JPH08268990A - Production of 7-methyl-2-naphthalenecarbonitrile - Google Patents

Abstract

PURPOSE: To suppress side reactions, enable the obtaining of the objective substance in high selectivity per conversion rate of a starting substance and efficiently produce the objective substance at a low material cost by nearly completely recovering the unreacted starting substance for reuse. CONSTITUTION: This method for producing 7-methyl-2-naphthalenecarbonitrile comprises reacting (a) 2,7-dimethylnaphthalene with N-bromosuccinimide so as to provide 20-80mol% conversion rate, providing 7-methyl-2- bromomethylnaphthalene, (b) then reacting the resultant 7-methyl-2- bromomethylnaphthalene with hexamethylenetetramine, affording 7-methyl-2- naphthalenecarbaldehyde and further (c) converting the prepared compound into a nitrile with hydroxylamine. The unreacted substance and by-products are separated from the objective substance simply by distillation after the step (c) to reuse the unreated 2,7-dimethylnaphthalene in the step (a).

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 7-methyl-2-naphthalenecarbonitrile (hereinafter abbreviated as "MNCN"), which has recently become more useful as an intermediate for medicines and agricultural chemicals. An example of the synthesis of useful compounds using MNCN is
For example, it is described in JP-A-5-78344 and 5-208946.

[0002]

BACKGROUND ART There are few synthetic examples of MNCN, and a method of reacting sodium 2-methyl-7-naphthalenesulfonate with potassium cyanide (PH Gore et al., J. Chem. Soc.,
Perkin Trans. I, 1972 , 1781) and 7-methyl-2-
A method in which naphthalenecarboxylic acid is reacted with thionyl chloride to give a chloride, and then reacted with concentrated aqueous ammonia to form 7-methyl-2-naphthalenecarboxamide, which is reacted with triphenylphosphine (JP-A-5-78).
No. 344 and No. 5-208946). In these conventional methods, starting materials are difficult to obtain, the former uses highly poisonous potassium cyanide in the reaction, and the latter has complicated steps, so that none of them is suitable for industrialization.

[0003]

DISCLOSURE OF THE INVENTION The object of the present invention is to produce MNCN from a relatively easily available starting material in a simple process at low cost and safely, and therefore to be suitable for industrialization.
It is to provide a manufacturing method of N.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have found that 2,7-dimethylnaphthalene (hereinafter,
As a result of studying the synthesis of MNCN starting from (2,7-DMN) as a starting material, a new method suitable for industrially producing MNCN at low cost was found, and the present invention was accomplished.

The present invention consists of the following steps (a) to (c):
It is a method for producing methyl-2-naphthalenecarbonitrile (MNCN). (a) a step of reacting 2,7-dimethylnaphthalene (2,7-DMN) with a halogenating agent to monohalogenate, (b) oxidizing the obtained 7-methyl-2-halogenomethylnaphthalene, A step of converting a halogenomethyl group into a carbaldehyde group, and (c) a step of nitrileing the obtained 7-methyl-2-naphthalenecarbaldehyde to obtain MNCN. The reaction route in the method for producing MNCN of the present invention is shown below.

[0006]

Embedded image

The starting material, 2,7-DMN, has a melting point of 98.
It is a crystalline substance with a boiling point of 262 ° C at atmospheric pressure and atmospheric pressure of 262 ° C. It can be produced by separation from petroleum fractions, alkylation or transalkylation of naphthalene or methylnaphthalene, isomerization of dimethylnaphthalene, and cyclization of alkylbenzene. it can. In the present invention, 2,7-DMN produced by any method can be used. The purity of 2,7-DMN is not particularly limited, but usually 90% by weight or more is preferable.

