JPH09263575A - Mercapto compounds, production of the same, tetraol compound and production of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new mercapto compound for optical material and curing agent for resin, etc., having high sulfur content and low in offensive smell by reacting bis-(2-mercaptoethyl)sulfide and specific pentaerythritol derivatives in the presence of a base. SOLUTION: This new mercapto compound is tetrakis(7-mercapto-2,5-dithia- heptyl)methane expressed by formula I, having high sulfur atom content, polyfunctionality and low in offensive odor, useful in organic optical material region as raw monomers giving a high refractive index resin caused by the high sulfur content and curing agent, etc., of an epoxy resin. This new mercapto compounds is obtained by carrying out the reaction of bis-(2-mercaptoethyl)sulfite and pentaerythritoltetrahalide or sulfonic acid ester of pentaerythritol expressed in formula (R is a 1-4C alkyl, phenyl, chlorophenyl, nitrophenyl, tolyl) in the presence of a base.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a mercapto compound, a method for producing a mercapto compound, a tetraol compound and a method for producing a tetraol compound, particularly a novel mercapto compound and a method for producing the same, and a method for producing the mercapto compound. The present invention relates to a novel tetraol compound as an intermediate and a method for producing the same.

[0002]

2. Description of the Related Art In the field of organic optical materials, it has been attempted to increase the content of sulfur atoms having high atomic refraction in the monomer molecule of the resin raw material for the purpose of increasing the refractive index of the resin. (For example, Japanese Patent Laid-Open No. 2-2708)
59, JP-A-5-208950). Here, in order to increase the sulfur atom content, a mercapto compound is generally used. As the mercapto compound, low molecular weight mercapto compounds such as methanethiol, ethanethiol and ethanedithiol are widely known. However, such a low molecular weight mercapto compound has a peculiar odor based on a mercapto group, and the amount used is often limited due to the composition ratio with other resin raw materials used for curing the resin. . For this reason, the low molecular weight mercapto compound is not easy to handle in terms of giving an operator discomfort, and it is difficult to ideally increase the content of sulfur atoms in the resin.

For this reason, trimethylolpropane tris- (thioglycolate) and pentaerythritol tetrakis- (thioglycolate) are used instead of low molecular weight mercapto compounds and have large molecular weights used as epoxy resin curing agents. The use of functional mercapto compounds is conceivable. However, although this type of mercapto compound has a small molecular weight and a good operability with less odor, it has a small sulfur atom content in the molecule, and therefore ideally increases the content of sulfur atoms in the resin. Is difficult.

Therefore, as the mercapto compound, a compound having a high content of sulfur atoms, polyfunctionality and a large molecular weight (small odor) is desired, and such a mercapto compound is currently provided. Has not reached.

An object of the present invention is to provide a mercapto compound having a high content of sulfur atoms, polyfunctionality and a low odor.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of such circumstances, and as a result, found a mercapto compound having a high sulfur atom content, a polyfunctionality and a low odor. I arrived.

That is, the mercapto compound according to the present invention is a mercapto compound represented by the following formula (1).

[0008]

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The method for producing the mercapto compound represented by the formula (1) includes a step of reacting bis- (2-mercaptoethyl) sulfite with pentaerythrityl tetrahalide in the presence of a base. Here, pentaerythrityl tetrahalide is, for example, pentaerythrityl tetrabromide.

Another method for producing the mercapto compound represented by the formula (1) is to use bis- (2-mercaptoethyl) sulfite and a pentaerythritol sulfonic acid ester represented by the following general formula (2) in the presence of a base. Includes the steps of reacting below.

[0011]

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In the general formula (2), R has 1 carbon atom.
~ 4 alkyl group, phenyl group, chlorophenyl group, nitrophenyl group or tolyl group.

Still another method for producing the mercapto compound represented by the formula (1) is as follows by reacting the mercapto compound represented by the following formula (3) with pentaerythrityl tetrahalide in the presence of a base and a catalyst. A step of obtaining a tetraol compound represented by the formula (4), and reacting the obtained tetraol compound with thiourea in the presence of a mineral acid,
It includes a step of obtaining a reaction product of the tetraol compound and thiourea, and a step of hydrolyzing the reaction product by making it alkaline with a base.

