JP2719961B2 - Stereoisomerization of methyl-delta-4-tetrahydrophthalic anhydride - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a process for the stereoisomerization of methyl-delta-4-tetrahydrophthalic anhydride, and more particularly to methyl-delta-4-tetrahydrophthalic anhydride.
The present invention relates to a method for subjecting delta-4-tetrahydrophthalic anhydride to a stereoisomerization by heat treatment in the presence of imidazoles.

ART methyl - delta 4-tetrahydrophthalic anhydride (hereinafter abbreviated as Me-Δ ⁴ -THPA) are useful compounds which are used as some components of the curing agent and an unsaturated polyester resin having an epoxy resin.

However, cis obtained by Diels-Alder reaction the trans piperylene and maleic anhydride-3-methyl - delta 4-tetrahydrophthalic anhydride (. Hereinafter abbreviated as cis -3Me-Δ ⁴ -THPA) or isoprene 4-methyl can be obtained by the maleic anhydride to the Diels-Alder reaction - delta-4 tetrahydrophthalic anhydride (. which hereinafter abbreviated as 4Me-Δ ⁴ -THPA) has a melting point are each 61 ° C. and 64 ° C. Solid at room temperature. Therefore, it is unsuitable as an epoxy resin curing agent which is required to be liquid at room temperature for handling. Therefore, these cis -3Me-Δ ⁴ -THPA and /
Or 4Me-delta ⁴ and structural isomers and / or stereoisomers of the -THPA With isomer mixtures, isomerization process to liquefy at room temperature have been developed.

Meanwhile, conventionally, as follows is disclosed as a method of stereoisomeric the Me-Δ ⁴ -THPA.

(B) by heating the cis -3Me-Δ ⁴ -THPA a Diels-Alder adduct of the maleic anhydride trans piperylene in the presence of dibutyl aniline, to the corresponding trans -3Me-Δ ⁴ -THPA Method for stereoisomerization (Journal of American Chemical Society)
1950, Vol. 72, pp. 1678-1681).

(B) heating the cis -3Me-Δ ⁴ -THPA in the presence of an alkali metal compound, the corresponding method of stereoisomerization trans body (Sho 57-34834 Patent Publication).

(C) Me-Δ ⁴ -THPA stereoisomerization method of heating in the presence of an alkaline earth metal oxide (JP-B 58-54146 JP)
And so on.

Further, the present inventors have also in the presence of a IV B metal compound or an alkali metal of the periodic table, heating cis by performing -3Me-Δ ⁴ -THPA or cis -3Me-Δ ⁴ -THPA and
4Me-delta ⁴ proposes stereoisomerization method of -THPA mixture (Japanese Patent Application No. Sho 63-181787 and Nos 63-223451).

Problems to be Solved by the Invention However, the known stereoisomerization methods disclosed above have the following problems. That is, in the stereoisomerization method in the presence of dibutylaniline or an alkali metal compound, there is a problem in that a large amount of by-products causes distillation residue to be generated during the rectification of the product, so that the yield decreases. Furthermore, in this method, since the catalyst is dissolved in the product, it is difficult to separate the catalyst, and it is difficult to reuse the catalyst.

In addition, when the present inventors retested the stereoisomerization method in the presence of an alkaline earth metal oxide, the stereoisomerization rate was low, and the reaction required a high temperature and a long time. There was found.

Upon invention stereoisomeric the Me-Δ ⁴ -THPA,
By-production of heavies is large, re-use of the catalyst is difficult, which is the reaction rate to solve the problems associated with the prior art that slow, Me-delta ⁴ inexpensive efficient solid of -THPA It is intended to provide an isomerization method.

SUMMARY The present inventors of the Invention The problem is, Me-Δ ⁴ -THPA stereoisomers of method in which various studies, the presence of imidazole, a heat treatment was performed, inexpensive The present inventors have found an efficient stereoisomerization method and have completed the present invention. That is, the present invention
The Me-Δ ⁴ -THPA in the presence of imidazoles, to a stereoisomeric Act of Me-Δ ⁴ -THPA, characterized in that the heat treatment.

