Electron-transfer photooxygenation

Conventional singlet oxygen sensitizers such as Thiazine dyes, 2 and 3, have been reported to promote Wagnerova Class II electron-transfer photooxygenations.60 For example, the participation of singlet oxygen in the reaction depicted in Fig. 9... 

Following a mechanism similar to that described in Scheme 29, electron transfer photooxygenation of 1-tert-bntylcyclohexa-l,3-diene (145) in the presence of Tr BF4 leads, throngh the intermediacy of cation radicals 146,149 and 150, to the dimeric fused tricyclic peroxides 151 (total 40% yield, cisitrans ca 5 4) rather than to the monomeric bridged bicyclic peroxide 148 (5-10%) which derives from cation radical 147 (Scheme 36) ... 

Independently and concomitantly, similar conclusions on the electron-transfer photooxygenations of several substituted 1,2-diarylcyclopropanes, 79a-d, affording the corresponding 1,2-dioxolanes, 80a-d, in high yields as well as high... 

The cyanoaromatic-sensitized electron-transfer photooxygenation (Foote-type) is a useful preparative reaction with a very limited class of unsaturated olefins, namely those substituted by aromatics and, at the same time, totally inert towards singlet oxygen. On the other hand, in the previous sections, it has been many times underlined that electron-transfer reactions may compete with singlet oxygen formation and, above all, that the reactions of 02 may be the only observable outcome in the presence of singlet-oxygen acceptors. 

Aryl-substituted oxiranes are converted to ozonides by co-sensitized electron transfer photooxygenation with 9,10-dicyanoanthracene (DCA) and biphenyl <82CC1223,83JA663,83JA5149,83JCS596, 84JCS(P1)15>. 

Ando and co-workers reported that electron transfer photooxygenation of three- and four membered cyclic disilanes gives cyclic perox-ides. DCA-sensitized photooxygenation of 1,2-disiletenes affords cyclic peroxides, 1,2,3,6-dioxadisilins, and 1,2,5-oxadisilole-nes. Similar photooxygenation of oxadisiliranes gives 1,2,4,3,5- tri-oxadisilolanes. For these photoreactions, Si-Si bond cleavage in the radical cations of the cyclic disilanes is postulated to be the key process. 

Schaap, A.P., Siddiqui, S., Prasad, G., Rahman, A.F.M.N., and Oliver, J.P., Stereoselective formation of ds-ozonides by electron transfer photooxygenation of naphthyl-substituted epoxides. Stereochemical assignment of ozonides by x-ray crystallography and chromatographic resolution,/. Am. Chem. Soc., 106, 6087, 1984. 

Futamura, S., Chemical behavior of aromatic radical cations under superoxide-free electron transfer photooxygenation conditions. Bull. Chem. Soc. Jpn., 65,1779,1992. 

Tsuchiya, M., Ebbesen, T. W., Nishimura, Y, Sakuragi, H., and Tokumaru, K., Kinetic studies on electron transfer photooxygenation of aromatic olefins. Quenching rate of olefin radical cation by oxygen and superoxide anion, Chem. Lett., 2121,1987. 

Algarra, F., Baldovi, M. V., Garcia, H., Miranda, M. A., and Primo, J., Direct photolysis and electron transfer photooxygenation of enol acetates of 3-phenylpropiophenones, Mowatsh. Chem., 124,209, 1993. 

Lopez, L., Troisi, L., Rashid, S. M. K., and Schaap, A. R, Synthesis of 1,2-dioxetanes via 9,10-dicyanoanthracene sensitized chain electron-transfer photooxygenations. Tetrahedron Lett., 30, 485, 1989. 

Gollnick, K. and Schnatterer, A., Formation of a 1,2-dioxane by electron-transfer photooxygenation of l,l-di-(p-anisyl) ethylene. Tetrahedron Lett., 185,1984. 

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