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The synthesis of substituted 1,4-benzoquinones, a biologically important class of compounds, was developed using [mu]-oxodi(phenyliodanyl) diacetate, a (diacetoxyiodo)benzene-based oxidizing reagent, in order to introduce second-year undergraduate organic laboratory students in their second semester or advanced organic students to increasingly popular and environmentally friendly hypervalent iodine chemistry. This experiment develops on concepts found in the undergraduate organic chemistry curriculum; conveniently fits into approximately two 3 h lab modules; and utilizes regularly found equipment and inexpensive, commercially available chemicals.

This review summarizes the structural and synthetic aspects of heterocyclic molecules incorporating an atom of a hypervalent main-group element. The term "hypervalent" has been suggested for derivatives of main-group elements with more than eight valence electrons, and the concept of hypervalency is commonly used despite some criticism from theoretical chemists. The significantly higher thermal stability of hypervalent heterocycles compared to their acyclic analogs adds special features to their chemistry, particularly for bromine and iodine. Heterocyclic compounds of elements with double bonds are not categorized as hypervalent molecules owing to the zwitterionic nature of these bonds, resulting in the conventional 8-electron species. This review is focused on hypervalent heterocyclic derivatives of nonmetal main-group elements, such as boron, silicon, nitrogen, carbon, phosphorus, sulfur, selenium, bromine, chlorine, iodine(III) and iodine(V). [ABSTRACT FROM AUTHOR]

A series of new isoxazole‐substituted aryl iodides 1 a–1 d have been synthesized by DIB‐mediated [3+2] cycloaddition reaction of 2‐iodo‐1,3‐bis(prop‐2‐yn‐1‐yloxy) benzene (4) with corresponding benzaldehyde oximes 5 a–5 d. Structure of the synthesized aryl iodides 1 were characterized by IR, 1H NMR, 13C NMR and HRMS. The structure of 1 a was also confirmed by single‐crystal X‐ray crystallography. Further, catalytic activity of iodoarenes 1 a–1 d was screened for the oxidation of hydroquinones and sulfides. On oxidation using aryl iodides 1 with m‐CPBA as terminal oxidant, hydroquinones afforded benzoquinones while sulfides gave corresponding sulfoxides in good to excellent yields. Iodoarene 1 b showed the best catalytic activity for the oxidation of sulfides and hydroquinones. Moreover, iodoarene 1 b, was also utilized for α‐oxytosylation of acetophenones. [ABSTRACT FROM AUTHOR]

We report a greener peptide coupling using bicyclic benziodazolone and triarylphosphine as coupling reagents. Bicyclic benziodazolone also works as a base and can be recovered as the corresponding iodine(I) compound after use, which can be converted to the original iodine(III) reagent by electrolytic oxidation. [ABSTRACT FROM AUTHOR]

Hypervalent iodine compounds have found broad application in modern organic chemistry as reagents and catalysts. Cyclic hypervalent iodine reagents based on the benziodoxole heterocyclic system have higher stability compared to their acyclic analogues, which makes possible the preparation and safe handling of the reagents with special ligands such as azido, cyano, and trifluoromethyl groups. Numerous iodine‐substituted benziodoxole derivatives have been prepared and utilized as reagents for transfer of the substituent on hypervalent iodine to organic substrate. Reactions of these reagents with organic substrates can be performed under metal‐free conditions, in the presence of transition metal catalysts, or using photocatalysts under photoirradiation conditions. In this review, we focus on the most recent synthetic applications of cyclic hypervalent iodine(III) reagents with the following ligands: N3, NHR, CN, CF3, SCF3, OR, OAc, ONO2, and C(=N2)CO2R. The review covers literature published mainly in the last 5 years. [ABSTRACT FROM AUTHOR]

