JPH11180941A - Preparation of 2-methylidenepentane-1,5-dinitrile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing the subject compound by which the subject compound useful as an intermediate for various organic materials and medicines and agrochemicals is prepared in high selectivity while suppressing the formation of byproduct at less as possible by adding a phenolic compound having a specific structure. SOLUTION: (C) Acrylonitrile is dimerized in the presence of (A) a phosphine catalyst (e.g. tricyclohexylphosphine) and (B) a substituted phenols having substituent groups at least at 2- and 6-positions. The component B is preferably a compound of the formula (R<1> and R<5> are each a 5-12C cycloalkyl, a 1-10C alkoxy or the like; R<2> to R<4> are each H, a 1-6C alkyl or an alkoxy), especially 2,6- dialkylphenol, e.g. 2,6-di-t-butylphenol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing 2-methylidenepentane-1,5-dinitrile (commonly called methyleneglutaronitrile). More specifically, the present invention relates to an improvement in a method for producing methylene glutaronitrile by dimerization of acrylonitrile. Methylene glutaronitrile is useful as an intermediate for various organic substances such as medicines and agricultural chemicals, and is also useful as an intermediate for producing polyester resins for paints and urethane resins.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining methylene glutaronitrile in a relatively high yield by dimerization of acrylonitrile, for example, a metal salt such as nickel, cobalt, copper or the like and isonitriles are used as catalysts, and t-butanol is used. (JP-B-46-34410), a method of obtaining methylene glutaronitrile using a metal halide and a trialkylamine as a catalyst (for example, JP-B-46-6892, Kosho 46-154
No. 92 and Japanese Patent Publication No. 47-8287), a method of dimerizing acrylonitrile using sodium sulfinate as a catalyst (Japanese Patent Application Laid-Open No. 60-13294).
No. 6) has been reported.

Further, US Pat. Nos. 3,562,311 and 3,652,642 disclose the use of a phosphine catalyst to dimerize acrylonitrile in a tertiary alcohol and an aromatic hydrocarbon solvent. JP-A-2-29038 discloses a method for producing methylene glutaronitrile by dimerizing acrylonitrile using a bis (acrylonitrile) nickel complex or the like as a catalyst.

The method described in JP-B-46-34410 has the disadvantage of requiring a long reaction at a high reaction temperature due to low catalytic activity.
Even in the method described in Japanese Patent Publication No. 2 and the like, since the activity is low, a high-concentration catalyst is required, which causes a disadvantage that the isolation of the target product induces the polymerization of the target product methyleneglutaronitrile. Have. JP-A-60-132946
However, the method described in Japanese Patent Application Laid-Open No. HEI 3-2903838 and the method described in U.S. Pat. No. 3,562,311 have a disadvantage that the yield of the desired dimer is low. It has the disadvantage of using an expensive catalyst having a low activity and a high concentration, and has a problem in its stability.

[0005] In any of the conventional methods, the desired dimer, as well as the linear dimer (1,4-dicyanobutenes), acrylonitrile trimer, tetramer, other oligomers,
Polymers are formed and the formation of these by-products causes a decrease in the selectivity of the desired dimer. The linear dimer makes it difficult to isolate the target dimer, methyleneglutaronitrile, and the polymer often becomes solid, which may cause clogging of the piping. Further, various difficulties occur in the process and are not preferred.

As a method for suppressing these by-products,
US Pat. No. 3,652,642 proposes a method for dimerizing acrylonitrile in the presence of a phosphine catalyst in a mixed solvent of an aliphatic alcohol and an aromatic hydrocarbon, but the effect is satisfactory. Not something. Further, a method of adding a hydrocarbon solvent to suppress the formation of oligomers and polymers has been proposed (US Pat. No. 3,567,759), but not only reduces the dimerization reaction rate but also suppresses the effect. Not enough. In addition, when a bis (acrylonitrile) nickel complex is used as a catalyst, the dimerization reaction to the desired methyleneglutaronitrile proceeds at a high selectivity. Is not satisfactory.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to produce methylene glutaronitrile by dimerizing acrylonitrile to minimize the generation of by-products and obtain methylene glutaronitrile with a high selectivity. It is intended for.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and as a result, have found that when dimerizing acrylonitrile in the presence of a phosphine catalyst, a phenol compound having a specific structure is added. As a result, it has been found that the formation of by-products is suppressed, and the desired methylene glutaronitrile can be produced with high selectivity, and the present invention has been completed. That is, the gist of the present invention resides in a method for producing methylene glutaronitrile, which comprises dimerizing acrylonitrile in the presence of a phosphine catalyst and a substituted phenol having a substituent at least at the 2,6-position.

