JPH0662543B2 - 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] Conventionally, various methods for producing an aromatic urethane have been proposed,
These are methods using an aromatic nitro compound as a starting material,
It is roughly classified into a method using an aromatic primary amine as a starting material.

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 for producing an aromatic urethane reductively by reacting in the presence of a catalyst mainly containing a platinum group metal compound such as palladium and rhodium and a halogen compound as a cocatalyst. This method is disclosed, for example, in Japanese Examined Patent Publication No. 43-2393.
9, JP-A-51-98240, JP-A-54-223.
No. 39, 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 present in the presence of an oxidizing agent such as oxygen or an organic nitro compound. And carbon monoxide are reacted in the presence of a catalyst mainly composed of a platinum group metal compound such as palladium and rhodium to oxidatively produce an aromatic urethane. This method is disclosed, for example, in Japanese Patent Laid-Open No.
-120551, JP-A-55-124750, JP-A-55-9172451, and the like.

These methods are methods for producing an aromatic urethane in a single step by reacting an aromatic nitrogen-containing compound with carbon monoxide in the presence of a compound containing a hydroxyl group, and therefore, the platinum group metal which is the main catalyst is used. Not only when the compound is used by dissolving it in the reaction solution, but also when it is used as a solid in a metal state, a part of the platinum group metal may be eluted in the reaction solution. To separate the product from the inside and recover the platinum group metal compound,
It requires complicated operations and a great deal of expense.

An organic compound having a hydroxyl group, which is a starting material, is used as a reaction solvent. Aromatic urethane has a very high solubility in the organic compound having a hydroxyl group. Therefore, in order to separate and recover the aromatic urethane 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. Will be needed. 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. Another method of recovering aromatic urethane may be distillation. 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 compound and must be distilled under a high vacuum in a temperature range of 100 to 140 ° C. Therefore, the deterioration of the catalyst performance cannot be avoided.

As described above, in the conventional method, the aromatic urethane is separated and recovered from the solution, and the catalyst is further recovered and reused.
Difficult to crystallize or distill.

Further, a method of producing an aromatic urethane by oxidative carbonylation of N, N'-diarylurea in the presence of a halogen compound using a platinum group metal compound as a cocatalyst has been proposed (JP-A-55-120552). , JP-A-58
-164565). In this case, there is an advantage that two equivalents of aromatic urethane are produced from the N, N'-disubstituted urea, but a similar problem remains in the separation of the aromatic urethane produced as described above from the catalyst system. However, there is a drawback that it requires complicated operation and a great deal of cost.

Further, also in the case of a one-step reaction using an aromatic nitro compound as a starting material, the problem of separation of the product from the catalyst and the fact that aromatic amine and N, N′-disubstituted urea are by-produced,
Also, in the case of a general reaction using an aromatic primary amine as a starting material, N, N'-disubstituted urea is produced as a by-product, so that there are drawbacks such as a decrease in the yield of aromatic urethane.

[Technical problem to be solved by the invention] The present invention has been made in view of the above circumstances, and in the conventional method, a method in which an aromatic urethane is synthesized from an aromatic primary amine in a single step is used for the production of ureas and the production thereof. By producing aromatic urethane by a two-step reaction between the separation step and the urethane production step by alcohol decomposition of ureas, the yield is improved, and the catalyst and aromatic urethane produced are recovered. It is to provide a method for easily producing an aromatic urethane. That is, when a solvent-soluble catalyst is used, the N, N′-disubstituted urea is easily crystallized from the reaction system and can be separated. Furthermore, even when a trace amount of a metal compound is dissolved in a solution when a solid catalyst is used, and when a halogen compound which is a cocatalyst is present in a reaction solution, the catalyst component and the product are easily separated from each other. It can be separated and the catalyst components can be efficiently recovered and reused.

[Means for Solving the Technical Problem] The present invention is a method for producing an aromatic urethane, which comprises three steps in order to efficiently separate a catalyst component and a product.

