Carbon-iodine Bond Research Articles

Exceptionally Short Tetracoordinated Carbon-Halogen Bonds in Hexafluorodihalocubanes.

Molecules that contain bonds whose length significantly deviates from the average are of interest in the context of understanding the nature and limits of the chemical bonds. However, it is difficult to disentangle the individual contributions of the multiple factors that give rise to such bond-length deviations as reports on such molecules remain scarce. In the present study, we have succeeded in synthesizing hexafluorodihalocubanes of the type C8F6X2 (2) (X = Cl (2Cl), Br (2Br), I (2I)), which represent a new series of molecules with unusual C(sp3)-halogen bonds. The C(sp3)-halogen bonds of 2Cl, 2Br, and 2I, determined via single-crystal X-ray diffraction analysis, are approximately 0.07-0.09 Å shorter than typical C(sp3)-halogen bonds. In particular, the carbon-iodine bonds of 2I are the shortest C(sp3)-I bonds reported to date. The solution-state structures and electronic states of the C(sp3)-halogen bonds in these hexafluorodihalocubanes were analyzed by X-ray absorption spectroscopy, which revealed detailed information on the length of these C(sp3)-halogen bonds in solution and the solid state as well as on the electron-deficient nature of 2. Detailed theoretical calculations and a comparison with halotrinitromethanes (1), which represent another series of molecules with shortened C(sp3)-halogen bonds, revealed that the factors responsible for the shortening of the C(sp3)-halogen bond vary among the different C(sp3)-halogen bonds, i.e., for C(sp3)-Cl and C(sp3)-Br, the s-character and hyperconjugation effects predominate, whereas for C(sp3)-I, the interatomic Coulombic interaction effect prevails.

Distinguishing the XUV-induced Coulomb explosion dynamics of iodobenzene using covariance analysis

Abstract The primary and secondary fragmentation dynamics of iodobenzene following its ionization at 120 eV were determined using three-dimensional velocity map imaging and covariance analysis. Site-selective iodine 4d ionization was used to populate a range of excited polycationic parent states, which primarily broke apart at the carbon-iodine bond to produce I+ with phenyl or phenyl-like cations (CnHx + or CnHx 2+, with n = 1-6 and x = 1-5). The molecular products were produced with varying degrees of internal excitation and dehydrogenation, leading to stable and unstable outcomes. This further allowed the secondary dynamics of C6Hx 2+ intermediates to be distinguished using native-frame covariance analysis, which isolated these processes in their own centre-of-mass reference frames. The mass resolution of the imaging mass spectrometer used for these measurements enabled the primary and secondary reaction channels to be specified at the level of individual hydrogen atoms, demonstrating the ability of covariance analysis to comprehensively measure the competing fragmentation channels of aryl cations, including those involving intermediate steps.

Acyl Iodide Synthesis from Carboxylic Acids Using a Novel Ph2P(O)H‐I2 Binary System and Its Application to Facile Preparation of Amides, Esters, and Thioesters

AbstractAcyl iodides are expected to be excellent acylating agents due to the low bond dissociation energy of the carbon–iodine bond and the high capability of iodine as a leaving group. Unfortunately, the preparative methods for acyl iodides directly from carboxylic acids are rather limited. In this work, we found that a novel binary system combining I2 and diphenylphosphine oxide (Ph2P(O)H) provides a simple method for the preparation of acyl iodides from carboxylic acids. Furthermore, the subsequent one‐pot reaction with appropriate nucleophiles, such as amines, alcohols, and thiols, afforded the corresponding amides, esters, and thioesters, respectively, in good to excellent yields.

Highly efficient removal of methyl iodide gas by recyclable Cu0-based mesoporous silica

Developing recyclable adsorbents for co-capture of I2 and CH3I gas is a meaningful and challenging topic. Herein, Cu0-based mesoporous silica (C-S) materials were synthesized and applied for CH3I capture for the first time. Factors (Cu0 content, temperature, contact time and CH3I concentration) affecting the adsorption behavior were investigated. The results demonstrated that the CH3I adsorption capacity of the obtained C-S materials reached up to 1060 mg/g at 200 ℃. Furthermore, the C-S material exhibited excellent reusability (91.3 %, 5 cycles). It was found that Cu0 could cleave the carbon iodine bonds, causing CH3I to dissociate into •CH3 and I-. Then the Cu+ converted from Cu0 reacted with I- to achieve the purpose of CH3I capture. The adsorption mechanism of CH3I on the C-S materials could be concluded that Cu0 reacted with CH3I form CuI (Cu + CH3I → CuI + •CH3). This work suggested that the obtained C-S materials could be promising adsorbents for CH3I capture.

