JPH0681735B2 - Method for producing 2-alkyl-6-acylnaphthalene - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing 2-alkyl-6-acylnaphthalene, more specifically, it is acylated in the presence of trifluoromethanesulfonic acid, 2-alkyl
And a method for producing 6-acylnaphthalene.

[Prior Art] Conventionally, 2-alkylnaphthalene is reacted with an acylating agent,
The following are known methods for producing 2-alkyl-6-acylnaphthalene.

One is to use a Friedel-Crafts catalyst such as aluminum chloride or iron chloride in the above reaction (US Pat. No. 3,234,286, JP-A-61-2675).
38, JP-A-62-61944).

The other one is to carry out the above reaction in the presence of boron trifluoride, or boron trifluoride and hydrogen fluoride (JP-A-54-135756, JP-A-61-218553). , JP-A-61
-271243, JP 61-277643, JP 62-486
43 publication).

However, in the former case, the amount of the catalyst needs to be 1 mol of the catalyst with respect to 1 mol of the product, and since these catalysts are difficult to recover, a large amount of the catalyst is thrown away, which is not economical. was there. On the other hand, in the latter case, when an acid fluoride is used as the acylating agent, some selectivity is obtained, but when acetic acid is used as the acylating agent, the selectivity of 2-alkyl-6-acylnaphthalene is increased. There was a problem that it was low.

[Problems to be Solved by the Invention] Under the circumstances, the present invention provides a high yield of 2-alkylnaphthalene, as well as other acylating agents, even when acetic acid is used as the acylating agent, and 2-alkyl with high selectivity
The purpose of the present invention is to provide a method for producing -6-acylnaphthalene.

[Means for Solving the Problems] As a result of intensive studies to achieve the above-mentioned object, the present inventors have achieved the purpose by acylating 2-alkylnaphthalene in the presence of a specific catalyst. Based on this finding, the present invention has been completed.

That is, the present invention is characterized by using trifluoromethanesulfonic acid as a catalyst in a method for producing a 2-alkyl-6-acylnaphthalene by reacting a 2-alkylnaphthalene and an acylating agent in the presence of a catalyst. Is a method for producing 2-alkyl-6-acylnaphthalene.

In the present invention, 2-alkylnaphthalene is used as a raw material. As the 2-alkylnaphthalene, all naphthalene derivatives in which the 2-position is substituted with an alkyl group or a cycloalkyl group can be used. Specific examples of 2-alkylnaphthalene include, for example, 2-methylnaphthalene,
2-ethylnaphthalene, 2-npropylnaphthalene, 2-isopropylnaphthalene, 2-nbutylnaphthalene, 2-isobutylnaphthalene, 2-sec butylnaphthalene, 2-tertbutylnaphthalene, 2-npentylnaphthalene, 2-isopentylnaphthalene , 2-amylnaphthalene, 2-n-hexylnaphthalene, 2-cyclopentylnaphthalene, 2-cyclohexylnaphthalene and the like. These 2-alkylnaphthalenes may be used alone or in combination of two or more.

The acylating agent used in the present invention is not particularly limited as long as it can be acylated. Examples of the acylating agent include carboxylic acid, acid anhydride, acid halide, ketene, and carboxylic acid ester.

The acid anhydride is preferable because it produces less water than the carboxylic acid, and a high conversion can be obtained with a small amount of catalyst.

Specific examples of the acylating agent include, for example, acetic acid, propionic acid, butyric acid, isobutyric acid, acetic anhydride, propionic anhydride, butyric anhydride, acetyl fluoride, propion fluoride, butyl fluoride, phenyl propion fluoride, triethyl chloride. Propion fluoride, acetyl chloride, propionyl chloride, butyryl chloride, phenylpropionyl chloride, acetyl bromide, propionyl bromide, acetyl iodide,
Propionyl iodide, methyl acetate, ethyl acetate,
Propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate,
Propyl butyrate and the like can be used. These acylating agents may be used alone or in combination of two or more.

The amount of the acylating agent used is usually in the range of 1 to 10 mol, preferably 1.2 to 2 mol, per 1 mol of the 2-alkylnaphthalene. If the proportion of acylating agent used is low, the conversion rate of 2-alkylnaphthalene will decrease,
If the proportion of the acylating agent used is too large, the selectivity of 2-alkyl-6-acylnaphthalene is lowered.

In the present invention, the 2-alkylnaphthalene is reacted with the acylating agent in the presence of trifluoromethanesulfonic acid.

The amount of trifluoromethanesulfonic acid used is usually in the range of 2 to 50 mol, preferably 2 to 20 mol, per 1 mol of 2-alkylnaphthalene. If the amount of trifluoromethane sulfonic acid used is low, the conversion rate of 2-alkylnaphthalene will decrease, and if the amount of trifluoromethane sulfonic acid used is too high, the catalyst efficiency will decrease and heat generated in the product separation step will occur. growing.

The method for adding the 2-alkylnaphthalene as the raw material of the present invention and the acylating agent, and the method for adding the trifluoromethanesulfonic acid as the catalyst of the present invention are not particularly limited, and various methods and procedures can be used.

In the present invention, the above raw materials are reacted in the presence of the above catalyst.
The conditions of this reaction may be appropriately determined depending on the type of raw material.

The reaction temperature is not particularly limited and is usually −20 to 10
It is in the range of 0 ° C, and preferably in the range of -10 to 80 ° C. If the reaction temperature is too low, the reaction temperature is slow, and if the reaction temperature is too high, a polymer is formed, which is not preferable.

