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.

Chemistry of Polyvalent Iodine

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...

Advances in Synthetic Applications of Hypervalent Iodine Compounds

Conventional methods for carrying out carbon–hydrogen functionalization and carbon–nitrogen bond formation are typically conducted at elevated temperatures, and rely on expensive catalysts as well as the use of stoichiometric, and perhaps toxic, oxidants. In this regard, electrochemical synthesis has recently been recognized as a sustainable and scalable strategy for the construction of challenging carbon–carbon and carbon–heteroatom bonds. Here, electrosynthesis has proven to be an environmentally benign, highly effective and versatile platform for achieving a wide range of nonclassical bond disconnections via generation of radical intermediates under mild reaction conditions. This review provides an overview on the use of anodic electrochemical methods for expediting the development of carbon–hydrogen functionalization and carbon–nitrogen bond formation strategies. Emphasis is placed on methodology development and mechanistic insight and aims to provide inspiration for future synthetic applications in the field of electrosynthesis.

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Electrochemical strategies for C-H functionalization and C-N bond formation.

Cyclizations of N-acyliminium ions.

Rephrasing Fuson's original formulation, the principle of
vinylogy explains how the influence of a functional group may be relayed to a distant point in the molecule when these two sites are connected to by conjugated unsaturated linkages, such as double and triple bonds or aromatic moieties.
This principle has been applied, over the years, to the majority of polar carbon-carbon bond-forming reactions of various repute, including the venerable Michael addition reaction, where the electrophilic -CdX site (1,2-addition) is “usurped” by a remote conjugated -RCdCR-CdX position (1,4-addition). The aldol addition reaction and the related
Mannich process, both fundamental pillars of organic synthesis, have not escaped this fate, and both of their
vinylogous extensions have emerged as extremely valuable
synthetic methodologies.

The Vinylogous Aldol and Related Addition Reactions: Ten Years of Progress†

A convenient methodology for the synthesis of 2-substituted pyrrolidines from α-amino acids is described. A number of cyclic and acyclic α-amino acid derivatives have been prepared in order to test the scope and diastereoselectivity of this method. These substrates were treated with iodosylbenzene or (diacetoxyiodo)benzene (DIB) and iodine in order to generate the corresponding carboxyl radical, which evolves by loss of carbon dioxide to produce a carbon radical which in turn undergoes oxidation to an N-acyliminium ion. This postulated intermediate could be trapped inter- or intramolecularly by oxygen, nitrogen and carbon nucleophiles. In the case of carbon nucleophiles, a Lewis acid is required for the concomitant carbon−carbon bond formation. High yields and modest diastereoselectivities were obtained. The present methodology was applied to the synthesis of ω-amino aldehydes or hemiaminals 8−14, 2-aminopyrrolidine derivative 15, aminolactone derivative 16, and azasugar analogues 17 and 18. When carbon n...

Tandem radical decarboxylation-oxidation of amino acids: A mild and efficient method for the generation of N-acyliminium ions and their nucleophilic trapping

Host-defense peptides, also called antimicrobial peptides (AMPs), whose protective action has been used by animals for millions of years, fulfill many requirements of the pharmaceutical industry, such as: (1) broad spectrum of activity; (2) unlike classic antibiotics, they induce very little resistance; (3) they act synergically with conventional antibiotics; (4) they neutralize endotoxins and are active in animal models. However, it is considered that many natural peptides are not suitable for drug development due to stability and biodisponibility problems, or high production costs. This review describes the efforts to overcome these problems and develop new antimicrobial drugs from these peptides or inspired by them. The discovery process of natural AMPs is discussed, as well as the development of synthetic analogs with improved pharmacological properties. The production of these compounds at acceptable costs, using different chemical and biotechnological methods, is also commented. Once these challenges are overcome, a new generation of versatile, potent and long-lasting antimicrobial drugs is expected.

/pdf/the-road-from-host-defense-peptides-to-a-new-generation-of-1qr74yz3j8.pdf

The Road from Host-Defense Peptides to a New Generation of Antimicrobial Drugs

We have demonstrated that chemically modified anticancer drugs can provide random laser (RL) when infiltrated in a biological tissue. A fluorescent biomarker has been covalently bound to tamoxifen, which is one of the most frequently used drugs for breast cancer therapy. The light emitted by the drug-dye composite is scattered in tissue, which acts as a gain medium. Both non-coherent and coherent RL regimes have been observed. Moreover, the analysis of power Fourier transforms of coherent RL spectra indicates that the tissues show a dominant random laser cavity length of about 18 µm, similar to the average size of single cells. These results show that RL could be obtained from other drugs, if properly marked with a fluorescent tag, which could be appealing for new forms of combined opto-chemical therapies.

https://iopscience.iop.org/article/10.1088/1612-2011/12/4/045805/pdf

Random laser in biological tissues impregnated with a fluorescent anticancer drug

Furan and Its Derivatives

The β-fragmentation of primary alkoxyl radicals, described in many cases as low-yielding and plagued by side reactions, can proceed in satisfactory yields using carbohydrate substrates. The only reaction that can compete significantly with the β-scission is the intramolecular hydrogen abstraction. The ratio of β-fragmentation to hydrogen abstraction can be varied according to the reaction conditions, the stereochemistry of the substituents (e.g., α- or β-anomeric substituents), and the protecting groups chosen. The carbohydrate substrates are easily prepared, and the mild reaction conditions are compatible with most functional groups. The β-scission reaction provides an expedient way toward shorter and less common sugar series and also toward α,ω-differently substituted cyclic ethers. These units are useful building blocks and are present in many natural products with interesting biological activity.

β-Fragmentation of Primary Alkoxyl Radicals versus Hydrogen Abstraction: Synthesis of Polyols and α,ω-Differently Substituted Cyclic Ethers from Carbohydrates

Alicia Boto

Papers

Tandem radical decarboxylation-oxidation of amino acids: A mild and efficient method for the generation of N-acyliminium ions and their nucleophilic trapping

The Road from Host-Defense Peptides to a New Generation of Antimicrobial Drugs

Random laser in biological tissues impregnated with a fluorescent anticancer drug

Furan and Its Derivatives

β-Fragmentation of Primary Alkoxyl Radicals versus Hydrogen Abstraction: Synthesis of Polyols and α,ω-Differently Substituted Cyclic Ethers from Carbohydrates