Radical ions in photochemistry. 3. Photosensitized (electron transfer) cleavage of .beta.-phenethyl ethers

Arnold, Donald R.; Maroulis, A. J.

doi:10.1021/ja00435a030

Cited by 120 publications

(73 citation statements)

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“…6~h e measured fluorescence lifetime ( T~) for DCN is 9.5 ns which is in agreement with the previously reported value 10.06 (19 For personal use only. fusion controlled rate constant of 1.8 X 10'' M-' s-' for CH3CN solutions at 20°C (19).…”

Section: Resultssupporting

confidence: 91%

“…No crossover product, namely 4-methyl-4'-methoxy-l,2-diphenylethane (Id), was detected by glc when an equimolar mixture of l a and l b in CH3CN (deoxygenated) containing DCN was irradiated. Conversely, the bibenzyls l a and l b were not detected as products upon irradiation of an authentic sample of I d under similar conditions, though the unsymmetrically substituted bibenzyl I d quenches the fluorescence of DCN by electron transfer at near diffusion-controlled rates in acetonitrile (19) …”

Section: Wavelength Nmmentioning

confidence: 90%

“…The diether 32 was irradiated in the presence of benzophenone (11) in acetonitrile under similar deoxygenated conditions and detectable isomerization was observed. It is unlikely, however, that 3DCN can transfer energy to 32 in view of the magnitude of its triplet energy (ET = 55.5 kcal/mol) (19). On the basis of the foregoing data it should be possible to design unsymmetrical reactive substrates which, like the substituted bibenzyl systems described above, would undergo facile fragmentation of the corresponding radical cations generated by photoinduced electron transfer reactions to give cations and free radicals.…”

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confidence: 99%

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Photoinduced electron transfer C—C bond cleavage reactions; oxidations and isomerizations

Reichel¹,

Griffin²,

Müller³

et al. 1984

Can. J. Chem.

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Section: Resultssupporting

confidence: 91%

Section: Wavelength Nmmentioning

confidence: 90%

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confidence: 99%

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Photoinduced electron transfer C—C bond cleavage reactions; oxidations and isomerizations

Reichel¹,

Griffin²,

Müller³

et al. 1984

Can. J. Chem.

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“…The diol (1.0 g) was then cyclized by refluxing for I h with an excess (2-3 mL) of hydrobromic acid (49%). The cooled reaction mixture was diluted with water and the organic layer was extracted with ether, washed with saturated sodium bicarbonate solution, dried over magnesium sulfate, and the solvent was evaporated to yield 80% of the ether (10). The product (10) was purified by chromatography on silica gel using hexanes and methylene chloride as eluants.…”

Section: 3-diphenyltetrahydrofuran (10)mentioning

confidence: 99%

“…We have studied the photosensitized (electron transfer) reactions of [8][9][10][11] (and 15) under conditions identical with those used previously in reactions [ l ] and [2]. are cyclic analogs of 1 and 2.…”

Section: Introductionmentioning

confidence: 99%

1,n-Radical ions. The photosensitized (electron transfer) formation of 1,5-radical cations

Arnold¹,

Fahie²,

Lamont³

et al. 1987

Can. J. Chem.

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. Can. J. Chem. 65, 2734Chem. 65, (1987.The photosensitized (electron transfer) reactions of 3-phenyl-2.3-dihydrobenzofuran @a), 5-methyl-3-phenyl-2,3-dihydrobenzofuran (8b), cis and trans-2-methoxy-1-phenylindane (9, cis and trans), 3,3-diphenyltetrahydrofuran (lo), and 22-diphenyl-1-methoxycyclopentane (11) have been studied using 1,4-dicyanobenzene as an electron-accepting photosensitizer and acetonitrile-methanol (3: 1) as solvent. These reaction conditions cause carbon-carbon bond cleavage of analogous acyclic P,P-diphenylethyl ethers to give products derived from the diphenylmethyl radical and the a-oxycarbocation intermediates. The purpose of this study was to determine if this reaction could be applied to five-membered cyclic derivatives to give 1,5-radical cations.The primary products from 8 a and 8b were the dehydrogenated, aromatized 3-phenylbenzofurans 140 and 14b. These products react further; continued irradiation gave the methanol adducts, cis and tmns-2-methoxy-3-phenyl-2,3-dihydrobenzofuran (15a and 15b, cis and trans). The only observed reaction of the indanes (9, cis and trans) was cis-trans isomerization. Deuterium was incorporated at the bis-benzylic position of 8 and 9 when the irradiation was carried out in acetonitrilemethanol-0-d. These results are consistent with reversible deprotonation from the radical cations. 'There was no evidence for carbon-carbon bond cleavage with either 8 or 9. The relative rate, deprotonation faster than carbon-carbon bond cleavage, is explained in terms of the conformation of the bond that cleaves in relation to the singly occupied molecular orbital (SOMO) of the radical cation. Oxidation potential measurements support the conclusion that the SOMO of 8 and 9 is largely associated with the fused phenyl ring and is therefore orthogonal to the benzylic carbon-carbon bond. Irradiation of cis or trans-2-methoxy-3-phenyl-2,3-dihydrobenzofuran (15a, cis or trans), under these conditions, leads to cis-trans isomerization. The mechanism in this case involves the reversible loss of methanol. There is evidence that the addition of methanol to 14 involves the sensitizer radical anion -14 radical cation pair.In contrast with the fused bicyclic systems, the monocyclic tetrahydrofuran 10 and the methoxycyclopentane 11 both cleave under these conditions; the products are the expected acetals 22 and 29 formed from the intermediate 1,5-radical cations. In 10 and 11 the SOMO, which is largely associated with the diphenylmethyl moiety, can overlap with the adjacent carbon-carbon bond and cleavage occurs as in analogous acyclic systems. Both 10 and 11 are relatively stable to irradiation under conditions that are identical except with acetonitrile as solvent (without methanol). We found no evidence for cyclization of the intermediates (1,hadical cation or 1,5-diradical) into the terminal phenyl ring. DONALD R. ARNOLD, BRIAN J. FAHIE, LAURIE J. LAMONT, JACEK WIERZCHOWSKI et KENT M. YOUNG. Can. J. Chem. 65, 2734Chem. 65, (1987.Utilisant le dicyano-1,4 benzkne comme photosen...

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Triphenylpyrylium Tetrafluoroborate-Sensitized Photochemistry of the Terpenes Sabinene, α-Phellandrene, and α- and γ-Terpinene

Climent

Miranda²,

Roth³

2000

Eur. J. Org. Chem.

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The triphenypyrylium tetrafluoroborate (TPT)‐sensitized reactions of several terpene donor molecules, including sabinene (1), α‐phellandrene (4), α‐terpinene (5) and γ‐terpinene (6) give rise to significantly different products than reactions induced by other electron‐transfer sensitizers, such as 1,4‐dicyanobenzene (DCB). The divergent reactions require decidedly different key intermediates; the products obtained with TPT can be explained by dissociative recombination of the intermediate radical‐radical cation pair in the triplet state, generating donor‐derived biradicals.

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Radical ions in photochemistry. 3. Photosensitized (electron transfer) cleavage of .beta.-phenethyl ethers

Cited by 120 publications

References 1 publication

Photoinduced electron transfer C—C bond cleavage reactions; oxidations and isomerizations

Photoinduced electron transfer C—C bond cleavage reactions; oxidations and isomerizations

1,n-Radical ions. The photosensitized (electron transfer) formation of 1,5-radical cations

Triphenylpyrylium Tetrafluoroborate-Sensitized Photochemistry of the Terpenes Sabinene, α-Phellandrene, and α- and γ-Terpinene

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