In step (a), 2,7-DMN is reacted with a halogenating agent to monohalogenate to produce 7-methyl-2-halogenomethylnaphthalene. If only one methyl group of 2,7-DMN can be dihalogenated by reaction with a halogenating agent, in the next step (b), the dihalogenomethyl group can be converted to an aldehyde group only by hydrolysis, so the reaction is simple. become. However, when 2,7-DMN is dihalogenated, the main product is 2,7-di (halogenomethyl) naphthalene in which both methyl groups are monohalogenated, and only one methyl group is dihalogenated in 7- Methyl-2-
It was found that the selectivity of dihalogenomethylnaphthalene was very low. Therefore, it is monohalogenated to halogenate only one methyl group.
(-CH ₂ X) is converted to a carbonitrile group (-CN) via a carbaldehyde group (-CHO).

The monohalogenation may be any of chlorination, bromination and iodination, but bromination is preferred because of its excellent selectivity. As the halogenating agent, any halogenating agent that can be used for halogenating an aromatic side chain alkyl group can be used. Examples thereof include halogens such as chlorine, bromine and iodine, N-bromosuccinimide (NBS) and N.
-Halogenated succinimides such as chlorosuccinimide and sulfuryl chloride. Bromination with NBS is particularly preferable in terms of reaction yield.

The reaction of 2,7-DMN with a halogenating agent is
Solvent (eg carbon tetrachloride, methylene chloride, ethylene chloride, ethylene dichloride, cyclohexane, benzene, etc.)
In the presence or absence of a radical generator (for example,
It can be carried out in the presence or absence of a peroxide, an azo compound, ultraviolet rays, etc.). Depending on the type of halogenating agent or the presence or absence of solvent or radical generator,
The reaction temperature is generally 0 ° C or higher and 200 ° C or lower, preferably 50 ° C.
The temperature is above ℃ and below 120 ℃.
Complete within hours, usually within 4 hours.

As the amount of halogenating agent (eg, NBS) used increases, the conversion of 2,7-DMN improves, but as shown in FIG. 1, as the conversion of 2,7-DMN increases, Dihalide (eg 2,7-dibromomethylnaphthalene)
The amount of by-products is increased and the selectivity of monohalide (eg, 7-methyl-2-bromomethylnaphthalene) is decreased.
Although it is much easier to obtain than the starting material used in the conventional method, 2,7-DMN is the most expensive material used,
The yield of the target product per 2,7-DMN conversion rate is a major factor that determines the economic efficiency of the MNCN production method of the present invention.

Therefore, if the unreacted 2,7-DMN is to be recovered and reused, the conversion of 2,7-DMN is kept low to suppress the dihalogenation, and the consumption per 2,7-DMN is reduced. It is advantageous to increase the selectivity of the monohalide. In this case, the lower the conversion rate, the better the selectivity, which is advantageous from the basic unit, but from the viewpoint of productivity, the extremely low conversion rate is disadvantageous. In that sense, the conversion of 2,7-DMN is 10 to 90% (depending on the reaction conditions), preferably 20.
Within 80%. When NBS is used as the halogenating agent, a selectivity of about 80 to 90% can be obtained at a conversion of 60%.

On the other hand, when the unreacted 2,7-DMN is not recovered and reused, it is desirable to select the conversion rate of 2,7-DMN that maximizes the yield of the monohalide. Although depending on the reaction conditions, such a conversion of 2,7-DMN is generally 40% or more, preferably 60 to 90%,
It is particularly preferably 70 to 85%.

Considering that 2,7-DMN is relatively expensive as described above, the conversion rate of 2,7-DMN is 20 to 20%.
80%, dihalogenation is suppressed and unreacted 2,7-D
It is economically advantageous to recover the MN and reuse it in step (a). The amount of halogenating agent used in this case is NBS.
In this case, it is usually preferable that the stoichiometric amount is 1/5 or more of the stoichiometric amount required for monohalogenation of 2,7-DMN.

The reaction mixture obtained in step (a) contains, in addition to the desired monohalide, unreacted 2,7-DMN and a small amount of dihalide produced as a side reaction. Since the target product, 7-methyl-2-halogenomethylnaphthalene, has a halogen at the benzyl position, it is unstable to heat, acids, alkalis, metals and the like. Therefore, isolating the product at this stage by techniques such as vacuum distillation
It is not a good idea because it tends to cause decomposition of the product. Therefore, the product is not separated from unreacted 2,7-DMN and by-product dihalide, and after removing the halogenating agent, solvent, etc. as necessary, it is directly used in the reaction of the next step (b). It is preferable.

