Oxidation with hypervalent iodine reagents

Carbonyl oxidation with hypervalent iodine reagents involves the functionalization of the a-position of carbonyl compounds through the intermediacy of a hypervalent iodine enolate species. This electrophilic intermediate may be attacked by a variety of nucleophiles or undergo rearrangement or elimination [13]. Enantiomerically pure, a-substituted carbonyl compounds represent a family of derivatives important in nearly all fields of organic chemistry [14],... 

Alkene substrates on oxidation with hypervalent iodine reagents allow various transformations depending on their structure and on the reaction conditions. Some of these reactions using chiral hypervalent iodine reagent are reported to be stereoselective. As described earlier, the Wirth group developed new chiral... 

The oxidation of phenols with hypervalent iodine compounds has been used frequently and nucleophilic additions can be performed as well as cyclization reactions using this technique. The resulting quinone derivatives show high reactivity and they have been used in a various subsequent reactions. Substituted phenols like 32 [78] or 34 [79] have been oxidized by hypervalent iodine reagents and, depending on the substitution pattern, cyclizations have taken place as shown in Scheme 16. Product 33 is unstable and undergoes subsequent... 

The oxidation of carbonyl compounds can be achieved with hypervalent iodine reagents quite easily. A general feature of these reactions is the electrophilic attack of the hypervalent iodine reagent at the a-carbon atom of a carbonyl group and a review on this chemistry has been published recently [6]. This leads to hypervalent iodine intermediates of type 55. These phenyliodinated intermediates are quite unstable and a variety of subsequent reactions are possible. Intermediates 55, Scheme 24, can be considered as umpoled substrates regarding the reactivity of the a-position of the initial carbonyl compounds. Major processes are the substitution by a nucleophile (see Sect. 3.5.1 Functionalization in the a-Position) or the introduction of a carbon-carbon double bond (see Sect. 3.5.2 Introduction of an a,/ -Unsaturation). 

Total Synthesis of Natural Products via Oxidation of Aromatic Compounds with Hypervalent Iodine Reagents... 

A. Kirschning, G. Drager, and J. Harders, Regioselective oxidation of glycals with hypervalent iodine reagents, Synlett, (1993) 289-290. 

Oxidative Coupling Reactions with Hypervalent Iodine Reagents... 

Oxidative Coupling Reactions with Hypervalent Iodine Reagents 484 Other Reagents for the Oxidative Coupling Reaction 495 Iron(III) 495... 

Ionic solvents have been used to facilitate the Heck reaction (13-9), the oxidation of alcohols with hypervalent iodine reagents (19-3)," and the catalytic asymmetric dihydroxylation of olefins (15-48) using a recoverable and reusable osmium/... 

For a review on the oxidation of alcohols with hypervalent iodine reagents such as IBX and DMP, see H. Tohma, Y. Kita, Adv. Synth. Catal. 2004, 346, 111-124. 

Yadav JS, Reddy BVS, Basak AK, Narsaiah AV (2004) Recyclable 2nd generation ionic liquids as green solvents for the oxidation of alcohols with hypervalent iodine reagents. Tetrahedron 60 2131-2135... 

Oxime 354 served as the starting material in the domino step, which, upon treatment with hypervalent iodine reagent PhI(OAc)2, led to an oxidative dearomatization. The quinone congener 356 was formed by intramolecular nucleophilic attack of the free hydroxyl group. Concomitantly, the oxime functionahty was oxidized to the nitrile oxide, which could then react with the a,fi-unsaturated ketone in a 1,3-dipolar cycloaddition to form the tetracyclic cortistatin carbon skeleton 355. 

In the presence of a chiral catalyst such as rhodium(II) (5)-/V l,8-naphthanoyl-tert-leucinate dimer, Troc-amino indane was produced with 56% yield and 2.57 1 enantiomeric ratio. In contrast to other methods, no hypervalent iodine reagent (typically used stoichiometrically or in excess and forming iodobenzene as by-product) is required for oxidation of the amine component. However, a slight excess of the aromatic alkane component (5 equiv) must be used to achieve good conversions. The reactivity of rhodium nitrenes generated from 2,2,2-trichloroethyl-/V-tosyloxycarbamate with aliphatic alkanes is similar to the one observed with metal nitrenes obtained from the oxidation of sulfamate with hypervalent iodine reagent. Troc-protected amino cyclohexane and cyclooctane were obtained, respectively, in 73 and 62% yields when 2 equiv of alkanes was used, whereas yields up to 85% were observed with 5 equiv (eq 3). 

To date, this chemistry remains rather unexplored with respect to the development of related transition metal catalyses [43]. Still, difunctimialization of alkenes with hypervalent iodine reagents has been explored extensively over the past few decades [44], and there are important recent contributions that indicate that hypervalent iodines can indeed serve as suitable chiral reagents or catalysts for enantio-selective oxidation of alkenes [43-46]. 

Kita Y, Tohma H, Inagaki M, Hatanaka K, Yakura T (1991) A novel oxidative azidation of aromatic compounds with hypervalent iodine reagent, phenyliodine(III) bis(trifluoroacetate) (PIFA) and trimethylsilyl azide. Tetrahedron Lett 32(34) 4321 324... 

Common alcohol oxidation methods employ stoichiometric amounts of toxic and reactive oxidants like Cr03, hypervalent iodine reagents (Dess-Martin) and peracids that pose severe safety and environmental hazards in large-scale industrial reactions. Therefore, a variety of catalytic methods for the oxidation of alcohols to aldehydes, ketones or carboxylic acids have been developed employing hydrogen peroxide or alkyl hydroperoxides as stoichiometric oxygen sources in the presence of catalytic amounts of a metal catalyst. The commonly used catalysts for alcohol oxidation are different MoAV(VI), Mn(II), Cr(VI), Re(Vn), Fe(II) and Ru complexes . A selection of published known alcohol oxidations with different catalysts will be presented here. 

The use of hypervalent iodine reagents in carbon-carbon bond forming reactions is summarized with particular emphasis on applications in organic synthesis. The most important recent methods involve the radical decarboxylative alkylation of organic substrates with [bis(acyloxy)iodo]arenes, spirocyclization of para- and ortho-substituted phenols, the intramolecular oxidative coupling of phenol ethers, and the reactions of iodonium salts and ylides. A significant recent research activity is centered in the area of the transition metal-mediated coupling reactions of the alkenyl-, aryl-, and alkynyliodonium salts. 

The use of hypervalent iodine reagents for heteroatom-heteroatom bond forming reactions is well established in the context of classical oxidation chemistry [1-11]. For example, oxidations of anilines to azobenzenes, thiols to disulfides, and sulfides to sulfoxides with aryl-A3-iodanes were documented decades ago [1-5]. During the last ten years, particular attention has also been given to oxidative transformations of compounds derived from heavier elements, including the interception of reaction intermediates or initially formed products with external nucleophiles. A second important development is the utilization of sulfonyliminoiodanes, ArI = NS02R, for heteroatom-nitrogen bond formation, especially for imidations of sulfur, selenium, phosphorus and arsenic com-... 

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