JP4641407B2 - Method for purifying 4,5-dimercapto-1,3-dithiolane - Google Patents

Description

  The present invention relates to a method for purifying a thiol compound, and particularly relates to a method for purifying a thiol compound that has high purity and reduced coloration.

  In recent years, plastics are used for various optical applications such as lenses because they are lighter than glass and are difficult to break and can be easily dyed. As optical plastic materials, poly (diethylene glycol bisallyl carbonate) (CR-39) and poly (methyl methacrylate) are generally used. However, since these plastics have a refractive index of 1.50 or less, when they are used, for example, as a lens material, the lens becomes thicker as the power increases, and the superiority of the plastic, which is advantageous in terms of light weight, is lost. In particular, a strong concave lens is not preferable because the periphery of the lens becomes thick and birefringence and chromatic aberration occur. In addition, thick lenses in eyeglass applications tend to degrade aesthetics. In order to obtain a thin lens, it is effective to increase the refractive index of the material. In general, in glass and plastic, the Abbe number decreases as the refractive index increases, and as a result, their chromatic aberration increases. Therefore, a plastic material having a high refractive index and Abbe number is desired.

Examples of plastic materials having such performance include (1) polyurethane obtained by polyaddition of a polyol having bromine in the molecule and polyisocyanate (Patent Document 1), and (2) polyaddition of polythiol and polyisocyanate. Has been proposed (Patent Document 2, Patent Document 3). In particular, as polythiol used as a raw material for the polythiourethane (2), a branched chain having an increased sulfur atom content (Patent Documents 4 and 3) and a polythiol having a dithian structure introduced to increase the sulfur atom ( Patent Documents 5 and 6) have been proposed.
However, although the polyurethane of the above (1) has a slightly improved refractive index, it has disadvantages such as a low Abbe number and inferior light resistance, a high specific gravity, and a loss of lightness. . In addition, among the polythiourethanes of (2), the polythiourethane obtained by using a polythiol having a high sulfur content as a polythiol of the raw material has a refractive index raised to, for example, about 1.60 to 1.68, The Abbe number is lower than that of optical inorganic glass having a refractive index, and the Abbe number has to be increased.

As a polythiourethane that satisfies the above requirements, a high refractive index lens using a high sulfur content thiol such as 4,5-dimercapto-1,3-dithiolene, 1,2,2-trimercaptoethane, etc. 8) and 4,5-bisepithiopropyldithia-1,3-dithiolane, 4,5-bisthiyanyldithia-1,3-dithiolane, etc., using the above thiol compound as a raw material, high sulfur content disulfide compounds Attention has been focused on a high refractive index lens (Patent Document 9) using the above lens. These thiols are obtained via esters and thioesters using alcohols and aldehydes as starting materials. Since the structure of thioester is widely used for the structure of a protecting group for a thiol group, it is useful in the synthesis reaction. However, the thiol compounds are low in yield and highly colored by the methods described in the above documents, and it is difficult to obtain high-yield and uncolored raw materials. It is very difficult. Therefore, establishment of a thiol compound purification method that easily removes impurities and colored substances is desired.
As a conventional method for producing and purifying thiol compounds, for example, 4,5-dithioacetoxy-1,3-dithiolane is reacted at room temperature to 70 ° C. for 5 to 20 hours using concentrated sulfuric acid in a mixed solvent of ethanol and chloroform. As a result, the desired 4,5-dimercapto-1,3-dithiolane oil can be obtained. However, this synthesis method has problems of significant coloring and low purity / yield, and further, a distillation purification method under high vacuum / high temperature conditions has been used to purify the product. However, there are problems such as decomposition of products at high temperatures, and there are significant problems in production from the viewpoint of equipment and cost.

JP 58-164615 Japanese Patent Publication No. 4-58489 Japanese Patent Laid-Open No. 5-148340 JP-A-2-270859 Japanese Patent Publication No. 6-5323 JP 7-118390 A Japanese Patent Application No. 2003-192605 Japanese Patent Application No. 2003-192604 Japanese Patent Application No. 2003-195673

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for purifying a thiol compound that has high purity and reduced coloring.

  As a result of intensive studies to achieve the above object, the present inventors have added a basic solution to produce a thiol salt when purifying a thiol compound, and then crystallized by adding a purification solvent. The inventors have found that the above object can be achieved and have completed the present invention.

