Use Of Hypervalent Iodine Reagents Research Articles

Chiral Hypoiodite Salt Catalysts for Enantioselective Oxidative Transformations

AbstractIodine and its hypervalent derivatives have emerged as versatile and environmentally friendly oxidative reagents in organic synthesis, offering efficient ways to form new bonds. However, the use of hypervalent iodine reagents is challenging, as they are unstable, potentially explosive, and costly. Therefore, hypoiodite species derived from onium iodites using safe and inexpensive oxidants are considered more promising for facilitating oxidative transformations. Nevertheless, applications of such catalytic systems are still limited in scope, especially for asymmetric reactions. In this concept paper, we described recent progress in chiral hypoiodite‐catalyzed enantioselective oxidative bond‐forming reactions, focusing on carbon–oxygen, carbon–nitrogen, and carbon–carbon bond formation reactions using ammonium and guanidinium salts as onium iodites.

New Strategies for the Functionalization of Carbonyl Derivatives via α-Umpolung: From Enolates to Enolonium Ions.

ConspectusUmpolung, a term describing the reversal of innate polarity, has become an indispensable tool to unlock new chemical space by overcoming the limitations of natural polarity. Introduced by Dieter Seebach in 1979, this principle has had a tremendous impact on synthetic organic chemistry, offering previously inaccessible retrosynthetic disconnections. In contrast to the great progress made over the past decades for the generation of effective acyl anion synthons, the umpolung at the α-position of carbonyls (converting enolates into enolonium ions) has long proved challenging and only recently regained traction. Aiming to develop synthetic approaches to α-functionalization capable of complementing enolate chemistry, our group initiated, nearly 6 years ago, a program devoted to the α-umpolung of carbonyl derivatives. In this Account, following an overview of established methods, we will summarize our findings in this rapidly developing field. We focus on two distinct, yet related, topics of two carbonyl classes: (1) amides, where umpolung is enabled by electrophilic activation, and (2) ketones, where umpolung is enabled using hypervalent iodine reagents. Our group has developed several protocols to allow amide umpolung and subsequent α-functionalization, relying on electrophilic activation. Over the course of our investigations, transformations that are particularly challenging using enolate-based approaches, such as the direct α-oxygenation, α-fluorination, and α-amination of amides as well as the synthesis of 1,4-dicarbonyls from amide substrates, have been unlocked. Based on some of our most recent studies, this method has been shown to be so general that almost any nucleophile can be added to the α-position of the amide. In this Account, special emphasis will be placed on the discussion of mechanistic aspects. It is important to note that recent progress in this area has involved a shift in focus, moving even further away from the amide carbonyl, a development that shall also be detailed in a final subsection that highlights our latest investigations of umpolung-based remote functionalization of the β- and γ-positions of amides. The second section of this Account covers our more recent work dedicated to the exploration of the enolonium chemistry of ketones, unlocked through the use of hypervalent iodine reagents. By placing our work in the context of previous pioneering achievements, which mainly focused on the α-functionalization of carbonyls, we discuss new skeletal reorganizations of enolonium ions enabled by the unique properties of incipient positive charges α to electron-deficient moieties. Transformations such as intramolecular cyclopropanations and aryl migrations are covered and supplemented by detailed insight into the unusual nature of the intermediate species, including nonclassical carbocations.

Polymer up-cycling by mangana-electrocatalytic C(sp3)-H azidation without directing groups.

The chemical up-cycling of polymers into value-added materials offers a unique opportunity to place plastic waste in a new value chain towards a circular economy. Herein, we report the selective up-cycling of polystyrenes and polyolefins to C(sp3)-H azidated materials under electrocatalytic conditions. The functionalized polymers were obtained with high retention of mass average molecular mass and high functionalization through chemo-selective mangana-electrocatalysis. Our strategy proved to be broadly applicable to a variety of homo- and copolymers. Polyethylene, polypropylene as well as post-consumer polystyrene materials were functionalized by this approach, thereby avoiding the use of hypervalent-iodine reagents in stoichiometric quantities by means of electrocatalysis. This study, hence, represents a chemical oxidant-free polymer functionalization by electro-oxidation. The electrocatalysis proved to be scalable, which highlights its unique feature for a green hydrogen economy by means of the hydrogen evolution reaction (HER).