Hypervalent iodine reagents are in high current demand due to their exceptional reactivity in oxidative transformations, as well as in diverse umpolung functionalization reactions. Cyclic hypervalent iodine compounds, known under the general name of benziodoxoles, possess improved thermal stability and synthetic versatility in comparison with their acyclic analogs. Aryl-, alkenyl-, and alkynylbenziodoxoles have recently received wide synthetic applications as efficient reagents for direct arylation, alkenylation, and alkynylation under mild reaction conditions, including transition metal-free conditions as well as photoredox and transition metal catalysis. Using these reagents, a plethora of valuable, hard-to-reach, and structurally diverse complex products can be synthesized by convenient procedures. The review covers the main aspects of the chemistry of benziodoxole-based aryl-, alkynyl-, and alkenyl- transfer reagents, including preparation and synthetic applications. [ABSTRACT FROM AUTHOR]

Organic azides have found wide application in various fields of science and technology. This review summarizes recently developed approaches to the direct, one‐step synthesis of diverse organic azides utilizing hypervalent iodine reagents. The first part of review deals with the azidation using unstable azidoiodinanes generated in situ from common hypervalent iodine reagents (such as diacetoxyiodobenzene or iodosylbenzene) and a source of azide anion (TMSN3 or NaN3). The second part of review is dedicated to the application of stable azidobenziodoxoles as useful azidating reagents that allow selective direct azidation of C−H bonds or double carbon‐carbon bonds under mild reaction conditions. The use of azidobenziodoxoles eliminates the main disadvantages of the traditional approaches to organic azides, such as the need in pre‐functionalization of organic substrates and harsh reaction conditions. Synthetic application of azidobenziodoxoles made possible direct selective azidation of a plethora of organic substrates including complex molecules at the late synthetic stage. [ABSTRACT FROM AUTHOR]

Dehydrogenative cycloisomerization/arylation sequence of heteroatom nucleophile‐tethered unactivated alkynes provides a facile and powerful approach to C−C bond formation between the generated heterocycles and unfunctionalized arenes. Here, we describe a hypervalent iodine(III)‐catalyzed synthesis of oxazoles concomitant with the introduction of aryl groups into side chain from N‐propargyl carboxamides and arenes, representing first C(sp3)−C(sp2) bond formation by the catalytic dehydrogenative cycloisomerization/arylation reaction in exo‐dig modes. [ABSTRACT FROM AUTHOR]

Hypervalent iodine (HVI) reagents have gained much attention as versatile oxidants because of their low toxicity, mild reactivity, easy handling, and availability. Despite their unique reactivity and other advantageous properties, stoichiometric HVI reagents are associated with the disadvantage of generating non-recyclable iodoarenes as waste/co-products. To overcome these drawbacks, the syntheses and utilization of various recyclable hypervalent iodine reagents have been established in recent years. This review summarizes the development of various recyclable non-polymeric, polymer-supported, ionic-liquid-supported, and metal–organic framework (MOF)-hybridized HVI reagents. 1 Introduction 2 Polymer-Supported Hypervalent Iodine Reagents 2.1 Polymer-Supported Hypervalent Iodine(III) Reagents 2.2 Polymer-Supported Hypervalent Iodine(V) Reagents 3 Non-Polymeric Recyclable Hypervalent Iodine Reagents 3.1 Non-Polymeric Recyclable Hypervalent Iodine(III) Reagents 3.2 Recyclable Non-Polymeric Hypervalent Iodine(V) Reagents 3.3 Fluorous Hypervalent Iodine Reagents 4 Ionic-Liquid/Ion-Supported Hypervalent Iodine Reagents 5 Metal–Organic Framework (MOF)-Hybridized Hypervalent Iodine Reagents 6 Conclusion [ABSTRACT FROM AUTHOR]

2-Iodosylbenzoic acid in the presence of trifluoromethanesulfonic anhydride is an efficient oxidant and electrophilic reagent useful for preparation of the corresponding alkenyl and aryliodonium salts. Compared to the previously reported methods of electrophilic activation of 2-iodosylbenzoic acid, this procedure is compatible with acid-sensitive functional groups, requires mild reaction conditions, and affords products in higher yields. [ABSTRACT FROM AUTHOR]

