JPH051009A - Process for producing 1,4-dicyanobutenes - Google Patents

Abstract

PURPOSE:To produce the subject 1,4-dicyanobutene compound useful as a precursor for adiponitrile in a high selectivity, while reducing the addition of a proton donor as in a small amount as possible, by dimerizing acrylonitrile. CONSTITUTION:When acrylonitrile is dimerized in the presence of a phosphinite catalyst or phosphonite catalyst, preferably a compound of formula I or II (Ar is aromatic nucleus; X, X' are H, alkyl, alkoxy, alkylamino; R, R' are alkyl, cycloalkyl, aryl), especially the phosphinite catalyst, to produce a 1,4- dicyanobutene compound useful as a precursor of an intermediate for synthetic fibers or plastics, a compound of formula III (R1, R2 are H, alkyl, cycloalkyl, aryl) is added to the reactional system to produce the objective compound in a high selectivity while using a proton donor in a far small amount (usually in an amount of 0.01-1.5 mole times amount, preferably 0.5-1.0 times amount) compared with conventional methods.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing 1,4-dicyanobutenes. More specifically, the present invention relates to improvement of a method for producing 1,4-dicyanobutenes by dimerization of acrylonitrile.

[0002]

BACKGROUND OF THE INVENTION 1,4-Dicyanobutenes (cis-1,
4-dicyanobutene-1, trans-1,4-dicyanobutene-1 and trans-1,4-dicyanobutene-2
Etc.) are important substances as precursors of adiponitrile, which is an intermediate for synthetic fibers and plastics. Conventionally,
As a method for selectively obtaining 1,4-dicyanobutenes by dimerization of acrylonitrile, for example, JP-B-59-
Japanese Patent No. 36906 and Japanese Patent Publication No. 61-17819 disclose a method of dimerizing acrylonitrile using a phosphinite catalyst or a phosphonite catalyst in the presence of alcohol. In these methods, alcohol is used as a proton donor in a large amount with respect to the catalyst. For example, it is usually used in an amount of 100 molar equivalents or more, particularly 300 to 500 molar equivalents, relative to the catalyst.

Further, JP-A-61-158953 discloses a method of using the above catalyst, in which formamide is used as an extraction solvent for the dimerization product. In this case as well, a large amount of formamide is used. Used for. Thus, in the conventional method of dimerizing acrylonitrile using a phosphinite catalyst or a phosphonite catalyst, a large amount of a proton donor is used for the catalyst, but it is industrially advantageous to use 1,4-dicyanobutenes. It is desirable to selectively carry out the dimerization reaction by using the smallest possible amount of the proton donor for the preparation of ## STR6 ##.

[0004]

DISCLOSURE OF THE INVENTION The present invention reduces the amount of proton donor used as much as possible when dimerizing acrylonitrile to produce 1,4-dicyanobutenes.
Moreover, the object is to obtain 1,4-dicyanobutenes with high selectivity.

[0005]

Means for Solving the Problems As a result of repeated studies to achieve the above object, the present inventors have found that when dimerizing acrylonitrile using a phosphinite catalyst or a phosphonite catalyst, the dimerization reaction is extremely It was confirmed that the desired 1,4-dicyanobutenes can be produced with a high selectivity when carried out in the presence of a small amount of thiourea having a specific structure or a derivative thereof, and the present invention was reached. That is, the gist of the present invention is to dimerize acrylonitrile in the presence of a phosphinite catalyst or a phosphonite catalyst and a compound represented by the formula (1) in claim 1, 1,4-dicyanobutenes. It exists in the manufacturing method of.

The present invention will be described in detail below. The catalyst used for the dimerization of acrylonitrile in the present invention includes various phosphinite catalysts or phosphonite catalysts. Particularly, the compound represented by the following formula (2) or (3) is preferable.

[0007]

[Chemical 2]

[0008]

[Chemical 3]

[In the formulas (2) and (3), Ar represents an aromatic nucleus, and X and X'represent a hydrogen atom, an alkyl group,
It represents an alkoxy group or an alkylamino group, which may be the same or different from each other. R and R'represent an alkyl group or a cycloalkyl group, which may be the same or different. ]

Specific examples of Ar in the formulas (2) and (3) include a phenyl group and a naphthyl group.
X and X ′ are hydrogen atom; methyl group, ethyl group,
Alkyl group such as isopropyl group; alkoxy group such as methoxy group, ethoxy group, propoxy group, t-butoxy group;
Examples thereof include an alkylamino group such as a dimethylamino group and a diethylamino group, and X and X ′ may be the same as or different from each other.

R and R'in the equations (2) and (3)
Specific examples of include an alkyl group having 1 to 8 carbon atoms such as a methyl group, an ethyl group, an isopropyl group and a neopentyl group; and a cycloalkyl group such as a cyclohexyl group,
R and R'may be the same or different from each other.

An example of a typical phosphinite catalyst is methyldiphenylphosphinite (Ph ₂ POM).
e), ethyldiphenylphosphinite, isopropyldiphenylphosphinite, cyclohexyldiphenylphosphinite, methylbis-p-tolylphosphinite, ethylbis-p-tolylphosphinite, isopropylbis-p-tolylphosphinite, etc. Can be mentioned.

