The photoreduction of aromatic systems

Barltrop, J. A.

doi:10.1351/pac197333020179

Cited by 69 publications

(32 citation statements)

References 33 publications

(4 reference statements)

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“…16 except that the nucleophile is now cyanide ion, formed as a consequence of the photosubstitution reaction. Finally, it is noteworthy that while considerable amounts of 9-cyanophenanthrene (28) and 9-cyano-9,lO-dihydrophenanthrene (29) were isolated from the phenanthrene-photosensitized reactions in acetonitrile solution, no trace of 9-methoxyphenanthrene or the 9-methoxydihydro derivative could be detected in the ~ ~ present system. Apparently the radical cation of phenanthrene (11) is not as susceptible to nucleophilic attack by methanol as by cyanide.…”

Section: Irradiation In Acetonitrile-methanolmentioning

confidence: 77%

Radical ions in photochemistry. 15. The photosubstitution reaction between dicyanobenzenes and alkyl olefins

Borg¹,

Arnold²,

Cameron³

1984

Can. J. Chem.

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Can. J. Chem. 62, (785 (1984). ' The photosubstitution (electron transfer) reaction between 1,4-dicyanobenzene (1) and 2,3-dimethyl-2-butene (2), which gives I-(4-cyanophenyl)-2,3-dimethyl-2-butene (3) and 3-(4-cyanopheny1)-2,3-dimcthyl-I-butene (4). has been extended to other dicyanobenzene-olefin mixtures. Substitution of a cyano group occurs when both 1 or 1,2-dicyanobenzene (5) are irradiated in acetonitrile solution, in the presence of 2 or cyclohexcne (16). Under comparable conditions, 1.3-dicyanobenzene (6) failed to react. Little or no substitut~on was observed in any case when the olefin was methylpropene (19). ' The results for 1 and 5 are in agreement with empirical free energy calculations (Weller equation) for the electron transfer process which, however, fail to explain the general lack of reactivity of 1,3-dicyanobenzene. Phenanthrene (11) has been shown to photosensitize the photosubstitution reaction between dicyanobenzenes and 2. Under these conditions the olefin reacts with 6 predominantly at the 4-position, resulting in overall substitution of a hydrogen atom. This reaction occurs regiospecifically, resulting in the formation of only one of the two possible isomeric side chains. The mechanistic details of these reactions have been substantiated by means of deuterium labelling studies. The aromatic nitriles also undergo photosubstitution by 2, in acetonitrile-methanol solution, resulting in methanol-incorporated products. Whereas reaction with 1 or 5 results in substitution of a cyano group, 6 was observed to give isomeric dicyanocyclohexenes, resulting from initial reaction at the 4-position, followed by reduction. A detailed mechanism for this secondary photoreduction has been substantiated by deuterium labelling studies. The anomalous behaviour of 1,3-dicyanobenzene has been attributed to a difference in the react~vity of the radical anion. marquages par le deutCrium permettent de confirmer les dttails mkcanistiques dc ces rCactions. Les nitriles aromatiques, en solution dans des milanges d'acktonitrile et de methanol, subissent aussi des photosubstitutions par 2; il y a formation de produits ayant incorporC du mCthanol. Alors que la rCaction des composCs 1 ou 5 conduit a la substitution d'un groupe cyano, on a observC que le compost 6 donne des dicyanocyclohextnes isomkres qui resultent d'une rkaction initiale en position 4, suivie d'une riduction. Des Ctudes impliquant des marquages par du deuterium ont permis de confirmer le mCcanisme dCtaillC de cette photorCduction secondaire. On attribue Ie comportement anormal du dicyano-I ,3 benzkne a la diffkrence de rCactivitC de I'anion radical.[Traduit par le journal]

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Section: Irradiation In Acetonitrile-methanolmentioning

confidence: 77%

Radical ions in photochemistry. 15. The photosubstitution reaction between dicyanobenzenes and alkyl olefins

Borg¹,

Arnold²,

Cameron³

1984

Can. J. Chem.

