To a solution of N-(3-{[2-chloro-5-(methyloxy)phenyl]amino}quinoxalin-2-yl)-3-cyanobenzenesulfonamide (6.02 g, 12.95 mmol) in methanol (20 mL) and 1,4-dioxane (20 mL) was added 6.0 N aqueous sodium hydroxide (40 mL) at room temperature. The solution was stirred at 90° C. for 3.5 h. The reaction was cooled to room temperature and neutralized slowly by adding 2.0 N hydrochloric acid until the pH of the solution became in the 2-3 range at 0° C. The solution was diluted with ethyl acetate (300 mL). The organic layer was washed with saturated aqueous sodium chloride (50 mL) and dried over magnesium sulfate. Filtration and concentration at reduced pressure afforded 3-{[(3-{[2-chloro-5-(methyloxy)phenyl]amino}quinoxalin-2-yl)amino]sulfonyl}benzoic acid (5.921 g, 94%). MS (EI) for C22H17ClN4O5S: 485.0 (MH+)
