Br[CH2:2][C:3](=[O:16])[C:4]([C:7]1[CH:8]=[CH:9][C:10]([F:15])=[C:11]([CH:14]=1)[C:12]#[N:13])([CH3:6])[CH3:5].[N-:17]=[N+:18]=[N-:19].[Na+]>CN(C=O)C.O>[N:17]([CH2:2][C:3](=[O:16])[C:4]([C:7]1[CH:8]=[CH:9][C:10]([F:15])=[C:11]([CH:14]=1)[C:12]#[N:13])([CH3:6])[CH3:5])=[N+:18]=[N-:19]To a stirred solution of 5-(4-bromo-2-methyl-3-oxobutan-2-yl)-2-fluorobenzonitrile (10 g, 35.2 mmol) in DMF (100 mL) at 0° C. was added NaN3 (2.52 g, 38.7 mmol, 1.1 eq) portionwise. After stirring 2 h, the residue was diluted with water and extracted with EtOAc. The combined extracts were washed with brine (100 mL), dried over MgSO4 and evaporated in vacuo. The residue was purified by flash column chromatography (silica, Hex/EtOAc=4:1) to give 5-(4-azido-2-methyl-3-oxobutan-2-yl)-2-fluorobenzonitrile (6.6 g, 2 step overall yield 78%). 1H NMR (400 MHz, CDCl3) δ 7.57-7.55 (m, 1H), 7.50-7.46 (m, 1H), 7.25 (t, J=7.2 Hz, 1H), 3.8 (s, 2H), 1.55 (s, 6H).
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