Esters of 2-Iodoxybenzoic Acid: Hypervalent Iodine Oxidizing Reagents with a Pseudobenziodoxole Structure

Esters of 2-iodoxybenzoic acid (IBX-esters) were prepared by the hypochlorite oxidation of the
corresponding 2-iodobenzoate esters and isolated as chemically stable, microcrystalline products.
These hypervalent iodine compounds are potentially valuable oxidizing reagents belonging to a
new class of pentavalent iodine compounds with a pseudobenziodoxole structure. Methyl 2-iodoxybenzoate can be further converted to the diacetate or a bis(trifluoroacetate) derivative by treatment
with acetic anhydride or trifluoroacetic anhydride, respectively. Single-crystal X-ray diffraction
analysis of methyl 2-[(diacetoxy)iodosyl]benzoate 8a reveals a pseudobenziodoxole structure with
three relatively weak intramolecular I···O interactions. The dimethyl and diisopropyl esters of
2-iodoxyisophthalic acid were prepared by oxidation of the respective iodoarenes with dimethyldioxirane. Single-crystal X-ray diffraction analysis of diisopropyl 2-iodoxyisophthalate 6b showed
intramolecular I···O interaction with the carbonyl oxygen of only one of the two carboxylic groups,
while NMR spectra in solution indicated equivalency of both ester groups. IBX-esters, methyl
2-[(diacetoxy)iodosyl]benzoate, and 2-iodoxyisophthalate esters can oxidize alcohols to the respective
aldehydes or ketones in the presence of trifluoroacetic acid or boron trifluoride etherate. The bis(trifluoroacetate) derivative can oxidize alcohols to carbonyl compounds without acid catalyst.