JP5344570B2 - Method for purifying 3,4-dialkoxythiophene derivatives - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of purification to give a high purity 3,4-dialkoxythiophene derivative. <P>SOLUTION: This method for purifying the 3,4-dialkoxythiophene derivative comprises (A) a process of mixing for making a contact of an organic layer containing the dialkoxythiophene derivative with an aqueous layer containing an acid, (B) a process of separating the organic layer and aqueous layer, and recovering the organic layer and (C) a process of extracting the 3,4-dialkoxythiophene derivative from the recovered organic layer, and an electroconductive polymer obtained by using the obtained 3,4-dialkoxythiophene derivative as a raw material can be suitably used as a solid electrolytic capacitor, electroconductivity-imparting agent or the like, since it has high transparency in addition to the high electroconductivity. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for purifying 3,4-dialkoxythiophene derivatives.

  Aromatic monomers represented by pyrrole derivatives, aniline derivatives, thiophene derivatives and the like have been used for the production of conductive polymers, and various studies have been conducted for practical use. In particular, a polymer using a thiophene derivative as a raw material has high transparency in addition to high conductivity, so that the thiophene derivative is an important aromatic monomer.

  Among thiophene derivatives, 3,4-ethylenedioxythiophene has been put into practical use as a raw material for solid electrolytic capacitors, conductivity imparting agents and the like.

  As a method for producing this 3,4-ethylenedioxythiophene, a production method is known in which 3,4-dimethoxythiophene is heated to reflux in toluene together with ethylene glycol in the presence of paratoluenesulfonic acid (Non-patent Document 1). ).

  On the other hand, 3,4-dimethoxythiophene is also known to be obtained by a production method in which 3,4-dibromothiophene is reacted with metallic sodium in the presence of potassium iodide and copper oxide in a methanol solution (non-patent document). Reference 2).

  Thus, dialkoxythiophene represented by 3,4-dimethoxythiophene is an important raw material for the thiophene derivative.

  However, 3,4-dimethoxythiophene obtained by the previous production method has a low purity, and when 3,4-ethylenedioxythiophene is produced from this 3,4-dimethoxythiophene as a raw material, the low-purity 3,4 -Ethylenedioxythiophene is obtained and is very difficult to purify. Therefore, it is necessary to purify when producing 3,4-dimethoxythiophene.

  Known methods for purifying aromatic monomers such as thiophene derivatives include distillation, recrystallization, chromatography, extraction and the like.

  By-product can be reduced by purifying the obtained 3,4-dimethoxythiophene by distillation. For example, the purity of 3,4-dimethoxythiophene can be improved to about 96.5%. The main by-product is 2,4-dimethoxythiophene.

  Even if it is attempted to further increase the purity by distillation purification, the by-product is a structural isomer, so that the difference in boiling point is very small and separation is extremely difficult.

Synthetic Communications, 28 (12), 2237-2244 (1998) Tetrahedron Letters, 45, 6049-6050 (2004)

  An object of the present invention is to provide a purification method which gives a highly pure 3,4-dialkoxythiophene derivative.

  As a result of intensive studies by the inventors in order to solve the above problems, the step of mixing and contacting the organic layer containing the dialkoxythiophene derivative and the aqueous layer containing the acid (A), separating the organic layer and the aqueous layer, A step of recovering the organic layer (B), and a step of extracting the 3,4-dialkoxythiophene derivative represented by the following general formula (1) from the recovered organic layer (C) 3,4-dialkoxythiophene derivative According to this purification method, it was found that by-products such as 2,4-dialkoxythiophene derivatives can be removed, and that high-purity 3,4-dimethoxythiophene derivatives can be obtained, thereby completing the present invention. It was.

  The first invention is a step of mixing and contacting an organic layer containing a dialkoxythiophene derivative and an aqueous layer containing an acid, and a step of separating the organic layer and the aqueous layer and recovering the organic layer (B ), A method of purifying the 3,4-dialkoxythiophene derivative, which includes a step (C) of removing the recovered organic layer and removing the 3,4-dialkoxythiophene derivative represented by the following general formula (1).

