Oxidation of Compound 28-1 to Title Compound

Example 28

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To a solution of compound 28-1 (120 mg, 0.3 mmol, 1 eq) in DCM (3 mL) was added m-CPBA (104.8 mg, 0.6 mmol, 2 eq). The mixture was stirred at 20° C. for 2 hr. LCMS showed reactant was consumed completely and ˜72% of desired compound was detected (m/z=436.0; RT: 0.82 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 (45.8 mg, 0.1 mmol, 35.4% yield) as a white solid. LCMS (ESI): RT=0.825 min, mass calc. for C₂₂H₂₀F₃NO₃S 435.1, m/z found 436.0 [M+H]⁺; ¹H NMR (400 MHz, DMSO-d₆) δ 9.14 (d, J=1.3 Hz, 1H), 8.58 (d, J=7.6 Hz, 1H), 8.38 (d, J=7.6 Hz, 1H), 8.06 (dd, J=1.6, 8.9 Hz, 1H), 8.00-7.91 (m, 3H), 7.78 (t, J=7.5 Hz, 3H), 4.26-4.10 (m, 1H), 3.49 (s, 3H), 1.23 (d, J=6.6 Hz, 6H).