To a mixture of N-(3-(5-(4-chlorophenyl)-1H-pyrrolo[2,3-b]pyridine-3-carbonyl)-2,4-difluorophenyl)propane-1-sulfonamide (0.1 g, 0.2 mmol) and Et3N (114 μL, 0.8 mmol) in DMF (0.6 mL) was added a solution of TBAB (132 mg, 0.4 mmol) in DMF (0.2 mL). The reaction was stirred at 10° C. for 30 min, followed by dropwise addition of a solution of chloromethyl ethyl carbonate (34 mg, 0.25 mmol) in DMF (0.2 mL). The mixture was stirred at 10° C. for another 3 h, then diluted with EtOAc (40 mL) and filtered. The filtrate was concentrated in vacuo and the residue was purified by a silica gel column chromatography (PE/EtOAc (v/v)=2/1) to afford the title compound as a white solid (85 mg, 73%). The title compound was characterized by LC-MS and 1H NMR as shown below:
