Lithium Hydroxide → 3-Amino-4-phenoxy-5-sulfamoylbenzoic acid

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Reaction Steps

A suspension of 3-nitro-4-phenoxy-5-sulphamyl-benzoic acid (20 g) in water (100 ml) was adjusted to a pH of 8 by the addition of 1N lithium hydroxide. The resulting solution was hydrogenated at room temperature and 1.1 atmosphere hydrogen pressure, using a palladium-on-carbon catalyst (0.6 g catalyst containing 10% Pd). After the hydrogen uptake had become negligible, the catalyst was removed by filtration, and the 3-amino-4-phenoxy-5-sulphamyl-benzoic acid was precipitated from the filtrate by the addition of 4N hydrochloric acid until the pH was 2.5. After recrystallization from aqueous ethanol and drying, the melting point was 255°-256° C.

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