Polyvalent iodine

It is convenient to describe here certain polyvalent iodine compounds, formed by such substances as iodobenzene and p-iodotoluene. lodobenzeue in chloroform solution reacts readily with chlorine to form iodobenzene dlchlorlde (phenyl iododichloride) (I) ... 

The oxidation of acetylthiourea and phenylthiourea to afford the corresponding 1,2,4-thiadiazoles has been reported using [bis(acyloxy)iodo]arenes as the oxidants. The proposed mechanism involves the formation of a polyvalent iodine compound 74. After the elimination of iodobenzene, the 1,6-dip he nyl-dithioformamidine 75 is formed, which is set up to undergo a further oxidation to give the bis 3,5-diamino-l,2,4-thiadiazole 76 (Scheme 7) <2003T7521>. 

Xenon difluoride reacts with alkyl iodides at room temperature to give organic derivatives of polyvalent iodine. When an excess of iodomcthane (7) is treated with xenon difluoride it produces a stable solution of methyliodine difluoride in quantitative yield, the use of hydrogen fluoride as a catalyst allows a substantial amount of product to be obtained, while isopropyl iodide decomposes under the action of the reagent.16-21... 

Iodosobenzene bistrifluoroacetate is a versatile mild oxidant that has been used to oxidize a broad range of organic compounds, such as alkenes, alkynes, carbonyl compounds, and alcohols Its application in organic synthesis has been summarized m several recent reviews devoted to polyvalent iodine compounds [63, 64, 65]... 

Methods leading to polyvalent iodine compounds (Expts 6.31 to 6.36). 

Two polyvalent iodine compounds arising from o-iodobenzoic acid have been found to be useful synthetic reagents. Thus oxidation of the iodo acid (7) with potassium persulphate, followed by the addition of benzene and treatment with potassium iodide gives the iodonium iodide (8) which is converted into diphenyliodonium-2-carboxylate [DPIC (9)] with aqueous alkali (Expt 6.35).16... 

A. Varvoglis Polyvalent iodine compounds in organic synthesis [9]... 

E. B. Merkushev Organic compounds of polyvalent iodine. Derivatives of iodosobenzene [13]... 

The purpose of present review is to summarize the application of different classes of iodine(III) compounds in carbon-carbon bond forming reactions. The first two sections of the review (Sects. 2 and 3) discuss the oxidative transformations induced by [bis(acyloxy)iodo] arenes, while Sects. 4 through 9 summarize the reactions of iodonium salts and ylides. A number of previous reviews and books on the chemistry of polyvalent iodine discuss the C-C bond forming reactions [1 -10]. Most notable is the 1990 review by Moriarty and Vaid devoted to carbon-carbon bond formation via hypervalent iodine oxidation [1]. In particular, this review covers earlier literature on cationic carbocyclizations, allyla-tion of aromatic compounds, coupling of /1-dicarbonyl compounds, and some other reactions of hypervalent iodine reagents. In the present review the emphasis is placed on the post 1990s literature. 

Aryl-, as well as heteroaryliodonium salts, belong to the most common, stable, and well investigated class of polyvalent iodine compounds. The preparation and chemistry of aryliodonium salts was extensively covered in several reviews [5,7,9,10]. Diaryliodonium salts have found synthetic application as arylating reagents in reactions with various organic substrates. 

It can be anticipated that these areas of synthetic application will continue to attract significant research activity in the future. The increasing use of the transition metal-mediated coupling reactions of iodonium salts may add a new dimension to the field of polyvalent iodine chemistry. 

We hope and anticipate that this review will provide added stimulus for the further development of the chemistry of polyvalent iodine compounds. 

Six structural types of polyvalent iodine species are commonly encountered, as shown below ... 

The most important structural features of polyvalent iodine compounds may be summarized as follows ... 

Full details for an improved method for preparation of these polyvalent iodine compounds are available.1 The method is similar to that used to prepare vinylio-donium tetrafluoroborates (13,151), and yields are 60-89%. 

Oxygenated polyvalent iodine compounds are also useful halogenating agents. oc-Iodoepoxides are prepared by reaction of iodosylbenzene diacetate (IBDA) with allyl alcohols (equation 116)832. Iodosylbenzene, activated by triflic acid, adds to acetylenes (equation 1 17)833. PhI(OAc)2 simultaneously iodinates and etherifies phenols (equation 118)834. 

In view of the propensity of alkynyliodonium ions for Michael reactions with a wide range of nucleophiles, such displacements at iodine represent an unusual mode of reactivity. However, carbon ligand exchanges of this type at polyvalent iodine do find precedent in the literature106 and probably proceed via the tetrasubstituted iodate ions shown in equation 130. A similar mechanism was first proposed by Beringer and Chang to account for interconversions of diaryliodonium salts with aryllithium reagents (equation 131)106. 

Structures of vinyliodonium salts that have appeared in the literature since 1945 are shown in Table 8. For compounds that were reported earlier, the reader is directed to Willgerodt s monograph115 and to the compilation of polyvalent iodine compounds by Beringer and Gindler141. Table 8 includes a number of vinyliodonium ions whose stereoiso-meric configurations (i.e. is or Z) have been reported. Most of these assignments are based on NMR information and require some discussion. 

Polyvalent iodine compounds in the oxidation of heterocycles 02CRV2523. 

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