Br[CH2:2][C:3](=[O:18])[C:4]([C:7]1[CH:12]=[CH:11][C:10]([S:13]([NH2:16])(=[O:15])=[O:14])=[C:9]([Cl:17])[CH:8]=1)([CH3:6])[CH3:5].[N-:19]=[N+:20]=[N-:21].[Na+]>CN(C=O)C.O>[N:19]([CH2:2][C:3](=[O:18])[C:4]([C:7]1[CH:12]=[CH:11][C:10]([S:13]([NH2:16])(=[O:15])=[O:14])=[C:9]([Cl:17])[CH:8]=1)([CH3:6])[CH3:5])=[N+:20]=[N-:21]To a solution of 4-(4-bromo-2-methyl-3-oxobutan-2-yl)-2-chlorobenzenesulfonamide (11.3 g, 31.8 mmol) in DMF (50 mL) was added NaN3 (3.1 g, 47.8 mmol, 1.5 eq) at 0° C. After stirring 2 h, the residue was diluted with water and extracted with EtOAc. The combined extracts were washed with 1M HCl and water successively, dried over MgSO4, filtered and evaporated. The residue was purified by chromatography (Hex/EtOAc=4:1 to 2:1) to give 4-(4-azido-2-methyl-3-oxobutan-2-yl)-2-chlorobenzenesulfonamide (8.0 g, 79% yield) as yellow sticky oil. 1H NMR (400 MHz, CDCl3) δ 8.11 (d, J=8.4 Hz, 1H), 7.43 (s, 1H), 7.29 (d, J=2.2 Hz, 1H), 5.12 (s, 2H), 4.11 (s, 2H), 1.58 (s, 6H).
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