（式（１）中のＲ_１、Ｒ_２は互いに同じであっても異なっていてもよい炭素数１〜２０の鎖状又は分岐鎖状のアルキル基又はアリール基を表す。）

(R ₁ and R _{2 in} Formula (1) represent a linear or branched alkyl group or aryl group having 1 to 20 carbon atoms that may be the same or different from each other.)

  In a second invention, the dialkoxythiophene derivative is a dialkoxythiophene derivative obtained by reacting a halogenated thiophene represented by the general formula (2) with an alkali metal alkoxide in an alcohol solvent. A method for purifying a 3,4-dialkoxythiophene derivative according to the first aspect of the invention.

（式（２）中のＸは互いに独立であっても異なってもよいフッ素原子、塩素原子、臭素原子又はヨウ素原子のいずれかを表す。）

(X in Formula (2) represents either a fluorine atom, a chlorine atom, a bromine atom or an iodine atom which may be independent or different from each other.)

  A third invention is a method for purifying a 3,4-dialkoxythiophene derivative according to the first or second invention, wherein the acid is hydrochloric acid, paratoluenesulfonic acid, or sulfuric acid.

  A fourth invention uses any one of the first to third inventions characterized in that the aqueous layer has an acid concentration of 0.1 to 30 mol% with respect to the dialkoxythiophene derivative. It is a purification method of the described 3,4-dialkoxythiophene derivative.

  According to a fifth aspect of the present invention, there is provided a 3,4-dialkoxythiophene derivative purified according to any one of the first to fourth aspects, which has a purity of at least 99.00%. Dialkoxythiophene derivatives.

  According to the purification method of the present invention, the 3,4-dialkoxythiophene derivative represented by the general formula (1) can be obtained with high purity.

  First, the step (A) in which an organic layer containing a dialkoxythiophene derivative and an aqueous layer containing an acid are mixed and contacted will be described.

  The present invention is characterized by using a dialkoxythiophene derivative containing at least a 3,4-dialkoxythiophene derivative represented by the following general formula (1).

R ₁ and R ₂ in the general formula (1) represent a linear or branched alkyl group having 1 to 20 carbon atoms or an aryl group which may be the same or different from each other.

Examples of R ₁ and R ₂ include a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, an isopropyl group, and an isobutyl group. Among these, a methyl group, an ethyl group, a propyl group, and a butyl group are preferable from the viewpoint of reactivity and handleability, and a methyl group is more preferable.

  Examples of the 3,4-dialkoxythiophene derivative represented by the general formula (1) include 3,4-dimethoxythiophene, 3-methoxy-4-ethoxythiophene, 3,4-diethoxythiophene, and 3-methoxy. -4-propoxythiophene, 3-ethoxy-4-propoxythiophene, 3,4-dipropoxythiophene, 3-butoxy-4-methoxythiophene, 3-butoxy-4-ethoxythiophene, 3-butoxy-4-propoxythiophene, Examples include 3,4-dibutoxythiophene.

Examples of the acid used in the present invention include organic acids such as formic acid, acetic acid, methanesulfonic acid and paratoluenesulfonic acid, and inorganic acids such as hydrochloric acid, phosphoric acid, nitric acid and sulfuric acid.
Among these, paratoluenesulfonic acid, hydrochloric acid, and sulfuric acid are preferable from the viewpoint of handling, and paratoluenesulfonic acid and hydrochloric acid are more preferable.

  One type or two or more types of acids can be used.

  0.1-30 mol% is preferable with respect to the dialkoxy derivative, and the concentration of the acid in the aqueous layer is more preferably 10-20 mol%. When the acid concentration is less than 0.1 mol%, the 2,4-dialkoxythiophene derivative or the like may not be completely removed, and when it exceeds 30 mol%, there is a drawback that the recovery rate is lowered.

