Aerobic oxidative iodination of organic molecules activated by sodium nitrite

Aerobic oxidative iodination activated by sodium nitrite occurs effectively and selectively with 100% iodine atom economy with air as the oxidant. Silica-supported sulfuric acid was used for the activation of the catalyst and iodination. Thus, I₂/NaNO₂/air/silica-supported H₂SO₄ in acetonitrile iodinated aromatics, ketones and aldehydes effectively at ambient temperature.     

Direct iodination of alkanes

[reaction: see text] A cheap and efficient iodination of hydrocarbons can be achieved by generating tert-butyl hypoiodite from iodine and sodium tert-butoxide. The alkane is reactant and solvent, and this metal-free process provides a clean solution for their direct iodination.     

A simple and facile iodination method of didechlorotiacumicin B and aromatic compounds

Tiacumicin B(also known as fidaxomicin or difimicin) is a marketed 18-membered macrolide antibiotic for the treatment of Clostridium difficile infections. Tiacumicin B is structurally characterized with two chlorine atoms substituted on the aromatic ring, which is installed by the halogenase Tia M. During the study on halide compatibility of Tia M, a facile and nonenzymatic iodination method of didechlorotiacumicin B was discovered, requiring Na I, acid and air for iodination at room temperature.This method was also amenable to other 9 aromatic substrates with electron-rich sites for iodination.     

Investigation on the iodination reaction of methylene blue by liquid chromatography-mass spectrometry with ionspray ionisation.

Radioactive iodine (131I and 123I) labelled methylene blue is used for the early diagnosis of melanoma metastases. We studied the iodination reaction of methylene blue (using "cold" iodine) in order to characterise the iodination product(s) as far as number and position of iodine atoms introduced on the aromatic ring(s) is concerned. The reaction was carried out under the same experimental conditions used for the radioactive one, that is in a large excess of methylene blue. The ionspray HPLC-MS analysis of the reaction mixture showed that the iodinated methylene blue was present only in a very small amount and the main iodinated product was a demethylated one, coming out from the iodination of an impurity azure B. We also studied the iodination reaction of azure B in order to better explain the reaction pathway. Commercial azure B contains impurities of methylene blue and all the possible demethylated derivatives. HPLC-MS analysis of the reaction mixture allowed a complete characterisation of the iodinated and bis-iodinated products.     

A convenient iodination of indoles and derivatives

We report a direct iodination of indole and derivative compounds with iodine monochloride (ICl) in the presence of Celite^®. This procedure has now been extended to the iodination of substituted indoles, azaindoles and pyrroles. The scope of this procedure is exemplified by the iodination of melatonin in 98% yield.     

Eco-friendly oxidative iodination of various arenes with sodium percarbonate as the oxidant

Six easy laboratory procedures are presented for the oxidative iodination of various aromatics, mostly arenes, with either molecular iodine or potassium iodide (used as the sources of iodinating species, I+ or I3+), in the presence of sodium percarbonate(SPC), a stable, cheap, easy to handle, and eco-friendly commercial oxidant.     

An iodine-123 generator/iodination kit: A preliminary report

Preliminary results are described of a¹²³Xe filled device to serve as a combination¹²³I generator/iodination kit.¹²³X was produced in the Brookhaven Linac Isotope Producer (BLIP) by the reaction¹²⁷I(p, 5n)¹²³Xe. The device consists of a small glass ampoule containing an internal glass breakseal and a flanged neck on which was crimped a multi-injection type septum. The ampoule contained a hydrogen sulfide atmosphere to assure that the iodine generated from the decay of the xenon was in the form of iodide. Following an adequate period for¹²³Xe to decay (this period can be used for shipment), a needle is forced through the septum breaking the seal and residual gases are pumped off. The¹²³I in the form of iodide can then be rinsed from the ampoule with any desired solvent or reagent added directly to the device to carry out an iodination in an enclosed environment. Preliminary results of both iodine recovery and iodinations have been promising. This research was supported by the US Department of Energy under Contract No. DE-ACO2-76CH0016.     

The iodination of aromatic substrates on alumina

The iodination of a wide variety of aromatic substrates has been attained on dehydrated alumina. The procedure is particularly well suited for arenes.     

Rapid aerobic iodination of arenes mediated by hypervalent iodine in fluorinated solvents

Arenes are rapidly converted to the corresponding iodides by aerobic oxidative iodination at room temperature by treatment with iodine and catalytic quantities of nitrous acid in a fluorinated solvent. Dichloroiodic acid is proposed as the actual iodination reagent.     

A new, environment friendly protocol for iodination of electron-rich aromatic compounds

A new environment friendly procedure for effective aromatic iodination is presented. A mixture of potassium iodide and potassium iodate is used in the presence of an acid for in situ iodination of aromatic compounds.     

Regioselective iodination of flavonoids by N-iodosuccinimide under neutral conditions

Regioselective synthesis of C-6 and C-8 monoiodo flavonoids, which are important intermediates for the synthesis of flavonoid natural products and drug molecules, was achieved by iodination of suitably alkylated flavonoids with N-iodosuccinimide (NIS) in DMF. The iodination gives either a C-6 or C-8 iodo flavonoid in high yield, depending on the protection pattern of the C-5 and C-7 OH groups. The mild and neutral conditions render this novel protocol particularly useful for the regioselective iodination of acid-sensitive substrates.     

