JP7723381B2 - Zinc carbamate complex, method for producing zinc carbamate complex, and method for producing carbamate compound using the zinc carbamate complex as a catalyst - Google Patents

Description

The present invention relates to a zinc carbamate complex, a method for producing the zinc carbamate complex, and a method for producing a carbamate compound using the zinc carbamate complex as a catalyst.

Carbamate compounds are useful compounds as polyurethane raw materials and the like.
The present inventors have developed a technology for synthesizing carbamate compounds from inexpensive, abundant, and low-toxic carbon dioxide and tetraalkyl silicate (TROS) (see Non-Patent Document 1).
Non-Patent Document 2 reports an example in which an aggregate of zinc carbamate complexes consisting of the building blocks shown below was synthesized by adsorbing carbon dioxide onto a metal organic framework (MOF) containing zinc amide.

ChemSusChem 2017, 10, 1501-1508. J. Am. Chem. Soc. 2017, 139, 10526-10538.

The objective of the present invention is to provide a novel zinc carbamate complex, a method for producing a zinc carbamate complex, and a method for producing a carbamate compound.

As a result of extensive investigations aimed at solving the above problems, the present inventors have found that a novel zinc carbamate complex can be produced by reacting an amine compound, a zinc compound, an L-ligand, and carbon dioxide, and have thus completed the present invention.
The present invention provides the following specific embodiments.

[1]
A zinc carbamate complex represented by the general formula (1) or (1'):
In formula (1), each R ¹ is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group; R ² is a substituted or unsubstituted m-valent hydrocarbon group; m is 1 or 2; X is an anionic ligand; L is an L-ligand, and the L-ligand is a monodentate ligand, bidentate ligand, tridentate ligand, tetradentate ligand, or hexadentate ligand; n is the number of L-ligands and is an integer of 1 to 4, and when n is 2 or more, multiple Ls may be the same or different.
In formula (1'), R ¹ , X, L, and n are defined as R ¹ , X, L, and n in formula (1), respectively; R ²² is a substituted or unsubstituted divalent hydrocarbon group; and R ³ is a substituted or unsubstituted monovalent hydrocarbon group.
[2]
The zinc carbamate complex according to [1], wherein in the formula (1) or (1'), R ¹ is a hydrogen atom.
[3]
The zinc carbamate complex according to [1] or [2], wherein in the formula (1) or (1'), X is a sulfonate ligand or a carboxylate ligand.
[4]
The zinc carbamate complex according to any one of [1] to [3], wherein in the formula (1) or (1'), L is an amine ligand or a phosphine ligand.
[5]
The zinc carbamate complex according to [4], wherein in the formula (1) or (1'), L is a bidentate amine ligand.
[6]
The zinc carbamate complex according to [5], wherein in the formula (1) or (1'), the bidentate amine ligand is 1,10-phenanthroline or 2,2'-bipyridyl.
[7]
A method for producing a zinc carbamate complex represented by general formula (1) or (1'), comprising a reaction step of reacting an amine compound represented by general formula (A) or (A'), a zinc compound represented by general formula (B), an L-ligand, and carbon dioxide.
In formula (A), each R ¹ is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group; R ² is a substituted or unsubstituted m-valent hydrocarbon group; and m is 1 or 2.
In formula (B), X and Y are anionic ligands.
In formula (1), R ¹ , R ² and m are respectively defined as R ¹ , R ² and m in formula (A); X is defined as X in formula (B); L is an L-ligand, and the L-ligand is a monodentate ligand, a bidentate ligand, a tridentate ligand, a tetradentate ligand, or a hexadentate ligand; n is the number of the L-ligands and is an integer of 1 to 4, and when n is 2 or more, multiple Ls may be the same or different.
In formula (A'), R ¹ has the same meaning as R ¹ in formula (A); R ²² is a substituted or unsubstituted divalent hydrocarbon group; and R ³ is a substituted or unsubstituted monovalent hydrocarbon group.
In formula (1'), R ¹ , R ²² and R ³ have the same meanings as R ¹ , R ²² and R ³ in formula (A'), respectively; X has the same meaning as X in formula (B); L and n have the same meanings as L and n in formula (1), respectively.
[8]
The method for producing a zinc carbamate complex according to [7], wherein the amine compound represented by general formula (A) or (A') is a monoamine compound selected from aniline or an aniline derivative, 4-aminopyridine, 1-aminohexane, and cyclohexylamine; or a diamine compound selected from 4,4'-methylenedianiline, 2,4-tolylenediamine, 1,6-hexyldiamine, and derivatives thereof, or a compound in which one amino group of these diamine compounds is converted to a group having a urethane structure represented by formula (C).
(In the formula, ^R3 has the same meaning as ^R3 in formula (A'), and * indicates a binding site.)
[9]
The method for producing a zinc carbamate complex according to [7] or [8], wherein the zinc compound represented by the general formula (B) is ZnCl ₂ , ZnBr ₂ , Zn(OTf) ₂ or Zn(OAc) ₂ .
[10]
In the formula (1) or (1′), L is an amine ligand or a phosphine ligand.
[7] to [9]. A method for producing a zinc carbamate complex according to any one of [7] to [9].
[11]
[10] The method for producing a zinc carbamate complex according to [10], wherein in the formula (1) or (1'), L is a bidentate amine ligand.
[12]
[11] The method for producing a zinc carbamate complex according to [11], wherein the bidentate amine ligand in the formula (1) or (1') is 1,10-phenanthroline or 2,2'-bipyridyl.
[13]
A method for producing a carbamate compound, comprising a carbamate production step of reacting an amine compound (D), an alkoxysilane (E), and carbon dioxide using as a catalyst the zinc carbamate complex according to any one of [1] to [6] or the zinc carbamate complex obtained by the method for producing a zinc carbamate complex according to any one of [7] to [12] to produce a carbamate compound (F).
[14]
[14] The method for producing a carbamate according to [13], wherein the alkoxysilane (E) is a tetraalkoxysilane.

The present invention provides a zinc carbamate complex, a method for producing a zinc carbamate complex, and a method for producing a carbamate compound using the zinc carbamate complex as a catalyst.

Specific examples will be used to explain the details of the present invention, but the present invention is not limited to the following and can be modified as appropriate without departing from the spirit of the invention.

1. Zinc Carbamate Complex A zinc carbamate complex according to one embodiment of the present invention is a zinc carbamate complex represented by general formula (1) or (1′).
In formula (1), each R ¹ is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group; R ² is a substituted or unsubstituted m-valent hydrocarbon group; m is 1 or 2; X is an anionic ligand; L is an L-ligand, and the L-ligand is a monodentate ligand, bidentate ligand, tridentate ligand, tetradentate ligand, or hexadentate ligand; n is the number of L-ligands and is an integer of 1 to 4, and when n is 2 or more, multiple Ls may be the same or different.
In formula (1'), R ¹ , X, L, and n are defined as R ¹ , X, L, and n in formula (1), respectively; R ²² is a substituted or unsubstituted divalent hydrocarbon group; and R ³ is a substituted or unsubstituted monovalent hydrocarbon group.
The present inventors have discovered that a novel zinc carbamate complex can be produced by reacting an amine compound, a zinc compound, an L-ligand, and carbon dioxide. The present inventors had envisioned a zinc carbamate complex as an intermediate in the catalytic reaction in the carbamate synthesis reaction reported in Non-Patent Document 1, but this is the first time that a zinc carbamate complex itself has been synthesized and isolated. The present inventors further discovered that a zinc carbamate complex represented by general formula (1) or (1') acts as a catalyst for carbamate compound synthesis, leading to the completion of the present invention.
The only report on the synthesis of similar zinc carbamate complexes is in Non-Patent Document 2, which only reports an example of the synthesis of zinc carbamate complexes using a special diamine, and does not mention the use of any of the synthesized zinc carbamate complexes as catalysts for the synthesis of carbamate compounds, etc.
The zinc carbamate complexes represented by the general formula (1) or (1') will be described in detail below.

