JPH02223552A - Production of n-phenylmaleimide compound - Google Patents

Abstract

PURPOSE:To simply obtain the title compound useful as a raw material, etc., for heat resistance in high yield and purity by subjecting a compound obtained by reacting an amine compound with maleic anhydride in an organic solvent to cyclodehydration in the presence of a solvent and superacid resin. CONSTITUTION:A compound expressed by formula I (R1-R5 are h, halogen, 1-6C alkyl, 1-6C alkyl ether, OH, phenoxy, etc.) is reacted with maleic anhydride in an organic solvent (e.g. benzene, toluene, xylene, etc.) to give a phenylmaleimide expressed by formula II, which is subjected to cyclodehydration in the presence of a superacid resin (e.g. sulfonylfluoride vinyl ether) and aprotic polar solvent (e.g. N,N-dimethylacetamide) to provide the compound expressed by formula III. The above-mentioned method enables easy re-utilization of the resin and is industrially advantageous.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel method for producing an N-phenylmaleimide compound useful as a raw material for heat-resistant polymers or as a raw material for medicines, agricultural chemicals, etc.

[Conventional technology]

Conventionally, the synthesis of N-phenylmaleimide compounds has generally been carried out by dehydrating and ring-closing phenylmaleamide acids obtained from an amine compound and maleic anhydride using fatty acid anhydrides such as acetic anhydride (e.g. ,
Japanese Patent Publication No. 53-53648).

However, this method has drawbacks such as the need to use an expensive catalyst such as a cobalt salt and an expensive dehydrating agent such as acetic anhydride in order to obtain a high yield of N-phenylmaleimide compound. In addition, after imidization, it is necessary to remove the acid used as a dehydration ring-closing agent when isolating the target product. To remove the acid, the reaction mixture must be poured into a large amount of water or This method is complicated and not necessarily satisfactory, as it requires injecting water to precipitate crystals, then filtering out the precipitated crystals, and washing the crystals with a large amount of water.

On the other hand, there is a method in which an amine compound and maleic anhydride are reacted in an aqueous solvent to produce phenylmaleamic acids, and then imidized by heating in the presence of an acid catalyst (Japanese Patent Publication No. 57
-42043).

Furthermore, a method is known in which an amine compound and maleic anhydride are reacted in an organic solvent to produce phenylmaleamide acids, and the phenylmaleimide compound is produced by dehydration and ring closure in the coexistence of an aprotic polar solvent and an acid catalyst. (For example, Special Publication No. 53-68770, Special Publication No. 55-4
6394, Japanese Patent Publication No. 60-100554), these methods may produce non-negligible by-products.
In addition to suppressing by-products depending on the reaction conditions, purification operations are necessary to obtain a highly pure N-phenylmaleimide compound.

Purification methods include isolation by recrystallization using an appropriate solvent or isolation by distillation, but in either method, removal of the acid catalyst is essential. The acid catalysts commonly used are sulfuric acid, p-toluenesulfonic acid, phosphoric acid, phosphoric anhydride, polyphosphoric acid, trichloroacetic acid, trifluoroacetic acid, etc. After imidization, the reaction solution is repeatedly washed with water or diluted. After neutralizing with a weak alkaline aqueous solution, wash with water to remove the acid. The desired product must be obtained from the resulting organic solvent layer, and this method is not necessarily industrially advantageous since it requires a lot of time and effort, including waste liquid treatment.

We also proposed a method in which maleic anhydride and an amine compound are heated in an aprotic polar solvent in the presence of phosphorus oxide to complete imidization, followed by direct distillation to obtain an N-phenylmaleimide compound following the solvent. (For example, Special Publication No. 60-112758, Special Publication No. 60-112759)
In this method, when charging the phosphorus oxide as a dehydrated imidization ring-closing agent to the reaction system, the phosphorus oxide is charged in advance to control the temperature and prevent deterioration of the reaction product due to heat of dissolution during charging. It is necessary to use a preparation solution diluted with an organic solvent, and it is also necessary to remove the phosphorus compound after imidization. When removing phosphorus compounds,
The phosphorus compound liquid layer is separated and recovered, but in order to effectively separate the phosphorus compound liquid layer, the remaining amount of solvent in the reaction mixture is a problem, and it is necessary to consider the concentration state of the solvent used. However, it is not an industrially satisfactory method, as it is not operationally rational and requires treatment of the separated phosphorus compound.

[Problems to be Solved by the Invention] The present invention provides an industrially advantageous method for producing N-phenylmaleimide compounds that does not have these drawbacks.

