, N,N'-dimethylpropyleneurea, 1,3-dimethyl-2-imidazolidinone, and N-methylpyrrolidone are preferred. Aprotic solvents are more preferred as the reaction solvent, ethers and aprotic polar solvents are even more preferred, and 1,4-dioxane, an aprotic ether, and N-methylpyrrolidone, an aprotic polar solvent, are particularly preferred. Using the above reaction solvents allows for more efficient production of carbamic acid esters. Furthermore, if there is a large difference between the boiling point of the solvent and the boiling point of the product, purification is easy, and the solvent can be reused. One type of reaction solvent may be used, or two or more types may be used. The amount of reaction solvent used is not particularly limited and can be appropriately selected depending on the target carbamic acid ester.

[0035] (catalyst) In one embodiment of the present invention, the reaction step 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 step in the presence of a catalyst. Examples of preferred catalysts include organic base carboxylates, alkali metal salts, zinc compounds, titanium(IV) compounds, and zirconium(IV) compounds. Examples of organic base carboxylates include acetate of 1,8-diazabicyclo[5.4.0]undeca-7-ene, acetate of 1,5-diazabicyclo[4.3.0]non-5-ene, and 1,1 Examples include nitrates of ,3,3-tetramethylguanidine. Examples of 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 zinc compounds include zinc halides such as zinc chloride and zinc bromide; zinc sulfate; zinc sulfonates such as zinc p-toluenesulfonate and zinc trifluoromethanesulfonate; zinc formate, zinc acetate, zinc propionate, zinc octanoate, zinc salicylate, zinc pivalate, zinc acrylate, p-chlorobenzoic acid, zinc phenolate, zinc chloroacetate, zinc acetylacetonate, zinc oxalate, and zinc carboxylate derivatives such as zinc trifluoroacetate and zinc(II)-1,10-phenanthroline complex. Examples of 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 zirconium(IV) compounds include zirconium(IV) chloride and zirconium(IV) oxychloride octahydrate. The catalyst may be prepared, for example, by generating it from two or more compounds. For instance, zinc acetate and 1,10-phenanthroline may be placed in a reaction vessel to form a zinc(II)-1,10-phenanthroline (phen) complex, which can then be used as the catalyst. In particular, 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 preferred. The amount of catalyst used in the reaction process (charging amount) is not particularly limited and should be appropriately selected depending on the target carbamate ester, but is preferably 10 mol% or more, 70 mol% or less, and more preferably 50 mol% or less relative to the amount of carbamate salt. In addition, one type of catalyst may be used, or two or more types may be used.

[0036] (Reaction temperature) The reaction temperature (sometimes referred to as "reaction temperature") is not particularly limited and can be adjusted as appropriate by the reaction scale, etc. It is usually 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 can be adjusted as appropriate depending on the reaction temperature, reaction scale, etc. Typically, it is 30 minutes or more, preferably 1 hour or more, and typically 48 hours or less, preferably 24 hours or less, and more preferably 20 hours or less.

[0038] (Reaction atmosphere) The atmosphere during the reaction process may be an air atmosphere or an inert gas atmosphere such as nitrogen or argon. The reaction process may be carried out under either pressurized or reduced pressure conditions, usually at 0.01 atm or higher, preferably 0.05 atm or higher, more preferably 0.1 atm or higher, and usually at 10 atm or lower, preferably 5 atm or lower, more preferably 2 atm or lower.

[0039] (Reaction vessel) The reaction vessel is not particularly limited and should be appropriately selected depending on whether it is 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 (closed reaction vessel), and more preferably a sealed reaction vessel that is equal in volume to the mixture of the carbamate salt, metal alkoxide, and, if necessary, the reaction solvent and catalyst.