That is, the present invention
(1) When purifying a thiol compound having one or more geminal-dithiol structures represented by the general formula (1), a basic solution is added to produce a thiol salt, and a purification solvent is added to crystallize the thiol compound. A method for purifying thiol compounds to remove impurities and / or colored substances,

(2) When purifying a thiol compound having one or more pairs of thiol structures represented by the general formula (2), a basic solution is added to form a thiol salt, and a purification solvent is added to crystallize impurities and impurities. A method for purifying thiol compounds to remove colored substances,

（式中、Ｒは、炭素数１〜３のアルカン残基、炭素数４〜７のシクロアルカン残基、ヘテロ原子が酸素、窒素もしくは硫黄原子である炭素数３〜７のヘテロ環残基又は炭素数６〜１０の芳香族環残基を示し、各残基は置換基を有していてもよい。） (3) When purifying the thiol compound represented by the general formula (3), a thiol salt is formed by adding a basic solution and crystallized by adding a purifying solvent to remove impurities and / or colored substances. Compound purification method,

(In the formula, R is an alkane residue having 1 to 3 carbon atoms, a cycloalkane residue having 4 to 7 carbon atoms, a heterocyclic residue having 3 to 7 carbon atoms in which the hetero atom is an oxygen, nitrogen or sulfur atom, or An aromatic ring residue having 6 to 10 carbon atoms is shown, and each residue may have a substituent.)

を提供するものである。 (4) When purifying the thiol compound represented by the general formula (4), a thiol salt is formed by adding a basic solution and crystallized by adding a purifying solvent to remove impurities and / or colored substances. Compound purification method

Is to provide.

  The method for purifying a thiol compound of the present invention is suitable as a method for purifying a thiol compound with high purity and reduced coloring.

In the general formula (3), examples of the alkane residue of R include a methane residue, an ethane residue, an n-propane residue, an i-propane residue, and the like. preferable.
Examples of the R cycloalkane residue include a cyclobutane residue, a cyclopentane residue, and a cyclohexane residue, and a cyclopentane residue and a cyclohexane residue are preferable.
Examples of the heterocyclic group of R include 1,3-dithiolane residue, 1,3-dithiane residue, 1,4-dithiane residue, etc., and 1,3-dithiolane residue, 1, 4-dithiane residues are preferred.
Examples of the aromatic ring residue of R include a benzene ring residue and a naphthalene ring residue, and a benzene ring residue is preferable.
In addition, the substituents of these residues include halogen atoms such as bromine, chlorine and iodine, alkyl groups such as methyl group, ethyl group, n-propyl group and i-propyl group, phenyl group and naphthyl group. An aromatic group etc. are mentioned.

  Examples of the compound having one or more geminal-dithiol structures represented by the general formula (1) of the present invention include dimercaptomethane, 1,1-dimercaptoethane, 1,1-dimercaptopropane, 2,2 -Dimercaptopropane, 1,1-dimercaptobutane, 2,2-dimercaptobutane, 1,1-dimercapto-2-methylpropane, 1,1,2,2-tetramercaptoethane, 1,1,2, 2-tetramercaptopropane, 1,1,3,3-tetramercaptopropane, 1,1,3,3-tetramercapto-2-thiapropane, 1,1,2,2-tetramercaptobutane, 1,1,4 , 4-tetramercaptobutane, 1,1,5,5-tetramercaptopentane, 1,1,5,5-tetramercapto-3-thiapentane, 1,1,6,6- Examples include tetramercaptohexane, 1,1-dimercaptocyclopentane, 1,1-dimercaptocyclohexane, 1,1,4,4-tetramercaptocyclohexane, and the like.

  Examples of the compound having at least one thiol structure represented by the general formula (2) include 1-mercapto-2-thiapropane, 1-mercapto-2-thiabutane, 2-mercapto-3-thiabutane, and 1-mercapto. -2-thiapentane, 2-mercaptol-3-thiapentane, 1-mercapto-2-cyclothiapentane, 1-mercapto-2-cyclothiahexane, 1-mercapto-2,6-cyclodithiahexane and the like.

  Examples of the thiol compound represented by the general formula (3) include 4,5-dimercapto-1,3-dithiolane, 2,3-dimercapto-1,4-dithiane, 3,4-dimercapto-bicyclo [4]. .3.0] -2,5,7,9-tetrathianonane, 3,4-dimercapto-bicyclo [4.4.0] -2,5,7,10-tetrathiadecane, 2,3-dimercapto -1,4-benzodithian and the like, and these compounds may have cis- and trans-isomers with respect to the mercapto group.

The basic solution used in the present invention is preferably a solution in which a basic substance is dissolved in water or an organic solvent.
Examples of the basic substance include hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, and barium hydroxide, amines such as ammonia, diethylamine, and triethylamine, and the like. Potassium oxide and the like are preferable. The base concentration used is preferably 0.5 to 8 mol and 0.9 to 2 mol with respect to 1 mol equivalent of thiol groups present in the reaction product. The basic substance is preferably dropped after being dissolved in an organic solvent such as water or ethanol, and the amount of the solvent is usually preferably 100 to 10,000 ml and 200 to 1000 ml.