Influence of the Chemical Modification of Carbon Nanotube Fibers on Electrical properties and Electromechanical Response

The electromechanical response (EMR) of carbon nanotube (CNT) fibers is related to the densification process of the CNT network driven by electromagnetic force. The study of the interaction between the electrical properties and the electromechanical response of carbon nanotubes is of great theoretical significance for exploring the microstructure of carbon nanotube fibers and developing the related flexible electronic devices. This study investigated the relationship between the conductive pathway network and EMR, by analyzing the internal structural characteristics of the CNT fibers after undergoing hydrogen peroxide oxidation and iodine modification. The results show that impurities such as amorphous carbon impeded electron transport and deformation of CNT networks. After hydrogen peroxide oxidation treatment, he carbon nanotube surface impurities inside the fibres were reduced, the van der Waals forces between carbon nanotubes were increased, the deformation of the carbon nanotube network was enhanced, and the negative effect of the decrease in the elastic modulus of the fibres caused by the increase in temperature was weakened. In the case of iodine-decorated CNT fibers, carbon-iodine bonds effectively strengthened the interaction between CNTs, but hinders the contraction of the carbon nanotube network, resulting in a weaker electromechanical response. Hydrogen peroxide oxidation treatment is more beneficial than iodine modification to improve the shrinkage and deformation ability of carbon nanotube fibres in the electromechanical response.

Catalyst-free photoarylation of 2-aryl-2H-indazoles by carbon-iodine bond activation.

A photocatalyst-free visible-light induced arylation of 2-aryl-2H-indazoles with aryl iodides has been developed for the first time to produce 3,2-diaryl-2H-indazoles in good to moderate yields. In this transformation, potassium tert-butoxide acts as an activator of the C-I bond and also as a scavenger of in situ generated HI in the reaction. This method exhibits high functional group tolerance with a wide substrate scope and it has been successfully applied to the synthesis of liver X receptor agonists and also for fluorescent probes. This is the first report on the photoarylation of 2-arylindazoles at the C3-position with aryl iodides under catalyst-free conditions.

Copper-Catalyzed Aryne Insertion into the Carbon-Iodine Bond of Heteroaryl Iodides.

Aryne insertions into the carbon-iodine bond of heteroaryl iodides has been achieved for the first time. This novel reaction provides an efficient pathway for the synthesis of valuable building blocks 2-iodoheterobiaryls from heteroaryl iodides and o-silylaryl triflates in excellent regioselectivity. The copper(I) catalyst, which bears a N-heterocyclic carbene (NHC) ligand, is essential to accomplish the reaction. Control reactions and DFT calculations indicate that the coordination of copper, as a Lewis acid, with nitrogen atoms of heteroaryl iodides mediates the insertion of arynes into heteroaryl carbon-iodine bonds.

2-Benzamide Tellurenyl Iodides: Synthesis and Their Catalytic Role in CO2 Mitigation.

Benzamide-derived organochalcogens (chalcogen=S, Se, and Te) have shown promising interest in biological and synthetic chemistry. Ebselen molecule derived from benzamide moiety is the most studied organoselenium. However, its heavier congener organotellurium is under-explored. Here, an efficient copper-catalyzed atom economical synthetic method has been developed to synthesize 2-phenyl-benzamide tellurenyl iodides by inserting a tellurium atom into carbon-iodine bond of 2-iodobenzamides in one pot with 78-95 % yields. Further, the Lewis acidic nature of Te center and Lewis basic nature of nitrogen of the synthesized 2-Iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides enabled them as pre-catalyst for the activation of epoxide with CO2 at 1 atm for the preparation of cyclic carbonates with TOF and TON values of 1447 h-1 and 4343, respectively, under solvent-free conditions. In addition, 2-iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides have also been used as pre-catalyst for activating anilines and CO2 to form a variety of 1,3-diaryl ureas up to 95 % yield. The mechanistic investigation for CO2 mitigation is done by 125 Te NMR and HRMS studies. It seems that the reaction proceeds via formation of catalytically active Te-N heterocycle, an ebtellur intermediate which is isolated and structurally characterized.