Pseudocyclic β‐trifluorosulfonyloxy vinylbenziodoxolones were prepared starting from hydroxybenziodoxolones and alkynes in the presence of trifluoromethanesulfonic acid. The reaction of these compounds with azide anion leads to β‐azido vinylbenziodoxolones as products of vinylic nucleophilic substitution in which addition‐elimination reactions occur and the double bond configuration is retained. The structures of β‐trifluorosulfonyloxy vinylbenziodoxolone and β‐azido vinylbenziodoxolone were established by single crystal X‐ray diffraction. [ABSTRACT FROM AUTHOR]

[Display omitted] This minireview describes chemistry of hypervalent organoiodine triflates, which have received wide synthetic application as powerful electrophilic reagents and oxidants. The first representative of these compounds, μ-oxo-bis[(trifluoromethanesulfonato)(phenyl)iodine], was originally prepared and investigated in N. S. Zefirov's laboratory at Moscow State University in the early 1980s. This compound, now commonly known as Zefirov's reagent, is a useful reagent for the synthesis of various iodonium salts from the corresponding organic precursors. Recently, thermally stable and highly reactive triflates derived from cyclic hypervalent iodine compounds, benziodoxoles, have been reported and utilized in organic synthesis. The strongest iodine(V) oxidant, IBX-ditriflate, has been prepared from 2-iodoxybenzoic acid (IBX) and triflic acid. IBX-ditriflate can readily oxidize organic substrates that are generally resistant to oxidation. [ABSTRACT FROM AUTHOR]

A facile metal-free [2,3]-sigmatropic rearrangement reaction of allyl sulfides via N-sulfilimine intermediates has been developed. Treatment of allyl sulfides with imino-λ3 -iodanes in the presence of a catalytic amount of elemental iodine allowed the reaction to proceed under mild conditions and gave the corresponding N-allylsulfenamide compounds in moderate to good yields. Several N-allylsulfenamide structures have been confirmed by single-crystal X-ray crystallography. The reaction initially involves the sulfonylimino group transfer reaction between imino-λ3 -iodane and the sulfur atom, resulting in the formation of N-sulfilimine species, followed by [2,3]-sigmatropic rearrangement to form the N-allylsulfenamide. [ABSTRACT FROM AUTHOR]

[18F]Fluoroaliphatic carboxylic acids are important PET tracers that have demonstrated a considerable potential to address the fatty acid oxidation‐dependent processes in clinical patients. Herein, we report an efficient radiosynthetic approach to ω‐[18F]fluoroaliphatic carboxylic esters and acids by nucleophilic radiofluorination of the readily available iodocarboxylic esters. Methyl 6‐[18F]fluorohexanoate was further applied as a starting material for the preparation of the succinimide ester (NHS ester)‐containing bifunctional radiofluorinated prosthetic group in two simple steps, 10 min each. The synthesized NHS ester of 6‐[18F]fluorohexanoic acid can serve as an important reagent for a quick and efficient conjugation with peptides or proteins via amino groups of lysines. [ABSTRACT FROM AUTHOR]

Organohypervalent iodine reagents are widely used for the preparation of various oxazolines, oxazoles, isoxazolines, and isoxazoles. In the formation of these heterocyclic compounds, hypervalent iodine species can serve as the activating reagents for various substrates, as well as the heteroatom donor reagents. In recent research, both chemical and electrochemical approaches toward generation of hypervalent iodine species have been utilized. The in situ generated active species can react with appropriate substrates to give the corresponding heterocyclic products. In this short review, we summarize the hypervalent-iodine--mediated preparation of oxazolines, oxazoles, isoxazolines, and isoxazoles starting from various substrates. 1 Introduction 2 Synthesis of Oxazolines 3 Synthesis of Oxazoles 4 Synthesis of Isoxazolines 5 Synthesis of Isoxazoles 6 Conclusion [ABSTRACT FROM AUTHOR]