[0014]

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[0015]

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In this production method, the pentaerythrityl tetrahalide is, for example, pentaerythrityl tetrabromide. The catalyst is, for example, a quaternary ammonium salt or a quaternary phosphonium salt.

The tetraol compound according to the present invention is usually used as an intermediate for producing the mercapto compound represented by the above formula (1), and is represented by the following formula (4).

[0018]

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This method for producing a tetraol compound includes a step of reacting a mercapto compound represented by the following formula (3) with pentaerythrityl tetrahalide in the presence of a base and a catalyst.

[0020]

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[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The mercapto compound according to the present invention is represented by the following formula (1).

[0022]

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Since this mercapto compound has a high content of sulfur atoms, it is useful, for example, for increasing the content of sulfur atoms in a resin used as an organic optical material. Specifically, this mercapto compound, when used as a monomer for producing a resin for an organic optical material, can increase the sulfur atom content in the intended resin,
As a result, it is possible to easily increase the refractive index of the resin. The mercapto compound of the present invention used for such a purpose has a relatively large molecular weight and has a peculiar odor based on the mercapto group, and thus has good handleability.

The mercapto compound of the present invention is used for the above-mentioned organic optical materials, and in place of the conventionally known mercapto compound, a vulcanizing agent, a cross-linking agent, an epoxy resin curing agent, a polymerization adjusting agent. It can also be used for a wide range of fields such as agents and antioxidants.

Next, a method for producing the above-mentioned mercapto compound will be described. Here, three types of production methods will be described as the production method of the above-mentioned mercapto compound.

(First Manufacturing Method) In the first manufacturing method,
Bis- (2-mercaptoethyl) sulfite (hereinafter,
DMDS) and pentaerythrityl tetrahalide are used as raw materials, and both are reacted in the presence of a base.

As the pentaerythrityl tetrahalide used here, various halides such as pentaerythrityl tetrabromide, pentaerythrityl tetrachloride, pentaerythrityl tetraiodide and the like can be used, but they are reactive and economical. In terms of the point, it is preferable to use pentaerythrityl tetrabromide.

The base used in this reaction may be either an inorganic base or an organic base. Examples of the inorganic base include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as sodium carbonate and potassium carbonate.
On the other hand, examples of the organic base include alkali metal alcoholates such as sodium methylate and sodium ethylate, and aliphatic amines such as triethylamine and tributylamine. Of these various bases, it is most preferable to use sodium hydroxide in terms of reactivity and economy.

When the above-mentioned DMDS and the above-mentioned pentaerythrityl tetrahalide are reacted with each other, they are mixed and reacted with heating while adding the above-mentioned base while stirring. The reaction temperature at this time is usually preferably set to 30 to 120 ° C, more preferably 70 to 120 ° C. When the reaction temperature is lower than 30 ° C., the reaction rate becomes too slow, and the practicality of the present production method becomes poor.
On the other hand, if the reaction temperature exceeds 120 ° C., side reactions are likely to occur, and the yield of the target mercapto compound may decrease.

The reaction may be carried out under normal pressure, that is, atmospheric pressure, or under increased pressure. When the reaction is carried out under pressure, the pressure range is preferably set to atmospheric pressure to 15 atm (gauge pressure), more preferably to atmospheric pressure to 10 atm (gauge pressure). If the pressure exceeds 15 atm, the usable reactor is limited, which is not preferable.

When the DMDS and pentaerythrityl tetrahalide are reacted in this way, a reaction solvent may be used. As the reaction solvent, for example, aromatic hydrocarbon solvents such as benzene, toluene and xylene, and lower alcohol solvents such as methanol, ethanol and propyl alcohol can be used. Further, DMDS which is a reaction raw material can be used as a reaction solvent. In addition,
As the reaction solvent, it is preferable to use toluene or DMDS, but especially from the viewpoint of economy, DMDS which is a raw material
It is preferable to use

The proportion of DMDS and pentaerythrityl tetrahalide used is preferably DMDS in an amount of 4 times or more, more preferably 4 to 50 times, the amount of DMDS with respect to pentaerythrityl tetrahalide. D
When the ratio of MDS used is less than 4 times by mole, the selectivity of the reaction may be lowered, and the yield of the target mercapto compound may be lowered. On the contrary, when the proportion of DMDS used exceeds 50 times by mole, the yield of the mercapto compound is hard to increase in proportion to the amount used, which is not economical.

