JP2712675B2 - Industrial production of phenyl chlorothioformates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention relates to an industrial production method of phenyl chlorothioformates. Phenyl chlorothioformates are very important compounds as intermediates in the production of pharmaceuticals and agricultural chemicals.

<Prior Art> A method is known in which phenyl chlorothioformates are produced by a reaction between phenols and thiophosgene in an organic solvent-water mixed solvent in the presence of a dehydrohalogenating agent, followed by distillation. JP-A-60-61562
No.).

<Problems of the prior art> In the method described in JP-A-60-61562, an organic solvent used as a reaction solvent is carbon tetrachloride,
It is a halogenated hydrocarbon solvent such as chloroform and dichloromethane and an aromatic hydrocarbon solvent such as benzene and toluene. In recent years, halogenated hydrocarbon solvents have been pointed out as environmental pollution problems and toxicity problems, and it is difficult to handle industrially. It has become to. In addition, thiophosgene acts as a chlorinating agent also in the aromatic hydrocarbon solvent, and there is a possibility that a highly toxic halogenated aromatic compound is produced as a by-product.

Further, in the above patent, crude phenylchlorothioformates after the reaction are produced by distillation, but when the reaction solution is distilled without purification, the target product is decomposed, and the distillation yield and distillation The purity of the product is reduced.

In addition, phenols mixed as impurities in crude phenyl chlorothioformates are relatively difficult to separate from the target substance by distillation, and require precise distillation.

<Problems to be Solved by the Present Invention> The inventors of the present invention have conducted intensive studies on an industrial production method of phenyl chlorothioformates, and as a result, have found that a linear, branched or cyclic aliphatic carbon having 5 to 15 carbon atoms as a reaction solvent. By employing a hydrogen solvent, there is no toxicity problem as in a halogenated hydrocarbon solvent, and it is confirmed that the solvent is inert to the present reaction and has no adverse effect on the reaction result such as yield. I started.

Further, during distillation, it was found that the causative substance which causes decomposition and lowers the distillation yield was the remaining raw phenol, and the impurities were removed from the reaction mixture after controlling the reaction conditions or after completion of the reaction. It has been found that removal is difficult even by the operation of separating the liquid after excessive addition of the hydrogen halide reagent, and it can be removed only by separating the reaction solution and then washing again with a dehydrohalogen reagent aqueous solution. Thus, the present invention has been completed.

That is, the present invention relates to (1) crude phenyl produced by the reaction of phenols and thiophosgene in a mixed solvent of an aliphatic hydrocarbon solvent and water in the presence of a dehydrohalogenating agent.
An industrial process for producing phenyl chlorothioformates, comprising separating a solution of chlorothioformates, washing the solution with an aqueous solution of a dehydrohalogenating reagent, and then distilling the solution.

(2) The method according to claim (1), wherein the aliphatic hydrocarbon solvent is a linear, branched or cyclic compound having 5 to 15 carbon atoms. .

<Operation> Hereinafter, the present invention will be described in detail.

Raw phenols applicable to the present invention include unsubstituted phenols, alkyl phenols such as methyl phenol, ethyl phenol and tert-butyl phenol, β-naphthol, and 5,6,7,8-tetrahydro-2-naphthol. Condensed phenols can be used. The phenols may be previously charged to the reactor before the start of the reaction, or may be dissolved in an aqueous solution of a dehydrohalogenating reagent and supplied to the reactor.

The amount of thiophosgene used in the present invention is not problematic if it is at least equimolar to phenol, but if it is too small, the yield of the target phenyl chlorothioformate decreases, and the use of a large excess After the completion of the reaction, a large amount of thiophosgene remains, and thiophosgene is very dangerous because it is a highly toxic compound. Therefore, it is preferable to use the phenol in an amount of 1.01 to 1.5 times the molar amount of the phenol.

The aliphatic hydrocarbon solvent used in the present invention is applicable as long as it has 5 to 15 carbon atoms, such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, and tridecane. Branched aliphatic hydrocarbons such as aliphatic hydrocarbons, dimethylbutane, methylpentane, dimethylpentane, methylhexane, trimethylpentane, dimethylhexane, and methylheptane, cyclopentane, cyclohexane, cyclooctane, methylcyclopentane, methylcyclohexane, and methylcyclohexane Heptane, methylcyclooctane, dimethylcyclopentane, dimethylcyclohexane, dimethylcycloheptane, dimethylcyclooctane, ethylcyclopentane, ethylcyclohexane, ethylcycloheptane, ethylcyclooctane Cycloaliphatic hydrocarbons, as mixtures, petroleum ether, petroleum benzine, ligroin and the like can be mentioned, preferably, industrially easily available, pentane, hexane, octane, cyclohexane, petroleum ether, Petroleum benzine and ligroin. In addition, aliphatic hydrocarbons having 5 or less carbon atoms cannot be applied to the present invention because they are gaseous at ordinary temperature. Aliphatic hydrocarbons having 15 or more carbon atoms may be solid at room temperature, and may be liquid at ordinary temperature. It is not applicable because it has a high boiling point and makes distillation separation from the target product phenyl chlorothioformate difficult.

The amount of the aliphatic hydrocarbon solvent used in the reaction can be in any ratio with respect to thiophosgene used as a reaction raw material.However, when the amount is less than 0.2 times by weight, reproducibility of the reaction is poor, and If the amount is more than twice the weight, not only is there no significant effect on the reaction, but it is not economical.