In the first step, an aromatic primary amine and carbon monoxide are reacted in the presence of molecular oxygen using a catalyst mainly composed of a platinum group metal compound or a halogen compound as a catalyst to produce N, This produces an N'-disubstituted urea. 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 containing a hydroxyl group, preferably without using a catalyst,
It produces aromatic primary amines and aromatic urethanes.

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

The present invention provides a method for efficiently producing an aromatic urethane, and the present invention can solve the problems in the prior art and further expand the application range. That is, in the first step, N, N′-disubstituted ureas are produced from an aromatic primary amine by a known method, and then the produced N, N′-disubstituted ureas are used as a catalyst component (cocatalyst component). Can also be used together.
In this way, by reacting in a two-step method, the problem of separation of eluted trace metals, which occurs when a solid catalyst is used,
It also shows the possibility of efficiently recovering and reusing a cocatalyst such as a halogen compound which is often used.

Next, the present invention will be specifically described.

(First Step) In the first step, an N, N′-disubstituted urea is produced in the presence of molecular oxygen that functions as an oxidant, based on the following reaction formula.

Aromatic primary amines include anilines, aminonaphthalenes, aminoanthracenes, aminobiphenyls, and the like. Specific compounds include aniline, o-, and m.
-, And p-toluidine, o-, m-, and p-chloroaniline, 1- and 2-aminonaphthalene, 2-methyl-1-aminonaphthalene, diaminobenzene, triaminobenzene, aminotoluene, diaminotoluene, diamino Examples thereof include naphthalene, isomers thereof, and a mixture thereof.

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

The compound containing a platinum group metal is a compound such as ruthenium, rhodium, palladium, platinum, or another platinum group element, carbon monoxide, a phosphine ligand, or an organic metal compound having an organic group. Further, these elements may be in a metallic state, and these platinum group metals have cobalt,
It is also possible to use iron, rhodium, palladium, etc. in combination. Specifically, the complex compounds of the respective metals are mixed and used, or used as a mixed metal carbonyl cluster compound. Alternatively, the metal element may be supported on activated carbon, graphite, silica, alumina or the like.

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 from 1~150kg / cm ^2,
The reaction time varies depending on other conditions, but is usually several minutes to several hours.

However, the N, N'-disubstituted urea obtained in the first step has low solubility in the solvent, the raw material aromatic amine, and the compound containing a hydroxyl group. For this reason,
By simply cooling the solution after the reaction to room temperature, the generated ureas are precipitated as crystals. Therefore, by filtering this solution, ureas can be efficiently obtained as a solid. On the other hand, if the catalyst is a solid catalyst, the reaction operation becomes extremely simple. In the case of a solvent-soluble catalyst, the catalyst solution can be reused as it is after the product is crystallized and separated. After the reaction, when the reaction system is solidified by cooling to room temperature, the components other than the N, N'-disubstituted urea in the reaction mixture can be easily separated by washing with a solvent such as toluene and benzene. Only the N, N'-disubstituted urea can be taken out alone. Further, the washing liquid can be subjected to the reaction again after distilling off the solvent.

(Second Step) Next, the N, N′-disubstituted urea thus obtained and an organic compound having a hydroxyl group are reacted as 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 specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and t-butyl. And alcohols, and alkyl-substituted phenols such as phenol, chlorophenol, methyl, ethyl, n-propyl and isopropyl, and isomers thereof.

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 using 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.

[Functions and Effects of the Invention] Aromatic primary amines using a ruthenium or rhodium carbonyl complex catalyst, which is a typical reaction example as a method for producing the N, N'-disubstituted urea in the first stage according to the present invention. In the carbonylation reaction of an aromatic nitro compound, the N, N'-disubstituted urea formed has a low solubility in a solvent and a compound containing an aromatic primary or a hydroxyl group as a raw material. Therefore, it is cooled to room temperature. By doing so, crystallization can be easily carried out, and the N, N′-disubstituted urea can be efficiently isolated by filtration.

