Reaction of singlet oxygen with some benzylic sulfides

Product distribution, total quenching rate (k_T), and rate of chemical reaction (k_r) with singlet oxygen have been determined for some alkyl, benzyl, α-methylbenzyl, and cumyl sulfides. Their contributions depend on the steric hindering around the sulfur atom. In protic solvents, the sulfoxide is the main product via a hydrogen-bonded persulfoxide. In apolar solvents, intramolecular α-H abstraction leads to oxidative C-S bond cleavage, with varying efficiency. The behavior of sulfides is compared to that of alkenes and amines.     

Reaction of singlet oxygen with azines: Implications for dioxirane intermediate

Photooxygenation of tricyclo[3.3.1.1]decanone azine (adamantanone azine) afforded, in addition to adamantanone, 4-oxahomoadamantan-5-one derived from a dioxirane intermediate via a non-radical pathway.     

Reaction of singlet oxygen with thioanisole in ionic liquid-acetonitrile binary mixtures

A study of the reaction of thioanisole with singlet oxygen in different ionic liquid-acetonitrile binary mixtures has shown that ILs are able to accelerate the thioanisole sulfoxidation when used as additives. With imidazolium ILs, the maximum efficiency is reached at x(IL) ～ 0.1-0.2, whereas for the pyrrolidinium IL a plateau is reached. These results are discussed in terms of the ILs' tendency to form ionic aggregates and of differences in sulfoxidation reaction mechanism.     

Reaction of diphenyldiazomethane with singlet oxygen studied by time-resolved IR spectroscopy

The mechanism of the reaction of diphenyldiazomethane 4a with singlet oxygen has been investigated by nanosecond time-resolved UV-vis (LFP) and IR (step-scan) spectroscopy. The experiments were performed with fullerene (C60) as photosensitizer for the generation of (1)O2 in nonpolar solvents (toluene and CCl4). The UV-vis experiments allowed us to monitor the formation of benzophenone O-oxide 1a, while in the IR experiments the bleaching of 4a and the formation of benzophenone 7a and N2O was observed. The kinetic data were evaluated using Monte Carlo simulation and DFT calculations. These methods allow us to present a consistent mechanistic scheme for the reaction of 4a with (1)O2 and to explain why the elusive dioxadiazole 5a as key intermediate is not directly observed.     

反,反,顺-2,4,7-十四碳三烯与单重态氧的反应

Nugtern等人关于不饱和酯肪酸经自动氧化生成少量具有生物活性的前列腺素类似物的报道,为人工非酶仿生合成前列腺素开辟了新途径.Sammuelsson认为,在生物体中合成前列腺素过程中生成的双环过氧化物,类似于单重态氧与1,4-二烯反应的产物.Mihelich     

Reaction of singlet oxygen with thiirane: Implication for a spirodioxathiirane intermediate

Photosensitized oxygenation of biadamantylidene thiirane afforded, in addition to the corresponding thiirane oxide, the desulfurization products i.e., biadamantylidene and its oxidized products, dioxetane and oxirane, via a spirodioxathiirane intermediate.     

Reaction of singlet oxygen with styrene-butadiene copolymer: 2. Determination of kinetic parameters of photo-oxidation

The rate constant of the reaction of styrene-butadiene copolymer (SBR) with singlet oxygen and its reactivity index were estimated from an investigation of the influence of SBR on the quantum efficiency of the photo-peroxidation of 1,3-diphenylisobenzofuran (DPBF).     

Reaction of singlet oxygen with indanone phosphazine: formation of ketone and lactone

Photooxygenation of 1,1,3,3-tetramethyl-2-indanone triphenyl-phosphazine afforded, in addition to the parent indanone and triphenylphosphine oxide, 2,2,5,5-tetramethyl-3,4-benzo-3-penten-5-olide from a carbonyl oxide intermediate and also gave light emission.     

Reaction of singlet oxygen with styrene-butadiene copolymer: 1. 9-Methylanthracene photo-sensitized oxidation of styrene-butadiene copolymer

9-Methylanthracene (9MA) photo-sensitizes the oxidation of styrene-butadiene copolymer (SBR). This effect was explained as being associated mainly with the ability of 9MA to form singlet oxygen. The calculated quantum efficiency of singlet oxygen formation resulting from the quenching by oxygen of electronic excited states of 9MA is high (γ_Δ^M = 0·74 ± 0·04). This indicates that 9MA should be a rather efficient photo-sensitizer in photo-oxidation processes.     

Cytogenetic effects of singlet oxygen.

Singlet oxygen was generated in the gas phase at atmospheric pressure by the method of heterogeneous photosensitization. In vitro exposure of human lung WI-38 fibroblasts to gas-phase singlet oxygen resulted in sister chromatid exchange.     