Aiming at the enhanced catalytic activity of fluoro‐λ3‐iodane generated from iodoarene precatalyst with Selectfluor and HF⋅pyridine, this study focused on the λ3‐iodanes bearing coordinating substituents. Compared to 4‐iodoanisole as a precatalyst of our previous method, N‐methyl‐2‐iodobenzamide or 2‐iodobenzamide worked well in the fluorocyclization of N‐propargyl carboxamides to oxazoles. Control experiments suggest the equilibrium mixture of iodane‐amine complexes and cyclic iodane fluorides would be involved in the present catalysis. [ABSTRACT FROM AUTHOR]

This account describes the development of organosulfonyloxy-substituted iodine(III) and iodine(V) benziodoxole derived reagents, which are thermally stable compounds with useful reactivity patterns. Iodine(III) benziodoxoles and pseudobenziodoxoles are powerful electrophiles and mild oxidants toward various unsaturated compounds. In particular, pseudocyclic benziodoxole-derived triflate (IBA-OTf) is an efficient reagent for oxidative heteroannulation reactions. Aldoximes react with nitriles in the presence of IBA-OTf at room temperature to give 1,2,4-oxadiazoles in high yields. Moreover, IBA-triflate is used as a catalyst in oxidative heteroannulations with m -chloroperoxybenzoic acid as the terminal oxidant. The iodine(V) benziodoxole derived tosylates, DMP-tosylate and IBX-tosylate, are superior oxidants for the oxidation of structurally diverse, synthetically useful alcohols, utilized as key precursors in the total syntheses of polyketide antibiotics and terpenes. And finally, the most powerful hypervalent iodine(V) oxidant, 2-iodoxybenzoic acid ditriflate (IBX·2HOTf), is prepared by treatment of IBX with trifluoromethanesulfonic acid. According to the X-ray data, the I–OTf bonds in IBX-ditriflate have ionic character, leading to the high reactivity of this reagent in various oxidations. In particular, IBX-ditriflate can oxidize polyfluorinated primary alcohols, which are generally extremely resistant to oxidation. 1 Introduction 2 Iodine(III) Benziodoxole Based Organosulfonates 3 Pseudocyclic Iodine(III) Benziodoxole Triflate (IBA-triflate) 4 Pseudocyclic Iodine(III) Benziodoxole Tosylates 5 Iodine(V) Benziodoxole Derived Tosylates 6 Iodine(V) Benziodoxole Derived Triflate (IBX-ditriflate) 7 Conclusions [ABSTRACT FROM AUTHOR]

This short introductory review provides a brief summary of history and recent developments in the field of hypervalent iodine chemistry in connection with the 7th International Conference on Hypervalent Iodine Chemistry (ICHIC-2021, Moscow, 27th June to 1st July, 2021). Hypervalent iodine reagents and catalysts are intensively used in modern organic chemistry as mild, environmentally safe, and economical alternative to heavy metal reagents. General features and applications of hypervalent iodine compounds are overviewed. [ABSTRACT FROM AUTHOR]

An efficient oxidative cycloaddition of enaminones with nitrile oxides generated in situ from respective aldoximes using hypervalent iodine reagents has been developed. Reactions of various aldoximes with enaminones in the presence of [hydroxy(tosyloxy)iodo]benzene involved the regioselective cycloaddition reaction resulting in the formation of the 3,4‐disubstituted isoxazoles in moderate to good yields. Structures of several isoxazole products were confirmed by a single X‐ray crystallography. [ABSTRACT FROM AUTHOR]

A ditriflate derivative of 2-iodoxybenzoic acid (IBX) was prepared by the reaction of IBX with trifluoromethanesulfonic acid and characterized by single crystal X-ray crystallography. IBX-ditriflate is the most powerful oxidant in a series of structurally similar IBX derivatives which is best illustrated by its ability to readily oxidize hydrocarbons and the oxidation resistant polyfluoroalcohols. [ABSTRACT FROM AUTHOR]

The article titled "Front Cover: New Isoxazole-Substituted Aryl Iodides: Metal-Free Synthesis, Characterization and Catalytic Activity" in the European Journal of Organic Chemistry discusses the synthesis and catalytic activity of isoxazole-tethered aryl iodides. These aryl iodides were synthesized through a metal-free reaction and were found to be effective catalysts for oxidative transformations such as the oxidation of hydroquinone, sulfides, and α-oxytosylation. The article highlights the excellent catalytic activity of these aryl iodides and their potential as additions to hypervalent iodine catalysis. The full research article provides more detailed information on the topic. [Extracted from the article]