[0040] (Other processes) In the method for producing carbamic acid esters according to this embodiment, in addition to the reaction steps described above, optional steps may be included. Optional steps include the carbamic acid salt production step described in the (Carbamic Acid) section, the regeneration of metal alkoxides with alcohol, and the purification step to increase the purity of the carbamic acid ester. In the purification step, purification methods commonly used in the field of organic synthesis, such as filtration, adsorption, column chromatography, and distillation, can be employed. [Examples]

[0041] The present invention will be described in more detail below with reference to examples, but modifications may be made as appropriate without departing from the spirit of the invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[0042] <Example 1-1> Benzylammonium N-benzylcarbamate (2.0 mmol), titanium tetramethoxide (2.0 mmol), and 1,4-dioxane (5 mL) were added to a 5 mL sealed reaction vessel and reacted at 200 °C for 48 hours. The yield of alkyl N-benzylcarbamate was 8%. Mesitylene (50 mg) was used as an internal standard for the yield. 1 This was determined by 1H NMR.

[0043] <Examples 1-2> Alkyl N-benzylcarbamate 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] <Examples 1-3> Alkyl N-benzylcarbamate esters were obtained in the same manner as in Examples 1-2, except that the reaction time was changed as shown in Table 1. The yields are shown in Table 1.

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

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

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

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

[0049] <Examples 1-8> Alkyl N-benzylcarbamate esters were 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.

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

[0051] <Examples 1-10> Alkyl N-benzylcarbamate esters were 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] <Example 1-11> Alkyl N-benzylcarbamate esters were obtained in the same manner as in Example 1-1, except that the amounts of metal alkoxide and solvent were changed as shown in Table 1. The yields are shown in Table 1.

[0053] <Examples 1-12> Except for changing the reaction temperature as shown in Table 1, the same procedure as in Example 1-11 was followed to prepare N-benzyl Alkyl carbamate esters were obtained. The yields are shown in Table 1.

[0054] [ka]

[0055] [Table 1]

[0056] Examples 1-1 to 1-12 demonstrate that alkyl carbamates can be produced using various titanium compounds as metal alkoxides.

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

[0058] <Example 2-2> 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> Except for changing the reaction time as shown in Table 2, the same procedure as in Example 2-2 was followed, and N-benzylka Alkyl rubamate ester was obtained. The yields are shown in Table 2.

[0060] <Example 2-4> Alkyl N-benzylcarbamate esters were obtained in the same manner as in Examples 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> Alkyl N-benzylcarbamate esters were obtained in the same manner as in Examples 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] [ka]

[0063] [Table 2]

[0064] It was shown that alkyl carbamates can be produced using silicon compounds as metal alkoxides.

[0065] <Example 3-1> Benzylamine (2.0 mmol), 1,8-diazabicyclo[5.4.0]undeca-7-ene (2.0 mmol), and 1,4-dioxane (4.5 mL) were added to a 5 mL sealed reaction vessel, and a CO2 / N2 mixed gas (v:v=15:85) was passed 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 N-benzylcarbamate methyl ester was 50%. The yield was measured using mesitylene (50 mg) as an internal standard. 1 This was determined by 1H NMR.

[0066] <Example 3-2> 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> The same procedure as in Example 3-1, except that the volume ratio of the CO2 / N2 mixed gas was changed as shown in Table 3. This yielded an alkyl N-benzylcarbamate. The yield is shown in 3.

[0068] [ka]

[0069] [Table 3]

[0070] <Example 4-1> A mixture containing dicarbamate, prepared by aerating 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) with a carbon dioxide / nitrogen mixture (1 atm, v:v=15:85) at a flow rate of 0.1 L / min for 20 minutes, 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 measured using mesitylene (50 mg) as an internal standard. 1 This was determined by 1H NMR.

[0071] [ka]

[0072] <Example 4-2> A mixture containing carbamate, prepared by aerating 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) with a carbon dioxide / nitrogen mixture (1 atm, v:v=15:85) at a flow rate of 0.1 L / min for 20 minutes, 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%. Mesitylene (50 mg) was used as an internal standard for the yield. 1 This was determined by 1H NMR.

