Chlorosulfonic acid → 4-(2-cyano-4-(trifluoromethyl)phenyl)-6-fluoro-3,4-dihydro-2H-benzo[b][1,4]oxazine-7-sulfonyl chloride

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Reaction Steps

To a vial charged with 2-(6-fluoro-2H-benzo[b][1,4]oxazin-4(3 H)-yl)-5-(trifluoromethyl)benzonitrile (1.85 g, 5.74 mmol) was added DCM (23 mL). The resulting solution was cooled in an ice water bath prior to the addition of chlorosulfonic acid (1.526 ml, 22.96 mmol), faster than dropwise. After 30 min of stirring LC-MS of the resulting yellow/brown solution indicated desired product mass as the main mass (M+23) with consumption of starting material. The solution was added to ice water, and extracted 2× with DCM. The combined organics were dried with Na2SO4, filtered, and dried under reduced pressure. The crude material was purified with a 25 g SNAP column ramping EtOAc in heptane (0-25%, then isocratic at 25%, 10% DCM throughout) providing product as a white foam 4-(2-cyano-4-(trifluoromethyl)phenyl)-6-fluoro-3,4-dihydro-2H-benzo[b][1,4]oxazine-7-sulfonyl chloride (1.80 g, 4.28 mmol, 74.5% yield). 1H NMR (400 MHz, CHLOROFORM-d) δ ppm 3.87-3.94 (m, 2 H) 4.40-4.49 (m, 2 H) 6.37 (d, J=11.15 Hz, 1 H) 7.50 (d, J=6.46 Hz, 1 H) 7.64 (d, J=8.51 Hz, 1 H) 7.94-8.01 (m, 1 H) 8.09 (dd, J=1.57, 0.59 Hz, 1 H). m/z (ESI) 443.1 (M+Na)+.

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