Iodonium Cation Research Articles

Key-to-lock halogen bond-based tetragonal pyramidal association of iodonium cations with the lacune rims of beta-octamolybdate.

The structure-directing "key-to-lock" interaction of double σ-(IIII)-hole donating iodonium cations with the O-flanked pseudo-lacune rims of [β-Mo8O26]4- gives halogen-bonded iodonium-beta-octamolybate supramolecular associates. In the occurrence of their tetragonal pyramidal motifs, deep and broad σ-(IIII)-holes of a cation recognize the molybdate backbone, which provides an electronic pool localized around the two lacunae. The halogen-bonded I⋯O linkages in the structures were thoroughly studied computationally and classified as two-center, three-center bifurcated, and unconventional "orthogonal" I⋯O halogen bonds. In the latter, the O-atom approaches orthogonally the C-IIII-C plane of an iodonium cation and this geometry diverge from the IUPAC criteria for the identification of the halogen bond.

Halogen Bonding and/or Covalent Bond: Analogy of 3c-4e N···I···X (X = Cl, Br, I, and N) Interactions in Neutral, Cationic, and Anionic Complexes.

X-ray structural measurements and computational analysis demonstrated the similarity of the geometries and electronic structures of the X-I···N (X = Cl, Br, I, and N) bonding in strong halogen-bonded (HaB) complexes and in the anionic or cationic halonium ions. In particular, I···N bond lengths in the solid-state associations formed by strong HaB donors (e.g., I2, IBr, ICl, and N-iodosuccinimide) and acceptors (e.g., quinuclidine or pyridines) were in the same range of 2.3 ± 0.1 Å as those in the halonium ions [e.g., the bis(quinuclidine)iodonium cation or the 1,1'-iodanylbis(pyrrolidine-2,5-dione) anion]. In all cases, bond lengths were much closer to those of the N-I covalent bond than to the van der Waals separations of these atoms. The strong N···I bonding in the HaB complexes led to a substantial charge transfer, lengthening and weakening of the I···X bonds, and polarization of the HaB donors. As a result, the central iodine atoms in the strong HaB complexes bear partial positive charges akin to those in the halonium ions. The energies and Mayer bond orders for both N···I and I···X bonds in such associations are also comparable to those in the halonium ions. The similarity of the bonding in such complexes and in halonium ions was further supported by the analysis of electron densities and energies at bond critical (3, -1) points in the framework of the quantum theory of atoms in molecules and by the density overlap region indicator. Overall, all these data point out the analogy of the symmetric N···I···N bonding in the halonium ions and the asymmetric X···I···N bonding in the strong HaB complexes, as well as the weakly covalent character of these 3c-4e interactions.

Structure and Bonding of Halonium Compounds.

The geometrical parameters and the bonding in [D···X···D]+ halonium compounds, where D is a Lewis base with N as the donor atom and X is Cl, Br, or I, have been investigated through a combined structural and computational study. Cambridge Structural Database (CSD) searches have revealed linear and symmetrical [D···X···D]+ frameworks with neutral donors. By means of density functional theory (DFT), molecular electrostatic potential (MEP), and energy decomposition analyses (EDA) calculations, we have studied the effect of various halogen atoms (X) on the [D···X···D]+ framework, the effect of different nitrogen-donor groups (D) attached to an iodonium cation (X = I), and the influence of the electron density alteration on the [D···I···D]+ halonium bond by variation of the R substituents at the N-donor upon the symmetry, strength, and nature of the interaction. The physical origin of the interaction arises from a subtle interplay between electrostatic and orbital contributions (σ-hole bond). Interaction energies as high as 45 kcal/mol suggest that halonium bonds can be exploited for the development of novel halonium transfer agents, in asymmetric halofunctionalization or as building blocks in supramolecular chemistry.

NIR-sensitized hybrid radical and cationic photopolymerization of several cyanines in combination with diaryliodonium bis(trifluoromethyl)sulfonyl imide

A series of cyanines exhibiting absorption between 750 and 930 nm reacted after NIR excitation with the bis(t-butylphenyl) iodonium cation comprising the [(CF3SO2)2N]− anion (NTf2)−, resulting in the generation of free radicals and conjugate acids.

