JP2009298722A - Method for producing dialkoxythiophene and alkylenedioxythiophene - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide methods for safely, efficiently and industrially advantageously producing a dialkoxythiophene and an alkylenedioxythiophene. <P>SOLUTION: The method for producing the 3,4-dialkoxythiophene comprises decarboxylating thiophene-2,5-dicarboxylic acid represented by general formula (1) (wherein R<SP>1</SP>and R<SP>2</SP>are each independently a 1-15C monovalent hydrocarbon group) in the presence of an alkylpyridine and a copper compound. The method can be applied also to the production of the alkylenedioxythiophene. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing high-purity dialkoxythiophene and alkylenedioxythiophene.

  Dialkoxythiophene, alkylenedioxythiophene and their derivatives are known to be very useful materials as monomers for the production of conductive polymers.

  Conventionally, various methods are known as methods for producing dialkoxythiophene and alkylenedioxythiophene by decarboxylation of dialkoxythiophene-2,5-dicarboxylic acid and alkylenedioxythiophene-2,5-dicarboxylic acid. It has been. For example, (1) a method of performing decarboxylation using a high-boiling solvent in the presence of a copper catalyst (see Patent Document 1), (2) using a copper catalyst in a water-soluble high-boiling solvent in an oxygen atmosphere. Examples include decarboxylation (see Patent Document 2) and (3) decarboxylation in quinoline in the presence of a copper catalyst (see Non-Patent Document 1).

  However, the method (1) requires precision distillation in order to obtain high-purity dialkoxythiophene and alkylenedioxythiophene. Moreover, since sulfolane (boiling point 285 ° C.) or polyethylene glycol 300 having a higher boiling point than dialkoxythiophene and alkylenedioxythiophene is used as a reaction solvent, when these are recovered and reused, sulfolane has a high boiling point. For this reason, a considerable amount of heat energy is required, and polyethylene glycol 300 has a limit in reuse because it is difficult to recover by distillation. In the method (2), oxygen or air is passed through the reaction solution at a high temperature, so there is a risk of ignition. In the method (3), a highly toxic quinoline is used as a reaction solvent, and the yield is as low as 54%. Furthermore, since the reaction temperature is 200 ° C., much heat energy is required.

Therefore, the production methods of dialkoxythiophene and alkylenedioxythiophene of the above (1) to (3) are not industrially preferable.
JP 2001-288182 A US Pat. No. 7,202,369 Synthetic Communications, Vol. 26, 1996, p. 2205-2212

  An object of the present invention is to provide a method for producing dialkoxythiophene and alkylenedioxythiophene safely and efficiently and advantageously industrially.

  As a result of intensive studies on the above problems, the present inventors have found that dialkoxythiophene and alkylenedioxythiophene can be efficiently produced, and have completed the present invention.

That is, the present invention provides a method for producing dialkoxythiophene and alkylenedioxythiophene as shown below.
Item 1. General formula (1);

(Wherein R ¹ and R ² each independently represents a monovalent hydrocarbon group having 1 to 15 carbon atoms), thiophene-2,5-dicarboxylic acid represented by alkylpyridine and copper compound General formula (2), characterized by decarboxylation in the presence of

(Wherein R ¹ and R ² are the same as defined above).
Item 2. Item 2. The method according to Item 1, wherein the alkylpyridine has a boiling point of 120 to 180 ° C.
Item 3. Alkylpyridines are 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,6-dimethylpyridine, 2,4-dimethylpyridine and 2, Item 3. The method according to Item 1 or 2, which is at least one selected from the group consisting of 4,6-trimethylpyridine.
Item 4. Item 4. The method according to any one of Items 1 to 3, wherein the copper compound is at least one selected from the group consisting of copper, basic copper carbonate, copper oxide (I), and copper oxide (II).
Item 5. Item 5. The method according to any one of Items 1 to 4, wherein the decarboxylation reaction temperature is 100 to 180 ° C.
Item 6. General formula (3);

(Wherein A represents a divalent hydrocarbon group having 1 to 15 carbon atoms). Decarboxylation of thiophene-2,5-dicarboxylic acid represented by alkylpyridine and a copper compound. A general formula (4) characterized by:

(Wherein A is the same as defined above), and a method for producing alkylenedioxythiophene.
Item 7. Item 7. The method according to Item 6, wherein the alkylpyridine has a boiling point of 120 to 180 ° C.
Item 8. Alkylpyridines are 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,6-dimethylpyridine, 2,4-dimethylpyridine and 2, Item 8. The method according to Item 6 or 7, which is at least one selected from the group consisting of 4,6-trimethylpyridine.
Item 9. Item 9. The method according to any one of Items 6 to 8, wherein the copper compound is at least one selected from the group consisting of copper, basic copper carbonate, copper (I) oxide, and copper (II) oxide.
Item 10. Item 10. The method according to any one of Items 6 to 9, wherein the decarboxylation reaction temperature is 100 to 180 ° C.

