Unexpected Behavior of the Heaviest Halogen Astatine in the Nucleophilic Substitution of Aryliodonium Salts

Guérard, François; Lee, Yong‐Sok; Baidoo, Kwamena E.; Gestin, Jean‐François; Brechbiel, Martin W.

doi:10.1002/chem.201603013

Cited by 3 publications

(5 citation statements)

References 43 publications

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“…Further unexpected behaviour of astatine has been reported in nucleophilic substitution reactions with aryliodonium salts, where astatine gave much faster and slightly higher reaction yields than iodine, a behaviour similar to the results in dediazotation reactions …”

Section: Investigations Of Chemical Propertiessupporting

confidence: 72%

“…Another optimization of this labelling strategy has been developed by Guérard et al Using bispecific aryliodonium salts as precursors, they avoid the electrophilic pathway, which is often hampered by the necessity to oxidize astatine to the only intermediately stable cationic species. Their approach enables to use a nucleophilic substitution with astatide as the reaction partner, which allows for easily controllable reaction conditions.…”

Section: Investigations Of Astatinated Organic Compoundsmentioning

confidence: 99%

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Astatine

Meyer

2018

Labelled Comp Radiopharmac

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This educational review describes and summarizes the historic discovery of element 85, the experiments leading to its physical and chemical characterization and comparison with its lighter homologue iodine. The half-lives of its longest living isotopes At and At with 8.3 and 7.22 hours respectively together with their alpha decay characteristics made these isotopes interesting for radiation biological research. However, the lack of stable isotopes of astatine presents a strong challenge for all characterizations. Nevertheless, the decay characteristics especially of At stimulated several research groups to develop labelling strategies for the preparation of astatinated radiopharmaceuticals for targeted alpha radiation therapy. Because of the distinct differences in the chemical behaviour of astatine, when compared with iodine, these approaches are quite challenging. Accordingly, quite different labelling strategies have been tested, namely nucleophilic and electrophilic substitution reactions as well as complex forming strategies. Classic and new developments for the preparation of these compounds are reviewed.

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Section: Investigations Of Chemical Propertiessupporting

confidence: 72%

Section: Investigations Of Astatinated Organic Compoundsmentioning

confidence: 99%

Astatine

Meyer

2018

Labelled Comp Radiopharmac

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“…5 , one can observe that only single excitations from the 6p subshell (model B) play a non negligible role in the calculation of 6p 5 -6p 4 7s and 6p 4 7s -6p 4 7p transition rates of interest while double excitations from 6p as well as single and double excitations from 6s (models C to E) do not affect the oscillator strengths. Moreover, core-polarization effects from the At VIII [1s 2 … 5d 10 ] ionic core (model F) are rather small. This can be illustrated by the mean ratios of oscillator strengths obtained with two successive models for which the values were found to be equal to gf (B)/ gf (A) = 0.94 ± 0.08, gf (C)/ gf (B) = 1.00 ± 0.01, gf (D)/ gf (C) = 0.99 ± 0.03, gf (E)/ gf (D) = 1.00 ± 0.01 and gf (F)/ gf (E) = 0.99 ± 0.03 where the uncertainty represents the standard deviation.…”

Section: Type Of Calculationmentioning

confidence: 99%

“…This makes 211 At an ideal short-range radiation source for targeted α therapy in cancer treatment (see e.g. [5][6][7][8][9][10] ). * Corresponding author.…”

Section: Introductionmentioning

confidence: 99%

Newly identified energy levels and calculated transition rates in astatine atom, the rarest element on Earth

Quinet

Sicorello

2018

Journal of Quantitative Spectroscopy and Radiative Transfer

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A theoretical investigation of the atomic structure and radiative parameters involving the lowest states within the 6p 5 , 6p 4 7s and 6p 4 7p configurations of neutral astatine is reported for the first time in the present paper. Using different physical models based on the pseudo-relativistic Hartree-Fock approach, the influence of intravalence, core-valence and core-core electron correlation on the atomic parameters is discussed in detail. This work allowed us to establish the intermediate-coupling composition and to clearly fix the spectroscopic designation of six excited levels within the 6p 4 7s and 6p 4 7p configurations which had been located in previous experimental studies. In addition new tentative identifications of four levels belonging to the 6p 4 9p and 6p 4 10p configurations are reported in this work together with predicted level energies along the 6p 4 n p and 6p 4 n d Rydberg series up to n = 50.

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“…Significant progress has been made in nucleophilic radiofluorination of aromatic compounds, including the well‐explored route using diaryliodonium salts as precursors . Radiochlorination, radiobromination, radioiodonation, and radioastatination using diaryliodonium precursors have also been reported and shown to have promise for the labeling of aromatic compounds with radiohalogens. However, the report on radiobromination only demonstrated the feasibility of such reaction, and an in‐depth exploration is needed.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of aromatic radiobromination by nucleophilic substitution using diaryliodonium salt precursors

Kim

Chu

Voller

et al. 2017

Labelled Comp Radiopharmac

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Radiobromine labelled compounds can be used for positron emission tomography (PET) imaging (i.e. 76Br) and for radiation therapy (i.e. 77Br). However, the commonly used electrophilic substitution reaction using no-carrier-added (NCA) radiobromide does not always afford the desired product due to the high reactivity of the brominating intermediate. A nucleophilic substitution by bromide, such as radiobromination of iodonium precursors, provides an alternative route for the synthesis of bromo-radiopharmaceuticals. The applicability of aromatic radiobromination by nucleophilic substitution using diaryliodonium salt precursors was evaluated using iodonium model compounds and [76Br]/[77Br]bromide. Radiobromination was observed under all conditions tested, in up to quantitative yields. A QMA cartridge treatment method and a base-free method have been developed, and no extra base is needed for either method. The base-free conditions are mild and afford much cleaner reactions. Up to 20% water is tolerated in the reactions without reducing the radiochemical yields. NCA and carrier-added reactions afforded similar results. 4-Bromobenzaldehyde and 4-bromobenzoate have been radiosynthesized reliably and in good yields. These results indicate that this method is robust and efficient, and thus will provide a route for radiobromination of electron-deficient arenes and an alternative route for the synthesis of bromo-radiopharmaceuticals for biological evaluations.

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Unexpected Behavior of the Heaviest Halogen Astatine in the Nucleophilic Substitution of Aryliodonium Salts

Cited by 3 publications

References 43 publications

Astatine

Astatine

Newly identified energy levels and calculated transition rates in astatine atom, the rarest element on Earth

Evaluation of aromatic radiobromination by nucleophilic substitution using diaryliodonium salt precursors

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