[Cl:1][C:2]1[N:7]=[CH:6][C:5]([CH3:8])=[CH:4][C:3]=1[I:9].[Br:10]N1C(=O)CCC1=O.N(C(C)(C)C#N)=NC(C)(C)C#N>ClC1C=CC=CC=1>[Br:10][CH2:8][C:5]1[CH:6]=[N:7][C:2]([Cl:1])=[C:3]([I:9])[CH:4]=14.60 g (18.15 mmol) of 6-chloro-5-iodo-3-methylpyridine (Setliff et al., J. Chem. Engineering Data (1976), 21(2), 246-7), 3.39 g (19.06 mmol) of N-bromosuccinimide and 0.30 g (1.82 mmol) of 2,2′-azobis(2-methylpropanenitrile) in 500 ml of chlorobenzene are boiled under reflux for about 16 hours. The reaction mixture is washed with saturated aqueous sodium sulphite solution and sodium bicarbonate solution and then dried over sodium sulphate and concentrated under reduced pressure. Column chromatography of the residue on silica gel (silica gel 60-Merck, particle size: 0.04 to 0.063 mm) using the mobile phase mixture ethyl acetate:cyclohexane (1:10) gives 3.86 g (38% of theory) of 3-bromomethyl-6-chloro-5-iodopyridine.
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