Chemistry of singlet oxygen. XVIII. Rates of reaction and quenching of alpha-tocopherol and singlet oxygen

Abstract —α-Tocopherol scavenges singlet oxygen (produced by methylene blue photosensitization in methanol) by a combination of chemical reaction (4.6 times 10⁷M^-1s^-1) and quenching (6.2 times 10⁸M^-1 s^-1). The total rate of scavenging (6.7 times 10⁸ M^-1s^-1) makes it an effective protective agent against photooxidation mediated by singlet oxygen.     

Reactions of singlet oxygen with biomolecules

Rate constants of singlet oxygen quenching by glycyrrhetic acid, glycyrrhizic acid, isoliquiritigenin, licurazide,d-glucose, andl-arabinose were determined. An increase in the quenching rate constants by more than an order of magnitude is observed on going from aglycone to the corresponding glycoside.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 57–59, January, 1996.     

Chemistry of singlet oxygen with arylphosphines

The chemistry of singlet oxygen with a variety of arylphosphines has been studied. Rates of singlet oxygen removal by para-substituted arylphosphines show good correlation with the Hammett σ parameter (ρ=−1.53 in CDCl₃), and with the Tolman electronic parameter. The only products for the reactions of these phosphines with singlet oxygen are the corresponding phosphine oxides. Conversely, for ortho-substituted phosphines with electron-donating substituents, there are two products, namely a phosphinate formed by intramolecular insertion and phosphine oxide. Kinetic analyses demonstrate that both products are formed from the same intermediate, and this allows determination of the rate ratios for the competing pathways. Increasing the steric bulk of the phosphine leads to an increase in the amount of insertion product. VT NMR experiments show that peroxidic intermediates can only be detected for very hindered and very electron-rich arylphosphines.     

Reaction of singlet oxygen with sulfide: A similarity of singlet oxygenation and coupling reaction of cation radical and superoxide ion

Photosensitized oxygenation of 5H,7H-dibenzo[b,g][1,5]dithiocin afforded the sulfoxides. The reaction of its cation radical derived from oxidation by nitrosyl tetrafluoroborate with superoxide ion gave the same products.     

Reaction of cis- and trans-4-alkoxycarbonylamino-3-hydroxythiophans with thionyl chloride

The reaction of cis- and trans-4-alkoxycarbonylamino-3-hydroxythiophans with thionyl chloride gives chlorosulfites. trans-4-Alkoxycarbonylamino-3-chlorosulfito-thiophans are converted to cis-3a,4,6,6a-tetrahydrothieno[3,4-d]oxazolidone by heating or by treatment with pyridine. cis-4-Carboalkoxyamino-3-hydroxythiophans form 3-carboalkoxy-3a,4,6,6a-tetrahydrothieno[3,4-d]oxathiazolidones.     

Two-photon photosensitized production of singlet oxygen.

Singlet molecular oxygen (a(1)Delta(g)) has been produced and optically detected upon two-photon nonlinear excitation of a sensitizer with a focused laser beam. The experiments were performed using toluene solutions with either a substituted difuranonaphthalene or a substituted distyryl benzene as the sensitizer. The data indicate that the two-photon absorption cross sections of the difuranonaphthalenes are comparatively large and depend significantly on the functional groups attached to the chromophore. The time-resolved 1270 nm phosphorescence signals used to characterize the production of singlet oxygen are limited in much the same way as signals from other two-photon spectroscopic studies (e.g., weak signals that can be masked by scattered radiation). Nevertheless, the two-photon singlet oxygen signals also reflect the unique advantages of this nonlinear optical technique (e.g., depth penetration in the sample afforded by irradiation in a spectral region void of the more dominant one-photon linear transitions and spatial resolution afforded by irradiation with a focused laser beam).     

Reaction of dimethylamines with epimeric (at the 2 and 4 positions) trans-2-methyl- and trans-1,2-dimethyl-4-vinylethynyldecahydro-4-quinolols

A mixture of the corresponding 4-(4-dimethylamino-1,2-butadienyl)- and 4-(4-dimethylamino-1-butynyl)decahydro-4-quinolols, with predominance of the allene components, is formed from each vinylacetylenic alcohol as a result of the addition of diethylamine to epimeric (at the 2 and 4 positions) trans-2-methyl- and trans-1,2-dimethyl-4-vinylethynyldecahydro-4-quinolols. On the basis of the PMR spectra and data on the stabilities of allenic and acetylenic diamino alcohols under the conditions of their formation, it was concluded that the addition of dimethylamine to 4-vinylethynyldecahydro-4-quinolols proceeds simultaneously via two pathways — at the 1,4 and 3,4 positions of the vinylethynyl substituent.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 940–945, July, 1976.The authors thank A. S. Fridman and T. E. Prokof'ev for their participation in the discussion of the PMR spectra.