A convenient procedure for the preparation of a-iodo ketones by oxidative iodination of ketones using iodine and m-iodosylbenzoic acid as a recyclable hypervalent iodine oxidant is reported. Various ketones and b-dicarbonyl compounds can be iodinated by this reagent system under mild conditions affording the respective a-iodo-substituted carbonyl compounds in excellent yields. The final products of iodination are conveniently separated from byproducts by simple treatment with anionic exchange resin Amberlite IRA 900 HCO 3 -and are isolated with good purity after evaporation of the solvent. The reduced form of the hypervalent iodine oxidant, m-iodobenzoic acid, can be recovered in 91-95% yield from the Amberlite resin by treatment with aqueous hydrochloric acid followed by extraction with ethyl acetate.Hypervalent iodine reagents have emerged as the reagent of choice for various synthetically useful oxidative transformations. 1 The most widely used reagents, (diacetoxyiodo)benzene, [hydroxy(tosyloxy)iodo]benzene, and iodosylbenzene, are based on the oxidized form of iodobenzene, and the reactions of these reagents with organic substrates lead to iodobenzene as the byproduct, which is difficult to recover and reuse because of its high volatility and solubility in organic solvents. Numerous research groups have tried to improve iodobenzene-based hypervalent iodine reagents by developing polymer-supported analogues, such as, poly(diacetoxyiodo)styrene. 2 Despite the utility of polymer-supported reagents, they still have several drawbacks. These reagents require multistep preparation, they have lower reactivity compared to the corresponding monomeric analogues, and, moreover, the repeated use of these polymers leads to significant degradation due to benzylic oxidation of the polystyrene chain.Recently, we have found that m-iodosylbenzoic acid 3a,b and its derivatives 3c,d are efficient oxidizing reagents whose reduced form, m-iodobenzoic acid, can be easily recovered from the reaction mixture by treatment with anionic exchange resin or by addition of NaHCO 3 . 3 In the present study, we wish to report the use of m-iodosylbenzoic acid as a convenient recyclable oxidant for the synthesis of a-iodo ketones, which are important building blocks in organic synthesis. 4 Previously reported methods for the preparation of a-iodo ketones commonly employ oxidative iodination of carbonyl compounds using such inconvenient and environmentally harmful reagents as selenium dioxide, 5a mercury(II) chloride, 5b or cerium(IV) ammonium nitrate. 5c We have found that m-iodosylbenzoic acid (1) (which actually has a polymeric structure) 6 is an excellent oxidizing reagent in the oxidative iodination of ketones 3 whose reduced form, m-iodobenzoic acid (2), can be removed at the end of the reaction by treatment with anionic exchange resin Amberlite IRA 900 HCO 3 -5 producing pure a-iodo ketones 4 (Scheme 1).Scheme 1 Oxidative iodination of ketones using m-iodosylbenzoic acid (1) The results for the iodination of various enolizable ketones a...

Potassium 4-iodylbenzenesulfonate (PIBS) is a thermally stable and water soluble hypervalent iodine oxidant particularly useful as a recyclable reagent for oxidative iodination of alkenes, alkynes and ketones. This reagent can be effectively recovered from the reaction mixture by treatment of the aqueous layer with Oxone at 60 o C followed by filtration of the precipitate.

The selective preparation of 2-iodoxybenzenesulfonic acid (IBS, as potassium or sodium salts) by oxidation of sodium 2-iodobenzenesulfonate with Oxone or sodium periodate in water is reported. The single crystal X-ray diffraction analysis reveals a complex polymeric structure consisting of three units of IBS as potassium salt and one unit of 2-iodoxybenzenesulfonic acid linked together by relatively strong I=O···I intermolecular interactions. Furthermore, a new method for the preparation of the reduced form of IBS, 2-iodosylbenzenesulfonic acid, by using periodic acid as an oxidant, has been developed. It has been demonstrated that the oxidation of free 2-iodobenzenesulfonic acid under acidic conditions affords an iodine(III) heterocycle (2-iodosylbenzenesulfonic acid), while the oxidation of sodium 2-iodobenzenesulfonate in neutral aqueous solution gives the iodine(V) products.

A facile metal‐free [2,3]‐sigmatropic rearrangement reaction of allyl sulfides via N‐sulfilimine intermediates has been developed. Treatment of allyl sulfides with imino‐λ3‐iodanes in the presence of a catalytic amount of elemental iodine allowed the reaction to proceed under mild conditions and gave the corresponding N‐allylsulfenamide compounds in moderate to good yields. Several N‐allylsulfenamide structures have been confirmed by single‐crystal X‐ray crystallography. The reaction initially involves the sulfonylimino group transfer reaction between imino‐λ3‐iodane and the sulfur atom, resulting in the formation of N‐sulfilimine species, followed by [2,3]‐sigmatropic rearrangement to form the N‐allylsulfenamide.

Synthesis of α-Iodo Ketones by Oxidative Iodination of Ketones. -The hypervalent iodine oxidant, consisting of m-iodosylbenzoic acid and iodine, iodinates various enolizable ketones and β-dicarbonyl compounds under mild conditions providing the corresponding α-iodo-substituted carbonyl compounds in good to excellent yields. The final products are separated from by-products by treatment with an anionic exchange resin and are isolated with good purity after evaporation of the solvent. The reduced form of iodosylbenzoic acid, m-iodobenzoic acid, is recovered in 91-95% yield from the resin by treatment with hydrochloric acid, followed by extraction. -(YUSUBOV*, M. S.; YUSUBOVA, R. Y.; FUNK, T. V.; CHI, K.-W.; KIRSCHNING, A.; ZHDANKIN, V. V.; Synthesis 2010, 21, 3681-3685, http://dx.doi.org/10.1055/s-0030-1258223 ; Sib. State Med. Univ., Tomsk 634050, Russia; Eng.) -H. Hoennerscheid 09-039