  0.05-3.0 are preferable and, as for pH of the water layer which added the acid, 0.1-1.0 are more preferable. When the pH is less than 0.05, the recovery rate decreases, and when the pH exceeds 3.0, there is a drawback that 2,4-dialkoxythiophene derivatives and the like cannot be completely removed.

  Examples of the organic solvent used in the organic layer include aromatic hydrocarbons and aliphatic hydrocarbons.

  Examples of the aromatic hydrocarbon include toluene and xylene, and examples of the aliphatic hydrocarbon include pentane, hexane, and heptane. Hexane is preferable from the viewpoint of handling.

  The amount of the organic solvent used is preferably 0.01 to 100 times, more preferably 0.1 to 30 times, and particularly preferably 1.0 to 10 times the weight of the dialkoxythiophene derivative. When the organic solvent is less than 0.01 times, the recovery rate is lowered, and when it exceeds 100 times, there is a disadvantage that costs are increased.

  The solubility of the dialkoxythiophene derivative in acid is such that the solubility in aqueous solution of hydrochloric acid having a pH of 1.0 (25 ° C.) is 1.0 to 10 g / L for 3,4-dialkoxythiophene, while 2,4- Dialkoxythiophene is 50 to 100 g / L. The present invention is a method for purification using the difference in solubility of the dialkoxythiophene derivative in acid. That is, by contacting and mixing the organic layer and the aqueous layer, a 3,4-dialkoxythiophene derivative that is difficult to dissolve in an acid due to a difference in solubility in acid, and a 2,4-dialkoxythiophene that is easily soluble in acid. Derivatives and the like can be separated.

The temperature at which the organic layer containing the dialkoxythiophene derivative and the aqueous layer containing the acid are mixed and contacted is not particularly limited, and can be easily extracted even at room temperature.
Further, the mixing contact time is preferably 1 to 120 minutes, more preferably 2 to 60 minutes, and particularly preferably 5 to 30 minutes. If less than 1 minute, by-products such as 2,4-dimethoxythiophene derivatives cannot be sufficiently dissolved in the aqueous layer, and if over 120 minutes, 3,4-dimethoxythiophene derivatives are dissolved in the aqueous layer. It is for having.

  The ratio when the organic layer and the aqueous layer are mixed and contacted is preferably 10 to 300 ml of the aqueous layer adjusted to pH 1.0, more preferably 50 to 200 ml, and particularly preferably 100 ml with respect to 100 ml of the organic layer. If it is less than 10 ml, a by-product such as a 2,4-dimethoxythiophene derivative cannot be sufficiently dissolved in the aqueous layer. If it exceeds 300 ml, the 3,4-dimethoxythiophene derivative is dissolved in the aqueous layer, and the cost is low. There is a disadvantage that will be applied.

  The method of mixing and contacting the organic layer and the aqueous layer is specifically a method of stirring the aqueous layer in a state where the sample is dissolved or dispersed in an organic solvent. The stirring method is not particularly limited. For example, the stirring method using a stirring bar or a stirring rod using a flask, the stirring method using an ultrasonic vibration device, the stirring by shaking with a separatory funnel or the like. From the viewpoint of stirring efficiency and mass production, a method of stirring with a stirrer or a stirring bar using a flask is preferable.

  Next, the process (B) which isolate | separates the said organic layer and the said water layer, and collect | recovers an organic layer is demonstrated.

  The mixture of the organic layer and the aqueous layer obtained in step (A) can be easily separated at room temperature, and can be separated by a separatory funnel to recover only the organic layer. Further, anhydrous sodium sulfate may be added to the separated organic layer for dehydration.

  Next, the step (C) of removing the solvent from the collected organic layer and taking out the 3,4-dialkoxythiophene derivative represented by the general formula (1) will be described.