[0073] [ka]

[0074] <Example 4-3> A mixture containing dicarbamate, prepared by aerating a mixture of hexamethylenediamine (116 mg, 1.0 mmol), tert-butylimino-tri(pyrrolidino)phosphorane (1250 mg, 4.0 mmol), and N-methylpyrrolidone (2.0 ml) with a carbon dioxide / nitrogen mixture (1 atm, v:v=15:85) at a flow rate of 0.1 L / min for 20 minutes, 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 measured using mesitylene (50 mg) as an internal standard. 1 This was determined by 1H NMR. [ka]

[0075] It was shown that alkyl carbamates can be produced by adding titanium alkoxide, a metal alkoxide, to a reaction system in which carbamates are generated using amines and carbon dioxide as raw materials, and then reacting the mixture. Furthermore, it was shown that alkyl carbamates can be produced using a low-concentration carbon dioxide gas, with carbon dioxide content of 15% in a carbon dioxide-containing gas mixture. [Industrial applicability]

[0076] According to the present invention, carbamate esters can be produced using carbamate salts and metal alkoxides as raw materials. Furthermore, the present invention also allows for the production of carbamate salts and carbamate esters using a low-concentration carbon dioxide mixed gas as a raw material, enabling the effective utilization of low-concentration carbon dioxide contained in exhaust gases, etc. Moreover, since the metal alkoxide used in the present invention can be recovered after the reaction and regenerated using alcohol, it is an environmentally friendly reaction in which essentially only low-concentration carbon dioxide, amines, and alcohols are consumed.

Claims

1. A carbamate salt production step comprising contacting an amino group-containing organic compound with a carbon dioxide-containing mixed gas in a solvent in the presence of a base to produce a carbamate salt represented by the following formula (B-1) or (B-2), and The reaction step includes a reaction step (excluding one carried out in the presence of a zinc compound) to produce a carbamic acid ester represented by the following formula (A-1) or (A-2) from the carbamate salt and alkoxysilane, A method for producing a carbamate ester, wherein the volume of carbon dioxide in the carbon dioxide-containing mixed gas in the carbamate salt production step is 0.01% or more. 【Chemistry 1】 【Chemistry 2】 (In the above formula, R １１ R represents a hydrogen atom or a monovalent hydrocarbon group that is unsubstituted or substituted; ２１ , R ３１ Each is independently an unsubstituted or substituted monovalent hydrocarbon. Represents the base; R １２ Each of these independently represents a hydrogen atom or a monovalent hydrocarbon group that is unsubstituted or substituted; R ２２ R represents an unsubstituted or substituted divalent hydrocarbon group; ３２ Each of these independently represents an unsubstituted or substituted monovalent hydrocarbon group; Q represents a q-valent countercation; q is 1 or 2; Q' represents a (2 / q')-valent countercation; q' is 1 or 2.

2. A method for producing a carbamic acid ester according to claim 1, wherein the carbamic acid salt is a carbamic acid salt represented by formula (B-1), the alkoxysilane is an alkoxysilane represented by the following formula (C-1), and the carbamic acid ester is a carbamic acid ester represented by formula (A-1). 【Transformation 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 carbamic acid ester according to claim 1 or 2, wherein Q is a cation selected from the group consisting of ammonium cation, amidinium cation, guanidinium cation, phosphonium cation, phosphazenium cation, carbocation, alkali metal cation, and alkaline earth metal cation.

4. A method for producing a carbamic acid ester according to claim 1, wherein the carbamic acid salt is a carbamic acid salt represented by the formula (B-2), the alkoxysilane is an alkoxysilane represented by the following formula (C-2), and the carbamic acid ester is a carbamic acid ester represented by the formula (A-2). 【Chemistry 4】 (In the above formula, R ３２ Each of these independently represents an unsubstituted or substituted monovalent hydrocarbon group; R ４２ Each is independently an unsubstituted or substituted hydrocarbon ligand, -OR ３２ This represents an unsubstituted or substituted alkoxy ligand, amide ligand, or halide ligand, distinct from the above; M' represents silicon, n' is 4, (n'-m') is an integer from 1 to 4, and m' represents an integer from 0 to 3.

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

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

7. A method for producing a carbamate ester according to any one of claims 1 to 6, wherein the carbamate salt production step and the reaction step are carried out in a continuous process.

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