JPH02124866A - Production of aromatic urethane - Google Patents

Abstract

PURPOSE:To obtain an aromatic urethane in high yield and, at the same time, to easily recover the catalyst and urethane by two-stage reaction process comprising the 1st step to react an aromatic primary amine with CO in the presence of a catalyst and the 2nd step to carry out alcoholysis of produced urea compound separated from the system. CONSTITUTION:An aromatic primary amine is made to react with carbon monoxide in the presence of a catalyst composed of a platinum-group metal compound and a halogen compound and the obtained N,N'-disubstituted urea is separated from the reaction liquid. The separated N,N'-disubstituted urea is made to react with an organic compound having hydroxyl group to effect the alcoholysis of the urea compound and obtain an aromatic primary amine and an aromatic urethane. The aromatic primary amine is separated from the mixture to leave the aromatic urethane. The separated aromatic primary amine is circulated to the 1st stage reaction process. The 2nd stage reaction, i.e., the reaction of the N,N'-disubstituted urea with the hydroxyl-containing organic compound is preferably carried out in the absence of catalyst. The product and the catalyst are easily recoverable and the catalyst component can be efficiently reused.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing aromatic urethane.

[Prior art and its problems] Conventionally, various methods for producing aromatic urethane have been proposed, but
These include methods using aromatic nitro compounds as starting materials;
It is broadly divided into methods that use aromatic primary amines as starting materials.

In the method using an aromatic nitro compound as a starting material, an aromatic nitro compound (e.g., nitrobenzene), a compound containing a hydroxyl group (e.g., alcohol), and carbon monoxide,
This is a method for reductively producing aromatic urethane by reacting it in the presence of a catalyst system mainly consisting of a platinum group metal compound such as palladium or rhodium and a halogen compound as a co-catalyst.

This method has been proposed, for example, in Japanese Patent Publication Nos. 43-23939, 51-98240, and 54-22339.

In addition, in the method using an aromatic primary amine as a starting material, an aromatic primary amine (e.g. aniline) and an organic compound containing a hydroxyl group (e.g. alcohols) are combined in the presence of an oxidizing agent such as oxygen or an organic nitro compound. This is a method for producing aromatic urethane oxidatively by reacting urethane and carbon monoxide in the presence of a catalyst mainly consisting of a platinum group metal compound such as palladium or rhodium. This method is used, for example, in JP-A-55
This method has been proposed in Japanese Patent Application Laid-open No. 120551, Japanese Patent Application Laid-Open No. 124750-1980, Japanese Patent Application Laid-open No. 9172451-1987, and so on.

These methods produce aromatic urethane in one step by reacting an aromatic nitrogen-containing compound and carbon monoxide in the presence of a hydroxyl group-containing compound, and therefore, a platinum group metal as a main catalyst is used. Whether the compound is used dissolved in the reaction solution or used as a solid in the metallic state, some platinum group metals may be eluted into the reaction solution. Separating the product from the inside and recovering the platinum group metal compound requires complicated operations and a large amount of cost.

Further, as a reaction solvent, an organic compound having a hydroxyl group as a starting material is used, and aromatic urethane has a very high solubility in this organic compound having a hydroxyl group. Therefore, in order to separate and recover aromatic urethane from a solution after 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. It becomes necessary. Moreover, even if this operation is performed, it is difficult to separate and isolate the aromatic urethane and the catalyst component dissolved in the solution. Distillation may also be considered as another method for recovering aromatic urethane. However, in this case, the aromatic urethane must be distilled off in order to recover the dissolved catalyst as a distillation residue.

However, aromatic urethane is a high boiling point compound and must be distilled under high vacuum at a temperature range of 100 to 140°C. Therefore, a decrease in catalyst performance is unavoidable.

As described above, in the conventional method, it is impossible to separate and recover aromatic urethane from a solution, and then recover and reuse the catalyst.
It is difficult whether it is crystallized or distilled.

Furthermore, a method has been proposed for producing aromatic urethanes by oxidative carbonylation of N,N'-diarylurea using a platinum group metal compound as a cocatalyst in the presence of a halogen compound (JP-A-55-120552, Japanese Patent Publication No. 1983
-164565).

In this case, there is an advantage that 2 equivalents of aromatic urethane are produced from N,N'-disubstituted urea, but the same problem remains in separating the produced aromatic urethane from the catalyst system as described above. The disadvantage is that it requires complicated operations and a large amount of cost.

Furthermore, even in the case of a one-step reaction using an aromatic nitro compound as a starting material, there are problems in separating the product from the catalyst, and in addition, aromatic amines and N,N'-disubstituted ureas are produced as by-products, and aromatic N in the case of general reactions using primary amines as starting materials.

Since N'-disubstituted urea is produced as a by-product, there are drawbacks such as a decrease in the yield of aromatic urethane.

