Sodium Hydroxide → 2-[3-Chloro-4-(pyrazol-1-yl)phenyl]propionic acid

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Reaction Conditions

Reaction Steps

20 g (100 mmoles) of 2-(4-amino-3-chlorophenyl) propionic acid are dissolved in 20 ml of concentrated hydrochloric acid and diazotized with 6.9 g of sodium nitrite in 20 ml of water at from -2° to -6° C. The solution is thereafter stirred for a further hour and subsequently stirred into 100 ml of a freshly-prepared, ice-cold, 5.5 N solution of sodium hydrogen sulfite. Heating is then effected slowly to a temperature of from 60° to 70° C. After one hour, acidification is effected with concentrated hydrochloric acid, and the resulting reaction mixture is left at 70° C. for a further 12 hours. 2-(3-chloro-4-hydrazinophenyl)propionic acid forms therein. 22 g (100 mmoles) of 1,1,3,3-tetraethoxypropane are then added thereto. After three hours' heating to 100° C., the reaction mixture is cooled, rendered alkaline with 35% strength sodium hydroxide solution and, in order to saponify the 2-[3-chloro-4-(pyrazol-1-yl)phenyl]propionic acid ethyl ester which is formed in addition to the acid, reheated for one hour. After cooling, impurities are extracted by shaking with benzene; the aqueous phase is acidified with concentrated hydrochloric acid; the product is extracted with diethyl ether; and the ether phase is washed with water, dried and concentrated in a vacuum. 24 g (96% of theory) of 2-[3-chloro-4-(pyrazol-1-yl)phenyl]propionic acid, m.p. 83° to 85° C., are thus obtained.

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