2-n-Butyl-5-hydroxymethyl-4-iodoimidazole → 2-Butyl-5-formyl-4-iodo-imidazole

A stirred mixture of 174.1 g (0.62 mol) of 2-n-butyl-5-hydroxymethyl-4-iodoimidazole and 360 g (4.14 mol) of manganese dioxide in 3 L of dichloromethane was refluxed for 24 hr using a trap to remove water. The hot reaction mixture was filtered through a Celite® pad which was then washed with 4.5 L of boiling methylene chloride. The combined filtrates were concentrated to dryness. The residue was dissolved twice in 150 ml of methanol and each time the solution was concentrated to dryness. The residue was dissolved in 130 ml of methanol and chilled. After crystallization stopped, 700 ml of water was added slowly. The mixture was chilled, and the solid was collected by filtration, washed with water and dried to give 145.2 g (84%) of product; mp 104°-105° C.