(R ¹ )
In the formula (1) or (1'), each ^R1 is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group. In this specification, the term "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.
The number of carbon atoms in R ¹ 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.
The unsubstituted hydrocarbon group represented by R ¹ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.
Examples of the aliphatic hydrocarbon group include 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, an n-pentyl group, an isopentyl 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 ethyl group, an isopropyl ... Examples include alkyl groups such as a decyl group, an n-nonadecyl group, and an n-docosyl group; cycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group; alkenyl groups such as a vinyl group, an allyl group, a 1-propenyl group, an isopropenyl group, a 1-butenyl group, a 2-butenyl group, a 2-methylallyl group, a 1-heptenyl group, a 1-hexenyl group, a 1-heptenyl group, a 1-octenyl group, and a 2-methyl-1-propenyl group; and alkynyl groups such as a propargyl group.
Examples of aromatic hydrocarbon groups include phenyl, 1-naphthyl, 2-naphthyl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, 9-phenanthryl, 1-anthryl, 2-anthryl, 9-anthryl, 1-pyrenyl, 2-pyrenyl, 4-pyrenyl, 1-triphenylenyl, and 2-triphenylenyl groups.
When the hydrocarbon group represented by ^R1 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, and a tert-butyl group; a cycloalkyl group having 3 to 4 carbon atoms such as a cyclopropyl group and a cyclobutyl group; an aromatic hydrocarbon group having 6 to 10 carbon atoms such as a phenyl group, a 1-naphthyl group, and a 2-naphthyl group; a halogeno group such as a fluoro group, a chloro group, a bromo group, and an iodo group; Examples of the heterocyclic group include oxygen-containing functional groups such as an alkoxy group, a carboxy group, a carbonyl group, and a hydroxyl group; nitrogen-containing functional groups such as a cyano group; sulfur-containing functional groups such as an alkylthio group; functional groups containing an oxygen atom and a nitrogen atom such as an amide group, an imide group, a urea group, a group containing a urethane structure, a group containing an isocyanuric structure, a nitro group, a nitroso group, a cyanate group, an isocyanate group, and a morpholino group; and heterocyclic groups such as oxygen-containing heterocyclic groups such as a furanyl group, sulfur-containing heterocyclic groups such as a thienyl group, and nitrogen-containing heterocyclic groups such as a pyrrolyl group and a pyridyl group.
When the hydrocarbon group represented by ^R1 has a substituent, preferred examples of ^R1 include alkyl-substituted phenyl groups such as a 2-methylphenyl group, a 3-methylphenyl group, and a 4-methylphenyl group; alkoxy-substituted phenyl groups such as a 2-methoxyphenyl group, a 3-methoxyphenyl group, and a 4-methoxyphenyl group; halogen-substituted phenyl groups such as a 2-chlorophenyl group, a 3-chlorophenyl group, a 4-chlorophenyl group, a 2-bromophenyl group, a 3-bromophenyl group, and a 4-bromophenyl group; nitro-substituted phenyl groups such as a 4-nitrophenyl group and a 2-nitrophenyl group; aralkyl groups such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, and a 2-naphthylmethyl group; cycloalkylalkyl groups such as a cyclohexylmethyl group; hydrocarbon groups having an oxygen-containing heterocycle such as a furfuryl group; hydrocarbon groups having a sulfur-containing heterocycle such as a thienylmethyl group; and hydrocarbon groups having a nitrogen-containing heterocycle such as a pyridylmethyl group.
When the hydrocarbon group is a branched alkyl group, the number of carbon atoms in the main chain is the number of carbon atoms in the hydrocarbon group. When the hydrocarbon group has a substituent, the number of carbon atoms refers to the total number of carbon atoms in the substituent and the number of carbon atoms in the hydrocarbon group.
In terms of the usefulness of the zinc carbamate complex, R ¹ is preferably a hydrogen atom or a substituted or unsubstituted hydrocarbon group having 1 to 24 carbon atoms, and particularly preferably a hydrogen atom.
When m=2, the two R ^1s may be the same or different, but are preferably the same.

( ^R2 , m)
In the formula (1) or (1′), R ² is a substituted or unsubstituted m-valent hydrocarbon group, and m is 1 or 2.
The number of carbon atoms in ^R2 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.
When m=1, examples of the unsubstituted hydrocarbon group represented by ^R2 include the monovalent hydrocarbon groups exemplified for ^R1 .
When m = 2, examples of the unsubstituted hydrocarbon group represented by ^R2 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. Specific examples thereof include chain hydrocarbon groups such as methylene, ethylene, tetramethylethylene, n-propylene (trimethylene), 1-methylpropylene, 1,1-dimethylpropylene, 2-methylpropylene, 1,2-dimethylpropylene, 2,2-dimethylpropylene, 1,1,2-trimethylpropylene, 1,1,3-trimethylpropylene, n-butylene (tetramethylene), 2-methyl-1,4-butylene, 3-methyl-1,4-butylene, 2,2-dimethyl-1,4-butylene, 2,3-dimethyl-1,4-butylene, 2,2,3-trimethyl-1,4-butylene, n-pentylene (pentamethylene), and n-hexanylene (hexamethylene) groups; alicyclic hydrocarbon groups such as 1,4-cyclohexylene; Examples of such groups include a 1,4-phenylene group, a 1,2-phenylene group, and a 1,3-phenylene group in which two hydrogen atoms have been removed from a benzene ring; aromatic hydrocarbon groups such as a dimethylphenylene group (xylyl group) in which two hydrogen atoms have been removed from the benzene ring of xylene, a methylphenylene group (tolylene group) in which two hydrogen atoms have been removed from the benzene ring of toluene, and a naphthalene group in which two hydrogen atoms have been removed 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 in which one hydrogen atom has been removed from each of the two benzene rings of biphenyl, and a group in which one hydrogen atom has been removed from each of the two benzene rings of diphenylmethane; and divalent groups in which two hydrogen atoms have been removed from a polycyclic aromatic hydrocarbon such as a fluorene ring.
When the hydrocarbon group represented by ^R2 has a substituent, examples of the substituent include those exemplified as the substituents of the hydrocarbon group represented by ^R1 .
From the viewpoint of ease of availability of raw materials, ^R2 is preferably a substituted or unsubstituted monovalent or divalent hydrocarbon group having 1 to 24 carbon atoms, and more preferably a substituted or unsubstituted alkyl group having 1 to 24 carbon atoms; a substituted or unsubstituted cycloalkyl group having 3 to 24 carbon atoms; a substituted or unsubstituted alkylene group having 1 to 24 carbon atoms; a substituted or unsubstituted monovalent or divalent aromatic hydrocarbon group having 6 to 24 carbon atoms; a substituted or unsubstituted aralkyl group having 7 to 24 carbon atoms; or a heterocyclic group such as a substituted or unsubstituted nitrogen-containing heterocycle. a cyclic group; a substituted or unsubstituted phenylene group; a divalent group having 7 to 24 carbon atoms and consisting of an aliphatic hydrocarbon group and an aromatic hydrocarbon group; and more preferably a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted phenylene group, a divalent group having 7 to 24 carbon atoms consisting of an aliphatic hydrocarbon group and an aromatic hydrocarbon group, or a substituted or unsubstituted pyridyl group. As the substituent, an alkyl group, an alkenyl group, an alkoxy group, a cyano group, a halogeno group, or a nitro group is preferred in terms of the usefulness of the resulting complex. As the substituted phenyl group, preferred are alkyl-substituted phenyl groups such as a 2-methylphenyl group, a 4-methylphenyl group, and a 2,4-dimethylphenyl group; alkoxy-substituted phenyl groups such as a 4-methoxyphenyl group and a 2-methoxyphenyl group; halogen-substituted phenyl groups such as a 2-chlorophenyl group, a 4-chlorophenyl group, and a 2,4-dichlorophenyl group; and nitro-substituted phenyl groups such as a 4-nitrophenyl group and a 2-nitrophenyl group.

