Singlet Oxygen Photo‐Oxygenation in Water/Pluronic F‐127 Hydrogels: Increased Reaction Efficiency Coupled with a Switch in Regioselectivity

Griesbeck, Axel G.; Uhlig, Johannes; Sottmann, Thomas; Belkoura, L.; Strey, R.

doi:10.1002/chem.201202296

Cited by 10 publications

(7 citation statements)

References 40 publications

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“…This effect is nearly independent of the nature of the allylic substituent X. Under restricted environment conditions, however, this selectivity is altered: in zeolites, the twix selectivity dominates strongly, whereas in microemulsions and more noticeably in hydrogels, hydrogen abstraction from the lone methylene group becomes prevalent . Another very strong regiodirecting effect was observed for acceptor-substituted 2-butenes.…”

Section: Resultsmentioning

confidence: 96%

Ene–Diene Transmissive Cycloaddition Reactions with Singlet Oxygen: The Vinylogous Gem Effect and Its Use for Polyoxyfunctionalization of Dienes

et al. 2014

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The singlet oxygen reactivities and regioselectivities of the model compounds 1b-d were compared with those of the geminal (gem) selectivity model ethyl tiglate (1a). The kinetic cis effect is k(E)/k(Z) = 5.2 for the tiglate/angelate system 1a/1a' without a change in the high gem regioselectivity. Further conjugation to vinyl groups enabled mode-selective processes, namely, [4 + 2] cycloadditions versus ene reactions. The site-specific effects of methylation on the mode selectivity and the regioselectivity of the ene reaction were studied for dienes 1e-g. A vinylogous gem effect was observed for the γ,δ-dimethylated and α,γ,δ-trimethylated substrates 1h and 1i, respectively. The corresponding phenylated substrates 1j-l showed similar mode selectivity, as monomethylated 1j exhibited exclusively [4 + 2] reactivity while the tandem products 12 and 14 were isolated from the di- and trimethylated substrates 1k and 1l, respectively. The vinylogous gem effect favors the formation of 1,3-dienes from the substrates, and thus, secondary singlet oxygen addition was observed to give hydroperoxy-1,2-dioxenes 19 and 20 in an ene-diene transmissive cycloaddition sequence. These products were reduced to give alcohols (16, 17, and 18) or furans (24 and 25), respectively, or treated with titanium(IV) alkoxides to give the epoxy alcohols 26 and 27. The vinylogous gem effect is rationalized by DFT calculations showing that biradicals are the low-energy intermediates and that no reaction path bifurcations compete.

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Section: Resultsmentioning

confidence: 96%

Ene–Diene Transmissive Cycloaddition Reactions with Singlet Oxygen: The Vinylogous Gem Effect and Its Use for Polyoxyfunctionalization of Dienes

et al. 2014

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“…Additionally, solvent polarity effects do alter the regio‐ and diastereoselectivity of the ene reaction. This can also be observed for constrained anisotropic media such as polymer films, hydrogels, zeolites, cyclodextrines, micelles, octaacid and many more. These constrained media can exhibit two influences of the processes investigated here: steric constraint and Coulombic effects.…”

Section: Introductionmentioning

confidence: 79%

Two Useful Directing Modes in Singlet Oxygen Reactivity: Electrostatic Effects in the Ene Reaction with Allylic Alcoholates and a Chemoselectivity Change with α‐Alkoxy Michael Esters

et al. 2018

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The singlet oxygen reaction with trisubstituted E‐allylic alcohols resulted in the unselective formation of regioisomeric secondary and tertiary allylic hydroperoxides. Increasing the steric demand at the allylic hydroxymethyl group leads to a moderate large‐group effect that can be strongly enhanced by deprotonation of a dimethylated allylic alcohol and even more pronounced by cation complexation. The presence of alkoxide groups did additionally alter the diastereoselectivity of the singlet oxygen ene reactions with chiral allylic alcohols. The molecular combination of Michael ester and enol ether in α‐alkoxy ester substrates made possible the design of chemoselective substrates for singlet oxygen ene versus [2+2] cycloaddition, e. g. a 3,3‐dimethylated Michael ester as a selective substrate for the ene reaction and an adamantyl analogue as a selective 2+2 substrate. The Z/E‐monomethylated substrates as probes for cis regioselectivity revealed that there is no site preference for Z‐alkoxy hydrogen transfer on the way to the corresponding ene product.

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“…The increase in the τ obs2 from 320 to 550 μs is attributed to the presence of the anthracene (DMA) trapping agent (50 μmol/g) to quench 1 O 2 in the former. Because anthracene trapping agents are known to mainly quench 1 O 2 chemically and not physically, ,,, the approximate DMA consumption as a function of the irradiation time and particle density permitted conversion of units from μmol/g to molar. Similar to the indirect determination of the Φ Δ , a pseudo-first-order kinetic for this reaction was proposed (eqs S3–S6).…”

Section: Resultsmentioning

confidence: 99%

Interparticle Delivery and Detection of Volatile Singlet Oxygen at Air/Solid Interfaces

Durantini

Greer

2021

Environ. Sci. Technol.

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An interparticle system has been devised, allowing airborne singlet oxygen to transfer between particle surfaces. Singlet oxygen is photogenerated on a sensitizer particle, where it then travels through air to a second particle bearing an oxidizable compounda particulate-based approach with some similarities to reactive oxygen quenching in the atmosphere. In atmospheric photochemistry, singlet oxygen is generated by natural particulate matter, but its formation and quenching between particles has until now not been determined. Determining how singlet oxygen reacts on a second surface is useful and was developed by a three-phase system (particle–air–particle) interparticulate photoreaction with tunable quenching properties. We identify singlet oxygen quenching directly by near-IR phosphorescence in the airborne state and at the air/particle interface for total quenching rate constants (k T) of adsorbed anthracene trapping agents. The air/solid interface k T of singlet oxygen by anthracene-coated particles was (2.8 ± 0.8) × 107 g mol–1 s–1 for 9,10-dimethylanthracene and (2.1 ± 0.9) × 107 g mol–1 s–1 for 9,10-anthracene dipropionate dianion, and the lifetime of airborne singlet oxygen was measured to be 550 μs. These real-time interactions and particle-induced quenching steps open up new opportunities for singlet oxygen research of atmospheric and particulate processes.

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Singlet Oxygen Photo‐Oxygenation in Water/Pluronic F‐127 Hydrogels: Increased Reaction Efficiency Coupled with a Switch in Regioselectivity

Cited by 10 publications

References 40 publications

Ene–Diene Transmissive Cycloaddition Reactions with Singlet Oxygen: The Vinylogous Gem Effect and Its Use for Polyoxyfunctionalization of Dienes

Ene–Diene Transmissive Cycloaddition Reactions with Singlet Oxygen: The Vinylogous Gem Effect and Its Use for Polyoxyfunctionalization of Dienes

Two Useful Directing Modes in Singlet Oxygen Reactivity: Electrostatic Effects in the Ene Reaction with Allylic Alcoholates and a Chemoselectivity Change with α‐Alkoxy Michael Esters

Interparticle Delivery and Detection of Volatile Singlet Oxygen at Air/Solid Interfaces

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