Preparation of Dess–Martin periodinane—the role of the morphology of 1-hydroxy-1,2-benziodoxol-3(1H )-one 1-oxide precursor

1-Hydroxy-1,2-benziodoxol-3(1H)-one 1-oxide prepared by oxidation of o-iodobenzoic acid with potassium bromate forms either a microcrystalline powder, a macrocrystalline material, or a mixture of both forms. This difference in physical form is the source of the difficulty in reproducibly converting 1-hydroxy-1,2-benziodoxol-3(1H)-one 1-oxide to the corresponding I-triacetoxy derivative. A simple method is given for conversion of crystalline 1-hydroxy-1,2-benziodoxol-3(1H)-one 1-oxide to the more reactive powder form. The microcrystalline powder and macrocrystalline material are characterised by X-ray diffraction.