JPH05117224A - Production of 4-benzyloxy-4'-hydroxydiphenylsulfone - Google Patents

Abstract

PURPOSE:To obtain the title compound to be used as e.g. an image stabilizer for thermosensitive recording materials by reaction of 4,4'- dihydroxydiphenylsulfone with benzyl chloride in an alkaline matter-contg. aqueous solution while keeping the pH level of the reaction liquor within a specified range. CONSTITUTION:The objective compound can be obtained by dissolving 1.0mol of 4,4'-dihydroxydiphenylsulfone in an aqueous solution containing 0.8-1.0mol of an alkaline matter followed by reaction with 1.2-1.4mol of benzyl chloride while keeping the pH value of the reaction liquor at 7.5-8.5 (esp., it is preferable that the pH level be adjusted by addition of an alkaline matter). The reaction temperature is pref. 50-80 deg.C. Furthermore, it is preferable that after completing the reaction, an alkaline matter be added to the reaction liquor to adjust its pH level to 8.0-9.0 and the product, i.e., 4-benzyloxy-4'-hydroxydiphenylsulfone, separated at 40-70 deg.C. With this method, the objective compound can be obtained in high yield and in high purity with virtually no content of the raw materials and di-modification as by-product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing 4-benzyloxy-4'-hydroxydiphenyl sulfone, which is a useful raw material used as an image stabilizer for heat-sensitive recording materials.

[0002]

2. Description of the Related Art The reaction between a phenolic hydroxyl group and a halogenated aralkyl, which is a unit reaction for producing an aralkyloxy compound, is generally well known. However, when there are two phenolic hydroxyl groups as in the present invention, both hydroxyl groups are aralkylated, and it is difficult to selectively obtain only one of them in a high yield. A method for producing the same compound as the present invention is disclosed in JP-A-59-225157, and as mentioned above, there is an improvement in benzylating only one of the two hydroxyl groups. That is, 1 mol of 4,4'-dihydroxydiphenyl sulfone (hereinafter referred to as "BPS") is added to an alkaline substance 0.8.
Dissolved in water containing ~ 1.2 mol, temperature 40 ~ 80 ° C
Is reacted with 0.8 to 1.2 mol of benzyl chloride.
The ratio of their use is important. If the amount of benzyl chloride is 0.8 mol or less per 1 mol of BPS as the raw material, the residual ratio of the raw material is high, and if it is 1.2 mol or more, the by-product 4 ,. It is stated that the amount of 4'-dibenzyldiphenyl sulfone tends to increase, and that the same tendency also occurs in the proportion of the alkaline substance used.

[0003]

However, in the above production method, when the amount of benzyl chloride used is increased in order to increase the conversion rate of the raw material BPS to the target compound, the by-product 4,
4'-dibenzyloxydiphenyl sulfone (hereinafter referred to as "di-form") is produced, and when the amount used is reduced, BP as a raw material is produced.
A large amount of S remained, the yield was lowered, and a purification step was necessary in some cases.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors have found that in order to increase the conversion rate of the raw material BPS to a target compound, the amount of benzyl chloride used should be at least 1 to that of BPS. 2 times the molar amount is required, and in order to prevent the formation of the di-body at that time, only one of the two hydroxyl groups of BPS is alkaline substance in the reaction system, including the time of dissolution of BPS in water. It was found that it is important to make it exist with salt. That is, in the present invention, 1.0 mol of 4,4′-dihydroxydiphenyl sulfone is dissolved in water containing 0.8 to 1.0 mol of an alkaline substance, and 1.2 to 1.4 mol of benzyl chloride is reacted. In this case, the reaction solution is reacted at a pH of 7.5 to 8.5 to produce 4-benzyloxy-4′-hydroxydiphenyl sulfone. Further, after the reaction is completed, the reaction solution is alkaline. The substance was added to adjust the pH to 8.0 to 9.0, and 40
A method for producing 4-benzyloxy-4′-hydroxydiphenylsulfone, which comprises separating 4-benzyloxy-4′-hydroxydiphenylsulfone at ˜70 ° C.

In the present invention, the amount of alkaline substance used is extremely important. That is, when the raw material BPS is dissolved in water, when the amount of the alkaline substance used is 1.0 mol or more with respect to 1.0 mol of BPS, the amount of di-form is increased. And when benzyl chloride is added to the reaction system to proceed the reaction, p
It is important that the amount of alkaline substance used for the adjustment of H7.5 to 8.5 is necessary and minimum. At this time, the total amount of the alkaline substance used for BPS dissolution and pH adjustment is preferably 1.2 to 1.5 mol. In general, benzyl chloride reacts to generate chloride ions, and the pH tends to shift to the acidic side during the reaction, so that it is extremely rare to adjust the pH with an acidic substance. The specific amount of the alkaline substance for pH adjustment used is preferably 0.2 to 0.7 mol per 1 mol of BPS as the raw material. When the pH is 7.5 or less, the formation of di-forms can be suppressed, but the progress of the reaction is delayed and a large amount of the raw material remains, resulting in a pH of 8.
When the number is 5 or more, the reaction proceeds rapidly, but the two hydroxyl groups of BPS easily form a salt and the di-form is increased.
Here, examples of the alkaline substance used include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate and the like, of which typical ones are preferable. Examples are sodium hydroxide and sodium carbonate.