In step (b), 7-methyl-2-halogenomethylnaphthalene is oxidized to convert the 2-position halogenomethyl group into a carbaldehyde group (-CHO group). This oxidation can be carried out by any method capable of converting the halogenomethyl group attached to the aromatic ring into a carbaldehyde group. A typical example is a method of reacting with hexamethylenetetramine according to the following Sommelet reaction, but a method of oxidizing with an amine oxide (eg, pyridine N-oxide, trimethylamine N-oxide, etc.) can also be used. .

In the Somley reaction, first, hexamethylenetetramine is added to the halogenomethyl group to produce a quaternary ammonium salt, and further heating causes hydrolysis to produce an aldehyde. The amount of hexamethylenetetramine used is 0.5 times or more, preferably 1.0 times or more in terms of molar ratio with respect to the halogenomethyl group.

This reaction is carried out in the presence of water, usually at a pH of 3-6.
Perform under 5 acidic conditions. As the solvent, it is preferable to use one or more of water, acetic acid, hydrous alcohol and the like. The reaction temperature is preferably in the range of 50 to 200 ° C,
If the reaction temperature is about 100 ° C, the reaction is completed in about 2 hours. After the reaction, it is treated with an acid such as hydrochloric acid, sulfuric acid or phosphoric acid.

By this reaction, 7-methyl-2-halogenomethylnaphthalene disappears almost completely, and under appropriate conditions, 7-methyl-2-naphthalenecarbaldehyde can be obtained in a high yield of 90% or more. Even if 2,7-DMN coexists as an unreacted product of step (a) in the reaction system, it does not react with hexamethylenetetramine and remains 2,7-DMN. On the other hand, when a dihalide, which is a by-product of step (a), coexists in the reaction system, it is aldehyded by the above reaction and becomes 2,7-naphthalene dicarbaldehyde.

The product of step (b), 7-methyl-2-
Naphthalene carbaldehyde is also relatively unstable with respect to heat, acid, alkali, metal ion, etc., and has a property of easily causing polymerization. After sufficiently removing acids, alkalis, metal ions, etc. by a method such as washing, vacuum distillation is performed to obtain 7-methyl-2.
-It is possible to isolate naphthalene carbaldehyde, but the presence of even a trace amount of acid, alkali, metal ion, etc. causes a marked decrease in yield, and therefore isolation at this stage is not a good idea. Therefore, as in the case of step (a),
After removing a solvent, a salt and the like from the reaction mixture as necessary, it is preferable to directly use them in the reaction of the next step without separating unreacted 2,7-DMN and by-produced 2,7-naphthalenedicarbaldehyde. .

In step (c), 7-methyl-2-naphthalenecarbaldehyde is nitridized to convert the carbaldehyde group into a carbonitrile group to obtain MNCN which is the desired product of the method of the present invention. There are many known methods for deriving carbonitrile from carbaldehyde [eg, Ian T. Harrison et al., Compendium of Organic Synt
hetic Chemistry, p. 460; same vol. 2, p. 186; same vol.
3, p. 296 (Wiley-Interscience)], any of these methods may be used for nitration. Also, once carbaldehyde was once induced into alcohol or carboxylic acid,
A method of carbonitrile conversion is also conceivable.

Reactants and by-products used when synthesizing carbonitrile from carbaldehyde are generally inorganic acids, alkalis, organic acids, low-boiling compounds, etc., all of which are derived from high-boiling naphthalene compounds. Easy to separate. Therefore, it can be said that the route for inducing carbonitrile from carbaldehyde is a synthetic route suitable for carbonitrile conversion of naphthalene.