( ^R22 )
In the formula (1'), ^R22 is a substituted or unsubstituted divalent hydrocarbon group. Specific examples of ^R22 include the divalent hydrocarbon groups exemplified for ^R2 . Preferred embodiments are the same as those of ^R2 when m = 2.

(R ³ )
In the formula (1'), ^R3 is a substituted or unsubstituted hydrocarbon group.
Specific examples of ^R3 include the monovalent hydrocarbon groups exemplified for ^R1 . ^R3 is preferably a substituted or unsubstituted aliphatic hydrocarbon group, more preferably a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 24 carbon atoms, and even more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.

(X)
In the formula (1), X is an anionic ligand.
The anionic ligand is not particularly limited, but preferably includes a halogen ligand, a sulfonate ligand, and a carboxylate ligand, more preferably a sulfonate ligand or a carboxylate ligand, further preferably a triflate ligand or an acetate ligand, and particularly preferably an acetate ligand.
Examples of halogen ligands include fluoride ligands, chloride ligands, bromide ligands, and iodine ligands.
Examples of sulfonate ligands include ligands represented by SO ₃ (R ^a ) ^— (R ^a represents a halogeno group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms). From the viewpoint of availability, preferred are fluoroalkylsulfonate ligands such as triflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate; arylsulfonate ligands such as tosylate, benzenesulfonate, 4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate; or alkylsulfonate ligands such as mesylate and butanesulfonate, with triflate ligands being more preferred.
Examples of carboxylate ligands include ligands represented by R ^b CO ₂ ^— (R ^b is a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms). Among these, from the viewpoint of ease of availability, formate ligands (OCOH), acetate ligands (OCOMe), propionate ligands (OCOEt), butyrate ligands (OCOPr), etc. are preferred, with acetate ligands being more preferred.

(L, n)
In the formula (1), L is an L-type ligand, and the L-type ligand is a monodentate ligand, a bidentate ligand, a tridentate ligand, a tetradentate ligand, or a hexadentate ligand; n is the number of the L-type ligands and is an integer of 1 to 4; when n is 2 or more, multiple Ls may be the same or different.
The L-type ligand is not particularly limited, but is preferably an amine ligand or a phosphine ligand, and is preferably a bidentate amine ligand from the viewpoint of increasing the catalytic activity and improving the reaction yield.
Examples of the amine ligand include monodentate amine ligands such as aniline, toluidine, anisidine, and N,N-dimethylformamide (DMF); bidentate amine ligands such as tetramethylethylenediamine, 1,10-phenanthroline, and 2,2′-bipyridyl; tridentate amine ligands such as N,N,N′,N″,N″-pentamethyldiethylenetriamine; tris[2-(dimethylamino)ethyl]amine (Me ₆ tetradentate amine ligands such as N,N'-ethyl diacetate-N,N'-bis(2-pyridylmethyl)-1,2-ethylenediamine (debpn), ethylenediaminetetraacetic acid, and N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN); polyethyleneimine; and the like. Among these, 1,10-phenanthroline or 2,2'-bipyridyl is preferred.
Examples of the phosphine ligand include triphenylphosphine, trimethylphosphine, tri-n-butylphosphine, tri-tert-butylphosphine, tricyclohexylphosphine, triethoxyphosphine, tri(p-tolyl)phosphine, tri(o-tolyl)phosphine, methyldiphenylphosphine, tri(2-furyl)phosphine, tricyclohexylphosphine, dicyclohexylphenylphosphine, tri-tert-butylphosphonium tetrafluoroborate, tri-tert-butylphosphonium tetraphenylborate, and tri(t-butyl)phosphine (P(t-Bu) ₃ ).CF ₃ SO ₃ H, 2-(di-t-butylphosphino)biphenyl (JohnPhos), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (Xphos), 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP), 1,1'-bis(diphenylphosphino)ferrocene (DPPF), 1,1'-bis(di-t-butylphosphino)ferrocene (DtBPF), N,N-dimethyl-1-[2-(diphenylphosphino)ferrocenyl]ethylamine, Examples of suitable bis(diphenylphosphino)phenyl compounds include 1-[2-(diphenylphosphino)ferrocenyl]ethyl methyl ether, 4,5-bis(diphenylphosphino)-9,9 dimethylxanthene (Xantphos), 4,6-bis(diphenylphosphino)phenoxazine (NIXantphos), bis[2-(diphenylphosphino)phenyl]ether (DPEphos), 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, and 1,4-bis(diphenylphosphino)butane.
n is the number of the L-type ligands and is an integer of 1 to 4, preferably 1 or 2.

Specific examples of the zinc carbamate complex represented by the general formula (1) or (1') include the following compounds.

The method for producing the zinc carbamate complex represented by the above general formula (1) or (1') is not particularly limited, but it is preferably derived from an amine compound R ² (NHR ¹ ) _m or R ² (N(CO ₂ R ³ )R ¹ ) (NHR ¹ ), a zinc compound ZnXY, and an L-type ligand L, and can be suitably produced by the method for producing a zinc carbamate complex described below.

2. Method for Producing Zinc Carbamate Complex A method for producing a zinc carbamate complex according to one embodiment of the present invention is a method for producing a zinc carbamate complex represented by general formula (1) or (1'), which includes a reaction step of reacting an amine compound represented by general formula (A) or (A'), a zinc compound represented by general formula (B), an L-ligand, and carbon dioxide.
In formula (A), each R ¹ is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group; R ² is a substituted or unsubstituted m-valent hydrocarbon group; and m is 1 or 2.
In formula (B), X and Y are anionic ligands.
In formula (1), R ¹ , R ² and m are respectively defined as R ¹ , R ² and m in formula (A); X is defined as X in formula (B); L is an L-ligand, and the L-ligand is a monodentate ligand, a bidentate ligand, a tridentate ligand, a tetradentate ligand, or a hexadentate ligand; n is the number of the L-ligands and is an integer of 1 to 4, and when n is 2 or more, multiple Ls may be the same or different.
In formula (A'), R ¹ has the same meaning as R ¹ in formula (A); R ²² is a substituted or unsubstituted divalent hydrocarbon group; and R ³ is a substituted or unsubstituted monovalent hydrocarbon group.
In formula (1'), R ¹ , R ²² and R ³ have the same meanings as R ¹ , R ²² and R ³ in formula (A'), respectively; X has the same meaning as X in formula (B); L and n have the same meanings as L and n in formula (1), respectively.

