CS232961B1 - Preparation Method 2-methyl-4,5-diphenylthiazole - Google Patents

Abstract

A method for preparing 2-methyl-4,5-diphenyl-thiazole of the formula by chlorinating benzoin in chloroform* or another inactive solvent not related to water with a boiling point in the range of 30 to 100 C, then adding an equimolar or up to twice the amount of thionyl chloride dropwise, preferably with the addition of 0.1 to 10% dimethylformamide, after the reaction is completed, the obtained solution is neutralized, dried, an equimolar or up to 50% increased amount of thioacetamide is added to it, after the reaction is completed, the solvent is distilled off, concentrated hydrochloric acid is added, the product is isolated as hydrochloride, after purification by washing with benzene, the product is alkalized and cooled, the product is separated and isolated. Economical preparation of the above diphenylthiazole derivative as a basic semi-finished product in the preparation of photographic sensitizers.

Description

by chlorinating the benzoin in chloroform * or other non-water-related solvents with a boiling point of 30 to 100 ° C, then equimolar or up to twice the amount of thionyl chloride is added dropwise, preferably with the addition of 0.1 to 10% dimethylformamide, The solution obtained is neutralized, dried, treated with an equimolar or up to 50% increased amount of thioacetamide, distilled off the solvent after completion of the reaction, concentrated hydrochloric acid is added, the product is isolated as the hydrochloride, purified by benzene washing and alkaline. upon cooling, precipitates the product and isolates.

Economic preparation of said diphenylthiazole derivative as a basic semi-finished product in the preparation of photographic sensitizers.

The invention relates to a process for the preparation of 2-methyl-4,5-diphenylthiazole of the formula

from benzoin. It is used as a basic semi-finished product in the production of photographic sensitizers. F

The substance is prepared by bromination of desoxybenzoin in acetic acid, carbon disulphide or diethyl ether.

The resulting bromo derivative is condensed with thioacetamide BU3 v'chlorbenzenu, reakění mixture after addition of water and hydrochloric acid freed of steam stripping of chlorobenzene, then an unnecessary ^l 'tek basified and the product is extracted Solvents and isolated by distillation in vacuo. Alternatively, the bromo derivative is condensed with thioacetamide in ethanol, purified as the hydrochloride, and the product is basified, shaken and distilled under reduced pressure to obtain the product (FIAT final report 943, page 43; HUBACHER, Ann. 259, 244/1890).

It has now been found that the above substance can be prepared more preferably from benzoin by its chlorination with thionyl chloride in a chloroform or other inactive water-immiscible solvent at a boiling point of 30 to 100 ° C, such as methylene chloride, ethylene chloride, carbon tetrachloride, diethyl ether. and the like, the resulting chloro derivative is boiled without isolation after neutralization and drying of the reaction solution after addition of an equimolar or up to 50% increased amount of thioacetamide until completion of the reaction. Then the reaction mixture was acidified with hydrochloric acid and all the solvent was distilled off. The residue is stirred with benzene, cooled in an ice bath, the precipitated product hydrochloride is filtered off with suction and washed thoroughly with benzene. The benzene is allowed to vent, the crystals are melted by heating with an excess of dilute ammonia or alkaline hydroxide, the precipitated oil is allowed to solidify, the product is crushed, rinsed with water and air-dried.

The process according to the invention eliminates the need for the preparation of desoxybenzoin, the preparation is carried out without intermediate isolation of the chloro derivative, the reaction proceeds at a relatively low temperature, and without distillation a pure product is capable of further processing.

The example below illustrates an embodiment of the invention.

Exemplary embodiment

To 100 parts by volume of chloroform is added 50 wt. parts of benzoin and 1 part by volume of dimethylformamide. The mixture is heated to boiling and 23 parts by volume of thionyl chloride are added dropwise over 30 minutes. Boil until completion of the reaction, pour the reaction mixture into 1000 parts by volume of water, stir and allow to settle. The chloroform layer was then washed with plenty of water and finally with the addition of 10 wt. parts of sodium hydrogen carbonate and after addition of 20 wt. parts of the thioacetamide are refluxed until the reaction is complete. 130 parts by volume of liquid were distilled off, 50 parts by volume of conc. hydrochloric acid, and any remaining chloroform is distilled off from the mixture. Stir the residue in the flask with 40 parts by volume of benzene and cool to 5 ° C. The precipitated product hydrochloride is filtered off with suction and washed with benzene. After venting the benzene, the intermediate is poured over 150 parts by volume of water and 50 parts by volume of concentrated ammonia, stirred, heated to melting and allowed to solidify. It is then crushed, washed with water and air-dried. 40 wt. 67.5% of theory, m.p. 51-2 ° C.

The same results are obtained with methylene chloride, ethylene chloride, carbon tetrachloride and diethyl ether. Jf

SUBJECT OF THE INVENTION

A process for the preparation of 2-methyl-4,5-diphenylthiazole of formula

Claims (1)

SUBJECT OF THE INVENTION A process for the preparation of 2-methyl-4,5-diphenylthiazole of formula s N C ₃ characterized in that the benzoin is chlorinated in a chloroform or other inactive medium with a water-sewing solvent having a boiling point in the range of 30 to 100 ° C, such as methylene chloride, tetrschloromethane, ethylene chloride, diethyl ether and the like. double the amount of thionyl chloride, preferably with the addition of 0.1 to 10% dimethylformamide by weight of the benzoin used, boiling the mixture until completion of the reaction, neutralizing, drying, adding an equimolar or up to 50% increased amount of thioacetamide, boiling at temperature of the mixture until completion of the reaction, the solvent is distilled off, an equimolar or up to 10-fold concentrated hydrochloric acid is admitted, the product hydrochloride precipitated by cooling is filtered off with suction, freed from impurities by washing with benzene, benzene vented and melted in an excess of aqueous ammonia or aqueous alkaline The alkali-containing product is then isolated and the crystallized product is isolated by cooling.