Trifluoroacetic acid → 4-Chloro-5-iodo-2-methoxypyridine

To a solution of 4-chloro-5-iodo-pyridin-2-ylamine (64.2 g, 0.25 mol) in methanol (1.1 L) and TFA (93.7 mL, 1.26 mol) was added tert-butyl nitrite (150 mL, 1.26 mol) so as to maintain temperature less than 3° C. The resultant mixture was stirred at RT for 1 h then allowed to warm to RT and stirred for 16 h. The reaction was quenched by the careful addition of water then concentrated in vacuo to ¼ volume. The resultant residue was treated with water (1 L) and the precipitate formed collected by filtration and dried in vacuo at 35° C. to give the title compound (62.3 g, 92%). Contains 16% impurity. 1H NMR 400 MHz (DMSO-d) δ: 8.56 (1 H, s), 7.20 (1 H, s), 3.86 (3 H, s).