^{Me-Δ 4 -THPA Me-Δ} 4 -THPA trans piperylene and cis -3Me-Δ ⁴ obtained by the maleic anhydride to the Diels-Alder reaction -THPA or trans piperylene and isoprene used in the present invention mixture a mixture of cis obtained by reacting maleic anhydride and Diels-Alder -3Me-Δ ⁴ -THPA and 4Me-Δ ⁴ -THPA of the like.

The isomerization process of Me-Δ ⁴ -THPA of the present invention, a so-called location-based movement of the double bond, structured isomerization does not occur, resulting only stereoisomerization.

That is, cis -3Me-Δ ⁴ -THPA is stereoisomerization trans -3Me-Δ ⁴ -THPA which reacts by isomerization, a low freezing point substance provides a mixture of cis- and trans-isomer.
In the case of using a mixture of cis -3Me-Δ ⁴ -THPA and 4Me-Δ ⁴ -THPA is provide further low freezing point material than the above, which cis -3Me-Δ ⁴ -THPA, trans -3Me −
It believed to be based on freezing point depression effect of mixing three parties Δ ⁴ -THPA and 4Me-Δ ⁴ -THPA.

Catalyst The catalyst used in the present invention is an imidazole. As such a catalyst, specifically, imidazole, 2-
Methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl -2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1- (cyanoethylaminoethyl) -2-methylimidazole, 1-aminoethyl-2-methylimidazole , 1-cyanoethyl-2-undecylimidazole, 2-enyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 4-methylimidazole and the like. Among these, as a catalyst, imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-ethyl The use of -4-methylimidazole, 4-methylimidazole is particularly preferred.

The amount of the catalyst used relative to Me-Δ ⁴ -THPA, a 0.001 to 10% by weight, preferably from 0.01 to 5% by weight.

Further, the product liquid isomer mixture and the catalyst of the present invention can be separated by known means such as distillation, and the catalyst separated in this manner can be reused.

Stereoisomerization Conditions The reaction format of the stereoisomerization reaction of the present invention may be either a batch system or a continuous system. The reaction temperature is from 70 to 250 ° C, preferably from 100 to 200 ° C. The reaction time is 0.1 to 15 hours, preferably about 0.2 to 7 hours in the case of a batch system. The reaction pressure may be normal pressure or under pressure. The solvent may or may not be used, but if used, toluene,
Xylene, cumene, tetralin or decalin and the like can be used.

Advantageous Effects The method of the present invention, can be reduced generation of high boiling point by-products, thus stereoisomeric mixture of Me-Δ ⁴ -THPA in high yield. Further, the method of the present invention uses a small amount of the catalyst and is easy to separate the product from the catalyst, so that the catalyst can be reused and is excellent in industrial value. Furthermore, the method of the present invention has the effects of requiring no high-temperature and long-time reaction due to a high rate of the stereoisomerization reaction, and having less coloring of the obtained liquid product (low Gardner color number).

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. The ratios, parts and percentages in the examples are on a weight basis unless otherwise specified.

Cis four-necked flask 300ml with Example 1 agitator -3Me-Δ ⁴
-THPA (mp 61 ° C.) (manufactured by Shikoku Fine Chemical Co., Ltd.) 100 parts of 2-methylimidazole with respect to cis -3Me-Δ ⁴ -THPA charged 0.1 parts of stirring in a nitrogen atmosphere, 3 at 0.99 ° C.
A time isomerization reaction was performed. After the reaction, the product containing the catalyst was distilled under reduced pressure to obtain 97.2 parts of a pale yellow transparent liquid (Gardner color number <1).

Freezing point of the liquid product is 0 ° C., the results were analyzed by gas chromatography cis -3Me-Δ ⁴ -THPA 28%
And were trans -3Me-Δ ⁴ mixture of -THPA 72%. Further, as a result of the nuclear magnetic resonance spectrum analysis, it was confirmed that the double bond of the cyclohexene ring did not move.

Examples 2 to 13 The isomerization reaction and distillation under reduced pressure were carried out in the same manner as in Example 1 except that the kind of the catalyst used, the amount of the catalyst used, and the stereoisomerization reaction conditions were changed as shown in Table 1. Thus, a liquid product was obtained. Table 1 shows the recovery (parts), cis- / trans-form ratio, Kardner color number and freezing point of the obtained product. The imidazoles used as catalysts are all manufactured by Shikoku Fine Chemical Company.

