Lithium Hexamethyldisilazide → N-(2,4-Dimethoxybenzyl)-2,4,5-trifluoro-N-(1,2,4-thiadiazol-5-yl)benzenesulfonamide

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To a solution of (N-(2,4-dimethoxybenzyl)-1,2,4-thiadiazol-5-amine (Preparation 14, 13 g, 51.73 mmol) in dry tetrahydrofuran (150 ml) at −70° C. under argon atmosphere was added 1 M lithium 1,1,1,3,3,3-hexamethyldisilazan-2-ide in tetrahydrofuran (56.9 ml, 56.9 mmol) dropwise. The reaction mixture was allowed to warm up to room temperature and stirred for 1 h. It was again cooled to −70° C. and a tetrahydrofuran (50 ml) solution of 2,4,5-trifluorobenzenesulfonyl chloride (11.9 g, 51.73 mmol) was added dropwise to it at this temperature. After complete addition, reaction mixture was gradually allowed to warm up to room temperature and stirred for 1 hour. The reaction mixture was quenched with saturated aqueous ammonium chloride solution and extracted with ethyl acetate. The organic layer was washed with water and saturated aqueous sodium chloride solution. Crude product was purified over 100-200 silica gel using 5-15% v/v ethyl acetate in hexane to give 17 g (75%) of the title compound as a white solid.

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