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A transition metal‐free approach for the N‐arylation of amino acid derivatives has been developed. Key to this method is the use of unsymmetric diaryliodonium salts with anisyl ligands, which proved important to obtain high chemoselectivity and yields. The scope includes the transfer of both electron deficient, electron rich and sterically hindered aryl groups with a variety of different functional groups. Furthermore, a cyclic diaryliodonium salt was successfully employed in the arylation. The N‐arylated products were obtained with retained enantiomeric excess., A transition metal‐free N‐arylation of amino esters is reported, where the use of unsymmetric aryl(anisyl) iodonium salts is key to obtain high yields. The scope includes arylation with electron deficient, electron rich, and sterically hindered aryl groups. Various functional groups are tolerated, and no racemization is generally observed.

The iodine(III) reagents vinylbenziodoxolones (VBX) were employed to vinylate a series of aliphatic and aromatic thiols, providing E‐alkenyl sulfides with complete chemo‐ and regioselectivity, as well as excellent stereoselectivity. The methodology displays high functional group tolerance and proceeds under mild and transition metal‐free conditions without the need for excess substrate or reagents. Mercaptothiazoles could be vinylated under modified conditions, resulting in opposite stereoselectivity compared to previous reactions with vinyliodonium salts. Novel VBX reagents with substituted benziodoxolone cores were prepared, and improved reactivity was discovered with a dimethyl‐substituted core., Novel vinylation reagent: The iodine(III) reagents vinylbenziodoxolones (VBX) have been employed to vinylate aliphatic and aromatic thiols, as well as mercaptothiazoles. The methodology proceeds under mild and transition metal‐free conditions to provide alkenyl sulfides with excellent stereoselectivity. A novel VBX reagent with a substituted benziodoxolone core had superior efficiency.

The reactions of thioamides with ortho-nitro-substituted iodonium ylides proceeded under mild conditions to give enaminones or thiazoles, depending on the iodonium ylide used. This protocol allowed the use of protic solvents, including aqueous solutions, and therefore coupling reactions with complex molecules such as peptides or steroids were possible. A mild and efficient method for the synthesis of various iodonium ylides was established. DFT calculations suggested that the halogen bonding between a thioamide and iodonium ylide was important in this chemoselective coupling reaction. The potential use of enaminones conjugated with pharmaceuticals as prodrugs was also demonstrated.

Cyclic hypervalent iodine reagents are now frequently used in synthetic organic chemistry, either as oxidants or group-transfer reagents. Vinylbenziodoxol(on)es (VBXs) bearing alkene substituents have been less investigated than the corresponding trifluoromethyl or alkynyl reagents. Nevertheless, since 2016 the development of new synthetic methods to access VBXs has awakened the interest of the synthetic community, leading to new transformations highlighting their unique reactivity as electrophilic alkene synthons. In this review, an overview of the synthesis and applications of VBX reagents will be presented. The review is organized according to the two main classes of VBX reagents reported so far - simple alkyl/aryl-substituted VBXs and heteroatom (S, O, N, X)-substituted VBXs - as they differ significantly from the point of view of synthetic access.

Demonstrated herein is the construction of trifluoromethylated quaternary carbon centers by an asymmetric radical transformation. Enantioenriched trifluoromethylated oxindoles were accessed using a hypervalent iodine-based trifluoromethyl transfer reagent in combination with a magnesium Lewis acid catalyst and PyBOX-type ligands to achieve up to 99 % ee and excellent chemical yields. Mechanistic studies were performed by experimental and computational methods and suggest a single-electron transfer induced SN2-type mechanism. This example is thereby the first report on the construction of enantioenriched trifluoromethylated carbon centers using hypervalent iodine-based reagents proceeding through such a reaction pathway. ISSN:1433-7851 ISSN:1521-3773 ISSN:0570-0833

A metal‐free and direct alkene C−H cyanation is described. Directing groups are not required and the mechanism involves electrophilic activation of the alkene by a cyano iodine(III) species generated in situ from a [bis(trifluoroacetoxy)iodo]arene and trimethylsilyl cyanide as the cyanide source. This C−H functionalization can be conducted on gram scale, and for noncyclic 1,1‐ and 1,2‐disubstuted alkenes high stereoselectivity is achieved, thus rendering the method highly valuable.

