FORMATION OF 1,2-DIOXANES BY ELECTRON-TRANSFER PHOTOOXYGENATION OF 1,1-DISUBSTITUTED ETHYLENES

Article abstract of DOI:10.1016/S0040-4039(01)81277-6

Electron-rich 1,1-diarylethylenes (1a-e) afford 3,3,6,6-tetraaryl-1,2-dioxanes (3a-e) in high yields (>90percent) when subjected to electrontransfer photooxygenation in the presence of DCA.Whereas 1,1-diphenylethylene (1f) and 1,1-di(p-chlorophenyl)ethylene (1h) yield the 1,2-dioxanes 3f and 3h at 30percent and less than 10percent, respectively, there is negligible (if any) 1,2-dioxane formation with 1,1-di(m-anisyl)ethylene (1i). 1,2-Dioxane formation proceeds in a chain reaction (Scheme 1).N-Vinylcarbazol (1g), however, yields the 1,2-dioxane 3g via the cyclobutane derivative 7 (Scheme 2).