JP2733785B2 - Method for stereoisomerizing 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 a process for converting methyl-delta-4-tetrahydrophthalic anhydride to diazabicyclo. The present invention relates to a method of performing a heat treatment in the presence of undecene or a salt or diazabicyclononene or a salt thereof to perform stereoisomerization.

ART methyl - delta 4-tetrahydrophthalic anhydride (. Hereinafter abbreviated as Me- △ ⁴ -THPA) is a useful compound which is used as such components of the curing agent and an unsaturated polyester resin having an epoxy resin .

However, cis-3-methyl-delta-4-tetrahydrophthalic anhydride (hereinafter abbreviated as cis-3Me- △ ^4- THPA) or isoprene obtained by subjecting transpiperylene and maleic anhydride to a Diels-Alder reaction. And 4-methyl-delta-4- obtained by subjecting maleic anhydride to Diels-Alder reaction
Tetrahydrophthalic anhydride (hereinafter abbreviated as 4Me- △ ^4- THPA) has melting points of 61 ° C. and 64 ° C., respectively, and is a 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- △ ^4- THPA and / or 4Me- △ ^4- THPA are isomerized by structural isomerization and / or stereoisomerization to form a mixture of isomers, thereby liquefying at room temperature. Have been developed.

By the way, the following methods have been disclosed as methods for stereoisomerizing Me- △ ^4- THPA.

(A) By heating cis-3Me- △ ^4- THPA, which is a Diels-Alder adduct of transpiperylene to maleic anhydride, in the presence of dibutylaniline, to the corresponding trans-3Me- △ ^4- THPA Stereoisomerization method (Journal of American Chemical Society, 1950, Vol. 72, pp. 1678-1681).

(B) A method in which cis-3Me- △ ^4- THPA is heated in the presence of an alkali metal compound to stereoisomerize to the corresponding trans form (JP-B-57-34834).

(C) Stereoisomerization method in which Me- △ ^4- THPA is heated in the presence of an alkaline earth metal oxide (Japanese Patent Publication No. 58-54146)
And so on.

In addition, the present inventors have also performed cis-3Me- △ ^4- THPA or cis-3Me- △ ^4- THPA and 4Me- by performing heat treatment in the presence of a Group IVB metal compound or an alkali metal of the periodic table. △ ⁴ proposes a stereoisomeric 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 that a large amount of by-products causes distillation residue to be generated during the rectification of the product, so that the yield is reduced. 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 re-tested 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.

The present invention relates to the stereoisomerization of Me- △ ^4- THPA,
Heavies by-production of many, reuse of the catalyst is difficult, which is the reaction rate to solve the problem associated with the prior art point of slow, Me-△ ⁴ inexpensive efficient solid of -THPA It is intended to provide an isomerization method.

Means for Solving the Problems Summary of the Invention The present inventors studied various methods for the stereoisomerization of Me- △ ^4- THPA, and found that diazabicycloundecene or salts or diazabicyclononene or salts thereof were used. By performing a heat treatment in the presence of the compound, an inexpensive and efficient stereoisomerization method was found, and the present invention was completed. That is, the present invention is characterized in that Me- △ ^4- THPA is heat-treated in the presence of diazabicycloundecene or a salt or diazabicyclononene or a salt thereof.
The present invention relates to a method for stereoisomerizing Me- △ ^4- THPA.

Me- △ ⁴ -THPA used in the present invention Me- △ ⁴ -THPA cis -3Me- △ ⁴ -THPA or trans piperylene and isoprene obtained by a Diels-Alder reaction of trans-piperylene and maleic anhydride And a mixture of cis-3Me- △ ^4- THPA and 4Me- △ ^4- THPA obtained by subjecting a mixture of the above to a Diels-Alder reaction with maleic anhydride.

In the Me- △ ^4- THPA of the present invention, in the isomerization method, so-called structural isomerization based on the transfer of a double bond does not occur, but only stereoisomerization occurs.

That is, isomerization of cis-3Me- △ ^4- THPA results in stereoisomerization to the corresponding trans-3Me- △ ^4- THPA to give a mixture of cis- and trans-forms, which are low freezing point substances. Further, when a mixture of cis-3Me- △ ^4- THPA and 4Me- △ ^4- THPA is used, a substance having a lower freezing point than that described above is obtained, which is composed of cis-3Me- △ ^4- THPA and trans-3Me. It is considered to be based on the freezing point depressing action due to the mixture of-△ ^4- THPA and 4Me- △ ^4- THPA.

