Iodination [Synthetic Reagents]

　1,3-Diiodo-5,5’-dimethylhydantoin (DIH) [D3657], which was first reported by Ozazi, is an useful iodinating reagent.¹⁾ DIH has higher reactivity and selectivity than molecular iodine or N-iodosuccinimide (NIS), which are frequently used for iodination reaction. DIH is a pale yellow solid that does not sublime like molecular iodine, and has low toxicity, which makes it easier to handle. In addition, dimethylhydantoin, which is formed after the reaction, can easily be removed by aqueous extraction.
　DIH reacts smoothly at room temperature with aromatic compounds in the presence of sulfuric acid to give the corresponding iodinated aromatic compounds in a high regioselectivity and a high yield. Moreover, even low-activated substances such as nitrobenzene can easily be iodinated by using sulfuric acid.²⁾