Hereinafter, the production method of the present invention will be described in detail. (Catalyst) The phosphine catalyst used in the present invention is not particularly limited, but may be any of the general formula PR ₃ (R is an alkyl group or cycloalkyl group having 1 to 10 carbon atoms which may be different from each other, Represents 6 to 12 aryl groups)
The tertiary phosphine represented by is preferred. Among the tertiary phosphines, cycloalkyl phosphines are particularly preferred.

Here, the cycloalkylphosphine is
In the general formula PR _3, at least one R is equal cycloalkyl group, the remaining R is also included that the alkyl group. Specific examples of the cycloalkyl group include groups such as cyclopentyl, cyclohexyl, methylcyclopentyl, methylcyclohexyl, and cyclooctyl. Specific examples of the alkyl group include groups such as methyl, ethyl, propyl, butyl, amyl, hexyl, octyl, and dodecyl. Illustrative specific tertiary cycloalkylphosphines include tricyclohexylphosphine, tri (methylcyclohexyl) phosphine,
n-butyldicyclohexylphosphine, dicyclohexylmonopropylphosphine and the like, particularly preferably tricyclohexylphosphine, and the compound can obtain a particularly high methyleneglutaronitrile selectivity in combination with a 2,6-disubstituted phenol described later. This is because it is a general-purpose industrial product and is economically advantageous.
The amount of catalyst used is based on acrylonitrile
0.00001 to 1 (molar ratio), preferably 0.000
It is in the range of 1 to 0.1 (molar ratio). The catalyst is separated from the reaction product by a general method such as distillation and extraction, and can be used repeatedly.

(Additive) In the present invention, when dimerizing acrylonitrile using the above-mentioned catalyst to produce methylene glutaronitrile, the dimerization reaction is carried out with a substituted phenol having a substituent at least at the 2,6-position. It is an essential requirement that the present invention be implemented in the presence of a class, and this is a major feature of the present invention. Preferred as substituted phenols having a substituent at least at the 2,6-position used in the present invention are compounds represented by the following formula (1).

[0012]

Embedded image (In the formula, R ¹ and R ⁵ are an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or 7 carbon atoms.
And 12 to 12 aralkyl groups, which may be the same or different. R ² , R ³ and R ⁴ each represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkoxy group, which may be the same or different. )

More specifically, R ¹ and R ⁵ are alkyl groups such as isopropyl group and t-butyl group, cycloalkyl groups such as cyclohexyl group and cyclopentyl group, isopropoxy group, t-butoxy group, sec- And alkoxy groups such as -butoxy group, and aryl groups such as phenyl group and p-tolyl group. R ¹ and R ⁵ may be the same or different from each other.

More specific examples of the substituted phenols include 2,6-diethylphenol, 2,6-diisopropylphenol, 2,6-di-t-butylphenol,
2,6-di-sec-butylphenol, 2,6-di-
t-butyl-4-methylphenol, 2,6-di-t-
Butyl-4-methoxyphenol, 2,4,6-tri-
t-butylphenol and the like. In either case, a high methylene glutaronitrile selectivity can be obtained in combination with a phosphine catalyst, but 2,6-di-t-butylphenol is particularly preferred mainly for economic reasons. The amount of the substituted phenol represented by the above formula (1) is usually selected in the range of 0.1 to 50 equivalents, preferably 1 to 20 equivalents, based on the number of moles of the phosphine catalyst used. When the amount is too small, the effect of improving the selectivity is small, and when the amount is too large, there is no disadvantage to the effect of improving the selectivity, but it is not economically preferable.

