Iodine(III) Reagents in Radical Chemistry

Palladium/Light Induced Radical Alkenylation and Allylation of Alkyl Iodides Using Alkenyl and Allylic Sulfones

Alkenylation and allylation of alkyl iodides with alkenyl and allyl sulfones, respectively, took place under Pd/photoirradiation system. The initial alkyl radical, derived from a single electron transfer between Pd(0) and RI, underwent the title transformations. Pd(0) was regenerated through a reductive elimination of PhSO₂PdI, which is formed by the combination of the sulfonyl radical and the palladium radical. The addition of water was effective, presumably by pushing the equilibrium through hydrolysis of PhSO₂I.

Selective P-C(sp3 ) Bond Cleavage and Radical Alkynylation of α-Phosphorus Alcohols by Photoredox Catalysis

Herein the first P-C(sp³ ) bond cleavage and radical alkynylation of α-phosphorus alcohols to construct phosphonoalkynes is reported. The phosphorus radical is generated upon P-C bond cleavage reaction via the alkoxyl radical through photoredox catalysis with cyclic iodine(III) reagents. Various arylphosphinoyl-, alkylphosphinoyl-, phosphonate-, and phosphonic amide alcohols serve as radical phosphorus precursors to construct phosphonoalkynes for the first time.

Site-selective synthesis of functionalized dibenzo[f,h]quinolines and their derivatives involving cyclic diaryliodonium salts via a decarboxylative annulation strategy

An unprecedented site-selective synthesis of dibenzo[f,h]quinolines and their derivatives was reported via an acid directed decarboxylative annulation cascade.

A metal-free direct C (sp3)–H cyanation reaction with cyanobenziodoxolones

Metal-free direct C(sp³)–H cyanation reaction: cyanobenziodoxolones as cyanating reagents and oxidants.

Nickel(ii)-catalyzed enantioselective α-alkylation of β-ketoamides with phenyliodonium ylideviaa radical process

Enantioselective α-alkylation of β-ketoamides with iodonium ylide was realizedviaa radical process. In the presence of a chiralN,N′-dioxide/Ni(OTf)₂complex, the corresponding products were obtained with good results. Control experiments and EPR studies supported a radical process.

A strategy for generating aryl radicals from arylborates through organic photoredox catalysis: photo-Meerwein type arylation of electron-deficient alkenes

Generation of a variety of aryl radicals from arylboronic acids through metal-free photoredox catalysis under mild conditions.

PhI(OAc)2-mediated dearomative C–N coupling: facile construction of the spiro[indoline-3,2′-pyrrolidine] skeleton

A facile construction of the spiro[indole-3,2′-pyrrolidine] skeleton, through diacetoxyiodobenzene (PIDA) mediated C–N bond-forming dearomatization of C3 sulfonamide linked indole derivatives, has been developed.

Catalytic, metal-free sulfonylcyanation of alkenes via visible light organophotoredox catalysis

A catalytic, redox-neutral group transfer radical addition of olefins with tosyl cyanide via visible light-induced organophotoredox catalysis has been described.

Bromide-catalyzed electrochemical trifluoromethylation/cyclization of N-arylacrylamides with low catalyst loading

An electro-generated trifluoromethyl radical mediated by a bromide ion is efficiently applied to the trifluoromethylarylation/cyclization of N-arylacrylamides.

Regio- and Stereoselective Iron-Catalyzed Oxyazidation of Enamides Using a Hypervalent Iodine Reagent

A novel regio- and diastereoselective iron-catalyzed intermolecular oxyazidation of enamides using various azidobenziodoxolone (ABX) derivatives is presented. A variety of α-N₃ amino derivatives and of α-N₃ piperidines were synthesized in good yields and under mild reaction conditions. The reaction involves a radical process using cheap FeCl₂ as the initiator.

Atom-Transfer Radical Addition to Unactivated Alkenes by using Heterogeneous Visible-Light Photocatalysis

Heterogeneous visible-light photocatalysis represents an important route toward the development of sustainable organic synthesis. In this study visible light-induced, heavy metal-free atom-transfer radical addition to unactivated terminal olefins is carried out by using the combination of heterogeneous titanium dioxide as photocatalyst and a hypervalent iodine(III) reagent as co-initiator. The reaction can be applied to a range of substrates with good functional-group tolerance under very mild conditions. In addition to a number of commonly used atom-transfer reagents, the relatively challenging chloroform is also suitable.

