Preparation method of 4-methylphthalic anhydride compound

Abstract

The invention discloses a preparation method of a 4-methylphthalic anhydride compound, and the specific method is as follows: in the presence of a solvent, 4-methyl-1, 2, 3, 6-tetrahydrophthalic anhydride reacts with a dehydrogenation reagent to prepare the 4-methylphthalic anhydride, 1, 3-dihalo-5, 5-dimethyl hydantoin is used as a dehydrogenation reagent. The method can overcome the problems of overhigh cost and low production efficiency in the existing method for preparing 4-methylphthalic anhydride, and has the advantages of high yield, convenience and safety in operation, low production cost and environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of organic chemical synthesis technology, and in particular to a method for preparing a 4-methylphthalic anhydride compound. Background Technology

[0002] 4-Methylphthalic anhydride is a known compound commonly used as an important raw material in organic synthesis. It is also used as a solvent, dye intermediate, and paint additive, for example, as an intermediate for the herbicide imidacloprid.

[0003] Several methods are known to be used to prepare 4-methylphthalic anhydride. For example, patent literature reports a method using 4-methyltetrahydrophthalic anhydride as a raw material and liquid bromine, thioyl chloride, or trichloroisocyanuric acid as a dehydrogenation reagent.

[0004] However, existing technologies for preparing 4-methylphthalic anhydride suffer from problems such as environmental pollution, low production efficiency, or excessively high costs. Summary of the Invention

[0005] [Technical Issues] To overcome the problems of high cost and low production efficiency in existing methods for preparing 4-methylphthalic anhydride, this invention proposes a method for preparing 4-methylphthalic anhydride that is high-yield, easy and safe to operate, low-cost, and environmentally friendly.

[0006] [Technical Solution] The purpose of this invention is to provide a method for preparing 4-methylphthalic anhydride compounds, the synthetic route of which is as follows:

[0007] The specific method is as follows: In the presence of a solvent, 4-methyl-1,2,3,6-tetrahydrophthalic anhydride reacts with a dehydrogenating agent to prepare the 4-methylphthalic anhydride; the dehydrogenating agent is 1,3-dihalo-5,5-dimethylhydantoin.

[0008] In one embodiment of the present invention, the solvent is a polar aprotic organic solvent.

[0009] In one embodiment of the present invention, the solvent is one or more of dimethyl sulfoxide (DMSO), N,N-dialkylformamide, and N,N-dialkylacetamide; wherein the alkyl group is an alkyl group having 1 to 3 carbon atoms.

[0010] In one embodiment of the present invention, the solvent is one or more of dimethyl sulfoxide (DMSO), N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-diethylformamide.

[0011] Preferably, the solvent is N,N-dimethylformamide.

[0012] In one embodiment of the present invention, the dehydrogenating agent is one or more of 1,3-dibromo-5,5-dimethylhydantoin, 1,3-dichloro-5,5-dimethylhydantoin, and 1,3-diiodo-5,5-dimethylhydantoin.

[0013] 1,3-Dibromo-5,5-dimethylhydantoin is shown in the following formula (2):

[0014] 1,3-Dibromo-5,5-dimethylhydantoin, also known as 1,3-dibromo-5,5-dimethyl-2,4-imidazolidinedione, is a known compound that is commercially available.

[0015] In one embodiment of the present invention, the molar ratio of 4-methyl-1,2,3,6-tetrahydrophthalic anhydride to the dehydrogenating agent is 1:2.

[0016] In one embodiment of the present invention, the reaction conditions are: 50-120℃, 0.5-2h.

[0017] Preferably, the reaction temperature is 50℃, 55℃, 60℃, 65℃, 70℃, 80℃, 90℃, 100℃, 110℃ or 120℃.

[0018] More preferably, the reaction temperature is 90°C.

[0019] If the reaction temperature is below the aforementioned range, the reaction will proceed with difficulty or may even fail to occur. If the reaction temperature is above the aforementioned range, problems such as increased impurity content and higher tar content are likely to occur. In particular, the temperature must not exceed the boiling point of the polar aprotic organic solvent; otherwise, the concentrations of various substances in the reaction system will change as the reaction proceeds, thus affecting the reaction progress and even the final reaction product.

[0020] In one embodiment of the present invention, the preparation method further includes solvent removal and distillation separation steps.

[0021] In one embodiment of the present invention, when N,N-dimethylformamide is used as a polar aprotic organic solvent, the chemical reaction process is as follows:

[0022] After the reaction between 4-methyl-1,2,3,6-tetrahydrophthalic anhydride and 1,3-dibromo-5,5-dimethylhydantoin is completed, further steps such as water addition and condensation, solvent removal and / or distillation separation can be performed to obtain the final product 4-methylphthalic anhydride.

[0023] Beneficial effects: The reaction conditions of this invention are mild and easy to operate, making it very easy to meet the requirements of safe production. The 1,3-dibromo-5,5-dimethylhydantoin used in this invention is inexpensive, readily available, and easy to operate, further making it easy to meet the requirements of safe production. Detailed Implementation

[0024] The present invention will be further described below by way of embodiments. However, these embodiments are merely illustrative examples of preferred embodiments of the invention, and the scope of protection of the invention should not be construed as being limited to these embodiments. Unless otherwise specified, all raw materials are commercially available products.