  Hereinafter, the present invention will be described in detail.

[Production of dialkoxythiophene]
The dialkoxythiophene represented by the general formula (2) is obtained by decarboxylating the thiophene-2,5-dicarboxylic acid represented by the general formula (1) in the presence of an alkylpyridine and a copper compound. Manufactured.

The monovalent hydrocarbon group having 1 to 15 carbon atoms represented by R ¹ and R ² in the general formula (1) may be linear, branched or cyclic, and may be a methyl group, an ethyl group, n -Propyl group, isopropyl group, cyclopropyl group, n-butyl group, 2-methylpropyl group, t-butyl group, cyclobutyl group, n-pentyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, Cyclopentyl group, 1-methylcyclobutyl group, 2-methylcyclobutyl group, 3-methylcyclobutyl group, n-hexyl group, cyclohexyl group, phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-phenyl Methyl group, 2,3-dimethylphenyl group, 2,4-dimethylphenyl group, 2,5-dimethylphenyl group, 2,6-dimethylphenyl group, 3,4- Dimethylphenyl group, 3,5-dimethylphenyl group, 3,6-dimethylphenyl group, 2-methyl-3-ethylphenyl group, 2-methyl-4-ethylphenyl group, 2-methyl-5-ethylphenyl group, Examples include 2-methyl-6-ethylphenyl group, benzyl group, 2-methylbenzyl group, 3-methylbenzyl group, 4-methylbenzyl group and the like.

  The alkyl pyridine is not particularly limited, but 2-methylpyridine (boiling point 129 ° C), 3-methylpyridine (boiling point 144 ° C), 4-methylpyridine (boiling point 143 ° C), 2,3-dimethylpyridine (boiling point 163 ° C). ), 2,4-dimethylpyridine (boiling point 157-158 ° C), 2,5-dimethylpyridine (boiling point 152-155 ° C), 2,6-dimethylpyridine (boiling point 139-141 ° C), 3,4-dimethylpyridine (Boiling point 164-165 ° C), 3,5-dimethylpyridine (boiling point 168-171 ° C), 2,4,6-trimethylpyridine (boiling point 175-178 ° C), 2,4,5-trimethylpyridine (boiling point 165- 168 ° C), 2,3,6-trimethylpyridine (boiling point 176-178 ° C), 2-ethylpyridine (boiling point 149 ° C), 3-ethylpyridine ( Point 162-165 ° C), 4-ethylpyridine (boiling point 170 ° C), 2,6-diethylpyridine (boiling point 174-175 ° C), 2-ethyl-6-methylpyridine (boiling point 160-162 ° C), 2-ethyl -4-methylpyridine (bp 173-175 ° C), 4-ethyl-2-methylpyridine (bp 179-180 ° C), 5-ethyl-2-methylpyridine (bp 174-176 ° C), 2-propylpyridine ( Boiling point 170 ° C), 2-isopropylpyridine (boiling point 159 ° C), 3-isopropylpyridine (boiling point 177-178 ° C), 4-isopropylpyridine (boiling point 173 ° C), 2-t-butylpyridine (boiling point 169 ° C), etc. Can be mentioned. Preferably, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,6-dimethylpyridine, 2,4-dimethylpyridine, 2,4 , 6-trimethylpyridine, more preferably 3-methylpyridine or 4-methylpyridine. The amount of alkylpyridine used is preferably 0.1 to 20 ml, more preferably 0.5 to 10 ml, based on 1 g of thiophene-2,5-dicarboxylic acid.

  Copper compounds include copper powder, copper oxide (I), copper oxide (II), copper chromate, basic copper carbonate (II), copper sulfate (II), copper hydroxide (II), copper chloride (I) , Copper (II) chloride, copper (I) bromide, copper (II) bromide, copper (I) iodide, copper (II) iodide, copper (I) acetate, copper (II) acetate, acetylacetonate Examples include copper (II) and the like, and those in which a hydrate exists may be in a hydrated state. Preferred are copper, copper oxide (I), copper oxide (II), and basic copper carbonate (II), and more preferred are copper oxide (I) and copper oxide (II). As a usage-amount of a copper compound, it is preferable that it is 0.001-2g with respect to 1g of thiophene-2,5-dicarboxylic acid, and it is more preferable that it is 0.01-1g.

  The thiophene-2,5-dicarboxylic acid represented by the general formula (1) used for the reaction may be a hydrate or wet with water. The reaction temperature for decarboxylation is preferably 100 to 180 ° C, more preferably 120 to 180 ° C. The reaction time may be carried out until thiophene-2,5-dicarboxylic acid disappears, but it is usually sufficient to carry out for 1 to 24 hours.