  Examples of the method for removing the solvent include a method using vacuum concentration. Concentration under reduced pressure is a step of concentrating a solution by extracting a solvent component while heating or depressurizing at room temperature. According to the vacuum concentration, a large amount of solution can be concentrated, and the solvent can be recovered and reused.

  The manufacturing method of the dialkoxythiophene derivative of this invention is demonstrated.

  A dialkoxythiophene derivative can be produced by reacting a halogenated thiophene represented by the following general formula (2) with an alkali metal alkoxide in an alcohol solvent.

  X in the general formula (2) represents a fluorine atom, a chlorine atom, a bromine atom or an iodine atom which may be independent or different from each other.

  Examples of the halogenated thiophene represented by the general formula (2) include 3,4-difluorothiophene, 3,4-dichlorothiophene, 3,4-dibromothiophene, 3,4-diiodothiophene, 3-chloro- 4-fluorothiophene, 3-bromo-4-fluorothiophene, 3-iodo-4-fluorothiophene, 3-bromo-4-chlorothiophene, 3-chloro-4-iodothiophene, 3-bromo-4-iodothiophene, etc. Can be mentioned.

  Among these, 3,4-difluorothiophene, 3,4-dichlorothiophene, 3,4-dibromothiophene, 3,4-diiodothiophene and the like are preferable in terms of price and handling, and 3,4-dibromothiophene is More preferably.

  One kind or two kinds of halogenated thiophenes can be used.

Examples of the alkali metal alkoxide include lithium methoxide, lithium ethoxide, lithium propoxide, lithium butoxide, sodium methoxide, sodium ethoxide, sodium propoxide, sodium butoxide, potassium methoxide, potassium ethoxide, and potassium propoxide. , Potassium bromide, lithium phenoxide, sodium phenoxide, potassium phenoxide and the like.
Among these, sodium methoxide, sodium ethoxide, sodium propoxide, and sodium butoxide are preferable in terms of handling, and sodium methoxide is more preferable.

  One or two alkali metal alkoxides can be used.

Examples of the alcohol solvent include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octynol, methoxymethanol, methoxyethanol, methoxypropanol, methoxybutanol, ethylene glycol, and propylene glycol.
Among these, methanol, ethanol, propanol, butanol and the like are preferable, and methanol is more preferable.

  One or two kinds of the alcohol solvent can be used.

  When the halogenated thiophene represented by the general formula (1) and the alkali metal alkoxide are mixed in an alcohol solvent, a catalyst can be used.

  Examples of the catalyst include copper halides such as copper fluoride, copper chloride, copper bromide, and copper iodide, and copper catalysts such as copper oxide.

  After completion of the reaction, for example, after adding water and filtering, the crude product is extracted with an organic solvent, and the resulting organic solvent layer is washed with water and dried.

  Examples of the organic solvent include aromatic solvents such as toluene and xylene, and aliphatic solvents such as pentane, hexane, and heptane.

  The organic solution of the crude product can be dried by, for example, an operation of heating and refluxing the organic solution of the crude product under reduced pressure to separate and remove azeotropic water.

  After the reaction, for example, after adding water or the like and filtering, the mixture is extracted with an organic solvent, and the obtained organic layer is washed with water and dried to give a crude containing at least the dialkoxythiophene derivative represented by the general formula (1). A product can be obtained. Main by-products include 2,4-dialkoxythiophene derivatives.

  Purity can also be improved by a distillation operation such as distillation under reduced pressure of the crude product containing at least the dialkoxythiophene derivative represented by the general formula (1).

  The method for purifying 3,4-dialkoxythiophene derivatives of the present invention can be used as a method for purifying dialkoxythiophene derivatives obtained by any production method, regardless of the dialkoxythiophene derivatives obtained by the above production methods. It is.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples. In the examples, “%” represents “% by weight”.

  Purity was measured by gas chromatography (GC). The apparatus used was an Agilent 6890N network GC (column: DB-35) manufactured by Agilent Technologies. Purity was calculated from the peak area ratio obtained using a detection device by FID.