[0025] Example 1 A method for preparing a 4-methylphthalic anhydride compound, comprising the following steps: First, 0.1 mol of 4-methyltetrahydrophthalic anhydride and 50 mL of N,N-dimethylformamide were mixed in a reaction vessel. The mixture was heated and maintained at 90 °C. A solution of 20 mL of N,N-dimethylformamide containing 0.2 mol of 1,3-dibromo-5,5-dimethylhydantoin was added dropwise over 30 minutes. A sample was then taken for TLC analysis. The reactants were observed to gradually disappear, and new products were formed. After one hour, once all the reactants had reacted, the temperature was lowered to room temperature. The reaction solution was then diluted with 700 mL of water, resulting in precipitation. The precipitate was filtered, and the resulting filter cake was dissolved in 50 mL of ethyl acetate and sonicated. After complete dissolution, the mixture was filtered again, and the filtrate was rotary evaporated to obtain the final product, 13.4 g of 4-methylphthalic anhydride, with a yield of 82.6%.

[0026] Example 2 A method for preparing a 4-methylphthalic anhydride compound, comprising the following steps: First, 0.1 mol of 4-methyltetrahydrophthalic anhydride and 50 mL of N,N-diethylformamide were mixed in a reaction vessel. The mixture was heated and maintained at 90 °C. A solution of 20 mL of N,N-diethylformamide containing 0.2 mol of 1,3-dibromo-5,5-dimethylhydantoin was added dropwise over 30 minutes. A sample was then taken for TLC analysis. The reactants gradually disappeared, and new products were formed. After one hour, once all the reactants had reacted, the temperature was lowered to room temperature. The reaction solution was then diluted with 700 mL of water, resulting in precipitation. The precipitate was filtered, and the resulting filter cake was dissolved in 50 mL of ethyl acetate and sonicated. After complete dissolution, the mixture was filtered again, and the filtrate was rotary evaporated to obtain the final product, 12.8 g of 4-methylphthalic anhydride, with a yield of 78.8%.

[0027] Example 3 A method for preparing a 4-methylphthalic anhydride compound, comprising the following steps: First, 0.1 mol of 4-methyltetrahydrophthalic anhydride was mixed with 50 mL of N,N-dimethylacetamide in a reaction vessel. The mixture was heated and maintained at 90 °C. A solution of 20 mL of N,N-dimethylacetamide containing 0.2 mol of 1,3-dibromo-5,5-dimethylhydantoin was added dropwise over 30 minutes. A sample was then taken for TLC analysis. The reactants gradually disappeared, and new products were formed. After one hour, once all the reactants had reacted, the temperature was lowered to room temperature. The reaction solution was then diluted with 700 mL of water, resulting in precipitation. The precipitate was filtered, and the resulting filter cake was dissolved in 50 mL of ethyl acetate and sonicated. After complete dissolution, the mixture was filtered again, and the filtrate was rotary evaporated to obtain the final product, 12.6 g of 4-methylphthalic anhydride, with a yield of 77.5%.

[0028] Examples 4 to 7 Except as shown in the table below, Examples 4 to 7 were carried out in the same manner as Example 1, and the results of the weight, content and yield of 4-methylphthalic anhydride as the final product are listed in Table 1 below.

[0029] Comparative Examples 1 to 4 Except as shown in the table below, Comparative Examples 1 to 4 were performed in the same manner as in Example 1, and the results of the weight, content and yield of 4-methylphthalic anhydride as the final product are listed in Table 1 below.

[0030] Table 1

[0031] Note: In Comparative Example 3, the solvent was an equimolar mixture of chlorobenzene and pyridine, wherein the molar amount of chlorobenzene and pyridine was 0.202 mol each.

[0032] As can be seen from Table 1, by comparison, the product yield obtained by the technical solution of this application is higher, the cost is lower, the post-processing method is simpler, and the experimental operation is safer.

[0033] The embodiments described herein are merely illustrative examples of preferred embodiments of the present invention. Those skilled in the art can make various modifications to the described embodiments based on the disclosure of this invention; however, any modifications that do not depart from the essence of the invention still fall within the scope defined by the appended claims.

Claims

1. A method for producing a 4-methylphthalic anhydride compound, characterized by comprising: reacting a 4-methylphthalic acid compound with a carbodiimide compound in the presence of a base. The synthetic route is as follows: The specific method is: In the presence of a solvent, 4-methyl-1,2,3,6-tetrahydrophthalic anhydride is reacted with a dehydrogenation reagent to obtain the 4-methylphthalic anhydride; the dehydrogenation reagent is 1,3-dihalo-5,5-dimethylhydantoin.

2. The production method according to claim 1, characterized by, The solvent is a polar aprotic organic solvent.

3. The production method according to claim 2, characterized by, The solvent is one or more of dimethyl sulfoxide, N,N-dialkyl formamide, and N,N-dialkyl acetamide; wherein the alkyl group is an alkyl group having 1 to 3 carbon atoms.

4. The production method according to claim 3, characterized by, The solvent is one or more of dimethyl sulfoxide, N,N-dimethyl formamide, N,N-dimethyl acetamide, and N,N-diethyl formamide.

5. The preparation method according to claim 1, characterized in that, The dehydrogenation reagent is one or more of 1,3-dibromo-5,5-dimethylhydantoin, 1,3-dichloro-5,5-dimethylhydantoin, and 1,3-diiodo-5,5-dimethylhydantoin.

6. The method of claim 1, wherein, The molar ratio of 4-methyl-1,2,3,6-tetrahydrophthalic anhydride to the dehydrogenation reagent is 1:2-2.

5.

7. The preparation method according to claim 1, characterized in that, The reaction conditions are: 50-120℃, 0.5-2h.

8. The method of claim 1, wherein, The steps of solvent removal and distillation separation are also included.

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