Ionic-Liquid-Supported Recyclable Hypervalent Iodine III Reagents

Various primary and secondary alcohols can be oxidized to aldehydes and ketones with the ion-supported [bis(acyloxy)iodo]arene 99 in the ionic liquid [emim]+[BF4] (l-ethyl-3-methylimidazolium tetrafluorobo-rate) in the presence of bromide anion [94], or in water in the presence of ion-supported TEMPO [97]. Under similar conditions reagent 99 can be used for mild, efficient, highly selective and environmentally friendly oxidation of aliphatic and aromatic sulfides to sulfoxides in excellent yields [98]. This reaction is compatible with hydroxyl, nitrile, methoxy, carbon-carbon double bonds and ester functionalities. The analogous pyrrolidinium-derived ion-supported [bis(acyloxy)iodo]arenes are efficient oxidants of alcohols to carbonyl compounds in the presence of TEMPO [99]. 

PhI(OH)OTs, probably due to the presence of the electron-withdrawing ester group on the benzene ring of reagent 101. 

4 Magnetic Nanoparticle-Supported Recyclable Hypervalent lodine(III) Reagent 

The most important and practically useful hypervalent iodine(V) reagents, IBX and DMP, have a serious disadvantage with respect to the principles of green chemistry since they are normally used as the non-recyclable, stoichiometric reagents. In the only available report, it has been shown that IBX can be recovered in a low yield (about 50%) after reaction with alcohols in ethyl acetate [108], 

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