Electron-transfer-induced photochemical reactions of (silylallyl)iminium and benzylpyrrolinium salts by dual diradical and diradical cation cyclization pathways

1990 ◽  
Vol 112 (9) ◽  
pp. 3594-3607 ◽  
Author(s):  
In Seop Cho ◽  
Chung Lan Tu ◽  
Patrick S. Mariano
Keyword(s):  
Electron Transfer ◽  
Photochemical Reactions

Article

1999 ◽  
Vol 77 (10) ◽  
pp. 1655-1670 ◽  
Author(s):  
Dino Mangion ◽  
Donald R Arnold
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Photochemical Reactions ◽  
Transfer Mechanism ◽  
Radical Ions ◽  
Reaction Conditions ◽  
Electron Transfer Mechanism ◽  
Photochemical Reactivity ◽  
Bond Homolysis

The photochemical reactivity of a series of 4-halobenzonitriles and 4-haloanisoles with 1,1-diphenylethene in a nucleophilic solvent (methanol) has been investigated. Analysis of the photochemical reactions involving the 4-halobenzonitriles revealed formation of alkene-methanol adducts, such as 1-methoxy-2,2-diphenylethane, 1-methoxy-2,2-diphenylethene, and 1,1-dimethoxy-2,2-diphenylethane, indicative of a photochemical electron-transfer mechanism. These products were not significant in the photochemical reactions involving the 4-haloanisoles. Both the 4-halobenzonitriles and the 4-haloanisoles produced an arene-alkene-methanol Markovnikov adduct, 1-aryl-2-methoxy-2,2-diphenylethane (aryl = 4-cyanophenyl or 4-methoxyphenyl). This compound was shown to undergo an acid-catalysed elimination to 1-aryl-2,2-diphenylethene under the reaction conditions, which subsequently underwent a 6pi-electrocyclization to the 3-substituted(cyano or methoxy)-9-phenylphenanthrene. Possible mechanisms for the observed reactivity are discussed and evaluated.Key words: photochemistry, photoinduced electron transfer, bond homolysis, radical ions, radicals, exciplexes.

Kinetics of the photochemical reactions of the croconate dianion in aqueous solution

1992 ◽  
Vol 70 (1) ◽  
pp. 135-143 ◽  
Author(s):  
B Zhao ◽  
M. H. Back
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Quantum Yield ◽  
Rate Constants ◽  
Photochemical Reactions ◽  
Electron Acceptors ◽  
Basic Solution ◽  
Hydroxyl Ion ◽  
Kinetics Of

The kinetics of the photochemical reactions of the dianion of croconic acid (1,2-dihydroxycyclopentenetrione) have been studied in aqueous solution in the presence of electron acceptors. In neutral solutions the quantum yield for disappearance of croconate dianion was small (< 10−3) but was substantially increased in basic solution and in the presence of electron acceptors. At pH 12 in the presence of 4-nitrobenzylbromide and biacetyl a quantum yield of 1 was obtained. The kinetics of the rate of disappearance of croconate dianion as a function of pH and concentration of acceptor showed that the excited dianion is oxidized by acceptors and reacts with hydroxyl ion. A mechanism is proposed that, by assuming reasonable values for the rate constants involved, is shown to be consistent with the results. Keywords: photolysis, kinetics, croconate dianion, electron transfer.

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