(Amine compounds represented by general formula (A) or (A'))
R ² (NHR ¹ ) _m (A)
In formula (A), each R ¹ is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group; R ² is a substituted or unsubstituted m-valent hydrocarbon group; and m is 1 or 2.
R ² (N(CO ₂ R ³ ) R ¹ ) (NHR ¹ ) (A')
In formula (A'), R ¹ has the same meaning as R ¹ in formula (A); R ²² is a substituted or unsubstituted divalent hydrocarbon group; and R ³ is a substituted or unsubstituted monovalent hydrocarbon group.
For details of R ¹ in general formula (A) or (A'), the explanation of R ¹ in "Zinc carbamate complex represented by general formula (1)" in the above section "1. Zinc carbamate complex" applies.
For details of ^R2 in general formula (A), the explanation of ^R2 in "Zinc carbamate complex represented by general formula (1)" in the above section "1. Zinc carbamate complex" applies.
For details of R ²² and R ³ in general formula (A′), the explanation of R ²² and R ³ in “Zinc carbamate complex represented by general formula (1)” in the above section “1. Zinc carbamate complex” applies.
The amine compound represented by the general formula (A) may be a monoamine compound or a diamine compound. The amine compound represented by the general formula (A') is a compound in which one of the amino groups of a diamine compound is converted to a group having a urethane structure represented by the formula (C).

(In the formula, ^R3 has the same meaning as ^R3 in formula (A'), and * indicates a binding site.)
In formula (C), ^R3 is a substituted or unsubstituted monovalent hydrocarbon group, and specific examples of ^R3 include the monovalent hydrocarbon groups exemplified for ^R1 . ^R3 is preferably a substituted or unsubstituted aliphatic hydrocarbon group, more preferably a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 24 carbon atoms, and even more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.

Preferred examples of the monoamine compound include aniline or an aniline derivative, 4-aminopyridine, 1-aminohexane, and cyclohexylamine. Preferred examples of the aniline derivative include o-anisidine, m-anisidine, p-anisidine, 4-vinylaniline, 4-nitroaniline, 4-bromoaniline, 4-fluoroaniline, 4-cyanoaniline, 4-cyanoaniline, p-toluidine, 4-chloroaniline, 4-bromoaniline, and 4-fluoroaniline.
Preferred examples of the diamine compound include 4,4'-methylenedianiline, 2,4-tolylenediamine, 1,6-hexyldiamine, and derivatives thereof. Also preferred are compounds encompassed by general formula (A'), in which one amino group of these diamine compounds or diamine compound derivatives is converted to a group having a urethane structure represented by formula (C) above.
The amount of the amine compound used (charge amount) is not particularly limited, but is usually 1 equivalent or more, preferably 1.5 equivalents or more, more preferably 2.5 equivalents or more, and even more preferably 3 equivalents or more, relative to 1 equivalent of the zinc compound, and is usually 20 equivalents or less, preferably 15 equivalents or less, and more preferably 10 equivalents or less.

(Zinc compound represented by general formula (B))
ZnXY (B)
In formula (B), X and Y are anionic ligands that can serve as counter anions for zinc ions (Zn ²⁺ ), and may be the same or different.
For details of X and Y in formula (B), the description of X in "Zinc carbamate complex represented by general formula (1)" in the above section "1. Zinc carbamate complex" applies.
From the viewpoint of easy availability of zinc compounds, it is preferred that X and Y are the same.
Preferred examples of the zinc compound represented by the general formula (B) include ZnCl ₂ , ZnBr ₂ , Zn(OTf) ₂ and Zn(OAc) ₂ .

(L-type ligand)
The L-type ligand represented by L is a monodentate ligand, bidentate ligand, tridentate ligand, tetradentate ligand, or hexadentate ligand. Specific examples of the L-type ligand include the ligands exemplified in the description of the L-type ligand in "Zinc carbamate complex represented by general formula (1)" in the above section "1. Zinc carbamate complex," and preferred embodiments are also the same.
The amount of the L-ligand used (charge amount) is not particularly limited, but is usually 0.5 equivalents or more, preferably 1.0 equivalents or more, more preferably 2.0 equivalents or more, and even more preferably 3.0 equivalents or more, relative to 1 equivalent of the zinc compound, and is usually 20 equivalents or less, preferably 10 equivalents or less, and more preferably 5 equivalents or less.

(carbon dioxide)
In the reaction step, carbon dioxide (gas) is used as a raw material for the zinc carbamate complex. The carbon dioxide used in the reaction step may be not only that prepared as an industrial gas, but also that separated and recovered from exhaust gases from factories, power plants, etc. The reaction system may contain gases other than carbon dioxide, such as inert gases such as _N2 and Ar, to the extent that the effects of the present invention are not significantly impaired.

(solvent)
The reaction step may or may not involve the use of a solvent, but it is preferable to use a reaction solvent. The use of a reaction solvent is thought to increase the amount of carbon dioxide dissolved in the reaction mixture, thereby increasing the carbon dioxide concentration in the reaction system, facilitating the reaction and improving the yield of the zinc carbamate complex.
The type of reaction solvent is not particularly limited, and examples thereof include alcohols such as ethanol, propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, t-butanol, allyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and glycerin; aliphatic hydrocarbons such as butane, hexane, octane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; and heterocyclic aromatic hydrocarbons such as pyridine. Examples of suitable solvents include aromatic compounds; aprotic polar solvents such as ethyl acetate, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, and N-methylpyrrolidone (NMP); ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran, and dioxane; nitriles such as acetonitrile, propionitrile, butyronitrile, benzonitrile, and 2-cyanopyridine; and ketones such as acetone and isopropyl ketone. Among these, acetonitrile is preferred. One type of solvent may be used, or two or more types may be used.
The amount of the solvent used is not particularly limited, but is usually 1 equivalent or more, preferably 1.5 equivalents or more, more preferably 2.5 equivalents or more, and even more preferably 4 equivalents or more, relative to 1 equivalent of the zinc compound, and is usually 20 equivalents or less, preferably 15 equivalents or less, and more preferably 10 equivalents or less.

(Filling pressure)
The charging pressure of the carbon dioxide gas is not particularly limited, but is usually 0.1 MPa or more, preferably 1.0 MPa or more, more preferably 1.0 MPa or more, and even more preferably 3.0 MPa or more, and is usually 10.0 MPa or less, preferably 5.0 MPa or less. When the charging pressure is within this range, the zinc carbamate complex can be produced efficiently. In this specification, the "charging pressure" refers to the pressure of carbon dioxide (25°C) in the reactor at the start of the reaction.

(Reaction temperature)
The reaction temperature is not particularly limited, but a higher temperature tends to result in a higher yield of the zinc carbamate complex, and is usually 100° C. or higher, preferably 120° C. or higher, more preferably 150° C. or higher, and usually 250° C. or lower, preferably 230° C. or lower, more preferably 200° C. or lower. When the reaction temperature is within this range, the zinc carbamate complex can be produced efficiently.

(Reaction time)
The reaction time is not particularly limited and may be adjusted appropriately depending on the reaction temperature, amount of catalyst, reaction scale, etc. It is usually 30 minutes or more, preferably 1 hour or more, more preferably 2 hours or more, and usually 120 hours or less, preferably 100 hours or less, more preferably 80 hours or less. In this specification, the "reaction time" refers to the time during which the temperature in the reactor is maintained at a predetermined reaction temperature after it has reached the predetermined reaction temperature.

(Reaction vessel)
The reaction vessel is not particularly limited as long as it is made of a material that is stable to the zinc carbamate complex, and can be appropriately selected depending on whether the process is a continuous process or a batch process. In one embodiment of the present invention, the process may be a continuous process or a batch process. In the case of a batch process, the reaction vessel is preferably a sealed reaction vessel (sealed reaction vessel), more preferably a sealed pressure-resistant vessel having a volume 10 to 100 times the volume of the mixture of the amine compound, the zinc compound, the ligand, and optionally a solvent, and more preferably a stainless steel autoclave.

