JPH0678304B2 - Method for producing N-alkyl substituted lactam - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an N-alkyl-substituted lactam.

More specifically, it relates to an improved process for producing N-alkyl substituted lactams using lactones and secondary amines or ammonium derivatives thereof as starting materials.

Among the N-alkyl-substituted lactams which are the objects of the present invention, N-alkyl-2-pyrrolidone is particularly useful as a nontoxic solvent having excellent chemical or heat stability and as an intermediate for various organic syntheses. However, quality regulations and requirements are strict, and high quality is desired.

[Prior Art] It is conventionally known that N-alkyl-substituted lactams can be produced by various methods.

To list them, i) a method by reaction of a lactone with a primary amine.

ii) A method of reacting a lactam and an alkylating agent in the presence of a catalyst.

iii) A method by catalytic hydrogenation of a cyclic dicarboxylic acid-N-substituted imide.

iv) A method of hydrolyzing a starting material compound which can be converted into an N-substituted lactam by hydrogenolysis of N-hydroxyalkyl-substituted fukutams, N-vinyllactams and the like in the presence of a catalyst can be mentioned.

Among these, the method i) is most commonly adopted industrially.

That is, this method is excellent in terms of reaction rate, reaction yield, and quality of the product, and is not industrially advantageous because it does not use corrosive raw materials or catalysts. Have the conditions [Kirk Othmer (Kirk
Othmer Encyclopedia of Chemical technolog
y), published by John Wiley
& Sons) (1984) Volume 19 Page 517 and Journal of American Chemical Society (J.Am.Che
m.Soc.,) Vol. 71, p. 897 (1949)].

When a secondary amine is reacted with a lactone instead of a primary amine, an N, N-dialkyl-substituted ω-oxycarboxylic acid amide is formed. It was difficult.

However, according to JP-B-47-18751, γ-butyrolactone is reacted with dimethylamine and trimethylamine within a temperature range of 270 to 290 ° C. to obtain N-methyl-2-pyrrolidone. Yield of 80
%, The use efficiency of the substituted alkyl group of the secondary amine is poor, and the production unit of the secondary amine is large, and the purity is low, and only low-quality production that is easy to color is obtained. The technology could not be adopted.

[Problems to be Solved by the Invention] The primary amine used as a starting material in a conventional method for producing an N-alkyl-substituted lactam is produced by various methods. Most commonly, a lower alcohol, Reaction of raw materials such as halogenated hydrocarbons with ammonia, nitro compounds,
It is produced via a hydrogenation reaction of a nitrile compound or its precursor.

Usually, a primary amine is produced by the reaction of alcohol and ammonia, but the reaction product in this case is not a simple one, and is usually a thermodynamic equilibrium composition or a ratio close to it. A product in which a primary amine is mixed is manufactured.

For example, in the case of the simplest reaction of methanol and ammonia, monomethylamine, dimethylamine, and trimethylamine are produced, in order to suppress the production of mono- and dimethylamine, which are particularly versatile, and the production of trimethylamine, which is less versatile, to be low. Much effort has been expended on research and technological development of the catalysts and reaction conditions and processes of [see, for example, Frank J. Weigert.
J.Weigert) Journal of Catalysis (J.Gata)
l) Vol. 103, pages 20-29 (1987), JP-A-61-254
JP, JP-A-61-256, Chemical Handbook, Applied Chemistry I (1986), Chemical Society of Japan, p. 547].

However, in spite of these efforts, it is substantially difficult to selectively produce, among various amines, only primary amines that are effective for producing N-alkyl-substituted lactams, and it is also difficult to produce them. Distilling and separating only the primary amine from the mixture of the substituted amines mentioned above requires a large energy load and is costly.

Therefore, as the demand for N-alkyl-substituted lactams has increased, there has been a demand for a method for producing N-alkyl-substituted lactams that does not use primary amines.

In order to solve such a problem, the present invention uses a secondary amine, which has been disadvantageous in the conventional quality and yield, and has a high quality and a high yield comparable to those of the primary amine. It is an object of the present invention to provide a method for producing an N-alkyl-substituted lactam in which the production unit of secondary amine is improved.

