30 August 2013 (online)
1,3-Diiodo-5,5-dimethylhydantoin (DIH, C5H6I2N2O2, mp 192–196 °C, CAS: 2232-12-4) is a light brown powder. It has a light iodine odor and is stable when kept dry and at low temperature.
In 1965, Orazi et al. introduced DIH as an efficient reagent for iodination. DIH is a stable compound with a high iodine content. Mechanistic studies suggest that this reagent acts as an I+ donor. Homolytic cleavage could not be detected and no HI is formed. Therefore, additional bases or oxidants are not required!
DIH has a reactivity comparable to that of molecular iodine, but it is more convenient to handle, because this solid reagent does not sublimate. It possesses the same selectivity as N-iodosuccinimide (NIS) and equal or better halogenating ability. With two N–I bonds, DIH can be more economical in direct comparison to NIS. It has been used as an iodizing agent or an oxidizing agent in production processes in the pharmaceutical, food, and agricultural industries.
DIH has been used for chemoselective iododesilylations to obtain nitriles,  for the iodination of aromatic compounds, for the preparation of chroman derivatives, to convert aromatic aldehydes into the corresponding amides, for the sulfonylamidation of alkylbenzenes at the benzylic position, and to obtain oxazolonederivatives, benzothiazine, and tetrahydroquinoline derivatives.
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