Method for producing isocyanates

Abstract

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

Description

Technical Field

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

Background Art

[0002] Conventionally, the phosgene method in which an amine is reacted with phosgene has been used as the main industrial production method for isocyanates. However, the phosgene method has many problems from the viewpoints of environmental load and safety, such as phosgene being extremely toxic and hydrogen chloride being generated 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 a method of producing a carbamate from an amine, carbon dioxide and an alcohol through a multi-step reaction, and then producing an isocyanate through a thermal decomposition reaction of the carbamate. Patent Document 3 describes a method of producing a carbamate using an amine, an N-unsubstituted carbamate and an alcohol, and then producing an isocyanate through a thermal decomposition reaction of the carbamate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problem to be Solved by the Invention

[0005] The above-mentioned method for producing an isocyanate has complicated production steps.

[0006] Therefore, the present invention aims to provide a new method for producing isocyanates through a simple process. [Means for solving the problem]

[0007] The present invention Step (1) involves reacting compound A, which has an element M-oxygen double bond, with compound B, which has an amino group, to obtain product C. Step (2) involves reacting the aforementioned product C with at least one selected from the group consisting of carbon dioxide, carbonate, and bicarbonate to obtain an isocyanate. Includes, The element M is a metallic element or P. The present invention provides a method for producing an isocyanate, wherein in step (1) above, the ratio of the number of double bonds in compound A to the number of moles of amino groups in compound B is 0.5 or more. [Effects of the Invention]

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

[0009] A method for producing isocyanate according to the first aspect of the present invention is: Step (1) involves reacting compound A, which has an element M-oxygen double bond, with compound B, which has an amino group, to obtain product C. Step (2) involves reacting the aforementioned product C with at least one selected from the group consisting of carbon dioxide, carbonate, and bicarbonate to obtain an isocyanate. Includes, The element M is a metallic element or P. In step (1) above, the ratio of the number of double bonds in compound A to the number of moles of amino groups in compound B is 0.5 or more.

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

[0011] In the 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 the 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 performed in one pot.

[0013] In the 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 the 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 the 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 general formula (B). R-NX2(B) In general formula (B), R represents an optionally substituted hydrocarbon group, the two X each independently represent a hydrogen atom or a protecting group.

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

[0017] In the 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 is carried out under an inert atmosphere in the step (1).

[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 comprises 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, the reaction is carried out in the presence of a base in the step (1).

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

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

[0024] [Method for Producing Isocyanate] A method for producing isocyanate according to the first embodiment of the present invention comprises the steps of: (1) reacting compound A having an element M-oxygen double bond with compound B having an amino group to obtain product C; and (2) reacting product C obtained in step (1) with at least one selected from the group consisting of carbon dioxide, carbonates, and bicarbonates to obtain isocyanate. Element M is a metallic 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 (e.g., PFR: plug flow reactor, CSTR: continuous stirred tank reactor).

[0026] Steps (1) and (2) may be performed in a single pot.

[0027] In this specification, "steps (1) and (2) are carried out in one pot" means that the reactions of steps (1) and (2) are carried out without including a step to isolate and purify product C between steps (1) and (2). As long as there is no step to isolate and purify product C, steps (1) and (2) may be carried out in the same reaction vessel or in different reaction vessels. Carrying out steps (1) and (2) in one pot can improve the efficiency of the manufacturing process, for example. In this specification, "a step to isolate and purify product C" means a step to obtain a purity of product C of 95% or higher after removing the solvent.

[0028] Steps (1) and (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 continuously in the same reaction vessel.

[0029] The following provides a detailed explanation of each step.

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

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

[0032] Element M is either a metallic element or P. Element M may also be a metallic element.

[0033] Element M may be V, Fe, Mo, Ta, Nb, Ti, W, or P; or V, Fe, Mo, Ta, Nb, Ti, or W; or V, Fe, Mo, or Nb; or even V. In other words, compound A may have a vanadium-oxygen double bond.