[Means for Solving Problems] The present inventors have used secondary amines in a reaction for producing an N-alkyl-substituted lactam by reacting a lactone with an amine, and have a good yield and good product quality. In order to find out a different production method, the reaction conditions have been diligently studied, a specific temperature and a specific amount of water are used, and by-products are circulated to solve the above problems, and the present invention has been accomplished. It was

That is, in the present invention, i) a lactone compound is reacted with a secondary amine in the presence of water to give an N, N-dialkyl-substituted compound.
In the method for producing an N-alkyl-substituted lactam via ω-hydroxycarboxylic acid amide, dealcohol decomposition is carried out at a water-lactone (water / lactone) molar ratio of 3-5 and a reaction temperature of 240-265 ° C. To form a lactam ring, and ii) a lactone compound is reacted with a secondary amine in the presence of water to form an N, N-dialkyl-substituted-ω-hydroxy compound. In the method for producing an N-alkyl-substituted lactam via a carboxylic acid amide, the N, N-dialkyl-substituted-ω-hydroxycarboxylic acid amide is heated to a temperature of 240 ° C or higher to form a lactam ring by dealcohololysis. From the method for producing an N-alkyl-substituted lactam, characterized in that the eliminated alcohol is separated and is recycled to the step for producing the secondary amine. Is shall.

The lactone compound used in the production method of the present invention has a skeleton
It is a compound having a 4- to 7-membered ring, and various alkyl- and allyl-substituted derivatives can be used.

Examples of these are propiolactone, γ-butyrolactone, glutarolactone, caprolactone, phthalide, 2-pyrone, coumarin, dihydroaconic acid derivative,
Examples thereof include various compounds that are conventionally known to form a lactam ring, such as dihydrobenzofuranone.

As the amines used in the present invention, a secondary amine having an alkyl group or an aralkyl group having a carbon number of about C _{1 to} C ₂₀ can be widely used, but from the purpose of producing a single reaction product, a nitrogen atom and It is preferable that the two substituents attached are the same, and examples thereof include dimethylamine, diethylamine, dipropylamine, dibutylamine, dicyclohexylamine, diphenylamine and the like.

Generally, light-boiling dialkylamines are often handled as an aqueous solution, but these are dissolved as an aqueous dialkylammonium solution.

Such a dialkylammonium derivative can also be used as the secondary amine of the present invention.

That is, in the production method of the present invention, N, by reacting with a lactone compound in exactly the same manner as in the case of dialkylamine.
An N-dialkyl-substituted-ω-oxycarboxylic acid amide is formed and can be suitably used as a raw material for the production method of the present invention.

In the conventional method for producing an N-alkyl-substituted lactam, the process for producing an N-alkyl-substituted lactam using a lactone compound and a primary amine as a starting material produces an N-alkyl-substituted-ω-hydroxycarboxylic acid amide as an intermediate. Including,
It is known that lactams are produced by dehydration ring closure.

γ-butyrolactone and monoalkylamine (R-NH ₂ )
An example of the above reaction is as follows.

That is, from γ-butyrolactone to N-alkyl-γ-
N-alkyl-2-pyrrolidone can be produced via oxybutyric acid amide.

On the other hand, it has been conventionally known that the reaction between the lactone compound and the secondary amine used in the production method of the present invention produces an N, N-dialkyl-substituted-ω-hydroxycarboxylic acid amide.

This is shown by taking the reaction of γ-butyrolactone and a secondary amine (R ₂ NH) as an example, and the following chemical equation is followed.

In this case, N, N-dialkyl-substituted-ω-hydroxycarboxylic acid amide is produced.

This product has no NH bond to be dehydrated,
In Japanese Patent No. 18751, it is reported that it can be converted into an N-substituted lactam by heating.

In order to elucidate this reaction mechanism, the present inventors have investigated the N, N-
We have conducted a detailed study on the reactivity of dialkyl-substituted-ω-hydroxycarboxylic acid amide compounds, and confirmed that the alcohol was eliminated when heated to a temperature of 250 ° C in the presence of water. Then, it was found that the dealcoholization shown in the following formula occurs to close the ring to form a lactam ring.

Although this dealcohol decomposition reaction proceeds in an aqueous solution, water has a catalytic action, but as shown in the reaction formula, water is not a stoichiometrically essential component for the reaction, and the aqueous solution. The reaction can be carried out without a catalyst in a gas phase or an inert solvent, if not present.