The treatment of phenyl-protected pentafluoroethylstannanes, Sn(C2F5)(4-n)Ph-n (n = 1-3), with anhydrous HF results in the formation of the corresponding fluorostannanes which are associated in the solid state but form monomeric and dimeric fluoride complexes in solution. Due to the pronounced Lewis acidity caused by the electron-withdrawing pentafluoroethyl groups, these stannanes represent suitable precursors for the synthesis of neutral, monoanionic and dianionic hexacoordinate tin(IV) complexes. The employment of an excess of cesium fluoride and 1,10-phenanthroline exclusively leads to the octahedral complexes [Sn(C2F5)(n)F6-n](2-) (n = 2-4) and [Sn(C2F5)(n)F4-n(phen)] (n = 1-3). The addition of bases, donating solvents as well as LiF, on the other hand, selectively affords salts containing dinuclear anions of the form [(C2F5)(3)Sn(mu-F)(3)Sn(C2F5)(3)](-) and [(C2F5)(2)F2Sn(mu-F)(2)SnF2(C2F5)(2)](2-).

Described herein is an effective and practical modular flow design for the meta‐selective C−H arylation of anilines. The design consists of four continuous‐flow modules (i.e., diaryliodonium salt synthesis, meta‐selective C−H arylation, inline copper extraction, and aniline deprotection) which can be operated either individually or consecutively to provide direct access to meta‐arylated anilines. With a total residence time of 1 hour, the desired product could be obtained in high yield and excellent purity without the need for column chromatography, and the residual copper content meets the standards for parenterally administered pharmaceutical substances.

Reactions of SiCl4 with R2PO(OH) (R=Me, Cl) yield compounds with six‐fold coordinated silicon atoms. Whereas R=Me afforded the hexacoordinated tetra‐cationic silicon complex [Si(Me2PO(OH))6]4+ with chloride counter‐ions, R=Cl caused release of HCl with formation of a cyclic dimeric silicon complex [Si(Cl2PO(OH))(Cl2PO2)3(μ‐Cl2PO2)]2 with bridging bidentate dichlorophosphates., Ionic dissociation of SiCl4: The first example of a structurally characterized tetra‐cationic hexacoordinated silicon tetrachloride is reported. It was obtained by reaction of dimethylphosphinic acid with SiCl4 under ambient conditions. Additionally, the structure of a cyclic dimeric hexacoordinated silicon complex was determined by single‐crystal X‐ray diffraction and verified by solid‐state NMR spectroscopy.

This review article describes the chemistry of transition-metal complexes containing heavier Group 14 elements (Si, Ge, and Sn) as the σ-electron acceptor (Z-type) ligands and discusses the characteristics of bonds between the transition metal and Z-type ligand. Moreover, we review the iridium-hydride-mediated cleavage of E−X bonds (E = Si, Ge; X = F, Cl), where the key intermediates are pentacoordinate silicon or germanium compounds bearing a dative M→E bond.

A palladium(II)-catalyzed γ-C-H amination of cyclic alkyl amines to deliver highly substituted azetidines is reported. The use of a benziodoxole tosylate oxidant in combination with AgOAc was found to be crucial for controlling a selective reductive elimination pathway to the azetidines. The process is tolerant of a range of functional groups, including structural features derived from chiral α-amino alcohols, and leads to the diastereoselective formation of enantiopure azetidines.

Hypervalent iodine compounds are privileged reagents in organic synthesis because of their exceptional reactivity. Among these compounds, cyclic derivatives stand apart because of their enhanced stability. They have been widely used as oxidants, but their potential for functional-group transfer has only begun to be investigated recently. The use of benziodoxol(on)es for trifluoromethylation (Togni's reagents) is already widely recognized, but other transformations have also attracted strong interest recently. In this Review, the development in the area since 2011 will be presented. After a short summary of synthetic methods to prepare benziodoxol(on)e reagents, their use to construct carbon-heteroatom and carbon-carbon bonds will be presented. In particular, the introduction of alkynes by using ethynylbenziodoxol(on)e (EBX) reagents has been highly successful. Breakthroughs in the introduction of alkoxy, azido, difluoromethyl, and cyano groups will also be described.