[Technical Problems to be Solved by the Invention] This invention was made in view of the above circumstances, and the conventional method was to synthesize aromatic urethane from aromatic primary amine in one step. By producing aromatic urethane through a two-step reaction of the separation process and the urethane production process by alcoholysis of ureas, the yield can be improved, and the catalyst and the produced aromatic urethane can be easily recovered. An object of the present invention is to provide a method for easily producing aromatic urethane. That is, when using a catalyst soluble in a solvent, N, N'
-Disubstituted urea easily crystallizes from the reaction system, making it possible to separate it. Furthermore, when a solid catalyst is used, if a small amount of metal compound dissolves into the solution, or if a halogen compound as a cocatalyst is present in the reaction solution, catalyst components and products can easily separate. can be separated, and the catalyst components can be efficiently recovered and reused.

[Means for Solving Technical Problems] The present invention is a method for producing aromatic urethane that includes three steps in order to efficiently separate catalyst components and products.

In the first step, an aromatic primary amine and carbon monoxide are reacted using a catalyst mainly consisting of a platinum group metal compound or a halogen compound as a catalyst, resulting in N,N'
- produces a di-substituted urea.

Next, the generated N,N'-disubstituted urea is separated and recovered from the reaction solution.

In the second step, the N obtained in the first step is
, N'-disubstituted urea and an organic compound containing a hydroxyl group, preferably without using a catalyst,
A primary aromatic amine and an aromatic urethane are produced.

Next, in the third step, the aromatic primary amine is separated to obtain an aromatic urethane, and the separated aromatic primary amine is recycled to the first step.

The present invention provides a method for efficiently producing aromatic urethane, and it is possible to solve the problems in the prior art and further expand the scope of application of the present invention. That is, in the first step, N is converted from an aromatic primary amine by a known method.

N'-disubstituted ureas are produced, and the resulting N,N
It can also be used to efficiently separate the '-disubstituted ureas from the catalyst components (including co-catalyst components). In this way, by conducting the reaction in a two-step method, it is possible to solve the problem of separation of eluted trace metals that occurs when solid catalysts are used, and to recover and reuse the often used co-catalysts such as I\rogen compounds. This shows the possibility of doing it efficiently.

Next, the present invention will be specifically explained.

(First step) The first step is N based on the following reaction formula.

N'-disubstituted urea is produced.

mouthArNH3+ Co = Ar-NHCNl-Ar +
CO2+ [Old aromatic secondary amines include anilines, aminonaphthalenes, aminoanthracenes, aminobiphenyls, etc. Specific compounds include aniline, o-m-1 and p-toluidine, o- m
-1 and p-chloroaniline, 1- and 2-aminonaphthalene, 2-methyl-1-aminonaphthalene, diaminobenzene, triaminobenzene, aminotoluene, diaminotoluene, diaminonaphthalene, and isomers thereof, as well as these Examples include mixtures of

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

A compound containing a platinum group metal is a compound such as a platinum group element such as ruthenium, rhodium, palladium, or platinum, and a ligand such as carbon monoxide or phosphines, or an organometallic compound having an organic group.

Furthermore, these platinum group metals include cobalt, iron, rhodium,
Palladium and the like can also be used in combination. Specifically, a mixture of complex compounds of each metal is used, or a mixed metal carbonyl cluster compound is used.

The reaction temperature is usually 30-300°C, preferably 120-300°C.
It is carried out in a temperature range of 200°C. Reaction pressure is 1-500
kg/cm2, preferably 1-150 kg/
cm2 range, and the reaction time varies depending on other conditions, but is usually from several minutes to several hours.

Therefore, the N obtained in this first step.

N'-disubstituted urea has low solubility in solvents and raw materials such as aromatic amines and compounds containing hydroxyl groups. Therefore, simply by cooling the solution after the reaction to about room temperature, the produced ureas will precipitate out as crystals. Therefore, by filtering this solution, ureas can be efficiently obtained as a solid substance. On the other hand, if the catalyst is a solid catalyst, the reaction operation will be extremely simple. In the case of a catalyst soluble in a solvent, the catalyst liquid can be reused as it is after crystallizing and separating the product. After the reaction, if the reaction system solidifies by cooling to room temperature, N in the reaction mixture.

Components other than N'-disubstituted urea can be easily separated by washing with a solvent such as toluene or benzene.
'-Disubstituted urea alone can be extracted. Further, the washing liquid can be subjected to the reaction again after distilling off the solvent.

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

關Ar-N)IcNH-Ar + Roll-A
r-NlIC0OR+ Ar-NH2 Organic compounds containing hydroxyl groups include -valent alcohols and -valent phenols, and specifically, methyl, ethyl, n-
Examples include monohydric alcohols such as propyl, isopropyl, n-butyl, isobutyl, and t-butyl, and alkyl-substituted phenols such as phenol, chlorophenol, methyl, ethyl, n-propyl, and isopropyl, and their isomers. .

The reaction temperature is usually 80-300°C, preferably 120-300°C.
It is preferable to carry out at a temperature range of 200°C. The pressure is set at the autogenous pressure at the reaction temperature of the organic compound containing a hydroxyl group or the solvent that is commonly used.

And this reaction can be carried out without using a catalyst.

After completion of this reaction, a distillation operation is performed to recover the aromatic urethane as a distillation residue, and on the other hand, the aromatic primary amine is recovered by distillation. This aromatic primary amine is the first N
, and reused in the reaction for producing N'-disubstituted urea.

