7 - Hydroxy(tosyloxy)iodo]benzene and its Analogues

Abstract

This chapter discusses [Hydroxy(tosyloxy)iodo] benzene and its analogues. [Hydroxy(tosyloxy)iodo] benzene, PhI(OH)OTs (hereafter abbreviated HTI), is often called Koser's reagent. It is a readily available stable compound, which is gaining popularity in diverse fields. Although in several reactions it behaves similarly to other hypervalent iodine reagents, there are many instances, in which it shows a different reactivity or improved features. Its uses refer mostly to oxidations of various types and tosyloxylations (or oxysulphonylations with analogues bearing various RSO3 groups). Some related compounds having an organosulphonyloxy group are also discussed in this chapter, including Zefirov's reagent, PhI(OTf)OI(OTf)Ph, and the product of its further transformation. Alkynes upon heating with HTI in methanol undergo an oxidative rearrangement to methyl carboxylates, which are hydrolyzed in situ to afford carboxylic acids. Cyclooctene was unreactive towards HTI, but 1-methyl-4-cycloocten-1-ol afforded an almost 1:1 mixture of two tosyloxy ethers (55%); the regioselectivity for the formation of the two skeletons was low, but the addition was highly trans-selective. The use of silyl enol ethers permitted the preparation of α-tosyloxy ketones with acid-sensitive or oxidizable ring systems, such as furan and pyridine.