As a first non‐metal‐catalyzed oxidation for the in situ generation of acylnitroso species, we describe the hypoiodite catalysis using tetra‐n‐butylammonium iodide as precatalyst with tert‐butyl hydroperoxide or hydrogen peroxide as a terminal oxidant. This method can be applied to hetero Diels–Alder (HDA) reactions with dienes and ene reactions with alkenes. Furthermore, the conversions of the representative HDA adduct to nitrone and 2‐amino alcohols were demonstrated. Compared with previous metal‐catalyzed oxidation methods, this work provides a more efficient and environmentally friendly procedure. First example of hypoiodite‐catalyzed oxidation for the in situ generation of acylnitroso species, which can be used in hetero Diels–Alder reactions with dienes and in ene reactions with alkenes. [ABSTRACT FROM AUTHOR]

A simple and convenient synthesis of ω-iodoaliphatic carboxylic acids and esters by the reaction of cyclic ketones with iodine and hydrogen peroxide in the presence of catalytic CuCl has been developed. ω-Iodoaliphatic carboxylic esters were further used for the efficient preparation of di(2-pyridylmethylamino)alkanoic acids in excellent yields. [ABSTRACT FROM AUTHOR]

Reactions involving benzyne and aryne intermediates have found widespread application in organic synthesis. Various benzyne precursors and benzyne generating procedures are known. Recently, methods of benzyne generation from diaryliodonium salts and related hypervalent iodine compounds have received considerable attention. These methods are characterized by mild reaction conditions and applicability in a broad range of chemical transformations. The present minireview is focused on the preparation and reactivity of hypervalent iodine based benzyne precursors. Furthermore, recent developments in their synthetic application are discussed. Diaryliodonium derivatives can be effectively used for generation of benzyne via decarboxylation, deprotonation, desilylation or deboronation. These reactions are characterized by mild reaction conditions and applicability in a broad range of chemical transformations. In particular, pseudocyclic arylbenziodoxaborole triflates can readily generate aryne intermediates upon treatment with water at room temperature. [ABSTRACT FROM AUTHOR]

Phenol based aryliodonium salts were prepared by the reaction of [hydroxy(tosyloxy)iodo]arenes with aryl silyl ethers in the presence of trifluoromethanesulfonic acid. Structures of several aryliodonium salts with the hydroxy group in the para-position of the phenyl ring were established by single crystal X-ray crystallography. Under basic conditions, 4-hydroxyphenyl(phenyl)iodonium salts form a dimeric hypervalent iodine(iii) complex, oxyphenyl(phenyl)iodonium ylidic salt, the solid structure of which was confirmed by X-ray crystallography. Phenolic iodonium salts are potentially useful phenol transfer reagents in reactions with various anionic nucleophiles. [ABSTRACT FROM AUTHOR]

New substituted 1-arylbenziodoxolones were prepared and their reactivity with azide anion as a nucleophile was investigated. It was found that independent of the presence of substituents, all reactions of 1-arylbenziodoxolones proceed as nucleophilic substitution of the iodonium leaving group in the electron-deficient benziodoxolone benzene ring. The presence of bulky substituents in the ortho position of the aryl ring slows the reaction down, while the presence of a moderately electron- withdrawing bromine substituent in para position to the iodine atom in the benziodoxolone ring moderately increases the rate of substitution. The presence of a strongly electronwithdrawing nitro group in the para position to the iodine atom in the benziodoxolone ring dramatically increases the rate of substitution. These observations are in agreement with the electronic requirements for internal nucleophilic substitution in the benziodoxole ring. A quantum-chemical computational study of the possible reaction paths is in agreement with the observed effects of substituents on the reactivity of arylbenziodoxolones in this reaction. [ABSTRACT FROM AUTHOR]