Particularly suitable for the nitration of the step (c) is operability, yield, easiness of removal of reactants, etc.
In this method, hydroxylamine is used as the nitrating agent. Although it is possible to react hydroxylamine itself as a solvent, it is preferable to use a solvent separately and dissolve hydroxylamine in the form of a salt (for example, hydrochloride, sulfate, etc.) in the solvent before use. The reaction solvent is
One or more of water, alcohols, formic acid, acetic acid and acetic anhydride can be used. The solvent may coexist with formate or acetate (eg, sodium salt), phthalic anhydride and the like.

The amount of hydroxylamine used is preferably equimolar or more to carbaldehyde. The reaction temperature is not particularly limited, but is preferably in the range of 80 to 200 ° C., and it is particularly preferable to carry out the reaction at the reflux temperature. Under reflux conditions, the reaction is usually completed in about 3 hours. If the conditions are properly selected, the conversion rate of carbaldehyde is almost 100%, and MNCN is
It can be obtained with a high yield of 90% or less.

Hydroxylamine as nitrileing agent
It is also possible to use O-sulphonic acid. In this case, nitration proceeds without using acid or salt simply by reacting with carbaldehyde in water. The reaction temperature is generally about -20 to 150 ° C.

Another useful nitration method is to use a combination of ammonia or ammonium salts and an oxidant. For example, a combination of ammonia and nickel peroxide, lead tetraacetate, cupric chloride or iodine, or a combination of diammonium monohydrogen phosphate and nitropropane can be used.

Unreacted 2,7-DMN is inert to this nitration reaction and does not react, but 2,7-naphthalenedicarbaldehyde coexisting as a by-product undergoes nitration to give 2,7-naphthalenediene. Becomes carbonitrile. Therefore,
The reaction mixture of the nitration reaction includes a solvent, a low molecular weight compound such as a nitrating agent (eg, unreacted hydroxylamine) or an inorganic compound, unreacted 2,7-DMN, the target MNCN, and a small amount. However, as a by-product 2,7
-Contains 2,7-naphthalenedicarbonitrile originating from dihalogenomethylnaphthalene.

Of these, low molecular weight compounds and inorganic compounds can be easily removed by distillation or treatment with acid, alkali, water or the like. Therefore, when MNCN is produced by the method of the present invention, not only the unit reaction in the middle can proceed with high conversion and high yield, but also the reaction liquid after removing the low molecular weight compound and the inorganic compound is substantially 2 It consists exclusively of 7,7-DMN, MNCN and 2,7-naphthalenedicarbonitrile. 2,7-DMN and MNCN were separated from this reaction solution,
Is advantageously recovered as a product and the 2,7-DMN is recycled to the halogenation step (a) as part of the starting material.

Although crystallization can be used as this separation method, a separate solvent is required, resulting in high cost and low separation efficiency. Therefore, it is preferable to apply the distillation separation which is generally easy to operate and has high separation efficiency. Of the above components, the melting points of MNCN and 2,7-naphthalenedicarbonitrile are known to be 134-6 ° C and 267-8 ° C, respectively, but other physicochemical properties such as boiling point are known. Absent.

Then, as a result of examining whether or not 2,7-DMN and MNCN can be separated by distillation from the above reaction solution, it was found that all of the above three components were stable at the boiling point of MNCN. It was found that MNCN and 2,7-naphthalenedicarbonitrile have a large difference in boiling points from each other and can be easily separated by distillation.

Therefore, it is preferable to remove inorganic substances and solvents from the reaction mixture obtained in the nitration step and then distill the reaction solution obtained to separate 2,7-DMN and MNCN. Distillation may be carried out under any conditions as long as MNCN is stable, and can be carried out under any pressure conditions of slightly increased pressure, normal pressure and reduced pressure. Considering the distillation temperature, vacuum distillation is industrially suitable, but it is necessary to distill under a pressure at which the boiling point is higher than the melting point. Since the boiling point difference is large,
The distillation apparatus does not particularly require a rectification stage, but if the theoretical number of stages is 5 to 10, the separation will be better and it is more preferable. Also, some reflux is desirable for the same reason.

