Phenyl chloroformate (0.5 mL, 3.99 mmol) was added to a stirred solution of N-(3-amino-5-(tert-butyl)-2-methoxyphenyl)methanesulfonamide (see, for example, Cirillo, P. F. et al., WO 2002/083628, 24 Oct. 2002; 1 g, 3.67 mmol) and NaHCO3 (620 mg, 7.38 mmol) in THF (10 mL) and DCM (10 mL). The mixture was stirred for 2 h then water (20 mL) was added. The organic layer was separated, dried (MgSO4), filtered and evaporated to furnish a brown foam, which was stirred in cyclohexane (20 mL) to afford the sub-title compound (1.4 g) as a colourless solid.
