General procedure for the synthesis of 2-bromo-5-trifluoromethoxypyridine: 2-chloro-5-(trifluoromethoxy)pyridine (6, 7.0 g, 35.4 mmol) and bromotrimethylsilane (10.8 g, 9.3 mL, 70.8 mmol, 2 eq.) were dissolved in propionitrile (35 mL) and heated to reflux for 24 hours. The reaction process was monitored by gas chromatography (GC) to confirm 100% conversion. Upon completion of the reaction, the mixture was vacuum distilled to afford pure 2-bromo-5-trifluoromethoxypyridine (31, 7.0 g, 28.7 mmol, 81% yield) as a colorless oil. Boiling point: 63-66°C (14 mbar).
NMR data:
1H NMR (CDCl3, 300 MHz): δ= 8.34 (d, J = 2.8 Hz, 1H), 7.56 (d, J = 8.7 Hz, 1H), 7.45 (dd, J = 8.7, 2.8 Hz, 1H).
19F NMR (CDCl3, 282 MHz): δ= -58.8.
13C NMR (CDCl3, 75 MHz): δ= 145.6, 143.1, 139.2, 131.4, 129.0, 120.1 (q, J = 260 Hz).
Elemental analysis: C6H3BrF3NO (molecular weight 241)
Calculated value (%): C 29.78, H 1.25, N 5.79; measured value: C 29.96, H 1.41, N 5.64.
