JPH0662544B2 - Method for producing aromatic urethane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an aromatic urethane.

[Prior Art and its Problems] Various methods for producing an aromatic urethane have been proposed in the past. These methods are a method using an aromatic nitro compound as a starting material and a method using an aromatic primary amine as a starting material. It can be roughly divided.

A method using an aromatic nitro compound as a starting material is a method in which an aromatic nitro compound (for example, nitrobenzene), a compound containing a hydroxyl group (for example, alcohols), and carbon monoxide are used.
This is a method of producing an aromatic urethane by a reductive carbonylation reaction by reacting in the presence of a catalyst mainly composed of a platinum group metal compound such as palladium and rhodium. This method is described, for example, in JP-A-51-98240 and JP-A-54-223.
No. 39, Japanese Patent Publication No. 43-23939, etc.

In addition, a method using an aromatic primary amine as a starting material is a method in which an aromatic primary amine (eg, aniline) and an organic compound having a hydroxyl group (eg, alcohols) are mixed with each other in the presence of an oxidizing agent such as oxygen or an organic nitro compound. It is a method of producing an aromatic urethane by an oxidative carbonylation reaction by reacting carbon oxide with a catalyst mainly containing a platinum group metal compound such as palladium and rhodium. This method, for example,
JP-A-55-124050, JP-A-55-120551
And JP-A-59-172451.

In this case, in any of the methods, since the platinum group metal compound which is the main component of the catalyst alone has a low urethane synthesis activity, a halogen compound such as iron chloride, iron oxychloride, vanadium oxychloride, potassium iodide or the like is used as a cocatalyst. Are dissolved in the reaction system. However, the halogen compound has a large amount of precipitation in reaction vessels, pipes, valves and the like and is highly corrosive to metal materials. Therefore, an expensive metal material excellent in corrosion resistance must be used.

Further, when the platinum group metal compound which is the main catalyst is used by dissolving it in the reaction solution and when it is used as a solid in the metal state, a part of the platinum group metal should not be eluted in the reaction solution. I can't. Therefore, after the reaction is completed, a complicated operation and a large cost are required to recover the platinum group metal compound from the reaction solution.

An organic compound having a hydroxyl group, which is a reaction raw material, is used as a reaction solvent. Aromatic urethane has a very high solubility in the organic compound having a hydroxyl group. Therefore, when the aromatic urethane is separated and recovered from the solution after the reaction by crystallization, it is necessary to cool the solution to an extremely low temperature of several tens of degrees below zero, or to concentrate the solution and then cool it to precipitate crystals. Becomes Moreover, even if this operation is performed, it is difficult to separate and recover the aromatic urethane and the catalyst component dissolved in the solution. Another method of recovering the aromatic urethane may be a method by distillation. In this case, however, the aromatic urethane has to be distilled off in order to recover the dissolved catalyst as a distillation residue. However, aromatic urethane is a high-boiling compound,
Distillation must be carried out in a medium temperature range of 100 to 150 ° C. under a high vacuum of about mmHg.

As described above, aromatic urethane is separated and recovered from the solution,
Further, it is difficult to recover the catalyst and reuse it by crystallization or distillation.

Furthermore, when an aromatic nitro compound is used as a starting material, an aromatic amine and an N, N'-disubstituted urea are used, and when an aromatic primary amine is used as a starting material, an N, N'-disubstituted urea is used. There is a drawback that the yield of aromatic urethane decreases as a by-product.

In addition, a method of producing an aromatic urethane by a two-step reaction is
Japanese Patent Application Laid-Open No. 62-111958, Japanese Patent Application No. 63-012018
Has been proposed to. However, JP-A-62-111958
In such a case, the ruthenium complex catalyst may precipitate during the first-step reaction, and may go out of the system together with crystals of the product urea compound. Japanese Patent Application No. Sho 63-01201
In No. 8, the addition solvent suppresses the precipitation of the catalyst during the reaction in the first step, but the addition of the solvent does not increase the reaction rate.

