Oxidation of Compound 27-1 to Desired Product

Example 27

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To a solution of compound 27-1 (120 mg, 0.3 mmol, 1 eq) in DCM (3 mL) was added m-CPBA (47.1 mg, 0.3 mmol, 0.9 eq). The mixture was stirred at 20° C. for 2 hr. LCMS showed reactant was consumed completely and ˜83% of desired compound was detected (m/z=441.9; RT: 0.78 min). The reaction mixture was diluted with DCM (30 mL). This solution was washed sequentially with saturated Na₂SO₃ (20 mL*2), NaHCO₃ (20 mL*2), and brine (30 mL). The organic phase was dried over anhydrous Na₂SO₄, filtered and concentrated in vacuum. The residue was purified by prep-HPLC to give the title compound (65.8 mg, 0.2 mmol, 52.7% yield) as a white solid. LCMS (ESI): RT=0.790 min, mass calc. for C₂₂H₂₀F₃NO₂S 419.1, m/z found 442.0 [M+Na]⁺; ¹H NMR (400 MHz, DMSO-d₆) δ 8.59 (d, J=7.6 Hz, 1H), 8.48 (d, J=1.3 Hz, 1H), 8.23 (d, J=7.5 Hz, 1H), 8.06 (dd, J=1.6, 9.0 Hz, 1H), 7.99-7.89 (m, 3H), 7.86-7.74 (m, 3H), 4.17 (m, 1H), 2.93 (s, 3H), 1.23 (dd, J=2.6, 6.6 Hz, 6H).