New organohypervalent iodine compounds, arylbenziodoxaborole triflates, were prepared from 1-acetoxybenziodoxaboroles and arenes by treatment with trifluoromethanesulfonic acid under mild conditions. Single crystal X-ray crystallography of these compounds revealed a pseudocyclic structure with a short intramolecular interaction of 2.698 to 2.717 Å between oxygen and iodine in the benziodoxaborole ring. These new pseudocyclic aryliodonium salts readily generate aryne intermediates upon treatment with water at room temperature. The generated aryne intermediates react with various substrates to give the corresponding aryne adducts in moderate to good yields. Furthermore, the new benzyne precursors can also work as arylating reagents towards aromatic rings. The aryne intermediates generated from arylbenziodoxaborole triflates selectively react with tert-butyl phenol forming products of ortho arylation in moderate yields. [ABSTRACT FROM AUTHOR]

Aiming at the enhancement of electrophilicity of imino-λ3-iodanes, we have developed (tosylimino)pentafluorophenyl-λ3-iodane, which shows superior reactivity compared to the commonly used (tosylimino)phenyl-λ3-iodane in the [2+2+1]-type synthesis of imidazoles. [ABSTRACT FROM AUTHOR]

(Diacetoxyiodo)benzene or iodine(III) catalyst, in situ generated from iodobenzene precatalyst with Oxone, promotes the cycloisomerization-amination sequence of N-propargyl carboxamides with bis(sulfonyl)imides under mild conditions, thereby leading to the direct formation of oxazoles bearing nitrogen functional groups. [ABSTRACT FROM AUTHOR]

Two powerful hypervalent iodine(V) oxidants, DMP-OTs (1-tosyloxy-1,1-diacetoxy-1 H-1λ5-benzo[ d][1,2]iodoxol-3-one) and IBX-OTs (1-tosyloxy-1-oxo-1 H-1λ5-benzo[ d][1,2]iodoxol-3-one) show high reactivity in the oxidation of structurally complex primary and secondary alcohols, which are highly functionalized polyketide or terpene fragments or steroids. The yields of the corresponding carbonyl compounds are even higher for the protocol that uses pyridine as additive. The oxidations proceed very rapidly at room temperature leaving the protective groups and π-systems intact and affording the corresponding carbonyl compounds in good to excellent yields. Moreover, IBX-OTs is an efficient reagent for the oxidative dehydrogenation of steroidal alcohols to the corresponding enones. [ABSTRACT FROM AUTHOR]

Keywords: iodine; iodine heterocycles; hypervalent iodine; benziodoxole; ligand transfer EN iodine iodine heterocycles hypervalent iodine benziodoxole ligand transfer 2651 2651 1 08/25/23 20230815 NES 230815 The front cover picture, designed by Yoshimura, illustrates applications of benziodoxoles as group transfer reagents. Iodine, iodine heterocycles, hypervalent iodine, benziodoxole, ligand transfer Cyclic hypervalent iodine compounds based on the benziodoxole system have higher stability compared to their acyclic analogues, which makes possible the preparation and safe handling of the reagents with special ligands such as azido, cyano, and trifluoromethyl groups. [Extracted from the article]

New pseudocyclic benziodoxole tosylates were prepared by the treatment of 1-hydroxybenziodoxolones with p-toluenesulfonic acid or via ligand transfer reaction between PhI(OH)OTs (Koser's reagent) and substituted 2-iodobenzoic acids under mild condition. Single crystal X-ray crystallography of these compounds revealed a pseudocyclic structure with a short intramolecular interaction of 2.362 Å between oxygen and iodine in the iodoxole ring. Pseudocyclic benziodoxole tosylates readily react with various organic substrates as electrophiles or oxidants to afford the corresponding iodonium salts or the products of oxidation. Furthermore, these compounds can be used as efficient recyclable hypervalent iodine reagents. The reduced form of a pseudocyclic benziodoxole tosylate, 2-iodobenzoic acid, can be efficiently recovered from the reaction mixture by a simple acid-base liquid-liquid biphasic procedure. [ABSTRACT FROM AUTHOR]