International audience; The long-standing quest for chiral hypervalent organoiodine compounds (i.e., iodanes) as metal-free reagents for asymmetric synthesis continues. Although remarkable progress has recently been made in organoiodine-catalyzed reactions using a terminal oxidant in stoichiometric amounts, there is still a significant need for “flaskable” chiral iodane reagents. Herein, we describe the synthesis of new iodobinaphthyls and iodobiphenyls, their successful and selective DMDO-mediated oxidation into either λ3- or λ5-iodanes, and the evaluation of their capacity to promote asymmetric hydroxylative phenol dearomatization (HPD) reactions. Most notably, a C2-symmetrical biphenylic λ5-iodane promoted the HPD-induced conversion of the monoterpene thymol into the corresponding ortho-quinol-based [4+2] cyclodimer (i.e., bis(thymol)) with enantiomeric excesses of up to 94 %.

Over the last fifteen years, gold has been raised from the status of an inert noble metal to one of the most-often-used catalysts in synthetic chemistry. The functionalization of the triple bond of alkynes has been especially successful in this respect. In contrast, gold-catalyzed alkynylation reactions only began to emerge in 2007. Since then, three different approaches have been successfully used for this transformation. 1) Gold nanoparticles have been shown to promote catalytic cycles based on the oxidative arylation of aryl halides to give a palladium-free Sonogashira reaction. 2) The use of benziodoxol(on)e hypervalent iodine compounds as oxidative alkynylation reagents has allowed the CH functionalization of electron-rich heterocycles under mild conditions with a very broad functional-group tolerance. 3) The use of iodobenzene acetate or Selectfluor as an external oxidant has led to the first alkynylation methods based on direct CH/CH coupling reactions. In only six years, gold-catalyzed alkynylation methods have grown from non-existent to useful synthetic procedures for the synthesis of structurally diverse alkynes. Considering that acetylenes are among the most-important building blocks for applications in synthetic chemistry, chemical biology, and materials science, there is tremendous potential for the further development of gold-catalyzed alkynylation reactions in the future.

Phenols, anilines, and malonates have been arylated under metal-free conditions with twelve aryl(phenyl)iodonium salts in a systematic chemoselectivity study. A new "anti-ortho effect" has been identified in the arylation of malonates. Several "dummy groups" have been found that give complete chemoselectivity in the transfer of the phenyl moiety, irrespective of the nucleophile. An aryl exchange in the diaryliodonium salts has been observed under certain arylation conditions. DFT calculations have been performed to investigate the reaction mechanism and to elucidate the origins of the observed selectivities. These results are expected to facilitate the design of chiral diaryliodonium salts and the development of catalytic arylation reactions that are based on these sustainable and metal-free reagents.

A new reaction for the rhodium‐catalyzed geminal‐difunctionalization‐based fluorination is presented. The substrates are aromatic and aliphatic diazocarbonyl compounds. As the fluorine source a stable and easily accessible benziodoxole reagent was used. A variety of alcohol, phenol, and carboxylic acid reagents were employed to introduce the second functionality. The reaction was extended to trifluoromethylation using a benziodoxolon reagent. The fluorination and trifluoromethylation reactions probably proceed by a rhodium‐containing onium ylide type intermediate, which is trapped by either the F or CF3 electrophiles.

Keywords: asymmetric synthesis ; enantioselectivity ; hypervalent compounds ; iodine ; organocatalysis ; Diaryliodonium Salts ; Beta-Ketoesters ; Ketones ; Arylation ; Aldehydes ; Iodoarenes ; Oxidation ; Reagents ; Trifluoromethylation Reference EPFL-ARTICLE-180009doi:10.1002/cctc.201200116View record in Web of Science Record created on 2012-07-13, modified on 2017-12-03

1,1,1,2,2,4,4,5,5,5-Decafluoro-3-phenyl-3-pentanol (13) was prepared via the Cannizzaro-type disproportionation reaction, and dimetallated 13 (i.e., 15) was used as a bidentate ligand, which was bulkier than the Martin ligand (1,1,1,3,3,3-hexafluoro-2-phenyl-2-propanol). P-H spirophosphorane (16) was synthesized utilizing the new bidentate ligand, and the structure of 16 was essentially the same as that of the P-H phosphorane with the Martin ligands (1b). Phosphoranes which exhibit reversed apicophilicity (9: O-equatorial) were also synthesized and could be converted to the corresponding stable stereoisomers (10: O-apical). The crystal structures of O-equatorial phosphoranes (9) and those of O-apical isomers (10) were slightly affected by the steric repulsion of pentafluoroethyl groups. Kinetic measurements revealed that the stereomutation of O-equatorial methylphosphorane (9a) to the O-apical isomer (10a) was slowed. The activation enthalpy for the stereomutation of 9a→10a (24.4 kcal mol–1) was higher than that of the phosphorane bearing the Martin ligands (3a→4a: 19.3 kcal mol–1) by 5.1 kcal mol–1.

