JPS5819665B2 - Succinyl succinate diester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides succinyl succinic acid dialkyl ester (cyclohexa-1,4-diene-2,5-diol-1,4
-Dicarboxylic acid dialkyl ester).

The compound of the present invention is a substance useful as a raw material for quinacridone pigments, etc., and has been conventionally produced from succinic acid diester or halogenated acetyl acetate in the presence of an alkali catalyst such as an alkali metal or its alcoholide, ammonia, or a secondary amine. It is known that this method can be used, and various studies have been conducted on the former method in particular because raw materials are easily available and it is economically inexpensive.

That is, as a method for producing succinyl succinic acid diester from succinic acid diester, for example, USP 3024
268, Org, 5ynth, 45 (1965), 25
~28, Org, React, 1.274~2
75 and 283-284, Organic Chemistry Handbook (Gihodo, 1972) 430, etc., succinic acid is usually prepared in a solvent such as ethanol or an aromatic hydrocarbon in the presence of sodium or sodium ethoxide, etc. This is a condensation reaction of acid diethyl ester.

As mentioned above, the methods shown in these conventionally known patents and general technical documents all specifically relate to ethyl esters; It is known that there are differences in performance (Am.

404.287, etc.), in fact, according to the knowledge of the present inventors, for example, as a result of attempting the same reaction for ethyl ester and methyl ester according to the method described in the above-mentioned USP 3024268, in the case of the former, the patent As shown in Example 1 of the specification, the desired diethyl succinyl succinate was obtained with a yield of nearly 80%, but in the latter case, dimethyl succinyl succinate was obtained with a yield of 50 to 60%. It was recognized that this could only be achieved by increasing the rate.

The present invention relates to an improvement in the method for producing such dialkyl succinyl succinates, and in particular to the production of succinic acid dialkyl esters in a solvent consisting of aromatic or aliphatic hydrocarbons or aliphatic lower alcohols and dimethyl sulfoxide (DMSO) in the presence of an alkali metal alcoholade. It is characterized in that the acid dialkyl ester is subjected to a condensation reaction and then neutralized.

According to the method of the present invention, the desired succinyl succinic acid diester can be obtained in high yield, making it possible to carry out the process economically.

To explain in more detail below, lower alkyl esters are generally used as dialkyl succinates as starting materials, and the corresponding dialkyl succinyl succinates can be obtained. In this case, it is necessary to convert the ester group into a carboxyl group by dynamic hydrolysis during the synthesis, and as a result, the alcohol residue becomes unnecessary, so from an economical point of view, it is not suitable for industrial use. Cheap methyl or ethyl esters are preferred, with the former being the most advantageous.

Further, as the alkali metal alcoholade, a sodium or potassium alkyl alcoholate is used, and the alcoholade corresponding to the alkyl group of the raw material dialkyl succinate is usually used, for example, in the case of methyl ester, methylate is used.

This alkali metal alcoholade may be separately prepared and added to the reaction system, or may be used as it is by reacting the alkali metal and alcohol prior to the condensation reaction. It may also be produced by reaction with alcohol produced during the reaction using only an alkali metal.

Conventionally known methods generally required at least 2 mol or more of the alkali metal alcoholide to be used per 1 mol of raw diester succinate, but in the method of the present invention, about 1.0 to 16 mol is sufficient. You can get the following effect.

Of course, there is no problem if the molar ratio is less than 1.0 or more than 1.6, but if it is too small, the reaction rate will be slow and the yield will not be sufficient. However, the corresponding effect cannot be obtained and it is uneconomical.

Therefore, a molar ratio of about 0.8 to 3 is usually appropriate, preferably a molar ratio of <1.0 to 1.6 as described above.

The solvent used is a mixed solvent consisting of DMSO and at least one of aromatic or aliphatic hydrocarbons or aliphatic lower alcohols. Examples of the hydrocarbon include aromatic compounds such as benzene, toluene, ethylbenzene, xylene, etc.
Chain-like aliphatic hydrocarbons such as hexane, heptano, and octane or cyclic aliphatic hydrocarbons such as cyclopenkune, cyclohexane, and methylcyclohexane are used, and as the alcohol, methanol, ethanol, etc. corresponding to the raw material dialkyl succinate are used. It will be done.

