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Photosensitized reaction with oxygen

Butenes were subjected to photosensitized reaction with molecular oxygen in methanol. 1-Butene proved unreactive. A single hydroperoxide, l-butene-3-hydroperoxide, was produced from 2-butene and isolated by preparative gas chromatography, Thermal and catalyzed decomposition of pure hydroperoxide in benzene and other solvents did not result in formation of any acetaldehyde or propionaldehyde. The absence of these aldehydes suggests that they arise by an addition mechanism in the autoxidation of butenes where they are important products. l-Butene-3-hydroperoxide in the absence of catalyst is converted predominantly to methyl vinyl ketone and a smaller quantity of methyl vinyl carbinol —volatile products usually not detected in important quantities in the autoxidation of butene. [Pg.105]

Figure 10.23 Schematic depiction of photodynamic therapy (PDT) using a dendrimer with a protoporphyrin photosensitizer core, which upon irradiation with light and subsequent reaction with oxygen creates tissue-damaging singlet oxygen. Figure 10.23 Schematic depiction of photodynamic therapy (PDT) using a dendrimer with a protoporphyrin photosensitizer core, which upon irradiation with light and subsequent reaction with oxygen creates tissue-damaging singlet oxygen.
Complex reactions occur on the autoxidation of pyrroles (see Section 3.05.1.4) predictably, susceptibility to autoxidation increases with increasing alkyl substitution, llie photosensitized reaction of pyrrole and oxygen yields 5-hydroxy-A -pyrrolin-2-one, probably by way of an intermediate cyclic peroxide (Scheme 28) (76JA802). [Pg.57]

Katsumura, Kitaura and their coworkers [74] found and discussed the high reactivity of vinylic vs allylic hydrogen in the photosensitized reactions of twisted 1,3-dienes in terms of the interaction in the perepoxide structure. Yoshioka and coworkers [75] investigated the effects of solvent polarity on the product distribution in the reaction of singlet oxygen with enolic tautomers of 1,3-diketones and discussed the role of the perepoxide intermediate or the perepoxide-Uke transition state to explain their results. A recent review of the ene reactions of was based on the significant intervention of the perepoxide structure [76], which can be taken as a quasi-intermediate. [Pg.38]

Wasserman and Keehn ") have also carried out the photosensitized auto-oxidation of anti-[2.2](l,4)naphthalenophane (34A). Irradiation of anti-34 in methanol and simultaneous reaction with singlet oxygen affords the oxidation product 127 in 20% yield. The primary step in the reaction is assumed to be formation of a peroxide (128) whose geometry permits an intra-annular Diels—Alder reaction as second step methanol-ysis then leads to 127 which was isolated. [Pg.116]

Enamines, reaction with quinones, 20, 3 Enantioselective aldol reactions, 67, 1 allylation and crotylation, 73, 1 Ene reaction, in photosensitized oxygenation, 20, 2 Enolates ... [Pg.589]

The method of photosensitized oxygenation was successfully applied in the preparation of alcohols 265-270 from sylvestrene (264),207 and seems to be the most simple and successful method for the preparation of optically active rose oxides (272,273) from (+)- or (—)-citronellol C271).177 It may also be used for the preparation of certain organo-metallic hydroperoxides. Thus, the triphenyl-tin derivative of tri-methylethylene (274) undergoes a photosensitized oxygenation reaction with a rate similar to that of tetramethylethylene, giving rise to the hydroperoxides 275 and 276 219... [Pg.89]

Dehydration products have been observed from photosensitized oxygenation reactions with cycloheptatriene (304),220 AMialin (307) 222 3/1- and 3a-hydroxy-A4-cholestenes (312a and 312b, respectively),226,227 and 2-hydroxy-10-methyl-1,9-octalin (316).226... [Pg.93]


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See also in sourсe #XX -- [ Pg.330 ]




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Oxygen photosensitization

Oxygenation reactions, photosensitized

Photosensitivity reactions

Photosensitized oxygenation

Reaction photosensitization

Reaction with oxygen

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