[Br:1][C:2]1[CH:3]=[C:4]2[N:11]([S:12]([C:15]3[CH:21]=[CH:20][C:18]([CH3:19])=[CH:17][CH:16]=3)(=[O:14])=[O:13])[CH:10]=[CH:9][C:5]2=[N+:6]([O-])[CH:7]=1.C[CH2:23][N:24](CC)CC.C[Si](C#N)(C)C>ClCCCl>[Br:1][C:2]1[CH:3]=[C:4]2[N:11]([S:12]([C:15]3[CH:21]=[CH:20][C:18]([CH3:19])=[CH:17][CH:16]=3)(=[O:14])=[O:13])[CH:10]=[CH:9][C:5]2=[N:6][C:7]=1[C:23]#[N:24]To a stirred mixture of 6-bromo-1-tosyl-1H-pyrrolo[3,2-b]pyridine 4-oxide (5.66 g, 15.41 mmol), Et3N (21.5 mL, 154 mmol) and DCE (40 mL) was added trimethylsilyl cyanide (10.33 mL, 77 mmol), and the reaction mixture was stirred at 76° C. for 16 hours. The dark reaction mixture was concentrated in vacuo and purified by silica gel chromatography (1% to 2% MeOH/DCM) to give the title compound as a white solid (3.48 g, 60%). 1H NMR (500 MHz, CDCl3) δ ppm 8.56 (d, 1H, J=1.0 Hz), 7.90 (d, 1H, J=4.0 Hz), 7.79 (d, 2H, J=8.0 Hz), 7.33 (d, 2H, J=8.0 Hz), 6.88 (d, 1H, J=4.0 Hz), 2.41 (s, 3H); ESI-MS m/z [M+H]+ calc'd for C15H10BrN3O2S, 376, 378; found 376, 378. Further elution of the silica gel column with 4% MeOH/DCM gave a second major fraction, which was the tosyl-deprotected product, which was collected to give impure 6-bromo-1H-pyrrolo[3,2-b]pyridine 5-carbonitrile as a brown solid (1.25 g, 36%). ESI-MS m/z [M+H]+ calc'd for C8H4BrN3, 222, 224; found 222, 224.
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