12 - Some Further Reagents of Iodine(III)

Abstract

This chapter describes various hypervalent iodine compounds, which have been sporadically used in reactions of synthetic interest. Although they cannot be considered presently as fully fledged reagents, it is possible that in the future they will be further developed. It is hoped that this separate presentation of minor reagents would serve as a source of inspiration for new useful applications. o-Iodosylbenzoic acid is actually cyclic in the crystalline state. [Bis(saccharinyl)iodo]benzene belongs to a category of iodobenzene derivatives, in which two imidyl groups are attached to iodine through nitrogen; its main utility is the transfer of a saccharinyl group to the α-position of enolizable ketones. The reaction of iodosylbenzene with sulfur trioxide at 50°C leads to the formation of two isolable hygroscopic compounds, depending on the stoichiometry of the reactants. When iodosylbenzene is treated with pyridine and trimethylsilyl triflate under strictly anhydrous conditions, at room temperature, the title compound precipitates almost quantitatively. Similar compounds are formed using substituted pyridines, quinoline and N-methyl-imidazole. The main advantage of o-iodosylbenzoic acid is that its use avoids chromatographic separation.