International audience; This works introduces hypervalent bis-catecholato silicon compounds as versatile sources of alkyl radicals upon visible-light photocatalysis. Using Ir[(dF(CF3)ppy)(2)(bpy)]-(PF6) (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine, bpy = bipyridine) as catalytic photooxidant, a series of alkyl radicals, including highly reactive primary ones can be generated and engaged in various intermolecular homolytic reactions. Based on cyclic voltammetry, Stern-Volmer studies, and supported by calculations, a mechanism involving a single-electron transfer from the silicate to the photoactivated iridium complex has been proposed. This oxidative photocatalyzed process can be efficiently merged with nickel-catalyzed C-sp2-C-sp3 cross-coupling reactions.

The reaction of benzothiadiphosphole 1 with an equimolar mixture of R 1 MgBr and R 2 MgBr gave intermediate A¢, which, after only 4-5 min, was treated with an equimolar amount of R 3 MgBr, giving the asymmetric phosphine PR 1 R 2 R 3 in 45% overall yield (75-80% yield when R 1 ) R 2 and 85-90% yield when R 1 ) R 2 ) R 3 ) and the byproduct 6 in 90% yield. The treatment of 6 with PCl3 quantitatively regenerates the starting reagent 1. Treatment of the phosphines with elemental sulfur gave the corresponding sulfides.

Indoles are omnipresent in natural products, bioactive molecules, and organic materials. Consequently, their synthesis or functionalization are important fields of research in organic chemistry. Most works focus on installation or modification of the pyrrole ring. To access benzene-ring-functionalized indoles with an unsubstituted pyrrole ring remains more challenging. Reported herein is a platinum-catalyzed cyclization/alkynylation domino process to selectively obtain C5- or C6-functionalized indoles starting from easily available pyrroles. The work combines, for the first time, a platinum catalyst with ethynylbenziodoxole hypervalent iodine reagents in a domino process for the synthesis of polyfunctionalized arene rings and gives access to important building blocks for the synthesis of bioactive compounds and organic materials.

Phosphanes: No pain, all gain. A regenerable phosphorus donor is the key to an efficient and economic one-pot synthesis of five- and six-membered secondary cyclic phosphanes. The reaction, at room temperature, of 1 with 1 equivalent of bis(Grignard reagent) 2 followed by treatment with aqueous acid gives cyclic phosphanes 3 in 70-80 % yield and the new compound 4. Simply treating 4 with PCl3 quantitatively regenerates the starting reagent 1, which can be reused without further purification.

Alkynes and nitriles are valuable building blocks in organic synthesis and also have multiple applications in chemical biology and materials science. Due to the high availability of tertiary alcohols, developing methods for their conversion into alkynes and nitriles is particularly attractive. In a previous communication, our group has reported the conversion of alcohols into alkynes through cesium oxalates based on the powerful combination of photochemistry with Ethynyl BenziodoXolones (EBXs). Herein, we report further investigations into this transformation, including our findings on the effect that backbone modification of EBXs has on the deoxyalkynylation of cesium oxalates. In addition, we disclose preliminary data on the development of new deoxycyanation and dethioalkynylation processes. We also report the serendipitous discovery of the C-H alkynylation of 1,2-dichloroethane.

First synthesized in 1991, EthynylBenziodoXolones (EBXs) - cyclic hypervalent iodine reagents derived from 2-iodobenzoic acid - are now among the most versatile electrophilic alkynylation reagents. Due to their cyclic structure, these reagents exhibit enhanced stability compared to previously used alkynyl iodonium salts. Over the last decade, both the iodoheterocycle and the arene ring have been extensively modified to fine-tune the reactivity of the reagents, resulting in new analogues such as Ethynylbenziodoxoles (EBxs) or N-heterocyclic reagents. In this article, we have for the first time compiled the structural data available for EBXs and their analogues, focusing especially on X-Ray and NMR data. For selected compounds, molecular electrostatic potentials (MEP) have also been calculated. When considering the tight relationship between structure and reactivity in hypervalent iodine reagents, the collected data is expected to be highly useful for further developments in the field.