Palladium-Catalyzed Organic Reactions Involving Hypervalent Iodine Reagents.

The chemistry of polyvalent iodine compounds has piqued the interest of researchers due to their role as important and flexible reagents in synthetic organic chemistry, resulting in a broad variety of useful organic molecules. These chemicals have potential uses in various functionalization procedures due to their non-toxic and environmentally friendly properties. As they are also strong electrophiles and potent oxidizing agents, the use of hypervalent iodine reagents in palladium-catalyzed transformations has received a lot of attention in recent years. Extensive research has been conducted on the subject of C—H bond functionalization by Pd catalysis with hypervalent iodine reagents as oxidants. Furthermore, the iodine(III) reagent is now often used as an arylating agent in Pd-catalyzed C—H arylation or Heck-type cross-coupling processes. In this article, the recent advances in palladium-catalyzed oxidative cross-coupling reactions employing hypervalent iodine reagents are reviewed in detail.

Use of Hypervalent Iodine Reagents in Visible Light-Promoted α-Ketoacylations of Sulfoximines with Aryl Alkynes.

In visible light, sulfoximidoyl-containing hypervalent iodine reagents react with aryl alkynes to give N-α-ketoacylated sulfoximines in good to high yields. The process is metal- and base-free, providing the diketonic products without the use of highly oxygenated reagents such as peroxides. Results from mechanistic investigations suggest the intermediacy of radicals and reveal the importance of molecular oxygen.

Hypervalent Iodine Reagents in Palladium-Catalyzed Oxidative Cross-Coupling Reactions.

Hypervalent iodine compounds are valuable and versatile reagents in synthetic organic chemistry, generating a diverse array of useful organic molecules. Owing to their non-toxic and environmentally friendly features, these reagents find potential applications in various oxidative functionalization reactions. In recent years, the use of hypervalent iodine reagents in palladium-catalyzed transformations has been widely studied as they are strong electrophiles and powerful oxidizing agents. For instance, extensive work has been carried out in the field of C–H bond functionalization via Pd-catalysis using hypervalent iodine reagents as oxidants. In addition, nowadays, iodine(III) reagents have been frequently employed as arylating agents in Pd-catalyzed C–H arylation or Heck-type cross-coupling reactions. In this review, recent advancements in the area of palladium-catalyzed oxidative cross-coupling reactions using hypervalent iodine reagents are summarized in detail.

Fluorination and Fluoroalkylation Reactions Mediated by Hypervalent Iodine Reagents

AbstractThis review summarizes the progress in the fluorination and fluoroalkylation of electron‐rich systems with diverse fluorine (F) and fluoroalkyl (Rfn) reagents employing hypervalent iodine compounds as initiators in the last few decades. Because of the strong electrophilicity, high oxidizing properties, low toxicity, air and moisture stability, ready availability, ease of handling, and mild reaction conditions, the hypervalent iodine reagents have been widely utilized in modern organic chemistry. In particular, the use of hypervalent iodine reagents to initiate the C−F and C−Rfn (Rfn=CF2H, CF3, perfluoroalkyl, OCH2CF3, SCF3, SeCF3 and etc) bond formation has been increasingly developed. In these reactions, hypervalent iodine compounds behave as powerful oxidants or electrophiles and activate the fluorination/fluoroalkylation reagents, the transition‐metal catalysts, or the substrates to in situ form electrophilic or radical intermediates, which subsequently participate in fluorination, difluoromethylation, trifluoromethylation, perfluoroalkylation, trifluoroethoxylation, fluoroalkylthiolation, trifluoromethylselenolation and others under mild conditions. Although great achievements have been made in this area, they are just the initial phase and still require a wide scope for improvement. It is anticipated that this review will draw much attention from the organic chemistry community and inspire more contributions in the development of new hypervalent‐iodine‐mediated fluorination and fluoroalkylation reactions.magnified image

Access to Vinyl Ethers and Ketones with Hypervalent Iodine Reagents as Oxy-Allyl Cation Synthetic Equivalents.

