Treatment of uracil bases and protected nucleosides with iodine monochloride (ICl) gave the corresponding 5-iodouracil products in over 95% purified yields. Analogously facile chlorination was effected with iodobenzene dichloride (PhICl2). Protection of the nucleosides as p-toluyl esters provided reactants that were soluble in organic solvents and crystallized readily in high yields.
