Method for producing isocyanate

Abstract

This method for producing an isocyanate comprises: a step (1) for reacting a compound A having an element M-oxygen double bond with a compound B having an amino group to obtain a product C; and a step (2) for reacting the product C with at least one selected from the group consisting of carbon dioxide, a carbonate, and a hydrogen carbonate to obtain an isocyanate. The element M is a metal element or P. In the step (1), the ratio of the number of the element M-oxygen double bonds of the compound A to the number of moles of the amino group of the compound B is 0.5 or more.

Description

Isocyanate manufacturing method

[0001] The present invention relates to a method for producing isocyanates.

[0002] The phosgene process, which involves reacting an amine with phosgene, has been used as the main industrial method for producing isocyanates. However, the phosgene process has many problems from the viewpoints of environmental impact and safety, such as the extremely high toxicity of phosgene and the generation of hydrogen chloride as a by-product.

[0003] Therefore, in recent years, methods for producing isocyanates without using phosgene have been studied. For example, Patent Documents 1 and 2 describe methods in which a carbamate is produced from an amine, carbon dioxide, and an alcohol by a multi-stage reaction, and then an isocyanate is produced by a thermal decomposition reaction of the carbamate. Patent Document 3 describes a method in which a carbamate is produced using an amine, an N-unsubstituted carbamate, and an alcohol, and then an isocyanate is produced by a thermal decomposition reaction of the carbamate.

[0004] JP 2022-078234 A JP 2021-095357 A JP 2016-117674 A

[0005] The above-mentioned methods for producing isocyanates involve complicated production steps.

[0006] Therefore, an object of the present invention is to provide a new method for producing an isocyanate by a simple process.

[0007] The present invention provides a method for producing an isocyanate, comprising: a step (1) of reacting a compound A having an element M-oxygen double bond with a compound B having an amino group to obtain a product C; and a step (2) of reacting the product C with at least one selected from the group consisting of carbon dioxide, carbonates, and hydrogencarbonates to obtain an isocyanate, wherein the element M is a metal element or P, and in the step (1), the ratio of the number of double bonds in the compound A to the number of moles of the amino groups in the compound B is 0.5 or more.

[0008] According to the present invention, isocyanates can be produced by a simple process.

[0009] The method for producing an isocyanate according to a first aspect of the present invention includes: a step (1) of reacting a compound A having an element M-oxygen double bond with a compound B having an amino group to obtain a product C; and a step (2) of reacting the product C with at least one selected from the group consisting of carbon dioxide, carbonates, and hydrogencarbonates to obtain an isocyanate, wherein the element M is a metal element or P, and in the step (1), the ratio of the number of double bonds in the compound A to the number of moles of the amino groups in the compound B is 0.5 or more.

[0010] In a second aspect of the present invention, for example, in the method for producing an isocyanate according to the first aspect, the ratio is 1.0 or more.

[0011] In a third aspect of the present invention, for example, in the method for producing an isocyanate according to the first or second aspect, the reaction temperature in the step (2) is 100° C. or lower.

[0012] In a fourth aspect of the present invention, for example, in the method for producing an isocyanate according to any one of the first to third aspects, the step (1) and the step (2) are carried out in one pot.

[0013] In a fifth aspect of the present invention, for example, in the method for producing an isocyanate according to any one of the first to fourth aspects, the element M is V, Fe, Mo, Ta, Nb, Ti, W, or P.

[0014] In a sixth aspect of the present invention, for example, in the method for producing an isocyanate according to any one of the first to fifth aspects, the compound B is a primary amine.

[0015] In a seventh aspect of the present invention, for example, in the method for producing an isocyanate according to any one of the first to sixth aspects, the compound B is a compound represented by the following general formula (B): R-NX2 (B) In general formula (B), R represents a hydrocarbon group which may have a substituent, and two Xs each independently represent a hydrogen atom or a protecting group.

[0016] In an eighth aspect of the present invention, for example, in the method for producing an isocyanate according to the seventh aspect, the hydrocarbon group contains at least one selected from the group consisting of an aliphatic ring and an aromatic ring.

[0017] In a ninth aspect of the present invention, for example, in the method for producing an isocyanate according to any one of the first to eighth aspects, the product C has an element M-nitrogen double bond.

[0018] In a tenth aspect of the present invention, for example, in the method for producing an isocyanate according to any one of the first to ninth aspects, the compound A is further obtained by the reaction in the step (2).

[0019] In an eleventh aspect of the present invention, for example, in the method for producing an isocyanate according to any one of the first to tenth aspects, the reaction in the step (1) is carried out under an inert atmosphere.

[0020] In a twelfth aspect of the present invention, for example, in the method for producing an isocyanate according to any one of the first to eleventh aspects, in the step (2), the reaction is carried out in a solvent, and the solvent contains at least one selected from the group consisting of toluene, 1,4-dioxane, and acetonitrile.

[0021] In a thirteenth aspect of the present invention, for example, in the method for producing an isocyanate according to any one of the first to twelfth aspects, in the step (1), the reaction is carried out in the presence of a base.

[0022] A method for producing an isocyanate derivative according to a fourteenth aspect of the present invention includes a step (3) of converting the isocyanate obtained by the method for producing an isocyanate according to any one of the first to thirteenth aspects into an isocyanate derivative.

[0023] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0024] [Method for Producing Isocyanate] The method for producing an isocyanate according to the first embodiment of the present invention includes step (1) of reacting compound A having an element M-oxygen double bond with compound B having an amino group to obtain product C, and step (2) of reacting product C obtained in step (1) with at least one selected from the group consisting of carbon dioxide, carbonates, and hydrogencarbonates to obtain an isocyanate. Element M is a metal element or P. In step (1), the ratio of the number of element M-oxygen double bonds in compound A to the number of moles of amino groups in compound B is 0.5 or more.

[0025] The reactions in steps (1) and (2) may be carried out using a batch reactor or a flow reactor (for example, a plug flow reactor (PFR) or a continuous stirred tank reactor (CSTR)).

[0026] Step (1) and step (2) may be carried out in one pot.

[0027] As used herein, "step (1) and step (2) are carried out in one pot" means that the reactions of step (1) and step (2) are carried out without including a step of isolating and purifying product C between step (1) and step (2). Step (1) and step (2) may be carried out in the same reaction vessel or in different reaction vessels, as long as they do not include a step of isolating and purifying product C. By carrying out step (1) and step (2) in one pot, for example, it is possible to achieve an improvement in the efficiency of the production process. As used herein, "a step of isolating and purifying product C" means a step of making the purity of product C 95% or more when the solvent is removed.

[0028] Step (1) and step (2) may be carried out in the same reaction vessel. The reaction in step (1) and the reaction in step (2) may be carried out consecutively in the same reaction vessel.

[0029] Each step will be described in detail below.

[0030] <Step (1)> Compound A is a compound having an element M-oxygen double bond.

[0031] The number of element M-oxygen double bonds in one molecule of compound A may be 1 or more, for example, 1 to 5. The number of element M-oxygen double bonds in one molecule of compound A is preferably 1. However, in some cases, the number of element M-oxygen double bonds in one molecule of compound A may be 2 or more.

