A mixture of 7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-one (740 mg, 2.25 mmol, Example 4), 2-methyl-2-propane-sulfinamide (819 mg, 6.76 mmol, Aldrich), and tetraethoxytitanium (6.07 mL, 29.3 mmol, Aldrich) in dry THF (15 mL) was heated at 75° C. for 24 hours under nitrogen atmosphere. The mixture was cooled to RT and brine and aqueous, saturated bicarbonate solution were added while rapidly stirring. After 1 h, the resulting suspension was filtered through celite, and the filter cake was washed with EtOAc. The filtrate was washed with brine and dried over MgSO4. The solvent was removed under reduced pressure and the remaining residue was purified by flash chromatography on silica gel (0-20% EtOAc/hexanes) to afford the title product as an orange solid. MS m/z=423.8 [M+H]+. Calculated for C16H13BrClFN2O2S: 431.71.
