JPH0667891B2 - Method for producing aromatic urethane - Google Patents

Description

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

[Prior art and its problems]

Conventionally, various methods for producing aromatic urethane have been proposed, but they are roughly classified into a method using an aromatic nitro compound as a starting material and a method using an aromatic primary amine as a starting material.

The method using an aromatic nitro compound as a starting material is mainly based on an aromatic nitro compound (for example, nitrobenzene), an organic compound having a hydroxyl group (for example, alcohols), carbon monoxide, and a platinum group metal compound such as palladium or rhodium. The reaction is carried out in the presence of a catalyst to produce an aromatic urethane reductively. This method is disclosed, for example, in Japanese Patent Laid-Open No.
-98240, JP-A-54-22339, JP-B-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 a hydroxyl group-containing organic compound (eg, alcohols) are used in the presence of an oxidizing agent such as oxygen or an organic nitro compound. In this method, carbon monoxide is reacted in the presence of a catalyst mainly composed of a platinum group metal compound such as palladium or rhodium to oxidatively produce an aromatic urethane. This method is disclosed, for example, in JP-A-55-1247.
50, JP-A-55-120551, JP-A-59-172
451 etc.

In the above-mentioned conventional techniques, in any of the methods, since the platinum group metal compound as 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 as a co-catalyst is used. And is dissolved in the reaction system. However, halogen compounds are highly corrosive to metal materials such as reaction vessels and piping valves, and therefore expensive metal materials having excellent corrosion resistance must be used.

Furthermore, when the platinum group metal compound, which is the main catalyst, is used by dissolving it in the reaction solution, even if it is used as a solid in the metal state, part of the platinum group metal is eluted in the reaction solution due to the halogen compound. To do. However, in order to recover the platinum group metal compound from the reaction solution after completion of the reaction, complicated operation and great cost are required.

A hydroxyl group-containing organic compound, which is a reaction raw material, is used as a reaction solvent. Aromatic urethane has a very high solubility in the hydroxyl group-containing organic compound. 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. Become. 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. Moreover, a method by distillation can be considered as another method for recovering the aromatic urethane. However, in this case, the aromatic urethane must be distilled in order to recover the dissolved catalyst as a distillation residue. However, aromatic urethane is a high-boiling compound and must be distilled under a high vacuum of about 1 mmHg in the medium temperature range of 100 to 150 ° C.

Furthermore, when an aromatic nitro compound is used as a starting material, a small amount of unreacted aromatic nitro compound remains in the solution after the reaction. If distillation is performed in this state, the aromatic urethane will be colored by the aromatic nitro compound.

As described above, it is difficult to separate and collect the aromatic urethane from the solution, and further to collect and reuse the catalyst, whether by crystallization or distillation.

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

[Technical problem to be solved by the invention]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing an aromatic urethane that does not use a halogen compound as a cocatalyst and solves various problems caused by this use. is there. Another object of the present invention is to produce an aromatic urethane by a two-step reaction to improve the yield of the aromatic urethane, and to easily recover the catalyst and the produced aromatic urethane. To submit the manufacturing method. Further, an object of the present invention is to add an aromatic primary amine in a large excess in the urea formation reaction carried out in the first step and substantially increase the reaction rate by using it as a solvent to efficiently produce aroma. It is intended to obtain a method for producing a group urethane.

[Means for solving technical problems]

The present invention is a method for producing an aromatic urethane including three steps.

In the first step, an aromatic mononitro compound, an aromatic primary amine, and carbon monoxide are reacted using a catalyst mainly composed of a ruthenium complex compound to produce an N, N′-di-substituted urea. To do. Here, the aromatic primary amine is added in a large excess and used substantially as a solvent. Then, the produced N, N′-disubstituted urea is separated and recovered from the reaction solution.

In the second step, N, N′-obtained in the first step
The di-substituted urea and an organic compound containing a hydroxyl group are reacted to produce an aromatic primary amine and an aromatic urethane,
Then, the aromatic primary amine is separated to obtain an aromatic urethane.

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

Next, the invention will be specifically described.