It was used in the ratio shown an embodiment 14 to 17 cis -3Me-Δ ⁴ -THPA and 4Me-Δ ⁴ -THPA total 100 parts in Table 2, using 2-methyl imidazole or 2-undecyl imidazole as a catalyst, The isomerization reaction and distillation under reduced pressure were carried out in the same manner as in Example 1 except that the amount used was changed. Recovery of the resulting product (parts) shown cis- / trans isomer ratio of cis -3Me-Δ ⁴ -THPA, the Gardner color number and freezing point in the second table.

Comparative Example 1 In the same manner as in Example 1 except that dibutylaniline (manufactured by Tokyo Chemical Industry Co., Ltd.) 2 parts was used in place of 0.1 part of 2-methylimidazole and the reaction conditions were set to 200 ° C. for 5 hours. An isomerization reaction and vacuum distillation were performed. As a distillate, 88.7 parts of a red liquid (Gardner color number 4) was obtained. 13.3 parts of heavy materials remained in the pot.

The freezing point of the distillate was 10 ° C, and the result of gas chromatography analysis showed that the cis form was 40% and the trans form was 60%
Was a mixture of

Comparative Example 2 Five parts of calcium oxide was used instead of 0.1 part of 2-methylimidazole as a catalyst, and the reaction conditions were 200
An isomerization reaction was carried out in the same manner as in Example 1 except that the temperature was changed to 5 ° C. for 5 hours. After the reaction, the product was solidified when cooled to room temperature, and its melting point was 42 ° C.

The product was analyzed by gas chromatography and found to be a mixture of 80% cis-form and 20% trans-form. Stereoisomerization in the presence of this catalyst revealed that the rate of the isomerization reaction to trans-form was slow. .

Comparative Example 3 One part of sodium hydroxide was used instead of 0.1 part of 2-methylimidazole as a catalyst, and the reaction conditions were 200
The isomerization reaction and the distillation under reduced pressure were carried out in the same manner as in Example 1 except that the temperature was changed to 3 hours at ℃. 87.6 parts of a pale yellow transparent liquid (Gardner color number <1) was obtained as a distillate.

The freezing point of the distillate was 3 ° C., and as a result of gas chromatography analysis, it was a mixture of cis-isomer 31% and trans-isomer 69%.

Example 18 An isomerization reaction and vacuum distillation were carried out in the same manner as in Example 1 except that the distillation residue separated in Example 1 was reused. Distillate is a pale yellow transparent liquid (Gardner color number <
1) and 98.6 parts were recovered. The distillation residue was 4.2 parts, but the net value after subtracting 2.8 parts of Example 1 was 1.4.
Department.

The freezing point of the distillate was 5 ° C, and as a result of gas chromatography analysis, it was a mixture of 34% of the cis form and 66% of the trans form. This proved that repeated use of the distillation residue containing the catalyst was possible.

Continuing from the front page (72) Inventor Shoji Ishii 1-3-1, Nishitsurugaoka, Oimachi, Iruma-gun, Saitama Prefecture Within Toa Fuel Industry Co., Ltd. (72) Inventor Hiroshi Ueno 1 Nishitsurugaoka, Oimachi, Iruma-gun, Saitama Prefecture 3-1, Chome Toa Fuel Industry Co., Ltd.

Claims (3)

(57) [Claims] 1. A method for stereoisomerizing methyl-delta-4-tetrahydrophthalic anhydride, comprising subjecting methyl-delta-4-tetrahydrophthalic anhydride to a heat treatment in the presence of imidazoles. 2. The method according to claim 1, wherein the methyl-delta-4-tetrahydrophthalic anhydride is cis-3-methyl-delta-4-tetrahydrophthalic anhydride. 3. The method of claim 1, wherein the methyl-delta-4-tetrahydrophthalic anhydride is a mixture of cis-3-methyl-delta-4-tetrahydrophthalic anhydride and 4-methyl-delta-4-tetrahydrophthalic anhydride. The method according to (1).