The amount of the base used is usually preferably set to 4 to 6 times the molar amount of pentaerythrityl tetrahalide. If the amount used is less than 4 times the molar amount, the yield of the target mercapto compound may decrease. vice versa,
If it exceeds 6 times by mole, side reactions are likely to occur.

During the reaction, a catalyst may be added to accelerate the reaction. Examples of usable catalysts include tetraethylammonium bromide and tetra-n.
-Propyl ammonium bromide, tetra-n-butyl ammonium bromide, tetra-n-pentyl ammonium bromide, tetra-n-hexyl ammonium bromide, tetra-n-heptyl ammonium bromide, tetra-n-octyl ammonium bromide, tetra-n
-Decyl ammonium bromide, tetra-n-amyl ammonium bromide. Quaternary ammonium salts such as trioctylmethylammonium chloride, tetraethylphosphonium bromide, tetra-n-propylphosphonium bromide, tetra-n-butylphosphonium bromide,
Tetra-n-pentylphosphonium bromide, tetra-
Examples thereof include quaternary phosphonium salts such as n-hexylphosphonium bromide, tetra-n-heptylphosphonium bromide, tetra-n-octylphosphonium bromide and tetraphenylphosphonium bromide. Among them, it is preferable to use tetra-n-butylammonium bromide from the viewpoint of economy. The amount of such a catalyst to be used is usually preferably set to 0.01 to 1.0 times the mol of pentaerythrityl tetrahalide.

The time required to complete the reaction varies depending on the reaction conditions, that is, the reaction temperature and pressure, but is generally 0.5.
~ 24 hours. The progress of the reaction can be easily confirmed using high performance liquid chromatography.

The desired mercapto compound can be obtained by separating the reaction solution, washing it with water, and concentrating it.

(Second Manufacturing Method) In the second manufacturing method,
The target mercapto compound can be obtained by using pentaerythritol sulfonic acid ester instead of the pentaerythrityl tetrahalide used in the first production method and performing the same reaction as in the first production method.

The pentaerythritol sulfonic acid ester used in this production method is represented by the following general formula (2).

[0039]

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In the general formula (2), R is a methyl group,
An alkyl group having 1 to 4 carbon atoms such as an ethyl group, an n-propyl group, an n-butyl group, a phenyl group, a chlorophenyl group, a nitrophenyl group or a tolyl group.

The pentaerythritol sulfonic acid ester represented by the general formula (2) is, for example,
Pentaerythritol tetrakis (methane sulfonate), pentaerythritol tetrakis (ethane sulfonate), pentaerythritol tetrakis (propane sulfonate), pentaerythritol tetrakis (benzene sulfonate), pentaerythritol tetrakis (chlorobenzene sulfonate), pentaerythritol tetrakis (nitrobenzene sulfonate), pentaerythritol Tetrakis (toluene sulfonate)
And the like. Of these, pentaerythritol tetrakis (benzene sulfonate) and pentaerythritol tetrakis (toluene sulfonate) are preferably used from the viewpoint of easy handling and economy.

(Third Manufacturing Method) In the third manufacturing method,
A tetraol compound represented by the following formula (4) is produced as an intermediate, and an intended mercapto compound is produced from this tetraol compound. Hereinafter, this manufacturing method will be described in the order of steps.

[0043]

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First, a mercapto compound represented by the following formula (3) and pentaerythrityl tetrahalide are used as reaction raw materials to produce a tetraol compound represented by the above formula (4).

[0045]

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The mercapto compound represented by the formula (3) is
It can be synthesized from 2-mercaptoethanol and ethylene sulfide or from ethylene oxide and ethanedithiol. On the other hand, as the pentaerythrityl tetrahalide, the same one as used in the first production method can be used, but it is preferable to use pentaerythrityl tetrabromide in terms of reactivity and economy.