First, as shown in the following formula, an aromatic mononitro compound, an aromatic primary amine, and carbon monoxide are reacted with each other using a catalyst containing a ruthenium complex compound as a main component.

In the first-step reaction, the aromatic primary amine that is the starting material for the reaction is added in large excess, and the reaction is carried out substantially as a solvent.

Examples of this aromatic primary amine include enilines, aminonaphthalenes, aminoanthracenes, aminobiphenyls, and the like. Specific compounds include aniline, o-,
m- and p-toluidine, o-, m-, and p-chloroaniline, α and β naphthylamine, 2-methyl-1
-Aminonaphthalene, isomers of these aromatic primary amines, and mixtures thereof.

Aromatic mononitro compounds include nitrobenzenes,
There are nitronaphthalenes, nitroanthracenes, nitrobiphenyls and the like, and specific compounds include nitrobenzene, o-, m-, and p-nitrotoluene, o-
Nitro-p-xylene, 2-methyl-1-nitronaphthalene, o-, m-, and p-chloronitrobenzene, 1
Examples include -bromo-4-nitrobenzene and isomers of these aromatic mononitro compounds, and also a mixture thereof.

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

The ruthenium complex compound used as a catalyst is Ru
₃ (CO) ₁₂ , H ₄ Ru ₄ (CO) ₁₂ , Ru (CO) ₃ (PPh ₃ ) ₂ , Ru (CO) ₃ (dpp
e), (Ru (CO) ₂ (HCO ₂ ) P (CC ₆ H ₁₁ ) ₃ ) ₂ , Ru (acac) ₃ , and the like. However, dppe: diphenylphosphinoethane and acac: acetylacetonate. Further, not only the ruthenium complex compound alone, but also cobalt, iron, rhodium, palladium and the like can be used in combination.

The reaction temperature is usually 80 to 300 ° C., preferably 120 to 2
It is better to carry out at 00 ° C. Reaction pressure is 1 ~ 500kg / c
It is good to carry out in the range of m ² , preferably 1 to 300 kg / cm ² . The reaction time varies depending on the reaction system, catalyst and other reaction conditions, but is usually several minutes to several hours.

However, the N, N'-disubstituted urea obtained by this reaction has low solubility in the aromatic primary amine used as the solvent. For this reason, the N, N′-disubstituted urea formed is precipitated as crystals only by cooling the solution after the reaction to about room temperature. Therefore, by passing this solution over N,
The N'-disubstituted urea is obtained as a solid. On the other hand, the catalyst is obtained as a solution together with the solvent. The solution containing this catalyst can be reused for this reaction.

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

Examples of the organic compound having a hydroxyl group include monohydric alcohols and monohydric phenols, and specifically, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl and t-butyl. And monophenols such as phenol, chlorophenol, methyl, ethyl, n-propyl, iso-propyl, and other alkylphenols.

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 usually under autogenous pressure at the reaction temperature of the hydroxyl group-containing organic compound or solvent used.

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 the first stage N, N '
Reused in the reaction for the production of disubstituted urea.

[Operation and effect of the invention]

According to this invention, N generated in the first-step reaction,
Since the N'-disubstituted urea has a low solubility in the aromatic primary amine as a solvent, it can be easily crystallized by cooling it to room temperature, and the N, N'-
The di-substituted urea can be recovered. Moreover, the catalyst is contained in the liquid together with the solvent and can be reused in the first-step reaction.

After the reaction, by cooling to room temperature, when the reaction system solidifies, the components other than N, N'-disubstituted urea in the reaction mixture are washed with a solvent such as toluene and benzene,
It can be easily separated and only the N, N'-disubstituted urea can be taken out alone. Also, the washing liquid, after distilling off the solvent,
It can be subjected to the reaction again.

In this reaction, it is also possible to use a compound which does not participate in this reaction, such as toluene or cyclohexane, as a solvent. However, when the concentration of the aromatic primary amine as a raw material is increased, the reaction rate is increased. Therefore, the reaction is performed at a high reaction rate by adding the aromatic primary amine in a large excess and substantially using it as a solvent. be able to.