[0032] The element M is a metal element or P. The element M may be a metal element.

[0033] The element M may be V, Fe, Mo, Ta, Nb, Ti, W, or P, or may be V, Fe, Mo, Ta, Nb, Ti, or W, or may be V, Fe, Mo, or Nb, or may be V. That is, the compound A may have a vanadium-oxygen double bond.

[0034] In a preferred embodiment of the present invention, the compound A may be a complex having a ligand that coordinates with the element M.

[0035] Examples of the ligand include a hydrocarbon group which may have a substituent, an oxyhydrocarbon group which may have a substituent, and a halogen.

[0036] The number of carbon atoms in the hydrocarbon group is not particularly limited as long as it is at least 1. The number of carbon atoms in the hydrocarbon group may be, for example, 20 or less, 15 or less, 10 or less, 5 or less, or 3 or less.

[0037] The hydrocarbon group may be a linear or branched chain hydrocarbon group. The hydrocarbon group may be an alkyl group, an alkenyl group, or an alkynyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and a sec-butyl group. Examples of the alkenyl group include a vinyl group and an allyl group. Examples of the alkynyl group include an ethynyl group.

[0038] Examples of the substituent on the hydrocarbon group include halogen, amino group, alkoxy group, alkyl ester group, carboxyl group, and hydroxyl group.

[0039] Examples of hydrocarbon groups contained in the oxyhydrocarbon group include those described above. The oxyhydrocarbon group may be an alkoxy group. Examples of the alkoxy group include a methoxy group, an ethoxy group, and an isopropoxy group. Examples of the substituent of the oxyhydrocarbon group include those described above for hydrocarbon groups. Examples of the substituted oxyhydrocarbon group include a group derived from triethanolamine (TEA).

[0040] Examples of halogen include fluorine, chlorine, bromine, and iodine, and an example is chlorine.

[0041] The ligand is preferably an isopropoxy group, an ethyl group, an ethoxy group, chlorine, or TEA.

[0042] The number of ligands can be adjusted appropriately depending on the type of element M. The number of ligands may be 1 or more, for example, 1 to 5. The number of ligands may be 3 or 4. The number of ligands is preferably 3.

[0043] Compound A may be a compound represented by the following general formula (A): n VO (A) In general formula (A), L represents a hydrocarbon group which may have a substituent, an oxyhydrocarbon group which may have a substituent, or a halogen, and n is a natural number of 1 to 5. When n is 2 or more, the multiple Ls are independent of each other. At least two selected from the multiple Ls may be linked to each other.

[0044] Examples of the hydrocarbon group which may have a substituent and the oxyhydrocarbon group which may have a substituent are those mentioned above.

[0045] In formula (A), n may be 3 or 4. n is preferably 3.

[0046] In formula (A), L is preferably an alkoxy group, more preferably an isopropoxy group.

[0047] Compound A is vanadium(V) oxytriisopropoxide (VO(O iVO(OEt)3, VO(OEt)Cl2, VOCl3, or VO(TEA).

[0048] Compound A is not limited to the above-mentioned complexes. In another preferred embodiment of the present invention, compound A may be an oxide of element M or an inorganic salt containing element M. Examples of compound A include VO, NHVO, NaVO, TiO, WO, FeO, FeO, NbO, NbO, and (NH)MoO.

[0049] In yet another preferred embodiment of the present invention, the oxide of element M or the inorganic salt containing element M as compound A may be supported on a support. That is, in step (1), product C may be obtained by reacting a complex of compound A having an element M-oxygen double bond and a support supporting compound A with compound B having an amino group. The support is preferably a solid capable of supporting compound A. In this specification, "solid" means a substance that is in a solid state at atmospheric pressure and 20°C.

[0050] The carrier may contain a compound S having a cation D1 with an ionic radius of greater than 60.5 pm. In the complex, it is preferable that the compound S is different from the above-mentioned compound A. In this specification, the "ionic radius" is a value based on the definition described in Shannon et al., Acta Cryst. A 32 (1976) 751. The ionic radius is usually determined by the type of cation, the valence of the cation, and the coordination number of the cation.

[0051] The ionic radius of cation D1 may be greater than 60.5 pm, 61 pm or more, 63 pm or more, 65 pm or more, 68 pm or more, 70 pm or more, 75 pm or more, 80 pm or more, 85 pm or more, 90 pm or more, 95 pm or more, or even 100 pm or more. The upper limit of the ionic radius of cation D1 is not particularly limited, and may be, for example, 200 pm or less, or 150 pm or less. In some cases, the ionic radius of cation D1 may be 100 pm or less.

[0052] The valence of the cation D1 is, for example, 1 to 6, and preferably 1 to 4. The valence of the cation D1 may be 3 or less, or 2 or less, depending on the case.

[0053] Cation D1 is preferably a metal cation, and the metal cation preferably contains at least one selected from the group consisting of magnesium ions, cerium ions, zirconium ions, sodium ions, calcium ions, manganese ions, cobalt ions, lanthanum ions, zinc ions, potassium ions, indium ions, niobium ions, barium ions, strontium ions, iron ions, and yttrium ions, more preferably contains at least one selected from the group consisting of magnesium ions and cerium ions, and particularly preferably contains a magnesium ion.

[0054] Compound S typically further has an anion D2 bonded to cation D1. Examples of anion D2 include oxide ions, hydroxide ions, carbonate ions, and phosphate ions, and an oxide ion is preferred.

[0055] The compound S preferably has a metal cation as the cation D1 and an oxide ion as the anion D2, i.e., the compound S is preferably a metal oxide having a metal cation.

[0056] Specific examples of metal oxides include MgO (ionic radius of magnesium ion: 72 pm), CeO2 (ionic radius of cerium ion: 97 pm), ZrO2 (ionic radius of zirconium ion: 78 pm), CaO (ionic radius of calcium ion: 100 pm), MnO (ionic radius of manganese ion: 67 to 83 pm), CoO (ionic radius of cobalt ion: 65 to 74.5 pm), Fe2O3 (ionic radius of iron ion: 78 pm), and YO3 (ionic radius of yttrium ion: 90 pm). Compound S preferably contains at least one selected from the group consisting of MgO and CeO2, and particularly preferably contains MgO.

[0057] Compound S may be a compound other than a metal oxide, such as a hydroxide salt such as NaOH (ionic radius of sodium ion: 102 pm), a carbonate salt such as CaCO (ionic radius of calcium ion: 112 pm), or a hydroxyphosphate salt such as Ca(PO)(OH) (ionic radius of calcium ion: 118 pm).

[0058] The carrier may contain Compound S as a main component. In this specification, "main component" means the component contained in the carrier in the largest amount by weight. The content of Compound S in the carrier may be, for example, 80 wt % or more, 90 wt % or more, 95 wt % or more, or even 99 wt % or more. The carrier may be substantially composed of Compound S.