光化学的活性化を駆動力としたヨウ素を利用する新規分子変換反応の開発

Effective use of the light that surrounds us is the hottest research topic in all fields, including the energy field. Light is the means by which reactions occur, and can be thought of as a “type of reagent.” Since light has no shape or weight, it is a clean substance that does not leave any residue, and can be one of the most important methods for investigating processes that reduce environmental impact. Against this background, the authors have been conducting research aiming at the development of novel molecular transformation reactions driven by photochemical activation of representative elements. In this study, we focused on iodine, which is easy to handle, has low toxicity, and is highly responsive to visible light. That is to say, iodine and carbon-iodine bonds readily respond to light energy as small as visible light and undergo bond cleavage to generate radical species. By applying this phenomenon to fine organic synthesis reactions, the authors have succeeded in developing a methodology for easily synthesizing compounds such as phenacyl halides, cyclopropanes, and lactones, which have high industrial value, from light energy and inexpensive raw materials.

RDD-HCD Provides Variable Fragmentation Routes Dictated by Radical Stability.

Radical-directed dissociation (RDD) is a fragmentation technique in which a radical created by selective 213/266 nm photodissociation of a carbon-iodine bond is reisolated and collisionally activated. In previous RDD experiments, collisional activation was effected by ion-trap collision-induced dissociation (CID). Higher-energy collisional dissociation (HCD) differs from CID both in terms of how ions are excited and in the number, type, or abundance of fragments that are observed. In this paper, we explore the use of HCD for activation in RDD experiments. While RDD-CID favors fragments produced from radical-directed pathways such as a/z-ions and side chain losses regardless of the activation energy employed, RDD-HCD spectra vary considerably as a function of activation energy, with lower energies favoring RDD while higher energies favor products resulting from cleavage directed by mobile protons (b/y-ions). RDD-HCD therefore affords more tunable fragmentation based on the HCD energy provided. Importantly, the abundance of radical products decreases as a function of increasing HCD energy, confirming that RDD generally proceeds via lower-energy barriers relative to mobile-proton-driven dissociation. The dominance of b/y-ions at higher energies for RDD-HCD can therefore be explained by the higher survivability of fragments not containing the radical after the initial or subsequent dissociation events. Furthermore, these results confirm previous suspicions that HCD spectra differ from CID spectra due to multiple dissociation events.

Single- and multi-photon-induced ultraviolet excitation and photodissociation of CH3I probed by coincident ion momentum imaging.

The UV-induced photodissociation dynamics of iodomethane (CH3I) in its A-band are investigated by time-resolved coincident ion momentum imaging using strong-field ionization as a probe. The delay-dependent kinetic energy distribution of the photofragments resulting from double ionization of the molecule maps the cleavage of the carbon-iodine bond and shows how the existence of a potential well in the di-cationic potential energy surfaces shapes the observed distribution at small pump-probe delays. Furthermore, the competition between single- and multi-photon excitation and ionization of the molecule is studied as a function of the intensity of the UV-pump laser pulse. Two-photon excitation to Rydberg states is identified by tracking the transformation of the delay-dependent singly-charged iodomethane yield from a pure Gaussian distribution at low intensity to a Gaussian with an exponentially decaying tail at higher intensities. Dissociative ionization induced by absorption of three UV photons is resolved as an additional delay-dependent feature in the kinetic energy of the fragment ions detected in coincidence.

Energy transfer photocatalyst enabled by covalent organic framework induced reversible complexation-mediated polymerization under white LED light irradiation and the mechanism study

Heterogeneous photocatalytic polymerization has emerged as a successful method for the development of greener reversible deactivation radical polymerization protocols. In this article, a halogen-free covalent organic framework (1,3,6,8-tetrakis(4-aminophenyl) pyrene-1,3,6,8-tetrakis(4-formylphenyl) pyrene-covalent organic framework [TAPPy-TFPPy-COF]) based on imine bonds was prepared, which mediated reversible complexation-mediated polymerization of methacrylates for the synthesis of various polymers with controllable molecular weight and relatively uniform distribution under white light-emitting diode light irradiation. TAPPy-TFPPy-COF absorbed the energy from photo and was transformed to excited state (COF•), and then the energy transfer occurred between COF• and initiator 2-iodo-2-methylpropionitrile (CP-I), which cleaved the carbon-iodine bond of CP-I to generate carbon radicals, thereby initiating the polymerization reaction. The density function theory calculation suggests that the coordination of iodine of CP-I with nitrogen on TAPPy-TFPPy-COF significant decrease the bond dissociation energy, making the polymerization more efficiency. The monomer conversion and reaction time showed a linear kinetic relationship of first order. The number average molecular weight of the obtained polymers increased along with the monomer conversion rate, and in good agreement with theoretical molecular weight, indicating a high frequency of the activation-deactivation cycle. The obtained polymer has high chain end fidelity, which can be used to synthesize various block copolymers. This work provided a new direction for the development of heterogeneous catalysts for reversible complexation-mediated polymerization.

