Oxidation hypervalent iodo compound

Disulfides, diselenides, and ditellurides can be oxidized by hypervalent iodine compounds quite easily. Depending on the reaction conditions disulfides can be oxidized to sulfinic esters [59] or thiosulfonic S-esters [60,61]. Diselenides can be transformed into selenosulfonates [62]. Arenetellurinic mixed anhydrides are mild oxidants and can be obtained by oxidation of the corresponding ditellurides as shown in Scheme 9 [63]. Recently it was shown that a thioacetal based linker for solid-phase synthesis can be cleaved oxidatively using [bis(trifluoro-acetoxy)iodo]benzene 4 [64]. 

A pyrrolone ring is formed from a methylene and a ring-carbon in a low-temperature cyclo-oxidation of the amide (104.2) which is promoted by [bis(tri-fluoroacetyloxy)iodo]benzene. The application of hypervalent iodine compounds to the formation of C—C bonds has been reviewed [3714]. A similar compound (104.3) is cyclized in lower yield by stirring it at 0 C with trifluoroacetic anhydride. 

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. 

Iodine in combination with [bis(acyloxy)iodo]arenes is a classical reagent combination for the oxidative iodination of aromatic and heteroaromatic compounds [99], A typical iodination procedure involves the treatment of electron-rich arenes with the PhI(OAc)2-iodine system in a mixture of acetic acid and acetic anhydride in the presence of catalytic amounts of concentrated sulfuric acid at room temperature for 15 min [100,101]. A solvent-free, solid state oxidative halogenation of arenes using PhI(OAc)2 as the oxidant has been reported [102]. Alkanes can be directly iodinated by the reaction with the PhI(OAc)2-iodine system in the presence of f-butanol under photochemical or thermal conditions [103]. Several other iodine(in) oxidants, including recyclable hypervalent iodine reagents (Chapter 5), have been used as reagents for oxidative iodination of arenes [104-107]. For example, a mixture of iodine and [bis(trifluoroacetoxy)iodo]benzene in acetonitrile or methanol iodinates the aromatic ring of methoxy substituted alkyl aryl ketones to afford the products of electrophilic mono-iodination in 68-86% yield [107]. 

Iodosylbenzoic acid (85) is also a convenient recyclable hypervalent iodine oxidant for the synthesis of a-iodo ketones by oxidative iodination of ketones [88], Various ketones and p-dicarbonyl compounds can be iodinated by this reagent system under mild conditions to afford the respective a-iodo substituted carbonyl compounds in excellent yields. The final products of iodination are conveniently separated from by-products by simple treatment with anionic exchange resin Amberlite IRA 900 HCOs" and are isolated with good purity after evaporation of the solvent. The reduced form of the hypervalent iodine oxidant, 3-iodobenzoic acid (59), can be recovered in 91-95% yield from the Amberlite resin by treatment with aqueous hydrochloric acid followed by extraction with ethyl acetate [88]. 

Several examples of solvent-free reactions of hypervalent iodine reagents under microwave irradiation conditions have been reported [2, 68-72], A solvent-less oxidation of 1,4-dihydropyridines to the respective pyridines can be performed using [bis(trifluoroacetoxy)iodo]benzene at room temperature under microwave irradiation conditions [68], Carbonyl compounds (aldehydes, ketones and esters) can be converted into the respective a-[(2,4-dinitrobenzene)sulfonyl]oxy carbonyl compounds by the reaction of the neat carbonyl compounds with [hydroxy(2,4-dinitrobenzenesulfonyloxy)iodo]benzene (HDNIB) under microwave irradiation in less than 40 s [69], Likewise, a-halocarbonyl compounds 55 can be conveniently prepared by sequential treatment of carbonyl compounds 54 with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation (MWI) conditions (Scheme 6.21) [70],... 

Moucheron et al. discovered a direct method for the oxidation of electron-poor quinoxalines, 1,4,5,8-tetraazaphenanthrenes, and 1,4,5,8,9,12-hexaazatriphenylenes, by employing hypervalent X, -iodinane compounds, such as diacetoxyiodobenzene (DIB) and [bis(trifluoroacetoxy) iodo]benzene (BTI), giving the respective quinoxalinediones... 

Iodine can form organic compounds with oxidation states of +3 and 4-5. The most common stmctural types of organic polyvalent iodine species are represented by structures 1—3, shovm in Figure 1. Structure 1, the iodo-nium ion, formally does not belong to hypervalent species since it has only eight valence electrons on the iodine atom however, in the modem Hterature iodonium salts are commonly treated as the 10-electron hypervalent... 

Wirth and coworkers prepared iodoxolones 66, 68, 70, and 71 by the oxidation of (Z)-3-iodo acrylic acid derivatives 65, 67, and 69 using peracetic acid or other common oxidants (Scheme 5 2009OL3578). Structures of products 66 and 68 were established by X-ray analysis (2009OL3578). Bond angles and distances within the five-membered iodoxolone system are similar to the respective X-ray structural parameters of 1-hydroxybenziodoxole derivatives (see Section 3.2.2.2 1964NAT512, 2007ACE6529). lodoxolones 66, 68, 70, and 71 have stability and reactivity similar to the noncyclic hypervalent iodine(III) compounds (2009OL3578). 

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