Dichloromethane → HCID 178526740, compound

3-Nitro-6-trifluoromethyl-pyridine-2,4-diol (5.8 gm, 26 mmol) was heated in phenylphosphonic dichloride (30 mL) at 100° C. for 19 hours. The resulting mixure was then cooled and poured on to ice (60 gm), and then extracted with ethyl acetate (3×50 mL). The combined organic extracts were washed with aqueous sodium hydrogen carbonate solution (10% w/v) until the washings remained basic (pH ˜8). The deep yellow organic layer was then washed with saturated brine, dried over sodium sulphate, filtered and evaporated to give a yellow gum. Trituration of the gum with dichloromethane gave a yellow solid which was filtered off and dried (4.65 gm). The solid was dissolved in water (25 mL) and acidified with 2N hydrochloric acid (7.5 mL) to give a thick white precipitate which was filtered off and washed with water. The precipitate was dissolved in ethyl acetate, dried over sodium sulphate, filtered and evaporated to give the title compound as a white solid (3.75 gm).