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The synthesis of substituted 1,4-benzoquinones, a biologically important class of compounds, was developed using μ-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.

The iodine(III) catalyst, in situ generated from iodoarene as a precatalyst with m-CPBA and Tf2NH, promoted the metal-free [2 + 2 + 1] cycloaddition-type reactions of alkynes, nitriles, and oxygen atoms for the regioselective formations of 2,4-disubstituted and 2,4,5-trisubstituted oxazole. A first example of iodine catalysis for multicomponent reactions is represented.

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 using hypervalent iodine compounds as an environmentally sustainable alternative to heavy metals.

New experimental procedures for the preparation of dibenziodolium salts by oxidative cyclization of 2-iodobiphenyl in the presence of appropriate strong acids are described. Particularly useful is a convenient one-pot synthesis of dibenziodolium hydrogen sulfate from 2-iodobiphenyl using Oxone as an inexpensive and environmentally safe oxidant. Dibenziodolium hydrogen sulfate, bis(triflyl)imidate, or triflate can be readily converted to various other dibenziodolium derivatives (chloride, bromide, thiocyanate, azide, cyanide, phenylsulfinate) by anion exchange. Structures of key products have been established by single-crystal X-ray diffraction analysis. Particularly interesting is the X-ray structure of dibenziodolium thiocyanate, which represents the first example of a structurally characterized hypervalent iodine compound with a relatively short iodine-sulfur secondary bond distance.

Hypervalent iodine catalyzed oxidation of aldoximes using oxone as a terminal oxidant generates nitrile oxides, which react with alkenes and alkynes to give the corresponding isoxazolines and isoxazoles in moderate to good yields. This reaction involves active hypervalent iodine species formed in situ from catalytic iodoarene and oxone in the presence of hexafluoroisopropanol in aqueous methanol solution.

Hofmann rearrangement of carboxamides to carbamates using Oxone as an oxidant can be efficiently catalyzed by iodobenzene. This reaction involves hypervalent iodine species generated in situ from catalytic amount of PhI and Oxone in the presence of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) in aqueous methanol solutions. Under these conditions, Hofmann rearrangement of various carboxamides affords corresponding carbamates in high yields.

The preparation, X-ray structure, and reactivity of new, highly soluble, and reactive iodonium ylides derived from malonate methyl ester and bearing an ortho substituent on the phenyl ring are reported. These new reagents show higher reactivity than common phenyliodonium ylides in the Rh-catalyzed cyclopropanation, C-H insertion, and transylidation reactions under homogeneous conditions.

A series of heterocyclic compounds containing trivalent iodine, oxygen, and boron in a five-membered ring were prepared and structurally investigated by X-ray crystallography. 1-Chloro-4-fluoro-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol was synthesized by chlorination of 2-fluoro-6-iodophenylboronic acid followed by treatment of the intermediate iododichloride with water. 1-Acetoxy-4-fluoro-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol, 1-acetoxy-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol, and similar 1-substituted trifluoroacetate derivatives of benziodoxaborole were prepared the hypochlorite oxidation of 2-fluoro-6-iodophenylboronic acid or 2-iodophenylboronic acid in acetic or trifluoroacetic acid, respectively. 1-Acetoxy substituted benziodoxaborole can be further converted to the respective trifluoroacetate by treatment with trifluoroacetic acid or to the 1-hydroxy derivative by basic hydrolysis with aqueous NaHCO(3). X-ray structural studies of 1-chloro- and 1-trifluoroacetoxy substituted benziodoxaboroles 13, 17, and 18 have shown the presence of a planar five-membered heterocyclic ring with unusually short endocyclic I-O bond distance of 2.04-2.09 Å. Slow crystallization of 4-fluoro-1-trifluoroacetoxy-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol from methanol resulted in the formation of a tetrameric macrocyclic structure 21 resulting from self-assembly of the initially formed 4-fluoro-1,3-dimethoxy-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol. Structural parameters of the five-membered iodoxoborol ring, such as the planar geometry and the short B-O and O-I bonds lengths in 13, 17, and 18 compared to those in 21 and known benziodoxoles are indicative of partially aromatic character of this ring. Density functional theory (DFT) predicted NIST (0) and NIST (1) indexes for 1-chloro- and 1-trifluoroacetoxy substituted benziodoxaboroles, however, are indicative of significantly lower aromaticity compared to the classic aromatic systems.