As an example of a typical phosphonite catalyst, diethylphenylphosphonite [PhP (OEt)]
₂ ], dimethylphenylphosphonite, diethyl-p-
Examples include tolylphosphonite, dimethyl-p-tolylphosphonite, diisopropylphenylphosphonite, diisopropyl-p-tolylphosphonite and the like.

The amount of these phosphinite catalysts or phosphonite catalysts used is not particularly limited, but is usually 0.1 to 60% by weight based on the total amount of components such as raw materials, catalysts and solvents in the dimerization reaction, Preferably 1 to 30
It is selected from the range of weight%. Although the phosphinite catalyst and the phosphonite catalyst described above are both effective in the reaction of the present invention, the phosphinite catalyst is more preferable from the viewpoint of stability of the catalyst. In the present invention, in the case of producing 1,4-dicyanobutenes by dimerizing acrylonitrile using the above-mentioned catalyst, the dimerization reaction is performed by the following formula (1).

[0015]

[Chemical 4]

(Wherein R ₁ and R ₂ are each a hydrogen atom, an alkyl group, a cycloalkyl group or an aryl group, and may be different from each other or the same) It is an essential requirement to carry out the reaction in the presence of a 1,4-dicyanobutene with a high selectivity with a much smaller amount than the proton-donating solvent in the conventional method. You can get the kind.

In the compound of the above formula (1), the structure of C = S is important, and a compound having a structure of C = O instead of C = S, such as urea, cannot exert the effect of the present invention. Further, in the compound of the formula (1), if at least two hydrogen atoms are present, its effect will be sufficiently exhibited. R ₁ and R ₂ in the formula (1) are a hydrogen atom, a methyl group, an ethyl group,
Examples thereof include alkyl groups such as n-propyl group, isopropyl group, t-butyl group, and cycloalkyl groups such as cyclohexyl group, and specific examples of the compound of formula (1) include, for example, thiourea, methylthiourea, and ethylthio. Urea or the like is used.

The amount of the compound represented by the formula (1) used is usually in the range of 0.01 to 1.5 times equivalent to the number of moles of the phosphinite catalyst or phosphonite catalyst used,
It is preferably selected from the range of 0.5 to 1.0 times equivalent, and a much smaller amount than a well-known proton donor such as alcohol is sufficient. In the present invention, in addition to the above components,
It is desirable to add a hydrocarbon solvent, for example, the required amount of benzene, toluene, xylene, hexane, heptane, etc. is used.

The dimerization reaction of acrylonitrile according to the method of the present invention is usually carried out under an atmosphere of an inert gas by adding a predetermined amount of acrylonitrile, a phosphinite catalyst or a phosphonite catalyst, a compound of the formula (1) and preferably a hydrocarbon solvent. Mix, usually -10 to 100 ° C, preferably 5
It is carried out by stirring at a temperature of about -80 ° C.
The concentration of acrylonitrile is preferably kept high from the viewpoint of reaction efficiency, and is generally 5 to 70% by weight, preferably 10 to 40% by weight. Since the presence of water hinders the progress of the reaction, it is desirable to sufficiently dry components such as acrylonitrile and a solvent in advance.

[0020]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. In the examples below, the products were analyzed by gas chromatography and gel permeation chromatography. Further, the "conversion rate" indicates a weight% of acrylonitrile converted into a dimer and a polymer by-product with respect to a charged acrylonitrile. The "selectivity" of a product is
It is the value in% of the weight ratio of the product to the weight of the converted acrylonitrile. Further, 1,4-dicyanobutenes include cis-1,4-dicyanobutene-1, trans-1,4-dicyanobutene-1 and trans-1,
Represents 4-dicyanobutene-2.

Example 1 2 g (37.7 mmol) of acrylonitrile, 4 g of benzene and 4 g of benzene were placed in a flask having a volume of 30 ml under an argon atmosphere.
Thiourea (0.27 g, 3.5 mmol) and isopropyldiphenylphosphinite (0.9 g, 3.7 mmol) were charged, and the mixture was heated to 60 ° C. on an oil bath and stirred for 1 hour to carry out a dimerization reaction. After the reaction was completed, the product was analyzed by gas chromatography using an internal standard method (internal standard: biphenyl).
Was used for quantitative analysis. Conversion rate of acrylonitrile is 3
The selectivity of 1,4-dicyanobutenes was 87.0%, and the selectivity of 2-methyleneglutaronitrile was 5.7%.

Comparative Example 1 Instead of the thiourea used in Example 1, urea 0.
When the reaction was performed in the same manner as in Example 1 except that 8 g (13 mmol) was used, the conversion rate of acrylonitrile was 8.5%, and the selectivity of 1,4-dicyanobutenes was 2%.
It was 5.0%, and the selectivity for 2-methyleneglutaronitrile was 9.5%.

[0023]

INDUSTRIAL APPLICABILITY According to the present invention, when dimerizing acrylonitrile to produce 1,4-dicyanobutenes, the amount of the phosphinite catalyst or phosphonite catalyst is much smaller than that of conventionally known proton donors. By using an amount of the compound of the above formula (1), the target product can be obtained with high selectivity.

Claims (1)

What is claimed is: 1. A phosphinite catalyst or a phosphonite catalyst, and a compound represented by the following formula (1): (Wherein R ₁ and R ₂ each represent a hydrogen atom, an alkyl group, a cycloalkyl group or an aryl group, and may be different from each other or the same) Below, the manufacturing method of 1, 4- dicyano butenes characterized by dimerizing acrylonitrile.