The intermediate fraction of the 2,7-DMN fraction and the MNCN fraction can be recovered without loss of 2,7-DMN and MNCN by redistillation or by mixing and distilling at the time of the next distillation. Return to halogenation step (a) as starting material 2,7
-The less MNCN in the DMN fraction the better, 20 by weight
% Or less, preferably 10% or less, and more preferably 5% or less. When MNCN is mixed in 2,7-DMN, a part of the MNCN is halogenated and causes MNCN loss.

MNC of the MNCN fraction thus collected
The N content (purity) can be arbitrarily set according to the application.
If a high-purity product is required, the purity of 99
% Or more of MNCN can be easily recovered only by distillation. Further, if necessary, it can be further purified by recrystallization or the like.

[0034]

The present invention will be described below in detail with reference to examples. All the analysis of the composition in the examples was performed by gas chromatography. In the examples,% relating to purity and composition is% by weight, and% relating to conversion, selectivity and yield is mol%.

[0035]

Example 1 7-Methyl-2-bromomethylnaphthalene (MBMN)
Synthesis of 2,7-DMN (purity 98.5%) 3.12 g (0.02 mol, calculated as 100% purity), azobisisobutyronitrile
(AIBN) 0.014 g (8.5 × 10 ^-5 mol), NBS3.56 g
(0.02 mol), and ethylene dichloride (EDC) 50
ml was put into a 100 ml glass three-necked flask equipped with a reflux condenser, and the mixture was reacted under reflux for 2 hours.

After cooling the reaction mixture to room temperature, the precipitated crystals were filtered off and EDC was distilled off to obtain 4.8 g of a reaction solution. From the analysis result of this reaction solution, the conversion rate of 2,7-DMN was 76.5.
%, The yield of MBMN was 59.4%, and the yield of 2,7-dibromomethylnaphthalene was 14.8% (however, the same applies hereafter without loss). MBM based on 2,7-DMN conversion
The N selectivity is 77.6%, and the 2,7-dibromomethylnaphthalene selectivity is 19.3%. This reaction solution (2,7-DMN1
5.3%, MBMN 58.2%, 2,7-dibromomethylnaphthalene 19.4%) can be directly used in the next step as crude MBMN.

[0037]

[Example 2] Reaction and post-reaction treatment were carried out in the same manner as in Example 1 while changing the amount of NBS, and the 2,7-DMN conversion rate and MBMN selectivity, 2,7- The relationship between dibromomethylnaphthalene selectivity and MBMN yield was obtained. As can be seen from this figure, the higher the 2,7-DMN conversion rate is, the lower the MBMN selectivity is and the more the by-product 2,7-dibromomethylnaphthalene selectivity is increased. And this phenomenon becomes more remarkable when the 2,7-DMN conversion rate exceeds 80%. As a result, the yield of MBMN is maximized when the 2,7-DMN conversion rate is around 80%.

[0038]

Example 3 7-Methyl-2-naphthalenecarbaldehyde (MNC)
Synthesis of A) Reaction solution (crude MBMN) obtained by reacting 0.7 mol of NBS with 1 mol of 2,7-DMN in the same manner as in Example 2 (crude MBMN) 43
5.0 g (2,7-DMN29.3%, 0.82 mol; MBMN53.4
%, 0.99 mol; 2,7-dibromomethylnaphthalene 10.1
%, 0.14 mol; 1.27 mol as bromomethyl group), acetic acid
500 ml, 500 ml water, and hexamethylenetetramine 33
6.5 g (2.4 mol, 1.9 times of bromomethyl group) was charged into a 5-liter glass three-necked flask equipped with a reflux condenser, and heated under reflux for 2 hours. Add 1.2 liters of 35% hydrochloric acid to the reaction mixture.
Addition was carried out in 15 minutes, and heating under reflux was continued for 30 minutes. After cooling the reaction mixture to room temperature, 1 liter with 1.6 liters of benzene.
Once, extracted once with 600 ml, benzene was distilled off from the combined organic layers under reduced pressure, and 354.9 g of reaction liquid (crude MNCA)
I got The composition of this reaction solution is MNCA 43.5%, 2,7-
Naphthalene dicarbaldehyde 4.8% 2,7-DMN 36.0
%Met. MBMN was not detected in this reaction solution. The yield of MNCA from MBMN is 91.7%.