(Solvent) The reaction of the present invention can be carried out without using a solvent. However, when the tertiary phosphine and / or substituted phenol used are hardly soluble in the starting acrylonitrile, these are dissolved. Therefore, the reaction can be carried out in an appropriate solvent as required. Examples of these solvents include: Aliphatic and aromatic hydrocarbons such as hexane, benzene, toluene, and chlorobenzene; ethers such as diethyl ether, dimethoxyethane, tetrahydrofuran, and dioxane; and esters such as ethyl acetate, butyl acetate, and butyrolactone. The use amount of these solvents is not particularly limited and is arbitrary.

(Reaction conditions) In this reaction, a predetermined amount of acrylonitrile, a phosphine catalyst and the above substituted phenol are mixed and heated to a desired temperature, preferably in an atmosphere of an inert gas such as nitrogen, carbon dioxide, argon or the like. It is carried out by stirring. Although the progress of the reaction is confirmed even at a temperature lower than 0 ° C., it is usually 0 ° C. to obtain a higher reaction rate.
The above is performed. The reaction temperature is generally 0 to 100 ° C,
Preferably, it is in the range of 10 to 50 ° C. If the temperature is too high, the polymerization reaction of the raw material acrylonitrile unfavorably proceeds competitively. Since the reaction time varies depending on the reaction conditions, it cannot be specified unconditionally.
５０50 hours, preferably 0.2-30 hours.

(Reaction Product) The reaction product obtained by the production method of the present invention is methylene glutaronitrile.
The linear dimer of acrylonitrile (1,4-dicyanobutenes) does not form any by-product. Also, almost no oligomer or polymer of acrylonitrile tetramer or more is formed, and the target methylene glutaronitrile can be obtained with high selectivity. Separation of the product from the reaction mixture containing the catalyst can be performed by a known method such as distillation, extraction, or adsorption.

[0018]

Next, the present invention will be described more specifically with reference to examples and comparative examples. The product was quantitatively analyzed by gas chromatography using an internal standard method using diglyme as an internal standard substance, and the conversion and selectivity were determined by the following formulas.

(Equation 1)

(Example 1) In a Schlenk tube having an inner volume of 30 ml, under a nitrogen atmosphere, a stirrer, 7.4 mg (0.026 mmol) of tricyclohexylphosphine, 2,6-
23.7 mg of diethylphenol (0.160 mmol
l), 852 mg of acrylonitrile (15.90 mmol)
l) 5.51 g of chlorobenzene as a solvent and 88.9 mg of diglyme as an internal standard substance for analysis were charged, and a dimerization reaction was carried out at 20 ° C. for 2 hours while stirring under a nitrogen atmosphere. After completion of the reaction, the obtained homogeneous solution was quantified by gas chromatography.

As a result, acrylonitrile was 259.9.
mg (4.90 mmol) remained to produce 466.8 mg (4.40 mmol) of methylene glutaronitrile. The conversion of the starting acrylonitrile was 69.2%, the selectivity for methylene glutaronitrile was 80.0%, and no linear dimer by-product or solid polymer was formed. In addition, 2,6-diethylphenol is
It was recovered almost quantitatively.

(Example 2) In a Schlenk tube having an internal volume of 30 ml, under a nitrogen atmosphere, a stirrer, 8.7 mg (0.031 mmol) of tricyclohexylphosphine, 2,6-
28.3 mg of diisopropylphenol (0.160 m
mol), 899 mg of acrylonitrile (16.78 m
mol), 5.48 g of chlorobenzene as a solvent, and 84.1 mg of diglyme as an internal standard substance for analysis, and stirred at 20 ° C. for 2 hours under a nitrogen atmosphere for 2 hours.
A quantification reaction was performed. After completion of the reaction, the obtained homogeneous solution was quantified by gas chromatography.