Catalyst The catalyst used in the present invention is diazabicycloundecene or a salt or diazabicyclononene or a salt thereof. As such a catalyst, specifically, 1,
8-diazabicyclo [5.4.0] undecene-7 (hereinafter abbreviated as DBU), DBU formate, DBU acetate, DBU propionate, DBU butyrate, DBU octylate, DBU oleate, DBU Phenol salt, DBU paratoluenesulfonate, DBU3Me- △ ^4- THPA salt, DBU4Me- △ ^4- THPA salt, 1,
5-diazabicyclo [4.3.0] nonene-5 (hereinafter DBN)
Abbreviated. ), DBN formate, DBN acetate, DBN propionate, DBN butyrate, DBN octylate, DBN oleate, D
BN phenol salt, DBN paratoluenesulfonate, DBN3M
e- △ ^4- THPA salt, DBN4Me- △ ^4- THPA salt and the like can be mentioned. Among these, DBU, DBU octylate, DBU phenol salt, DBU3Me- △ ^4- THPA
Salt, DBU4Me- △ ^4- THPA salt, DBN, DBN3Me- △ ^4- THPA
The use of salts, DBN4Me- △ ^4- THPA salts, is particularly preferred.

The salts of DBU or DBN can be easily produced by mixing DBU or DBN with an organic acid or phenol in an equimolar ratio and heating to about 50 to 150 ° C.

The amount of the catalyst used is 0.001 to 10 based on Me- △ ^4- THPA.
%, Preferably 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. Especially,
The residue obtained by performing a stereoisomerization reaction of Me- △ ^4- THPA using DBU or DBN as a catalyst and recovering a liquid product by distillation forms a Me- △ ^4- THPA salt of DBU or DBN. Suitable for reuse.

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.

Effects of the Invention According to the method of the present invention, the production of high-boiling by-products can be reduced, and thus a stereoisomer mixture of Me- △ ^4- THPA can be obtained 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.

Example 1 Cis-3Me- 口⁴ was added to a 300 ml four-necked flask equipped with a stirrer.
100 parts of -THPA (melting point 61 ° C) and 0.1 part of DBU (manufactured by San-Apro) were charged to cis-3Me- △ ^4- THPA, and the isomerization reaction was performed at 150 ° C for 3 hours under stirring in a nitrogen atmosphere. . After the reaction, the product containing the catalyst was distilled under reduced pressure to obtain 96.8 parts of a pale yellow transparent liquid (Gardner color number <1).

The freezing point of the liquid product was 0 ° C., and analysis by gas chromatography revealed that cis-3Me- △ ^4- THPA27%
And it was a mixture of trans -3Me- △ ⁴ -THPA73%. 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 14 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 ratio, Gardner color number and freezing point of the obtained product. The catalysts DBU and DBU
The salts used were those manufactured by San Apro, and the DBN used was that manufactured by Tokyo Chemical Industry Co., Ltd. The DBN salts used were those prepared from the above DBN and acids or phenol.

Examples 15-18 cis-3Me- △ ^4- THPA and 4Me- △ ^4- THPA total 100
Parts were used in the proportions shown in Table 2 and DBU or DBN was used as a catalyst.
Except as shown in the table, the isomerization reaction and the distillation under reduced pressure were performed in the same manner as in Example 1. Table 2 shows the recovery (parts) of the obtained product, the ratio of cis / trans form of cis-3Me- △ ^4- THPA, the Gardner color number, and the freezing point.

Comparative Example 1 As a catalyst, 2 parts of dibutylaniline (manufactured by Tokyo Chemical Industry Co., Ltd.) was used in place of 0.1 part of DBU, and the reaction condition was 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 5 ° C. for 5 hours. 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 An isomerization reaction was carried out in the same manner as in Example 1 except that 5 parts of calcium oxide was used instead of 0.1 part of DBU as a catalyst and the reaction conditions were set at 200 ° 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-isomer and 20% trans-isomer. Stereoisomerization in the presence of this catalyst revealed that the rate of the isomerization reaction to the trans-isomer was slow. .

Comparative Example 3 The isomerization reaction and distillation under reduced pressure were carried out in the same manner as in Example 1 except that 1 part of sodium hydroxide was used instead of 0.1 part of DBU as the catalyst and the reaction conditions were set at 200 ° C. for 3 hours. Was. 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 19 An isomerization reaction and distillation under reduced pressure 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 98.3 parts were recovered. The distillation residue was 4.9 parts, but the net difference from Example 1 and 3.2 parts was 1.7
Department.

The freezing point of the distillate was 5 ° C, and as a result of gas chromatography analysis, it was a mixture of 35% of the cis form and 65% of the trans form. This proved that the distillation residue containing the catalyst could be used repeatedly.

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) Methyl-delta-4-tetrahydrophthalic anhydride is heated in the presence of diazabicycloundecene or a salt or diazabicyclononene or a salt thereof. A method for stereoisomerizing tetrahydrophthalic anhydride. 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).