Further, in the present invention, the catalyst is mainly composed of a ruthenium complex compound, and it is not necessary to use a halogen compound.
Therefore, the corrosion of the material is extremely small, and it is not necessary to use an expensive material.

Furthermore, the first-stage reaction has few side reactions and is highly yielded.
N, N'-disubstituted ureas can be obtained.

Further, in the second stage reaction, since it is not necessary to use a catalyst, the aromatic urethane can be recovered as a distillation residue without distilling. Moreover, since the aromatic primary amine and the residual hydroxyl group-containing organic compound, which are the substances to be distilled, are substances having relatively low boiling points, 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 has few side reactions as in the first-step reaction. Therefore, although it is a two-step reaction, aromatic urethane can be produced in high yield.

〔Example〕

Next, examples of the present invention will be described. In each example, the term "alkyl carbamate" is used in place of the general term "urethane" to clearly indicate the individual substance names.

Example 1 3.71 g of nitrobenzene, 40.0 m of aniline, Ru ₃ (CO) ₁₂ 0.00509 were placed in an electromagnetic stirring autoclave having an internal volume of 200 m.
After adding g, the inside of the system was replaced with carbon monoxide, and then carbon monoxide was injected at 50 kg / cm ² . 16 with stirring
The reaction was carried out at 0 ° C for 1.5 hours. After completion of the reaction, the mixture was cooled to room temperature, and after evacuation, the reaction solution was filtered to obtain 5.42 g of crystals of N, N'-diphenylurea. When the liquid was analyzed by liquid chromatography, it contained 0.37 g of N, N'-diphenylurea, and nitrobenzene was not detected.

The yield of N, N'-diphenylurea was 85% only in the isolated one, and 9% including the one existing in the solution.
1%. The turnover frequency of the catalyst is 84 [mol-Ph
NO ₂ / mol-Ru · hr].

Then, isolated N, N'-diphenylurea crystals 3.00
g, methyl alcohol 50.00 g, another internal volume of 200 m
It is charged into the electromagnetic stirring type autoclave of 1 while stirring.
The reaction was carried out at 60 ° C for 3 hours. After the reaction was completed, the reaction solution was analyzed and as a result, the yield of methyl N-phenylcarbamate was 94% and the yield of aniline was 95%.

Examples 2 to 5 Next, the results of an experiment for producing N, N'-diphenylurea in the same apparatus and operation as those shown in Example 1 are shown in the table.

Example 6 Nitrobenzene 1.80 g, aniline 40.0 m, Ru (a
cac) ₃ 0.0800g, reaction temperature 160 ℃, CO charge 50kg
The experiment was conducted in the same manner as in Example 1 with the reaction time of / cm ² and the reaction time of 2.0 hours. The amount of crystals obtained was 2.80 g, nitrobenzene was not detected in the liquid, and N, N'-diphenylurea
It contained 0.27 g.

The yield of N, N'-diphenylurea was 90% only in the isolated one, and 9% including the one existing in the solution.
9%. The turnover frequency of the catalyst is 36 [mol-Ph
NO ₂ / mol-Ru · hr].

Then, the same operation as in Example 1 was performed to obtain crystals.
N, N'-diphenylurea total amount and ethyl alcohol 50.00
was reacted with g. After the reaction was completed, the reaction solution was analyzed and the yield of ethyl N-phenylcarbamate was 93%.
The yield of aniline was 95%.

Example 7 Nitrobenzene 2.32 g, aniline 40.0 m, Ru
An experiment was conducted in the same manner as in Example 1 except that (CO) ₃ (PPh ₃ ) _{2 was} 0.0817 g, the reaction temperature was 160 ° C., the CO content was 50 kg / cm ² , and the reaction time was 1.5 hours. The crystals obtained were 3.38 g, and nitrobenzene was not detected in the liquid, and 0.31 g of N, N'-diphenylurea was contained.

The yield of N, N'-diphenylurea was 93% when it was included only in the isolated product and when it was included in the 85% solution.
Is. The catalyst turnover frequency is 109 [mol-PhNO
₂ / mol-Ru · hr].