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

[0035] Examples of ligands include optionally substituted hydrocarbon groups, optionally substituted oxy hydrocarbon groups, and halogens.

[0036] The number of carbon atoms in the hydrocarbon group is not particularly limited, as long as it is one or more. For example, the number of carbon atoms in the hydrocarbon group may be 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 alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and sec-butyl groups. Examples of alkenyl groups are vinyl and allyl groups. Examples of alkynyl groups are ethynyl groups.

[0038] Examples of substituents on hydrocarbon groups include halogens, amino groups, alkoxy groups, alkyl ester groups, carboxyl groups, and hydroxyl groups.

[0039] Examples of hydrocarbon groups included in the oxyhydrocarbon group are those described above. The oxyhydrocarbon group may also be an alkoxy group. Examples of alkoxy groups include the methoxy group, ethoxy group, and isopropoxy group. Examples of substituents on the oxyhydrocarbon group are those described above for hydrocarbon groups. An example of a substituted oxyhydrocarbon group is a group derived from triethanolamine (TEA).

[0040] Examples of halogens include fluorine, chlorine, bromine, and iodine, with chlorine being an example.

[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 as appropriate depending on the type of element M. The number of ligands may be one or more, for example, 1 to 5. The number of ligands may also 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). L n VO (A) In general formula (A), L represents an optionally substituted hydrocarbon group, an optionally substituted oxy hydrocarbon group, or a halogen, and n is a natural number between 1 and 5. When n is 2 or greater, the L groups are independent of each other. At least two of the L groups selected may be linked together.

[0044] Examples of optionally substituted hydrocarbon groups and optionally substituted oxy hydrocarbon groups are those described above.

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

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

[0047] Compound A is vanadium(V) oxytriisopropoxide (VO(O i It may also be Pr)3), VO(OEt)3, VO(OEt)Cl2, VOCl3, or VO(TEA).

[0048] Compound A is not limited to the complex described above. 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 V2O5, NH4VO3, TiO2, WO3, FeO, Fe2O3, NbO2, Nb2O5, and (NH4)2MoO4.

[0049] Compound B is a compound that contains an amino group.

[0050] Compound B is preferably a primary amine.

[0051] The number of amino groups in one molecule of compound B may be one or two or more.

[0052] Compound B may contain a cyclic structure. Compound B may contain one cyclic structure or two or more cyclic structures. The cyclic structure may or may not have a heteroatom. The cyclic structure may be an aliphatic ring or an aromatic ring. A compound B containing a cyclic structure with a heteroatom is, for example, tetrahydroflaminamine.

[0053] Aliphatic rings include, for example, cyclohexane, cyclopentane, and adamantane. Aromatic rings include, for example, benzene, naphthalene, and anthracene.

[0054] In compound B, the cyclic structure and nitrogen may or may not be directly bonded. In compound B, the aliphatic ring and nitrogen may be directly bonded. Compound B may also be a primary amine in which the amino group and the aliphatic ring are directly bonded.

[0055] Compound B may also be a compound represented by the following general formula (B). R-NX2(B) In formula (B), R represents an optionally substituted hydrocarbon group, and the two X's independently represent a hydrogen atom or a protecting group.

[0056] Examples of protecting groups include silyl protecting groups and carbamate protecting groups. Examples of silyl protecting groups 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 carbamate protecting groups include tert-butoxycarbonyl group (Boc group) and benzyloxycarbonyl group (Cbz group).

[0057] In general formula (B), X is preferably a hydrogen atom.

[0058] In general formula (B), the number of carbon atoms in the hydrocarbon group is not particularly limited, as long as it is 1 or more. 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.

[0059] In a preferred embodiment of the present invention, the hydrocarbon group in general formula (B) includes a cyclic structure. In general formula (B), the hydrocarbon group may include at least one selected from the group consisting of aliphatic rings and aromatic rings.

