CS253344B1 - Method of separation of the crude mixture of 4-benzyloxy-4'-hydroxydiphenylsulfone and 4-benzyloxy-2'-hydroxydiphenylsulfone - Google Patents

Abstract

The present invention relates to a process for separating a crude mixture of 4-benzyloxy-4'-hydroxy-diphenylsulfone and 4-benzyloxy-2'-hydrodiphenylsulfone, characterized in that the crude mixture is treated with water at 70-100 ° C and pure 4-benzyl-oxy- 4'-Hydroxydiphenylsulfone is filtered off.

Description

The present invention provides a process for separating a crude mixture of 4-benzyloxy-4'-hydroxydiphenylsulfone and 4-benzyloxy-2'-hydroxydiphenylsulfone based on their different solubility in hot water.

Industrially significant 4-benzyloxy-4'-hydroxydiphenylsulfone is prepared by benzylating 4,4'-dihydroxydiphenylsulfone (Organic Synthesis 25, 9, 1945; CS AO 235 420). However, the preparation of pure 4,4'-dihydroxydiphenylsulfone of formula XII is quite complex. In a number of earlier works, its preparation is carried out by heating the phenol of formula (I) at 160-180 ° C with fuming sulfuric acid for several hours while distilling off the water and pouring the reaction mixture into water after completion of the reaction. The recrystallized product was considered to be a uniform 4,4'-dihydroxydiphenylsulfone of formula III. (Glutz: Liebig's Analen der Chemie 147,2; Annaheim: item 172,36).

OH

HO (I) (III) (IV)

Later, however, it became clear (after refining the analytical methods) that the product thus prepared contains, in addition to the 4,4'-isomer of formula III, 4.2 ^l- dihydroxydiphenylsulfone of formula IV, the separation of which is effected by very complex crystallization from acetone and benzene (Hinkel LE, Seummers GHR: Journal of Chemical Society 1949, 2,855). On an industrial scale, this type of division is hardly feasible.

It has now been found that the 4-benzyloxy-4'-hydroxydiphenylsulfone of the formula V and the 4-benzyloxy-2'-thyroxydiphenylsulfone of the formula VI dissolve selectively in hot water. While the 4-benzyloxy-4'-hydroxydiphenylsulfone of formula V is practically insoluble in hot water, the 4-benzyloxy-2'-hydroxydiphenylsulfone of formula VI dissolves slightly in hot water.

According to the present invention, the crude mixture of 4-benzyloxy-4 -hydroxydifenylsulfonu ¹ V and 4-benzyloxy-2'-hydroxydifenylsulfonu Formula VI is treated with water at a temperature of 70 to 100 ° C and insoluble in hot water, pure 4-benzyloxy-4 ' The hydroxydiphenylsulfone of formula V is filtered off with suction.

(III) (IV) (V) insoluble in hot water (VI) soluble in hot water

The actual benzylation is carried out by dissolving the crude mixture of the two isomers in dilute potassium hydroxide solution and adding the appropriate amount of benzyl chloride in the cold. After stirring at room temperature for 6 hours, the reaction is terminated by boiling for 1 hour. After cooling, the solution is acidified with conc. hydrochloric acid to congo. After aspiration, the precipitated product is stirred with water and the mixture is heated to boiling. The suspension is suction filtered while hot and the filter residue, representing pure 4-benzyloxy-4'-hydroxydiphenylsulfone, is washed with hot water.

The analytical determination of the individual sulfone derivatives is carried out by chromatographic analysis on a silica gel layer mounted on an aluminum support (Silufol) using a 5: 1 benzene-ethyl acetate solution. Detection is by spraying an alkaline solution of the diazonium salt.

The advantage of the above invention is the simplicity with which both isomers can be separated to produce pure 4-benzyloxy-4'-hydroxydiphenylsulfone which is used in the preparation of coloring agents used in color photography.

Example

A 6,000 ml sulfonation flask equipped with a stirrer and a descending condenser was charged with 613 ml of fuming sulfuric acid (monohydrate) with 2000 g of phenol and the mixture was rapidly heated to 180-190 ° C. After distilling off the water, the reaction mixture was poured into hot water. The undissolved gum was filtered off, and a crude mixture of 4,4'- and 4,2'-dihydroxydiphenylsulfone crystallized from the filtrate. After aspiration of the crystalline mixture, the crude mixture is redissolved in hot water, carboraffin is added, filtered and the filtrate is crystallized. After suctioning and drying, the product is obtained. 187 ° C. 67.5 g of crude sulfone are dissolved in 4,500 ml of water and 21.6 g of potassium hydroxide at 35-40 ° C. After dissolution, 60.6 ml of benzyl chloride are added and the mixture is stirred for 6 hours at 20 ° C. The temperature is then raised to boiling and the solution is maintained at this temperature for 1 hour. After cooling, the suspension is acidified to congo. The precipitated product was stirred with hot water, the undissolved portion was aspirated and washed on the filter with hot water. Chromatographically pure 4-benzyloxy-4'-hydroxydiphenylsulfone was obtained in a yield of 16.5 g, i.e. 94% of theory, m.p. 166-168 ° C.

Claims (1)

B, SCOPE OF THE INVENTION Method of dividing a crude mixture of 4-benzyloxy-4'-OCH hydroxydifenylsulfonu V ₂ (V) and 4-benzyloxy-2'-hydroxydifenylsulfonu VI <^ _{S 2} -®-OCH ₂ - (vi) OH, characterized in that the crude mixture of compounds of formula V and VI is treated with water at 70 to 100 ° C, pure 4-benzyloxy-4'-hydroxydiphenylsulfone is filtered off.