JPH06184008A - Production of 2,3-dimethylnaphthalene and intermediate therefor - Google Patents

Abstract

PURPOSE:To inexpensively mass produce 2,3-dimethylnaphthalene useful as a synthetic intermediate for 2,3-naphthalenedicarboxylic acid, etc., from 6- methyl-1,2,3,4-tetrahydronaphthalene industrially obtainable in a large amount. CONSTITUTION:6-Methyl-1,2,3,4-tetrahydronaphthalene is made to react with formaldehyde and a hydrogen halide in the presence of an acid catalyst, the prepared 6-halomethyl-7-methyl-1,2,3,4-tetrahydronaphthalene is hydrogenated and then the prepared 6,7-dimethyl-1,2,3,4-tetrahydronaphthalene is dehydrogenated to produce 2,3-dimethylnaphthalene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing 2,3-dimethylnaphthalene, which is useful as a raw material for 2,3-naphthalenedicarboxylic acid, which is important as a raw material for synthesizing weather-resistant pigments and dyes.

[0002]

2. Description of the Related Art 2,3-Naphthalenedicarboxylic acid, which is a derivative of 2,3-dimethylnaphthalene, is a compound attracting attention as an intermediate for dyes, pigments and the like, and many proposals have been made for its synthesis method. (For example, JP-A-61-1
No. 194048, No. 61-221151, etc.). All of these methods for synthesizing 2,3-naphthalenedicarboxylic acid utilize liquid-phase air oxidation of 2,3-dimethylnaphthalene, and the yield is good. However, 2,3-dimethylnaphthalene used in these synthetic methods has hitherto been dependent on separation and recovery from coal tar fractions and petroleum fractions, and the dimethylnaphthalene content in these fractions is as low as 10 or. The difficulty of separation from climbing dimethylnaphthalene isomers makes these synthetic methods difficult to carry out. Under such circumstances, the production of 2,3-naphthalenedicarboxylic acid relies on a method of separating and recovering a small amount of by-products obtained during the anthraquinone synthesis by the oxidation of anthracene, and it is difficult to supply a large amount thereof.

[0003]

Therefore, an object of the present invention is to provide a method for producing 2,3-dimethylnaphthalene, which is useful as a synthetic intermediate for 2,3-naphthalenedicarboxylic acid, selectively, inexpensively and in large quantities. To provide.

[0004]

Under these circumstances, the present inventor has conducted extensive studies on a selective method for producing 2,3-dimethylnaphthalene, and as a result, 6-methyl-1, which is industrially easily available in large quantities, By using 2,3,4-tetrahydronaphthalene as a raw material and reacting it with formaldehyde and hydrogen halide in the presence of an acid catalyst, a 7-position halomethylated product is selectively obtained, and the halomethylated product is dehalogenated and dehydrated. It has been found that 2,3-dimethylnaphthalene can be efficiently obtained by priming, and the present invention has been completed.

The method of the present invention is represented by the following reaction formula.

[0006]

[Chemical 1]

That is, the present invention provides 6-methyl-1,2,
Novel 6-halomethyl-7-methyl-1, obtained by reacting 3,4-tetrahydronaphthalene with formaldehyde and hydrogen halide in the presence of an acid catalyst
Hydrogenating 2,3,4-tetrahydronaphthalene and subjecting the resulting 6,7-dimethyl-1,2,3,4-tetrahydronaphthalene to a dehydrogenation reaction 2,3
-A method for producing dimethylnaphthalene.

The present invention is also useful as a production intermediate.
-Halomethyl-7-methyl-1,2,3,4-tetrahydronaphthalene.

Each step of the above reaction formula will be described. First, from 6-methyl-1,2,3,4-tetrahydronaphthalene to 6-halomethyl-7-methyl-1,2,3,4
The step of obtaining tetrahydronaphthalene is an aromatic halomethylation reaction and is carried out by reacting formaldehyde and hydrogen halide in the presence of an acid catalyst.

The formaldehyde used in the reaction can be carried out even if introduced as a gas, but it is preferable to use a polymer such as paraformaldehyde or trioxane because the operation is easy. As hydrogen halide, hydrogen chloride,
Examples thereof include hydrogen bromide, and these can be used in the form of hydrochloric acid or hydrobromic acid. As the acid catalyst, either a protic acid or a Lewis acid can be used, and it is preferable to select and use any one depending on the reaction solvent used. For example, in the case of an acetic acid solvent, it is preferable to use a protonic acid such as phosphoric acid or sulfuric acid as a catalyst, and when a solvent such as chloroform or dichloromethane is used, a Lewis acid such as zinc chloride or tin chloride can also be used as a catalyst.

