Trifluoroacetic acid → 4-(4-chloro-2-cyanophenyl)-2-(methoxymethyl)-N-(thiazol-2-yl)-3,4-dihydro-2H-benzo[b][1,4]oxazine-7-sulfonamide

To a solution of 4-(4-chloro-2-cyanophenyl)-N-(4-methoxybenzyl)-2-(methoxymethyl)-N-(thiazol-2-yl)-3,4-dihydro-2H-benzo[b][1,4]oxazine-7-sulfonamide (170 mg, 0.28 mmol) in dichloromethane (10 mL) was added trifluroacetic acid (0.7 mL, Spectrochem) at 0° C. and the mixture was allowed to stir at room temperature for 4 h. The volatiles were removed under reduced pressure and the residue was basified (pH˜10) with saturated aqueous NaHCO3 solution. The aqueous layer was extracted with dichloromethane (2×100 mL). The combined organic layers were dried over sodium sulfate, filtered and concentrated under reduced pressure to get the crude material which was further purified by column chromatography (silica gel 100-200 mesh, 0-2% methanol in dichloromethane) to obtain 4-(4-chloro-2-cyanophenyl)-2-(methoxymethyl)-N-(thiazol-2-yl)-3,4-dihydro-2H-benzo[b][1,4]oxazine-7-sulfonamide (70 mg, 51.5%) as an off white solid. m/z (ESI) 476.8 (M+H)+. 1H NMR (400 MHz, DMSO) δ 12.71 (s, 1H), 8.13 (d, J=2.5 Hz, 1H), 7.84 (dd, J=8.8, 2.5 Hz, 1H), 7.59 (d, J=8.8 Hz, 1H), 7.35-7.04 (m, 3H), 6.80 (d, J=4.6 Hz, 1H), 6.57 (d, J=8.5 Hz, 1H), 4.46 (d, J=4.6 Hz, 1H), 3.80-3.76 (m, 1H), 3.65-3.57 (m, 3H), 3.29 (s, 3H).