[0059] In the composite, the content of the carrier is, for example, 99.9 wt% or less, and may be 99.5 wt% or less, 99 wt% or less, 97 wt% or less, 95 wt% or less, 92 wt% or less, or even 90 wt% or less. The lower limit of the content of the carrier may be, for example, 50 wt% or more, 70 wt% or more, or even 80 wt% or more.

[0060] The shape of the carrier is not particularly limited, and may be, for example, particulate. In this specification, particulate includes spherical, ellipsoidal, scaly, fibrous, and the like.

[0061] Compound B is a compound having an amino group.

[0062] Compound B is preferably a primary amine.

[0063] The number of amino groups in one molecule of compound B may be one or two or more.

[0064] Compound B may contain a cyclic structure. Compound B may contain one cyclic structure or may contain two or more cyclic structures. The cyclic structure may or may not contain a heteroatom. The cyclic structure may be an aliphatic ring or an aromatic ring. An example of Compound B containing a cyclic structure having a heteroatom is tetrahydrofuranamine.

[0065] Aliphatic rings include, for example, cyclohexane, cyclopentane, and adamantane. Aromatic rings include, for example, benzene, naphthalene, and anthracene.

[0066] In compound B, the cyclic structure and the nitrogen may or may not be directly bonded. In compound B, the aliphatic ring and the nitrogen may be directly bonded. Compound B may be a primary amine in which an amino group and an aliphatic ring are directly bonded.

[0067] Compound B may be a compound represented by the following general formula (B): R-NX2 (B) In formula (B), R represents a hydrocarbon group which may have a substituent, and two Xs each independently represent a hydrogen atom or a protecting group.

[0068] Examples of the protecting group include silyl protecting groups and carbamate protecting groups. Examples of the silyl protecting group include trimethylsilyl group (TMS group), triethylsilyl group (TES group), triisopropylsilyl group (TIPS group), tert-butyldimethylsilyl group (TBDMS group), and tert-butyldiphenylsilyl group (TBDPS group). Examples of the carbamate protecting group include tert-butoxycarbonyl group (Boc group) and benzyloxycarbonyl group (Cbz group).

[0069] In formula (B), X is preferably a hydrogen atom.

[0070] In general formula (B), the number of carbon atoms in the hydrocarbon group is not particularly limited as long as it is at least 1. The number of carbon atoms in the hydrocarbon group may be, for example, 20 or less, 15 or less, 12 or less, or 10 or less.

[0071] In a preferred embodiment of the present invention, the hydrocarbon group in general formula (B) contains a cyclic structure. In general formula (B), the hydrocarbon group may contain at least one ring selected from the group consisting of an aliphatic ring and an aromatic ring.

[0072] The hydrocarbon group containing a cyclic structure is, for example, an alicyclic hydrocarbon group or an aromatic cyclic hydrocarbon group. In this specification, the term "alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an aliphatic ring as a cyclic structure and does not contain an aromatic ring, and includes both monocyclic alicyclic hydrocarbon groups and polycyclic alicyclic hydrocarbon groups. Here, the alicyclic hydrocarbon group does not need to be composed only of an aliphatic ring, and may contain a chain structure as part of it. The term "aromatic cyclic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring as a cyclic structure. Here, the aromatic cyclic hydrocarbon group does not need to be composed only of an aromatic ring, and may contain an aliphatic ring or a chain structure as part of it.

[0073] Examples of the alicyclic hydrocarbon group include a cyclohexyl group, a cyclopentyl group, and an adamantyl group, and the alicyclic hydrocarbon group is preferably a cyclohexyl group.

[0074] The aromatic hydrocarbon group may contain a benzene ring, such as a phenyl group, a methylphenyl group, a methoxyphenyl group, or a benzyl group.

[0075] In another preferred embodiment of the present invention, the hydrocarbon group in general formula (B) may be a linear or branched chain hydrocarbon group, and may be an alkyl group, an alkenyl group, or an alkynyl group.

[0076] Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, sec-butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. Examples of the alkenyl group include vinyl and allyl groups. Examples of the alkynyl group include ethynyl groups.

[0077] The substituents may be any substituent, such as those described above for Compound A.

[0078] Examples of compound B include ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, cyclohexylamine, cyclopentylamine, 2-phenylmethylamine, 2-phenylethylamine (phenethylamine), 1-phenylethylamine, 2-phenylpropylamine, 3-phenylpropylamine, 3,3-diphenylpropylamine, 2-(4-methylphenyl)ethylamine, 2-(4-bromophenyl)ethylamine, 2-(4-trifluoromethylphenyl)ethylamine, 3-ethoxypropylamine, 1-adamantanamine, 4-methoxyaniline, tetrahydrofuran-2-methaneamine, hexamethylenediamine, 1,5-pentamethylenediamine, toluenediamine, toluenediamine, 4,4'-methylenedianiline, and 2,4,6-trimethylaniline. When structural isomers exist in the compounds exemplified above, the structural isomers are also included in the examples. Compound B is preferably cyclohexylamine.

[0079] In the method for producing an isocyanate according to the first embodiment, various types of isocyanates can be produced by selecting the compound B.

[0080] As described above, in step (1), compound A and compound B are reacted to obtain product C. In step (1), the ratio of the number of element M-oxygen double bonds in compound A to the number of moles of amino groups in compound B is 0.5 or more. In this specification, the "ratio of the number of element M-oxygen double bonds in compound A to the number of moles of amino groups in compound B in step (1)" is a value calculated by the formula: (the number of element M-oxygen double bonds contained in one molecule of compound A multiplied by the amount of substance of compound A used in step (1)) / (the number of amino groups contained in one molecule of compound B multiplied by the amount of substance of compound B used in step (1)).

[0081] In step (1), the ratio of the number of elemental M-oxygen double bonds of compound A to the number of moles of amino groups of compound B may be 0.8 or more, preferably 1.0 or more. In step (1), the ratio of the number of elemental M-oxygen double bonds of compound A to the number of moles of amino groups of compound B may be 10.0 or less, 7.0 or less, 5.0 or less, 3.0 or less, or even 2.0 or less. In step (1), the ratio of the number of elemental M-oxygen double bonds of compound A to the number of moles of amino groups of compound B may be, for example, 0.5 or more and 10.0 or less, 0.8 or more and 3.0 or less, 1.0 or more and 1.5 or less, 1.0 or more and 1.2 or less, or 1.0 or more and 1.1 or less. In step (1), the ratio of the number of elemental M-oxygen double bonds of compound A to the number of moles of amino groups of compound B may be 1.0.

[0082] In step (1), the ratio of the amount of substance of compound A to the amount of substance of compound B may be 0.8 or more, preferably 1.0 or more. In step (1), the ratio of the amount of substance of compound A to the amount of substance of compound B may be 10.0 or less, 7.0 or less, 5.0 or less, 3.0 or less, or even 2.0 or less. In step (1), the ratio of the amount of substance of compound A to the amount of substance of compound B may be 1.0 or more and 2.0 or less, 1.0 or more and 1.5 or less, 1.0 or more and 1.2 or less, or 1.0 or more and 1.1 or less. In step (1), the ratio of the amount of substance of compound A to the amount of substance of compound B may be 1.0.