[PROBLEMS TO BE SOLVED BY THE INVENTION] The present invention has been made in view of the above circumstances, and an object thereof is to use an aromatic urethane which does not use a halogen compound as a cocatalyst and solves various problems caused by this use. The present invention provides a method of manufacturing the same. Further, the object of the present invention is to produce an aromatic urethane by a two-step reaction between the production of ureas by a carbonylation reaction and the reaction of the produced ureas and a compound having a hydroxyl group,
An object of the present invention is to provide a method for producing an aromatic urethane, which improves the yield and selectivity as a whole and facilitates the recovery of the catalyst and the produced aromatic urethane. A further object of the present invention is to further increase the reaction rate by using an amide compound as a part or all of the solvent in the urea production step by the carbonylation reaction carried out in the first step, and to carry out efficient catalyst recycling. As a result, a method for efficiently producing an aromatic urethane is to be obtained.

[Means for Solving the Problem] The present invention is a method for producing an aromatic urethane including three steps.

In the first step, an aromatic nitro compound, an aromatic primary amine and carbon monoxide are reacted with each other using a catalyst mainly composed of a platinum group metal compound to give an N, N′-disubstituted urea. To generate. Here, the reaction rate is increased by using an amide compound as a part or all of the solvent. Then, the produced N, N'-disubstituted urea is separated and recovered from the reaction solution.

In the second step, the N, N′-disubstituted urea obtained in the first step is reacted with an organic compound having a hydroxyl group to produce an aromatic primary amine and an aromatic urethane, and then, The aromatic primary amine is separated to obtain an aromatic urethane.

In the third step, the separated primary amine is recycled to the first step.

Next, the invention will be specifically described.

First, in the first step, an aromatic primary amine, an aromatic nitro compound, and carbon monoxide are used, a catalyst mainly containing a platinum group metal compound is used, and an amide compound is used as a part or all of the solvent. To react. This reaction is considered to proceed according to the following reaction formula.

Aromatic primary amines include anilines, aminonaphthalenes, aminoanthracenes, aminobiphenyls, and the like, and specific compounds include aniline, o-, and m.
-And p-toluidine, o-, m- and p-chloroaniline, α and β-naphthylamine, 2-methyl-1-aminonaphthalene, diaminobenzene isomers, triaminobenzene isomers, aminotoluene isomers , Diaminotoluene isomers, aminonaphthalene isomers, and mixtures thereof.

Examples of the aromatic nitro compound include nitrobenzenes, nitronaphthalenes, nitroanthracenes, nitrobiphenyls, or at least one hydrogen atom as another substituent, for example, a halogen atom, a cyano group, an alicyclic group, an aromatic group, an alkyl group. , An alkoxy group, a sulfone group, a sulfoxide group, a carbonyl group, an ester group, an amide group and the like are substituted, and specific compounds include nitrobenzene, o-, m- and p-nitrotoluene, o- Nitro-p-xylene, 2-methyl-1
-Nitronaphthalene, dinitrobenzene isomers, trinitrobenzene isomers, dinitrotoluene isomers,
Examples include nitronaphthalene isomers, o-, m- and p-chloronitrobenzene, 1-bromo-4-nitrobenzene, and mixtures thereof. However, it is preferable to use a nitro compound corresponding to the aromatic primary amine.

Examples of the amide compound to be added include amides, specifically N, N′-dimethylacetamide, N, N′-dimethylformamide, N-methyl-2-pyrrolidinone, and the like. A substituted urea compound represented by (R ¹ , R ² , R ³ , and R ⁴ are alkylene containing 3 to 5 carbon atoms linked by an alkyl group and a carbon chain), specifically, N, N, N ′ , N′-tetramethylurea, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyltetrahydro-2 (1H) -pyrimidinone and the like, And a phosphine-amide compound represented by the formula (wherein R ¹ and R ² are alkyl groups having 1 to 5 carbon atoms, and n is 1 to 5), And a phosphine-amide compound represented by the formula (wherein R ¹ and R ² are alkyl groups having 1 to 6 carbon atoms, and alkylene having 3 to 5 carbon atoms linked by a carbon chain), and isomers thereof,
Further, a mixture of these and the like can be mentioned.