[0060] Hydrocarbon groups containing a cyclic structure include, for example, alicyclic hydrocarbon groups or aromatic hydrocarbon groups. In this specification, "alicyclic hydrocarbon group" means a hydrocarbon group that contains only an aliphatic ring as its cyclic structure and does not contain an aromatic ring, and includes both monocyclic and polycyclic alicyclic hydrocarbon groups. Here, an alicyclic hydrocarbon group does not need to consist only of an aliphatic ring, and may contain a chain-like structure as part of it. "Aromatic hydrocarbon group" means a hydrocarbon group that contains an aromatic ring as its cyclic structure. Here, an aromatic hydrocarbon group does not need to consist only of an aromatic ring, and may contain an aliphatic ring or a chain-like structure as part of it.

[0061] Alicyclic hydrocarbon groups include, for example, cyclohexyl groups, cyclopentyl groups, and adamantyl groups. The alicyclic hydrocarbon group is preferably a cyclohexyl group.

[0062] Aromatic cyclic hydrocarbon groups may include a benzene ring. Aromatic cyclic hydrocarbon groups may include, for example, a phenyl group, a methylphenyl group, a methoxyphenyl group, a benzyl group, and the like.

[0063] In another preferred embodiment of the present invention, in general formula (B), 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.

[0064] Alkyl groups include, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, sec-butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. Alkenyl groups include, for example, vinyl and allyl groups. Alkynyl groups include, for example, ethynyl groups.

[0065] The substituent may be any substituent; for example, those described above for compound A are examples.

[0066] Examples of compound B include ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, cyclohexylamine, cyclopentylamine, 2-phenylmethylamine, 2-phenylethylamine, 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, 4,4'-methylenedianiline, and the like. If structural isomers exist for the compounds exemplified above, those structural isomers are also included in the examples. Compound B is preferably cyclohexylamine.

[0067] In the method for producing isocyanates according to the first embodiment, various types of isocyanates can be produced by selecting compound B.

[0068] 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 elemental 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 elemental M-oxygen double bonds in compound A to the number of moles of amino groups in compound B in step (1)" is the value calculated by the formula: (value obtained by multiplying the number of elemental M-oxygen double bonds contained in one molecule of compound A by the amount of substance of compound A used in step (1)) / (value obtained by multiplying the number of amino groups contained in one molecule of compound B by the amount of substance of compound B used in step (1)).

[0069] In step (1), the ratio of the number of elemental M-oxygen double bonds in compound A to the number of moles of amino groups in 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 in compound A to the number of moles of amino groups in compound B may be 10.0 or less, 7.0 or less, 5.0 or less, 3.0 or less, and even 2.0 or less. In step (1), the ratio of the number of elemental M-oxygen double bonds in compound A to the number of moles of amino groups in 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 in compound A to the number of moles of amino groups in compound B may be 1.0.

[0070] 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, and 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.

[0071] Product C, obtained by reacting compound A and compound B, may contain an element M-nitrogen double bond. Element M in product C originates from compound A.

[0072] The number of elemental M-nitrogen double bonds in one molecule of product C may be one or more, for example, 1 to 5. Preferably, the number of elemental M-nitrogen double bonds in one molecule of product C is 1. However, in some cases, the number of elemental M-nitrogen double bonds in one molecule of product C may be two or more.

[0073] 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.

[0074] In product C, the cyclic structure and nitrogen may or may not be directly bonded. In product C, the aliphatic ring and nitrogen may be directly bonded.

[0075] In a preferred embodiment of the present invention, product C may have a ligand that coordinates to element M.

[0076] Examples of ligands include those mentioned above for compound A.

[0077] Product C may be a compound represented by the following general formula (C). L n VNR (C) In general formula (C), R represents an optionally substituted hydrocarbon group, L represents an optionally substituted hydrocarbon group, an optionally substituted oxy hydrocarbon group, or a halogen, and n is a natural number from 1 to 5. When n is 2 or greater, the L groups are independent of each other. At least two selected from the L groups may be linked together. 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.