2-Iodylpyridine and four examples of 3-alkoxy-2-iodylpyridines were prepared by oxidation of the respective 2-iodopyridines with 3,3-dimethyldioxirane. Structures of 2-iodylpyridine, 2-iodyl-3-isopropoxypyridine, and 2-iodyl-3-propoxypyridine were established by single-crystal X-ray diffraction analysis. 2-Iodyl-3-propoxypyridine has moderate solubility in organic solvents (e.g., 1.1 mg/mL in acetonitrile) and can be used as a recyclable reagent for oxidation of sulfides and alcohols. The reduced form of this reagent, 2-iodo-3-propoxypyridine, can be effectively separated from the reaction mixture by treatment with diluted sulfuric acid and recovered from the acidic aqueous solution by adding aqueous sodium hydroxide.

Organohypervalent iodine reagents have attracted significant recent interest as versatile and environmentally benign oxidants with numerous applications in organic synthesis. This Perspective summarizes synthetic applications of hypervalent iodine(V) reagents: 2-iodoxybenzoic acid (IBX), Dess-Martin periodinane (DMP), pseudocyclic iodylarenes, and their recyclable polymer-supported analogues. Recent advances in the development of new catalytic systems based on the generation of hypervalent iodine species in situ are also overviewed.

New tosyl derivatives of 2-iodylaniline and 2-iodylphenol were prepared by the dimethyldioxirane oxidation of the corresponding 2-iodophenyltosylamides or 2-iodophenyl tosylate and isolated as stable, microcrystalline products. Single-crystal X-ray diffraction analysis of N-(2-iodylphenyl)-N,4-dimethylbenzenesulfonamide revealed pseudocyclic structure formed by intramolecular I...O interactions between the hypervalent iodine center and the sulfonyl oxygens in the tosyl group. This tosylamide has an excellent solubility in organic solvents and is a potentially useful hypervalent iodine oxidant.

The treatment of [(diacetoxy)iodo]benzene with sodium bisulfate leads to the formation of oligomeric cationic species resulting from self-assembly of hydroxy(phenyl)iodonium ions, [PhIOH](+), in an aqueous acidic media. Depending on the PhI(OAc)(2):NaHSO(4) ratio, three new oligomeric products have been isolated and characterized by X-ray crystallography. The treatment of 5 equiv of PhI(OAc)(2) with 1 equiv of NaHSO(4).H(2)O affords the previously unknown mu-oxo-[bis(acetoxy)iodo]benzene, PhI(OAc)OI(OAc)Ph, which was structurally characterized by X-ray crystallography. In the solid-state, this mu-oxo product forms an isolated diamond-core dimeric structure with pentagonal-planar iodine centers. The interaction of PhI(OAc)(2) with 1 equiv of NaHSO(4).H(2)O affords a solid-state polymeric phenyliodine(III) sulfate, [(PhIO)(3).SO(3)](n), in which bis(mu-oxo)triiodanyl dication repeat units are linked by sulfate anions. Three of these neighboring polymeric chains form pseudo triple-helix supramolecular structure, which translates along crystallographic b-axis. The reaction of PhI(OAc)(2) with 3 equiv of NaHSO(4).H(2)O results in the formation of a tetrameric phenyliodine(III) sulfate, PhI(OH)OSO(2)O(Ph)IOI(Ph)OSO(2)OI(OH)Ph, the solid state structure of which consists of mu-oxodiiodanyl dicationic species linked by sulfate anions to the terminal hydroxy(phenyl)iodonium groups. The pseudo double-helix structure of this compound formed by the strong intermolecular interactions between two neighbor mu-oxodiiodanyl dicationic fragments and four (per pseudo helix dimer) areas of sulfate anions to the terminal hydroxy(phenyl)iodonium groups interactions.

During the synthesis of tricyclic phosphonopyrrolidines via intramolecular Diels-Alder reactions of 1-acylamino(furan-2-yl)methyl phosphonates, two isomers are formed in most cases. The presence of a short three-atom tether together with spectroscopic data, including difference NOE, revealed that the cycloaddition occurred exo, but the phosphonate substituent on the tether had an exo or endo orientation. This was confirmed via X-ray analysis. A thermodynamic preference for the product with the phosphonate function in the endo position was observed experimentally and was confirmed theoretically. Density functional theory methods and several high-level post Hartree-Fock procedures were used to rationalize the observed isomer ratio of the IMDAF-reactions. This was done for two different types of reagents: with the activating carbonyl group in the tether or as a substituent on the tether. For the first type of molecules there is a large steric hindrance of the bulky tether substituents that disfavors the exo-isomer. In the latter case, there was a very small energy difference between the transition states causing a mixture of epimers being formed.