When the tetraol compound represented by the formula (4) is produced, the mercapto compound represented by the formula (3) is reacted with pentaerythrityl tetrahalide in the presence of a base and a catalyst. The base that can be used here is an inorganic or organic base (especially aliphatic amines) similar to that used in the first production method, but in particular, in view of reactivity and economy, water is used. Sodium oxide is preferred. On the other hand, the catalyst that can be used here is a quaternary ammonium salt or a quaternary sulfonium salt similar to that used in the first production method, but tetra-n-butyl ammonium bromide or tetra-n-butyl ammonium bromide or tetra- Preference is given to using n-butylphosphonium bromide.

When the mercapto compound represented by the formula (3) is reacted with pentaerythrityl tetrahalide, the two are mixed, and this is mixed with an aromatic hydrocarbon solvent such as benzene, toluene, xylene, or methanol, ethanol. , A lower alcohol solvent such as propyl alcohol, a catalyst and a base are further added and the mixture is stirred. The reaction temperature is preferably set to 20 to 120 ° C, and 5
More preferably, the temperature is set to 0 to 100 ° C. When the reaction temperature is lower than 20 ° C., the reaction rate becomes too slow, and the practicality of the present production method becomes poor. Conversely, the reaction temperature is 120 ℃
If it exceeds, the side reaction is likely to occur, and the yield of the tetraol compound to be produced in this step may decrease.

The ratio of the mercapto compound represented by the formula (3) and the pentaerythrityl tetrahalide used is preferably set to 4 times or more the mole of the mercapto compound represented by the formula (3) as compared with the pentaerythrityl tetrahalide. It is more preferable to set the molar ratio to 4 to 6 times. When the amount of the mercapto compound represented by the formula (3) used is less than 4 times by mole, the yield of the tetraol compound may decrease. On the other hand, if the amount exceeds 6-fold, the yield of the tetraol compound is unlikely to increase in proportion to the amount used, which is not economical.

The amount of the base used is preferably 0.8 to 1.2 times the mol of the mercapto compound represented by the formula (3). It is more preferably equimolar. If the amount of the base used is outside this range, the yield of the tetraol compound may decrease. Further, the amount of the catalyst used is 0.01 to 0.01 of pentaerythrityl tetrahalide.
It is preferably set to 1.0 times mol. When the amount of the catalyst used is less than 0.01 times by mole, the reaction rate becomes slow. On the other hand, when it exceeds 1.0 times by mole, the yield of the tetraol compound hardly increases in proportion to the amount used, which is not economical.

The time required to complete the reaction varies depending on the reaction conditions, that is, the reaction temperature, etc., but is generally 0.5 to 24.
Time. The progress of the reaction can be easily confirmed using high performance liquid chromatography.

The tetraol compound of interest in this step can be obtained by cooling the reaction solution to room temperature, filtering the crystalline substance, separating and washing with water, and further concentrating it.

Next, the obtained tetraol compound is reacted with thiourea in the presence of a mineral acid to obtain a reaction product of the tetraol compound and thiourea. Examples of the mineral acid used here include hydrochloric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, phosphoric acid, and the like, but hydrochloric acid is preferable because it can suppress the coloring of the target mercapto compound. preferable.

The amount of thiourea used to react with the tetraol compound is preferably set to 4 times or more the molar amount of the tetraol compound, more preferably 4 to 12 times the molar amount. When the amount of thiourea used is less than 4 times the molar amount,
The yield of the target mercapto compound may decrease. On the other hand, if the amount exceeds 12 times, the yield of the mercapto compound is unlikely to increase in proportion to the amount used, which is not economical. The amount of mineral acid used is 4 for tetraol compounds.
It is preferable to set the molar ratio to 16 times. If the amount of the mineral acid used is less than 4 times the molar amount, the yield of the target mercapto compound may decrease. On the other hand, if the amount exceeds 16 times, the yield of the mercapto compound is unlikely to increase in proportion to the amount used, which is not economical.

The reaction temperature here is usually from room temperature to
It is preferable to set within the range of the reflux temperature.

Next, the obtained reaction product is made alkaline with a base and hydrolyzed to be converted into a mercapto. Thereby, the target mercapto compound is obtained.

The base used in this step is, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, ammonia, or an aliphatic amine such as triethylamine or hydrazine. The amount of such a base used is usually preferably 4 times or more the molar amount of the tetraol compound represented by the formula (4), and more preferably 4 to 16 times the molar amount. If the amount of the base used is less than 4 times the molar amount, the yield of the target mercapto compound may decrease. On the contrary, when the molar ratio exceeds 16 times,
It is difficult to increase the yield of the mercapto compound in proportion to the amount used, which is not economical.