Benziodoxole Triflate as a Versatile Reagent for Iodo(III)cyclization of Alkynes

The utility of benziodoxole triflate, derived from α,α-bis(trifluoromethyl)-2-iodobenzyl alcohol, as a versatile reagent for iodo(III)cyclization via electrophilic activation of alkyne, is reported herein. The reagent promotes cyclization of alkynes tethered to a variety of nucleophilic moieties, affording benziodoxole-appended (hetero)arenes such as benzofurans, benzothiophenes, isocoumarins, indoles, and polyaromatics under mild conditions. This unprecedented class of (hetero)aryl-I^III compounds proved easy to purify, stable, and amenable to various synthetic transformations.

Iodosylbenzene-Pseudohalide-Based Initiators for Radical Polymerization

Iodosylbenzene reacts with various (pseudo)halides (trimethylsilyl azide or isocyanate or potassium azide, cyanate, and bromide) to yield unstable hypervalent iodine(III) compounds, PhIX₂ (X = (pseudo)halide), that undergo rapid homolysis of the hypervalent I-X bonds and generate (pseudo)halide radicals, which can initiate the polymerization of styrene, (meth)acrylates, and vinyl esters. Polymers are formed containing (pseudo)halide functionalities at the α-chain end but, depending on the termination mechanism and the occurrence of transfer of (pseudo)halide groups from the initiator to the propagating radicals, also at the ω-chain end. With slowly polymerizing monomers (styrene and methyl methacrylate) and initiators that were generated rapidly at high concentrations and were especially unstable, the reactions proceeded via a "dead-end" polymerization mechanism, and only low to moderate monomer conversions were attained. When the initiator was generated more slowly and continuously throughout the polymerization (using the combination of iodosylbenzene with the poorly soluble potassium (pseudo)halide salts), typically higher conversions and higher molecular weights were reached. The presence of (pseudo)halide functionalities in the polymers was proved by elemental analysis, IR, and NMR spectroscopy. The azide-containing polymers underwent click-type coupling reactions with dialkynes, while the (iso)cyanate-containing polymers reacted with diamines to afford high-molecular-weight polymers with triazole- and urea-type interchain links, respectively.

Co(OAc)2-Catalyzed Trifluoromethylation and C(3)-Selective Arylation of 2-(Propargylamino)pyridines via a 6-Endo-Dig Cyclization

A Co(OAc)₂-catalyzed trifluoromethylation and subsequent C(3)-selective arylation of 2-(propargylamino)pyridines has been developed. A new 6-endo-dig cyclization involving an unprecedented C(3) selective arylation of the pyridines instead of a commonly observed 5-exo-dig cyclization with "N" is realized. Moreover, the study presents the first case of the installation of a trifluoromethyl group into electron-deficient azaarenes. The process delivers an efficient cascade approach to new trifluoromethylated 1,8-naphthyridine structures with a broad substrate scope.

Hypervalent Iodine Mediated Chemoselective Iodination of Alkynes

Reported herein are practical approaches for the chemoselective mono-, di-, and tri-iodination of alkynes based on efficient oxidative iodinations catalyzed by hypervalent iodine reagents. The reaction conditions were systematically optimized by altering the iodine source and/or the hypervalent iodine reagent system. The tetrabutylammonium iodide (TBAI)/(diacetoxyiodo)benzene (PIDA) system is specific for monoiodination, while the KI/PIDA system results in di-iodination. Combining the TBAI/PIDA and KI/PIDA systems in one pot provided the corresponding tri-iodination products efficiently. These reaction conditions can be applied to the synthetically important iodination of aromatic and aliphatic alkynes, which was accomplished in good yield (up to 99%) and excellent chemoselectivity. These synthetic methods can also be applied to the efficient chemoselective synthesis of iodoalkyne derivatives, intermediates, and related biologically active compounds.

Metal-free intermolecular cyclopropanation between alkenes and iodonium ylides mediated by PhI(OAc)2·Bu4NI

A simple and highly effective synthesis of poly substituted cyclopropanes was developed. This metal-free intermolecular reaction between iodonium ylides and alkenes is mediated by PhI(OAc)₂ and Bu₄NI.