Hydrochloric Acid → 5-((4-((2-Carboxyethyl)carbamoyl)phenyl)diazenyl)-2-hydroxybenzoic acid

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Reaction Conditions

Reaction Steps

N-(4-Aminobenzoyl)-β-alanine (100 g) was suspended in water (1300 mL) and methanesulfonic acid (115.4 g) was added to this mixture. The mixture was cooled to 10° C. and a solution of sodium nitrite (34.46 g) in water (200 mL) was added at a rate such that the temperature stayed below 12° C. The mixture was stirred for 30 min and added to an ice-cold solution of salicylic acid (69.65 g), sodium hydroxide (40.35 g) and sodium carbonate (106.9 g) in 1 L water at 7-12° C. After 3 hours at 10° C., the mixture was heated to 60-65° C. and acidified to pH 4.0-4.5 by the addition of hydrochloric acid. After a further 3 hours at 60-65° C., the mixture was cooled to ambient temperature, filtered, washed with water and dried in vacuo to yield Balsalazide. Yield ca. 90%. Balsalazide was transformed into its disodium salt in ca. 85% yield by treatment with aqueous NaOH solution followed by crystallization from n-propanol/methanol.

Provenance & Evidence