The dealcoholization reaction of the present invention is preferably carried out at a reaction temperature of 240 to 265 ° C. If the reaction temperature is lower than 240 ° C, the reaction hardly progresses, and if it exceeds 265 ° C, by-products are generated due to the successive reaction to lower the purity and the product is colored.

Especially for N-alkyl lactams which have a strict requirement for coloring (APHA) stability, the preferred reaction temperature of the production method of the present invention is
The temperature is about 240 to 265 ° C., and the reaction is carried out in the presence of water in a specific range substantially without catalyst.

In the production method of the present invention, the N, N-dialkyl-substituted acid amide which is an intermediate is usually pyrolyzed in an aqueous solution, which is produced by the reaction of a lactone and a secondary amine. As a preferred embodiment, for example,
A method in which a reaction product of a lactone and a secondary amine is dissolved in water and then thermally decomposed, and a lactone is reacted with an aqueous secondary amine solution (ammonium ionized) to form an N, N-dialkyl-substituted carboxylic acid amide. A method of directly producing an aqueous solution and thermally decomposing it, and a method of carrying out any of the above steps under thermal decomposition conditions can be performed.

The alcohol produced in the dealcoholization decomposition reaction of the present invention is preferably recycled for use in the amine production step by reaction with ammonia. As a result, it is possible to recover most of the loss of the substituent component caused by using the secondary amine.

In the production method of the present invention, N, N-dialkyl substitution-
This is a method of thermally decomposing an ω-oxycarboxylic acid amide, but before the thermal decomposition, a ring-opening addition reaction of a secondary amine or its corresponding ammonium compound to a lactone occurs.

In the present invention, this ring-opening addition reaction can be carried out directly in the system of the final reaction step for forming a lactam ring, or at a stage before the thermal decomposition reaction.

Examples will be shown below by taking as an example the reaction for producing N-methyl-2-pyrrolidone, but this does not limit the present invention.

Many modifications that are obvious to those skilled in the art can be made without departing from the scope of the present invention regarding the conditions of pyrolysis.

Example 1 50 g aqueous solution of dimethylamine in 60 g of γ-butyrolactone 1
25.46 g was mixed at room temperature and reacted for 5 hours. At this time,
The liquid temperature rose to 40 ° C due to the heat of reaction. Excess dimethylamine and water were distilled off, and the resulting colorless residue was subjected to H-NMR.
And ¹³ C-NMR, and represented by the following formula, N, N-dimethyl-γ-hydroxybutyric acid amide Was confirmed.

When this was charged into an autoclave and heated to a temperature of 255 ° C., it was confirmed that N-methyl-2-pyrrolidone and methyl alcohol were produced in 3 hours.

Unreacted N, N-dimethyl compound remained in the reaction solution,
In addition to this, a large amount of N-methyl-γ-oxybutyric acid amide,
It was also confirmed that a small amount of 2-pyrrolidone was produced.

N-methyl-γ-oxybutyric acid amide is an intermediate compound for producing N-methyl-2-pyrrolidone, which is conventionally produced by the reaction of γ-butyrolactone and methylamine (primary amine).

It is presumed that the decomposition of the N, N-dimethyl compound into N-methyl-2-pyrrolidone involves the following two reaction routes.

(Route 1) (Route 2) The yield of N-methyl-2-pyrrolidone was 41.4 g.

Assuming that the total content of N, N-dimethyl compound and N-methyl compound is an effective intermediate for producing N-methyl-2-pyrrolidone, γ-butyrolactone as an active ingredient containing N-methyl-2-pyrrolidone The selectivity of was 99% or more on a molar basis, which was almost quantitative.

The color tone (APHA) of the product after distillation purification was as good as 10.
(See Comparative Example 2 for Distillation Conditions) Example 2 A 500 ml autoclave was charged with 86 g of γ-butyrolactone and 97.2 g of a 50% aqueous solution of dimethylamine, and the temperature was 255 ° C.
The pressure was maintained at 52 kg / cm ² G and the reaction was carried out for 3 hours.

The dimethylamine / lactone molar ratio in this case is 1.15 and the water / lactone molar ratio is 2.7.

