[CH:1]([C:3]1[C:11]2[C:6](=[CH:7][C:8]([C:12]([O:14][CH3:15])=[O:13])=[CH:9][CH:10]=2)[NH:5][CH:4]=1)=O.C1(C)C=CC(S(O)(=O)=O)=CC=1.C([BH3-])#N.[Na+].O>CN(C)C=O.S1(CCCC1)(=O)=O>[CH3:1][C:3]1[C:11]2[C:6](=[CH:7][C:8]([C:12]([O:14][CH3:15])=[O:13])=[CH:9][CH:10]=2)[NH:5][CH:4]=1
A mixture of methyl 3-formyl-1 H-indole-6-carboxylate (12.0 g), p-toluenesulphonic acid (2.0 g) and p-toluenesulphonylhydrazide (13.0 g) in a mixture of dimethylformamide (100 ml) and sulpholane (50 ml) was heated at 100° C. for 15 minutes and then cooled to room temperature. The mixture was treated with sodium cyanoborohydride (15.0 g, 5 g portions after 10 minute intervals), then heated at 100° C. for 2 hours. After cooling to ambient temperature the reaction mixture was treated with ice water (500 ml) giving a white precipitate. Water (1000 ml) was added and the mixture stirred for 30 minutes then filtered. The off-white solid was washed with warm water then azeotroped with toluene to yield the title compound (10.2 g) as a white solid.
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