  The purification solvent used in the present invention is preferably a water-soluble solvent miscible with water, more preferably a water-soluble organic solvent, such as methanol, ethanol, n-propyl alcohol, 2-propanol, n-butanol, Examples include alcohols such as 2-butanol, ethers such as tetrahydrofuran, ketones such as acetone, butanone and 2-butanone, acetonitrile and the like, and methanol, ethanol and the like are preferable. The purification solvent may be at least one selected from the above solvents, and may be a mixed solvent such as ethanol / acetone.

  After completion of purification, the thiol compound is preferably neutralized with an acidic aqueous solution such as hydrochloric acid or sulfuric acid. The concentration of the acidic aqueous solution is usually 1 to 30%, preferably 5 to 20%, and it is preferably dropped while cooling so that the pH is usually 5 to 8, and preferably 5.5 to 7.

The purification method of the present invention is performed, for example, as follows.
That is, first, a basic solution is dropped and reacted while cooling the crude thiol compound, and then a purified solvent is added to form a precipitate. After collecting the precipitate, it is dissolved in water and then neutralized with an acidic aqueous solution while cooling to obtain a purified thiol compound.
More specifically, it may be performed as follows. For example, as a thiol compound, 4,5-dimercapto-1,3-dithiolane as a basic solution with respect to 1 mol, for example, usually 1 to 40%, preferably 10 to 30% potassium hydroxide aqueous solution 50 to 2000 Dissolved in milliliters, preferably 100-600 milliliters, usually cooled to -20-20 ° C, preferably -10-0 ° C, and an organic solvent, for example 50-2000 milliliters of ethanol, preferably 100-600 milliliters, is added, Dipotassium-1,3-dithiolane-4,5-dithiolate is precipitated. The precipitate is recovered, 50 to 2000 ml of water, preferably 100 to 600 ml, is added to dissolve the salt, and then ethanol is added. After repeating this operation 1 to 5 times, the precipitate of dipotassium-1,3-dithiolane-4,5-dithiolate is added with an acidic aqueous solution, for example, usually 1 to 50%, preferably 10 to 30% aqueous sulfuric acid solution, and pH Is usually 5-8, preferably 5.5-7. After completion of neutralization, the organic layer is recovered, washed with water sufficiently, and dried to obtain 4,5-dimercapto-1,3-dithiolane having no color.

  The thiol compound obtained by the purification method of the present invention is preferably used as an intermediate or a raw material for a monomer for synthesizing a polymer for a high refractive index lens used for a lens. What is necessary is just to synthesize | combine according to the method. Specifically, for example, when synthesizing 4,5-bisepithiopropyldithia-1,3-dithiolane, 4,5-dimercapto-1,3-dithiolane and S-substituted sulfenyl-O- The mixture with methoxythiocarbonate is stirred at room temperature for 12 hours, and the resulting carbonyl sulfide and methanol are removed under reduced pressure to obtain the desired product.

The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, the coloring condition and purity of the thiol compounds obtained in Synthesis Examples, Examples, and Comparative Examples were measured according to the following methods.
(1) Coloring condition The coloring condition of the product was observed under fluorescent lamp irradiation.
(2) Measurement of purity Purity was determined using Shimadzu GC-14BPF gas chromatography. The gas flow rate was 51 ml / min, the temperature range was 150 to 300 ° C., and the heating rate was 5 ° C./min.