[Operations and effects of the invention] Aromatic primary amine using a ruthenium or rhodium carbonyl complex catalyst, which is a typical reaction example of the first stage N,N'-disubstituted urea production method according to the present invention. and N produced in the carbonylation reaction of aromatic nitro compounds.

Since N'-disubstituted urea has low solubility in solvents and compounds containing aromatic primary or hydroxyl groups as raw materials, it can be easily crystallized by cooling it to room temperature, and it can be efficiently crystallized by filtration. .

N'-disubstituted ureas can be isolated.

In this reaction, it is also possible to use compounds that do not participate in this reaction, such as toluene and cyclohexane, as solvents. However, since increasing the concentration of the aromatic primary amine as a raw material increases the reaction rate, it is necessary to add a large excess of the aromatic primary amine and use it as part of the solvent to form the aromatic primary amine. The reaction can be carried out at a high reaction rate.

Furthermore, by converting the conventional reaction using a palladium-halogen compound catalyst system in the production of aromatic urethane using a membrane process into a two-step process, it is possible to separate the eluted palladium and remove the dissolved halogen compounds in the urea production reaction step. A ripple effect can be expected in which separation from the product becomes extremely easy.

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 being distilled off. In addition, the aromatic primary amine that is the substance to be distilled and the remaining organic compound containing a hydroxyl group are compounds with relatively low boiling points, so the distillation operation can be carried out under mild conditions, making the operation easier. . Moreover, the recovered aromatic primary amine can be reused in the first stage N,N'-disubstituted urea production reaction. Furthermore, the second stage reaction, like the first stage reaction, has fewer side reactions. Therefore, although it is a two-step reaction, aromatic urethane can be produced in high yield.

[Example] Next, an example of the present invention will be described. In addition, in each example, the term "r alkyl carbamate" is used instead of the term "urethane", which is an indicative common name, to clearly indicate the name of each substance.

Example 1 According to the method described in Japanese Patent Publication No. 63-32347, 40 ml of aniline, 0.050 g of SPd black, and 0.40 g of potassium iodide were charged into a 200 ml electromagnetic stirring autoclave, and the system was replaced with oxygen. Afterwards, oxygen was injected at a pressure of 2.5 kg/cm2.

Further, carbon monoxide was press-fitted thereon at a total pressure of 50 g/cm2. The reaction was carried out at 160° C. for 2 hours while stirring. After the reaction was completed, the reaction solution was cooled to room temperature, evacuated, and filtered to obtain a mixture of N,N'-diphenylurea crystals and a catalyst. Dissolve this mixture in acetone and
The undissolved catalyst was filtered off and the filtrate was concentrated to N,N'
- 6.50 g of diphenyl urea crystals were obtained. Also, the N obtained here.

As a result of elemental analysis, N'-diphenylurea was found to be free of halogen elements and palladium. moreover,
When the N,N'-diphenylurea obtained here and methanol were reacted according to Example 1, the yield was 94%.
Methyl N-phenylcarbamate was obtained.

Example 2 An experiment for producing N,N'-diphenylurea was conducted using the same equipment and operation as in Example 1, except that the catalyst was changed to 5% Pd-carbon.

N'-diphenylurea was obtained in a yield of 18.99 g.

Further, as a result of elemental analysis, it was found that the N,N'-diphenylurea obtained here did not contain a halogen element or palladium. In addition, N, N′ − obtained in this way
When diphenyl urea and methanol were reacted according to Example 1, methyl N-phenylcarbamate was obtained with a yield of 95%.

Comparative Example 1 In a magnetic stirring autoclave with an internal volume of 200 ml, 4.83 g of aniline, 8.12 g of nitrobenzene, 37.0 g of methanol, and 120.11 Ru3 (Co) were added.
After replacing the inside of the system with carbon monoxide, carbon monoxide was injected under pressure to a concentration of 50 kg/cm2. Next, the reaction was carried out at 160°C for 5 hours with stirring, and after the reaction was completed, this solution was analyzed by HPLC. As a result, the yield of methyl N-phenylcarbamate was 61% based on nitrobenzene, and the yield of N,N'-diphenylurea was 61%. The yield was 4%. Then, this solution was stored in a freezer at 5° C. for a day and night, but no crystals were deposited.

Applicant's agent: Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) When producing an aromatic urethane from a primary aromatic amine, carbon monoxide, and a compound containing a hydroxyl group, (i) Using a platinum group metal compound and a halogen compound as a catalyst, By reacting a monoamine with carbon monoxide, an N,N'-disubstituted urea is produced,
Next, a urea generation step of separating and isolating the generated N,N'-disubstituted urea from the reaction solution; (ii) containing the N,N'-disubstituted urea obtained in the urea generation step and a hydroxyl group; a step of reacting with an organic compound to produce an aromatic primary amine and an aromatic urethane; (iii) then separating the aromatic primary amine obtained in step (ii) to obtain an aromatic urethane; , a step of recycling the separated aromatic primary amine to the step (i), and these steps are performed separately. (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.