Azobisisobutyronitrile → 3-Bromo-2-(bromomethyl)-6-chloropyridine

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To a stirred solution of 3-bromo-6-chloro-2-methylpyridine (105 g, 509 mmol) in CCl4 (2 L) was added N-bromosuccinimide (95 g, 534 mmol) followed by AIBN (8.35 g, 50.9 mmol). The reaction was brought to reflux for 24 hours and then cooled to r.t., filtered, and concentrated. Purification of the residue by flash chromatography on silica gel with 60% methylene chloride/heptanes afforded semi-pure product. Further purification by SFC on a Chiralpak AD-H column with 20% IPA/CO2 [the conditions of the preparative separation were as follows: column Chiralpak AD-H (2.1×25 cm, 5 μm particle size) (Chiral Technologies, West Chester, Pa., USA); mobile phase 20% 2-propanol/CO2; elution mode isocratic pump-mixed; flow rate 50 mL/min; pressure 100 bar.] gave 3-bromo-2-(bromomethyl)-6-chloropyridine. LCMS=285.7 (M+H)+ 1H NMR (CDCl3, 500 MHz) δ 7.81 (d, J=8.4 Hz, 1H), 7.15 (d, J=8.3 Hz, 1H), 4.63 (s, 2H).

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