[Br:1][C:2]1[CH:3]=[C:4]2[C:10]([CH3:11])=[CH:9][N:8]([S:12]([C:15]3[CH:20]=[CH:19][C:18](Br)=[CH:17][CH:16]=3)(=[O:14])=[O:13])[C:5]2=[N:6][CH:7]=1.[Li+].[CH3:23]C([N-]C(C)C)C.CI.[Na+].[Cl-]>C1COCC1.CCOC(C)=O>[Br:1][C:2]1[CH:3]=[C:4]2[C:10]([CH3:11])=[C:9]([CH3:23])[N:8]([S:12]([C:15]3[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=3)(=[O:14])=[O:13])[C:5]2=[N:6][CH:7]=1
To a suspension of 5-bromo-1-(4-bromophenylsulfonyl)-3-methyl-1H-pyrrolo[2,3-b]pyridine (B-6-2) (0.9 g, 2.56 mmol) in THF (20 mL) was added dropwise LDA (15 mL, 0.2 M in THF) at −40° C. The mixture was stirred at −10˜−20° C. for 0.5 hour. Methyl iodide (0.55 g 3.84 mmol) was added dropwise at −40˜−30° C. The reaction was stirred at room temperature overnight. LC-MS showed that the reaction was complete. Saturated aqueous NaCl (10 mL) and EtOAc (10 mL) were added into the mixture. The organic layer was separated, dried over anhydrous Na2SO4 and concentrated to give 5-bromo-2,3-dimethyl-1-(phenylsulfonyl)-1H-pyrrolo[2,3-b]pyridine (B-6-3) (0.9 g, 96.3%, containing some starting material (B-6-2) as a light yellow solid.
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