Chlorine → 2,6-Dichloropyridin-3-ol

Temperatur

20 °C

100 g (0.77 mole) of 2-chloro-3-pyridinol (I) was dissolved in 350 ml of dimethylformamide. 70 ml of chlorine (measured at -80°; 0.93 mole) was introduced in the course of 1.5 hours into the stirred solution at 0°. The reaction mixture was then stirred for 1.5 hours at 20° C. and subsequently concentrated in a rotary evaporator (bath: 50°; 10 torr). 400 ml of water and 100 ml of ether were added to the residue; the two phases were separated and the aqueous phase was extracted 5 times with 100 ml of ether each time. The combined ether phases were washed with water and dried. The solvent was removed in vacuo; the semisolid residue was stirred with 1.6 liters of water, and the resulting suspension was adjusted to pH 3. The suspension was heated to boiling, and after a few minutes the solution was decanted from an oily residue. The solution was purified with active charcoal, and the yellow product obtained on cooling was recrystallised from water; m.p. 136°-138° C.; yield 42 g.