The amide compound of the present invention has the function of improving the reaction rate by using as a solvent, and further has the function of stabilizing the catalyst and allowing the catalyst to exist in the filtrate without being precipitated. If there is, it is more suitable.

Oxygen-containing organic sulfur compounds such as sulfoxides are represented by the general formula R ¹ —SO—R ² or R ¹ —SO ₂ —R ² . Where R ¹ and R ² are alkyl, alkoxy substituted or phenyl substituted containing 1 to 8 carbon atoms, and further R
¹ and R ² are alkylene containing 4 to 7 carbon atoms linked by a carbon chain. Specifically, dimethyl sulfoxide,
Examples include diphenyl sulfoxide and sulfolane.

In the method of the present invention, only the amide compound to be added can be used as a solvent as it is, but it is also preferable to perform it in a mixed solution with another suitable solvent. Examples of such other solvent include aromatic hydrocarbons such as benzene, toluene, xylene, and mesitylene, halogenated aliphatic hydrocarbons such as chlorohexane and chlorocyclohexane, chlorobenzene, bromobenzene, dichlorobenzene, and trichlorobenzene. Halogenated aromatic hydrocarbons such as chlorobenzene are used.

Carbon monoxide may be pure or may contain nitrogen, argon, helium, carbon dioxide gas, halogenated hydrocarbon and the like.

The compound containing a platinum group metal is a compound such as ruthenium, rhodium, palladium, a platinum group element such as platinum, carbon monoxide, a ligand of phosphines, or an organometallic compound having an organic group, Those containing no halogen element are preferred. Specifically, Ru ₃ (CO) ₁₂ , H ₄ R
u ₄ (CO) ₁₂ , [Ru ₂ (CO) ₄ (HCOO) ₂ ] n, Ru (CO) ₃ (dppe), Ru (CO) ₃ (PP
h ₃ ) ₂ , Ru (acac) _{3 and} other ruthenium complex compounds, Rh ₆ (CO) ₁₆ , RhH (CO) (PPh ₃ ) ₃ ,
Rh (acac) (CO) (PPh ₃ ), Rh (aca
c) Rhodium complex compounds such as (CO) ₂ and Rh (acac) ₃ are listed. However, PPh ₃ is triphenylphosphine, dpppe is diphenylphosphinoethane, and acac is acetylacetonate.

In addition to these complex compounds, it is also possible to use an inorganic platinum group metal compound that changes into an active species in the reaction system. Specific examples thereof include RuO ₂ · nH ₂ O, Ru-black, Ru carbon and the like. These compounds are
It is considered that in the reaction system, it is converted into a carbonyl complex to give an active species.

Further, cobalt, iron, rhodium, palladium and the like can be used in combination with these platinum group metals.

The reaction temperature is usually 30 to 300 ° C., preferably 120 to
It is carried out in the temperature range of 200 ° C. Reaction pressure is 1 to 500
kg / cm ^2, preferably in the range of 10~150kg / cm ^2, the reaction time varies depending on other conditions a few hours normally several minutes.

The N, N'-disubstituted urea obtained by the method of the present invention has a low solubility in the solvent and the raw material aromatic amine or aromatic nitro compound. For this reason, the N, N′-disubstituted urea that has formed precipitates as crystals only by cooling the solution after the reaction to about room temperature. Therefore, by filtering this solution, N, N 'disubstituted urea can be efficiently obtained as a solid. After the reaction, when cooled to room temperature and crystallized, the components other than the di-substituted urea in the reaction mixture can be easily separated by washing with a solvent such as toluene or benzene, and only the di-substituted urea can be taken out alone. it can.