As the dehydrohalogenating reagent used in the reaction and the treatment after the liquid separation, lithium hydroxide, sodium hydroxide, rubium hydroxide, cesium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, Alkali or alkaline earth metal hydroxides such as barium hydroxide, lithium carbonate, sodium carbonate, alkali metal carbonates such as potassium carbonate, lithium hydrogen carbonate,
Alkali metal bicarbonates such as sodium bicarbonate and sodium bicarbonate can be mentioned, but industrially, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate and potassium bicarbonate are economically advantageous. is there.

Further, the type of the dehydrohalogenating agent used in the reaction and the type of the dehydrohalogenating agent used in the treatment after liquid separation may be different.

The amount of the dehydrohalogenating reagent used in the reaction may be 1 equivalent or more with respect to the phenol, but use of 3 equivalents or more does not bring any benefit and may lower the yield. As the concentration, any concentration can be used, but the amount of water in which the inorganic salt by-produced in the reaction is sufficiently dissolved, or when the phenol is dissolved and supplied to the reactor, the phenol salt and the phenol in the reaction are used. There is no problem as long as the amount of water in which the generated inorganic salt is sufficiently dissolved is normal.
An aqueous solution of dehydrohalogenated reagent having a concentration of 〜30 wt% is used.

The reaction temperature is not limited as long as it is in the range of 0 ° C. to 60 ° C. and the boiling point of the aliphatic carbon to be used.
In the following, coagulation may occur, and at 40 ° C. or higher, the yield may decrease, which is not preferable.

The rate of supplying the aqueous solution of the dehydrohalogenating reagent or the dehydrohalogenating reagent in which phenols are dissolved to the reactor can be carried out without any problem as long as the reaction temperature is within the above-mentioned temperature range.

The reaction is completed at the same time as supplying the aqueous solution of the dehydrohalogenation reagent or the dehydrohalogenation reagent in which phenols are dissolved, but the ripening may be further performed for 0.5 to 6.0 hours.

After completion of the reaction, the reaction solution was settled and separated, and crude phenyl was added.
An aliphatic hydrocarbon solvent solution of chlorothioformeotes is obtained.

The amount of the dehydrohalogenating agent used for washing the crude phenyl chlorothioformate may be any amount that can easily perform the liquid separation operation. With respect to the starting phenols to be used, it is theoretically sufficient if the equivalent is not less than 1.05 equivalents or less with respect to the remaining phenols.
Removal of phenols may be insufficient,
If it is more than 10 equivalents, no benefit is brought about, and the resulting phenyl chlorothioformate may be decomposed, which is not preferable. As the concentration of the dehydrohalogenation reagent in the aqueous solution, any concentration can be used,
There is no problem if the content is 1 to 30% by weight and / or the solubility of the dehydrohalogenating agent used.

After completion of the addition of the dehydrohalogenating agent, the mixture is stirred, then settled, separated, and distilled.

As a distillation apparatus, a short distillation apparatus or a distillation apparatus having a short packed column may be used.
The heating temperature and the degree of decompression differ depending on the type of chlorothioformate, but distillation under reduced pressure is performed
Obtain chlorothioformates.

At a distillation temperature of 60 ° C or lower, a high vacuum is required depending on the type of phenyl chlorothioformate, and a large-scale condenser is required to collect the distilled product. Required and not preferred,
If the temperature is higher than 200 ° C., decomposition of the target phenyl chlorothioformate may occur, which is not preferable.

<Effect of the Invention> According to the present invention, a more industrial method for producing phenyl chlorothioformates has been established.

<Examples> Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to only these examples.

Example 1 57.2 g of thiophosgene and 115 g of pentane were charged into a three-necked flask equipped with a stirrer and a 300-ml dropping funnel, and cooled on a water bath with stirring to bring the internal temperature to 7 ° C.

To this, an aqueous solution of phenol sodium hydroxide composed of 45.0 g of phenol, 20.1 g of sodium hydroxide and 230 g of water prepared in advance was added dropwise over 3 hours, followed by aging at the same temperature for 6 hours.

After completion of the reaction, the reaction mixture was settled, and the aqueous layer was separated and removed to obtain an organic layer. As a result of analysis by gas chromatography, the reaction yield of phenyl chlorothioformate was 97.0%, and the remaining amount of phenol was 1.4 g in total. .

Subsequently, 0.7 g of sodium hydroxide and 7 g of water were added to the solution.
Aqueous sodium hydroxide solution was added, and the mixture was stirred for 10 minutes with a stirrer.

The obtained organic layer was distilled off pentane by heating from room temperature to 50 ° C. under normal pressure, and subsequently under reduced pressure to 4 mmHg,
By heating, 79.0 g of phenyl chlorothioformate was obtained at a distillation temperature of 75 to 76 ° C.

As a result of analysis by gas chromatography, the purity was 99.2%,
The phenol-based yield was 95.0%, and the distillation yield was 97.9%.

[Examples 2 to 5] Using the same apparatus as in Example 1, the reaction was carried out under the conditions shown in Table 1.

 The results are shown in Table 1.

[Comparative Examples 1 and 2] Using the same apparatus as in Example 1, the reaction was carried out under the conditions shown in Table 1.

 The results are shown in Table 1.

Claims (2)

(57) [Claims] 1. A solution of a crude phenylchlorothioformate produced by the reaction of a phenol and thiophosgene in a mixed solvent of an aliphatic hydrocarbon solvent and water in the presence of a dehydrohalogenating agent, followed by liquid separation. An industrial process for producing phenyl chlorothioformates, comprising washing the solution with an aqueous solution of a dehydrohalogenating reagent and then distilling the solution. 2. The method according to claim 1, wherein the aliphatic hydrocarbon solvent is a linear, branched or cyclic compound having 5 to 15 carbon atoms.