[N+:1]([C:4]1[CH:5]=[C:6]2[C:10](=[CH:11][CH:12]=1)[NH:9][C:8]([C:13](OCC)=[O:14])=[CH:7]2)([O-:3])=[O:2].[OH-].[K+].C(N1C=CN=C1)(N1C=CN=C1)=O.[BH4-].[Na+]>CO.O>[N+:1]([C:4]1[CH:5]=[C:6]2[C:10](=[CH:11][CH:12]=1)[NH:9][C:8]([CH2:13][OH:14])=[CH:7]2)([O-:3])=[O:2]
To a solution of ethyl 5-nitro-1H-indole-2-carboxylate (9.8 g, 42.0 mmol) in methanol (300 mL) was added a solution of 2 M potassium hydroxide (31 mL, 63.0 mmol). The reaction mixture was heated at reflux for 2 h and then the hot solution was filtered, poured onto ice, and acidified. The resultant fine pale brown precipitate was collected by filtration and dried. The crude acid was dissolved in tetrahydrofuran (250 mL) and stirred with 1,1′-carbonyldiimidazole (10.2 g, 63.0 mmol) with gentle warming for 2 h. Water (100 mL) was added and then solid sodium borohydride (7.9 g, 0.21 mol) was added portionwise over 30 min, the reaction mixture was stirred for a further 40 min and then it was quenched with 1 M hydrochloric acid. The tetrahydrofuran was removed at reduced pressure and the residue was dissolved in ethyl acetate, washed, dried, and concentrated to give (5-nitro-1H-indol-2-yl)methanol (903). This material was used without purification in the next step.
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