Mechanochemical Aliphatic Iodination (and Bromination) by Cascaded Cyclization

AbstractAliphatic iodination via mechanochemistry is a mammoth challenge due to the high polarizability and weak electrophilicity of iodonium cation (I+), and low bond dissociation energy of carbon iodine bond. Herein, the synthesis is demonstrated of oxazoline derivatives from N‐allyl benzamides via mechanochemical cascaded cyclization and halogenation using N‐iodo‐ and N‐bromosuccinimides, respectively, as bifunctional reagents.

Trifluoromethanesulfonamide vs. Non-Fluorinated Sulfonamides in Oxidative Sulfamidation of the C=C Bond: An In Silico Study.

A theoretical analysis of the reaction of oxidative sulfamidation of several alkenes was performed in order to explain the various experimental observations and different reactivity of triflamide and non-fluorinated sulfonamides. Transformations occurring in the system alkene–sulfonamide in the presence of oxidative system (ButOCl + NaI) were analyzed at the MP2/DGDZVP//B3LYP/DGDZVP level of theory using the IEF-PCM method for taking into account the solvent acetonitrile (MeCN) effect. As the model substrates, styrene, trimethyl(vinyl)silane, dimethyl(divinyl)silane and diphenyl(divinyl)silane were chosen and mesylamide, triflamide, tosylamide and p-nosylamide were taken as the reagents. ButOI generated from ButOCl and NaI reacts with sulfonamides to give N-iodinated sulfonamides RSO2NHI and RSO2NI2 as active intermediates, the iodinating activity of the latter being notably higher. The analysis allowed to answer such challenging questions as different reactivity of nonfluorinated sulfonamides leading to aziridination and of triflamide resulting in the formation the main products of bis-triflamidation, or different regioselectivity of halogenation of styrene and trimethyl(vinyl)silane caused by a linear intermediate iodonium cation in the former case and a cyclic one in the latter.

Halogen Bonding Provides Heterooctameric Supramolecular Aggregation of Diaryliodonium Thiocyanate

The crystal structure of the newly synthesized 4-methoxyphenyl(phenyl)iodonium thiocyanate, [PhI(4-C6H4OMe)](SCN), represents the first example of 16-membered cyclic heterooctamer formed by halogen bonding between the iodonium cation and SCN−. Results of density functional theory (DFT) calculations followed by the topological analysis of the electron density distribution within the framework of the quantum theory of atoms in molecules (QTAIM) method at the ωB97XD/DZP-DKH level of theory reveal that energies of attractive intermolecular noncovalent interactions I···S and I···N (responsible for the formation of heterooctameric supramolecular clusters {PhI(4-C6H4OMe)}4·{SCN}4 in the solid state structure of [PhI(4-C6H4OMe)](SCN)) vary from 0.9 to 8.5 kcal/mol.

Radioiodination of Cefoperazone with 125I and its Biological Distribution in Mice

Cefoperazone tracer was radioiodinated with 125I by replacing the hydrogen atom with iodonium cation I+ which is known as an electrophilic substitution reaction. All the reaction parameters were studied to produce maximum Radiochemical yield (RCY) of 125I-Cefoperazone [125I-Cefo] by using 3.7 MBq of Na125I, 150 µg of cefoperazone as substrate, 100 µg of Chloramine-T as oxidizing agent in water at 60oC for 20 min, the RCY of 125I-Cefo up to 90.2% The radiochemical yield was determined practically by electrophoresis 0.02M phosphate buffer with pH 7. A theoretical study was performed using Gaussian 09 to calculate the heat of formation of the expected products. The tracer was separated and purified by high-pressure liquid chromatography (HPLC) with phosphate buffer pH 6.8: methanol (3:1 v/v). The biological distribution of the tracer was studied in normal and infected mice with E-coli bacteria and sacrificed after different time’s intervals activity in each organ was counted and expressed as a percentage of the injected activity per organ.

Iodoarene-Catalyzed Stereospecific Intramolecular sp(3) C-H Amination: Reaction Development and Mechanistic Insights.