The reaction time is not particularly limited and is usually 10 minutes to
It is done in the range of 10 hours.

In the present invention, it is not necessary to use a catalyst, but it is preferable to use a solvent because the product can be easily separated. Examples of usable catalysts include halogenated hydrocarbons such as methylene chloride and carbon tetrachloride, carbon sulfides such as carbon disulfide, aromatic hydrocarbons such as benzene that are difficult to react, nitro compounds such as nitrobenzene, nitromethane, nitroethane, and nitropropane. And halogenated aromatic compounds such as chlorobenzene.

The amount of the catalyst used is usually in the range of 1 to 100 g, preferably in the range of 5 to 50 g, per 1 g of 2-alkylnaphthalene.

In the present invention, the reaction product containing 2-alkyl-6-acylnaphthalene can be obtained by reacting by the above method. In this reaction product, 2-alkyl-6-acylnaphthalene forms a complex with trifluoromethanesulfonic acid, so in order to take out 2-alkyl-6-acylnaphthalene alone, this complex is decomposed. There is a need. Decomposition of this complex can be usually performed by adding water, ammonia gas or the like. The amount of water added is
It is usually in the range of 10 to 100 times the weight of the catalyst.

2-Alkyl-6-acylnaphthalene obtained by decomposing the complex can be separated and purified by a known method.

When water is added to decompose the complex, the trifluoromethanesulfonic acid obtained by decomposition is present as an aqueous solution. This trifluoromethanesulfonic acid can be recovered from the aqueous solution and used as a catalyst for the reaction of the present invention for acylating a 2-alkylnaphthalene.

As a method for recovering trifluoromethanesulfonic acid from an aqueous solution containing trifluoromethanesulfonic acid, for example, the aqueous solution is heated under reduced pressure to remove water as much as possible, and then 100% sulfuric acid or fuming sulfuric acid is added and distilled to remove trifluoromethane. There is a method of obtaining methane sulfonic acid.

Thus, the recovered trifluoromethanesulfonic acid can be used as a catalyst in the reaction of the present invention any number of times.

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

Example 1 5.0 g of 2-methylnaphthalene was dissolved in 40 g of benzene, and 25 g of trifluoromethanesulfonic acid was added. 2.5 g of acetic acid was gradually added while heating the solution to 60 ° C., and the mixture was stirred for 5 hours.
The reaction mixture was poured into ice water to decompose the catalyst and product,
The product was analyzed by gas chromatography. The conversion rate is
97%, the selectivity of 2-methyl-6-acetylphthalene was 88%.

Comparative Example 1 The reaction was performed in the same manner as in Example 1 except that 25 g of methanesulfonic acid was used as the catalyst, and no formation of an acetylated product was observed.

Comparative Example 2 In a 200 cc autoclave, 2-methylnaphthalene 5.0
g, benzene 40 g, acetic acid 2.5 g, HF ₅ g, BF ₃ 10 g, 11
When the reaction was carried out at ℃, the conversion was 99% and the selectivity of 2-methyl-6-acetylnaphthalene was 25%.

Example 2 500 ml of the trifluoromethanesulfonic acid aqueous solution obtained in Example 1 was heated at 60 ° C. under reduced pressure to remove water. 100% concentrated sulfuric acid was added to the obtained CF ₃ SO ₃ H · H ₂ O and distilled to 33 m.
23 g of a fraction having mHg of 110 to 113 ° C. was obtained. When this was used as a catalyst and a reaction was carried out in the same manner as in Example 1, the conversion was 96.
%, The selectivity of 2-methyl-6-acetylnaphthalene was 88%.

Example 3 2-alkylnaphthalene 6.0 g of 2-isopropylnaphthalene
The same reaction as in Example 1 was carried out except that The conversion was 98% and the selectivity of 2-isopropyl-6-acetylphthalene was 90%.

Example 4 10.0 g of 2-methylnaphthalene was dissolved in 40 g of benzene, and the solution was heated to 0 ° C.
After cooling to 25 g of trifluoromethanesulfonic acid was added. While keeping the solution at 0 ° C., 4.6 g of acetic anhydride was gradually added and stirred for 3 hours. When analyzed in the same manner as in Example 1 below, the conversion was 75% and the selectivity for 2-methyl-6-acetylnaphthalene was 87%.

[Effect of the Invention] As described above, according to the configuration of the present invention, 2-alkyl-6-acylnaphthalene can be obtained from 2-alkylnaphthalene with high selectivity and high yield. The catalyst used in the reaction of the present invention can be recovered by a simple method, and the recovered catalyst can be used in the reaction of the present invention any number of times. This is an extremely advantageous method as an industrial production method for 6-acylnaphthalene. The 2-alkyl-6-acylnaphthalene produced by the present invention can be used as an intermediate of a raw material of polyester used for magnetic tapes and the like.

Claims (3)

[Claims] 1. A method for producing a 2-alkyl-6-acylnaphthalene by reacting a 2-alkylnaphthalene with an acylating agent in the presence of a catalyst, wherein trifluoromethanesulfonic acid is used as the catalyst. 2-alkyl-6
-Method for producing acylnaphthalene. 2. The method according to claim 1, wherein the acylating agent is acetic acid or acetic anhydride. 3. The method according to claim 1, wherein the trifluoromethanesulfonic acid is recovered from a reaction product obtained by reacting a 2-alkylnaphthalene with an acylating agent in the presence of trifluoromethanesulfonic acid.