(Operation procedure)
First, the raw materials, an amine compound, a zinc compound, and a ligand, are added to a reaction vessel. This is preferably carried out under an inert gas atmosphere such as nitrogen or argon. After the amine compound, zinc compound, and ligand are added to the reaction vessel, the reactor is filled with the raw material, carbon dioxide, to create a carbon dioxide atmosphere. When a solvent is used, it can be added to the reaction vessel before introducing carbon dioxide into the reactor, or it can be added to the reactor simultaneously with the amine compound, etc. During the reaction, an inert gas such as nitrogen or argon may be contained in the reaction vessel to the extent that it does not significantly impair the effects of the present invention. Furthermore, it is preferable to stir the mixture during the reaction; for example, a magnetic stirrer can be used. After the reaction, the mixture is cooled, the remaining gas is discharged, and the reaction product is recovered.

(Other processes)
The method for producing a zinc carbamate complex according to this embodiment may include any optional step in addition to the reaction step. An example of such an optional step is a purification step for increasing the purity of the zinc carbamate complex. 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. Specifically, for example, the obtained solid may be filtered under a nitrogen atmosphere, washed with diethyl ether or the like, and vacuum dried.

3. Method for Producing Carbamate Compound Using Zinc Carbamate Complex as a Catalyst Another aspect of the present invention is a method for producing a carbamate compound, which includes a carbamate production step of reacting an amine compound (D), an alkoxysilane compound (E), and carbon dioxide using the above-mentioned zinc carbamate complex as a catalyst to produce a carbamate compound (F).
The amine compound (D) and alkoxysilane compound (E) used in this embodiment are not particularly limited, and are appropriately selected depending on the desired carbamate compound (F).

A preferred example of a method for producing a carbamate compound according to one embodiment of the present invention is a method including a carbamate production step in which an amine compound represented by formula (D1) or (D1′), an alkoxysilane compound represented by formula (E1), and carbon dioxide are reacted using the zinc carbamate complex as a catalyst to produce a carbamate compound represented by formula (F1) or (F1′).
In formula (D1), each R ⁴ is independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group; R ⁵ is a substituted or unsubstituted m′-valent hydrocarbon group; and m′ is 1 or 2.
In formula (E1), R ⁶ 's are each independently a substituted or unsubstituted hydrocarbon group; R ⁷ 's are each independently a substituted or unsubstituted hydrocarbon group; and n' is an integer of 1 to 4. However, when n' is 2 or greater, two R ^6's may be bonded to each other to form a ring. Furthermore, when n' is 3 or less, R ⁶ and R ⁷ may be bonded to form a ring.
In formula (F1), R ⁴ , R ⁵ and m′ have the same meanings as R ⁴ , R ⁵ and m′ in formula (D1), respectively; R ⁶ has the same meaning as R ⁶ in formula (E1).
In formula (D1'), R ⁴ has the same meaning as R ⁴ in formula (D1); R ⁵⁵ is a substituted or unsubstituted divalent hydrocarbon group; and R ⁸ is a substituted or unsubstituted monovalent hydrocarbon group.
In formula (F1'), R ⁴ , R ⁵⁵ and R ⁸ have the same meanings as R ⁴ , R ⁵⁵ and R ⁸ in formula (D1'), respectively; R ⁶ has the same meaning as R ⁶ in formula (E1).

(Amine Compound (D))
The "amine compound" used in this embodiment is not particularly limited as long as it is a compound having an amino group, and preferred examples thereof include amine compounds represented by formula (D1) or (D1').
R ⁵ (NHR ⁴ ) _m (D1)
In formula (D1), R ⁴ represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group; R ⁵ represents a substituted or unsubstituted m′-valent hydrocarbon group, where m′ is 1 or 2.
R ⁵⁵ (N(CO ₂ R ⁸ ) R ⁴ ) (NHR ⁴ ) (D1′)
In formula (D1'), R ⁴ has the same meaning as R ⁴ in formula (D1); R ⁵⁵ is a substituted or unsubstituted divalent hydrocarbon group; and R ⁸ is a substituted or unsubstituted monovalent hydrocarbon group.
For details of ^R4 in general formula (D1) or (D1'), the explanation of ^R1 in "Zinc carbamate complex represented by general formula (1)" in the above section "1. Zinc carbamate complex" applies.
For details of ^R5 in general formula (D1), the explanation of ^R2 in "Zinc carbamate complex represented by general formula (1)" in the above section "1. Zinc carbamate complex" applies.
For details of R ⁵⁵ and R ⁸ in general formula (D1′), the same explanation as for R ²² and R ³ in “Zinc carbamate complex represented by general formula (1)” in the above section “1. Zinc carbamate complex” applies.
The amine compound represented by the general formula (D1) may be a monoamine compound or a diamine compound. The amine compound represented by the general formula (D1′) is a diamine compound in which one of the amino groups is converted to a group having a urethane structure represented by the formula (C′).
(In the formula, ^R8 has the same meaning as ^R3 in formula (D1'), and * indicates a binding site.)
In formula (C'), ^R8 is a substituted or unsubstituted monovalent hydrocarbon group, and specific examples of ^R8 include the monovalent hydrocarbon groups exemplified for ^R1 . ^R8 is preferably a substituted or unsubstituted aliphatic hydrocarbon group, more preferably a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 24 carbon atoms, and even more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.
From the viewpoint of improving the yield of the carbamate compound and facilitating isolation and purification, it is preferable that R ⁴ and R ⁵ are the same groups as R ¹ and R ² of the zinc carbamate complex, respectively.
The amine compound represented by the general formula (D1) may be a monoamine compound or a diamine compound.
Preferred examples of the monoamine compound include aniline or an aniline derivative, 4-aminopyridine, 1-aminohexane, and cyclohexylamine. The aniline derivative is not particularly limited, but preferred examples include o-anisidine, m-anisidine, p-anisidine, 4-vinylaniline, 4-nitroaniline, 4-bromoaniline, 4-fluoroaniline, 4-cyanoaniline, 4-cyanoaniline, p-toluidine, 4-chloroaniline, 4-bromoaniline, and 4-fluoroaniline.
Preferred examples of the diamine compound include 4,4'-methylenedianiline, 2,4-tolylenediamine, 1,6-hexyldiamine, and derivatives thereof. Also preferred are compounds encompassed by general formula (D1'), in which one amino group of these diamine compounds or diamine compound derivatives is converted to a group having a urethane structure represented by formula (C').

(Alkoxysilane Compound (E))
In this embodiment, the term "alkoxysilane compound" refers to alkoxysilane and its derivatives. The specific type of alkoxysilane compound is not particularly limited and can be appropriately selected depending on the target carbamate compound. For example, an alkoxysilane compound represented by formula (E1) is preferably used.
(R ⁷ ) _4-n' Si (OR ⁶ ) _n' ...(E1)
(In formula (E1), R ⁶ 's are each independently a substituted or unsubstituted hydrocarbon group; R ⁷ 's are each independently a substituted or unsubstituted hydrocarbon group; and n' is an integer of 1 to 4. However, when n' is 2 or greater, two R ^6's may be bonded to each other to form a ring. Furthermore, when n' is 3 or less, R ⁶ and R ⁷ may be bonded to form a ring.)

