Photoinduced single electron transfer

Photoinduced single-electron transfer followed by fragmentation of the radical cation is an efficient method for generating carbon-centered radicals under exceptionally mild conditions. The fate of the thus formed radicals depends primarily on their interaction with the acceptor radical anions. Typically observed reactions are either back-electron transfer or radical coupling, but from the synthetic point of view, another most intriguing possibility is the trapping of the radical with suitable substrates such as olefins (Scheme 16). 

Photoinduced single-electron transfer Proton transfer... 

Barvian MR, Barkley RM, Greenberg MM (1996) Reactivity of 5,6-dihydro-5-hydroxythymid-6-yl generated via photoinduced single electron transfer and the role of cyclohexa-1,4-diene in the photodeoxygenation process. J Am Chem Soc 117 4894-4904 Becker D, Sevilla MD (1997) Radiation damage to DNA and related biomolecules. Electron Spin Re-son 16 79-115... 

Phthalimides. Like their aromatic ketone counterparts, TV-alkyl phthalimides participate in hydrogen atom abstraction reactions to form a large variety of heterocyclic compounds. However, despite many similarities between phthalimides and aromatic ketones, there are some important differences. In contrast to aromatic ketones, electronically excited phthalimides are not transformed quantitatively into the triplet state, and thus they may react from both the singlet and the triplet state. In addition, phtalimides are much more inclined to photoinduced single-electron-transfer (PET) reactions [24,25]. (For details see Sec. 3.3.2.1.)... 

A novel procedure for the oxidative removal of benzyl protecting groups by catalytic homogeneous electron transfer has been developed by Schmidt and Steckhan (equation 34)." The selectivity of the reaction can be adjusted by altering the substitution on the aromatic rings of the cation radicals (48). Finally, a recent publication describes a photoinduced single electron transfer initiated oxidative cleavage of benzylic ethers. ... 

Compound 639 also promotes the photo induced reduction of ketones whereas 2-(2 -hydroxyphenyl)-l,3-dimethyl-benzimidazoline 640 promotes benzpinacol formation (Scheme 153) <2005JOC9632>. Photoinduced single electron transfer (SET) followed by regiospecific proton transfer (PT) led to the formation of either benzhydrol or benzpinacol, depending on the 2-aryl substituent. 

Various photoreactions arising by carbon-oxygen bond cleavage have been reported. Photoinduced single electron transfer-initiated cleavage of the benzylic ether protecting... 

Topics reviewed during the year include the photochemistry of indoles, sulfoxides, pyrazoles and isothiazoles, (S-hetero)cyclic unsaturated carbonyl compounds, photoinduced single electron transfer (SET) reactions of amines and of azo compounds, SET reactions of organosilanes and organostannanes with Qo and ketones, photochromic polypeptides and di(hetero)arylethenes, processes in chromophore sequences on a-helical polypeptides,aryl-aryl coupling in furans, thiophenes and pyrroles," [3+2]cycloaddition of aromatic nitriles (and esters) with alkenes, and reactions of benzylsilane derivatives. ... 

Kamata, M., Kato, Y., and Hasegawa, E., Photoinduced single electron transfer reactions of 1,3-dithianes and 1,3-dithiolanes sensitized by triphenylpyrylium salt in the presence of molecular oxygen. Tetrahedron Lett., 32, 4349,1991. 

Hasegawa, E., Ishiyama, K., Horaguchi, T., and Shimizu, T., Exploratory study on photoinduced single electron transfer reactions of a,P-epoxy ketones with amines, /. Org. Chem., 56,1631, 1991. Hasegawa, E., Ishiyama, K., Horaguchi, T., and Shimizu, T., Free radical trapping of a-keto radicals derived from a,P-epoxy ketones via photoinduced single electron transfer process. Tetrahedron... 

Cossy, J., Bouzide, A., Ibhi.S., and Aclinou, R, Formation of P-hydroxyketones from a,P-epoxy ketones by photoinduced single electron transfer reactions. Tetrahedron, 47, 7775,1991. 

Buscemi, S., Pace, A., Vivona, N., Caronna, T., and GaHa, A., Photoinduced single electron transfer on 5-aryl-1,2,4-oxadiazoles some mechanistic investigations in the synthesis of quanazolin-4-ones, /. Org. Chem., 64, 7028, 1999. 

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