Next, in the second step, the obtained N, N'-disubstituted urea is reacted with an organic compound having a hydroxyl group as in the following formula to produce an aromatic primary amine and an aromatic urethane.

As the organic compound having a hydroxyl group, monohydric alcohols,
There are monohydric phenols and the like, and specifically, monohydric alcohols such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and t-butyl, and phenol, chlorophenol, methyl, ethyl,
Examples thereof include alkylphenols having an alkyl group such as n-propyl and isopropyl.

The reaction temperature is usually 80 to 300 ° C., preferably 120 to 300 ° C.
It is preferable to carry out in the temperature range of 200 ° C. The pressure is set to an organic compound containing a hydroxyl group which is usually used, or an autogenous pressure at a reaction temperature of a solvent. And this reaction can be performed without the use of a catalyst.

After the completion of this reaction, a distillation operation is performed to recover aromatic urethane as a distillation residue, while the aromatic primary amine is recovered by distillation. This aromatic primary amine is reused in the first stage N, N'-disubstituted urea formation reaction.

When the first step (reaction formula (1)) and the second step (reaction formula (2)) are continuously performed as described above, the aromatic primary amine does not formally change, Only the aromatic nitro compound participates in the reaction, and as a whole, the aromatic nitro compound is reductively converted into aromatic urethane, which is more economical than using an aromatic primary amine as a starting material.

According to the present invention, the N, N′-disubstituted urea produced in the first-step reaction has a solubility in the solvent and the raw material aromatic amine or aromatic nitro compound. Since it is small, it can be easily crystallized by cooling it to room temperature, and the N, N'-disubstituted urea can be efficiently recovered by filtration. Moreover, since the reaction rate is increased by using the amide compound as the solvent, the productivity can be improved.

Further, in the present invention, since it is not necessary to use a halogen compound, corrosion of equipment materials is extremely small, and it is not necessary to use an expensive material for the reactor.

Furthermore, this first-step reaction has few side reactions, and N, N'-disubstituted urea can be obtained in high yield.

Further, in the second-step reaction, since it is not necessary to use a catalyst, aromatic urethane can be recovered as a distillation residue without distilling. Moreover, since the aromatic primary amine, which is a substance to be distilled, and the residual organic compound having a hydroxyl group are substances having a relatively low boiling point, the distillation operation can be performed under mild conditions, and the operation becomes easy. Moreover, the recovered aromatic primary amine can be reused in the first stage N, N'-disubstituted urea formation reaction. Furthermore, the second-step reaction proceeds almost quantitatively with no catalyst reaction, and there are few side reactions. Therefore, although it is a two-step reaction, aromatic urethane can be produced in high yield.

[Examples] Next, examples of the present invention will be described. In each example, the term "alkyl carbamate" is used in place of the term "urethane" which is a commonly used name, and the individual substance names are clearly indicated.

Example 1 An inner volume of 200 m, a magnetic stirring type autoclave, 5.6 g of nitrobenzene, 7.8 g of aniline, 27 m of toluene,
After adding 6.3 g of N, N, N ′, N′-tetramethylurea (hereinafter abbreviated as TMU) and 20 mg of Ru ₃ (CO) ₁₂ and replacing the inside of the system with carbon monoxide, 50 kg / cm of carbon monoxide was added. Pressed so as to be ² . The mixture was reacted at 160 ° C. for 2.0 hours with stirring. After the reaction was completed, the reaction solution was cooled to room temperature, evacuated and filtered to obtain 3.5 g of N, N'-diphenylurea crystals.
Got When the filtrate was analyzed by gas chromatography and high performance liquid chromatography, N, N'-diphenylurea
It contained 0.1 g and 2.9 g of nitrobenzene. From this, the TOF (Turn Over Frequency) on the basis of the catalytic metal atom of N, N′-diphenylurea formation was 100 h ⁻¹ , and the selectivity on the basis of nitrobenzene was 94%.

