Sodium Hydroxide → Salclobuzate Sodium

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Reaction Conditions

Reaction Steps

A 22 L, five neck round bottom flask, was equipped with an overhead stirrer, reflux condenser, thermocouple temperature read out, and heating mantle. The following reaction was run under a dry nitrogen atmosphere. Reagent acetone (13000 mL) and 4-[(4-chloro-2-hydroxy-benzoyl)amino]butanoic acid (500.0 g, 1.94 mol) were charged to the reactor and stirring was started. The reaction slurry was heated to 50° C. until a hazy brown solution was obtained. The warm solution was pumped through a warm pressure filter dressed with Whatman #1 paper into a clean 22 L reactor. The clear yellow filtrate was heated to 50° C. while stirring. Sodium hydroxide solution (50% aqueous; 155 g, 1.94 mol) was charged to the reactor while maintaining vigorous agitation. After the base addition was complete, the reactor was heated to reflux (60° C.) for 2.5 hours and then allowed to cool slowly to ambient temperature. The product was isolated by vacuum filtration through a sintered glass funnel and dried in a vacuum oven at 50° C. for 24 hours to give 527.3 g of sodium 4-[(4-chloro-2-hydroxybenzoyl)amino]butanoate as an off-white solid. Using acetone in the final stage of the synthesis always resulted in the production of the anhydrous crystalline form. The yield was 97.2%. The Form I prepared was a crystalline polymorph having a melting point onset of about 215.07° C. and characterized by an X-ray powder diffractogram substantially as shown in FIG. 1. A DSC scan, TGA spectrum, and Sorption/desorption curve of the Form I prepared are shown in FIGS. 6, 11, and 22, respectively. FTIR spectra of the Form I prepared are shown in FIGS. 16A and 16B.

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