6-(Benzylthio)-1-(5-bromo-2-methoxyphenyl)quinolin-2(1H)-one (5.48 g, 12.11 mmol) was diluted with MeCN (38.0 ml), AcOH (1.444 ml) and water (0.950 ml), and the mixture was cooled to 0° C. 1,3-Dichloro-5,5-dimethylimidazolidine-2,4-dione (3.58 g, 18.17 mmol) was added in portions and the reaction was stirred in the ice bath for 5 minutes until complete conversion to the sulfonyl chloride (reaction went from heterogeneous yellow mixture to yellow solution upon addition). With the solution at 0° C., 2,3,4,5,6-pentafluorophenol (2.68 g, 14.54 mmol) was added, followed by TEA (6.75 ml, 48.5 mmol), and the reaction was allowed to warm to RT for 20 min. Water was added and the organics were extracted with DCM (×3), followed by drying via phase separator. The organics were then concentrated in vacuo and purified via MPLC eluting with 0-100% ethyl acetate in heptanes (with 10% DCM additive) to yield perfluorophenyl 1-(5-bromo-2-methoxyphenyl)-2-oxo-1,2-dihydroquinoline-6-sulfonate (5.92 g, 10.27 mmol, 85% yield) as a white solid. MS (ESI, pos. ion) m/z: [M+1] 576.0
