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Concentrated sulfuric acid (5 mL), periodate (26 g, 123 mmol) and iodine (62 g, 246 mmol) were sequentially added to a stirred solution of 5-(trifluoromethyl)pyridin-2-amine (100 g, 617 mmol) in acetic acid (1 L) under argon protection and at room temperature. The reaction mixture was heated to 80 °C and stirred continuously for 16 hours. The progress of the reaction was monitored by thin layer chromatography (TLC) and after confirming the complete consumption of the raw materials, the reaction mixture was cooled to 0 °C and alkalized with sodium hydroxide solution (200 mL) to precipitate the solid product. The solid was collected by filtration and concentrated under vacuum to afford the target compound 3-iodo-5-(trifluoromethyl)pyridin-2-amine (120 g, 67% yield) as an off-white solid. The product was characterized by 1H NMR (DMSO-d6, 500 MHz): δ 8.27 (s, 1H), 8.16 (s, 1H), 6.87 (brs, 2H); TLC conditions: 10% ethyl acetate/hexane (Rf 0.4).

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