Next, by the same operation as in Example 1, the obtained N, N'-
3.00g of diphenylurea crystals and 50.00 of methyl alcohol
was reacted with g. After the reaction was completed, the reaction solution was analyzed and as a result, the yield of methyl N-phenylcarbamate was 93%,
The yield of aniline was 94%.

Comparative Example 1 3.82 g of nitrobenzene, 2.85 g of aniline, 34.58 g of toluene and R were placed in an electromagnetic stirring autoclave having an internal volume of 200 m.
After adding 0.10 g of u ₃ (CO) ₁₂ and substituting the inside of the system with carbon monoxide, carbon monoxide was injected under pressure to 50 kg / cm ² .
Then, the mixture was reacted at 160 ° C. for 6 hours while stirring. After the reaction was completed, the reaction solution was cooled to room temperature, and after evacuation, the reaction solution was passed through N
5.91 g of crystals of N'-diphenylurea were obtained. When the liquid was analyzed by liquid chromatography, nitrobenzene was not detected.

The isolated yield of N, N′-diphenylurea was 90%, and the turnover frequency of the catalyst was 11 [mol-PhNO ₂ / mol-Ru · h].
r].

Next, 3.00 g of the crystals and 50.00 g of methyl alcohol were charged into another magnetic stirring type autoclave having an internal volume of 200 m, and reacted at 160 ° C. for 3 hours while stirring. As a result of analyzing the reaction solution after completion of the reaction, the yield of methyl N-phenylcarbamate was 94% and the yield of aniline was 95%.

Comparative Example 2 Nitrobenzene 6.12 g, methanol 37.00 g, Ru ₃ (CO) ₁₂ 0.11 g in an electromagnetic stirring autoclave having an internal volume of 200 m.
Was charged, and the inside of the system was replaced with carbon monoxide, and then carbon monoxide was pressure-fitted to 50 kg / cm ² . Then, the mixture was reacted at 160 ° C. for 5 hours with stirring, and after the reaction was completed, the solution was analyzed by liquid chromatography. As a result, the conversion rate of nitrobenzene was 32% and the selectivity of methyl N-phenylcarbamate was 13%. Raw aniline selectivity is 4
It was 0%. That is, in terms of yield, the yield of methyl N-phenylcarbamate is 4% and the yield of by-product aniline is 13%.
Met.

Comparative Example 3 An aniline (4.63 g), nitrobenzene (6.12 g) and methanol (37.00) were placed in an electromagnetic stirring autoclave having an internal volume of 200 m.
g and Ru ₃ (CO) ₁₂ 0.11 g were charged and the inside of the system was replaced with carbon monoxide, and then carbon monoxide was pressure-fitted to 50 kg / cm ² . Then, the mixture was reacted at 160 ° C. for 5 hours with stirring, and after completion of the reaction, this solution was analyzed by liquid chromatography. As a result, the yield of methyl N-phenylcarbamate based on aniline was 61%, and the yield of N, N'-diphenylurea was 4%.

Then, this solution was left in a freezer at -5 ° C for one day and night.
No crystals were deposited.

Claims (2)

[Claims] 1. An aromatic mononitro compound, an excess of an aromatic primary amine which can be substantially used as a solvent, and carbon monoxide are reacted using a catalyst mainly composed of a ruthenium complex compound to produce N, N'-. Produced di-substituted urea, then produced
A urea forming step of separating and recovering N, N′-disubstituted urea from the reaction solution, and an N, N′-disubstituted urea obtained in the urea forming step are reacted with an organic compound containing a hydroxyl group to form an aromatic compound. First
Amine and aromatic urethane are formed, and then aromatic primary
A method for producing an aromatic urethane, comprising: a step of separating an amine to obtain an aromatic urethane; and a step of recycling the separated aromatic primary amine to the urea formation step. 2. The method for producing an aromatic urethane according to claim 1, wherein the reaction between the N, N'-disubstituted urea and the organic compound containing a hydroxyl group is carried out without using a catalyst.