Search Results (9)

Background: N-succinimidyl-[¹⁸F]fluorobenzoate ([¹⁸F]SFB) is commonly prepared through a three-step procedure starting from [¹⁸F]fluoride ion. A number of methods for the single-step radiosynthesis of [¹⁸F]SFB have been introduced recently, including the radiofluorination of diaryliodonium salts and the Cu-mediated ¹⁸F-fluorination of pinacol aryl boronates and aryl tributyl stannanes, but they still have the drawbacks of lengthy product purification procedures. In the present work, two approaches for the direct labeling of [¹⁸F]SFB from diaryliodonium (DAI) salt (4) and pinacol aryl boronate (6) are evaluated, with a major focus on developing a fast and simple SPE-based purification procedure. Methods: DAI salt precursor 6 was labeled employing the common “minimalist” approach with a two-step reaction heating sequence. The Cu-mediated radiofluorination of 4 was accomplished using Bu₄NOTf as a phase transfer catalyst for the elution of [¹⁸F]fluoride, followed by radiofluorination in the same solvent. Several types of SPE cartridges were tested in the elution and SPE procedures. Results: The Cu-mediated ¹⁸F-fluorination of the pinacol aryl boronate precursor afforded a higher RCC of 56 ± 3% (n = 7), making it better suited for the one-pot synthesis of [¹⁸F]SFB. SPE-based purification was achieved using cation exchange and reverse-phase polymer resin cartridges, connected in series. In a full-batch test, [¹⁸F]SFB was obtained with an RCY of 30% (n. d. c.), RCP > 99%, A_m 96–155 GBq/µmol, and a synthesis time of ≤35 min. Conclusions: Compared to other published methods, [¹⁸F]SFB production via the Cu-mediated radiofluorination of pinacol aryl boronate precursor provides significant time and cost savings, coupled with an ease of implementation. Full article

Select triphenyl stannanes bearing either a formally sp² or sp³ hybridized amine, viz 2-(pyC₂H₄)SnPh₃ (2: py = pyridinyl), 4-(pyC₂H₄)SnPh₃ (3), 2-(pzC₂H₄)SnPh₃ (4: pz = pyrazyl), and Me₂N(CH₂)₃SnPh₃ (6), were prepared and characterized by NMR spectroscopy (¹¹⁹Sn, ¹³C, ¹H), and additionally, in the case of 2, by single crystal X-ray diffraction. Bromination of 2 to yield 2-(pyC₂H₄)SnPhBr₂ (8) was achieved in good yield. X-ray crystallographic analysis of 8 revealed two unique molecules with 5-coordinate Sn centers featuring Sn-N distances of 2.382 (5) and 2.363 (5) Å, respectively. The calculated structures of the non- and hypercoordinating C,N-stannanes (1–9) were in good agreement with available crystallographic data. The relative stabilities of hyper- and non-hypercoordinating conformers obtained from conformational sampling were determined by comparison with reference conformers and by natural bond orbital (NBO) energetic analyses. Reduction of 8 to the dihydride species, 2-(pyC₂H₄)SnPhH₂ (9), and subsequent conversion to the polystannane, -[2-(pyC₂H₄)SnPh]_n- (15), by transition metal-catalyzed dehydropolymerization was also achieved. Evidence for the decomposition of 15 into a redistributed distannoxane, {2-(pyC₂H₄)SnPh₂}₂O (16), was also observed. Full article

(1) Background: [¹⁸F]Flumazenil 1 ([¹⁸F]FMZ) is an established positron emission tomography (PET) radiotracer for the imaging of the gamma-aminobutyric acid (GABA) receptor subtype, GABA_A in the brain. The production of [¹⁸F]FMZ 1 for its clinical use has proven to be challenging, requiring harsh radiochemical conditions, while affording low radiochemical yields. Fully characterized, new methods for the improved production of [¹⁸F]FMZ 1 are needed. (2) Methods: We investigate the use of late-stage copper-mediated radiofluorination of aryl stannanes to improve the production of [¹⁸F]FMZ 1 that is suitable for clinical use. Mass spectrometry was used to identify the chemical by-products that were produced under the reaction conditions. (3) Results: The radiosynthesis of [¹⁸F]FMZ 1 was fully automated using the iPhase FlexLab radiochemistry module, affording a 22.2 ± 2.7% (n = 5) decay-corrected yield after 80 min. [¹⁸F]FMZ 1 was obtained with a high radiochemical purity (>98%) and molar activity (247.9 ± 25.9 GBq/µmol). (4) Conclusions: The copper-mediated radiofluorination of the stannyl precursor is an effective strategy for the production of clinically suitable [¹⁸F]FMZ 1. Full article

