[CH3:1][C:2]([CH3:4])=O.S(=O)(=O)(O)O.[Br:10][C:11]1[CH:17]=[C:16]([CH3:18])[C:15]([CH3:19])=[CH:14][C:12]=1[NH2:13].[BH4-].[Na+]>O1CCCC1>[Br:10][C:11]1[CH:17]=[C:16]([CH3:18])[C:15]([CH3:19])=[CH:14][C:12]=1[NH:13][CH:2]([CH3:4])[CH3:1]A solution of acetone (5.60 mL, 76.3 mmol) and aqueous 4 M sulfuric acid (5.20 mL, 20.8 mmol) in tetrahydrofuran (15 mL) was added dropwise to a stirred solution of 2-bromo-4,5-dimethylaniline 1-8 (13.9 g, 69.3 mmol) in tetrahydrofuran (40 mL) at approximately 0° C. Sodium borohydride (2.62 g, 69.3 mmol) was added cautiously and the resulting mixture allowed to warm to ambient temperature. After 30 min, the reaction was quenched by the careful sequential addition of water (25 mL) and sodium hydroxide pellets (until strongly alkaline). The reaction mixture was extracted with tert-butyl methyl ether (150 mL) and the organic phase was washed with brine, dried (sodium sulfate) and concentrated in vacuo to give a crude residue. Purification of the crude residue by flash chromatography over silica gel (gradient elution; 0%-20% ethyl acetate/hexanes as eluent) afforded 1-9 as a clear, pale orange oil.
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