(R ⁶ )
In formula (E1), each R ⁶ independently represents an unsubstituted or substituted monovalent hydrocarbon group.
The number of carbon atoms in ^R6 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.
Examples of the unsubstituted hydrocarbon group represented by ^R6 include 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, an n-pentyl group, an isopentyl 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, and an n-nonadecyl group. and n-docosyl groups; cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups; aromatic hydrocarbon groups such as phenyl, 1-naphthyl, 2-naphthyl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, 9-phenanthryl, 1-anthryl, 2-anthryl, 9-anthryl, 1-pyrenyl, 2-pyrenyl, 4-pyrenyl, 1-triphenylenyl, and 2-triphenylenyl groups; and the like.
When the hydrocarbon group represented by ^R6 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, or a tert-butyl group; a cycloalkyl group having 3 to 4 carbon atoms, such as a cyclopropyl group or a cyclobutyl group; an aromatic hydrocarbon group having 6 to 10 carbon atoms, such as a phenyl group, a 1-naphthyl group, or a 2-naphthyl group; heterocyclic groups, such as an oxygen-containing heterocyclic group, an sulfur-containing heterocyclic group, such as a thienyl group, or a nitrogen-containing heterocyclic group, such as a pyrrolyl group or a pyridyl group; a halogeno group, such as a fluoro group, a chloro group, a bromo group, or an iodo group; an isocyanate group; a cyano group; an amino group; an amido group; and a nitro group. Therefore, when the hydrocarbon group represented by ^R6 has a substituent, preferred examples of ^R6 include aralkyl groups such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, and a 2-naphthylmethyl group; a cycloalkylalkyl group such as a cyclohexylmethyl group; a hydrocarbon group having an oxygen-containing heterocycle such as a furfuryl group; a hydrocarbon group having a sulfur-containing heterocycle such as a thienylmethyl group; and a hydrocarbon group having a nitrogen-containing heterocycle such as a pyridylmethyl group; and the like, with a benzyl group and a phenethyl group being particularly preferred.
As ^R6 , a methyl group, an ethyl group, an n-propyl group, an isopropyl group, or an n-butyl group is particularly preferred from the viewpoint of the reaction efficiency between the alkoxysilane and carbon dioxide.

(R ⁷ )
In formula (E1), each R ⁷ independently represents an m′-valent hydrocarbon group which is unsubstituted or substituted.
The number of carbon atoms in ^R7 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.
Examples of the unsubstituted hydrocarbon group represented by ^R7 include the monovalent hydrocarbon groups exemplified for ^R6 . From the viewpoints of availability and stability, preferred examples include a methyl group, an ethyl group, a vinyl group, an allyl group, and a phenyl group.
Furthermore, when the hydrocarbon group represented by ^R7 has a substituent, examples of the substituent include those exemplified as the substituent of the hydrocarbon group represented by ^R6 . Among these, an isocyanate group or a cyano group is preferred.

(n′)
In formula (E1), n' is an integer of 1 to 4, and is preferably 2 or more, more preferably 3 or 4, and even more preferably 4, from the viewpoints of reaction efficiency and stability of the carbamate compound.

Specific examples of the alkoxysilanes represented by formula (E1) include methoxytrimethylsilane, methoxytriethylsilane, methoxytripropylsilane, methoxytriisobutylsilane, methoxytrioctylsilane, methoxytrihexadecylsilane, methoxytrivinylsilane, methoxytriphenylsilane, phenylmethoxydimethylsilane, phenylmethoxydiethylsilane, ethoxytrimethylsilane, ethoxytriethylsilane, ethoxytripropylsilane, ethoxytriisobutylsilane, ethoxytrioctylsilane, ethoxytriphenylsilane, ethoxytrivinylsilane, ethoxytriallylsilane, and ethoxydiethylsilane. monoalkoxysilanes such as phenylsilane, phenylethoxydipropylsilane, propoxytrimethylsilane, propoxytriethylsilane, propoxytripropylsilane, phenylpropoxydimethylsilane, phenylpropoxydiethylsilane, and phenylpropoxydipropylsilane; dimethoxydimethylsilane, dimethoxydiethylsilane, dimethoxydipropylsilane, phenyldimethoxymethylsilane, dimethoxymethylvinylsilane, dimethoxydiphenylsilane, diethoxydimethylsilane, diethoxydiethylsilane, diethoxydipropylsilane, diethoxymethylphenylsilane, diethoxyethylphenylsilane; Dialkoxysilanes such as diphenylpropylsilane, dipropoxydimethylsilane, dipropoxydiethylsilane, dipropoxydipropylsilane, phenyldipropoxymethylsilane, phenyldipropoxyethylsilane, phenyldipropoxypropylsilane, dibutoxydimethylsilane, dibutoxydiethylsilane, and phenyldimethoxyethylsilane; trimethoxymethylsilane, trimethoxyethylsilane, trimethoxypropylsilane, trimethoxyisobutylsilane, trimethoxyoctylsilane, trimethoxyhexadecylsilane, triethoxymethylsilane, triethoxyethylsilane, triethoxypropylsilane, and triethoxy Examples of the alkoxysilane include trialkoxysilanes such as isobutylsilane, triethoxyoctylsilane, trimethoxyvinylsilane, trimethoxyphenylsilane, triethoxyphenylsilane, triethoxyvinylsilane, triethoxyallylsilane, tripropoxymethylsilane, tripropoxyethylsilane, tripropoxypropylsilane, tripropoxyphenylsilane, 2-cyanoethyltriethoxysilane, and 3-(triethoxysilyl)propyl isocyanate; and tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, and tetrakis(2-ethylhexyloxy)silane.

From the viewpoints of availability and high reactivity, the alkoxysilane compound is preferably tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, trimethoxymethylsilane, triethoxymethylsilane, diethoxydimethylsilane, dimethoxydimethylsilane, ethoxytrimethylsilane, triethoxyphenylsilane, triethoxyvinylsilane, triethoxyallylsilane, 2-cyanoethyltriethoxysilane, 3-(triethoxysilyl)propyl isocyanate, 1,2-bis(triethoxysilyl)ethane, or 1,6-bis(triethoxysilyl)hexane, more preferably tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, trimethoxymethylsilane, or dimethoxydimethylsilane, and even more preferably tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, or tetrabutoxysilane.
The alkoxysilane may be a commercially available product or may be synthesized.
The amount of alkoxysilane used (charge amount) is not particularly limited, but is usually 1 equivalent or more, preferably 1.5 equivalents or more, more preferably 2.5 equivalents or more, and even more preferably 3 equivalents or more, relative to 1 equivalent of the amine compound, and is usually 20 equivalents or less, preferably 15 equivalents or less, and more preferably 10 equivalents or less.

(L-type ligand)
In this embodiment, it is preferable to carry out the carbamate production step by adding an L-type ligand.
The L-type ligand may be the same as or different from the ligand constituting the zinc carbamate complex, but it is preferable that they are the same.
Specific examples of the L-type ligand include the ligands exemplified in the description of the L-type ligand in "Zinc carbamate complex represented by general formula (1)" in the above section "1. Zinc carbamate complex," and preferred embodiments are also the same.
The amount of the ligand used (charge amount) is not particularly limited, but is usually 0.5 equivalents or more, preferably 1.0 equivalents or more, more preferably 2.0 equivalents or more, relative to 1 equivalent of the zinc carbamate complex, and is usually 20 equivalents or less, preferably 10 equivalents or less, more preferably 5 equivalents or less.

(Zinc carbamate complex)
The zinc carbamate complex described above in "1. Zinc carbamate complex" or the zinc carbamate complex obtained by the production method described above in "2. Production method for zinc carbamate complex" can be used as a catalyst in the carbamate production step.
The amount of the zinc carbamate complex used in the carbamate production step is preferably 0.01 mmol% or more, more preferably 0.1 mmol% or more, and even more preferably 1.0 mmol% or more, of the amount of the amine compound (D) used, preferably less than 10.0 mol%, more preferably 5.0 mol% or less, and even more preferably 3.0 mol% or less.

(Carbamate compound represented by formula (F1))
In the compound represented by formula (F1), ^R4 and ^R5 are derived from the amine compound represented by formula (D1), and ^R6 is derived from the alkoxysilane compound represented by formula (E1).
Examples of the carbamate compound represented by formula (F1) include the following compounds.

