3-Fluorobenzenesulfonyl Chloride → 4-{[4-(3-Fluorobenzenesulfonyl)-3,4-dihydro-2H-benzo[1,4]oxazine-6-carbonyl]-amino}-benzoic acid

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Reaction Steps

Step 7 and 8. A solution of 4-[(3,4-dihydro-2H-benzo[1,4]oxazine-6-carbonyl)-amino]-benzoic acid ethyl ester (27 mg, 0.085 mmol) in pyridine (0.4 mL) was treated with a solution of 3-fluoro-benzenesulfonyl chloride (25 mg, 0.13 mmol) in pyridine (0.2 mL). The resulting mixture was stirred at room temperature for 18 hours. The pyridine was evaporated, and the residual crude 4-{[4-(3-fluoro-benzenesulfonyl)-3,4-dihydro-2H-benzo[1,4]oxazine-6-carbonyl]-amino}-benzoic acid ethyl ester was dissolved in ethanol (0.6 mL) and treated with KOH 3N (0.15 mL). The resulting mixture was stirred at room temperature overnight. The mixture was acidified with HCl 3N and evaporated. The residue was purified by preparative HPLC (ZORBAX Eclipse XDB-C18, 21.2×50 mm, 5 μm, gradient acetonitrile/water+0.1% formic acid). 4-{[4-(3-Fluorobenzenesulfonyl)-3,4-dihydro-2H-benzo[1,4]oxazine-6-carbonyl]-amino}-benzoic acid (17.1 mg, 44%) was obtained as an off-white solid, MS (ISP): m/e=455.0 (M−H).

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