2-Iodylphenol ethers were prepared by the dimethyldioxirane oxidation of the corresponding 2-iodophenol ethers and isolated as chemically stable, microcrystalline products. Single-crystal X-ray diffraction analysis of 1-iodyl-2-isopropoxybenzene 8c and 1-iodyl-2-butoxybenzene 8d revealed pseudopolymeric arrangements in the solid state formed by intermolecular interactions between IO2 groups of different molecules. 2-Iodylphenol ethers can selectively oxidize sulfides to sulfoxides and alcohols to the respective aldehydes or ketones.

New N-functionalized benziodazoles were prepared by the peracetic oxidation of 2-iodobenzamides derived from alanine or valine. X-ray crystal structural analysis of two benziodazole-based phenyliodonium derivatives provides insight into facile interchange between benziodazoles and iminium benziodoxoles under acidic or basic conditions. [reaction: see text]

Preparation, structural characterization, and reactivity of 3-[bis(trifluoroacetoxy)iodo]benzoic acid and 3-[hydroxy(tosyloxy)iodo]benzoic acid, new recyclable iodine(III) reagents derived from 3-iodosylbenzoic acid, are described. The reduced form of these reagents, 3-iodobenzoic acid, can be easily recovered from the reaction mixtures using ion-exchange resin or basic aqueous workup followed by acidification with HCl.

New 1-substituted benziodazoles, namely, azide 7, tosylate 8, mesylate 9, and triflate 10, were prepared by the reaction of acetoxybenziodazole 3 with TMSN3, TsOH·H2O, MsOH, or TMSOTf, respectively. Reaction of triflate 10 with alcohols (methanol, ethanol, 2-propanol, and 2-adamantanol) afforded novel 1-alkoxy-3-iminiumbenziodoxoles 11a−d, while similar reactions with amides gave 1-amido-3-iminiumbenziodoxoles 12a−d in 51−89% yield. The structure of iminiumbenziodoxole 12b was established by a single-crystal X-ray analysis. The results of ab initio molecular orbital calculations on structures 3 and 11 are in good agreement with X-ray structural data. The calculation results indicate that the driving force of the novel rearrangement of benziodazoles to 3-iminiumbenziodoxoles is the greater thermodynamic stability of the N-protonated 3-iminobenziodoxoles relative to O-protonated benziodazol-3-ones by about 9.0 (MP2: 10.8) kcal/mol in the case of the acetoxy substituted 3 and 3d compounds and 15 kcal/mol (M...

1-[Hydroxy(sulfonyloxy)iodo]-1H,1H-perfluoroalkanes 3 [R(f)CH(2)I(OH)OSO(2)R; R = CH(3), CF(3), p-CH(3)C(6)H(4), R(f) = CF(3), C(2)F(5)] can be prepared in two steps from the appropriate iodofluoroalkanes by oxidation with peroxytrifluoroacetic acid and subsequent reaction with TsOH, MsOH, or Me(3)SiOTf. The tosylate derivative 3a reacts with silyl enol ethers under mild conditions to give the respective alpha-(tosyloxy) ketones. A similar reaction of cyclohexene furnishes cis-1,2-bis(tosyloxy)cyclohexane as the major product. Triflates 3c,f react with (trimethylsilyl)arenes under mild conditions to afford the respective (fluoroalkyl) (aryl)iodonium triflates 7, while the analogous reaction with alkynyltrimethylsilanes leads to novel (fluoroalkyl)(alkynyl)iodonium salts 8.

Azidoiodinanes 2 and 4a,b can be prepared from the appropriate benziodoxoles 1 and 3a,b and trimethylsilyl azide in the form of stable, crystalline compounds. A single-crystal X-ray analysis for azide 4b revealed the expected hypervalent iodine distorted T-shaped geometry with the N1−I−O bond angle of 169.5 (2) degrees. The lengths of the bonds to the iodine atom, I−N (2.18 A), I−O (2.13 A), and I−C (2.11 A), are within the range of typical single covalent bonds in organic derivatives of polyvalent iodine, while the previously reported benziodoxoles generally have an elongated I−O bond. The geometry of the I(III)NNN fragment in 4b is similar to the literature electron diffraction data on monomeric iodine azide, IN3, in gas phase. Azidobenziodoxoles 2,4 are potentially useful reagents for direct azidation of organic substrates, such as dimethylanilines, alkanes, and alkenes. Reaction of 2 with dimethylanilines proceeds under mild conditions to afford the respective N-azidomethyl-N-methylanilines in excelle...

