To a solution of tert-butyl 1,3-thiazol-4-ylcarbamate (Preparation 72, 28.94 g, 144.55 mmol) in anhydrous tetrahydrofuran (600 ml), cooled to −70° C., under nitrogen was added lithium 1,1,1,3,3,3-hexamethyldisilazan-2-ide (1 M in tetrahydrofuran, 144.55 ml, 144.55 mmol) dropwise. The reaction mixture was warmed to room temperature and stirred for 1 hour before cooling −70° C. 2,4,5-trifluoro benzenesulfonyl chloride (40 g, 173.46 mmol) in tetrahydrofuran (80 ml) was added dropwise and then the reaction mixture was slowly warmed to room temperature and stirred for 2 hours. The reaction mixture was quenched with saturated aqueous ammonium chloride solution and extracted with ethyl acetate. Organic layer was washed with water and saturated aqueous sodium chloride solution before concentrating in vacuo. The crude residue was purified by column chromatography eluting with ethyl acetate:hexane (gradient 1:19 to 3:17, by volume) to afford the title compound as white solid, 37 g, 64% yield.