[0083] The product C obtained by reacting the compound A with the compound B may have an element M-nitrogen double bond. The element M contained in the product C is derived from the compound A.

[0084] The number of element M-nitrogen double bonds in one molecule of product C may be 1 or more, for example, 1 to 5. The number of element M-nitrogen double bonds in one molecule of product C is preferably 1. However, in some cases, the number of element M-nitrogen double bonds in one molecule of product C may be 2 or more.

[0085] Product C may contain a cyclic structure. Compound B may contain one cyclic structure or two or more cyclic structures. The cyclic structures are as described above for Compound B.

[0086] In the product C, the cyclic structure and the nitrogen may or may not be directly bonded. In the product C, the aliphatic ring and the nitrogen may be directly bonded.

[0087] In a preferred embodiment of the present invention, the product C may have a ligand that coordinates with the element M.

[0088] Examples of the ligand include those described above for Compound A.

[0089] The product C may be a compound represented by the following general formula (C): n VNR (C) In general formula (C), R represents a hydrocarbon group which may have a substituent, L represents a hydrocarbon group which may have a substituent, an oxyhydrocarbon group which may have a substituent, or a halogen, and n is a natural number of 1 to 5. When n is 2 or more, multiple Ls are independent of each other. At least two selected from the multiple Ls may be linked to each other. That is, R is the same as in general formula (B) above, and L is the same as in general formula (A) above. In general formula (C), N is bonded to V and R, and L is coordinated to V. In general formula (C), n may be 3 or 4. n is preferably 3.

[0090] The product C is not limited to the above. In another preferred embodiment of the present invention, the product C may not have a ligand that coordinates with the element M.

[0091] In step (1), the reaction of compound A with compound B may be carried out under an inert atmosphere. The inert atmosphere may be a nitrogen atmosphere.

[0092] In step (1), the reaction between compound A and compound B may be carried out in the presence of a base. The base is not particularly limited and may be an inorganic base or an organic base. Examples of inorganic bases include hydride salts such as sodium hydride and lithium hydride, hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, and barium hydroxide, carbonates such as sodium carbonate, potassium carbonate, lithium carbonate, barium carbonate, sodium bicarbonate, and potassium bicarbonate, and ammonia. Examples of organic bases include amines, nitrogen-containing aromatic compounds, and urea. These bases may be used alone or in combination. The base is preferably sodium hydride, N,N-diisopropylethylamine, diazabicycloundecene (DBU), or 1,8-bis(dimethylamino)naphthalene (DMAN).

[0093] The base may also function as a dehydrating agent. For example, when sodium hydride is used as the base in step (1), it is converted into sodium hydroxide by the reaction and can be used as a dehydrating agent as described below.

[0094] The amount of base used is not particularly limited. For example, the ratio of the amount of base used to the number of moles of amino groups in compound B is 0.20 or more, 0.50 or more, 0.70 or more, 0.80 or more, 0.90 or more, or even 1.0 or more. The ratio of the amount of base used to the number of moles of amino groups in compound B is the molar amount of base (mol) / (the number of amino groups contained in one molecule of compound B × the molar amount of compound B) (mol).

[0095] In step (1), the reaction temperature is, for example, 150°C or lower, 130°C or lower, 120°C or lower, 100°C or lower, 90°C or lower, 80°C or lower, and preferably 70°C or lower. The reaction temperature is, for example, 20°C or higher, 25°C or higher, or even 30°C or higher. The reaction temperature may be 20°C or higher and 130°C or lower, or 20°C or higher and 70°C or lower. In this specification, the reaction temperature means the temperature of the reaction system.

[0096] In step (1), the reaction time is not particularly limited. From the viewpoint of obtaining a sufficient amount of product C, the reaction time is, for example, 10 minutes or more, 1 hour or more, or even 2 hours or more. The reaction time is, for example, 48 hours or less, 24 hours or less, 12 hours or less, 6 hours or less, or even 2 hours or less.

[0097] In step (1), the reaction between compound A and compound B may be carried out in a solvent. The solvent may be a polar solvent or a nonpolar solvent. In this specification, a nonpolar solvent is a solvent having a relative dielectric constant of 8.0 or less at 25°C. In this specification, a polar solvent is a solvent having a relative dielectric constant of more than 8.0 at 25°C.

[0098] Examples of non-polar solvents include toluene, benzene, xylene, hexane, 1,4-dioxane, tetrahydrofuran, ethyl acetate, cyclopentyl methyl ether, and mixed solvents thereof. The non-polar solvent is preferably toluene.

[0099] Examples of polar solvents include acetonitrile, dimethyl sulfoxide, dichloromethane, propylene carbonate, methanol, ethanol, dimethylacetamide (DMA), and mixed solvents thereof. The polar solvent is preferably DMA, acetonitrile, or dichloromethane.

[0100] From the viewpoint of efficiency, the solvent is preferably a non-polar solvent. By using the same solvent in the subsequent step (2), the efficiency of the production method of the present invention can be improved. Even when the solvent is a polar solvent, the efficiency of the production method of the present invention can be improved by using the same solvent in the subsequent step (2).

[0101] In step (1), a dehydrating agent may be further used. This can suppress decomposition of product C. As the dehydrating agent, known dehydrating agents such as molecular sieves, N,N'-dicyclohexylcarbodiimide (DCC), sodium sulfate, and magnesium oxide can be used. Furthermore, as described above with respect to bases, a base that can also function as a dehydrating agent may be used.

[0102] In step (1), additives may be further used, such as antioxidants and reaction accelerators.

[0103] <Step (2)> As described above, in step (2), the product C obtained in step (1) is reacted with at least one selected from the group consisting of carbon dioxide, carbonates, and hydrogencarbonates to obtain an isocyanate.

[0104] The ratio of the total amount of carbon dioxide, carbonate, and bicarbonate to the amount of compound B as a starting material may be 1 or more. The carbon dioxide, carbonate, and bicarbonate are preferably in excess relative to the amount of compound B as a starting material. In step (2), the ratio of the total amount of carbon dioxide, carbonate, and bicarbonate to the amount of product C may be 1 or more.

[0105] Examples of carbonates and bicarbonates include carbonates and bicarbonates of alkali metals and alkaline earth metals. Examples of bicarbonates include sodium bicarbonate and potassium bicarbonate. Examples of carbonates include sodium carbonate, potassium carbonate, potassium sodium carbonate, and sodium sesquicarbonate.

[0106] Carbonates and bicarbonates can be produced by the reaction of carbon dioxide with a base. For example, carbonates and bicarbonates may be produced by introducing carbon dioxide into a basic solution.

[0107] In step (2), the product C may be reacted with carbon dioxide to obtain an isocyanate.

[0108] Step (2) may be carried out in an atmosphere containing carbon dioxide or in a carbon dioxide atmosphere.

[0109] The atmosphere containing carbon dioxide may be obtained by replacing the entire atmosphere in a reaction vessel containing product C obtained in step (1) with carbon dioxide, or by bubbling carbon dioxide into a solution containing product C obtained in step (1). That is, the reaction of product C with carbon dioxide in step (2) may be carried out after replacing the atmosphere in a reaction vessel containing product C obtained in step (1) with carbon dioxide, or may be carried out while bubbling carbon dioxide into a solution containing product C obtained in step (1).

