Phosphorus oxychloride → 3-Bromo-2,5-dichloropyridine
Reaction equation
[Br:1][C:2]1[C:3](=O)[NH:4][CH:5]=[C:6]([Cl:8])[CH:7]=1.O=P(Cl)(Cl)[Cl:12]>CN(C=O)C>[Br:1][C:2]1[C:3]([Cl:12])=[N:4][CH:5]=[C:6]([Cl:8])[CH:7]=1Participants
4
Reactant 2
Product 1
Reagents, catalysts & solvents 1
Conditions
- Temperature
- 70 °C
Procedure
To a solution of 3-bromo-5-chloropyridin-2-one (84.3 g, 0.404 mol) in DMF (100 mL) was added POCl3 (56.5 mL, 0.61 mol) via dropping funnel over 3 hours at room temperature. The resulting black solution was then heated to 70° C. and allowed to stir for 3 days. After cooling to room temperature, the solution was poured into 1 L of ice/water, filtered, and the solid dried in a vacuum oven to provide 81.76 g (89%) of the desired 3-bromo-2,5-dichloropyridine as an off-white solid, m.p. 39-41° C.: IR(CHCl3) 3867, 3663, 2989, 2734, 1812, 1606, 1547, 1400, 1366, 1230, 1155, 1129, 1074, 1027, 894, 658, 563 cm-1 ; 1H NMR (300 MHz, CDCl3) δ 8.0 (d, 1H, J=2.2 Hz), 8.35 (d, 1H, J=2.2 Hz); 13C NMR (CDCl3) δ 120.43, 130.74, 141.46, 146.64, 148.99; exact mass calculated for C5H2NBrCl2 =224.8748; high resolution mass spec. 224.8764.