Incidentally, such a hydrolysis reaction is usually
It is preferably carried out in the range of room temperature to reflux temperature.

The mercapto compound thus obtained can be purified by a general method of washing with acid, washing with water and concentration after extracting from the reaction solution with an organic solvent such as toluene.

The series of mercapto-forming steps according to this production method are known methods described in JP-A-2-270859.

[0061]

Example 1 A 1,000 ml four-necked flask equipped with a stirrer, a thermometer and a condenser was prepared, and 600 g (3.9 mol) of bis- (2-mercaptoethyl) sulfite was prepared. , Pentaerythrityl tetrabromide 50 g (0.129
Mol) and 4.1 g (0.0127 mol) of tetra-n-butylammonium bromide as a catalyst.
Next, this was heated to 80 to 100 ° C., and 219 g (0.53 mol) of a 10% aqueous sodium hydroxide solution was added dropwise under a nitrogen atmosphere. Then, it stirred for 3 hours, maintaining at 80-100 degreeC.

Next, the reaction solution was cooled to 50 ° C., separated and washed twice with water, and then the organic layer was concentrated under reduced pressure. When the concentrate was separated by silica gel column chromatography, the tetrakis-formula represented by the above formula (1) was obtained.
72.6 g (0.107 mol) of (7-mercapto-2,5-dithiaheptyl) methane was obtained. The yield based on pentaerythrityl tetrabromide was 82.9.
%Met.

The resulting tetrakis- (7-mercapto-
2,5-dithiaheptyl) methane elemental analysis value and N
The MR analysis results are shown in Table 1 and Table 2, respectively.

[0064]

[Table 1]

[0065]

[Table 2]

Example 2 50 g (0.129) of pentaerythrityl tetrabromide
89.8 g (0.129 mol) of pentaerythritol tetrakis (benzenesulfonate) was used instead of tetraerythritol tetrakis (benzene sulfonate), and the same procedure as in Example 1 was carried out, except that tetrakis- (7-mercapto) represented by the above formula (1) was used. -2
70.1 g (0.09 mol) of 5-dithiaheptyl) methane was obtained. The yield of pentaerythritol tetrakis (benzene sulfonate) was 79.8%.
Met. The elemental analysis value and the NMR analysis result of the obtained tetrakis- (7-mercapto-2,5-dithiaheptyl) methane were the same as those in Example 1.

Example 3 A 1,000 ml four-necked flask equipped with a stirrer, a thermometer and a condenser was prepared, and 71.8 g (0.2%) of 2-[(2-mercaptoethyl) thio] ethanol was prepared. 52 mol) and 50 g of pentaerythrityl tetrabromide
(0.129 mol) and 1.7 g (0.005 mol) of tetra-n-butylphosphonium bromide as a catalyst were added. Furthermore, 325 g of toluene was added, and 10
% Aqueous sodium hydroxide solution (104 g, 0.52 mol) was gradually added. Then, heat to 70-80 ° C for 8
Stirred for hours.

Next, the reaction solution was cooled to 40 ° C., separated, washed twice with water, and then the organic layer was concentrated under reduced pressure.
70.8 g of tetrakis- (7-hydroxy-2,5-dithiaheptyl) methane represented by the above formula (4) was obtained. The yield based on pentaerythrityl tetrabromide was 89.1%.

The resulting tetrakis- (7-hydroxy-
2,5-dithiaheptyl) methane elemental analysis value and N
The MR analysis results are shown in Table 3 and Table 4, respectively.

[0070]

[Table 3]

[0071]

[Table 4]

Example 4 A 1,000 ml four-necked flask equipped with a stirrer, a thermometer and a condenser was prepared, and 71.8 g (0.2%) of 2-[(2-mercaptoethyl) thio] ethanol was prepared. 52 mol) and 50 g of pentaerythrityl tetrabromide
(0.129 mol) and 1.7 g (0.005 mol) of tetra-n-butylphosphonium bromide as a catalyst were added. Furthermore, 325 g of toluene was added, and 10
% Aqueous sodium hydroxide solution (104 g, 0.52 mol) was gradually added. Then, heat to 70-80 ° C for 8
Stirred for hours.