[0110] In step (2), the reaction temperature may be, for example, less than 130°C or 100°C or less. The reaction temperature is, for example, 90°C or less, 80°C or less, preferably 70°C or less, and more preferably 30°C or less. The reaction temperature is, for example, 20°C or more, or even 25°C or more. The reaction temperature may be 20°C or more and 70°C or less. The reaction temperature may be 25°C or more and 50°C or less, or 30°C or more and 50°C or less. The above configuration can improve the yield of isocyanate.

[0111] In step (2), the reaction time is not particularly limited. The reaction time is, for example, 3 minutes or more, 10 minutes or more, 1 hour or more, or even 2 hours or more. The reaction time is, for example, 24 hours or less, 12 hours or less, 7 hours or less, or even 2 hours or less.

[0112] In step (2), the reaction of product C with at least one selected from the group consisting of carbon dioxide, carbonates, and hydrogencarbonates may be carried out in the presence of a solvent, such as those described above for step (1).

[0113] In step (2), the solvent may be a non-polar solvent. It is presumed that the above-described configuration suppresses side reactions and improves the yield of isocyanate. For example, when a non-polar solvent is used, aggregation of compounds A with each other suppresses coordination of isocyanate with element M of compound A, thereby suppressing side reactions. Alternatively, the solvent may be a polar solvent.

[0114] In step (2), the solvent may include at least one selected from the group consisting of toluene, 1,4-dioxane, and acetonitrile. The solvent is preferably toluene. Alternatively, the solvent is preferably DMA.

[0115] The solvent in step (1) and the solvent in step (2) may be the same. The above-described configuration can improve the efficiency of the production method of the present invention.

[0116] In this manner, an isocyanate can be produced. In the method for producing an isocyanate according to the first embodiment of the present invention, for example, an isocyanate represented by the following general formula (I) can be produced: R-N=C=O (I) In general formula (I), R represents a hydrocarbon group which may have a substituent. That is, R is the same as that in general formula (B) above.

[0117] In step (2), compound A may be further obtained by reacting product C with at least one selected from the group consisting of carbon dioxide, carbonates, and hydrogencarbonates. That is, in step (2), product C may be reacted with at least one selected from the group consisting of carbon dioxide, carbonates, and hydrogencarbonates to obtain isocyanate and compound A. In this way, compound A, which is a starting material, can be recovered and reused, thereby increasing the productivity of isocyanate.

[0118] In step (2), a dehydrating agent may be further used, which can suppress decomposition of product C. Examples of the dehydrating agent include those described above in step (1).

[0119] In step (2), an additive may be further used. Examples of the additive include an antioxidant and a reaction accelerator. Specific examples of the additive include triethanolamine (TEA) and tris(2-hydroxyphenyl)amine. This can improve the yield of isocyanate. The additive may be added to a system containing product C before supplying at least one selected from the group consisting of carbon dioxide, carbonates, and bicarbonates. In step (2), for example, after adding the additive and stirring, product C may be reacted with at least one selected from the group consisting of carbon dioxide, carbonates, and bicarbonates. The stirring time is, for example, 5 to 30 minutes.

[0120] In the method for producing an isocyanate according to the first embodiment, the yield of the obtained isocyanate can be measured, for example, by subjecting the reaction solution in step (2) to gas chromatography. This allows the yield of the isocyanate to be measured without further treatment of the reaction solution.

[0121] In the method for producing an isocyanate according to the first embodiment of the present invention, step (1) and step (2) may be carried out consecutively. The method for producing an isocyanate according to the first embodiment of the present invention may include another step between step (1) and step (2).

[0122] An example of another step between step (1) and step (2) is a step of removing the solvent used in step (1). Examples of methods for removing the solvent include reduced pressure drying and vacuum drying. This allows different solvents to be used in step (1) and step (2).

[0123] The method for producing an isocyanate according to the first embodiment of the present invention does not need to include a step of removing the solvent used in step (1) between step (1) and step (2). For example, when the solvent used in step (1) and the solvent used in step (2) are the same, the step of removing the solvent used in step (1) can be omitted, and an isocyanate can be produced simply and easily.

[0124] Another example of a step between step (1) and step (2) is a step of removing substances that are not required in step (2). Examples of a method for removing substances include filtration. For example, after step (1), the dehydrating agent may be removed by filtration, and the filtrate may be used in step (2).

[0125] The method for producing an isocyanate according to the first embodiment of the present invention may include a step of isolating and purifying the product C between the step (1) and the step (2).

[0126] As described above, in the production method of this embodiment, isocyanate can be synthesized by performing steps (1) and (2) using compounds A and B. It is known that when a catalytic amount of compound A is reacted with compound B under a carbon dioxide atmosphere, a urea compound is synthesized instead of an isocyanate (T. Moriuchi et al. "Oxovanadium (V)-catalyzed amination of carbon dioxide under ambient pressure for the synthesis of ureas" RSC Adv., 2021, 11, 27121-27125).

[0127] [Method for Producing Isocyanate Derivative] The method for producing an isocyanate derivative according to the second embodiment of the present invention includes a step (3) of converting the isocyanate obtained by the method for producing an isocyanate according to the first embodiment into an isocyanate derivative.

[0128] Isocyanate derivatives are, for example, carbodiimides, isocyanurates, urethanes, ureas and urea derivatives.

[0129] In step (3), a carbodiimide is obtained, for example, by heat treating an isocyanate.

[0130] The temperature of the heat treatment is, for example, 50° C. or higher, 70° C. or higher, 100° C. or higher, or even 130° C. or higher.

[0131] The time for the heat treatment is not particularly limited, and is, for example, 1 hour or more, 2 hours or more, or even 5 hours or more.

[0132] Alternatively, in step (3), urethane can be obtained by adding an alcohol to the reaction mixture, for example, which may be isopropyl alcohol (IPA).

[0133] Steps (1), (2), and (3) may be performed in one pot, or only steps (1) and (2) may be performed in one pot. Step (3) may be performed in a vessel different from that in which steps (1) and (2) are performed. "Steps (1), (2), and (3) are performed in one pot" means that the reactions in steps (1), (2), and (3) are performed without including a step of isolating and purifying product C between steps (1) and (2) and without including a step of isolating and purifying isocyanate between steps (2) and (3). For example, in the method for producing an isocyanate derivative according to the second embodiment of the present invention, the reactions in steps (1), (2), and (3) are performed without an operation of distilling product C and isocyanate out of the system.

[0134] The solvent used in step (2) and the solvent used in step (3) may be the same.

[0135] The present invention will be described in more detail below, but the present invention is not limited thereto.

[0136] Example 1 [Step (1)] In a glove box, 0.60 mmol of compound A, 0.60 mmol of compound B, 0.60 mmol of base, and the solvent of step (1) were charged into a reaction vessel. As compound A, vanadium(V) oxytriisopropoxide (VO(O i 142 μL of Pr)3) was used. 69 μL of cyclohexylamine (Cy amine) was used as compound B. 14.4 mg of sodium hydride (NaH, 60% oil dispersion) was used as the base. 5 mL of dichloromethane was used as the solvent in step (1). These were reacted by stirring under a nitrogen atmosphere at 25°C for 24 hours.