Development of mass spectrometric glycan characterization tags using acid-base chemistry and/or free radical chemistry.

Despite recent advances in glycomics, glycan characterization still remains an analytical challenge. Accordingly, numerous glycan-tagging reagents with different chemistries were developed, including those involving acid-base chemistry and/or free radical chemistry. Acid-base chemistry excels at dissociating glycans into their constituent components in a systematic and predictable manner to generate cleavages at glycosidic bonds. Glycans are also highly susceptible to depolymerization by free radical processes, which is supported by results observed from electron-activated dissociation techniques. Therefore, the free radical activated glycan sequencing (FRAGS) reagent was developed so as to possess the characteristics of both acid-base and free radical chemistry, thus generating information-rich glycosidic bond and cross-ring cleavages. Alternatively, the free radical processes can be induced via photodissociation of the specific carbon-iodine bond which gives birth to similar fragmentation patterns as the FRAGS reagent. Furthermore, the methylated-FRAGS (Me-FRAGS) reagent was developed to eliminate glycan rearrangements by way of a fixed charged as opposed to a labile proton, which would otherwise yield additional, yet unpredictable, fragmentations including internal residue lossesor multiple external residue losses. Lastly, to further enhance glycan enrichment and characterization, solid-support FRAGS was developed.

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.

Copper‐Catalyzed Difluoromethylation of Alkyl Iodides Enabled by Aryl Radical Activation of Carbon–Iodine Bonds

AbstractThe engagement of unactivated alkyl halides in copper‐catalyzed cross‐coupling reactions has been historically challenging, due to their low reduction potential and the slow oxidative addition of copper(I) catalysts. In this work, we report a novel strategy that leverages the halogen abstraction ability of aryl radicals, thereby engaging a diverse range of alkyl iodides in copper‐catalyzed Negishi‐type cross‐coupling reactions at room temperature. Specifically, aryl radicals generated via copper catalysis efficiently initiate the cleavage of the carbon–iodide bonds of alkyl iodides. The alkyl radicals thus generated enter the copper catalytic cycles to couple with a difluoromethyl zinc reagent, thus furnishing the alkyl difluoromethane products. This unprecedented Negishi‐type difluoromethylation approach has been applied to the late‐stage modification of densely functionalized pharmaceutical agents and natural products.

Copper-Catalyzed Difluoromethylation of Alkyl Iodides Enabled by Aryl Radical Activation of Carbon-Iodine Bonds.

The engagement of unactivated alkyl halides in copper-catalyzed cross-coupling reactions has been historically challenging, due to their low reduction potential and the slow oxidative addition of copper(I) catalysts. In this work, we report a novel strategy that leverages the halogen abstraction ability of aryl radicals, thereby engaging a diverse range of alkyl iodides in copper-catalyzed Negishi-type cross-coupling reactions at room temperature. Specifically, aryl radicals generated via copper catalysis efficiently initiate the cleavage of the carbon-iodide bonds of alkyl iodides. The alkyl radicals thus generated enter the copper catalytic cycles to couple with a difluoromethyl zinc reagent, thus furnishing the alkyl difluoromethane products. This unprecedented Negishi-type difluoromethylation approach has been applied to the late-stage modification of densely functionalized pharmaceutical agents and natural products.

Synthesis and Single Crystal X-ray Studies of Cyclic Te(IV) Diiodide

The cyclic tellurium(IV) diiodide, 2-Methyl-1,1-diiodo-1-telluracyclopentane, was prepared in good yields at room temperature by the incorporation of tellurium powder across Carbon–Iodine bond in presence of sodium iodide and acetone. The cyclic tellurium(IV) diiodide compound has been established by proton and 13carbon NMR spectroscopy along with elemental analysis. This compound was further characterized by 125Te NMR in DMSO. Molecular structures of cyclic tellurium(IV) diiodide was also established by single-crystal X-ray studies. In solid-state, molecular structures of cyclic tellurium(IV) diiodidepossess scarcely observed Te…I secondary bonding interactions (SBIs) and two molecule are co-crystallized. Both molecules are interconnected with each other by Te…I secondary bonding interactions. The five-membered rings acquire a twist-boat shape structure. Observed C–Te–C bond angles for molecule A, and molecule B are 85.0(1)°& 85.4(2)° respectively. Similarly observed, I–Te–I bond angles for both molecule A & B are 174.5(1)°&174.2(1)° respectively.

