Synthesis of 3,3,6,6-Tetraaryl-1,2-Dioxanes via TiO2-catalyzed Photooxygenation of 1,1-Diarylethenes in the Presence of Mg(ClO4)2

Photooxygenation of methoxy-substituted 1,1-diarylethenes and 1,1,8,8-tetraaryl-1,7-octadienes catalyzed by titanium dioxide proceeded via photoinduced electron transfer to give 3,3,6,6-tetraaryl-1,2-dioxanes in high yields. The photooxygenation was remarkably accelerated by the addition of Mg(ClO4)2.