[0137] After removing dichloromethane under reduced pressure, the mixture was dried in vacuum for 1.5 hours to obtain a yellow oily liquid in the reaction vessel.

[0138] [Step (2)] In a glove box, 1 mL of toluene was added as a solvent for step (2) to the yellow oily liquid in the reaction vessel, and the reaction vessel was sealed. The solution in the reaction vessel was frozen using liquid nitrogen. Then, the atmosphere in the reaction vessel was replaced with carbon dioxide using a balloon filled with carbon dioxide and a pump. With the balloon still connected to the reaction vessel, the reaction was carried out at 30°C for 2 hours. That is, steps (1) and (2) were carried out in one pot.

[0139] After the reaction was completed, the reaction solution in the reaction vessel was analyzed using gas chromatography. Using a calibration curve prepared in advance using a standard sample, the amount of substance X (mol) of the resulting isocyanate (cyclohexyl isocyanate in Example 1 and the following Examples 2 to 8, phenethyl isocyanate in Examples 9 and 10, and 1-adamantyl isocyanate in Examples 11 to 16) was calculated. The yield (%) of the isocyanate was calculated using the following formula (1) based on the amount of substance X of the resulting isocyanate and the amount of substance Y of compound B used in the reaction (0.60 mmol in Example 1 and the following Examples 2 to 8, 0.15 mmol in Examples 9 and 10, and 0.24 mmol in Examples 11 to 16). Isocyanate yield (%) = 100 × X / Y (1)

[0140] Example 2 An isocyanate was produced in the same manner as in Example 1, except that the solvent in step (2) was changed to 1,4-dioxane.

[0141] Example 3 An isocyanate was produced in the same manner as in Example 1, except that the solvent in step (2) was changed to acetonitrile.

[0142] Example 4 [Step (1)] In a glove box, 0.60 mmol of compound A, 0.60 mmol of compound B, 0.60 mmol of base, and the solvent of step (1) were charged into a reaction vessel. As compound A, vanadium(V) oxytriisopropoxide (VO(O i142 μL of Pr)3) was used. 69 μL of cyclohexylamine (Cyamine) was used as Compound B. 14.4 mg of sodium hydride (NaH, 60% oil dispersion) was used as the base. 5 mL of toluene was used as the solvent in Step (1). These were reacted by stirring under a nitrogen atmosphere at 25°C for 6 hours.

[0143] [Step (2)] After the reaction was completed, the solution in the reaction vessel was frozen using liquid nitrogen. Then, the atmosphere in the reaction vessel was replaced with carbon dioxide using a balloon filled with carbon dioxide and a pump. With the balloon still connected to the reaction vessel, the reaction was carried out at 30°C for 2 hours.

[0144] After the reaction was completed, the yield of isocyanate was calculated in the same manner as in Example 1.

[0145] Example 5 An isocyanate was produced in the same manner as in Example 4, except that the reaction temperature in step (1) was 70°C.

[0146] Example 6 An isocyanate was produced in the same manner as in Example 5, except that the reaction temperature in step (2) was 50°C.

[0147] Example 7 An isocyanate was produced in the same manner as in Example 5, except that the reaction temperature in step (2) was 70°C.

[0148] Example 8 [Step (1)] In a glove box, 0.60 mmol of compound A, 0.60 mmol of compound B, 0.60 mmol of base, and the solvent of step (1) were charged into a reaction vessel. As compound A, vanadium(V) oxytriisopropoxide (VO(O i 142 μL of Pr)3) was used. Cyclohexylamine (69 μL) was used as Compound B. 14.4 mg of sodium hydride (NaH, 60% oil dispersion) was used as the base. 5 mL of dichloromethane was used as the solvent in Step (1). These were reacted by stirring at 70°C for 2 hours under a nitrogen atmosphere.

[0149] [Step (2)] After the reaction was completed, the solution in the reaction vessel was cooled to 25° C. Then, a tube connected to a carbon dioxide cylinder was immersed in the solution, and carbon dioxide was bubbled through at a flow rate of 100 mL / min for 3 minutes.

[0150] After the reaction was completed, the yield of isocyanate was calculated for the reaction solution in the reaction vessel in the same manner as in Example 1.

[0151] Example 9 [Step (1)] In a glove box, 0.15 mmol of compound A, 0.15 mmol of compound B, 0.15 mmol of base, and the solvent of step (1) were charged into a reaction vessel. As compound A, vanadium(V) oxytriisopropoxide (VO(O i Pr)3) was used as Compound B. Phenethylamine was used as Compound B. Sodium hydride (NaH, 60% oil dispersion) was used as the base. 2 mL of toluene was used as the solvent in Step (1). These were reacted by stirring at 70°C for 2 hours under an argon atmosphere.

[0152] [Step (2)] After the reaction was completed, the reaction vessel was cooled to 25°C, and then 0.15 mmol of triethanolamine (TEA) was added to the reaction vessel in an argon atmosphere glove box. The TEA was diluted with a small amount of toluene. After the addition of TEA, the mixture was stirred at 25°C for 10 minutes. Liquid nitrogen was then used to freeze the solution in the reaction vessel. The atmosphere in the reaction vessel was then replaced with carbon dioxide using a balloon filled with carbon dioxide and a pump. The reaction was continued at 25°C for 10 minutes with the balloon still connected to the reaction vessel.

[0153] After the reaction was completed, the yield of isocyanate was calculated for the reaction solution in the reaction vessel in the same manner as in Example 1.

[0154] Example 10 [Step (1)] In a glove box, 0.15 mmol of compound A, 0.15 mmol of compound B, 0.15 mmol of base, a dehydrating agent, and the solvent of step (1) were charged into a reaction vessel. As compound A, vanadium(V) oxytriisopropoxide (VO(O iPr)3) was used. Phenethylamine was used as Compound B. Diazabicycloundecene (DBU) was used as the base. 2 g of molecular sieves (MS3A) was used as the dehydrating agent. 2 mL of dimethylacetamide (DMA) was used as the solvent in Step (1). These were reacted by stirring at 130°C for 2 hours under an argon atmosphere.

[0155] [Step (2)] After the reaction was completed, the solution in the reaction vessel was cooled to 25°C, and then 0.15 mmol of TEA was added to the reaction vessel in an argon atmosphere glove box. At this time, the TEA was diluted with a small amount of DMA. After the addition of TEA, the mixture was stirred at 25°C for 10 minutes. Then, the solution in the reaction vessel was frozen using liquid nitrogen. Then, the atmosphere in the reaction vessel was replaced with carbon dioxide using a balloon filled with carbon dioxide and a pump. With the balloon still connected to the reaction vessel, the reaction was carried out at 25°C for 10 minutes.

[0156] After the reaction was completed, the yield of isocyanate was calculated for the reaction solution in the reaction vessel in the same manner as in Example 1.