Synthesis of Chiral-Substituted 2-Aryl-ferrocenes by the Catellani Reaction.

A palladium-catalyzed and norbornene-mediated methodology has been developed for the synthesis of chiral 2-aryl-ferroceneamides from chiral 2-iodo-N,N-diisopropylferrocencarboxamide, iodoarenes, and alkenes using a JohnPhos ligand and potassium carbonate as a base in dimethylformamide at 105 °C. The developed three-component coupling protocol allows the compatibility of electron-withdrawing fluoro, chloro, ester, and nitro and electron-donating methyl, methoxy, dimethoxy, benzyl ether-substituted iodo-benzenes, other iodoarenes, such as iodo-naphthalene, heteroarenes, such as iodothiophene, and terminating substrates, such as methyl, ethyl, tert-butyl acrylates, and substituted styrenes with 2-iodo-N,N-diisopropylferrocencarboxamide. Furthermore, the developed three-component Catellani method proceeded with the retention of the configuration of the planar chiral ferrocene, which depends on the role of the participating carbon-iodine bond in ferrocene. Consequently, the developed protocol enabled the formation of densely substituted chiral 2-aryl ferroceneamides, exhibiting good to excellent enantioselectivity. The conversion of an ester of the synthesized chiral 2-aryl ferroceneamides has also been carried out to further accommodate the easily expendable acid and alcohol functionalities.

Electrochemical Processes Coupled to a Biological Treatment for the Removal of Iodinated X-ray Contrast Media Compounds.

Iodinated X-ray contrast media (ICM) compounds are a form of intravenous radiocontrast containing iodine, which are rapidly eliminated via urine or feces. The issue with the accumulation of ICM has received considerable critical attention since they are ubiquitously distributed in municipal wastewater effluents and in the aquatic environment and are not significantly eliminated by most biological sewage treatment processes. Among the methods that have been tested to eliminate ICM, electrochemical methods have significant advantages, since they can selectively cut the carbon-iodine bonds that are suspected to decrease their biodegradability. On the production sites, the recovery of iodine ions due to the carbon-iodine cleavage can be envisaged, which is particularly interesting to reduce the cost of the ICM production process. The coupling of an electrochemical process and a biological treatment can be carried out to mineralize the organic part of the formed by-products, allowing the recovery of the iodide ions. Therefore, the degradation of diatrizoate, a typical ionic ICM compound, by an electrochemical process was the purpose of this study. The electrochemical reduction of diatrizoate was performed using a flow cell with a graphite felt electrode at different potentials. The removal yield of diatrizoate reached ~100% in 2 h and the main product, 3,5-diacetamidobenzoic acid, was quantitatively formed, showing that diatrizoate was almost completely deiodinated. According to the BOD5/COD ratio, the biodegradability of diatrizoate after electrolysis was considerably improved. Cyclic voltammetry analysis of the electroreduced solution showed several oxidation peaks. The electrochemical oxidation of the by-products formed after the first treatment by electroreduction was then performed at three different potentials to study the influence of electrochemical oxidation on biodegradability. Results showed that the degradation yield of the deiodinated by-products increased with the potential and reached 100% at 1.3 V/SCE. Four different biological treatments were implemented during 21 days in stirred flasks with fresh activated sludge. The evolution of the mineralization during the biological treatment highlighted the biorecalcitrance of diatrizoate as previously estimated by the BOD5/COD ratio. Interestingly, the mineralization yield increased from 41 to 60% when electrochemical oxidation at 1.3 V/SCE was implemented after electroreduction.

Iodine Catalysis for C(sp3)–H Fluorination with a Nucleophilic Fluorine Source

AbstractIodine catalysis was developed for aliphatic fluorination through light‐promoted homolytic C−H bond cleavage. The intermediary formation of amidyl radicals enables selective C−H functionalization via carbon‐centered radicals. For the subsequent C−F bond formation, previous methods have typically been limited by a requirement for electrophilic fluorine reagents. We here demonstrate that the intermediary instalment of a carbon–iodine bond sets the stage for an umpolung, thereby establishing an unprecedented nucleophilic fluorination pathway.