Iodine V Compounds

Oxidation by the Dess-Martin Reagent. Another reagent that has become important for laboratory synthesis is known as the Dess-Martin reagent,28 which is a hypervalent iodine(V) compound.29 The reagent is used in inert solvents such as chloroform or acetonitrile and gives rapid oxidation of primary and secondary alcohols. The by-product, o-iodosobenzoic acid, can be extracted with base and recycled. 

Recently it was found that iodine(v) compounds like 2-iodoxybenzoic acid (IBX) 7 can be used to affect selective oxidations at carbon atoms adjacent to aromatic systems. The mechanism of this transformation is believed to proceed via a SET (Single-Electron-Transfer) process. A postulated mechanism for the oxidation of benzylic positions is outlined in Scheme 32. This oxidation is quite general and proceeds efficiently in fluorobenzene/DMSO mixtures or in DMSO at 80 °C [ 135]. Starting from compounds 70, the corresponding aldehydes 71 can be obtained easily in good yields. 

Among iodine(V) compounds rather 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. 

A popular oxidizing agent that effects rapid oxidation of primary or secondary alcohols to aldehydes or ketones is the Dess-Martin reagent. This is the hypervalent iodine(V) compound 46, prepared from 2-iodoxybenzoic acid 45 (IBX) (6.40). Both IBX and the Dess-Martin reagent are potentially explosive and should be handled with care. 

In the older literature, derivatives of iodine(III) were known under the general name of iodinanes, while compounds of pentavalent iodine were called periodinanes. According to the 1983 lUPAC recommendations Treatment of variable valence in organic nomenclature (lambda convention) [126], these old names were replaced by -iodanes for iodine(III) and -iodanes for iodine(V) compounds. In the lambda nomenclature. 

The five-membered pentavalent iodine heterocycles represent a particularly important class of hypervalent iodine compounds. Cyclic iodine(V) compounds, such as IBX 212 and DMP 213, have found broad practical application as mild and selective reagents for the oxidation of alcohols and some other useful oxidative transformations. Several comprehensive reviews of the chemistry and synthetic applications of IBX and DMP have been published (2011JOC1185, 2006ARK26, 2010T7659, 2011AGE1524, 2001ACE2812). 

Such reactions are also possible in vitro, as several mild oxidizing agents are at hand nowadays. Thus, the Dess-Martin periodinane (DMP) [50] has been proven to be a versatile and powerful reagent for the mild oxidation of alcohols to the corresponding carbonyl compounds. In this way, a series of new iodine(V)-mediated reactions has been developed which go far beyond simple alcohol oxidation [51], Ni-colaou and coworkers have developed an effective DM P-mediated domino polycy-clization reaction for converting simple aryl amides, urethanes and ureas to complex phenoxazine-containing polycycles. For example, reaction of the o-hydroxy anilide 7-101 with DMP (2 equiv.) in refluxing benzene under exposure to air led to polycycle 7-103 via 7-102 in a yield of 35 % (Scheme 7.28) [52]. 

It is remarkable that the aromatic iodo-compounds can be converted via addition products with chlorine into organic iodine derivatives containing multivalent iodine (V. Meyer, Willgerodt). 

Kulprathipanja, S., Vora, B.V., and Leet, W.A. (2003) Combination pretreatment/ adsorption for treating a liquid stream contaminated with an iodine-containing compound. U.S. Patent 5,505,935. 

The periodinane (10) may also be prepared from o-iodobenzoic acid by oxidation with potassium bromate and then treatment with acetic anhydride18 (see Expt 6.36 for detailed formulation). It should be noted that the organic derivatives of pentacoordinate iodine(v) are termed periodinanes.18b This compound (the systematic name is l,l,l-triacetoxy-2,l-benzoxiodol-3(3//)-one) has found use as an oxidant of primary alcohols to aldehydes and alicyclic ketones to secondary alcohols it is claimed to have advantages over the chromium-based oxidation reagents. 

The first hypervalent iodine compound, (dichloroiodo)benzene 1, was prepared in 1886 by Willgerodt [9]. Since that time, several new reagents of iodine (III) and iodine (v) have been developed and are now frequently used in oxidative functionalizations. Scheme 1 shows a selection of the most frequently used... 

Organobismuth(III) halides may be prepared by elimination of aryl halide from triarylbismuth(V) dichlorides or dibromides upon heating (equation 4). Presumably, a bis-muth(V) compound is the intermediate when triarylbismuth compounds are treated with iodine or when trialkylbis-muth complexes are treated with chlorine, bromine, or iodine, but the intermediates have not been isolated and organobismuth halides are obtained directly (equation 5). The tris(trifluoromethyl)bismuth behaves like the trialkyl compounds without the observation of a bismuth(V) intermediate. ... 

The intention is not to cover the vast halo-organic chemistry in this context, but only organic polyvalent halogen compounds that are actually limited to derivatives with iodine (I), iodine (III), and iodine (V), though evidence for the divalent L2T radical was obtained by the hemolytic cleavage of I-O bonds during thermolysis of tert-butyl-peroxyiodanes7 ... 

---