[0157] Example 11 [Step (1)] In a glove box, 0.24 mmol of compound A, 0.24 mmol of compound B, 0.24 mmol of base, 0.24 mmol of dehydrating agent, and the solvent of step (1) were charged into a reaction vessel. As compound A, vanadium(V) oxytriisopropoxide (VO(O i Pr)3) was used as compound B. 1-Adamantanamine (Ad amine) was used as compound B. 1,8-bis(dimethylamino)naphthalene (DMAN) was used as the base. N,N'-dicyclohexylcarbodiimide (DCC) was used as the dehydrating agent. 5 mL of dimethylacetamide (DMA) was used as the solvent in step (1). These were reacted by stirring at 130°C for 3 hours under an argon atmosphere.

[0158] [Step (2)] Next, the reaction vessel was cooled until the temperature inside the reaction vessel reached 30°C. Carbon dioxide was introduced into the reaction vessel up to 0.6 MPa and then released to 0.1 MPa, and this operation was repeated three times to replace the atmosphere inside the reaction tube with carbon dioxide. Thereafter, a pressurized atmosphere of carbon dioxide was created at 0.5 MPa. In this state, the reaction vessel was stirred and reacted at 30°C for 1 hour.

[0159] After the reaction was completed, the yield of isocyanate was calculated for the reaction solution in the reaction vessel in the same manner as in Example 1.

[0160] Example 12 An isocyanate was produced in the same manner as in Example 11, except that the amount of compound A was changed to 0.48 mmol.

[0161] Example 13 An isocyanate was produced in the same manner as in Example 12, except that Na3VO4 was used as compound A and the reaction time in step (1) was 24 hours.

[0162] Example 14 First, 450 mg of MgO particles (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 131-00282) were prepared. Next, these particles (carriers) were placed in a muffle furnace and fired at 700° C. for 5 hours.

[0163] Next, 50 mg of NH4VO3 was prepared as Compound A. NH4VO3 was mixed with 10 mL of distilled water, and the NH4VO3 was dissolved in the distilled water using ultrasound. Next, a support was immersed in the resulting solution, and the two were mixed to bring the NH4VO3 into contact with the support. The resulting mixture was dried by removing water using an evaporator. This produced NH4VO3 supported on a support. The mixture was further calcined in a muffle furnace at 500°C for 5 hours, and then ground in a mortar to obtain a composite of Compound A and the support.

[0164] An isocyanate was produced in the same manner as in Example 13, except that the above complex was used instead of Compound A. The amount of the complex was adjusted so that the amount of NHVO present in the reaction vessel was 0.48 mmol.

[0165] Example 15 An isocyanate was produced in the same manner as in Example 14, except that NaVO was used instead of NHVO. The amount of the complex was adjusted so that the amount of NaVO present in the reaction vessel was 0.48 mmol.

[0166] Example 16 [Step (1)] A cylindrical container (hereinafter referred to as "flow reactor") was filled with 0.23 mmol of compound A and 1,365 mg of molecular sieves (MS4A, Fujifilm Wako Pure Chemical Industries, Ltd., synthetic zeolite, A-4, spherical (8-12 mesh)). Next, a mixture of 0.24 mmol of compound B, 0.24 mmol of base, a dehydrating agent, and the solvent from step (1) was supplied to the flow reactor at a flow rate of 0.2 mL / min, and nitrogen was supplied at a flow rate of 2 mL / min. The flow reactor was heated so that the temperature inside the flow reactor reached 130°C. Na3VO4 was used as compound A. 1-Adamantanamine was used as compound B. DMAN was used as the base. 0.24 mmol of DCC was used as the dehydrating agent. 5 mL of DMA was used as the solvent for step (1).

[0167] [Step (2)] After all the liquid was discharged from the outlet, the nitrogen supply was stopped, and 2 mL of DMA was supplied at a flow rate of 0.2 mL / min, and CO was supplied at a flow rate of 2 mL / min to the flow reactor. The reaction solution discharged from the outlet of the flow reactor was collected, and the isocyanate yield was calculated in the same manner as in Example 1.

[0168] Table 1 shows the isocyanate yields for Examples 1 to 8. Table 2 shows the isocyanate yields for Examples 9 to 12. Table 3 shows the isocyanate yields for Examples 13 to 16.

[0169]

[0170]

[0171]

[0172] Isocyanates were successfully produced by the production methods of Examples 1 to 16. The results of Examples 1 to 3 show that, under the production conditions of the Examples, the highest yield was achieved when toluene was used as the solvent in step (2). Furthermore, the results of Examples 4 to 7 show that the yield tends to increase as the reaction temperature in step (2) decreases.

[0173] [Production of Isocyanate Derivative] (Example 17) [Step (1)] In a glove box, 0.60 mmol of Compound A, 0.60 mmol of Compound B, 1.8 mmol of a base, 1.8 mmol of a dehydrating agent, and the solvent of Step (1) were charged into a reaction vessel. As Compound A, vanadium(V) oxytriisopropoxide (VO(O i Pr)3) was used as Compound B. 4-Methoxyaniline was used as Compound B. DBU was used as the base. DCC was used as the dehydrating agent. 5 mL of DMA was used as the solvent in Step (1). These were reacted by stirring at 130°C for 24 hours under an argon atmosphere.

[0174] [Step (2)] After the reaction was completed, the solution in the reaction vessel was frozen using liquid nitrogen. The reaction vessel was then cooled until the temperature inside the reaction vessel reached 25°C. The atmosphere inside the reaction vessel was then replaced with carbon dioxide using a balloon filled with carbon dioxide and a pump. With the balloon still connected to the reaction vessel, the reaction was carried out at 25°C for 2 hours. After the reaction was completed, the production of isocyanate was confirmed.

[0175] [Step (3)] After the reaction was completed, 1 mL of isopropyl alcohol (IPA) was added to the reaction vessel, and the mixture was stirred at 25° C. for 10 minutes under an argon atmosphere to carry out the reaction.

[0176] After the reaction was completed, the solution was filtered and concentrated, and then analyzed using 1H-NMR. The amount of substance Z (mol) of the obtained isocyanate derivative (urethane) was calculated using a calibration curve prepared in advance using a standard sample. The yield (%) of urethane was calculated using the following formula (2) based on the amount of substance Z of the obtained urethane and the amount of substance Y of compound B used in the reaction. Yield (%) of urethane = 100 × Z / Y (2)

[0177] Example 18 Urethane was produced in the same manner as in Example 17, except that the dehydrating agent was changed to sodium sulfate.

[0178] Example 19 [Step (1)] In a glove box, 0.60 mmol of compound A, 0.60 mmol of compound B, 1.8 mmol of base, 0.60 mmol of dehydrating agent, and the solvent of step (1) were charged into a reaction vessel. As compound A, vanadium(V) oxytriisopropoxide (VO(O i Pr)3) was used as Compound B. 4-Methoxyaniline was used as Compound B. DBU was used as the base. Magnesium oxide was used as the dehydrating agent. 5 mL of DMA was used as the solvent in Step (1). These were reacted by stirring at 130°C for 24 hours under a nitrogen atmosphere.

