[F:1][C:2]1[CH:10]=[C:9]2[C:5]([CH:6]=[CH:7][NH:8]2)=[CH:4][C:3]=1[C:11]([OH:13])=[O:12].[I:14]I.[OH-].[K+].S([O-])(O)=O.[Na+].Cl>CN(C=O)C>[F:1][C:2]1[CH:10]=[C:9]2[C:5]([C:6]([I:14])=[CH:7][NH:8]2)=[CH:4][C:3]=1[C:11]([OH:13])=[O:12]To a solution of 6-fluoro-1H-indole-5-carboxylic acid (2.32 g, 12.95 mmol) in DMF (15 mL) was added iodine (3.45 g, 13.60 mmol) and potassium hydroxide (1.60 g, 28.5 mmol). After stirring 20 min at RT, the reaction mixture was poured into ice water (40 mL) containing sodium hydrogensulfite (1.35 g, 12.95 mmol). The reaction mixture was stirred for 5 min, treated with 2 N HCl to adjust the pH to about pH=6 and filtered. The resulting orange solid was washed with water (2×25 mL) and transferred to a 250 mL round bottomed flask and dried overnight using a lyophilizer to afford 6-fluoro-3-iodo-1H-indole-5-carboxylic acid (3.63 g, 11.90 mmol, 92% yield) as an orange amorphous solid. MS (ESI, pos. ion) m/z: 305.9 (M+H)+.
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