We report an Umpolung strategy of enol ethers to generate oxy-allyl cation equivalents based on the use of hypervalent iodine reagents. Under mild basic conditions, the addition of nucleophiles to aryloxy-substituted vinylbenziodoxolone (VBX) reagents, easily available in two steps from silyl alkynes, resulted in the stereoselective formation of substituted aryl enol ethers. The reaction was most efficient with phenols as nucleophiles, but preliminary results were also achieved for C- and N- nucleophiles. In absence of external nucleophiles, the 2-iodobenzoate group of the reagent was transferred. The obtained aryl enol ethers could then be transformed into α-difunctionalized ketones by oxidation. The described "allyl cation"-like reactivity contrast with the well-established "vinyl-cation" behavior of alkenyl iodonium salts.

Enantioselective Synthesis of N-C Axially Chiral Compounds by Cu-Catalyzed Atroposelective Aryl Amination.

N-C axially chiral compounds have emerged recently as appealing motifs for drug design. However, the enantioselective synthesis of such molecules is still poorly developed and surprisingly no metal-catalyzed atroposelective N-arylations have been described. Herein, we disclose an unprecedented Cu-catalyzed atroposelective N-C coupling that proceeds at room temperature. Such mild reaction conditions, which are a crucial parameter for atropostability of the newly generated products, are operative thanks to the use of hypervalent iodine reagents as a highly reactive coupling partners. A large panel of the N-C axially chiral compounds was afforded with very high enantioselectivity (up to >99 % ee) and good yields (up to 76 %). Post-modifications of thus accessed atropisomeric compounds allows further expansion of the diversity of these appealing compounds.

Enantioselective Synthesis of N–C Axially Chiral Compounds by Cu‐Catalyzed Atroposelective Aryl Amination

AbstractN−C axially chiral compounds have emerged recently as appealing motifs for drug design. However, the enantioselective synthesis of such molecules is still poorly developed and surprisingly no metal‐catalyzed atroposelective N‐arylations have been described. Herein, we disclose an unprecedented Cu‐catalyzed atroposelective N−C coupling that proceeds at room temperature. Such mild reaction conditions, which are a crucial parameter for atropostability of the newly generated products, are operative thanks to the use of hypervalent iodine reagents as a highly reactive coupling partners. A large panel of the N−C axially chiral compounds was afforded with very high enantioselectivity (up to >99 % ee) and good yields (up to 76 %). Post‐modifications of thus accessed atropisomeric compounds allows further expansion of the diversity of these appealing compounds.

C‐Terminal Bioconjugation of Peptides through Photoredox Catalyzed Decarboxylative Alkynylation

AbstractWe report the first decarboxylative alkynylation of the C‐terminus of peptides starting from free carboxylic acids. The reaction is fast, metal‐free, and proceeds cleanly to afford alkynylated peptides with a broad tolerance for the C‐terminal amino acid. By the use of hypervalent iodine reagents, the introduction of a broad range of functional groups was successful. C‐terminal selectivity was achieved by differentiation of the oxidation potentials of the carboxylic acids based on the use of fine‐tuned organic dyes.

C-Terminal Bioconjugation of Peptides through Photoredox Catalyzed Decarboxylative Alkynylation.

We report the first decarboxylative alkynylation of the C-terminus of peptides starting from free carboxylic acids. The reaction is fast, metal-free, and proceeds cleanly to afford alkynylated peptides with a broad tolerance for the C-terminal amino acid. By the use of hypervalent iodine reagents, the introduction of a broad range of functional groups was successful. C-terminal selectivity was achieved by differentiation of the oxidation potentials of the carboxylic acids based on the use of fine-tuned organic dyes.

When nucleoside chemistry met hypervalent iodine reagents.

