Fluorine-19 NMR study of the reaction of p-fluorobenzenethiol and disulfide with periodate and other selected oxidizing agents

Evans, Brian J.; Doi, Joyce Takahashi; Musker, W. Kenneth

doi:10.1021/jo00295a020

Cited by 62 publications

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“…1,3,4,10 With growing interest in hypoxia, comes an increased need for new tools that researchers can use to detect hypoxia in biological systems. Fluorescent probes for the direct imaging of cellular hypoxia could provide a useful complement to radiochemical imaging 11 and immunohistochemical staining methods. 12 …”

Section: Introductionmentioning

confidence: 99%

Hypoxia-Selective, Enzymatic Conversion of 6-Nitroquinoline into a Fluorescent Helicene: Pyrido[3,2-f]quinolino[6,5-c]cinnoline 3-Oxide

Rajapakse

Gates

2012

J. Org. Chem.

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Regions of low oxygen concentration (hypoxia) occur in both normal human physiology and under pathophysiological conditions. Fluorescent probes for the direct imaging of cellular hypoxia could be useful tools that complement radiochemical imaging and immunohistochemical staining methods. In this work, we set out to characterize the hypoxia-selective enzymatic conversion of a simple nitroaryl probe, 6-nitroquinoline (1). We envisioned that this compound might undergo hypoxia-selective, bioreductive conversion to the fluorescent product, 6-aminoquinoline (2, Scheme 2). The probe 1 was, indeed, converted to a fluorescent product selectively under hypoxic conditions by the one-electron reducing enzyme NADPH: cytochrome P450 reductase. However, inspection of the fluorescence spectrum and LC/MS analysis of the reaction mixture revealed that the expected product 2 was not formed. Rather, the 63-fold increase in fluorescence emission at 445 nm resulting from the hypoxic metabolism of 1 was due to formation of the azoxy-helicene product, pyrido[3,2-f]quinolino[6,5-c]cinnoline 3-oxide (4). The generation of 4 involves an unusual biaryl bond formation under reductive conditions. The mechanism of this process remains uncertain, but could proceed via combination of a nitroaryl radical anion with a neutral nitrosoaryl radical, followed by tautomerization and intramolecular condensation between the resulting hydroxylamine and nitroso functional groups. Bioreductive metabolism of nitroaryl compounds represents a promising strategy for the selective delivery of cytotoxic agents and fluorescent markers to hypoxic tissue, but the results described here provide a important glimpse of the chemical complexity that can be associated with the enzymatic one-electron reduction of nitroaryl compounds.

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Section: Introductionmentioning

confidence: 99%

Hypoxia-Selective, Enzymatic Conversion of 6-Nitroquinoline into a Fluorescent Helicene: Pyrido[3,2-f]quinolino[6,5-c]cinnoline 3-Oxide

Rajapakse

Gates

2012

J. Org. Chem.

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“…On the basis of studies [12,13] on the oxidation of thiolsulfinates with periodate, Oae [14] supposed, however, that the oxidation of sulfides with periodate occurs by the rate-determining attack of sulfur on the central iodine atom of periodate (1 + 6 w 7, Scheme 1) and a subsequent ligand-coupling reaction of the supposed trigonal bipyramidal intermediate (7). On the other hand, Musker and coworkers [15,16] proposed the formation of a mixed anhydride intermediate of sulfinic and iodic acids (RSO-IO 3 ) for the periodate oxidation of thiols and disulfides rather than the oxygen-transfer mechanism.…”

Section: Introductionmentioning

confidence: 99%

Mechanism for the Oxidation of Sulfides and Sulfoxides with Periodates: Reactivity of the Oxidizing Species

et al. 2009

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DFT computations have been performed at different levels of theory to identify the mechanism for the oxidation of sulfides and sulfoxides with periodates. The periodate ion (IO 4 -), periodic acid (HIO 4 ) and their hydrated derivatives all oxidize sulfides to sulfoxides in one-step oxygen-transfer reactions and the relative reactivities are HIO 4 ϾϾ H 5 IO 6 Ͼ IO 4 -Ͼ H 4 IO 6 -ϾϾ H 3 IO 6 2-. The hydration and dissociation equilibria of the periodates are shifted towards IO 4 -in neutral and moderately acidic solutions, and sulfides are oxidized mainly with IO 4 -under normal experimental conditions. The oxygen atoms of the periodates attack the sulfides perpendicularly to the plane of the C-S-C atoms and the S···O···I atoms are in a linear arrangement in the very early transition state (TS). The sulfides are the electron donors and periodates are the

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“…60 Other smaller peaks between −110 and −115 ppm are likely due to byproducts formed from reactions of sulfenylnitrite, formed from isomerization of the thionitrate as shown in eq 4, including sulfinate, sulfonate, and sulfonic acid derivatives of the 4-fluorothiophenol. 61 …”

Section: 0 Results and Discussionmentioning

confidence: 99%

Role of Crystal Structure and Chalcogenide Redox Properties on the Oxidative Assembly of Cadmium Chalcogenide Nanocrystals

2017

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Oxidative assembly of metal chalcogenide nanocrystals (NCs) enables the formation of 2-D (dense) and 3-D porous structures without the presence of intervening ligands between particles that can moderate transport properties. This route has been demonstrated to be successful for a range of single-component structures including CdQ, PbQ, and ZnQ (Q = S, Se, Te). En route to the controllable assembly of multicomponent nanostructures, the roles of Q redox properties (2Q2− → Q22− + 2e) responsible for particle cross-linking and the native structure (cubic zinc blende vs hexagonal wurtzite) in the kinetics of assembly in single-component CdQ NCs are evaluated using time-resolved dynamic light scattering (TR-DLS). For wurtzite CdQ, the rates follow the ease of oxidation, with telluride as the fastest, followed by selenide and sulfide. However, when comparing CdS wurtzite (w) and zinc blende (zb), the cubic NCs exhibit surprisingly slow kinetics. NMR studies reveal the zb structure to have lower ligand coverage (by a factor of 4) relative to that of w, and the formation of free disulfide (the product of ligand oxidation) is slow. This is attributed to differences in the surface energies of w and zb facets, with w having polar (0001) facets of high energy compared to the neutral facets of the zb structure. The zb-CdS NCs prepared by low-temperature synthesis methods are likely to suffer from surface defects that may moderate reactivity. EPR studies suggest that zb-CdS has paramagnetic sulfur vacancies not present in w-CdS. These data suggest that structure plays an unexpectedly large role in the kinetics of CdQ NC oxidative assembly, providing a useful lever to moderate activities in multicomponent assemblies.

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Fluorine-19 NMR study of the reaction of p-fluorobenzenethiol and disulfide with periodate and other selected oxidizing agents

Cited by 62 publications

References 0 publications

Hypoxia-Selective, Enzymatic Conversion of 6-Nitroquinoline into a Fluorescent Helicene: Pyrido[3,2-f]quinolino[6,5-c]cinnoline 3-Oxide

Hypoxia-Selective, Enzymatic Conversion of 6-Nitroquinoline into a Fluorescent Helicene: Pyrido[3,2-f]quinolino[6,5-c]cinnoline 3-Oxide

Mechanism for the Oxidation of Sulfides and Sulfoxides with Periodates: Reactivity of the Oxidizing Species

Role of Crystal Structure and Chalcogenide Redox Properties on the Oxidative Assembly of Cadmium Chalcogenide Nanocrystals

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