Among these, compounds that have a boiling point of 100 to 150°C under normal pressure and that hardly form an azeotrope with the alcohol produced during the reaction, such as aromatic hydrocarbons such as xylene and ethylbenzene, are the most practical. It is.

The content of DMSO in the mixed solvent of these and DMSO is usually about several percent to obtain a sufficient effect, and even if a large amount is used, there is no noticeable difference in the yield of the desired product.

On the contrary, the higher the content, the more difficult it becomes to handle the reaction solution after the reaction is completed, and it is also uneconomical, so it is not practical.
Therefore, it can be said that it is usually desirable to use it in a range of 5 to 20% by weight.

In addition, in the method of the present invention, as shown in the examples below, D
Mixing MSO significantly improves the yield of the target product, especially in the case of methyl esters, which could not be achieved with conventional methods, but on the other hand, when only DMSO is used as a solvent, it is possible to obtain A sufficient yield cannot be obtained as in the case of using only

The reaction is generally carried out under stirring at 60-130°C, preferably at 1
It is carried out by heating to 00-120℃, 1-4
A sufficient yield can be obtained in about hours.

Since the product thus obtained is a dialkali metal salt, a post-treatment including a neutralization treatment is performed subsequent to the above condensation reaction.

There are no particular restrictions on the post-treatment after the condensation reaction (it can be easily carried out by conventionally known methods).

For example, the precipitate of the dialkyl metal salt of succinyl succinate obtained by the net side reaction is collected by filtration, dissolved in water, and then neutralized by adding acid to precipitate the dialkyl succinate dialkyl ester. A method of separating crystals, or by adding a large amount of water to the slurry of the raw acid after the condensation reaction, transferring and dissolving the dialkali metal salt of succinyl succinic acid dialkyl ester into the aqueous layer, separating this aqueous layer from the organic layer, and then adding the acid to the slurry resulting from the condensation reaction. In addition, after the condensation reaction, an acid is directly added to the reaction solution to neutralize it, and the resulting succinyl succinic acid diester is separated into an organic solvent layer. Any method may be used, such as transferring and dissolving the organic solution, separating this organic solution from the aqueous layer, concentrating it, crystallizing it, and separating it.

Further, in the neutralization treatment, acidic substances such as inorganic salts such as sulfuric acid, hydrochloric acid, carbonic acid, and phosphoric acid, organic acids such as formic acid, acetic acid, and oxalic acid, or acidic salts thereof are usually used.

In addition, in order to neutralize the dialkali metal salt of succinyl succinic acid diester by adding an acid directly to the reaction solution after the condensation reaction and liberate the succinyl succinic acid diester, a strong inorganic acid such as sulfuric acid or hydrochloric acid was used as the acidic substance. In this case, some by-products of the condensation reaction are also transferred into the organic solvent as organic acidic substances.

In order to remove this, it is necessary to further neutralize the alkali injection material, but in order to transfer only the by-products into the aqueous phase as an alkali salt, it is preferable to use a weakly alkaline material such as an alkali carbonate.

In addition, when an acid salt such as sodium bicarbonate or potassium bicarbonate is used as the acidic substance to be removed in the neutralization treatment, the dialkali metal salt of succinyl succinic acid diester is liberated into succinyl succinic acid diester, and the by-product is an alkali metal. It is very advantageous because it becomes a salt and can be separated as an organic phase and an aqueous phase, respectively, and the complicated steps described above can be omitted. When used in the synthesis of quinacridone, it is possible to use the reaction solution for the next step as it is without crystallizing and separating it from the organic phase.

Hereinafter, representative examples of the method of the present invention will be given and more specifically explained along with comparative tests.

Of course, it goes without saying that the present invention cannot be limited in any way by these examples.

In the examples, "parts" represent parts by weight.

Example 1 176 parts of xylene, 025 parts of DMS, and 30 parts of sodium methylate were placed in a reactor equipped with a stirrer, a distillation device, and a thermometer.
and 58.4 parts of dimethyl succinate were added, and the temperature was raised to 105 to 110° C. under stirring in a nitrogen stream, and the reaction was allowed to proceed for 2 hours while methyl alcohol by-produced during the reaction was distilled off through a distillation apparatus.

After the reaction was completed, the reaction solution was cooled to 50 to 60°C, and the methyl alcohol was distilled off under reduced pressure. Then, 350 parts of xylene was newly added, and then 200 parts of a 15% sulfuric acid aqueous solution was gradually added, and the mixture was stirred vigorously for about 10 minutes. After stirring, the mixture was allowed to stand still.