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“…cules and aliphatic amines the reaction involves electron The half-life of azadirachtin was¯48 min, yielding an transfer [188]. isomerised (Z)-2-methylbut-2-enoate product.…”

Section: Photodegradation Of Napropamide H(rs)-nn-diethyl-2-(1-mentioning

confidence: 99%

Reaction pathways and mechanisms of photodegradation of pesticides

Burrows

Santaballa

Steenken

2002

Journal of Photochemistry and Photobiology B: Biology

568

286

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The photodegradation of pesticides is reviewed, with particular reference to the studies that describe the mechanisms of the processes involved, the nature of reactive intermediates and final products. Potential use of photochemical processes in advanced oxidation methods for water treatment is also discussed. Processes considered include direct photolysis leading to homolysis or heterolysis of the pesticide, photosensitized photodegradation by singlet oxygen and a variety of metal complexes, photolysis in heterogeneous media and degradation by reaction with intermediates generated by photolytic or radiolytic means.

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“…generated by PET processes from amineϪarene pairs, are known to undergo H ϩ transfer from the α-CϪH bond to the geminate ion radical within the solvent cage, resulting in an amineϪarene adduct through coupling of the resultant radical species. [12] However, we [13] as well as others [14] have reported that PET reactions between a tert-amine and certain potent electron acceptors in polar solvents lead to a sequential two-electron oxidation [electron-proton-electron (E-P-E) sequence] of the amine, leading to iminium cation intermediates. Based on these premises, we have developed a photosystem utilizing 1,4-dicyanonaphthalene (DCN) as a light-harvesting electron-acceptor and methyl viologen dication (MV ϩϩ ) as an electron-transfer mediator, as shown in Figure 1, for the in situ generation of iminium cation intermediates from tert-amines for synthetic purposes.…”

Section: Introductionmentioning

confidence: 94%

“…Nucleophilic alkylation of 3 and 4, using Grignard reagents and allyltrimethylsilane/TiCl4, provides 12a؊d & 15 and 17a؊ c & 21, respectively, in a highly stereoselective manner. Hydrolysis of the resultant amides (12,15,17, and 21) provides α-amino acid derivatives (14) and α-hydroxy acids, respectively, in optically active form, along with the recovered (S)-prolinol chiral auxiliary in its recyclable form. generated by PET processes from amineϪarene pairs, are known to undergo H ϩ transfer from the α-CϪH bond to the geminate ion radical within the solvent cage, resulting in an amineϪarene adduct through coupling of the resultant radical species.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Electron Transfer (PET) Promoted Oxidative Activation of 1-(N-Benzyl-N-methylglycyl)-(S)-prolinol: Development of Novel Strategies Towards Enantioselective Syntheses of α-Amino Acids, TheirN-Methyl Derivatives and α-Hydroxy Acids Employing (S)-Prolinol as aRecyclable Chiral Auxiliary

2000

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PET activation of 1‐(N‐benzyl‐N‐methylglycyl)‐(S)‐prolinol (1) in dry acetonitrile, utilizing 1,4‐dicyanonaphthalene (DCN) as a light‐harvesting electron‐acceptor and methyl viologen (MV++) as an electron‐transfer mediator, leads to the formation of 3‐[benzyl(methyl)amino]perhydropyrrolo[2,1‐c][1,4]oxazin‐4‐one (3). When this photolysis is carried out in aqueous acetonitrile, exclusively 3‐hydroxyperhydropyrrolo[2,1‐c][1,4]oxazin‐4‐one (4) is produced. The formation of 3 can be rationalized in terms of intramolecular cyclization of the in situ generated iminium cation intermediate (2) by the OH moiety of (S)‐prolinol, while 4 is generated by hydrolysis of 2 followed by acetalization. Nucleophilic alkylation of 3 and 4, using Grignard reagents and allyltrimethylsilane/TiCl4, provides 12a‐d & 15 and 17a‐c & 21, respectively, in a highly stereoselective manner. Hydrolysis of the resultant amides (12, 15, 17, and 21) provides α‐amino acid derivatives (14) and α‐hydroxy acids, respectively, in optically active form, along with the recovered (S)‐prolinol chiral auxiliary in its recyclable form.

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The photoreduction of aromatic systems

Cited by 69 publications

References 33 publications

Radical ions in photochemistry. 15. The photosubstitution reaction between dicyanobenzenes and alkyl olefins

Radical ions in photochemistry. 15. The photosubstitution reaction between dicyanobenzenes and alkyl olefins

Reaction pathways and mechanisms of photodegradation of pesticides

Photoinduced Electron Transfer (PET) Promoted Oxidative Activation of 1-(N-Benzyl-N-methylglycyl)-(S)-prolinol: Development of Novel Strategies Towards Enantioselective Syntheses of α-Amino Acids, TheirN-Methyl Derivatives and α-Hydroxy Acids Employing (S)-Prolinol as aRecyclable Chiral Auxiliary

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