Potassium carbonate–silica: a highly effective stationary phase for the chromatographic removal of organotin impurities

Harrowven, David C.; Curran, Dennis P.; Kostiuk, Sarah L.; Wallis-Guy, Ian L.; Whiting, Sally; Stenning, Kerri J.; Tang, Bencan; Packard, Emma; Nanson, Lana

doi:10.1039/c0cc01328e

Cited by 95 publications

(97 citation statements)

References 48 publications

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“…51 The tin byproducts were removed by passing the reaction mixture through silica gel and (10 wt %) potassium carbonate. 52 The C^N ligands, L1 – L4 , were complexed with either IrCl 3 ·3H 2 O or [Ir(COD)(μ-Cl)] 2 (where COD = 1,5-cyclooctadiene) and the resulting μ-dichloro-bridged iridium dimers [Ir( L1 ) 2 (μ-Cl)] 2 , D-L1 ; [Ir( L2 ) 2 (μ-Cl)] 2 , D-L2 ; [Ir( L3 ) 2 (μ-Cl)] 2 , D-L3 ; and [Ir( L4 ) 2 (μ-Cl)] 2 , D-L4 were formed in good yields under standard conditions 53 and were used without further purification. The heteroleptic cationic iridium(III) complexes 1 – 4 were isolated in high yields through cleavage of D-L1 – D-L4 with the d t Bubpy ligand.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, Properties, and Light-Emitting Electrochemical Cell (LEEC) Device Fabrication of Cationic Ir(III) Complexes Bearing Electron-Withdrawing Groups on the Cyclometallating Ligands

et al. 2016

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The structure–property relationship study of a series of cationic Ir(III) complexes in the form of [Ir(C^N)2(dtBubpy)]PF6 [where dtBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine and C^N = cyclometallating ligand bearing an electron-withdrawing group (EWG) at C4 of the phenyl substituent, i.e., −CF3 (1), −OCF3 (2), −SCF3 (3), −SO2CF3 (4)] has been investigated. The physical and optoelectronic properties of the four complexes were comprehensively characterized, including by X-ray diffraction analysis. All the complexes exhibit quasireversible dtBubpy-based reductions from −1.29 to −1.34 V (vs SCE). The oxidation processes are likewise quasireversible (metal + C^N ligand) and are between 1.54 and 1.72 V (vs SCE). The relative oxidation potentials follow a general trend associated with the Hammett parameter (σ) of the EWGs. Surprisingly, complex 4 bearing the strongest EWG does not adhere to the expected Hammett behavior and was found to exhibit red-shifted absorption and emission maxima. Nevertheless, the concept of introducing EWGs was found to be generally useful in blue-shifting the emission maxima of the complexes (λem = 484–545 nm) compared to that of the prototype complex [Ir(ppy)2(dtBubpy)]PF6 (where ppy = 2-phenylpyridinato) (λem = 591 nm). The complexes were found to be bright emitters in solution at room temperature (ΦPL = 45–66%) with microsecond excited-state lifetimes (τe = 1.14–4.28 μs). The photophysical properties along with density functional theory (DFT) calculations suggest that the emission of these complexes originates from mixed contributions from ligand-centered (LC) transitions and mixed metal-to-ligand and ligand-to-ligand charge transfer (LLCT/MLCT) transitions, depending on the EWG. In complexes 1, 3, and 4 the 3LC character is prominent over the mixed 3CT character, while in complex 2, the mixed 3CT character is much more pronounced, as demonstrated by DFT calculations and the observed positive solvatochromism effect. Due to the quasireversible nature of the oxidation and reduction waves, fabrication of light-emitting electrochemical cells (LEECs) using these complexes as emitters was possible with the LEECs showing moderate efficiencies.

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Section: Resultsmentioning

confidence: 99%

Synthesis, Properties, and Light-Emitting Electrochemical Cell (LEEC) Device Fabrication of Cationic Ir(III) Complexes Bearing Electron-Withdrawing Groups on the Cyclometallating Ligands

et al. 2016

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“…However, furan and thiophene groups were successfully transferred, affording substrates 13 and 14 in excellent yields of 90% and 94% yield, respectively. The Stille products, following an aqueous work-up and purification (K 2 CO 3 /SiO 2 chromatography), 44 contained 10.5 ppm Pd, 7.9 ppm Sn and As and undetectable levels of Cu as detected by inductively coupled plasma mass spectrometry (ICPMS) trace element analyses (for details, see Supplementary Information). …”

Section: Resultsmentioning

confidence: 99%

Synthesis of 19-substituted geldanamycins with altered conformations and their binding to heat shock protein Hsp90

et al. 2013

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The benzoquinone ansamycin geldanamycin and its derivatives are inhibitors of heat shock protein Hsp90, an emerging target for novel therapeutic agents both in cancer and in neurodegeneration. However, toxicity of these compounds to normal cells has been ascribed to reaction with thiol nucleophiles at the quinone 19-position. We reasoned that blocking this position would ameliorate toxicity, and that it might also enforce a favourable conformational switch of the trans-amide group into the cis-form required for protein binding. We report here an efficient synthesis of such 19-substituted compounds and realization of our hypotheses. Protein crystallography established that the new compounds bind to Hsp90 with, as expected, a cis-amide conformation. Studies on Hsp90 inhibition in cells demonstrated the molecular signature of Hsp90 inhibitors: decreases in client proteins with compensatory increases in other heat shock proteins in both human breast cancer and dopaminergic neural cells, demonstrating their potential for use in the therapy of cancer or neurodegenerative diseases.

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“…The effectiveness of various additives on the chromatographic removal of residual tin was recently evaluated by the groups of Harrowven and Curran; 31 certain fluoride, acetate, and carbonate salts were found to be particularly effective at reducing residues to less than 100 ppm with potassium carbonate and potassium fluoride being particularly effective ( Table 1). 31 This method has been used in a synthesis of (þ)-pseudococaine, where iodine-mediated cyclization is followed by radical dehalogenation and chromatography on silica gel containing 10% KF (Scheme 17). 32 Isotopically labeled stannanes may be prepared and used to introduce deuterium and even tritium labels to compounds.…”

Section: Cr(ii) Complexesmentioning

confidence: 99%

8.26 Reduction of Saturated Alkyl Halides to Alkanes

Ziffle

Fletcher

2014

Comprehensive Organic Synthesis II

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Potassium carbonate–silica: a highly effective stationary phase for the chromatographic removal of organotin impurities

Abstract: Organotin impurities in product mixtures can be reduced from stoichiometric levels to approximately 15 parts per million by column chromatography using 10% w/w anhydrous potassium carbonate-silica as a stationary phase.

Cited by 95 publications

References 48 publications

Synthesis, Properties, and Light-Emitting Electrochemical Cell (LEEC) Device Fabrication of Cationic Ir(III) Complexes Bearing Electron-Withdrawing Groups on the Cyclometallating Ligands

Synthesis, Properties, and Light-Emitting Electrochemical Cell (LEEC) Device Fabrication of Cationic Ir(III) Complexes Bearing Electron-Withdrawing Groups on the Cyclometallating Ligands

Synthesis of 19-substituted geldanamycins with altered conformations and their binding to heat shock protein Hsp90

8.26 Reduction of Saturated Alkyl Halides to Alkanes

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