After standing still for about 10 to 20 minutes, remove the aqueous layer that separated into the lower layer, gradually add 50 parts of a 10% sodium carbonate aqueous solution to the remaining xylene layer, repeat the same liquid separation operation and wash with water, and then make the final layer. The xylene was distilled off from the xylene layer obtained under reduced pressure to crystallize dimethyl succinyl succinate.

This was collected by filtration, washed with a small amount of methyl alcohol, and then dried to obtain 36 g of crystals with a melting point of 153-154°C (
yield of 79% of theory).

Note that even when the reaction time of the condensation reaction was shortened to 1 hour, a yield of 78% was obtained.

Example 2 The condensation reaction and neutralization treatment were performed in the same manner as in Example 1 except that the content of DMSO in the mixed solvent was changed.
The yield of succinyl succinic acid dimethyl ester (relative to theoretical amount, hereinafter the same) was as follows.

Note that /161 and //67 represent the case of using only xylene and the case of only DMSO, respectively.

Example 3 The condensation reaction and neutralization treatment were carried out in the same manner as in Example 1 except that the amount of sodium methylate used (molar ratio to dimethyl succinate) was changed. As a result, the yield of dimethyl succinyl succinate was was as follows.

Example 4 The same procedure as in Example 1 was performed except that xylene, which was part of the solvent, was replaced with n-hexane, methylcyclohexane, benzene, or ethylbenzene, and the reaction conditions were changed. The results are shown below.

Example 5 Using the same reactor as in Example 1, add 88 parts of xylene and 12 parts of metallic sodium, and add 120 parts of methyl alcohol while stirring warmly while passing a small amount of nitrogen gas to cut off contact with the atmosphere. was gradually added, and the reaction was allowed to proceed for about 1 hour. After the metallic sodium completely disappeared, excess methyl alcohol was distilled off.

Next, after cooling this liquid to 60°C, 025 parts of DMS, 88 parts of xylene, and 58.4 parts of dimethyl succinate were added, and the reaction was carried out in the same manner as in Example 1. After post-treatment, dimethyl succinyl succinate was added. Ester 35.8
(yield 78.5%).

Example 6 The reaction and post-treatment were carried out in the same manner as in Example 5, except that ethyl alcohol was used instead of methyl alcohol and 70 parts of diethyl succinate was used instead of 58.4 parts of dimethyl succinate. 1.2 parts of succinyl succinic acid diethyl ester mP126-7°C (theoretical yield 80.5%) was obtained.

Example 7 158 parts of methyl alcohol, 25 parts of DMSO, 30 parts of sodium methylate, and 584 parts of dimethyl succinate were placed in a reactor equipped with a stirrer, a distillation device, and a thermometer, and the temperature was raised under stirring in a nitrogen stream. The mixture was reacted under reflux for 8.0 hours.

After the reaction was completed, 500 parts of xylene was newly added, and the methyl alcohol was distilled off under reduced pressure.
At 60° C., 200 parts of a 15% sulfuric acid aqueous solution was gradually added, and the mixture was vigorously stirred for about 10 minutes and then allowed to stand.

After standing still for about 10 to 20 minutes, the aqueous layer separated into the lower layer was removed, and 50 parts of a 10% aqueous sodium carbonate solution was gradually added to the remaining xylene layer. After repeating the same separation operation and washing with water, the final product was obtained. The xylene layer was distilled off under reduced pressure to crystallize dimethyl succinyl succinate.

This was collected by filtration, washed with a small amount of methyl alcohol, and then dried.

Dimethyl succinyl succinate was obtained in a yield (based on theory) of 53.7%.

On the other hand, when reaction, neutralization, and separation were carried out in the same manner as above except that 025 parts of DMS was not added, the yield (relative to theoretical amount) of succinyl succinic acid dimethyl ester was 12
%Met.

Claims (1)

[Claims] 1. Succinyl succinate, which is characterized by subjecting dialkyl succinate to a condensation reaction in a solvent consisting of an aromatic or aliphatic hydrocarbon or aliphatic lower alcohol and dimethyl sulfoxide in the presence of an alkali metal alcoholade, followed by neutralization. Method for producing acid dialkyl ester.