N[C:2]1[CH:10]=[C:9]([C:11]([O:13][CH3:14])=[O:12])[CH:8]=[C:7]2[C:3]=1[CH:4]=[CH:5][NH:6]2.Cl.N([O-])=O.[Na+].[I-:20].[Na+]>O>[I:20][C:2]1[CH:10]=[C:9]([C:11]([O:13][CH3:14])=[O:12])[CH:8]=[C:7]2[C:3]=1[CH:4]=[CH:5][NH:6]2
To a mixture of methyl 4-amino-1H-indole-6-carboxylate (Example SP-216, step 3) (3.2 g) in water (50 mL) was added concentrated hydrochloric acid (5 mL). The mixture was chilled to below 5° C. with the addition of ice. To this was added sodium nitrite (1.16 g) dissolved in water (10 mL). The mixture was stirred chilled for 1 h followed by addition of sodium iodide (3 g) in water (20 mL). The mixture was stirred for 30 minutes, filtered and the solids collected by filtration were washed with water and dried at 50° C. The solids turned black and gas evolved rapidly upon drying. Column chromatography on silica gel (200 mL) using 20% hexanes in CH2Cl2 as eluent to give 0.82 g of the title compound: 1H NMR (CDCl3) δ 3.94, 6.55, 7.43, 8.14, 8.22, 8.62.
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