  After the reaction, high-purity dialkoxythiophene is obtained by purifying the crude product obtained by a conventional method such as acid addition, solvent extraction, washing, and dehumidification using distillation or column chromatography. It is also possible to recycle alkylpyridine. Examples of the recycling method include a method of neutralizing a separated aqueous layer (acidic) generated by solvent extraction after reaction and then adding an acid after the reaction, followed by extraction with an organic solvent, and distilling the organic layer.

  Alkylpyridine acid salts (for example, hydrochloride) are more soluble in water than quinoline acid salts (for example, hydrochloride), so acid addition (acid washing) and solvent extraction are performed in the post-treatment after the reaction. Thus, the alkylpyridine can be easily removed as an acid salt (dissolved in the aqueous layer) and can be easily separated from the reaction product. In addition, since the boiling point of alkylpyridine is lower than that of quinoline (237 ° C.), considering the recycling of the solvent, it is easy to purify by distillation or the like, which is advantageous in terms of cost.

[Production of alkylenedioxythiophene]
The alkylenedioxythiophene represented by the general formula (4) is obtained by decarboxylating the thiophene-2,5-dicarboxylic acid represented by the general formula (3) in the presence of an alkylpyridine and a copper compound. Manufactured by.

  In the general formula (3), the divalent hydrocarbon group having 1 to 15 carbon atoms represented by A may be linear, branched or cyclic, and may be a methylene group, ethylene group, propylene group or butylene group. Pentylene group, hexylene group, 1-methylethylene group, 1-ethylethylene group, 1-hexylethylene group, 1-octylethylene group, 1-decylethylene group, 1-tetradecylethylene group, 1-phenylethylene group 1,2-dimethylethylene group, 1-methylpropylene group, 2-methylpropylene group, 1,2-dimethylpropylene group, 1,3-dimethylpropylene group, 1-ethylethylene group, cyclobutylene group, cyclohexylene Groups and the like.

  Moreover, the thiophene-2,5-dicarboxylic acid represented by the general formula (3) used in the reaction may be a hydrate or wet with water.

  The types and amounts of alkylpyridines used, the types and amounts of copper compounds used, decarboxylation reaction temperature, reaction time, post-reaction post-treatment, purification, alkylpyridine recycling, etc. This is the same as described in [Manufacturing of].

  According to the present invention, dialkoxythiophene and alkylenedioxythiophene can be produced safely and efficiently industrially advantageously.

  The following examples further illustrate the present invention, but the present invention is not limited to these examples.

Example 1 (Production of 3,4-ethylenedioxythiophene using 4-methylpyridine)
In a 100 ml flask, 15 g (0.06 mol) of 3,4-ethylenedioxythiophene-2,5-dicarboxylic acid monohydrate, 349.3 mg (4.39 mmol) of copper (II) oxide, and 4-methyl 56 ml of pyridine (boiling point 143 ° C.) was added and reacted at 130 ° C. for 3 hours. After completion of the reaction, the mixture was cooled in an ice bath, 150 ml of 18% hydrochloric acid was added, extracted twice with 150 ml of toluene, and the organic layer was washed twice with 150 ml of 18% hydrochloric acid and once with 150 ml of 8% aqueous sodium hydroxide solution. Dry with magnesium. The organic layer was concentrated under reduced pressure, and the resulting crude product was subjected to simple distillation to obtain colorless and clear 3,4-ethylenedioxythiophene in a yield of 72% (content: 99.9% or more, HPLC analysis). .
¹ H-NMR (CDCl ₃ , 400 MHz): 6.31 (s, 2H, thiophene ring), 4.18 (s, 4H, —CH ₂ CH ₂ —).

Examples 2-5
Reaction was carried out in the same manner as in Example 1 using the alkylpyridines shown in Table 1 below, and the results of Examples 2 to 5 were obtained.

Example 6 (Recovery of 4-methylpyridine)
The liquid separation aqueous layer produced by the toluene extraction of Example 1 was neutralized by adding a 24% aqueous sodium hydroxide solution, and then extracted twice with 50 ml of diethyl ether. The obtained organic layer was concentrated and then distilled to recover 50 ml of 4-methylpyridine.