(solvent)
The carbamate production step may or may not use a solvent. From the viewpoint of achieving carbamate production under milder conditions, for example, from the viewpoint of enabling a reduction in the carbon dioxide gas filling pressure, a lower reaction temperature, and a shorter reaction time, it is preferable not to use a solvent. Note that "no solvent is used" means that no solvent is used separately from the reaction reagents. For example, when a reaction substrate such as alkoxysilane is used as a solvent, this refers to conditions in which no solvent is used. Furthermore, "solvent-free" is also used in the same sense as "no solvent is used."
The type of reaction solvent is not particularly limited, and examples thereof include alcohols such as ethanol, propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, t-butanol, allyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and glycerin; aliphatic hydrocarbons such as butane, hexane, octane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; and heterocyclic aromatic hydrocarbons such as pyridine. Examples of suitable solvents include aromatic compounds; aprotic polar solvents such as ethyl acetate, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, and N-methylpyrrolidone (NMP); ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran, and dioxane; nitriles such as acetonitrile, propionitrile, butyronitrile, benzonitrile, and 2-cyanopyridine; and ketones such as acetone and isopropyl ketone. Among these, acetonitrile is preferred. One type of solvent may be used, or two or more types may be used.
The amount of the solvent to be used is not particularly limited, but is usually 1 equivalent or more, preferably 1.5 equivalents or more, more preferably 2.5 equivalents or more, and even more preferably 4 equivalents or more, relative to 1 equivalent of the amine compound, and is usually 20 equivalents or less, preferably 15 equivalents or less, and more preferably 10 equivalents or less.

(Filling pressure)
In the carbamate production step, the charging pressure of carbon dioxide gas is not particularly limited, but is usually 0.05 MPa, preferably 0.1 MPa or more, and usually 10.0 MPa or less, preferably 5.0 MPa or less. When the charging pressure is within this range, the carbamate compound can be produced efficiently. Within the above-mentioned charging pressure range, under solvent-free conditions, the reaction tends to proceed more rapidly at a lower pressure range.

(Reaction temperature)
The reaction temperature of the carbamate production step is not particularly limited, and although it depends on the type of amine compound, the type of alkoxysilane, the presence or absence of a solvent, etc., it is usually 100°C or higher, preferably 120°C or higher, more preferably 140°C or higher, and usually 250°C or lower, preferably 230°C or lower, more preferably 200°C or lower. When the reaction temperature is within this range, the carbamate compound can be produced efficiently. Within the above-mentioned reaction temperature range, under solvent-free conditions, the reaction tends to proceed more rapidly at a lower temperature range.

(Reaction time)
The reaction time for the carbamate production step is not particularly limited and may be appropriately adjusted depending on the reaction temperature, amount of catalyst, reaction scale, etc. It is usually 30 minutes or more, preferably 1 hour or more, more preferably 2 hours or more, and usually 120 hours or less, preferably 100 hours or less, more preferably 80 hours or less. Within the above-mentioned reaction time range, the reaction tends to be completed in a shorter time under solvent-free conditions.

(Reaction vessel)
The reaction vessel is not particularly limited as long as it is made of a material that is stable against the carbamate compound, and can be appropriately selected depending on whether the process is a continuous process or a batch process. In one embodiment of the present invention, the process may be a continuous process or a batch process. In the case of a batch process, the reaction vessel is preferably a sealed reaction vessel (sealed reaction vessel), more preferably a sealed pressure-resistant vessel having a volume 10 to 100 times the volume of the mixture of the amine compound, the alkoxysilane compound, the zinc carbamate complex, and, if necessary, the solvent, and more preferably a stainless steel autoclave.

(Operation procedure)
First, the raw materials, an amine compound and an alkoxysilane compound, and a zinc carbamate complex as a catalyst are added to a reaction vessel. This reaction is preferably carried out under an inert gas atmosphere, such as nitrogen or argon. After the amine compound and alkoxysilane compound are added to the reaction vessel, the reactor is filled with the raw material, carbon dioxide, to create a carbon dioxide atmosphere. If a solvent is used, it can be added to the reaction vessel before introducing carbon dioxide into the reactor, or it can be added to the reactor simultaneously with the amine compound. During the reaction, an inert gas, such as nitrogen or argon, may be contained in the reaction vessel, as long as it does not significantly impair the effects of the present invention. Furthermore, stirring during the reaction is preferred; for example, a magnetic stirrer can be used. After the reaction, the mixture is cooled, the remaining gas is discharged, and the reaction product is recovered.

(Other processes)
The method for producing a carbamate compound according to this embodiment may include any other step in addition to the carbamate production step. The optional step may include a purification step for increasing the purity of the carbamate compound. In the purification step, purification methods commonly used in the field of organic synthesis, such as filtration, adsorption, column chromatography, and distillation, may be employed. Specifically, for example, the obtained solid may be filtered under a nitrogen atmosphere, washed with diethyl ether or the like, and vacuum dried.

The present invention will be explained in more detail below using examples, but modifications can be made as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1-1]
A 10 mL stainless steel autoclave was charged with aniline (373 mg, 4.0 mmol), zinc acetate (184 mg, 1.0 mmol), 1,10-phenanthroline (180 mg, 1.0 mmol), and acetonitrile (3 mL), and then filled with CO ₂ (3.0 MPa). The autoclave was then heated at 150°C for 3 hours. After cooling for 1 hour, the solid obtained under a nitrogen atmosphere was filtered, washed with diethyl ether (5.0 mL), and dried in vacuo to obtain zinc carbamate complex 1 in a 45% yield (198 mg). The structure of the compound was determined by single crystal X-ray structural analysis and ¹ H NMR spectroscopy. The structure of zinc carbamate complex 1 and ¹ H
The NMR results are shown below. The results of single-crystal X-ray crystal structure analysis of zinc carbamate complex 1 (ORTEP diagram and main crystal data) are also shown.

NMR data of 1: ¹ H NMR (400 MHz, DMSO-d ₆ , 300 K): δ 9.11 (s, 2H, phen), 8.87 (d,
² J _HH = 7 Hz, 2H, phen), 8.52 (s, 1H, NH), 8.25 (s, 2H, phen), 8.09 (s, 2H, phen), 7.39 (d, ² J _HH = 8 Hz, 2H, o-Ph), 7.09 (t, ² J _HH = 8 Hz, 2H, m-Ph), 6.74 (t, ² J _HH
= 8 Hz, 1H, p-Ph), 1.79 (s, 3H, OC(=O)CH ₃ ).

[Example 1-2]
A 10 mL stainless steel autoclave was charged with p-toluidine (429 mg, 4.0 mmol), zinc acetate (184 mg, 1.0 mmol), 1,10-phenanthroline (180 mg, 1.0 mmol), and acetonitrile (3 mL), and then filled with CO ₂ (3.0 MPa). The autoclave was then heated at 150°C for 3 hours. After allowing the mixture to cool for 1 hour, the resulting solid was filtered under a nitrogen atmosphere, washed with diethyl ether (5.0 mL), and dried under vacuum. The formation of zinc carbamate complex 2 was confirmed by ¹ H NMR. The structure of zinc carbamate complex 2 and the results of ¹ H NMR are shown below.

NMR data of 2: ¹ H NMR (400 MHz, DMSO-d ₆ , 300 K): δ 9.11 (s, 2H, phen), 8.88 (d,
² J _HH = 7 Hz, 2H, phen), 8.42 (s, 1H, NH), 8.26 (s, 2H, phen), 8.10 (s, 2H, phen), 7.27 (d, ² J _HH = 8 Hz, 2H, Ar), 6.89 (d, ² J _HH = 8 Hz, 2H, Ar), 2.15 (s, 3H, Ar-CH ₃ ), 1.78 (s, 3H, OC(=O)CH ₃ ).

