Salt Effect on the 9,10-Dicyanoanthracene-Sensitized Photooxygenation of 1,2-Diarylcyclopropanes and the Photodecomposition of 3,5-Diaryl-1,2-dioxolanes

Article abstract of DOI:10.1021/jo00046a014

The 9,10-dicyanoanthracene (DCA)-sensitized photooxygenation of less electron-rich 1,2-diarylcyclopropanes 1 such as 1,2-diphenylcyclopropanes and 1,2-bis(4-chlorophenyl)cyclopropanes in the presence of Mg(ClO4)2 gave cis- and trans-3,5-diaryl-1,2-dioxolanes as major products.However, in the absence of Mg(ClO4)2, the photooxygenation did not afford 1,2-dioxolanes, but their decomposition products, 1,3-diaryl-1-hydroxypropan-3-ones 5, aryl aldehydes 6, and aryl methyl ketones 7.The DCA-sensitized photodecomposition of 1,2-dioxolanes also gave 5-7.This photoreaction was suppressed by addition of Mg(ClO4)2.The DCA-sensitized photooxygenation of 1 proceeds via radical cations that are generated by photoinduced electron-transfer from 1 to the excited singlet ¹DCA^*.The DCA-sensitized photodecomposition of 1,2-dioxolanes occurs via exciplexes that are formed between 1,2-dioxolanes and ¹DCA^* or energy-transfer from the excited triplet ³DCA^* to 1,2-dioxolanes.