A new strategy is reported for intramolecular sp(3) C-H amination under mild reaction conditions using iodoarene as catalyst and m-CPBA as oxidant. This C-H functionalization involving iodine(III) reagents generated in situ occurs readily at sterically hindered tertiary C-H bonds. DFT (M06-2X) calculations show that the preferred pathway involves an iodonium cation intermediate and proceeds via an energetically concerted transition state, through hydride transfer followed by the spontaneous C-N bond formation. This leads to the experimentally observed amination at a chiral center without loss of stereochemical information.

Radioiodination and biological evaluation of valsartan as a tracer for cardiovascular disorder detection

A procedure for radioiodination of valsartan with iodine-125 is carried out via an electrophilic substitution of hydrogen atom with the iodonium cation I+. All reaction parameters were studied to optimize the labeling conditions of valsartan and to obtain a maximum radiochemical yield (RCY) of the 125I-Valsartan [125I-Val]. By using 3.7 MBq of Na125I, 50 μg of valsartan (0.2 mM) as substrate, 25 μg of Iodogen (0.15 mM) as oxidizing agent in ethanol at room temperature for 30 min, the radiochemical yield of 125I-Val was 98.6% The radiochemical yield was determined by electrophoresis using cellulose acetate moistened with 0.02 M phosphate buffer pH 7. The labeled compound was separated and purified by means of high-pressure liquid chromatography (HPLC). The biological distribution in normal mice indicates the suitability of radioiodinated valsartan to image any cardiovascular disorders.

Comparative study between chloramine-T and iodogen to prepare radioiodinated etodolac for inflammation imaging

This study describes a fast and efficient method for radiolabeling of etodolac with iodine-125 [125I], where both chloramine-T and iodogen were used as oxidizing agents. The labeling reaction was carried out via electrophilic substitution of hydrogen atom with the iodonium cation I+. The labeling yield was found to be influenced by different factors such as drug concentration, pH of the reaction mixtures, different oxidizing agents, reaction time, temperature and different organic media. The radiochemical yield (RCY) was determined by TLC system using methylene chloride:ethyl acetate (3:7 v/v) as a developing solvent and by electrophoresis using cellulose acetate moistened with 0.02 M phosphate buffer pH 7. The maximum radiochemical yield of [125I]Etodolac (87.7%) was obtained. Labeled etodolac shows a good localization in inflamed muscle. It excretes mainly via kidney and to some via liver.

Electrochemical iodofluorination of electron-deficient olefins

Electron-deficient olefins like α,β-unsaturated ester, amide, and phosphonate reacted with iodonium cation species generated by the anodic oxidation of iodide anion in Et 3N-5HF/CH 3NO 2 to form corresponding iodofluorinated compounds in good to moderate yields. The reaction proceeds at room temperature under air atmosphere and constant current conditions. The iodofluorinated products were shown to be useful fluorine-containing building blocks.

Synthesis of a New Mutagenic Benzoazepinoquinolinone Derivative

A novel mutagenic compound 1, isolated as a Maillard product from tryptophan and glucose, was synthesized using Larock’s quinoline formation, where addition of iodonium cation to an acetylene moiety of N-propargylaniline triggers subsequent intramolecular electrophilic aromatic substitution to afford quinolines. The key synthetic intermediate 14 was obtained in a good yield when iodonium chloride was employed as an initiator of Larock’s method. Conversion of 14 with another six steps, including annulation of a lactam ring and Curtius rearrangement, furnished the target molecule 1. The synthesized and isolated 1 were identical in comparison of physical and spectral data.

ChemInform Abstract: Iodofluorination of Alkenes and Alkyne Using Electrochemically Generated Iodonium Cation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Iodofluorination of Alkenes and Alkyne using Electrochemically Generated Iodonium Cation

Iodofluorination of Alkenes and Alkyne using Electrochemically Generated Iodonium Cation

Sensitized photolysis of diphenyliodonium cation through intra-ion-pair electron transfer?A novel near-UV photoinitiator: Diphenyliodonium 9-acridinecarboxylate