[Examples 1-3]
A reaction was carried out in the same manner as in Example 1-2, except that p-toluidine was changed to 4-chloroaniline. The formation of zinc carbamate complex 3 was confirmed by ¹ H NMR. The structure of zinc carbamate complex 3 and the results of ¹ H NMR are shown below.

NMR data of 3: ¹ H NMR (400 MHz, DMSO-d ₆ , 300 K): δ 9.09 (s, 2H, phen), 8.90 (d,
² J _HH = 7 Hz, 2H, phen), 8.64 (s, 1H, NH), 8.26 (s, 2H, phen), 8.16-8.03 (m, 2H, phen), 7.41 (d, ² J _HH = 8 Hz, 2H, Ar), 7.12 (d, ² J _HH = 8 Hz, 2H, Ar), 1.77 (s, 3H, OC(=O)CH ₃ ).

[Examples 1-4]
A reaction was carried out in the same manner as in Example 1-2, except that p-toluidine was changed to 4-methoxyaniline. The formation of zinc carbamate complex 4 was confirmed by ¹ H NMR. The structure of zinc carbamate complex 4 and the results of ¹ H NMR are shown below.

NMR data of 4: ¹ H NMR (400 MHz, DMSO-d ₆ , 300 K): δ 9.10 (d, ² J _HH = 5 Hz, 2H, phen), 8.88 (dd, ² J _HH = 8 and 1 Hz, 2H, phen), 8.38 (s, 1H, NH), 8.24 (s, 2H, phen), 8.11 (dd, ² J _HH = 8 and 5 Hz, 2H, phen), 7.30 (d, ² J _HH = 8 Hz, 2H, Ar), 6.70 (d,
² J _HH = 8 Hz, 2H, Ar), 3.64 (s, 3H, OCH ₃ ), 1.78 (s, 3H, OC(=O)CH ₃ ).

[Examples 1-5]
The reaction was carried out in the same manner as in Example 1-2, except that p-toluidine was changed to cyclohexylamine. The formation of zinc carbamate complex 5 was confirmed by ¹ H NMR. The structure of zinc carbamate complex 5 and the results of ¹ H NMR are shown below.

NMR data of 5: ¹ H NMR (400 MHz, DMSO-d ₆ , 300 K): δ 9.07 (d, ² J _HH = 4 Hz, 2H, phen), 8.88 (d, ² J _HH = 8 Hz, 2H, phen), 8.25 (s, 2H, phen), 8.09 (dd, ² J _HH = 8 and 4 Hz, 2H, phen), 6.27 (s, 1H, NH), 2.73-3.64 (m, 1H, N-CH), 1.78 (s, 3H, OC(=O)C
H ₃ ), 1.75-1.45 (m, 6H, CH ₂ ), 1.75-1.45 (m, 6H, CH ₂ ), 1.23-0.90 (m, 5H, CH ₂ ).

Examples 1-1 to 1-5 confirmed that novel zinc carbamate complexes can be synthesized and isolated as stable compounds by reacting various amine compounds, zinc acetate, 1,10-phenanthroline, and carbon dioxide.

[Example 2-1]
A 10 mL stainless steel autoclave was charged with aniline (93 mg, 1.0 mmol), zinc carbamate complex 1 (8.8 mg, 0.020 _mmol ), Si(OMe) (304 mg, 2.0 mmol), and acetonitrile (3 mL), and the autoclave was filled with _CO (3.0 MPa) and heated at 140°C for 24 hours to give N-phenylcarbamic acid methyl ester in a 98% yield, as determined by ¹ H NMR using mesitylene (50 mg) as an internal standard.

[Example 2-2]
A 10 mL stainless steel autoclave was charged with aniline (47 mg, 0.50 mmol), zinc carbamate complex 1 (4.4 mg, 0.010 _mmol ), and Si(OMe) (1522 mg, 10.0 mmol), and the autoclave was filled with _CO (0.1 MPa). The autoclave was then heated at 140°C for 4 hours to give N-phenylcarbamic acid methyl ester in a 90% yield, as determined by ¹ H NMR using mesitylene (50 mg) as an internal standard.

Furthermore, Examples 2-1 and 2-2 confirmed that by using the obtained zinc carbamate complex as a catalyst, N-phenylcarbamic acid methyl ester can be efficiently produced from aniline, tetramethoxysilane, and carbon dioxide in a high yield of over 85%. Furthermore, in Example 2-2, in which the carbamate production step was carried out under solvent-free conditions, N-phenylcarbamic acid methyl ester was obtained in a high yield of 90%, despite the lower carbon dioxide gas charging pressure and reaction temperature and shorter reaction time than in Example 2-1, in which acetonitrile solvent was used.

According to the present invention, zinc carbamate complexes can be produced using an amine compound, a zinc compound, and carbon dioxide gas as raw materials. The zinc carbamate complex is an important intermediate in carbamate synthesis using carbon dioxide gas, an amine, TROS, and a zinc catalyst. Furthermore, the zinc carbamate complex itself also serves as a catalyst for the above-mentioned carbamate synthesis. Carbamates can be converted into isocyanates, which are polyurethane raw materials, by thermal decomposition, making this method useful as a new polyurethane raw material synthesis method using inexpensive, abundant, and low-toxicity carbon dioxide gas and recyclable, reusable TROS as raw materials.

Claims (5)

A zinc carbamate complex crystal represented by general formula (1) :

(In formula (1), ^R1 is a hydrogen atom ; ^R2 is an unsubstituted phenyl group, an alkyl-substituted phenyl group, an alkoxy-substituted phenyl group, a halogen-substituted phenyl group, or an unsubstituted cycloalkyl group ; m is 1 ; X is a triflate ligand or an acetate ligand ; L is an L-ligand, and the L-ligand is 1,10-phenanthroline or 2,2'-bipyridyl ; and n is the number of the L-ligands and is 1.) A method for producing a zinc carbamate complex crystal represented by general formula (1), comprising a reaction step of reacting an amine compound represented by general formula ( A), a zinc compound represented by general formula (B ), an L-ligand, and carbon dioxide (excluding the step of reacting in the presence of an alkoxysilane).

In formula (A), ^R1 is a hydrogen atom ; ^R2 is an unsubstituted phenyl group, an alkyl-substituted phenyl group, an alkoxy-substituted phenyl group, a halogen-substituted phenyl group, or an unsubstituted cycloalkyl group ; and m is 1 .
In formula (B), X and Y are triflate or acetate ligands .
In formula (1), R ¹ , R ² and m are respectively defined as R ¹ , R ² and m in formula (A); X is defined as X in formula (B); L is an L-ligand, and the L-ligand is 1,10-phenanthroline or 2,2′-bipyridyl ; and n is the number of the L-ligands and is 1. 3. The method for producing a zinc carbamate complex crystal according to claim 2 , wherein the amine compound represented by the general formula (A) is a monoamine compound selected from aniline and cyclohexylamine. adding a catalyst, an amine compound (D), and an alkoxysilane (E) to a reaction vessel;
introducing carbon dioxide into the reaction vessel;
a carbamate production step of reacting the amine compound (D), the alkoxysilane (E), and carbon dioxide to produce a carbamate compound (F),
The method for producing a carbamate compound, wherein the catalyst is the zinc carbamate complex crystal according to claim 1 . The method for producing a carbamate compound according to claim 4 , wherein the alkoxysilane (E) is a tetraalkoxysilane.