Then, the isolated N, N'-diphenylurea crystal 3.0
g, 50 g of methanol are charged into another electromagnetic stirring type autoclave having an internal volume of 200 m, and the mixture is stirred at 160 ° C.
And reacted for 3 hours. As a result of gas chromatographic analysis of the reaction solution after the completion of the reaction, the yield of methyl N-phenylcarbamate was 96% and the yield of aniline was 95%.

Example 2 Next, in an apparatus and operation similar to those shown in Example 1, an amount of TMU was changed to 16.4 g and toluene was changed to 15 m, and an N, N'-diphenylurea production experiment was conducted. The results are shown in Table 1.

Furthermore, N, N'-diphenylurea isolated here 3.
When 0 g and 50 g of methanol were reacted in the same apparatus and operation as in Example 1, methyl N-phenylcarbamate and aniline were respectively obtained in a yield of 95.
% And 94%.

Comparative Example 1 In the same apparatus and operation as shown in Example 1, TMU was not added, the amount of toluene was changed to 32 m, and the production experiment of N, N′-diphenylurea was conducted. Shown in 1.

Comparative Example 2 In the same apparatus and operation as shown in Example 1, pyridine was added instead of TMU, and N, N′-
Table 1 shows the results of the diphenylurea production experiment.

Comparative Example 3 In the same apparatus and operation as shown in Example 1, benzonitrile was added instead of TMU, and N,
Table 1 shows the results of the N'-diphenylurea production experiment.

Examples 3 to 8 Table 2 shows the results of an experiment for producing N, N'-diphenylurea by changing the solvent of the amide compound to be added in the same apparatus and operation as those shown in Example 1. .

Furthermore, N, N'-diphenylurea isolated here 3.
Table 3 shows the results of an experiment for producing methyl N-phenylcarbamate and aniline by reacting 0 g with 50 g of methanol in the same apparatus and operation as in Example 1.

Example 9 In the same apparatus and operation as in Example 1, the catalyst used was [Ru ₂ (CO) ₄ (HCOO) ₂ ] n.
Table 4 shows the results of the N, N′-diphenylurea production experiment.

Furthermore, N, N'-diphenylurea isolated here 3.
When 0 g and 50 g of methanol were reacted in the same apparatus and operation as in Example 1, methyl N-phenylcarbamate and aniline were respectively obtained in a yield of 95.
% And 95%.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masatsugu Mizuguchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Inventor Tetsuo Hachiya 1-2-1-2, Marunouchi, Chiyoda-ku, Tokyo Inside the Steel Pipe Co., Ltd. (72) Inventor Tomochi Nakamura 1-2 1-2 Marunouchi, Chiyoda-ku, Tokyo Inside the Nippon Steel Pipe Co., Ltd. (56) References Japanese Patent Publication No. 5-29349 (JP, B2)

Claims (3)

[Claims] 1. When a reaction of an aromatic primary amine, an aromatic nitro compound and carbon monoxide, a catalyst mainly containing a compound containing a platinum group metal is used, and an amide compound is used as a solvent or a solvent. Used as a part to produce N, N'-disubstituted urea, and then to separate and recover the produced N, N'-disubstituted urea from the reaction solution, and the N obtained in the urea production step. , N'-disubstituted urea and an organic compound containing a hydroxyl group are reacted to produce an aromatic primary amine and an aromatic urethane, and then the aromatic primary amine is separated to obtain an aromatic urethane. And a step of circulating the separated aromatic primary amine to the urea formation step, the method for producing an aromatic urethane. 2. The method for producing an aromatic urethane according to claim 1, wherein the urea formation step is performed without using a halogen compound. 3. The method for producing an aromatic urethane according to claim 1, wherein the reaction of the reaction N, N′-disubstituted urea with an organic compound having a hydroxyl group is carried out without using a catalyst.