Potassium Carbonate → 2,5-Dichloropyridine-4-carbonitrile

To 100 ml of acetonitrile was added 24.5 g of POCl3, followed by 27.1 g of 2,5-dichloro-4-pyridinecarboxaldehyde oxime (prepared as described in Example 4). The reaction mixture was heated at reflux temperature for 1 hour, then cooled and poured onto 300 g of ice. The pH of the mixture was adjusted to about pH 6 with K2CO3 and filtered. The filtrate was extracted with 100 ml of CH2Cl2. The filter cake and the CH2Cl2 solution were combined, diluted with equal volumes of hexane, treated with charcoal, dried, and concentrated. The residue was purified by distillation on a Kugelrohr distillation apparatus (boiling point 80° C. at 0.2 mm pressure) to give 19.0 g (77%) of the desired 2,5-dichloro-4-pyridinecarbonitrile as a white solid, m.p. 58°-60° C.