Next, the reaction solution was cooled to 40 ° C., separated, washed twice with water, and then the organic layer was concentrated under reduced pressure. This concentrated solution was dissolved in 214.8 g (1.61 mol) of 35% hydrochloric acid, and 107.6 g (1.38 mol) of thiourea was added to obtain 1
The mixture was stirred at 00 to 110 ° C for 5 hours. Then, the reaction solution was cooled to room temperature, and 104.7 g (1.
73 mol) at 20-40 ° C. to make it alkaline, 1
Stirred at 00 ° C. for 2 hours.

Next, the reaction solution was cooled to room temperature, 350 ml of toluene was added and extraction operation was performed to separate the organic layer.
The organic layer was washed with 100 ml of 5% hydrochloric acid and then washed with 100% water.
It was washed twice with ml, 20 g of magnesium sulfate was added and dried. Furthermore, when the organic layer was concentrated under reduced pressure and the concentrate was separated by silica gel column chromatography, 71.6 g of tetrakis- (7-mercapto-2,5-dithiaheptyl) methane represented by the above formula (1) was obtained.
(0.105 mol) was obtained. The yield based on pentaerythrityl tetrabromide was 81.4%.

The resulting tetrakis- (7-mercapto-
2,5-dithiaheptyl) methane elemental analysis value and N
The MR analysis result was the same as in the case of Example 1.

[0076]

Industrial Applicability According to the present invention, a novel mercapto compound represented by the above formula (1), which has a high sulfur atom content, is multifunctional and has a low odor, is provided.

Further, according to the method for producing a mercapto compound according to the present invention, a novel mercapto compound represented by the above formula (1) having a high sulfur atom content and being multifunctional and having little odor is produced. be able to.

Further, according to the present invention, useful as an intermediate for producing the mercapto compound according to the present invention,
Novel tetraol compounds are provided.

Furthermore, according to the method for producing a tetraol compound of the present invention, a novel tetraol compound useful as an intermediate for producing the mercapto compound of the present invention can be produced.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Michio Suzuki 1 346 Miyanishi, Harima-cho, Kako-gun, Hyogo Prefecture Sumitomo Seika Chemical Co., Ltd.

Claims (10)

[Claims] 1. A mercapto compound represented by the following formula (1). Embedded image 2. A method for producing a mercapto compound represented by the following formula (1), which comprises a step of reacting bis- (2-mercaptoethyl) sulfite with pentaerythrityl tetrahalide in the presence of a base. Embedded image 3. The method for producing a mercapto compound according to claim 2, wherein the pentaerythrityl tetrahalide is pentaerythrityl tetrabromide. 4. The following formula (1) comprising a step of reacting bis- (2-mercaptoethyl) sulfite with a pentaerythritol sulfonic acid ester represented by the following general formula (2) in the presence of a base. A method for producing a mercapto compound represented by: Embedded image Embedded image [In the general formula (2), R represents an alkyl group having 1 to 4 carbon atoms, a phenyl group, a chlorophenyl group, a nitrophenyl group or a tolyl group. ] 5. A step of reacting a mercapto compound represented by the following formula (3) with pentaerythrityl tetrahalide in the presence of a base and a catalyst to obtain a tetraol compound represented by the following formula (4): A step of reacting the tetraol compound with thiourea in the presence of a mineral acid to obtain a reaction product of the tetraol compound and the thiourea, and by making the reaction product alkaline with a base, And a step of hydrolyzing, a method for producing a mercapto compound represented by the following formula (1). Embedded image [Chemical 6] Embedded image 6. The method for producing a mercapto compound according to claim 5, wherein the pentaerythrityl tetrahalide is pentaerythrityl tetrabromide. 7. The method for producing a mercapto compound according to claim 5, wherein the catalyst is a quaternary ammonium salt. 8. The method for producing a mercapto compound according to claim 5, wherein the catalyst is a quaternary phosphonium salt. 9. A tetraol compound represented by the following formula (4): Embedded image 10. A tetraol compound represented by the following formula (4), which comprises a step of reacting a mercapto compound represented by the following formula (3) with pentaerythrityl tetrahalide in the presence of a base and a catalyst. Production method. Embedded image Embedded image