[0179] [Step (2)] After the reaction was completed, the solution in the reaction vessel was frozen using liquid nitrogen. The reaction vessel was then cooled until the temperature inside the reaction vessel reached 25°C. The atmosphere inside the reaction vessel was then replaced with carbon dioxide using a balloon filled with carbon dioxide and a pump. With the balloon still connected to the reaction vessel, the reaction was carried out at 25°C for 2 hours. After the reaction was completed, the production of isocyanate was confirmed.

[0180] [Step (3)] After the reaction was completed, 1 mL of isopropyl alcohol (IPA) was added to the reaction vessel, and the mixture was stirred at 25° C. for 10 minutes under a nitrogen atmosphere to carry out the reaction.

[0181] After the reaction was completed, the urethane yield of the reaction solution in the reaction vessel was calculated in the same manner as in Example 17.

[0182] Example 20 [Step (1)] In a glove box, 0.24 mmol of compound A, 0.24 mmol of compound B, 0.72 mmol of base, 0.72 mmol of a dehydrating agent, an antioxidant, and the solvent of step (1) were charged into a reaction vessel. As compound A, vanadium(V) oxytriisopropoxide (VO(O iPr)3) was used as Compound B. 4-Methoxyaniline was used as the base. DBU was used as the base. Magnesium oxide was used as the dehydrating agent. 1.3 mg of dibutylhydroxytoluene (BHT) was used as the antioxidant. 5 mL of DMA was used as the solvent in Step (1). These were reacted by stirring at 130°C for 3 hours under an argon atmosphere.

[0183] [Step (2)] After the reaction was completed, the reaction vessel was cooled until the temperature inside the reaction vessel reached 30°C. Carbon dioxide was introduced into the reaction vessel up to 0.6 MPa and then released to 0.1 MPa, and this operation was repeated three times to replace the atmosphere inside the reaction tube with carbon dioxide. Thereafter, a pressurized atmosphere of carbon dioxide was created at 0.5 MPa. In this state, the reaction vessel was stirred and reacted at 30°C for 2 hours. After the reaction was completed, the production of isocyanate was confirmed.

[0184] [Step (3)] After the reaction was completed, the reaction vessel was cooled until the temperature inside the reaction vessel reached 25° C. 1 mL of isopropyl alcohol (IPA) was added to the reaction vessel, and the mixture was stirred at 25° C. for 10 minutes under an argon atmosphere to cause a reaction.

[0185] After the reaction was completed, the urethane yield of the reaction solution in the reaction vessel was calculated in the same manner as in Example 17.

[0186] Example 21 Urethane was produced in the same manner as in Example 20, except that the dehydrating agent was changed to 0.4 g of molecular sieves (MS3A) and the solvent was changed to toluene.

[0187] Example 22 Urethane was produced in the same manner as in Example 21, except that no antioxidant was used.

[0188] Example 23 [Step (1)] In a glove box, 1.2 mmol of compound A, 1.2 mmol of compound B, 3.6 mmol of base, and the solvent of step (1) were charged into a reaction vessel. As compound A, vanadium(V) oxytriisopropoxide (VO(O iPr)3) was used. 2,4,6-Trimethylaniline was used as Compound B. DBU was used as the base. 10 mL of toluene was used as the solvent in Step (1). The reaction vessel was equipped with 2 g of molecular sieves (MS3A) as a dehydrating agent, in a state where it was not in contact with the reaction solution so that the vapor generated by the reaction could be trapped. These were reacted by stirring at 125°C for 7 hours under an argon atmosphere.

[0189] [Step (2)] After the reaction was completed, the solution in the reaction vessel was frozen using liquid nitrogen. The reaction vessel was then cooled until the temperature inside the reaction vessel reached 25°C. The atmosphere inside the reaction vessel was then replaced with carbon dioxide using a balloon filled with carbon dioxide and a pump. With the balloon still connected to the reaction vessel, the reaction was carried out at 25°C for 2 hours. After the reaction was completed, the production of isocyanate was confirmed.

[0190] [Step (3)] After the reaction was completed, 2 mL of isopropyl alcohol (IPA) was added to the reaction vessel, and the mixture was stirred at 25° C. for 30 minutes under an argon atmosphere to carry out the reaction.

[0191] After the reaction was completed, the urethane yield of the reaction solution in the reaction vessel was calculated in the same manner as in Example 17.

[0192] Table 4 shows the yields of isocyanate derivatives (urethanes) in Examples 17 to 19. Table 5 shows the yields of urethanes in Examples 20 to 23.

[0193]

[0194]

[0195] According to the production methods of Examples 17 to 23, urethane, which is an isocyanate derivative, could be produced.

[0196] According to the method for producing an isocyanate of the present embodiment, for example, an isocyanate can be produced efficiently.

Claims

1. A method for producing an isocyanate, comprising: a step (1) of reacting a compound A having an element M-oxygen double bond with a compound B having an amino group to obtain a product C; and a step (2) of reacting the product C with at least one selected from the group consisting of carbon dioxide, carbonates, and hydrogencarbonates to obtain an isocyanate, wherein the element M is a metal element or P, and in the step (1), the ratio of the number of double bonds in the compound A to the number of moles of the amino groups in the compound B is 0.5 or more.

2. The method for producing an isocyanate according to claim 1, wherein said ratio is 1.0 or greater.

3. The method for producing an isocyanate according to claim 1, wherein the reaction temperature in step (2) is 100°C or lower.

4. The method for producing an isocyanate according to claim 1, wherein the steps (1) and (2) are carried out in one pot.

5. The method for producing an isocyanate according to claim 1, wherein the element M is V, Fe, Mo, Ta, Nb, Ti, W, or P.

6. The method for producing an isocyanate according to claim 1, wherein compound B is a primary amine.

7. The method for producing an isocyanate according to claim 1, wherein compound B is a compound represented by the following general formula (B): R-NX2 (B) In general formula (B), R represents a hydrocarbon group which may have a substituent, and two Xs each independently represent a hydrogen atom or a protecting group.

8. The method for producing an isocyanate according to claim 7, wherein the hydrocarbon group contains at least one selected from the group consisting of an aliphatic ring and an aromatic ring.

9. The method for producing an isocyanate according to claim 1, wherein the product C has an element M-nitrogen double bond.

10. The method for producing an isocyanate according to claim 1, wherein in the step (2), compound A is further obtained by the reaction.

11. The method for producing an isocyanate according to claim 1, wherein in step (1), the reaction is carried out under an inert atmosphere.

12. The method for producing an isocyanate according to claim 1, wherein in the step (2), the reaction is carried out in a solvent, and the solvent includes at least one selected from the group consisting of toluene, 1,4-dioxane, and acetonitrile.

13. The method for producing an isocyanate according to claim 1, wherein in step (1), the reaction is carried out in the presence of a base.

14. A method for producing an isocyanate derivative, comprising the step (3) of converting the isocyanate obtained by the method for producing an isocyanate according to any one of claims 1 to 13 into an isocyanate derivative.

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