The reaction is usually carried out at about 20 to 100 ° C. under normal pressure.
Although it can be carried out at a temperature not higher than the boiling point of the solvent, the range of 40 to 60 ° C. is preferable from the viewpoint of shortening the reaction time and preventing side reactions and overreactions. The reaction time is preferably 3 to 10 hours. 6-halomethyl-7-methyl-obtained by this reaction
If necessary, 1,2,3,4-tetrahydronaphthalene can be purified by distillation, and can be easily separated by chromatography. In addition, the 6-halomethyl-7-methyl-1,2,3,4-tetrahydronaphthalene is a novel compound not described in the literature.

6-halomethyl-7-methyl-1,2,
As the hydrogenation reaction of 3,4-tetrahydronaphthalene, a hydrogenation reaction using an ordinary metal catalyst can be adopted. For example, in the presence or absence of a solvent, a hydrogen atmosphere of atmospheric pressure to 5 atm is used using the metal catalyst. Done in. The metal catalyst is not particularly limited as long as it is a group VIII metal or a group VIII metal supported on a non-acidic carrier, and as the group VIII metal, platinum, palladium, nickel, etc. are used as the non-acidic carrier. Activated carbon, barium sulfate, silica acidified with alkali,
Alumina can be used. As a more specific example, in the case of a palladium catalyst, for example, 5% palladium-carbon is preferably used in an amount of 3 to 20% by weight based on the substrate. The solvent is not particularly limited as long as it is a neutral organic solvent, but methanol, ethyl acetate and the like are preferable in view of reaction rate, solubility, stability and the like. In addition, 1 equivalent of potassium carbonate in the reaction system,
The coexistence of a base such as sodium carbonate, sodium hydroxide or potassium hydroxide is preferable in order to carry out the reaction at a low temperature, and the reaction temperature is preferably 0 to 30 ° C. in the presence of a base. In the absence of a base, a high temperature of 100 ° C. or higher is required. In this case, however, the condition can be changed from the hydrogen atmosphere to the nitrogen atmosphere at the end of the reaction so that the dehydrogenation step can be continued. In any case, the reaction time is preferably 1 to 10 hours. The 6,7-dimethyl-1,2,3,4-tetrahydronaphthalene obtained in the hydrocracking step is
After removing the catalyst by filtration, it can be purified by distillation.In the case of a small amount of synthesis, the amount is small if dissolved in a water-insoluble organic solvent, washed with water to remove the inorganic salt and base, and distilled off the solvent. However, the entire amount can be recovered.

The dehydrogenation reaction of 6,7-dimethyl-1,2,3,4-tetrahydronaphthalene is carried out by a conventional method, for example, using a transition metal catalyst such as a noble metal such as palladium,
It can be carried out at a temperature of 150 to 400 ° C. in the presence or absence of a solvent, as well as in the absence of a catalyst and a solvent using 1 equivalent or more of sulfur. Reaction temperature is 150 to 20
The range of 0 ° C. is preferable, and particularly when a noble metal catalyst is used, a temperature of 250 ° C. or higher is not preferable because an isomerization reaction occurs at a high temperature. Generally, the reaction time is preferably 3 to 10 hours. After the reaction, in the case of a catalytic reaction, the catalyst is removed by filtration, and when sulfur is used, the target white crystals of 2,3-dimethylnaphthalene can be obtained by carrying out distillation after washing with water.

The method for producing 6-methyl-1,2,3,4-tetrahydronaphthalene, which is the starting material compound of the present invention, is not particularly limited, but as a general method, it is abundant in petroleum fractions. The method by hydrogenation of 2-methylnaphthalene is simple. In this method, 6-methyl-1,
2-Methyl-1,2,3,4-tetrahydronaphthalene is formed together with 2,3,4-tetrahydronaphthalene, which can be easily separated by distillation.

[0015]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1 1.96 g (13.4 mmol) of 6-methyl-1,2,3,4-tetrahydronaphthalene was added to 4.5 ml of acetic acid, 3.0
ml 85% phosphoric acid, 5.5 ml concentrated hydrochloric acid, 823 mg paraformaldehyde (27.4 mm as formaldehyde)
ol) was put into a flask and reacted at 90 ° C. for 6 hours. After the reaction, add 30 ml of ethyl acetate and wash with water.
After dehydration using anhydrous magnesium sulfate, ethyl acetate was distilled off and the obtained white solid was separated by silica gel column chromatography to give 6-chloromethyl-
1.07 g of a chloromethylated compound containing 7-methyl-1,2,3,4-tetrahydronaphthalene as a main component was obtained,
792 mg of unreacted raw material was recovered (conversion rate 60%, selectivity 91%). ¹ H-NMR (CDCl ₃ , TMS standard, 90 MHz) δ (ppm): 1.55 to 1.98 (4H, m, -CH ₂ C H ₂ C H ₂ CH _2- ) 2.29, 2.37, 2.40 (3H, each s, Aromatic hydrogen) 2.50 ~ 3.00 (4H, m, -C H ₂ CH ₂ CH ₂ C H _2- ) 4.56, 4.65, 4.74 (2H, each s, -C H ₂ Cl) 6.75 ~ 7.15 (2H, m, Aromatic hydrogen)