When the reaction product liquid was analyzed by liquid chromatography,
The yield of -methyl-2-pyrrolidone was 59.5 g, and amides of methanol, N-methyl form and N, N-dimethyl form were detected, and the composition thereof was almost the same as in Example 1. The product had a purity of 99.9% and a color tone (APHA) of 10.
The content rate of γ-butyrolactone was 0.02%.

Comparative Example 1 By the reaction of γ-butyrolactone and monomethylamine,
N-methyl-gamma-hydroxybutyric acid amide crystals were synthesized. 103 g of the crystals were charged into a 500 ml autoclave and reacted at a temperature of 255 ° C. for 3 hours.

The yield of N-methyl-2-pyrrolidone is 61.8 g,
-The conversion of methyl amide is 75.4% and the selectivity is 9
It was 2.3 mol%.

In the reaction solution, in addition to unreacted N-methylamide compound and water, 4.0% by weight of γ-butyrolactone, 2-pyrrolidone 28.
5 ppm was detected. The product color tone (APHA) was 10.

Comparative Example 2 N-methyl-2-pyrrolidone was produced in the same manner as in Example 2 of the present invention except that the reaction temperature was 270 ° C. (the same temperature as in Example 1 described in JP-B-47-18751).

The yield of the desired product was 81.5 g, the amount of methanol in the reaction solution was large compared to Example 2, and it was confirmed that the residue of the amide compound decreased and the reaction proceeded.

The product solution is deamined, dehydrated and refined by combining three Oldershaw distillation columns to obtain the product N-methyl-2.
-Pyrrolidone is obtained.

In the purification tower, the product was withdrawn from the middle stage, and the bottoms containing the high boiling components were constantly withdrawn from the system.

The chemical purity of the product was 98.5%, and its color tone (APHA) deteriorated to 20. The content rate of γ-butyrolactone in the product was 0.4%.

Comparative Example 3 γ-butyrolactone 1.72 kg (2
0mol), 30% aqueous solution of dimethylamine 3.24kg (23.1mo
l) was charged and reacted at a temperature of 255 ° C. for 3 hours, and then the reaction solution was purified by distillation to produce N-methyl-2-pyrrolidone.

The dimethylamine / lactone molar ratio in this case is 1.15 and the water / lactone molar ratio is 6.3.

The chemical purity of the product was 99.7% and the color tone (APHA) was 10, but the content of γ-butyrolactone increased to 0.23%.

[Effect of the Invention] The present invention provides a novel method for producing a lactam by reacting a lactone with a secondary amine, which has a specific reaction condition as compared with the conventional technique using a reaction with a secondary amine. By adopting this, a lactam having a high selectivity to lactam, a low lactone content in the product, and a good color tone (APHA) can be obtained.

Further, by recycling the by-produced alcohol to the amine production step, the N-alkyl-substituted lactam can be produced without loss of the substance of the substituent due to the use of the secondary amine.

By changing the primary amine to the secondary amine, there is an advantage that the amine, which is one of the starting materials, can be easily obtained and the boiling point is high, so that the safety problem can be greatly improved.

Claims (3)

[Claims] 1. A method for producing an N-alkyl-substituted lactam by reacting a lactone compound with a secondary amine in the presence of water to give an N-alkyl-substituted lactam via an N, N-dialkyl-substituted-ω-hydroxycarboxylic acid amide. And the lactone molar ratio is 3 to
5, and the reaction temperature is 240 to 265 ° C. to dealcoholize to form a lactam ring.
Method for producing alkyl-substituted lactam. 2. A method for producing an N-alkyl-substituted lactam through the reaction of a lactone compound with a secondary amine in the presence of water to give an N, N-dialkyl-substituted-ω-hydroxycarboxylic acid amide, N, N-dialkyl substitution-ω
Heating the hydroxycarboxylic acid amide to a temperature of 240 ° C. or higher to decompose the alcohol to form a lactam ring, separate the eliminated alcohol, and recycle this to the secondary amine production process. A method for producing a characteristic N-alkyl-substituted lactam. 3. The lactone compound is γ-butyrolactone and the N-alkyl-substituted lactam is N-alkyl-substituted-2.
-The process according to claims 1 and 2 which is pyrrolidone.