[Means to solve the problem]

As a result of intensive studies aimed at achieving the object of the present invention, the present inventors have found that an N-phenylmaleimide compound can be obtained with high purity and high yield, and that the acid catalyst used during imidization can be simply separated by filtration. The inventors have discovered that the acid catalyst can be easily removed and recovered, the solvent can be immediately distilled off from the filtrate to obtain the desired product, and the recovered acid catalyst can be reused, leading to the present invention.

That is, the present invention relates to the general formula (I) (wherein R3-R5 are hydrogen atoms, halogen atoms, C4-R5
C6 alkyl group, C3 to C6 alkyl ether group,
Represents a hydroxyl group, a phenoxy group, a carboxyl group, and a nitro group. ) A general formula (n) produced by reacting an amine compound represented by the formula (n) with maleic anhydride in an organic solvent (wherein, R1-R1 represents the same meaning as in the above general formula (I)). General formula (I[[) (wherein, R+ "Rs is the This is a method for producing an N-phenylmaleimide compound represented by the formula (I).

Hereinafter, specific embodiments of the present invention will be explained.

Examples of the amine compound represented by the general formula (I) used in the method of the present invention include aniline, toluidine,
Examples include ethylaniline, anisidine, phenetidine, isopropoxyaniline, chloroaniline, bromoaniline, iodoaniline, nitroaniline, aminophenol, and aminobenzoic acid.

The amount of maleic anhydride and amine compound to be used is 1.0 to 1.5 mol, preferably 1.1 to 1.3 mol, per 1 mol of the amine compound.

If the amine compound is used in large excess with respect to maleic anhydride, the excessive amount of the amine compound may be added to the produced N-phenylmaleimide, producing by-products, which is not preferable.

The organic solvent used in the present invention is preferably a solvent that can azeotropically remove water produced by the dehydration ring-closing reaction, and includes nonpolar solvents such as henzene, toluene, xylene, ethylene dichloride, chlorobenzene, and mesitylene. The amount used is preferably 3 to 10 times that of maleic anhydride (weight ratio) to ensure smooth reaction.

Further, as the aprotic polar solvent used in the method of the present invention, N,N-dimethylacetamide, NN-dimethylformamide, N-methyl 2-pyrrolidone, 1
, 3-dimethyl-2-imidazolidinone, N,N-diethylacetamide, etc., and the amount used is 10 to 100 parts by weight, preferably 10 to 100 parts by weight, per mole of the amine compound.
It is preferable to use 50 parts by weight.

The dehydration imidization agent used in the present invention is a super-strongly acidic resin. As the super-strongly acidic resin, perfluorosulfonic acid type resin (Nafion H
, manufactured by Du'Pont), and conventional sulfonic acid type ion exchange resins (obtained by sulfonating polymers or copolymers of aromatic vinyl compounds) generally decompose at temperatures above 140°C. In contrast, this super acidic resin (Nafion H) is characterized by zero heat resistance at 200°C or higher. The amount used is 10 to 300 g, preferably about 30 to 150 g, per mole of the amine compound.

However, the amount of the super-strong acidic resin is not limited to these amounts (the optimum amount to be used can be determined as appropriate considering yield and economic efficiency. The super-strong acidic resin used as the imidizing agent is It can be recovered by filtration and used as is or after regeneration for the next reaction.

The reaction in the method of the present invention is carried out by adding an amine compound to a mixed solution of maleic anhydride and organic cutting, and heating the mixture at 150°C or lower, preferably 20 to 100°C, for 10 minutes or more, preferably at 0.
．． Stir for 5 to 1 hour to generate phenylmaleimide acid, then add an aprotic organic solvent and a super acidic resin to the resulting reaction solution and heat at 80°C or higher, preferably at 100°C or higher.
It is carried out by heating in a temperature range of 180°C, stirring for 0.5 to 20 hours, preferably 1 to 6 hours, and azeotropically separating water produced by the reaction. After the reaction is carried out under these conditions, it is cooled, the super acidic resin is removed by filtration, and the resulting organic layer is immediately concentrated under reduced pressure to remove the solvent, yielding an N-phenylmaleimide compound. . The product is isolated immediately by distillation, optionally followed by a solvent, or
It can be isolated by concentrating or distilling off the solvent and immediately recrystallizing it with a suitable solvent such as ethanol or isopropyl alcohol.

