Dienes photooxidation

Heteropoly acid, tungstate-based, 496, 497 Hexacoordinate silyl peroxides, 808-10 , -Hexa-2,4-diene, photooxidation, 254-5 Hexamethyldisiloxane, oxidation, 806-7 Hexamethylene triperoxide diamine (HMTD) enthalpy of formation, 166 explosive, 707-8... 

Synthetic and Mechanistic aspects of 1,3-Diene Photooxidation" riennan. E.L. Tetrahedron. 1991, 47, 1343. 

The scope extends to certain aromatic compounds such as phenanthrene. Besides those dienes and aromatic rings that can be photooxidized directly, there is a larger group that give the reaction in the presence of a photosensitizer such as eosin (see... 

Drivers for Performing Photooxidation of Dienes in Micro Reactors... 

Beneficial Micro Reactor Properties for Photooxidation of Dienes... 

Photooxidation of Dienes Investigated in Micro Reactors Cas/liquid reaction 24 [CL 24] Oxidation of cyclopentadiene by singlet oxygen to 2-cyclopentene-1,4-diol... 

In a thorough study on photooxidation of 2,5-dimethyl-2,4-hexadiene (455) it was found that 1,2-dioxene 456, 1,2-dioxetane 457, hydroperoxy dienes 458 and 459 and, when methanol was used as solvent, also hydroperoxy(methoxy)octene 460 are formed (Scheme 124) . Product distribution was found to be highly solvent dependent. These results led investigators to postulate a mechanism involving the intermediacy of perepoxide 461 and zwitterion 462 (Scheme 124). Accordingly, the product of [4-1-21-cycloaddition 456, the product of [2 + 2]-cycloaddition 457, as well as the products 458 and 459 deriving from ene-addition would originate from polar intermediates 461 and... 

Photooxidation of Dienes (Addition of Oxygen, Oxygen) (2 + 4)0C,0C-cyc/o-Peroxy-1 /4/addition... 

The furan nucleus, being electron rich, is particularly sensitive to oxidation and most reactions involve 1,4-addition of the oxidant to the diene system. Photooxidation is discussed later (Section 3.11.2.7.2). 

Photolysis, in the presence of oxygen, of alkenes containing an ally lie hydrogen atom leads to the formation of hydroperoxides. The sensitized process is more efficient, and often yields photoproducts different in structure from those obtained by nonsensitized photooxidation. Cyclohexadiene and related dienes on photolysis in the presence of oxygen yield the transannular peroxides. Thus, on photosensitized oxidation, a-terpinene (410) is converted into ascaridole (411).435 The equivalent process is not, in general, observed in acyclic dienes. Certain polynuclear aromatic hydrocarbons, such as anthracene and naphthacene and including the heterocycles 5,10-diphenyl-1-... 

Tetradehydrodianthracene undergoes 4 + 2-cycloaddition with electron-deficient dienes such as 1,2,4,5-tetrazines.263 The Diels-Alder reactions of [3.3 ortho-anthracenophanes witli A-(p-nitro, chloro, or methoxy-substituted phenyl)malehnides yield approximately equal quantities of inside and outside adducts.264 The photooxidation of bulky water-soluble 1,4-disubstituted naphthalenes with singlet oxygen yields both the expected 1,4- and the unexpected 5,8-endoperoxides.265... 

Tebbe methylenation < 1978JA3611 > of a-bromoacetophenone resulted in the formation of allylic bromide 165, which upon reaction with benzenesulfonamide gave the 1,6-diene 166 (Scheme 35). The acyclic diene 166 underwent photooxidative cyclization to form 1,2,5-dioxazepine 167 <1996TL815>. 

H. A. J. Carless, J. R. Billinge, and O. Z. Oak, Photochemical routes from arenes to inositol intermediates the photooxidation of substituted cis-cyclohexa-3,5-diene-l,2-diols, Tetrahedron Lett. 1989, 30, 3113-3116. 

In 1989, the irradiation of (E,E)-2,4-hexadiene S3 sensitized by meso-porphyrin IX dimethyl ester led to the formation of cis-3,6-dimethyl-l,2-dioxene (62), which was the major product detected at — 78 °C in Freon 11 [69]. Endoperoxide 62 was purified under vacuum at 0.75 mmHg, and collected in a trap (98% isolated yield). Dienes that can adopt a cisoid conformation, such as 53 or ( , )-l,4-di phenyl butadiene, were photooxidized by the corresponding endoperoxides in high or quantitative yield in a suprafacial Diels-Alder reaction [60, 70], Dienes that cannot readily adopt cisoid conformations, such as (fc, Z)-2,4-hexadienes and (Z, Z)-2,4-hexadienes, lose their stereochemistry in the singlet oxygen [2 + 4]-cyclo-addition [60], (E,Z)- and (Z,Z)-dienes give a complex mixture of hydroperoxides and aldehydes, which suggests the intervention of intermediate zwitterions or 1,4-diradicals [71]. 

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