Viktor V. Zhdankin

Chemistry of Polyvalent Iodine

Starting from the early 1990’s, the chemistry of polyvalent iodine organic compounds has experienced an explosive development. This surging interest in iodine compounds is mainly due to the very useful oxidizing properties of polyvalent organic iodine reagents, combined with their benign environmental character and commercial availability. Iodine(III) and iodine(V) derivatives are now routinely used in organic synthesis as reagents for various selective oxidative transformations of complex organic molecules. Several areas of hypervalent organoiodine chemistry have recently attracted especially active interest and research activity. These areas, in particular, include the synthetic applications of 2-iodoxybenzoic acid (IBX) and similar oxidizing reagents based on the iodine(V) derivatives, the development and synthetic use of polymer-supported and recyclable polyvalent iodine reagents, the catalytic applications of organoiodine compounds, and structural studies of complexes and supramolecular assemblies of polyvalent iodine compounds. The chemistry of polyvalent iodine has previously been covered in four books1–4 and several comprehensive review papers.5–17 Numerous reviews on specific classes of polyvalent iodine compounds and their synthetic applications have recently been published.18–61 Most notable are the specialized reviews on [hydroxy(tosyloxy)iodo]benzene,41 the chemistry and synthetic applications of iodonium salts,29,36,38,42,43,46,47,54,55 the chemistry of iodonium ylides,56–58 the chemistry of iminoiodanes,28 hypervalent iodine fluorides,27 electrophilic perfluoroalkylations,44 perfluoroorgano hypervalent iodine compounds,61 the chemistry of benziodoxoles,24,45 polymer-supported hypervalent iodine reagents,30 hypervalent iodine-mediated ring contraction reactions,21 application of hypervalent iodine in the synthesis of heterocycles,25,40 application of hypervalent iodine in the oxidation of phenolic compounds,32,34,50–53,60 oxidation of carbonyl compounds with organohypervalent iodine reagents,37 application of hypervalent iodine in (hetero)biaryl coupling reactions,31 phosphorolytic reactivity of o-iodosylcarboxylates,33 coordination of hypervalent iodine,19 transition metal catalyzed reactions of hypervalent iodine compounds,18 radical reactions of hypervalent iodine,35,39 stereoselective reactions of hypervalent iodine electrophiles,48 catalytic applications of organoiodine compounds,20,49 and synthetic applications of pentavalent iodine reagents.22,23,26,59 The main purpose of the present review is to summarize the data that appeared in the literature following publication of our previous reviews in 1996 and 2002. In addition, a brief introductory discussion of the most important earlier works is provided in each section. The review is organized according to the classes of organic polyvalent iodine compounds with emphasis on their synthetic application. Literature coverage is through July 2008.

Advances in Synthetic Applications of Hypervalent Iodine Compounds.

The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C-C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of using hypervalent iodine compounds as an environmentally sustainable alternative to heavy metals.

Organoiodine(V) reagents in organic synthesis.

Organohypervalent iodine reagents have attracted significant recent interest as versatile and environmentally benign oxidants with numerous applications in organic synthesis. This Perspective summarizes synthetic applications of hypervalent iodine(V) reagents: 2-iodoxybenzoic acid (IBX), Dess-Martin periodinane (DMP), pseudocyclic iodylarenes, and their recyclable polymer-supported analogues. Recent advances in the development of new catalytic systems based on the generation of hypervalent iodine species in situ are also overviewed.

Hypervalent Iodine Catalyzed Generation of Nitrile Oxides from Oximes and their Cycloaddition with Alkenes or Alkynes

Hypervalent iodine catalyzed oxidation of aldoximes using oxone as a terminal oxidant generates nitrile oxides, which react with alkenes and alkynes to give the corresponding isoxazolines and isoxazoles in moderate to good yields. This reaction involves active hypervalent iodine species formed in situ from catalytic iodoarene and oxone in the presence of hexafluoroisopropanol in aqueous methanol solution.

Benziodoxole-Based Hypervalent Iodine Reagents in Organic Synthesis

Five-membered hypervalent iodine heterocycles derived from benziodoxole and benziodazole oxide have recently emerged as reagents of choice for various synthetically useful oxidative transformations. In particular, IBX (2-iodoxybenzoic acid) and DMP (Dess-Martin periodinane) are widely used for the selective oxidation of primary and secondary alcohols and for a variety of other important oxidations. IBX-amides and IBX-esters are a new class of pentavalent iodine reagents with a pseudo-benziodoxole structure and a reactivity pattern similar to IBX.

1-Cyano-3-(1H)-1,2-benziodoxols: stable cyanoiodinanes and efficient reagents for direct N-alkyl cyanation of N,N-dialkylarylamines

Abstract Cyanobenziodoxols 2 and 4 can be prepared from benziodoxols 1 or 3 and cyanotrimethylsilane in the form of stable, crystalline compounds. Cyanobenziodoxol 2 reacts with N,N-dimethylary lamines under mild conditions to afford N-(cyanomethyl)-N-methylarylamines 6 in excellent yields.

Preparation and chemistry of stable azidoiodinanes: 1-Azido-3,3-bis(trifluoromethyl)-3-(1H)-1,2-benziodoxol and 1-Azido-1,2-benziodoxol-3-(1H)-one

Abstract Azidoiodinanes 2,4,6 can be prepared from benziodoxols 1,3 and trimethylsilyl azide in the form of stable, crystalline compounds. These compounds are potentially useful reagents for electrophilic azidonation of organic substrates. For example, reaction of azide 6 with cyclohexene affords 2-azidocyclohexanone 7 in moderate yield.

Hofmann Rearrangement of Carboxamides Mediated by Hypervalent Iodine Species Generated in Situ from Iodobenzene and Oxone: Reaction Scope and Limitations

Alkylcarboxamides can be converted to the respective amines by Hofmann rearrangement using hypervalent iodine species generated in situ from PhI and Oxone in aqueous acetonitrile. On the basis of this reaction, a convenient experimental procedure for the preparation of alkylcarbamates using Oxone as the oxidant in the presence of iodobenzene in methanol has been developed. An efficient method for direct conversion of substituted benzamides to the respective quinone derivatives by treatment with Oxone and iodobenzene in aqueous acetonitrile has also been found.

Synthesis and structure of benzoboroxoles: novel organoboron heterocycles

Abstract Benzoboroxoles (5) can be prepared from the readily available o-bromobenzyl alcohols via dilithiation followed by reaction with triisopropylborate. X-Ray structural analysis of 1-hydroxy-3(1H)-1,2-benzoboroxole (5a) as well as the results of ab initio molecular orbital calculations indicate a planar structure of the boron center with a relatively short CB bond. Preliminary results regarding the chemistry of benzoboroxoles are also reported.

Novel reagents containing hypervalent iodine and their use for electrophilic additions to olefins

Abstract A series of novel I(III) containing reagents have been developed and their electrophilic reactions with olefins giving vic -disubstituted derivatives (including vic -ditriflates) are described.