Formation of an ozonide by electron-transfer photooxygenation of tetraphenyloxirane. Cosensitization by 9,10-dicyanoanthracene and biphenyl

Dual Catalysis Strategies in Photochemical Synthesis

“…71 In the 1980s, the Schaap group discovered that biphenyl provided a dramatic rate increase to the DCA-catalyzed oxidation of cyclopropanes, 72 epoxides, 73–76 and aziridines. 77 For example, the photooxygenation of epoxide 19 to 20 is a slow reaction upon photocatalysis using DCA alone (Scheme 2).…”

Photoinduced electron transfer reactions of 2,4,6-triphenylpyrylium: solvent effect and charge-shift type of systems

“…The formation of radical pairs in the photoinduced electron transfer reaction is a subject of immeasurable signiÐcance due to its ubiquity in polymerisation,10 organic synthesis11 and cosensitisation. 12 The e †ect of solvent on the bell shaped energy gap dependence observed for the recombination of radical pairs has already been well established. The e †ect of driving force and molecular dimension,13a molecular charge,13b isotopic substitution,13c separation distance,13d stoichiometry,13e external pressure13f and steric e †ect on the radical yield13f,g have been studied.…”

Addition and cycloaddition reactions via photoinduced electron transfer

“…Redox photosensitization or co-sensitization by aromatic hydrocarbons has been utilized for enhancement of the efficiency of photoinduced electron transfer reactions. For example, the efficiency of the 9,10-dicyanoanthracene-sensitized photooxygenation of 1,2-diphenyloxirane in acetonitrile is enhanced appreciably by adding biphenyl as a co-sensitizer, giving 3,5-diphenyl-l,2,4-trioxolane in good yield [31][32]. This photoreaction does not take place in the absence of biphenyl.…”