JP2676105B2 - Method for producing 2,2,6,6-tetramethyl-4-oxopiperidine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing 2,2,6,6-tetramethyl-4-oxopiperidine.

2. Description of the Related Art 2,2,6,6-Tetramethyl-4-oxopiperidine is called triacetoneamine and is useful as an intermediate for the production of stabilizers for polymeric materials and bleaching agents.

Conventionally, as a method for producing this 2,2,6,6-tetramethyl-4-oxopiperidine, a method using various catalysts is known as described in JP-A-63-10761. However, all of them require a long reaction time, and a resinous by-product is produced, so that isolation of the target product is not easy and the reaction yield is not sufficient. Have the problem of.

For example, JP-B-58-30308 discloses that 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine and acetone and // in the presence of a catalyst such as ammonium chloride.
Alternatively, a method of reacting with diacetone alcohol is described. Further, for example, in JP-A-62-132858, acetone or an acidic condensate thereof is reacted with 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine to give 2 A method using halogenated phenols as a catalyst in producing 2,2,6,6-tetramethyl-4-oxopiperidine is described.

The method using ammonium chloride as a catalyst has the advantage that ammonium chloride is inexpensive, but from an industrial point of view, it has a serious drawback in that the reaction device is corroded by chloride ions, while halogenated phenols are used. The method used is still 2,2,6,6-
The yield of tetramethyl-4-oxopiperidine is low.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Therefore, the present inventors have conducted diligent research to solve the above-mentioned problems in the conventional production of 2,2,6,6-tetramethyl-4-oxopiperidine, and as a result, acetone and / Or a method for producing 2,2,6,6-tetramethyl-4-oxopiperidine by reacting the condensate thereof with ammonia, by using nitrophenols or nitronaphthols as a catalyst, the reaction No problem of equipment corrosion and high yield of 2,2,6,6-
The present invention has been accomplished by finding a method by which tetramethyl-4-oxopiperidine can be obtained.

Means for Solving the Problems The method for producing 2,2,6,6-tetramethyl-4-oxopiperidine according to the present invention comprises reacting acetone and / or a condensate of acetone with ammonia to give 2,2, In the method for producing 6,6-tetramethyl-4-oxopiperidine, nitrophenols or nitronaphthols are used as a catalyst.

The starting material in the method of the present invention is acetone and / or a condensate thereof, and the condensate includes, for example, mesyl oxide, diacetone alcohol, and holone.

More specifically, the method of the present invention comprises reacting acetone and / or a condensate thereof in a solvent with ammonia in the presence of a catalyst to obtain 2,2,4,4,6-pentamethyl-2,
3,4,5-Tetrahydropyrimidine is produced, then
As a reaction in the latter stage, the produced 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine was heated with acetone to obtain the desired 2,2,6,6-tetramethyl- This gives 4-oxopiperidine.

First, in the reaction of the first stage, acetone can be used as a solvent in excess and can be used as a solvent, but a lower aliphatic alcohol such as methanol or ethanol can also be used as a solvent. A mixture of acetone and these alcohols may be used as the solvent. The amount of the solvent is not particularly limited, but is in the range of 1 to 10, preferably 3 to 5 in weight ratio of acetone or its condensate to the solvent.

The amount of ammonia used is in the range of 3 to 20 times mol, preferably 5 to 10 times mol of acetone and / or its condensate with respect to ammonia. Ammonia is usually
It is blown into acetone and / or its condensate.

In the method of the present invention, nitrophenols or nitronaphthols are used as the catalyst. Examples of such catalysts include p-nitrophenol, o-nitrophenol, m-nitrophenol, 4-nitro-m.
-Cresol, 2,4-dinitrophenol, 2,4-dinitronaphthol and the like can be mentioned. Such a catalyst is
It is used in the range of 0.1 to 30 mol%, preferably 1 to 10 mol%, based on the starting material acetone and / or its condensate.

The reaction in the first stage is usually carried out by blowing ammonia into acetone and / or its condensate at a temperature of 0 to 100 ° C for 1 to 10 hours, preferably at a temperature of 20 to 60 ° C for 2 to 5 hours. Done. Then, after stopping the blowing of ammonia, the reaction mixture is heated at a temperature of 50 to 120 ° C. for 1 to 20 hours, preferably at a temperature of 60 to 100 ° C. for 2 to 5 hours. Done. The reaction in both the front and rear stages is usually carried out under normal pressure, but if necessary, it may be carried out under a pressure of up to 10 kg / cm ² , preferably up to 5 kg / cm ² .

After completion of the reaction, for example, by distilling the reaction mixture, highly pure 2,2,6,6-tetramethyl-4-oxopiperidine can be obtained in a high yield.

Effects of the Invention In the method of the present invention, since nitrophenols or nitronaphthols are used as the catalyst, unlike the method using a halide such as ammonium chloride,
It is possible to obtain 2,2,6,6-tetramethyl-4-oxopiperidine in a higher yield on the basis of acetone without fear of corrosion of the apparatus.

EXAMPLES Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 Acetone 58.1 g (1 mol), p-nitrophenol 4.2
25 in a mixture consisting of g (0.03 mol) and 28.6 g of methanol.
2.4 g (0.14 mol) of ammonia was blown in at 0 ° C. for 1 hour. After this, the reaction mixture was heated to reflux for 5 hours.

After adding sodium hydroxide in an equimolar amount to p-nitrophenol to the reaction mixture as an aqueous solution, the result of the analysis by gas chromatography showed 2,2,6,6-tetramethyl-
It was found that the amount of 4-oxopiperidine produced was 14.6 g. The yield based on the used ammonia was 67%, and the yield based on the consumed acetone was 68%.

Examples 2 to 6 In Example 1, instead of p-nitrophenol,
A reaction was carried out in the same manner as in Example 1 except that the nitrophenols or nitronaphthols shown in Table 1 were used,
2,2,6,6-Tetramethyl-4-oxopiperidine was obtained. The yields based on the ammonia used and the acetone consumed are shown in Table 1, respectively.

Comparative Example 1 In Example 1, instead of p-nitrophenol,
The reaction was performed in the same manner as in Example 1 except that 1.6 g of ammonium chloride was used to obtain 13.1 g of 2,2,6,6-tetramethyl-4-oxopiperidine. The yield based on the used ammonia was 60%, and the yield based on the consumed acetone was 59%.

Comparative Example 2 In Example 1, instead of p-nitrophenol,
Example 1 except that 8.0 g of pentachlorophenol was used.
And 2,2,6,6-tetramethyl-4
12.3 g of -oxopiperidine were obtained. The yield based on the used ammonia is 56%, and the yield based on the consumed acetone is
It was 60%.

Claims (1)

(57) [Claims] 1. A reaction of acetone and / or a condensate of acetone with ammonia to form 2,2,6,6-tetramethyl-4-.
A method for producing 2,2,6,6-tetramethyl-4-oxopiperidine, which comprises using nitrophenols or nitronaphthols as a catalyst in the method for producing oxopiperidine.