[CH3:1][O:2][C:3]1[CH:4]=[C:5]2[C:9](=[CH:10][CH:11]=1)[NH:8][CH:7]=[C:6]2[CH:12]=[O:13].[H-].[Na+].[CH3:16]I.O>CN(C)C=O>[CH3:1][O:2][C:3]1[CH:4]=[C:5]2[C:9](=[CH:10][CH:11]=1)[N:8]([CH3:16])[CH:7]=[C:6]2[CH:12]=[O:13]A solution of 5-methoxyindole-3-carboxaldehyde (80 g) in dimethylformamide (1 L) under nitrogen was treated portion-wise with sodium hydride (20.1 g, 60% dispersion in mineral oil) over 15 minutes. After stirring at ambient temperature for 30 minutes the mixture was treated dropwise with methyl iodide (31.3 mL) over 10 minutes and stirring was then continued for a further 2 hours. The reaction mixture was poured cautiously into water then extracted with ethyl acetate. The organic phase was washed with water, then dried over sodium sulfate and then evaporated. The residue was triturated with pentane to give the title compound (76 g) as a pale brown solid, m.p. 133-134° C. 1H NMR [(CD3)2SO]: δ 9.86 (1H, s); 8.20 (1H, s); 7.60 (1H, d, J=2.6 Hz); 7.50 (1H, d, J=8.9 Hz); 6.96 (1H, dd, J=8.9 and 2.6 Hz); 3.86 and 3.80 (6H, s).
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