Azobisisobutyronitrile → 2-Chloro-5-(chloromethyl)-3-fluoropyridine

1.00 g (6.87 mmol) of 6-chloro-5-fluoro-3-methylpyridine (cf. F. L. Setliff, Organic Preparations and Procedures International 1971, 3, 217-222), 1.01 g (7.56 mmol) of N-chlorosuccinimide and 0.11 g (0.69 mmol) of 2,2′-azobis(2-methylpropanenitrile) in 100 ml of chlorobenzene are boiled under reflux for 2 days. After about 16 and 32 hours, in each case a further 1.01 g (7.56 mmol) of N-chlorosuccinimide and 0.11 g (0.69 mmol) of 2,2′-azobis(2-methylpropanenitrile) are added. 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 (1:20) gives 0.65 g (53% of theory) 6-chloro-3-chloromethyl-5-fluoropyridine.