Photoreactions of o-quinones with olefins: competition between cyclo- and R–H-addition

Farid, Samir; Scholz, K.-H.

doi:10.1039/c19680000412

Cited by 9 publications

(4 citation statements)

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“…The absorbance charges are similar to those observed for the photoreaction of PhQ and 2-hexene and are due to the formation of cycloadducts between the excited PhQ and the double bonds of the egg PC. The efficiency of the reaction is given in Table 2 and is similar to that reported for the photoreaction of PhQ with 2-butene (Farid and Scholz, 1968). The quantum yield of -0.25…”

Section: Resultssupporting

confidence: 78%

“…These bands are believed to be due to cycloaddition products and indicate that the major products are cycloaddition when the PhQ is photolyzed in 2-hexene. These data are consistent with the observations ofFarid and Scholz (1968) on the products of photolysis of PhQ in butenes.Phospholipid vesicles were prepared from saturated and/or unsaturated phosphatidylcholines. The saturated PC used was DMPC.…”

supporting

confidence: 92%

“…Photoexcited PhQ adds to olefins to yield 1.4and/or 1.2-cycloadducts as well as R-H additions (Scheme 1). Farid and Scholz (1968) demonstrated that the photoproducts of PhQ and butenes were 85590% cycloadducts. The quantum yield for PhQ disappearance in the cis-2-butene was 0.36.…”

Section: Introductionmentioning

confidence: 99%

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Photolysis of Phenanthrenequinone in Phospholipid Vesicles

Lopez

O’Brien

2008

Photochemistry and Photobiology

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Phospholipid vesicles of saturated and unsaturated phosphatidylcholines have been prepared with phenanthrenequinone incorporated into the hydrocarbon region of the lipid bilayer. Blue or ultraviolet light exposure of these vesicles causes a loss of quinone absorbance and the corresponding formation of new absorbance bands due to addition products. In vesicles composed of unsaturated phospholipids, cycloaddition is preferred over R--H addition. The quant urn yield for quinone disappearance is -0.25 in vesicles which contain unsaturated phospholipids and decreases to 0.08 when the photolysis is conducted below the lipid characteristic temperature.

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Section: Resultssupporting

confidence: 78%

supporting

confidence: 92%

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Photolysis of Phenanthrenequinone in Phospholipid Vesicles

Lopez

O’Brien

2008

Photochemistry and Photobiology

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“…When hydrogen abstraction competes with the cycloaddition mechanisms, the hydrogen abstraction product yield increases as a function of the presence of large substituents in the olefin (as for example the neopentyl group as in 2,4,4-trimethyl-1-pentene) or when the reaction is done in the presence of a highly strained cyclic olefin. [23][24][25][26][27][28] Even so, the increase in the yield of hydrogen abstraction products parallels the quenching rate constants, indicating that steric effects reduce the biradical formation and/or cyclization controlling the product distribution. However, previous studies on the reaction of cyclic vicinal tricarbonyl compounds with olefins show that electronic effects predominate over steric effects in the quenching process, with photocycloaddition products only starting to be formed when the ionization potential of the olefin approaches 8.7 eV.…”

Section: Resultsmentioning

confidence: 99%

Laser flash photolysis study of the reaction of 1H-benz[f]indane-1,2,3-trione with olefins

Silva¹,

Netto‐Ferreira²

2004

J. Braz. Chem. Soc.

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A fotoquímica de 1H-benz[f]indano-1,2,3-triona (1) em presença de olefinas, em solução de benzeno e a temperatura ambiente, foi examinada empregando a técnica de fotólise por pulso de laser. O estado excitado triplete de 1 ( = 3 s, = 460 e 490 nm, em benzeno) é suprimido por olefinas contendo hidrogênio alílico com constantes de velocidade variando de 10 5 L mol -1 s -1 (para 1,5-hexadieno) a 10 9 L mol -1 s -1 (para 2,5-dimethyl-2,4-hexadieno). A comparação entre a reatividade de 1 com a de 1,2,3-indanotriona (2) mostra que um mesmo mecanismo de supressão está operando nos dois casos, o qual envolve, essencialmente, o estado excitado triplete de energia mais baixa da tricetona vicinal cíclica com característica n, *. (2) shows that a similar mechanism for the quenching by olefins is operating for the two cyclic vicinal triketones and involves essentially the lowest triplet excited state of n, * character.

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Photochemical cycloaddition of o‐quinones to allenes; 2‐alkylidene‐2,3‐dihydro‐1,4‐dioxins

Bos¹,

Slagt²,

Boleij³

1970

Recl. Trav. Chim. Pays‐Bas

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Phenanthroquinone was added photochemically to allene and nine of its methyl, methoxy and methylthio derivatives. Several 2-alkylidene-2,3-dihydrophenanthro[9,10-b]-1,4-dioxins were isolated; 2 : I-adducts were sometimes found as byproducts. The directiospecificity of the addition was investigated. The stereochemistry and conformation of the adducts are discussed in relation to long-range N M R coupling constants. Tetrachloro-o-benzoquinone was added similarly to methoxyallene. This addition could also be performed thermally.

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Photoreactions of o-quinones with olefins: competition between cyclo- and R–H-addition

Cited by 9 publications

References 0 publications

Photolysis of Phenanthrenequinone in Phospholipid Vesicles

Photolysis of Phenanthrenequinone in Phospholipid Vesicles

Laser flash photolysis study of the reaction of 1H-benz[f]indane-1,2,3-trione with olefins

Photochemical cycloaddition of o‐quinones to allenes; 2‐alkylidene‐2,3‐dihydro‐1,4‐dioxins

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