Oxidative iodination

Addition of halogens proceeds stepwise, sometimes accompanied by oxidation. Iodine forms 2,3-diiodo-2-butene-l,4-diol (53). Depending on conditions, bromine gives 2,3-dibromo-2-butene-l,4-diol, 2,2,3,3-tetrabromobutane-l,4-diol, mucobromic acid, or... 

However, in strong hydrochloric acid, these reagents, as weU as iodic acid, oxidize iodine to iodine monochloride or to the ICl ion. 

A-Nor-B-homo steroids with different substitution patterns than those described above may be prepared by acid catalyzed cyclization of 3)3-hydroxy-5(10)-seco-cholest-tra/w-l(l0)-en-5-one acetate (134a) formed in 30-40% yield by mercuric oxide-iodine sensitized irradiation of cholestane-3j3,5a-diol... 

A simplified experimental system results when free radical scavengers such as nitric oxide, iodine, or oxygen are added to the samples before... 

A mixture of 1,4-dioxane and water is often used as the solvent for the conversion of aldehydes and ketones by H2Se03 to a-dicarbonyl compounds in one step (Eq. 8.117).331 Dehydrogenation of carbonyl compounds with selenium dioxide generates the a, (i-unsaturated carbonyl compounds in aqueous acetic acid.332 Using water as the reaction medium, ketones can be transformed into a-iodo ketones upon treatment with sodium iodide, hydrogen peroxide, and an acid.333 Interestingly, a-iodo ketones can be also obtained from secondary alcohol through a metal-free tandem oxidation-iodination approach. 

See other halogen oxides, iodine compounds, oxidants... 

See Other HALOGEN OXIDES, IODINE COMPOUNDS, OXIDANTS... 

SCHEME 2.62 Synthesis of alkylthiophenes 397-399 through oxidative iodination of the thiophene followed by Ni-catalyzed polymerization. (From Bolognesi, A., Botta, C., Geng, Z., Flores, C., and Denti, L., Synth. Met., 71, 2191, 1995 Bolognesi, A., Porzio, W., Bajo, G., Zannoni, G., and Fanning, L., Acta Polym., 50, 151, 1999.)... 

The phase-transfer catalysed oxidative iodination of a,p-unsaturated carbonyl compounds (Table 10.23) using iodine/persulphate to produce the a-iodo derivatives has been described [16]. Activated methylene groups are also iodinated under similar conditions. 

Of the organohahdes, only the iodides are prone to oxidation by dioxirane for example, iodobenzene is oxidized by DMD to a mixture of iodosobenzene and iodylbenzene. In contrast, alkyl iodides afford labile primary oxidation products, which eliminate the oxidized iodine functionality to result in aUcenes (equation 23). In such a dioxirane oxidation, the subsequent in-situ reaction of the alkene affords the corresponding epoxides . 

Iodine is a moderately strong oxidising agent (See Table 3.1). During oxidation iodine is reduced as follows ... 

The last reagent is added as a moderator to prevent a runaway reaction nitrobenzene, or an alternative oxidant (iodine or chloroanil are often recommended), is required to convert the product, 1,2-dihydroquinoline, into quinoline. 

Only the head-to-tail adducts were obtained in the [2+2] photoaddition of 4-hydroxy-l-phenyl[l,8]naphthyridin-2(l//)-one with various alkenes in methanol (Scheme 3). The photolysis of the hypoiodites generated by the in situ reaction of the cycloadducts with excess mercury(ll) oxide-iodine reagent in benzene induced a regioselective scission of the non-ring junction bond of the alkoxyl radical to give substituted 3,9-dihydro-9-phenylyfuro[2,3- ][l,8]naphthyridin-4(2//)-one and/or 3,5-dihydro-5-phenylfuro[3,2-f][l,8]naphthyridin-4-(2//)-ones <1996T6125>. 

Character ( f iodafee.—Some of the iodates when heated split into iodides and oxygen, others into metallic oxides, iodine, and oiygen. 

Iodic ucid. HIOi. is commonly prepared by oxidizing iodine with HNOr. Il is a strongly oxidizing acid, oxidizing iodide to iodine, xulhtc to sulfate, and H S to sulfur, It reacts vigorously even w ith dry carbon, phosphorus, or organic matin, ... 

CHE492), and when the oxidative iodination used nitric acid as oxidizer, mixtures of 3-iodo- and 3-nitro-2-pyrones eventuated (79CHE142). 

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