[0078] Product C is not limited to those described above. In another preferred embodiment of the present invention, product C may not have a ligand that coordinates to element M.

[0079] In step (1), the reaction between compound A and compound B may be carried out under an inert atmosphere. The inert atmosphere may be a nitrogen atmosphere.

[0080] 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 sodium hydride and hydride salts, 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 individually or in combination. Preferably, the base is sodium hydride, N,N-diisopropylethylamine, diazabicycloundecene, or 1,8-bis(dimethylamino)naphthalene.

[0081] The base may be one that can function as a dehydrating agent. For example, if sodium hydride is used as the base in step (1), it will be converted to sodium hydroxide in the reaction and can be used as a dehydrating agent as described later.

[0082] 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, and even 1.0 or more. Note that the ratio of the amount of base used to the number of moles of amino groups in compound B is given by the amount of base (mol) / (number of amino groups contained in one molecule of compound B × amount of compound B) (mol).

[0083] In step (1), the reaction temperature is, for example, 150°C or lower, 120°C or lower, 100°C or lower, 90°C or lower, 80°C or lower, preferably 70°C or lower. The reaction temperature is, for example, 20°C or higher, 25°C or higher, and even 30°C or higher. The reaction temperature may be 20°C or higher and 70°C or lower. In this specification, reaction temperature means the temperature of the reaction system.

[0084] In step (1), the reaction time is not particularly limited. From the viewpoint of obtaining sufficient product C, it can be, for example, 10 minutes or more, 1 hour or more, or even 2 hours or more. Alternatively, the reaction time can be, for example, 48 hours or less, 24 hours or less, 12 hours or less, 6 hours or less, or even 2 hours or less.

[0085] In step (1), the reaction between compound A and compound B may be carried out under solvent conditions. The solvent can be a polar solvent or a nonpolar solvent. In this specification, a nonpolar solvent is a solvent with a dielectric constant of 8.0 or less at 25°C. In this specification, a polar solvent is a solvent with a dielectric constant greater than 8.0 at 25°C.

[0086] Examples of nonpolar solvents include toluene, benzene, xylene, hexane, 1,4-dioxane, tetrahydrofuran, ethyl acetate, cyclopentyl methyl ether, and mixtures thereof. Toluene is preferred as the nonpolar solvent.

[0087] Examples of polar solvents include acetonitrile, dimethyl sulfoxide, dichloromethane, propylene carbonate, methanol, ethanol, dimethylacetamide, and mixtures thereof. The polar solvent is preferably acetonitrile or dichloromethane.

[0088] From an efficiency standpoint, the solvent is preferably a nonpolar solvent. This allows the manufacturing method of the present invention to be made more efficient by using the same solvent in the subsequent step (2).

[0089] In step (1), a dehydrating agent may be used further. This can suppress the decomposition of product C. As the dehydrating agent, known dehydrating agents such as molecular sieves can be used. In addition, as mentioned above, a base that can also function as a dehydrating agent may be used.

[0090] <Process (2)> As described above, in step (2), product C obtained in step (1) is reacted with at least one selected from the group consisting of carbon dioxide, carbonates, and bicarbonates to obtain an isocyanate.

[0091] The ratio of the total amount of carbon dioxide, carbonate, and bicarbonate to the amount of compound B, which is the starting material, may be 1 or more. It is preferable that the amount of carbon dioxide, carbonate, and bicarbonate is in excess of compound B, which is the 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.

[0092] Examples of carbonates and bicarbonates include alkali metal and alkaline earth metal carbonates or bicarbonates. Examples of bicarbonates include sodium bicarbonate and potassium bicarbonate. Examples of carbonates include sodium carbonate, potassium carbonate, sodium potassium carbonate, and sodium sesquicarbonate.

