[CH3:1][O:2][C:3]1[C:4]([NH2:15])=[CH:5][C:6]([C:9]2[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=2)=[N:7][CH:8]=1.[I:16]([O-])(=O)=O.[K+].[OH-].[Na+]>[Cl-].[Na+].O>[I:16][C:5]1[C:6]([C:9]2[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=2)=[N:7][CH:8]=[C:3]([O:2][CH3:1])[C:4]=1[NH2:15]To an ice-cooled stirred suspension of 2.70 g (6.20 mmol) 5-methoxy-2-phenyl-pyridin-4-ylamine in 3 ml distilled water was added dropwise 3 ml concentrated sulfuric acid and the mixture was then warmed to 100° C. 1.30 g (6.07 mmol) potassium iodate was added after 3 h, a further 1.30 g (6.07 mmol) potassium iodate was added after an additional 3 h, and finally a further 0.75 g (3.50 mmol) potassium iodate was added after an additional 3 h. Stirred was continued for a further 2.5 h at 100° C., and then the mixture was allowed to cool to room temperature on standing overnight. The mixture was then diluted with saturated brine, made basic by addition of 30% aq. sodium hydroxide solution, and extracted three times with tetrahydrofuran. The combined organic phases were dried over sodium sulfate and concentrated in vacuo. Flash chromatography (ethyl acetate/heptane) afforded 1.60 g (79%) 3-iodo-5-methoxy-2-phenyl-pyridin-4-ylamine as an orange oil which crystallized on standing. ES-MS m/e (%): 327 (M+H+, 100).
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