The mono-brominated sulfonamide from step 2 (0.194 g, 0.509 mmol) was was dissolved in methanol (2 ml) before potassium thioacetate (0.0639 g, 0.560 mmol) was added as a solid. LC-MS of the resulting yellow solution shows the reaction is complete in minutes. Evaporation of the volatiles leaves a tan residue which was taken up into dichloromethane (4 ml), during which the disulfide of the thioacetic acid was deposited and filtered. The desired thioester could then be recrystallized from dichloromethane/hexanes (0.080 g, 0.214 mmol, 42%). LC-MS (ES+): 376 [MH]+ m/e. 1H-NMR (DMSO): 7.87 (d, 3H), 7.78 (s, 1H), 7.7 (m, 1H), 7.57 (m, 3H), 4.41 (s, 2H), 3.99 (t, 2H), 3.06 (t, 2H), 2.34 (s, 3H)