There has been increasing use of hypervalent iodine reagents in the field of nucleoside chemistry. Applications span: (a) synthesis of nucleoside analogues with sulfur and seleno sugar surrogates, (b) synthesis of unusual carbocyclic and ether ring-containing nucleosides, (c) introduction of sulfur and selenium into pyrimidine bases of nucleosides and analogues, (d) synthesis of isoxazole and isoxazoline ring-containing nucleoside analogues, (e) involvement of purine ring nitrogen atoms for remote C-H bond oxidation, and (f) metal-catalyzed and uncatalyzed synthesis of benzimidazolyl purine nucleoside analogues by intramolecular C-N bond formation. This review offers a perspective on developments involving the use of hypervalent iodine reagents in the field of nucleoside chemistry that have appeared in the literature in the 2003-2017 time frame.

Straightforward Strategies for the Preparation of NH-Sulfox­imines: A Serendipitous Story

Sulfoximines are emerging as valuable new isosteres for use in medicinal chemistry, with the potential to modulate physicochemical properties. Recent developments in synthetic strategies have made the unprotected ‘free’ NH-sulfoximine group more readily available, facilitating further study. This account reviews approaches to NH-sulfoximines, with a focus on our contribution to the field. Starting from the development of catalytic strategies involving transition metals, more sustainable metal-free processes have been discovered. In particular, the use of hypervalent iodine reagents to mediate NH-transfer to sulfoxides is described, along with an assessment of the substrate scope. Furthermore, a one-pot strategy to convert sulfides directly into NH-sulfoximines is discussed, with N- and O-transfer occurring under the reaction conditions. Mechanistic evidence for the new procedures is included as well as relevant synthetic applications that further exemplify the potential of these approaches.1 Introduction2 Strategies to Form NH-Sulfoximines Involving Transition-Metal Catalysts3 Metal-Free Strategies to Prepare NH-Sulfoximines4 Mechanistic Evidence for the Direct Synthesis of NH-Sulfoximines from Sulfoxides and Sulfides5 Further Applications6 Conclusion

Hypervalent Iodine-Based Activation of Triphenylphosphine for the Functionalization of Alcohols

The use of hypervalent iodine reagents as a general tool for the activation of PPh3 and its application to the functionalization of alcohols is reported. Combination of PPh3 with PhICl2 or TolIF2 gives dihalophosphoranes that are characterized by 31P NMR, however, with PhIOAc2, PhI(OTFA)2, or the cyclic chloro(benzoyloxy)iodane, no phosphoranes were observed. Reaction of these iodanes with PPh3 in the presence of primary, secondary, or tertiary alcohols results in either halogenation or acyl-transfer products in moderate to high yield.

Transition metal-free dimerization of alkynes using hypervalent iodine reagents

This communication describes the use of hypervalent iodine reagents to facilitate the homo-coupling of terminal alkynes. A variety of different aliphatic and aromatic alkynes were successfully dimerized when using acetoxy-benziodoxole as the activating agent under operationally simple transition metal-free conditions.

ChemInform Abstract: Decarboxylative Functionalization of Cinnamic Acids

AbstractReview: [88 refs.

ChemInform Abstract: Electrophilic Trifluoromethylation by Use of Hypervalent Iodine Reagents

AbstractReview: 165 refs.

Electrophilic trifluoromethylation by use of hypervalent iodine reagents.

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTElectrophilic Trifluoromethylation by Use of Hypervalent Iodine ReagentsJulie Charpentier, Natalja Früh, and Antonio Togni*View Author Information Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, Vladimir-Prelog-Weg 2, CH-8093 Zurich, Switzerland*E-mail [email protected]Cite this: Chem. Rev. 2015, 115, 2, 650–682Publication Date (Web):August 25, 2014Publication History Received22 April 2014Published online25 August 2014Published inissue 28 January 2015https://doi.org/10.1021/cr500223hCopyright © 2014 American Chemical SocietyRIGHTS & PERMISSIONSACS AuthorChoiceArticle Views40691Altmetric-Citations1143LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (7 MB) Get e-AlertsSUBJECTS:Aromatic compounds,Chemical reactions,Hydrocarbons,Reagents,Trifluoromethylation Get e-Alerts

ChemInform Abstract: Gold‐Catalyzed Regioselective Synthesis of 2‐ and 3‐Alkynyl Furans.

AbstractProcedures are developed for the selective synthesis of 2‐ and 3‐alkynylated furans based on the use of hypervalent iodine reagents and gold catalysis.