N-bromobutanimide → 5-(Bromomethyl)-2,4-dichloropyridine

2,4-dichloro-5-methylpyridine (13.64 g, 82.50 mmol), N-bromosuccinimide (15.42 g, 86.63 mmol) were dissolved in chlorobenzene (300 mL). 2,2′-azobis(isobutyronitrile) (1.355 g, 8.250 mmol) in chlorobenzene (160 mL) was added slowly in two times: first approximately a third of the total amount at room temperature, then the rest dropwise (over 40 min) at 132° C. The reaction mixture was stirred at 132° C. for 16 h. The reaction mixture was washed with a saturated sodium sulfite solution (organic layer at the top), then with a saturated sodium bicarbonate solution (organic layer at the bottom). The organic phase was dried with sodium sulfate, then filtered and concentrated. A crude material was obtained as a yellow oil (24.9 g). It was purified by flash chromatography (Heptanes/AcOEt gradient from 0 to 10% AcOEt) to yield pale yellow crystals (13.84 g).