Example 2 In a 100 ml four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a gas introduction tube, 6-methyl-1,2,
2.01 g of 3,4-tetrahydronaphthalene (13.7
mmol), 831 mg of paraformaldehyde (27.7 mmol as formaldehyde), 1.03 g of zinc chloride and 50 ml of chloroform were added, and the reaction was carried out at 60 ° C. for 5 hours while introducing hydrogen chloride gas at a rate of 10 ml / min with stirring. . After the reaction, the chloroform solution was washed with water, dehydrated with anhydrous sodium sulfate, filtered, and then chloroform was distilled off, followed by separation by silica gel column chromatography to find that 6-chloromethyl-7-methyl-
1.12 g of a chloromethylated product containing 1,2,3,4-tetrahydronaphthalene as a main component was obtained, and unreacted raw material 6
78 mg was recovered (66% conversion, 95% selectivity).

Example 3 1.00 g of the chloromethylated product obtained in Example 1 (5.
14 mmol) 5% palladium-carbon 30 mg and anhydrous sodium carbonate 270 mg (2.55 mmol), methanol 20
It was put in a flask together with ml and stirred at room temperature for 1 hour under a hydrogen atmosphere at atmospheric pressure. After removing the catalyst by filtration,
After adding 100 ml of n-hexane and removing inorganic salts by washing with water, dehydration was performed using anhydrous magnesium sulfate, hexane was distilled off, and 818 mg (99%) of colorless liquid dimethyl-1,2,3,4-tetrahydronaphthalene. ) Got. The obtained dimethyl-1,2,3,4-tetrahydronaphthalene was analyzed by gas chromatography, and as a result, 6,7-dimethyl-1,2,3,4-tetrahydronaphthalene was produced with a selectivity of 75%. Was confirmed.

Example 4 6,7-Dimethyl-1,2,3,4 obtained in Example 3
-Tetrahydronaphthalene (510 mg) was put in a flask equipped with a reflux condenser together with 10% palladium-carbon (50 mg), and the mixture was stirred at 220 ° C for 10 hours in a nitrogen stream. After the reaction, the mixture was left to cool to room temperature, the solidified product was dissolved in n-hexane, the catalyst was removed by filtration, and then n-hexane was distilled off to obtain 490 mg of white crystals. As a result of analyzing the crystals by gas chromatography, dimethyltetralin (raw material) 23%, dimethylnaphthalene 77%, and
The content of 2,3-dimethylnaphthalene in dimethylnaphthalene was 75%, and the total of other isomers was 25% (conversion rate 77
%, Selectivity over 99%).

[0020]

INDUSTRIAL APPLICABILITY According to the present invention, 6,3-dimethyl-naphthalene, which is useful as a synthetic intermediate for 2,3-naphthalenedicarboxylic acid and the like, is industrially easily available in large quantities in 6-methyl-
Selective from 1,2,3,4-tetrahydronaphthalene,
And it is cheap and can be manufactured in large quantities.

[Brief description of drawings]

FIG. 1 6-chloromethyl-7-methyl-of Example 1
1,2,3,4-tetrahydronaphthalene-containing product
It is a figure which shows a < ¹ > H-NMR spectrum.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C07C 22/04 9280-4H // C07B 61/00 300 (72) Inventor Ryo Tanaka Satte City, Saitama Prefecture Gonendo 1134-2 Cosmo Research Institute R & D Center (72) Inventor Toshio Shimizu Gongen 1134-2, Saitama Prefecture Cosmo Research R & D Center

Claims (3)

[Claims] 1. 6-halomethyl-7-methyl-1,2,
A method for producing 2,3-dimethylnaphthalene, which comprises hydrogenating 3,4-tetrahydronaphthalene and subjecting the obtained 6,7-dimethyl-1,2,3,4-tetrahydronaphthalene to a dehydrogenation reaction. 2. 6-Halomethyl-7-methyl-1,2, obtained by reacting 6-methyl-1,2,3,4-tetrahydronaphthalene with formaldehyde and hydrogen halide in the presence of an acid catalyst. Hydrogenation of 3,4-tetrahydronaphthalene, then the resulting 6,7-dimethyl-1,
A method for producing 2,3-dimethylnaphthalene, which comprises subjecting 2,3,4-tetrahydronaphthalene to a dehydrogenation reaction. 3. 6-halomethyl-7-methyl-1,2,
3,4-tetrahydronaphthalene.