As a result, acrylonitrile was 390.2
mg (7.35 mmol) remained, and 424.3 mg (4.00 mmol) of methylene glutaronitrile was produced. The conversion of the raw material acrylonitrile was 56.2%, the selectivity for methylene glutaronitrile was 84.8%, and no linear dimer by-product or solid polymer was formed. Incidentally, 2,6-diisopropylphenol was recovered almost quantitatively.

Example 3 A stirrer, 8.43 mg (0.030 mmol) of tricyclohexylphosphine, 2,6
16.1 mg of di-t-butylphenol (0.078
mmol), 821.5 mg of acrylonitrile (15.
32 mmol), 5.79 g of chlorobenzene as a solvent
And diglyme 115. as an internal standard substance for analysis.
2 mg was charged and a dimerization reaction was performed at 20 ° C. for 2 hours while stirring under a nitrogen atmosphere. After completion of the reaction, the obtained homogeneous solution was quantified by gas chromatography.

As a result, acrylonitrile was 342.6.
mg (6.46 mmol) remained, and 408.3 mg (3.85 mmol) of methylene glutaronitrile was produced. The conversion of the starting acrylonitrile was 57.9%, the selectivity for methylene glutaronitrile was 86.7%, and no linear dimer by-product or solid polymer was formed. In addition, 2,6-di-t-butylphenol was almost quantitatively recovered.

Example 4 A stirrer, 8.66 mg (0.031 mmol) of tricyclohexylphosphine, 2,6
-Di-t-butylphenol 27.3 mg (0.132
mmol), 788.8 mg of acrylonitrile (14.
7 mmol), 5.1 g of chlorobenzene as a solvent and 97.3 mg of diglyme as an internal standard for analysis.
And a dimerization reaction was performed at 20 ° C. for 2 hours while stirring under a nitrogen atmosphere. After completion of the reaction, the obtained homogeneous solution was quantified by gas chromatography.

As a result, acrylonitrile was 502.4.
mg (9.47 mmol) remained, and 253.4 mg (2.39 mmol) of methylene glutaronitrile was produced. The conversion of the raw material acrylonitrile is 35.7%, the selectivity of methylene glutaronitrile is 91.0%,
Also, no linear dimer by-product or solid polymer was produced. In addition, 2,6-di-t-butylphenol was almost quantitatively recovered.

(Comparative Example) In a Schlenk tube having an internal volume of 30 ml, under a nitrogen atmosphere, a stirrer, 12.3 mg (0.044 mmol) of tricyclohexylphosphine, 1167.1 mg (21.77 mmol) of acrylonitrile, and chlorobenzene as a solvent. 51 g and 57.9 mg of diglyme as an internal standard substance for analysis were charged, and a dimerization reaction was carried out at 20 ° C. for 2 hours while stirring under a nitrogen atmosphere. After completion of the reaction, the obtained homogeneous solution was quantified by gas chromatography.

As a result, acrylonitrile was 118.1.
mg (2.23 mmol) remained, and 658.9 mg (6.21 mmol) of methylene glutaronitrile was produced. The conversion of the raw material acrylonitrile was 89.8%, and the selectivity for methylene glutaronitrile was 63.5%. In addition, 2.1% of a linear dimer by-product and about 200 mg of a solid polymer were produced.

[0029]

According to the method of the present invention, under mild conditions,
Acrylonitrile can be dimerized with a high selectivity, whereby methylene glutaronitrile can be industrially advantageously produced.

Claims (3)

[Claims] 1. A dimerization of acrylonitrile in the presence of a phosphine catalyst and a substituted phenol having a substituent at least at the 2,6-position.
-A process for producing methylidenepentane-1,5-dinitrile. 2. The 2-methylidenepentane-1,5- 2-substituted phenol according to claim 1, wherein the substituted phenol having a substituent at least at the 2,6-position is a compound represented by the following formula (1). A method for producing dinitrile. Embedded image (Wherein, R ¹ and R ⁵ are an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or 7 carbon atoms. R ² , R ^3, and R ⁴ each represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group; They may be the same or different.) 3. The 2-methylidenepentane-1,5 according to claim 2, wherein the substituted phenol having a substituent at the 2,6-position is 2,6-dialkylphenol.
-A process for producing dinitrile.