Synthesis example (synthesis of 4,5-dimercapto-1,3-dithiolane)
(1) Synthesis of 4,5-dihydroxyl-1,3-dithiolane Methanedithiol (642 g) was added dropwise to a 40% aqueous solution of glyoxal (1161.6 g) over 1.5 hours while cooling in a water bath, followed by stirring reaction for 6 hours. . After the reaction was completed, water was removed to obtain 4,5-dihydroxyl-1,3-dithiolane as white crystals (1105.7 g). The obtained 4,5-dihydroxyl-1,3-dithiolane was used in the subsequent step without purification.
(2) Synthesis of 4,5-diacetoxyl-1,3-dithiolane Ice bath in 4,5-dihydroxyl-1,3-dithiolane (260.2 g) obtained in step (1) and pyridine (82 g) Acetic anhydride (403.0 g) was added dropwise over 3 hours while cooling at room temperature. The reaction was continued for another 2 hours with stirring. After most of pyridine and acetic acid were removed by distillation under reduced pressure at room temperature, ice and dichloromethane (200 ml) were added and the phases were separated. The pyridine was completely removed by washing with 5% sulfuric acid aqueous solution. Then, the pure dichloromethane solution was washed several times, and magnesium sulfate was added and dried. Dichloromethane was removed by distillation to obtain a white powder (405 g) of 4,5-diacetoxyl-1,3-dithiolane. The obtained white powder of 4,5-diacetoxyl-1,3-dithiolane was used in the subsequent step without purification.
(3) Synthesis of 4,5-dithioacetoxy-1,3-dithiolane
Ethyl acetate (492 ml) was added to a white powder (492 g) of 4,5-diacetoxy-1,3-dithiolane (492 g) and dissolved, and then thioacetic acid (354 g) was added dropwise. Ride ether solution (25 ml) was added slowly. After reacting at ice temperature for 1 hour, the mixture was further stirred at room temperature until the reaction was completed. 200 ml of dichloromethane was added to the reaction solution, washed with 20% potassium carbonate solution, dried, and then the solvent was removed to obtain a compound containing 4,5-dithioacetoxy-1,3-dithiolane (533 g, Yield 94.6%).
(4) Synthesis of 4,5-dimercapto-1,3-dithiolane
4,5-Dithioacetoxy-1,3-dithiolane (354 g, 1.39 mol) was added to a mixed solution of ethanol (400 ml) and diethyl ether (400 ml) and cooled to -5 ° C. A sodium hydroxide aqueous solution (5.85 mol, 700 ml) was added dropwise so as not to exceed 0 ° C. After completion of dropping, the mixture was stirred for 2 hours. While maintaining the obtained reaction solution at 0 ° C. or lower, a 20% aqueous sulfuric acid solution (1400 ml) was added and stirred for 30 minutes. After extraction with dichloromethane, washing with water, drying with magnesium sulfate, removing the solvent, and distillation at 78-80 ° C./0.67 Pa, 4,5-dimercapto-1,3-dithiolane (160.5 g, yield) was obtained. Rate 67.7%, purity 99.1%). The color was reddish brown.

Purification Example 1 (Purification of 4,5-dimercapto-1,3-dithiolane)
A 26.5% aqueous potassium hydroxide solution (204 g) was added dropwise to 82 g (purity 99.1%) of 4,5-dimercapto-1,3-dithiolane obtained in the above synthesis example over 40 minutes so as not to exceed 0 ° C. After completion of the dropwise addition, the mixture was aged for 30 minutes, ethanol (450 ml) was added so as not to exceed 2 ° C., and the mixture was kept at −5 ° C. for 1 hour. After collecting the precipitate, washing with ethanol (100 ml) was repeated twice while maintaining 0 ° C. or lower. Water (150 ml) was added while maintaining 0 ° C. to dissolve the precipitate, and then 600 ml of ethanol was added while maintaining the temperature at 0 ° C. or lower, followed by stirring for 1 hour. After collecting the precipitate, washing with ethanol (100 ml) was repeated three times while maintaining the temperature at 0 ° C. or lower. Water (150 ml) was added while maintaining 0 ° C. to dissolve the precipitate, and 160 g of 18% hydrochloric acid aqueous solution was added to maintain the pH at 6 while maintaining the temperature at 2 ° C. or lower. The organic layer was recovered, dried over anhydrous magnesium sulfate, and removed to obtain a mixture of cis- and trans-isomers of the desired 4,5-dimercapto-1,3-dithiolane (67.0 g, yield). 81.7%). The purity after purification was 99.6%, and it was colorless and transparent.

Comparative Example 1
Distillation was repeated twice at 85 to 90 ° C./0.67 Pa for 75 g (purity 99.1%) of 4,5-dimercapto-1,3-dithiolane obtained in the above synthesis example. A single distillation took 6 hours. A mixture of cis- and trans-isomers of the desired 4,5-dimercapto-1,3-dithiolane (60 g, yield 80.0%, purity 99.6%) was obtained, which was a yellow oily substance and was colorless and transparent It wasn't.

According to the purification method of the present invention, when purifying a thiol compound, a thiol salt is formed by adding a basic solution, and crystallized by adding a purification solvent, thereby achieving high purity and reduced coloring. A compound is obtained.

Claims (5)

In the purification method of 4,5-dimercapto-1,3-dithiolane, a basic solution is added to 4,5-dimercapto-1,3-dithiolane to form a thiol salt, and a purification solvent is added to crystallize the impurities. And / or a method for purifying 4,5-dimercapto-1,3-dithiolane, which comprises removing a colored substance. The method for purifying 4,5-dimercapto-1,3-dithiolane according to claim 1, wherein the basic solution is a solution obtained by dissolving a basic substance in water or an organic solvent. 4. The basic substance according to claim 2, wherein the basic substance is at least one selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, barium hydroxide, ammonia and amine. Purification method of 5-dimercapto-1,3-dithiolane. The method for purifying 4,5-dimercapto-1,3-dithiolane according to any one of claims 1 to 3, wherein the purification solvent is a water-soluble solvent. The method for purifying 4,5-dimercapto-1,3-dithiolane according to claim 4, wherein the water-soluble solvent is at least one selected from alcohols, ethers and ketones.