Bumetanide → 3-Butylamino-4-(4-chlorosulphonylphenoxy)-5-sulphamyl-benzoic acid

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Reaction Steps

To chlorosulphonic acid (5 ml), 3-butylamino-4-phenoxy-5-sulphamyl-benzoic acid (1 g) was added in portions, while stirring and keeping the temperature below 45°C. The reaction mixture was stirred to 10 minutes and then poured into ice water (10 g of ice and 20 ml of water). The precipitated 3-butylamino-4-(4-chlorosulphonylphenoxy)-5-sulphamyl-benzoic acid was isolated by filtration and without further purification added to aqueous ammonia (10 ml containing 2.5 g of ammonia). Excess of ammonia was removed by evaporation, and the resulting solution was adjusted to pH 2.5 by addition of 4N hydrochloric acid. The precipitated 3-butylamino-4-(4-sulphamylphenoxy)-5-sulphamyl-benzoic acid was isolated by filtration, recrystallized from aqueous ethanol, and dried. The obtained compound had a melting point of 265°C.

Provenance & Evidence