Example 1
[Production of 3,4-dimethoxythiophene]
A 500 ml four-necked flask was charged with 63 g of sodium methoxide and 120 g of methanol (the concentration of sodium methoxide in the methanol solvent was 35.0% by weight based on the total amount of sodium methoxide before the reaction), and 70 ° C. under an argon atmosphere. And dissolved.
After adding 2.49 g of cuprous bromide, 45 g of 3,4-dibromothiophene is added dropwise. After the dropping, the reaction solution was heated to reflux at 88 ° C. for 5 hours. After the reaction, water was added, the mixture was filtered, extracted with toluene, concentrated under reduced pressure, and then distilled under reduced pressure to obtain a crude product of 3,4-dimethoxythiophene (2,4-dimethoxythiophene content 2.8%). 22.0 g of 3,4-dimethoxythiophene content 96.5%).

[Purification of 3,4-dimethoxythiophene]
The obtained crude product of 3,4-dimethoxythiophene (20.0 g) was diluted with 100 ml of hexane, and stirred with 100 ml of 13.7 mol% hydrochloric acid for 10 minutes (room temperature). The hexane layer was extracted and concentrated under reduced pressure to obtain 3,4-dimethoxythiophene. The purity of the obtained 3,4-dimethoxythiophene was 99.1%, and the recovered amount was 18.8 g (recovery rate: 94.0%). The resulting product did not contain 2,4-dimethoxythiophene.

(Example 2)
[Purification of 3,4-dimethoxythiophene]
20.0 g of a crude product of 3,4-dimethoxythiophene obtained in the same manner as in Example 1 was diluted with 100 ml of hexane and stirred with 100 ml of 27.4 mol% hydrochloric acid for 10 minutes (room temperature). The hexane layer was extracted and concentrated under reduced pressure to obtain 3,4-dimethoxythiophene. The purity of 3,4-dimethoxythiophene obtained was 99.2% and the recovered amount was 17.8 g (recovery rate: 89.0%). The resulting product did not contain 2,4-dimethoxythiophene.

(Example 3)
[Purification of 3,4-dimethoxythiophene]
A crude product of 3,4-dimethoxythiophene obtained in the same manner as in Example 1 (20.0 g) was diluted with 100 ml of hexane and stirred with 100 ml of 8.2 mol% hydrochloric acid for 10 minutes (room temperature). The hexane layer was extracted and concentrated under reduced pressure to obtain 3,4-dimethoxythiophene. The purity of 3,4-dimethoxythiophene obtained was 98.5% and the recovered amount was 19.3 g (recovery rate: 96.5%). The obtained product contained 0.6% of 2,4-dimethoxythiophene.

Example 4
[Purification of 3,4-dimethoxythiophene]
A crude product of 3,4-dimethoxythiophene obtained in the same manner as in Example 1 (20.0 g) was diluted with 100 ml of hexane and stirred with 100 ml of 40.0 mol% hydrochloric acid for 10 minutes (room temperature). The hexane layer was extracted and concentrated under reduced pressure to obtain 3,4-dimethoxythiophene. The purity of 3,4-dimethoxythiophene was 99.2%, and the recovered amount was 16.0 g (recovery rate: 80.0%). The resulting product did not contain 2,4-dimethoxythiophene.

(Example 5)
[Purification of 3,4-dimethoxythiophene]
20.0 g of a crude product of 3,4-dimethoxythiophene obtained in the same manner as in Example 1 was diluted with 100 ml of hexane and stirred with 100 ml of 17.8 mol% paratoluenesulfonic acid for 10 minutes (room temperature). The hexane layer was extracted and concentrated under reduced pressure to obtain 3,4-dimethoxythiophene. The purity of 3,4-dimethoxythiophene was 99.2% and the recovered amount was 17.9 g (recovery rate: 89.5%). The resulting product did not contain 2,4-dimethoxythiophene.

