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• 106-22-9 Citronellol 
• 57-88-5 cholesterol 

Relevant academic research and scientific papers

Preparative oxidation of organic compounds in microemulsions with singlet oxygen generated chemically by the sodium molybdate/hydrogen peroxide system

A reverse (water in oil) microemulsion has been designed to oxidize hydrophobic organic substrates with singlet oxygen (1O2, 1Δ(g)) generated from the disproportionation of hydrogen peroxide catalyzed by molybdate ions. The microemulsion was prepared by mixing methylene chloride, sodium dodecylsulfate, n-butanol, and aqueous molybdate. Flash photolysis studies have shown that in such media singlet oxygen exhibits a similar kinetic behavior that under homogeneous conditions (τ(Δ) ? 42 μs). Various typical organic substrates have been oxidized on the preparative scale with this chemically generated singlet oxygen, and the expected oxidation products have been isolated in high yields.

Covalently immobilized porphyrins on silica modified structures as photooxidation catalysts

Heterogeneous photooxidation catalysts were prepared by the covalent linkage of a porphyrin to aminoalkylated silica particles by chlorosulphonation activation of the porphyrin nucleus. These catalysts were tested in [4+2] cycloaddition and ene reactions promoted by singlet oxygen. Photooxidation of substrates originates high yields of products but with longer reaction times compared to the free porphyrin catalysts. Quenching of singlet oxygen by the silica structure can be the plausible explanation. In the case of the ene reaction with citronellol the supported catalysts originate a distribution of the regioisomeric products which is opposite to that of the homogeneous catalyst.

Lanthanum(III)-catalyzed disproportionation of hydrogen peroxide: A heterogeneous generator of singlet molecular oxygen - 1O2 (1δg) - in near-neutral aqueous and organic media for peroxidation of electron-rich substrates

The decomposition of hydrogen peroxide into singlet molecular oxygen - 1O2 (1δg) - in the presence of lanthanum(III) salts was studied by monitoring its characteristic IR luminescence at 1270nm. The process was found to be heterogeneously catalyzed by LaIII, provided that the heterogeneous catalyst is generated in situ. The yield of 1O2 generation was assessed as 45 ± 5% both in water and in methanol. The pH-dependence on the rate of 1O2 generation corresponds to a bell-shaped curve from pH 4.5 to 13 with a maximum around pH 8. The study of the influence of H2O2 showed that the formation of 1O2 begins as soon as one equivalent of H2O2 is introduced. It then increases drastically up to two equivalents and more smoothly above. Unlike all other metal salt catalyst systems known to date for H2O2 disproportionation, this chemical source of 1O2 is able to generate 102 not only in basic media, but also under neutral and slightly acidic conditions. In addition, this La-based catalyst system has a very low tendency to induce unwanted oxygenating side reactions, such as epoxidation of alkenes. These two characteristics of the heterogeneous lanthanum catalyst system allow non-photochemical (i.e., "dark") singlet oxygenation of substrate classes that cannot be peroxidized successfully with conventional molybdate catalysts, such as allylic alcohols and alkenyl amines.

Dimethylsulfoxide as a kinetic booster for the chemical generation of singlet oxygen in methanol

The kinetic booster effect of dimethylsulfoxide on the chemical generation of singlet oxygen, 1O2, from the disproportionation of hydrogen peroxide catalyzed by molybdate ions in methanol has been evidenced by detection of the IR luminescence of 1O2 at 1270 nm and by 95Mo NMR spectroscopy. DMSO interacts rapidly, through a direct oxygen transfer with the stable tetraperoxomolybdate Mo(O2) 42-, leading to DMSO2 and to the unstable triperoxomolybdate Mo(02)32-, which releases 1O2. The procedure was applied to accelerate the dark singlet oxygenation of β-citronellol and α-terpinene.

ON THE USE OF METHYL SUBSTITUTED POLY(VINYLNAPHTHALENE) AS A REVERSIBLE SINGLET OXYGEN CARRIER

Poly(1,4-dimethyl-6-vinylnaphthalene) and poly(1,2,4-trimethyl-6-vinylnaphthalene) react with singlet oxygen to give corresponding endoperoxide polymers which on warming generate singlet oxygen efficiently.Singlet oxygenations by the use of these polymers have been described.

Immobilised porphyrins in monoterpene photooxidations

Porphyrins were covalently linked to modified Merrifield polymers by chlorosulphonation activation of the porphyrin nucleus. These supported porphyrins were used as photosensitizers to promote singlet oxygen oxidation of monoterpenes with an efficiency that depends on porphyrin structure and the spacer used to link it to the polymer structure. The performance of these photosensitizers was studied. Citronellol and α-terpinene gave the expected singlet oxygen ene addition products. α-Pinene and β-pinene also gave products from non-ene reactions, which is explained by the existence of an alternative radical pathway.

An entirely solvent-free photooxygenation of olefins under continuous flow conditions

Photooxygenations of alkenes with singlet oxygen are a versatile, atom-economical transformation. The choice of solvents is key to the success of this oxyfunctionalization with direct impact on the solubility of substrates, the lifetime of the reactive oxygen species, and the up-scaling of the process. We report an entirely solvent-free continuous-flow photooxygenation that operates at very high substrate/sensitizer ratios and enables high space-time yields.

Comparison of photo-oxidation reactions in batch and a new photosensitizer-immobilized microfluidic device

A glass microfluidic device has been functionalized with photoactive porphyrins for performing reactions which are mediated by singlet molecular oxygen. The resulting device was used to investigate the photochemical oxidation of cholesterol, α-terpinene, and citronellol under flow conditions, and the results were compared with similar batch reactions.

Kinetics of the oxygenation of unsaturated organics with singlet oxygen generated from H2O2 by a heterogeneous molybdenum catalyst

A heterogeneous catalyst containing MoO42- exchanged on layered double hydroxides (Mo-LDHs) is used to produce 1O 2 from H2O2, and with this dark 1O2, unsaturated hydrocarbons are oxidized in allylic peroxides. The oxidation kinetics are studied in detail and are compared with the kinetics of oxidation by 1O2, formed from H 2O2 by a homogeneous catalyst. A model is proposed for the heterogeneously catalyzed 1O2 generation and peroxide formation. The model divides the reaction suspension in two compartments: (1) the intralamellar and intragranular zones of the LDH catalyst; (2) the bulk solution. The 2-compartment model correctly predicts the oxidant efficiency and peroxide yield for a series of olefin peroxidation reactions. 1O 2 is generated at a high rate by the heterogeneous catalyst, but somewhat more 1O2 is lost by quenching with the heterogeneous catalyst than using the homogeneous catalyst. Quenching occurs mainly as a result of collision with the LDH hydroxyl surface, as is evidenced by using LDH supports containing strong 1O2 deactivators such as Ni2+. A total of 15 organic substrates were peroxidized on a preparative scale using the best Mo-LDH catalyst under optimal conditions.

Glycol-modified molybdate catalysts for efficient singlet oxygen generation from hydrogen peroxide

Pretreatment of molybdate-exchanged layered double hydroxides in polyalcohols such as ethylene glycol affords heterogeneous catalysts showing largely improved oxidant efficiency compared to the unmodified materials. The Royal Society of Chemistry.