Deciphering the peptide iodination code: Influence on subsequent gas-phase radical generation with photodissociation ESI-MS

Iodination of tyrosine was recently discovered as a useful method for generating radical peptides via photodissociation of carbon-iodine bonds by an ultraviolet photon in the gas phase. The subsequent fragmentation behavior of the resulting odd-electron peptides is largely controlled by the radical. Although previous experiments have focused on mono-iodination of tyrosine, peptides and proteins can also be multiply iodinated. Tyrosine and, to a lesser extent, histidine can both be iodinated or doubly iodinated. The behavior of doubly iodinated residues is explored under conditions where the sites of iodination are carefully controlled. It is found that radical peptides generated by the loss of a single iodine from doubly iodinated tyrosine behave effectively identically to singly iodinated peptides. This suggests that the remaining iodine does not interfere with radical directed dissociation pathways. In contrast, the concerted loss of two iodines from doubly iodinated peptides yields substantially different results that suggest that radical recombination can occur. However, sequential activation can be used to generate multiple usable radicals in different steps of an MS ⁿ experiment. Furthermore, it is demonstrated that in actual peptides, the rate of iodination for tyrosine versus mono-iodotyrosine cannot be predicted easily a priori. In other words, previous assumptions that mono-iodination of tyrosine is the rate-limiting step to the formation of doubly iodinated tyrosine are incorrect.     

Influence of acetylation on the iodination of thyroglobulin and the formation of thyroxine

Summary The results obtained show that when thyroglobulin is iodinated_{in vitro} the formation in it of thyroxine from the iodotyrosine residues present in it before iodination is possible. The structure of the thyroglobulin apparently plays an important role not only in the formation of thyroxine but also in the level of iodination of the protein.Institute of Biochemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Institute of Biological and Medicinal Chemistry, Academy of Medical Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 485–488, July–August, 1978.     

Mild and efficient direct aromatic iodination

Aryl iodides are important synthetic intermediates that can be transformed into tritium labelled compounds by metal-mediated hydrodehalogenation and also react in a number of important synthetic transformations. We present ICl/In(OTf)₃ as a new reagent combination for mild iodination, suitable for acid-sensitive substrates such as carbohydrates.     

Theoretical analysis of reactions of electrophilic iodination and chlorination of benzene and polycyclic arenes in density functional theory approximation

Quantum-chemical method DFT B3LYP/6-311G* was applied to stage by stage thermodynamic calculation of reactions of electrophilic iodination of benzene, naphthalene, phenanthrene, and anthracene with iodine and iodine monochloride, and comparison with chlorination reactions was performed. The main distinction of iodination process from chlorination was an enhanced reversibility owing to protodeiodination. The reversibility of iodination grows with the electron-donor properties of aromatic substrates. The calculations permit an assumption that the chlorination of anthracene and phenanthrene with iodine monochloride occurs most probably through stages of electrophilic iodination-dehydroiodination.     

On the product distribution in the iodination of phenol

The product distribution in the iodination of phenol with I₂, in water solution is buffer and pH dependent with the ortho product increasing at low pH and low buffer concentration. This effect is attributed to different rates of proton transfer from the 4-iodo-2,5-; and 2-iodo-3,5-cyclohexadienone intermediate.     

A simple iodination protocol via in situ generated ICl using NaI/FeCl3

A novel iodination of silyl-enol ethers using hitherto unexplored NaI/FeCl₃ system is reported. The procedure has been extended to the iodination of aromatic and hetero aromatic compounds.     

Tetramethylammonium dichloroiodate: an efficient and environmentally friendly iodination reagent for iodination of aromatic compounds under mild and solvent-free conditions

Tetramethylammonium dichloroiodate (1, TMADCI) as a mild and efficient iodination reagent was prepared. Iodination of different aromatic compounds with this reagent takes place fast and with high yields under solvent-free conditions.     

Efficient iodination of structurally varying pyrazoles in heterophase medium

A synthesis of 4-iodo-substituted pyrazoles by iodination of pyrazole and its derivatives in the heterophase (H₂O/CHCl₃ (CCl₄)) medium with the system KI-KIO₃ in the presence of H₂SO₄ additives was accomplished. The yields of 4-iodo-substituted pyrazoles in the iodination of pyrazole, 3,5-dimethylpyrazole, pyrazole-3(5)-carboxylic acid, 1-methylpyrazole-3-carboxylic acid, 1-methylpyrazole-5-carboxylic acid, 3-nitropyrazole, 1-methyl-3-nitropyrazole, 1-methylpyrazole, 1-ethylpyrazole, and 1-isopropylpyrazole were within 80–97%, whereas in the case of 3-nitropyrazole-5-carboxylic acid it was 32%.     

Green iodination of pyrazoles with iodine/hydrogen peroxide in water

In this Letter, we describe a practical, green iodination of pyrazoles to form the corresponding 4-iodopyrazole derivatives. The reaction takes place in water, using only 0.5 equiv of iodine and 0.6 equiv of hydrogen peroxide, a system that generates water as the only reaction by-product.