[Operations and Effects] The method of the present invention has simpler reaction operations than conventional production methods, and can easily produce N-phenylmaleimide compounds with high purity and high yield, and the acid catalyst removed and recovered by filtration. Super acidic resins can be easily reused and are manufactured using an extremely industrially advantageous manufacturing method.

Hereinafter, the method of the present invention will be explained in more detail with reference to Examples.

Adjustment of super acidic resin (Nafion It)Nafi
on K (manufactured by Du'Pont, commercially available as K type) 5
After stirring 0 g with 40 ml of 4N hydrochloric acid at room temperature for 4 hours, it was filtered and washed with distilled water until neutral. After repeating this operation four more times, 11 g of 00 mm was dried under reduced pressure at 80 to 90° C. to obtain Nafion II.

Example 1 58.8 g of maleic anhydride was placed in a reaction vessel equipped with a stirrer, thermometer, and Dean-Stark azeotropic distillation wrap.
A solution of 46.5 g (0.5 mol) of aniline dissolved in 46.5 g of toluene was gradually added using a dropping funnel under stirring. added to. Subsequently, after reacting for 0.5 hours, 35 g of tlafion It (super acidic resin) was charged, heated to reflux temperature, and reacted for 4 hours while azeotropically removing water produced by the reaction.

After the reaction was completed, the reaction solution was cooled to 70 to 80°C, the super acidic resin Nafion It was removed by filtration, and the solvent was immediately distilled off from the resulting organic layer, followed by vacuum distillation. .6g (aniline group 1 yield 86.3%
) was obtained as yellow crystal N-phenylmaleimide.

The m and p of the obtained product were 91 to 92'C, and the purity analysis result by GPC was 99% or more.

Example 2 29.4 g of maleic anhydride (
A solution of 23.3 g (0.25 mol) of aniline dissolved in 23.3 g of toluene was charged with 77.5 g of l-luene (0.3 mol) and 9 g of N,N dimethylacetamide, using a dropping funnel under stirring. was added gradually.

Subsequently, after reacting for 0.5 hours, the N recovered in Example 1
17.5 g of af ion II was charged, heated to reflux temperature, and reacted for 4 hours while azeotropically removing water produced by the reaction. After the reaction was completed, the same operation as in Example 1 was carried out to obtain 37.2% of yellow crystal N-phenylmaleimide.
g (aniline standard yield 86.0%) was obtained.

m, p, of the obtained product are 91-92° CT: GPC
The purity analysis result was 99% or more.

Example 3 58.8 g of maleic anhydride (
0.6 mol) and 310 g of xylene were charged, and 63.8 g (0.5 mol) of p-chloroaniline was added using the dropping funnel with stirring.
A solution of N,N-dimethylaceI amide (36 g) was gradually added. Subsequently, after reacting for 0.5 hours, 70 g of Nafion H was charged, heated to reflux temperature, and reacted for 5 hours while azeotropically removing water produced by the reaction. After the reaction was completed, the reaction solution was cooled to 70 to 80°C, the super acidic resin Nafion II was removed by filtration, and the solvent was immediately distilled off from the resulting organic layer. After cooling to precipitate crystals, filter and dry to remove pale yellow crystals of N.
-(p-chlorophenyl)maleimide 88.3g (p
- Chloroaniline standard yield of 85.2%) was obtained.

This product has a purity of 99% or more according to GPC analysis, m,
p was 116-118°C.

Examples 4 to 8 In the same manner as in Examples 1 to 3, 0.6 mol of maleic anhydride and 0.5 mol of various phenylamine compounds were reacted,
Subsequent work-up and purification were performed to obtain the corresponding N-phenylmaleimide compound. N obtained by each example
-The yield, appearance, purity, and melting point of the phenylmaleimide compound are summarized in Table 1 together with each raw material and reaction conditions.

Claims (1)

[Claims] 1) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_1 to R_5 are hydrogen atoms, halogen atoms, C
It represents an alkyl group of _1 to C_6, an alkyl ether group of C_1 to C_6, a hydroxyl group, a phenoxy group, a carboxyl group, and a nitro group. ) General formula (II) produced by reacting the amine compound represented by the formula and maleic anhydride in an organic solvent ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R_1 to R_5 are the general formulas above The general formula (III) is characterized by dehydrating and ring-closing phenylmaleamic acid represented by (I) in the presence of a super strong acid resin in the coexistence of an aprotic polar solvent. ) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) (In the formula, R_1 to R_5 represent the same meanings as in the above general formula (I).) Method for producing an N-phenylmaleimide compound represented by .