Organosulfonyloxy derivatives of 1,2-benziodoxol-3(1H)-one (3a-c) and 3,3-bis(trifluoromethyl)-3(1H)-1,2-benziodoxole (5a-c) can be prepared in high yield by the reaction of 1-hydroxybenziodoxoles 1 or 4 and the corresponding sulfonic acids or Me(3)SiOTf in the form of stable, but moderately hygroscopic, microcrystalline solids. Reaction of the triflate derivatives 3a and 5a with alkynyltrimethylsilanes affords either alkynyliodonium triflates 6, or (E)-beta-(trifluoromethanesulfonyloxy)alkenyliodonium triflates 7, while the same reaction in the presence of pyridine selectively gives the respective 1-alkynylbenziodoxoles 8 and 9 in 82-90% yield.

[reaction: see text] New amino acid-derived iodobenzene dicarboxylates were prepared by the reaction of (diacetoxyiodo)benzene with N-protected natural amino acids. These compounds in the presence of iodide anion can be used as reagents for beta-iodocarboxylation of alkenes leading to the respective amino acid esters.

The geometries and stabilities of HCCH, ICCH, ICCI, IF 3 , IF 2 CCH, IF(CCH) 2 , I(CCH) 3 , I 4 (CC) 4 4+ , and four isomers of I 4 (CC) 4 F 4 were calculated at the ab initio HF/LANL1DZ level. Final geometries were used for electron correlation calculations at the MP4/LANL1DZ level. The results of the calculations demonstrate considerable stability and suggest square planar structures for the macrocyclic tetraalkynyl tetraiodonium compounds

Allene 1 reacts with PhIO/BF 3 .Et 2 O or PhIF 2 /BF 3 .Et 2 O in CH 2 Cl 2 at -60 o C with the formation of novel phenyldihydrofuryliodonium salts 2. Molecular structures for both products 2a,b are determined by X-ray analysis. Iodonium perchlorate 2b reacts with the anionic nucleophiles (NaN 3 , NaOCH 3 , NaOC 2 H 5 , CuI/KI) to give the corresponding products of the vinylic nucleophilic substitution (6a-e) of the iodobenzene moiety

Bis(phenyliodonium) diyne triflates 8-10 were prepared by the reaction of the corresponding tributyltin substituted diacetylenes 4-6 with cyanophenyliodonium triflate 7 in 18-93% yields as relatively stable microcrystalline solids. They were characterized by multinuclear NMR, IR, and analytical data. Iodonium salts 8-10 reacted with triphenylphosphine under mild conditions with the loss of iodobenzene giving bisphosphonium salts 11,12 in high yields

The title compound 2 is readily prepared as a stable microcrystalline solid from bis(tri-n-butylstannyl) acetylene and PhICN•OTf. It was fully characterized by multinuclear NMR, IR, and elemental analysis. As expected, the electron-deficient acetylene 2 reacts with a number of nucleophiles (e.g., Ph 3 P, PhSNa, and PhOLi) providing a variety of bifunctionalized acetylenes 5, 6, 7, and 9. It also undergoes cycloaddition reactions with cyclopentadiene, furan, and other 1,3-dienes to afford useful bis(iodonium) norbornadiene-type adducts 12-14

PQQ (methoxatin), a bis(quinone) tricarboxylic acid, is an organic cofactor in a variety of biological redox processes. It is effectively inhibited on a micromolar scale by alkynyl and aryl monoiodonium salts, whereas bis-(iodonium)triflates 5 and 8 are PQQ inhibitors at nanomolar levels

Reactions of fluoroxenonium triflate (1), fluorosulfate (2), and nitrate (3), prepared from XeF 2 and the corresponding acids in CH 2 Cl 2 at −50°C, with cyclohexene and 1-hexene result in β-fluoroalkyl triflates, fluorosulfates, and nitrates. Triflate 1 reacts with cyclohexene with exclusive formation of the cis isomer 5, the analogous reactions of fluorosulfate 2 and nitrate 3 give mixtures of the corresponding cis and trans isomers. Reactions of 1-hexene with reagents 1−3 lead to mixtures of two regioisomers with domination of the Markovnikow type of addition. The stereochemical result of these reactions is rationalized in terms of an electrophilic attack by the positive xenonium ion on the π-electrons of the double bond with intermediate formation of organoxenonium species in analogy with the behavior of the isoelectronic iodine(III) species

La synthese des composes du titre a partir de «1,4-bis[tributylstannyl]-buta-1,3-diyne et -acetylene est presentee