[0093] 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.

[0094] In step (2), product C may be reacted with carbon dioxide to obtain an isocyanate.

[0095] Step (2) may be carried out in an atmosphere containing carbon dioxide, or in a carbon dioxide atmosphere.

[0096] The atmosphere containing carbon dioxide may be obtained by replacing the entire atmosphere in the reaction vessel containing product C obtained in step (1) with carbon dioxide, or by bubbling carbon dioxide into the solution containing product C obtained in step (1). That is, the reaction between product C and carbon dioxide in step (2) may be carried out after replacing the atmosphere in the reaction vessel containing product C obtained in step (1) with carbon dioxide, or it may be carried out while bubbling carbon dioxide into the solution containing product C obtained in step (1).

[0097] In step (2), the reaction temperature may be, for example, less than 130°C or 100°C or less. The reaction temperature may be, 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 may be, for example, 20°C or more, and even more preferably 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. With the above configuration, the yield of isocyanate can be improved.

[0098] In step (2), the reaction time is not particularly limited. The reaction time may be, for example, 3 minutes or more, 10 minutes or more, 1 hour or more, or even 2 hours or more. Alternatively, the reaction time may be 24 hours or less, 12 hours or less, 7 hours or less, or even 2 hours or less.

[0099] In step (2), the reaction between product C and at least one selected from the group consisting of carbon dioxide, carbonates, and bicarbonates may be carried out under a solvent. Examples of solvents include those described above for step (1).

[0100] In step (2), the solvent may be a nonpolar solvent. With the above configuration, it is presumed that side reactions can be suppressed and the yield of isocyanate can be improved. For example, when a nonpolar solvent is used, the aggregation of compound A members suppresses the coordination of isocyanate to element M of compound A, and thus it is presumed that side reactions are suppressed.

[0101] 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.

[0102] The solvent in step (1) and the solvent in step (2) may be the same. With the above configuration, the manufacturing method of the present invention can be made more efficient.

[0103] As described above, isocyanates can be produced. In the method for producing isocyanates according to the first embodiment of the present invention, for example, an isocyanate represented by the following general formula (I) can be produced. RN=C=O (I) In general formula (I), R represents a hydrocarbon group which may have substituents. That is, R is the same as that in general formula (B) above.

[0104] In step (2), compound A may be obtained by reacting product C with at least one selected from the group consisting of carbon dioxide, carbonate, and bicarbonate. That is, in step (2), isocyanate and compound A may be obtained by reacting product C with at least one selected from the group consisting of carbon dioxide, carbonate, and bicarbonate. This allows for the recovery and reuse of compound A, which is the starting material, thereby increasing the productivity of isocyanate.

[0105] In step (2), a dehydrating agent may be used further. This can suppress the decomposition of product C. Examples of dehydrating agents include those described above in step (1).

[0106] In the method for producing 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 makes it possible to measure the yield of isocyanate without further processing of the reaction solution.

[0107] In the method for producing isocyanate according to the first embodiment of the present invention, steps (1) and (2) may be carried out sequentially. In the method for producing isocyanate according to the first embodiment of the present invention, other steps may be included between steps (1) and (2).

[0108] An example of another step between step (1) and step (2) is the step of removing the solvent used in step (1). Methods for removing the solvent include, for example, vacuum drying or decompression drying. This allows for the use of different solvents in step (1) and step (2).

[0109] The method for producing isocyanate according to the first embodiment of the present invention does not necessarily include a step to remove the solvent used in step (1) between step (1) and step (2). For example, if the solvent used in step (1) and the solvent used in step (2) are the same, the step to remove the solvent used in step (1) can be omitted, and isocyanate can be produced simply.

[0110] Another example of a process between process (1) and process (2) is a process to remove substances that are not needed in process (2). One method of removal is filtration. For example, after process (1), the dehydrating agent may be removed by filtration and the filtrate may be used in process (2).