Radiolabeling of tetrazines has gained increasing attention due to their important role in pretargeted imaging or therapy. The most commonly used radionuclide in PET imaging is fluorine-18. For this reason, we have recently developed a method which enables the direct aromatic ¹⁸F-fluorination of tetrazines using stannane precursors through copper-mediated fluorinations. Herein, we further optimized this labeling procedure. 3-(3-fluorophenyl)-1,2,4,5-tetrazine was chosen for this purpose because of its high reactivity and respective limited stability during the labeling process. By optimizing parameters such as elution conditions, precursor amount, catalyst, time or temperature, the radiochemical yield (RCY) could be increased by approximately 30%. These conditions were then applied to optimize the RCY of a recently successfully developed and promising pretargeting imaging agent. This agent could be isolated in a decay corrected RCY of 14 ± 3% and Am of 201 ± 30 GBq/µmol in a synthesis time of 70 min. Consequently, the RCY increased by 27%. Full article

Tetraorganotin tin(IV) compounds containing a flexible or rigid (4: Ph₃Sn-CH₂-C₆H₄-R; 7: Ph₃SnC₆H₄-R, R = 2-oxazolinyl) chelating oxazoline functionality were prepared in good yields by the reaction of lithiated oxazolines and Ph₃SnCl. Reaction of 7 with excess HCl resulted in the isolation of the tin monochlorido compound, 9 (ClSn[Ph₂]C₆H₄-R). Conversion of the triphenylstannanes 7 and 4 into their corresponding dibromido species was successfully achieved from the reaction with Br₂ to yield 10 (Br₂Sn[Ph]C₆H₄-R) and 11 (Br₂Sn[Ph]-CH₂-C₆H₄-R), respectively. X-ray crystallography of 4, 7, 9, 10, and 11 reveal that all structures adopt a distorted trigonal bipyramidal geometry around Sn in the solid state. Compound 4, with an additional methylene spacer group, displays a comparatively long Sn–N bond distance compared to the dibromido tin species, 11. Several DFT methods were compared for accuracy in predicting the solid-state geometries of compounds 4, 7, 9–11. Compounds 10 and 11 were further converted into the corresponding dihydrides (12: H₂Sn[Ph]C₆H₄-R, 13: H₂Sn[Ph]-CH₂-C₆H₄-R), via Br–H exchange, in high yield by reaction with NaBH₄. Polymerization of 12 or 13 with a late transition metal catalyst produced a low molecular weight polystannane (14: –[Sn[Ph]C₆H₄-R]_n–, M_w = 10,100 Da) and oligostannane (15: –[Sn[Ph]-CH₂-C₆H₄-R]_n–, M_w = 3200 Da), respectively. Full article

Hydrogen interaction with ruthenium is of particular importance for the ruthenium-capped multilayer reflectors used in extreme ultraviolet (EUV) lithography. Hydrogen causes blistering, which leads to a loss of reflectivity. This problem is aggravated by tin. This study aims to uncover the mechanism via which tin affects the hydrogen uptake, with a view to mitigation. We report here the results of a study of hydrogen interaction with the ruthenium surface in the presence of tin using Density Functional Theory and charge density analyses. Our calculations show a significant drop in the energy barrier to hydrogen penetration when a tin atom or a tin hydride molecule (SnH_x) is adsorbed on the ruthenium surface; the barrier has been found to drop in all tested cases with tin, from 1.06 eV to as low as 0.28 eV in the case of stannane (SnH₄). Analyses show that, due to charge transfer from the less electronegative tin to hydrogen and ruthenium, charge accumulates around the diffusing hydrogen atom and near the ruthenium surface atoms. The reduced atomic volume of hydrogen, together with the effect of electron–electron repulsion from the ruthenium surface charge, facilitates subsurface penetration. Understanding the nature of tin’s influence on hydrogen penetration will guide efforts to mitigate blistering damage of EUV optics. It also holds great interest for applications where hydrogen penetration is desirable, such as hydrogen storage. Full article

Stille coupling of 5-chloro-4-oxo-4H-1,2,6-thiadiazin-3-yl trifluoromethanesulfonate (7) with tributyl(3-n-hexylthien-2-yl)stannane and Pd(Ph₃P)₂Cl₂ in PhMe at ca. 20 °C, for 24 h gave 3-chloro-5-(3-n-hexylthien-2-yl)-4H-1,2,6-thiadiazin-4-one (9) with a 60% yield. The latter is a potentially useful building block for the synthesis of oligomeric and polymeric donors for organic photovoltaics. Full article

The photostimulated reaction of Me₃Sn^- ion with mono, di and trichloro arenes in liquid ammonia gave very good yields of stannanes by the S_RN1 mechanism. These products reacted by a palladium-catalized cross coupling reaction with halobenzenes to give phenylated products also in very goods yields. Similar yields can be obtained in one-pot reactions. Full article