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, if the concentration of the aromatic primary amine as the raw material is increased, the reaction rate will increase. Therefore, add a large excess of the aromatic primary amine and use it as a part of the solvent to form the aromatic primary amine. Thus, the reaction can be performed at a high reaction rate.

Furthermore, by separating the reaction with the palladium-halogen compound catalyst system when producing aromatic urethane by the conventional one-step method into a two-step method, the eluted palladium is separated and the dissolved halogen compound is generated in the urea production reaction step. A ripple effect that makes it extremely easy to separate from an object can be expected.

Further, in the second stage 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 organic compound containing a residual hydroxyl group are compounds 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 forming reaction. Furthermore, the second stage reaction is
Similar to the first step reaction, 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 According to the method described in JP-B-63-32347, aniline 4 was placed in an electromagnetic stirring autoclave having an internal volume of 200 m.
0m, Pd black 0.050g, potassium iodide 0.40g
Was charged, and the system was replaced with oxygen, and then oxygen was added at 2.5 kg / cm ²
Pressed so that Further, carbon monoxide was pressed onto the above so that the total pressure was 50 g / cm ² . The mixture was reacted at 160 ° C. for 2 hours while stirring. After completion of the reaction, the mixture was cooled to room temperature, and after evacuation, the reaction solution was filtered to obtain a mixture of N, N'-diphenylurea crystals and a catalyst. This mixture was dissolved in acetone, the insoluble catalyst was removed by filtration, and the filtrate was concentrated to obtain 6.50 g of crystals of N, N'-diphenylurea. The N, N′-diphenylurea obtained here was found to contain no halogen element and palladium as a result of elemental analysis. Furthermore, N, obtained here,
When N′-diphenylurea and methanol were reacted according to Example 1, methyl N-phenylcarbamate was obtained with a yield of 94%.

Example 2 A N, N'-diphenylurea production experiment was conducted by the same apparatus and operation as in Example 1 except that the catalyst was changed to 5% Pd-carbon. Yield 6.99 g. Furthermore, N, N ′ obtained here
-Diphenylurea was found by elemental analysis to be free of halogen elements and palladium. In addition, the N, N'-diphenylurea obtained here and methanol are
When reacted according to Example 1, methyl N-phenylcarbamate was obtained with a yield of 95%.

Comparative Example 1 An electromagnetic stirring autoclave with an internal volume of 200 m was placed in an aniline 4.63 g, nitrobenzene 6.12 g, methanol 37.0.
g and Ru3 (CO) 12 0.11 g were added, the system was replaced with carbon monoxide, and then carbon monoxide was injected under pressure to 50 kg / cm ² . Then, the mixture was reacted at 160 with stirring for 5 hours, and after the reaction was completed, the solution was analyzed by HPLC. As a result, the yield of methyl N-phenylcarbamate based on nitrobenzene was 61%, and N, N'-diphenylurea The yield was 4%. Then, this solution was stored in a freezer at -5 ° C for one day and night, but no crystals were deposited.

 ─────────────────────────────────────────────────── ─── 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 this steel pipe company (56) References Japanese Patent Publication No. 5-29349 (JP, B2)

Claims (2)

[Claims] 1. A method for producing an aromatic urethane from an aromatic primary amine, carbon monoxide, and a compound containing a hydroxyl group, wherein (i) a platinum group metal compound and a halogen compound are used as catalysts to produce a molecule. N, N'-disubstituted urea is produced by reacting an aromatic primary amine with carbon monoxide in the presence of gaseous oxygen, and then the produced N, N'-disubstituted urea is produced from the reaction solution. A urea forming step of separating and isolating, and (ii) reacting the N, N'-disubstituted urea obtained in the urea forming step with an organic compound containing a hydroxyl group to form an aromatic primary amine and an aromatic compound. A step of producing a urethane, (iii) then separating the aromatic primary amine obtained in the step (ii) to obtain an aromatic urethane, and ) The process of recycling to the process, Manufacturing method of urethane. 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 having a hydroxyl group is carried out without using a catalyst.