The crude 5-benzenesulfonyl-2-(2-bromo-2-methyl-propylamino)-phenol from step 1 was dissolved in 10 mL DMF and potassium carbonate (0.565 g., 4.096 mmol) was added. The reaction mixture was heated to 80° C. with stirring for 2 hours, then cooled to room temperature and poured onto 100 g of ice in 150 mL 10% aqueous hydrogen chloride. The resulting solid was filtered and dried under vacuum for 18 hours to give 0.570 g (1.79 mmol) of 7-benzenesulfonyl-2,2-dimethyl-4H-benzo[1,4]oxazin-3-one. MS: 316 (M−H)−.