[0111] The method for producing isocyanate according to the first embodiment of the present invention may include a step of isolating and purifying product C between steps (1) and (2).

[0112] As described above, in the manufacturing method of this embodiment, isocyanates 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, urea compounds are synthesized instead of isocyanates (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).

[0113] [Method for producing isocyanate derivatives] 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.

[0114] Examples of isocyanate derivatives include carbodiimides, isocyanurates, urethanes, ureas, and urea derivatives.

[0115] In step (3), for example, carbodiimide is obtained by heat treatment of isocyanate.

[0116] The heat treatment temperatures are, for example, 50°C or higher, 70°C or higher, 100°C or higher, and even 130°C or higher.

[0117] The heating time is not particularly limited and can be, for example, 1 hour or more, 2 hours or more, or even 5 hours or more.

[0118] Steps (1), (2), and (3) may be carried out in a one-pot process, or only steps (1) and (2) may be carried out in a one-pot process. Step (3) may be carried out in a different container from steps (1) and (2). "Steps (1), (2), and (3) are carried out in a one-pot process" means that the reactions of steps (1), (2), and (3) are carried out without including a step to isolate and purify product C between steps (1) and (2), and without including a step to isolate and purify isocyanate between steps (2) and (3). For example, the method for producing an isocyanate derivative according to the second embodiment of the present invention carries out the reactions of steps (1), (2), and (3) without going through the operation of distilling off product C and isocyanate from the system.

[0119] The solvent used in step (2) and the solvent used in step (3) may be the same. [Examples]

[0120] The present invention will be described in more detail below, but is not limited thereto.

[0121] (Example 1) [Process (1)] Inside the glove box, 0.60 mmol of compound A, 0.60 mmol of compound B, 0.60 mmol of base, and the solvent from step (1) were added to the reaction vessel. Compound A was vanadium(V) oxytriisopropoxide (VO(O i Pr)3) 142 μL was used. As compound B, cyclohexylamine (Cyamine) 69 μL was used. As the base, sodium hydride (NaH, 60% oil dispersion) 14.4 mg was used. As the solvent for step (1), dichloromethane 5 mL was used. These were reacted by stirring at 25°C under a nitrogen atmosphere for 24 hours.

[0122] After removing the dichloromethane under reduced pressure, the mixture was vacuum-dried for 1.5 hours. Following vacuum drying, a yellow, oily liquid was obtained in the reaction vessel.

[0123] [Process (2)] Inside the glove box, 1 mL of toluene was added to the yellow oily liquid in the reaction vessel as the solvent for step (2), and the reaction vessel was sealed. The solution in the reaction vessel was frozen using liquid nitrogen. Then, the atmosphere inside the reaction vessel was replaced with carbon dioxide using a balloon and pump filled with carbon dioxide. The reaction was carried out at 30°C for 2 hours with the balloon still connected to the reaction vessel. In other words, steps (1) and (2) were carried out in a single pot.

[0124] After the reaction was complete, the reaction solution in the reaction vessel was analyzed using gas chromatography. Using a calibration curve prepared in advance with a standard sample, the amount of substance X (mol) of the obtained isocyanate (cyclohexyl isocyanate in Example 1 and Examples 2-8 below) was calculated. Based on the amount of substance X of the obtained isocyanate and the amount of substance Y of compound B used in the reaction (0.60 mmol in Example 1 and Examples 2-8 below), the yield (%) of the isocyanate was calculated using the following formula (1). Yield of isocyanate (%) = 100 × X / Y (1)

[0125] (Example 2) An isocyanate was produced by performing the same procedure as in Example 1, except that the solvent in step (2) was changed to 1,4-dioxane.

[0126] (Example 3) The same procedure as in Example 1 was followed to produce isocyanate, except that the solvent in step (2) was changed to acetonitrile.