(Example 6)
[Purification of 3,4-dimethoxythiophene]
A crude product of 3,4-dimethoxythiophene obtained in the same manner as in Example 1 (20.0 g) was diluted with 100 ml of hexane, and stirred with 100 ml of 14.2 mol% sulfuric acid for 10 minutes (room temperature). The hexane layer was extracted and concentrated under reduced pressure to obtain 3,4-dimethoxythiophene. The purity of 3,4-dimethoxythiophene was 99.0% and the recovered amount was 18.2 g (recovery rate: 91.0%). The obtained product contained 0.3% of 2,4-dimethoxythiophene.

(Comparative Example 1)
[Purification of 3,4-dimethoxythiophene]
100 ml of water was added to 100 ml of hexane, and 20.0 g of a crude product of 3,4-dimethoxythiophene obtained in the same manner as in Example 1 was stirred (stirred) for 10 minutes. The hexane layer was extracted and concentrated under reduced pressure to obtain 3,4-dimethoxythiophene. The purity of the obtained 3,4-dimethoxythiophene was 96.5%, and the recovered amount was 19.7 g (recovery rate: 98.5%). The obtained product contained 2.8% of 2,4-dimethoxythiophene.

(Comparative Example 2)
[Purification of 3,4-dimethoxythiophene]
20.0 g of a crude product of 3,4-dimethoxythiophene obtained in the same manner as in Example 1 was distilled under reduced pressure to obtain 3,4-dimethoxythiophene. The purity of the obtained 3,4-dimethoxythiophene was 96.5%, and the recovered amount was 19.7 g (recovery rate: 97.2%). The obtained product contained 2.8% of 2,4-dimethoxythiophene.

  Table 1 shows the purity of 3,4-dimethoxythiophene, the content of 2,4-dimethoxythiophene obtained in Examples 1 to 6 and Comparative Examples 1 and 2, and the recovered amount.

  Compared with Comparative Examples 1 and 2, in Examples 1 to 6, the content of 2,4-dimethoxythiophene decreased, and high-purity 3,4-dimethoxythiophene was obtained. From this, it can be seen that high-purity dialkoxythiophene can be obtained by using the method for purifying a 3,4-dialkoxythiophene derivative according to the present invention.

  Thus, by using the method for purifying a 3,4-dialkoxythiophene derivative of the present invention, a high-purity 3,4-dialkoxythiophene derivative can be obtained, and the obtained 3,4-dialkoxythiophene is obtained. A conductive polymer using a derivative as a raw material has high transparency in addition to high conductivity, and therefore can be suitably used for a solid electrolytic capacitor, a conductivity imparting agent, and the like.

Claims (4)

A step (A) of mixing and contacting an organic layer containing a dialkoxythiophene derivative and an aqueous layer containing an acid, a step (B) of separating the organic layer and the aqueous layer and recovering the organic layer, and the recovered organic layer A method for purifying a 3,4-dialkoxythiophene derivative, which includes a step (C) of removing a solvent and removing a 3,4-dialkoxythiophene derivative represented by the following general formula (1).

(R ₁ and R _{2 in} Formula (1) represent a linear or branched alkyl group or aryl group having 1 to 20 carbon atoms that may be the same or different from each other.) The dialkoxythiophene derivative is a dialkoxy derivative obtained by reacting a halogenated thiophene represented by the general formula (2) with an alkali metal alkoxide in an alcohol solvent. A method for purifying the described 3,4-dialkoxythiophene derivative.

(X in Formula (2) represents either a fluorine atom, a chlorine atom, a bromine atom or an iodine atom which may be independent or different from each other.)   The method for purifying a 3,4-dialkoxythiophene derivative according to claim 1 or 2, wherein the acid is hydrochloric acid, paratoluenesulfonic acid, or sulfuric acid.   The 3,4-dialkoxy according to any one of claims 1 to 3, wherein the aqueous layer has an acid concentration of 0.1 to 30 mol% with respect to the dialkoxythiophene derivative. Purification method for thiophene derivatives.