Spiro[piperidine-4,4′-pyrrolo[2,1-c][1,4]benzoxazine] (257 mg, 0.928 mmol), 4-fluoro-3-methylsulfonyl-benzoic acid (203 mg, 0.928 mmol), triethylamine (518 μL, 3.71 mmol), and EDC (196 mg, 1.02 mmol) were combined in dichloromethane (10 mL) and the reaction mixture was stirred at room temperature for 4 d. The reaction mixture was washed three times with a 1M solution of hydrochloric acid, followed by three washes with a saturated aqueous solution of sodium bicarbonate, followed by three washes of a saturated aqueous solution of sodium chloride. The organic layer was dried over sodium sulfate, filtered, and evaporated to dryness to yield the crude product. The crude material was purified column chromatography utilizing a gradient of 0-75% ethyl acetate in hexanes to yield (4-fluoro-3-methylsulfonyl-phenyl)-spiro[piperidine-4,4′-pyrrolo[2,1-c][1,4]benzoxazine]-1-yl-methanone (222 mg, 54%) as a colorless oil. ESI-MS m/z calc. 440.1. found 441.1 (M+1)+; Retention time: 1.51 minutes (3 min run).