[0039]

Example 4 MNCA was obtained in a yield of 87% in the same manner as in Example 3, except that the amount of hexamethylenetetramine was changed to 1.6 times the bromomethyl group in molar ratio. The conversion of MBMN was 100%.

[0040]

Example 5 7-Methyl-2-naphthalenecarbonitrile (MNC
N) of crude MNCA (2,7-DMN) obtained in the same manner as in Example 3.
35.1%, MNCA 45.0%, 2,7-naphthalenedicarbaldehyde 5.2%) 6.87 g (0.022 as carbaldehyde group)
mol), hydroxylamine hydrochloride 1.39 g (0.02 mol), formic acid
3.4 g and acetic anhydride 2.0 g were put into a 30 ml glass three-necked flask equipped with a reflux condenser, and heated under reflux for 2.5 hours. After cooling the reaction mixture to room temperature, 10 ml of water was added and ED
It was extracted twice with 25 ml of C, and the obtained organic layer was washed with 10 ml of water. EDC was distilled off under reduced pressure, and the obtained reaction solution was recovered as crude MNCN. When this reaction solution was analyzed, the conversion of MNCA was 100% (MNCA was not detected) and the yield of MNCN was 84.1%. The composition of this reaction solution is MNCN 40.5%, 2,7-DMN 38.2%, 2,7
-Naphthalenedicarbonitrile 2.7%.

[0041]

Example 6 When 0.02 mol of hydroxylamine sulfate was used instead of hydroxylamine hydrochloride in Example 5, the conversion of MNCA was 100% and the yield of MNCN was 89.7%.

[0042]

Example 7 354.9 g of crude MNCA obtained in Example 3 (MN
CA 0.91 mol, as carbaldehyde group 1.09 mol),
Hydroxylamine hydrochloride 117.1 g (1.68 mol), formic acid 3
80 g and 224 g of acetic anhydride were placed in a 2-liter glass three-necked flask equipped with a reflux condenser and heated under reflux for 5 hours. After cooling the resulting reaction mixture to room temperature, 500 ml of water
Was added and extracted twice with 1.2 liters of EDC. The obtained organic layer was washed with 500 ml of water and then EDC was distilled off to obtain 319.9 g of a reaction solution. The composition of this reaction solution (crude MNCN) was 42.6% MNCN, 2.7% 2,7-naphthalenedicarbonitrile, and MNCA was not detected in this reaction solution.
The yield of NCN was 89.6%.

[0043]

[Example 8] Separation of crude MNCN Reaction liquid obtained by increasing the reaction amount of Example 5 (crude MNCN)
216.9g (MNCN 42.6%, 2,7-DMN 38.7%, 2,7-
Naphthalene dicarbonitrile 2.7%, others: EDC,
50 mmH in a glass distillation column with a diameter of 15 mm.
Simple distillation was carried out under a pressure of g. 2,7-DMN with a purity of 99% (MNCN 0.1% or less) from a fraction with a boiling point of 154-167 ° C
59.6 g of MNC having a purity of 95% is obtained from a fraction having a boiling point of 213 ° C.
59.4 g of N (2,7-naphthalenedicarbonitrile not detected) was obtained. The 2,7-naphthalenedicarbonitrile remained as a distillation bottom.

The results of measuring the physical properties of the recovered MNCN after recrystallization from methanol were as follows. Melting point: 132.4 to 133.3 ° C Mass spectrum: M ⁺ (m / e) = 167 NMR ( ¹ H-NMR, CDCl ₃ ) δ: 2.54 (3H, s), 7.4-8.2 (6
H, m).