A novel near-UV photoinitiator, diphenyliodonium 9-acridinecarboxylate (DPIOAC), was synthesized by metathesis, characterized, and studied. In media of different polarity, this compound showed different absorption and fluorescence profiles and photochemical properties. When irradiated with near-UV light, the anion absorbed the radiation and sensitized the photolysis of the iodonium cation. The active free radicals thus formed initiated polymerization of vinyl monomers. The facts influencing the form of the existence of the ion pairs influenced the rate and efficiency of the intra-ion-pair electron transfer and, thus, of the polymerization. This new photoinitiator had a much greater photoinitiation ability for polymerization than the previously reported diphenyliodonium anthroate, which has a carbon atom at the nitrogen position of DPIOAC. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4521–4527, 1999

Synthesis and study of iodonium borate salts as photoinitiators

Iodonium butyltriphenylborate salts (AI+Ar′Ph3B−R), (Bu) were found to be more efficient than iodonium tetraphenylborate salts (RPh) when used as photoinitiators for the polymerization of acrylates. Relative photodecomposition rates were also different. It was found from a study of the photoreaction of iodonium borate salts with a model monomer, methyl methacrylate, that iodonium butyltriphenylborate salts simultaneously produce a butyl radical from the borate anion and an aryl radical from the iodonium cation upon irradiation. Both radicals initiate polymerization. Iodonium tetraphenylborate salts were found to release an aryl radical, but only from the iodonium cation. Iodonium borate salts exhibit strong absorption below 300 nm with a tail absorption above 400 nm. Thus, iodonium butyltriphenyl borate salts are efficient photoinitiators even when used with visible light. When a photosensitizer such as 5,7-diiodo-3-butoxy-6-fluorone is employed, iodonium butyltriphenylborate salts are rendered much more efficient for visible light photopolymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1667–1677, 1998

Electron transfer coloration of fluorane leuco dyes with iodonium salt—an approach for color stabilization

A thermocoloration system consisting of a fluorane leuco dye (FR) and an iodonium salt (DPIOB) was investigated. The color for the FR/DPIOB system posseses a highly colored stability. The rates of the color development reaction show a rapid rise with increase in temperature, and, owing to two kinds of different activation energy (E a) at the range of reaction temperature in the polymeric film, the reaction easily occurs in the high temperature region (>104°C). The thermal susceptibility increases with increase of FR/DPIOB content. A mechanism of thermocoloration via an electron transfer process is proposed. FR is oxidized to the FR +• radical, the iodonium cation is reduced to the diphenyl iodine radical, which then rapidly decomposes to iodobenzene and the phenyl radical. The ring opened cationic ester (FR-Ph) is formed by radical coupling between FR +• and the phenyl radical.

Untersuchung zum Reaktionsverhalten von Nitrilen RCN gegenüber [I 3 ] + [AsF 6 ] − (R = CH 3 , CF 3 , Br, I, H)

Investigation on the Reactivity of Nitriles RCN towards [I3]+[AsF6]− (R = CH3, CF3, Br, I, H) The reaction behaviour of cyanogen compounds R — CN (R = CH3, CF3, Br, I, H) towards [I3]+[AsF6]− is investigated. Whereas CF3CN and BrCN do not react, acetonitrile and cyanogen iodide react with the [I3]+ cation to yield the linear species [ICNI]+ and [CH3CNI]+. The different reactivity of RCN towards [I3]+ is discussed on the basis of the substituent electronegativity X(R) and the HSAB principle. Simple thermodynamic estimations (Born-Haber cycle) explain the greater stability of the (acetonitrile)iodonium cation compared with the inorganic (iodocyan)iodonium salt.

ChemInform Abstract: Photooxidation of 9,10‐Diethoxyanthracene: Mechanistic Dichotomies Between Homogeneous Solution and Reverse Micelle Photoprocesses.

We have compared the photooxidation of the title compound, DEA, by diphenyliodonium salts in homogeneous acetonitrile (AN) and in heptane/AOT/water reverse micelle solutions. The reaction is efficient, which we attribute to rapid (ca. 10 ps) deethylation of the DEA radical cation, initially formed by photoinduced electron transfer. In AN, the electron transfer occurs from singlet excited DEA, but in reverse micelles it is gated by intersystem crossing to triplet DEA. Under these conditions, DEA fluorescence quenching by the iodonium cation may still be observed; we infer operation of the external heavy atom effect as the primary mechanism. Keywords: anthracene, electron transfer, reverse micelle, photochemistry, picosecond.