Example 7 (Production of 3,4-ethylenedioxythiophene using recovered 4-methylpyridine)
In a 100 ml flask, 10 g (0.04 mol) of 3,4-ethylenedioxythiophene-2,5-dicarboxylic acid monohydrate, 232.3 mg (2.91 mmol) of copper (II) oxide, and Example 6 4-methylpyridine (37.5 ml) recovered in (3) was added and reacted at 130 ° C. for 3 hours. After completion of the reaction, the reaction mixture was cooled in an ice bath, 100 ml of 18% hydrochloric acid was added, extracted twice with 100 ml of toluene, and the organic layer was washed twice with 100 ml of 18% hydrochloric acid and once with 100 ml of 8% aqueous sodium hydroxide solution. Dry with magnesium. The organic layer was concentrated under reduced pressure, and the resulting crude product was subjected to simple distillation to obtain colorless and clear 3,4-ethylenedioxythiophene in a yield of 70.4% (content: 99.9% or more, HPLC analysis). Obtained.

Example 8 (Production of 2-methyl-2,3-dihydro-thieno [3,4-b] [1,4] dioxin)
In a 100 ml flask, 2-methyl-2,3-dihydro-thieno [3,4-b] [1,4] dioxin-5,7-dicarboxylic acid 5 g (0.02 mol), copper (II) oxide 124. 1 mg (1.56 mmol) and 19 ml of 4-methylpyridine were added and reacted at 130 ° C. for 3 hours. After completion of the reaction, the reaction mixture was cooled in an ice bath, 50 ml of 18% hydrochloric acid was added, extracted twice with 50 ml of toluene, and the organic layer was washed twice with 50 ml of 18% hydrochloric acid and once with 50 ml of 8% aqueous sodium hydroxide solution. Dry with magnesium. The organic layer was concentrated under reduced pressure, and the resulting crude product was subjected to simple distillation to yield colorless and clear 2-methyl-2,3-dihydro-thieno [3,4-b] [1,4] dioxin. 28% (content 99.9% or more, HPLC analysis).
¹ H-NMR (CDCl ₃ , 400 MHz): 6.31 (s, 2H, thiophene ring), 4.30 (t, 1H, —CH—), 4.25 (dd, 2H, —CH ₂ —), _{1.38 (d, 3H, -CH 3} ).

Example 9 (Production of 3,4-dimethoxythiophene)
In a 10 ml flask, 10 g (0.043 mol) of 3,4-dimethoxythiophene-2,5-dicarboxylic acid, 239.8 mg (3.014 mmol) of copper (II) oxide, and 4-methylpyridine (boiling point 143 ° C.) 37.5 ml was added and reacted at 130 ° C. for 3 hours. After completion of the reaction, the reaction mixture was cooled in an ice bath, 100 ml of 18% hydrochloric acid was added, extracted twice with 100 ml of toluene, and the organic layer was washed twice with 100 ml of 18% hydrochloric acid and once with 100 ml of 8% aqueous sodium hydroxide solution. Dry with magnesium. The organic layer was concentrated under reduced pressure, and the resulting crude product was subjected to simple distillation to obtain 3,4-dimethoxythiophene in a yield of 51% (content: 99.9% or more, HPLC analysis).
¹ H-NMR (CDCl ₃ , 400 MHz): 6.36 (s, 2H, thiophene ring), 3.78 (s, 6H, —CH ₃ ).

Claims (10)

General formula (1);

(Wherein R ¹ and R ² each independently represents a monovalent hydrocarbon group having 1 to 15 carbon atoms), thiophene-2,5-dicarboxylic acid represented by alkylpyridine and copper compound General formula (2), characterized by decarboxylation in the presence of

(Wherein R ¹ and R ² are the same as defined above).   The process according to claim 1, wherein the alkylpyridine has a boiling point of 120 to 180 ° C.   Alkylpyridines are 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,6-dimethylpyridine, 2,4-dimethylpyridine and 2, The method according to claim 1 or 2, which is at least one selected from the group consisting of 4,6-trimethylpyridine.   The method according to any one of claims 1 to 3, wherein the copper compound is at least one selected from the group consisting of copper, basic copper carbonate, copper oxide (I) and copper oxide (II).   The method according to any one of claims 1 to 4, wherein the reaction temperature for decarboxylation is 100 to 180 ° C. General formula (3);

(Wherein A represents a divalent hydrocarbon group having 1 to 15 carbon atoms). Decarboxylation of thiophene-2,5-dicarboxylic acid represented by alkylpyridine and a copper compound. A general formula (4) characterized by:

(Wherein A is the same as defined above), and a method for producing alkylenedioxythiophene.   The process according to claim 6, wherein the alkylpyridine has a boiling point of 120 to 180 ° C.   Alkylpyridines are 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,6-dimethylpyridine, 2,4-dimethylpyridine and 2, The method according to claim 6 or 7, which is at least one selected from the group consisting of 4,6-trimethylpyridine.   The method according to any one of claims 6 to 8, wherein the copper compound is at least one selected from the group consisting of copper, basic copper carbonate, copper (I) oxide and copper (II) oxide.   The reaction temperature of decarboxylation is 100-180 degreeC, The method in any one of Claims 6-9.