11 - Reagents of Iodine(V)

Abstract

This chapter explores the reagents of iodine(V). Among iodine(V) compounds very few have been used as reagents. These include iodylbenzene (formerly named iodoxybenzene) and some substituted iodylarenes, 2- iodylbenzoic acid (which is actually cyclic) and its triacetoxy derivative, better known as Dess-Martin reagent. The powerful oxidizing character of iodine(V) is not amply manifested in iodylarenes, the synthetic applications of which are limited. This is partly because of their polymeric nature, which makes them insoluble in most ordinary solvents, with the exception of water. Nevertheless, iodylbenzene and also 3-iodylbenzoic acid in the presence of catalytic amounts of other reagents can be of considerable synthetic utility. A fruitful area of application was the efficient dehydrogenation of steroidal 3- ketones to 1,4-dien-3-ones using benzeneseleninic anhydride, (PhSeO)20, generated in situ by oxygen atom transfer from iodylbenzene to catalytic amounts of diphenyl diselenide. The use of 3-iodylbenzoic acid instead of iodylbenzene has the advantage of avoiding chromatographic separation, allowing the recovery of both reagents. Iodylbenzene in hot nitrobenzene affects some oxidations mimicking its isoelectronic ozone. Among them, the most interesting oxidation is with pyrene, which is converted into a mixture of three isomeric pyrenequinones.