General procedure for the synthesis of 2-bromo-5-(bromomethyl)pyridine from 2-bromo-5-methylpyridine:
1. dissolve 12 g (70 mmol) of 2-bromo-5-methylpyridine in 100 mL of 1,2-dichloroethane.
2. 16 g (91 mmol) of N-bromosuccinimide and 0.40 g (2.4 mmol) of 2,2'-azobis(isobutyronitrile) were added to the above solution.
3. The reaction mixture was stirred at 85 °C for 15 min.
4. Upon completion of the reaction, water was added to the reaction mixture and the organic layer was separated.
5. The organic layer was dried with anhydrous magnesium sulfate and subsequently concentrated under vacuum.
6. The resulting residue was purified by silica gel column chromatography with an eluent ratio of solvent-free hexane:ethyl acetate = 10:1 to 9:1 (v/v).
7. The fraction containing the target compound was collected and concentrated in vacuo to give 15 g of 2-bromo-5-(bromomethyl)pyridine as white powder in 89% yield. 8.
8. The Rf value of the product was 0.63 (n-hexane:ethyl acetate=9:1, v/v).
9. Mass spectrum (CI, m/z): 250, 252, 254 (M++1). 10.
10. 1H-NMR spectrum (CDCl3, δ ppm): 4.42 (s, 2H), 7.49 (d, J=8.3 Hz, 1H), 7.61 (dd, J1=8.3 Hz, J2=2.7 Hz, 1H), 8.39 (d, J=2.7 Hz, 1H).