[0127] (Example 4) [Process (1)] Inside the glove box, 0.60 mmol of compound A, 0.60 mmol of compound B, 0.60 mmol of base, and the solvent from step (1) were added to the reaction vessel. Compound A was vanadium(V) oxytriisopropoxide (VO(O iPr)3) 142 μL was used. As compound B, cyclohexylamine (Cyamine) 69 μL was used. As the base, sodium hydride (NaH, 60% oil dispersion) 14.4 mg was used. Toluene 5 mL was used as the solvent for step (1). These were reacted by stirring at 25°C under a nitrogen atmosphere for 6 hours.

[0128] [Process (2)] After the above reaction was complete, 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. The reaction was carried out at 30°C for 2 hours with the balloon still connected to the reaction vessel.

[0129] After the reaction was complete, the yield of isocyanate was calculated in the same manner as in Example 1.

[0130] (Example 5) An isocyanate was produced by following the same procedure as in Example 4, except that the reaction temperature in step (1) was set to 70°C.

[0131] (Example 6) An isocyanate was produced by following the same procedure as in Example 5, except that the reaction temperature in step (2) was set to 50°C.

[0132] (Example 7) The same procedure as in Example 5 was followed to produce isocyanate, except that the reaction temperature in step (2) was set to 70°C.

[0133] (Example 8) [Process (1)] Inside the glove box, 0.60 mmol of compound A, 0.60 mmol of compound B, 0.60 mmol of base, and the solvent from step (1) were added to the reaction vessel. Compound A was vanadium(V) oxytriisopropoxide (VO(O iPr)3) 142 μL was used. As compound B, cyclohexylamine (69 μL) was used. As the base, 14.4 mg of sodium hydride (NaH, 60% oil dispersion) was used. As the solvent for step (1), 5 mL of dichloromethane was used. These were reacted by stirring at 70°C for 2 hours under a nitrogen atmosphere.

[0134] [Process (2)] After the above reaction was complete, 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 it at a flow rate of 100 mL / min for 3 minutes.

[0135] After the reaction was complete, the yield of isocyanate was calculated from the reaction solution in the reaction vessel in the same manner as in Example 1.

[0136] Table 1 shows the yields of isocyanates from Examples 1 to 8.

[0137] [Table 1]

[0138] Isocyanates could be produced using the manufacturing methods of Examples 1 to 8. From the results of Examples 1 to 3, it can be seen that the yield is highest when the solvent in step (2) is toluene under the manufacturing conditions of the examples. Furthermore, from the results of Examples 4 to 7, it can be seen that the yield tends to increase as the reaction temperature in step (2) decreases. [Industrial applicability]

[0139] According to the isocyanate production method of this embodiment, for example, isocyanates can be produced efficiently.

Claims

1. Step (1) involves reacting compound A, which has an element M-oxygen double bond, with compound B, which has an amino group, to obtain product C. Step (2) involves reacting the aforementioned product C with at least one selected from the group consisting of carbon dioxide, carbonate, and bicarbonate to obtain an isocyanate. Includes, The element M is a metallic element or P. A method for producing an isocyanate, wherein in step (1) above, the ratio of the number of double bonds in compound A to the number of moles of amino groups in compound B is 0.5 or more.

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

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

4. The method for producing an isocyanate according to claim 1, wherein steps (1) and (2) are performed in a single 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 the compound B is a compound represented by general formula (B). R-NX 2 (B) In general formula (B), R represents a hydrocarbon group which may have substituents, The two X's independently represent either a hydrogen atom or a protecting group.

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

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 step (2) above, 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. In step (2) above, the reaction is carried out under solvent conditions. The method for producing an isocyanate according to claim 1, wherein the solvent comprises 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 step (3) of converting an isocyanate obtained by the method for producing an isocyanate according to any one of claims 1 to 13 into an isocyanate derivative, A method for producing isocyanate derivatives, including [the specified substance].

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