To a stirred ice-cooled solution of tert-butyl 1-piperazinecarboxylate (0.88 g, 4.7 mmol), triethylamine (1.3 mL, 9.4 mmol), and 4-dimethylaminopyridine (0.0058 g, 0.047 mmol) in DCM (10 mL) was added 6-chloropyridine-3-sulfonyl chloride (1.0 g, 4.7 mmol) in one portion. The resulting mixture was stirred at 0° C. and gradually warmed up to ambient temperature for 1.5 h. Upon workup, the mixture was directly subjected to combi-flash column chromatography (methanol/DCM) to give compound 360 (1.44 g, 84% yield) as a white solid.