[0045]

Example 9 A reaction solution (crude M) obtained in the same manner as in Example 7
310.5 g of NCN) was distilled in a glass distillation column having a diameter of 15 mm and a theoretical plate number of 10 under the conditions of 50 mmHg and a reflux ratio of 5: 1. As a result, the fraction with a boiling point of 161.8 to 162.2 ° C was
84.2g of 9.6% 2,7-DMN, boiling point 214.1-214.6 ° C
Of 108.2 g of MNCN having a purity of 98.2% (no detection of 2,7-naphthalenedicarbonitrile) and an intermediate fraction (M
46.1 g of NCN 43.6%, 2,7-DMN 53.2%) was obtained. In addition, 2,7-naphthalenedicarbonitrile was not detected in these fractions, and the whole amount remained as a residue in the kettle.
-The vapor pressure of naphthalene dicarbonitrile is considered to be significantly lower than that of the components in the distillate.

[0046]

[Example 10] Reuse of recovered 2,7-DMN 2,7-DMN recovered in Example 10 (purity 99.6%, MNC
N 0.1%) 16.5 g was treated in the same manner as in Examples 1, 3 and 5 to carry out halogenation, carbaldehyde formation and nitration formation. Reaction liquid obtained after nitration (crude MNC
N) 14.7 g has a composition of MNCN 44.7%, 2,7-DMN 44.4
%, Which was comparable to the result of Example 5.

[0047]

INDUSTRIAL APPLICABILITY According to the present invention, crude MNCN can be obtained from 2,7-DMN in the form of a reaction mixture in a high yield and in a very simple manner without performing separation and purification in an intermediate step. . Further, since this crude MNCN can be easily separated into each component by distillation, the high-purity starting material (2,7-DMN) and the target substance (MNCN) can be hardly lost at the final stage of the production process. Can be collected.

As described above, since the starting material can be effectively recovered, even if the conversion rate is kept low in the halogenation step so as to increase the selectivity of the target monohalide,
No loss of starting material. As a result, the target M per conversion of the starting material 2,7-DMN was suppressed while suppressing side reactions.
NCN can be produced in high yield, and unconverted 2,7-DMN can be recovered without loss in the final step and reused in the halogenation step to finally obtain the target MNCN in the starting material 2 It can be obtained in high yield even when the amount of 7,7-DMN is supplied. Therefore, according to the present invention, 2,7-DMN
Therefore, MNCN can be efficiently manufactured with low raw material cost, and the manufacturing cost of MNCN is significantly reduced.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the conversion of 2,7-DMN, the selectivity and yield of monohalide, and the selectivity of dihalide by-produced.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Kouichi Takeda, No. 3 Hikari, Kashima-cho, Kashima-gun, Ibaraki Prefecture Sumikin Kako Co., Ltd.

Claims (6)

[Claims] 1. A step of (a) reacting 2,7-dimethylnaphthalene with a halogenating agent to monohalogenate, and (b) oxidizing the obtained 7-methyl-2-halogenomethylnaphthalene to obtain halogenomethyl. 7-methyl-2, which comprises the step of converting the group into a carbaldehyde group, and (c) nitriding the obtained 7-methyl-2-naphthalenecarbaldehyde to obtain 7-methyl-2-naphthalenecarbonitrile. -Method for producing naphthalenecarbonitrile. 2. The method according to claim 1, wherein the halogenating agent used in step (a) is N-bromosuccinimide. 3. The method according to claim 1, wherein the step (a) is carried out so that the conversion of 2,7-dimethylnaphthalene is 20 to 80%. 4. The method according to claim 1, wherein step (b) is carried out by reaction with hexamethylenetetramine. 5. The nitration of step (c) is carried out by reaction with hydroxylamine.
The method described in the section. 6. The products of steps (a) and (b) are subjected to the reaction in the next step without separation from unreacted substances and by-products, and 2,7-dimethyl after the reaction in step (c). The process according to any one of claims 1 to 5, wherein naphthalene and 7-methyl-2-naphthalenecarbonitrile are separated by distillation and the 2,7-dimethylnaphthalene fraction is recycled to step (a).