Hydrochloric Acid → alpha[(3-Ethylsulphonyl-imidazolidin-2-on-1-yl)-carbonylamino]-p-chlorophenylacetic acid

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Reaction Steps

Sufficient concentrated sodium hydroxide solution just to dissolve the acid was added to a suspension of 11.0 parts by weight of p-chloro-α-aminophenylacetic acid in 110 parts by volume of 50% strength aqueous dioxane. Dilute hydrochloric acid was then added with stirring until a pH of 7.5-8.0 was reached. 13.0 parts by weight of 3-ethylsulphonyl-imidazolidin-2-one-1-carbonyl chloride were then added in portions at about 0° C and the pH of the mixture was maintained at 7.5-8.0 by means of dilute sodium hydroxide solution. Thereafter the mixture was stirred further for as long as an occasional addition of sodium hydroxide solution was still necessary to maintain the pH of 7.5-8.0. The bulk of the dioxane was then removed in vacuo at pH 6.5, about 200 parts by volume of water were added, the mixture was extracted once with ether at pH 9.0 (the ether extract being discarded) and covered with fresh ether, and the pH was brought to 0.5 with stirring. The organic phase was then separated off, washed, dried and completely evaporated in vacuo. The residue was dissolved in hot ethyl acetate; thereafter the same amount of benzene and petroleum ether was added until there is turbidity which (only just) disappears again, and the mixture was left to crystallize.

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