Next, the proportion of BPS used as a raw material and benzyl chloride is also important, and in order to improve the yield, the former is 1.0 mol and the latter is 1.2 to 1.4 mol. It is necessary. It was supposed that the amount of benzyl chloride used in the monobenzylation reaction was extremely large as compared with the generally considered amount, and the di-form was naturally produced in a large amount. However, by adjusting the pH in the reaction system as described above, it is possible to suppress the formation of di-form and obtain the target compound in high yield. Here, when the amount of benzyl chloride used does not reach 1.2 mol, the residual amount of BPS as a raw material increases and the yield decreases, and when it exceeds 1.4 mol, the formation of di-form increases.

In the present invention, when BPS is dissolved in an aqueous solution of an alkaline substance, it is preferable to heat it to 40 ° C. to the reaction temperature or lower. Furthermore, the temperature at the time of reacting by adding benzyl chloride to the BPS aqueous solution is preferably 50 to 80 ° C. When it is 50 ° C. or lower, the reaction progresses slowly and the economic efficiency is lowered, and at 80 ° C. or higher. If so, the by-product di body tends to be more produced.

The reaction solution thus obtained is in the form of a suspension in which 4-benzyloxy-4'-hydroxydiphenyl sulfone, which is the object of the present invention, is deposited, and the desired compound is obtained by filtration or centrifugation. Can be taken out. However, since some BPS as a raw material remains, the reaction liquid is adjusted to pH 8.0 to 9.0 with an alkaline substance and then adjusted to 40 to
It is preferable to dissolve the raw material BPS at a temperature of 70 ° C. and then separate it from the aqueous solution. According to the production method of the present invention, since the generation of di-forms that do not dissolve in an alkaline aqueous solution is small, a high-purity product can be easily obtained as described above.
This method is extremely useful in industry. Needless to say, it may be recrystallized or dissolved in an alkaline aqueous solution and then subjected to a purification treatment such as acidification for precipitation to obtain an extremely high purity.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. Example 1 250.3 g (1.0 mol) of BPS was mixed with 4 parts of caustic soda.
60 in 3.0 l of water containing 0.0 g (1.0 mol)
After dissolution at ℃, at the same temperature 164.6 g of benzyl chloride
(1.3 mol) was added dropwise over 2 hours. Further, the reaction was carried out at the same temperature for 7 hours. During the reaction, 120 g of 10% caustic soda aqueous solution was added so as to maintain pH of 7.6 to 7.8.
The reaction was carried out while adding (0.3 mol). After completion of the reaction, a part of the reaction solution was taken and the composition of the product was measured by liquid chromatography. As a result, the target compound, 4-benzyloxy-4′-hydroxydiphenyl sulfone, was found to be 96.0.
%, BPS was 1.0%, and di-form was 0.5%, and other impurities were contained. Further, 10% caustic soda aqueous solution was added to the reaction solution to adjust the pH to 8.5, cooled to 50 ° C., filtered and dried to obtain 4-benzyloxy-4′-hydroxydiphenyl sulfone, 332 g having a melting point of 171 to 173 ° C. . At this time, the yield (based on BPS) was 97.6%. When measured by liquid chromatography, the purity was 98.2%, di body was 0.5%, and BPS was below the detection limit. Comparative Example 1 In Example 1, 250.3 g (1.0 mol) of BPS
Was dissolved in 3.0 l of water containing 52.0 g (1.3 mol) of caustic soda at 60 ° C. and then reacted in the same manner without pH adjustment. When a part of the reaction liquid was taken and the product composition was measured by liquid chromatography, the target compound was 91.7%, BPS was 1.5%, and di-form was 3.8.
%, And other impurities were contained, and especially the di-form was increased. Comparative Example 2 The amount of benzyl chloride used in Example 1 was changed to 12
The same reaction was performed instead of 6.6 (1.0 mol). After the reaction was completed, a part of the reaction solution was taken and the product composition was measured by liquid chromatography. As a result, the target compound was 77.6.
%, BPS was 18.0%, the di-form was 0.5%, and other impurities were contained, and a large amount of unreacted raw material BPS remained.

[0010]

According to the manufacturing method of the present invention, BP as a raw material is used.
High-purity 4 with extremely low content of S and di-products
-Benzyloxy-4'-hydroxydiphenyl sulfone can be obtained in high yield.

Claims (5)

[Claims] 1. Dissolving 1.0 mol of 4,4′-dihydroxydiphenyl sulfone in water containing 0.8 to 1.0 mol of an alkaline substance and reacting 1.2 to 1.4 mol of benzyl chloride. , The pH of this reaction solution is 7.5 to 8.5.
4-benzyloxy-characterized in that
Process for producing 4'-hydroxydiphenyl sulfone 2. The method according to claim 1, wherein the alkaline substance is sodium hydroxide or sodium carbonate. 3. The process according to claim 1, wherein an alkaline substance is added to adjust the pH when the reaction is carried out at a pH of 7.5 to 8.5. 4. The method according to claim 1, wherein the reaction temperature is 50 to 80 ° C. 5. After completion of the reaction, the reaction solution is adjusted to pH 8.0 to 9.
The production method according to claim 1, wherein 4-benzyloxy-4′-hydroxydiphenyl sulfone is separated at 40 to 70 ° C. by adding an alkaline substance to the mixture to adjust the concentration.